On the morning of 1 December 2017, an M-18A Dromader aircraft (Pratt & Whitney PT6A engine), registered VH-WHR (WHR) prepared for an aerial agricultural spraying operation at a private airstrip, 9 km north of Emerald Airport, Queensland. The aircraft was operated by Central Highlands Aerial Services and was conducting a spray operation on an 81-hectare paddock (Figure 1, shown in green), about 6 km west‑south‑west of the airstrip.
Figure 1: Application area (green), accident site (blue) and track flown (yellow)
Source: Google earth, annotated by the ATSB
The pilot conducted a pre-flight inspection of WHR and found everything to be serviceable. He was also the last person to fly the aircraft, three days prior to the accident, and had not identified any problems.
The wind was reported to be 4‑6 kt from the northeast. The spraying operation was standard with no major hazards in or around the paddock ‑ the pilot had sprayed the paddock several times in the past conducting the same spray pattern flying east and west.
At about 0604 Eastern Standard Time,[1] the aircraft arrived at the paddock and the pilot conducted several short spray runs in the south-western corner to ensure there was no overspray onto an adjoining paddock. He then conducted several back-to-back spray runs in the same corner (Figure 1) and at about 0614, he commenced a racetrack pattern over the remainder of the paddock.
At about 0620, a witness located about 1 km from the paddock observed the aircraft complete the ninth racetrack pattern run and commence a turn to the right to line up for the next run. The witness estimated that about three quarters of the way through the turn, while lining up for the next run, the aircraft rapidly pitched down and the right wing collided with the ground. The aircraft subsequently flipped, and came to rest inverted and facing in the opposite direction to the flight path about 20‑30 m from the initial contact point (Figure 2).
Figure 2: Accident site
Source: Police
At about 0622, the witness called emergency services and proceeded to the accident site. When the witness arrived at the wreckage, he found the pilot had exited the aircraft through the broken cockpit side window.
Ambulance officers treated the pilot before transporting him to hospital. He was admitted to treat his injuries, which included a fractured left leg, three fractured left ribs, bruises, cuts to his left side, and concussion. The pilot was wearing a helmet at the time of the accident and it was damaged from impact with the aircraft structure (Figure 3). The pilot had no recollection of the accident and no mechanical issue was identified that may have contributed to the accident.
Figure 3: Damage to the left side of the pilot’s flight helmet
Source: Police
While the track of the aircraft during the spray operation was recorded, other parameters such as airspeed, time, altitude, and aircraft attitude were not. Figure 4 shows the final four racetrack pattern turns back towards the west. The last inbound turn (shown in blue) was conducted at a smaller turn radius than the previous three turns in that direction. The track data finished about 460 m from the accident site.
Figure 4: Final four right turns from an easterly track (last shown in blue)
Source: Google earth, annotated by the ATSB
The pilot joined the operator in January 2015, gaining about 800-flight hours in WHR (with the installed PT6A engine) and flew the previous flight in WHR three days prior to the accident. He did not report any concerns with the aircraft.
The maintenance release for WHR was issued about 40 flight hours prior to the accident and no outstanding maintenance or defects were recorded.
Safety analysis
About three quarters of the way through a turn, as the aircraft was lined up for the next racetrack pattern spray run, the aircraft was observed to rapidly pitch down and collide with the ground. Analysis of the limited available recorded data showed that the final turn was flown at a tighter radius than the previous racetrack pattern turns. In combination, this could indicate that the accident was the result of an aerodynamic stall. However, there was insufficient information to determine if that occurred.
The pilot was unable to remember the final turn and could not provide a reason for the track variation or why the aircraft pitched down. No mechanical defects were noted with the aircraft, on the maintenance release, during the previous flight, or up to the section of the accident flight the pilot could remember. A post‑accident inspection of the aircraft by the operator did not identify any defects. From the limited available information, it was not possible to determine the reason for the accident.
The pilot was wearing his own personal flight helmet at the time of the accident. During the accident, the left side of the helmet struck the internals of the cockpit. Based on the degree of damage to the helmet, it probably prevented the pilot receiving more serious head injuries.
Findings
These findings should not be read as apportioning blame or liability to any particular organisation or individual.
During a turn, and for reasons that could not be determined, VH-WHR pitched down and collided with the ground.
The helmet worn by the pilot probably prevented more serious head injury.
Safety message
The International Civil Aviation Organization circular 85-AN/71 Safety in aerial work Part 1. Agricultural Operations discusses the importance of reducing serious head injuries by wearing a correctly fitting flight helmet. Pilots operating aircraft in agricultural operations are particularly vulnerable to accidents involving major or fatal head injury. The circular also discusses the need to select a helmet which provides effective protection and that is part of the pilot’s personal flying equipment as was the case in this accident.
About this report
Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, a limited-scope, fact-gathering investigation was conducted in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.
Publishing information
Released in accordance with section 25 of the Transport Safety Investigation Act 2003
Ownership of intellectual property rights in this publication
Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia.
Creative Commons licence
With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence.
Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work.
The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau
Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.
At 1242 Eastern Standard Time[1] on 18 November 2017, a Bell 206 helicopter, registered VH‑SDZ (SDZ), departed from Middlemount Airport, Queensland with a pilot and crew member on board to conduct power line inspections 32 km to the south.
At approximately 1255, the pilot positioned the helicopter in a hover 30 ft above the ground and 40 metres from a transmission tower so that it could be photographed by the crew member. After 3-4 minutes of hovering, the pilot heard what was described as a ‘very loud bang’ through the airframe, which was also felt through the controls. The helicopter began to shake violently and bounce vertically. The pilot also reported seeing tiny pieces of debris falling in front of the helicopter.
In response, the pilot immediately lowered the collective, intending to land in a clear area below the helicopter, but it did not respond to collective or cyclic control inputs. Instead, the helicopter began to pitch upward and drift backwards. The helicopter then yawed to the right, most likely due to contact with trees behind. The yaw could not be controlled with the tail rotor pedals so the pilot moved the throttle to the idle position. Despite attempts to level the aircraft, the left skid contacted the ground first and the helicopter rolled over.
The pilot moved the throttle and fuel shut off valve to the off position and switched off the battery before both occupants exited the helicopter. The pilot and the crew member were uninjured as a result of the occurrence.
Figure 1: VH-SDZ following collision with terrain
Source: Operator
Component examination
Examination of the helicopter following the occurrence identified that the mast, both pitch links, and the swashplate were fractured. The mast collar set was also fractured and not engaged with the mast[2]. The operator initially suspected that the mast collar set had disengaged in flight.
The mast collar secures the swashplate’s rotating ring to the mast. It is designed to drive the rotating ring at the same speed as the main rotor. If the mast collar is not engaged, the pitch links connecting the swashplate to the rotors are exposed to transverse forces for which they are not designed. This can result in the pitch links winding around the mast.
The fractured components and trunnion bearings (connecting the pitch links to the rotor blades) were sent to Bell Helicopter’s Engineering Laboratories for detailed examination (Figure 2). The initial examinations were also attended by the United States Federal Aviation Administration. Bell provided a report of their findings to the ATSB.
Figure 2: Components examined at Bell Helicopter’s Engineering Laboratories
Source: Bell Helicopter
The hypothesis of mast collar separation was considered by Bell Engineering Laboratories. It was determined that an in-flight separation would likely have resulted in rotational damage on the mast and mast collar splines, which was not observed. The damage observed in the pitch links was also not consistent with a separated mast collar.
Bell Helicopter concluded that all of the fractures, including that resulting in the mast collar separation, were a result of overstress. No pre-existing defect was found and all damage observed was secondary to the occurrence. Seized or damaged trunnion bearings were also considered for inhibited movement of the pitch links, which could result in abnormal bending loads. However, the condition of the trunnion bearings was found to be typical for bearings removed from service.
In summary, there were no findings made during the inspection at Bell Helicopter’s Engineering Laboratories that identified the probable factors contributing to this occurrence. The reason for the loss of control was therefore not determined.
Findings
While hovering, the pilot experienced a loss of cyclic and collective control that resulted in a ground collision. The reason for the loss of control was not able to be determined.
Safety message
This accident highlights how rapidly an emergency situation can develop. Recognising that the pilot had limited control authority on this occasion, regular practice and/or briefing of emergency actions will increase the likelihood of a correct response.
About this report
Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, a limited-scope, fact-gathering investigation was conducted in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.
Publishing information
Released in accordance with section 25 of the Transport Safety Investigation Act 2003
Ownership of intellectual property rights in this publication
Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia.
Creative Commons licence
With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence.
Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work.
The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau
Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.
On 26 September 2017, an instructor and student conducted a training flight in a Diamond Aircraft Industries DA40 aircraft, registered VH-MPM, from Archerfield Airport, Queensland. The flight training organisation was Aircrew Training and Support Pty Ltd, and the purpose of the flight was a simulated Recreational Pilot Licence (RPL) flight test to prepare the student for an upcoming RPL flight test.
The aircraft entered a developed spin during manoeuvres consistent with advanced stall recovery training which likely included intentional incipient spins. The spin continued until the aircraft collided with terrain. The instructor and student were fatally injured, and the aircraft was destroyed.
What the ATSB found
The ATSB found that the aircraft limitation prohibiting intentional spins was intended to include incipient spins. However, the manoeuvre was not defined and some operators considered that the manoeuvre was not an intentional spin. In addition, the aircraft was not certified for developed spin recovery, and the capability of the aircraft to recover from a developed spin had not been established nor was it required to be.
The ATSB also found that the instructor could not or did not prevent the aircraft from entering a developed spin, for reasons that could not be established.
The instructor’s flight records showed no evidence of spin training since his initial instructor training in January 2011. After this initial training, there was no requirement for an instructor to undergo any further spin training. However, a week before the accident flight, the student had mishandled the recovery from an incipient spin and the accident flight instructor had taken control of the aircraft and recovered, showing that he had the ability to recover from a spin at that stage of development.
What’s been done
The ATSB has issued a Safety Advisory Notice (AO‑2017‑096‑SAN-012) for training organisations conducting incipient spins in non-spin-permitted aircraft.
The Civil Aviation Safety Authority will review incipient spin recovery guidance provided in the Flight Instructor Manual.
Safety message
Although the reasons for the accident could not be fully established, the investigation identified varying interpretations of an ‘incipient spin’. Operators and pilots should clarify with manufacturers the extent to which the early stages of a spin are permissible and ensure that aircraft are always operated in accordance with limitations.
Furthermore, operators should have procedures, and instructors should take all steps, to ensure that they maintain the necessary skills to avoid unintentional spins and recover from both incipient and developed spins.
The New Zealand Civil Aviation Authority booklet, Spin Avoidance and Recovery provides valuable guidance for pilots in spin avoidance and recovery. The booklet provides the following advice for pilots regarding spin recovery:
To have a chance at recovery, the pilot must immediately recognise the spin, and its direction, know exactly what to do in the right order, and then execute the procedure correctly the first time.
VH-MPM accident site
Source: ATSB
The occurrence
What happened
On the morning of 26 September 2017, an instructor and student conducted a training flight in a Diamond Aircraft Industries DA40 aircraft, registered VH-MPM, from Archerfield Airport, Queensland. The flight training organisation was Aircrew Training and Support Pty Ltd, and the purpose of the flight was a simulated Recreational Pilot Licence (RPL) flight test to prepare the student for an upcoming RPL flight test.
At 0913 Eastern Standard Time (EST),[1] the aircraft departed Archerfield. The aircraft tracked towards the Archerfield training area and climbed to about 3,000 ft above mean sea level (AMSL).
At 0927, the aircraft entered the training area and commenced sequences consistent with a RPL flight test at altitudes between about 2,600 ft and about 4,500 ft AMSL (Figure 1).[2]
Figure 1: Overview of training area sequences
The figure shows the flight path of VH-MPM and location of accident site. Source: Google Earth and Airservices Australia, annotated by ATSB
From about 0939, radar data showed the aircraft conducted several short climbs followed by brief, rapid descents, which also included changes in heading. These manoeuvres were consistent with advanced stall[3] recovery training (see Wreckage examination).
At 0943:08, radar data showed the aircraft commence a climb to about 4,500 ft with a reducing groundspeed, consistent with further stall recovery training. The data then showed the aircraft’s flight path to be a near vertical descent with an average descent rate of about 6,000 feet per minute.
At 0943:44, as the aircraft descended, the instructor made a MAYDAY[4] broadcast on the area frequency stating ‘…the aircraft is in a sp…’ before the recorded transmission ended.
The descent continued until the aircraft descended below radar coverage with the last recorded radar position almost precisely above the accident site.
A witness, positioned 1.2 km west of the accident site, observed the aircraft turning and described the aircraft in a vertical, tight spiral descent with the aircraft’s nose slightly below horizontal, consistent with a spin (see Aircraft information). The witness described the spin continue for several complete turns until the aircraft collided with terrain.
Radar data indicates that the aircraft collided with terrain at about 0943:50. The instructor and student were fatally injured by impact forces and the aircraft was destroyed. There was no fire.
The instructor held an Air Transport Pilot Licence (Aeroplane), a flight instructor rating with a Grade 1 training endorsement and a Class 1 aviation medical certificate.
At the time of the accident flight, the instructor had over 3,200 hours of flying experience, of which over 170 hours were on the DA40.
Spin training and knowledge
The regulations required that an instructor complete training in developed spin recovery techniques prior to obtaining an instructor rating. After this initial training, there was no regulatory requirement for an instructor to undergo further spin training.
A review of the instructor’s training records showed he underwent developed spin recovery training on 18 January 2011, while training for his initial instructor rating. His employment records and logbooks show no subsequent spin training or assessment. However, there was no requirement to record spins or spin training in pilot logbooks.
Students of the flying school later reported that the instructor advised them of a recent incipient spin (see Spin classifications and recovery) occurrence. About a week prior to the accident flight, the same pairing of student and instructor as the accident flight entered an incipient spin during advanced stall recovery training. The instructor had described the student mishandling the recovery of the incipient spin which led to the aircraft entering an incipient spin in the opposite direction. The instructor then took control of the aircraft and recovered to stable flight.
On the day before the accident, the instructor conducted the ground school training of another pilot as part of the training for the issue of an instructor rating. During this training, the pilot presented a briefing on advanced stall recovery training to the instructor, which the instructor reviewed, took notes and provided feedback.
The ATSB assessment of the instructor’s feedback and notes indicated that the instructor’s knowledge of incipient spin recovery was consistent with established guidelines.
Student
The student was not required to hold, and did not hold, a flight crew licence. The student held a Class 2 aviation medical certificate and had 58 hours of flying experience, of which 19 hours were on the DA40.
Medical information
The ATSB found no indicators that increased the risk of either the instructor or student experiencing a level of fatigue known to have an effect on performance.
Witness reports from family and acquaintances indicate that the instructor and student were in good health and a good mental state prior to the flight. A review of the instructor and student’s medical history and the instructor’s mobile phone data found no indication that the health and or mental state of the instructor or student contributed to the accident. Post-mortem and toxicological examinations of the instructor and student did not reveal any medical issues that may have contributed to the accident.
Wreckage examination
The aircraft impacted terrain at an elevation of 167 ft above mean sea level. On-site examination of the wreckage and surrounding ground marks indicated that the aircraft impacted terrain left wing first, nose-down and rotating to the left at low forward speed. This was consistent with a left upright spin (Figure 2).
The forward fuselage separated at the engine firewall. The wings, centre fuselage, and rear fuselage all separated in a direction consistent with a left spin. Evidence from examination of the engine and propeller was consistent with the engine producing low power at the time of the accident. Although the throttle position could not be determined from the wreckage, evidence from the engine and propeller corresponds to the recommended power setting for spin recovery (idle).
The positions of the rudder, ailerons and elevator at the time of the accident could not be determined, however the wing flaps were retracted. Both fuel tanks were ruptured and the fuel selector was selected to the left fuel tank.
Figure 2: Wreckage comparison
The figure provides a comparison between the wreckage of VH-MPM and the expected wreckage pattern for a spin accident as described by Wood and Sweginnis (1995), Aircraft Accident Investigation. Source: ATSB and Endeavour Books
Examination of the wreckage and maintenance documentation found no evidence of a pre-existing problem that may have contributed to the accident. The accident was not survivable.
Purpose of the flight
The purpose of the flight was to prepare the student for an upcoming RPL flight test. On the day before the accident, the instructor and student conducted a simulated RPL flight test in accordance with Civil Aviation Safety Authority (CASA) form 61-1486 - Recreational Pilot Licence – Aeroplane. During this flight, the instructor determined that the student was not ready for the test. For the flight on the day of the accident, the instructor and student intended to conduct a similar flight to revise the sequences requiring attention.
A handwritten note (Figure 3) was found in the cockpit and was determined to relate to the accident flight. The note listed the following sequences to be conducted in the training area:
unusual attitudes
steep turns
stalls
advanced stalls
practice forced landing
precautionary search and landing.
The order of sequences and markings on the note aligned with the aircraft movements captured by radar. The note indicated that the sequences up to and including stalls had been completed. At the time the aircraft entered the spin, the instructor and student were likely conducting the next incomplete item on the list, which was advanced stall recovery training.
Figure 3: Instructor’s note from accident flight
Source: Queensland Police annotated by ATSB
The advanced stall recovery training component of the simulated RPL test required a student to demonstrate recovery from incipient spins (see Aircraft information) and stalls conducted with different engine power settings, aircraft configurations and entry attitudes.
This sequence requires an instructor or student to configure and manoeuvre an aircraft in a manner that is conducive to an incipient spin. An instructor may also deliberately induce an incipient spin. A student must then demonstrate the correct recovery to stable flight.
The aircraft should not be permitted to enter a developed spin, however, slow recovery action or mishandling during the incipient spin recovery may lead to an aircraft entering a developed spin. If the student does not demonstrate prompt and correct recovery actions, an instructor should take control to prevent the aircraft entering a developed spin.
Aircraft information
General information
The Diamond Aircraft Industries DA40-180 is a four-seat, low-wing, fixed-tricycle-undercarriage aircraft with a glass and carbon fibre reinforced polymer construction. It has a single reciprocating engine driving a variable pitch two bladed propeller (Figure 4). The aircraft was equipped with dual controls for the student and instructor and Garmin G1000 instrumentation. It was not equipped with an aircraft parachute system.
Figure 4: VH-MPM
Source: Operator
VH-MPM was manufactured in 2006 and had a total time in service of 678 hours. It had a valid maintenance release showing no outstanding issues and the last scheduled maintenance was completed on 22 August 2017.
Weight and balance
The aircraft was loaded within weight and longitudinal balance limits for the duration of the flight.
Fuel system and distribution
The aircraft was fitted with a main and auxiliary fuel tank with a combined capacity of 92.5 L in each wing, providing a total fuel capacity of 185 L. A fuel tank selector, positioned on the centre console between the student and instructor, provided for the selection to use fuel from the left or right fuel tanks or to select the fuel off.
Fuel records indicated that the aircraft was loaded with 139 L of fuel prior to departure, sufficient for the planned flight.
The aircraft flight manual contained the following fuel limitation:
Maximum permissible difference between right and left tanks: 8 US gallons (approximately 30 L)
It was not possible to determine the fuel level in each tank prior to take-off or during the flight. The fuel tanks ruptured during the accident and a significant amount of fuel escaped from each tank. Therefore, the distribution of fuel on board at the time of the accident could not be determined.
Intentional spinning limitation
The aircraft flight manual included a limitation stating that intentional spinning was not permitted in the aircraft.
The manufacturer provided the following comment regarding the conduct of incipient spins in VH-MPM:
The DA40 used in this accident is not approved for intentional spins, incipient or otherwise. Inducing a spin is outside of the approved envelope of the DA40.
The manufacturer also advised:
Using rudder deflection to enter an incipient spin, even if the aircraft is immediately recovered from that incipient spin, is an intentional spin and therefore not allowed to be performed with a DA40.
Certification spin testing
The aircraft type was certified in the Normal and Utility categories in accordance with European Aviation Safety Agency (EASA) Joint Aviation Regulations (JAR) part 23.
The aircraft was not approved for intentional spinning, but had been evaluated to meet the requirements of JAR Part 23.221, namely:
a. Normal Category aeroplanes. A single engined, normal category aeroplane must be able to recover from a one-turn spin or a three-second spin, whichever takes longer, in not more than one additional turn, after initiation of the first control action for recovery. In addition –
1. For both the flaps-retracted and flaps-extended conditions, the applicable airspeed limit and positive limit manoeuvring load factor must not be exceeded;
2. No control forces or characteristic encountered during the spin or recovery may adversely affect prompt recovery;
3. It must be impossible to obtain unrecoverable spins with any use of the flight or engine power controls either at the entry into or during the spin; and
4. For the flaps extended condition, the flaps may be retracted during the recovery but not before rotation has ceased.
b. Utility category aeroplanes. A utility category aeroplane must meet the requirements of sub-paragraph (a).
The certification report stated that the aircraft exhibited prompt incipient spin recovery behaviour within the certification requirements. The manufacturer was not required to and did not test the aircraft for fully developed spin behaviour and recovery.
Developed spin recovery
While, the flight manual prohibited intentional spinning, the manual provided the procedure shown in Figure 5 to assist in recovery from an unintentional spin.
Figure 5: Unintentional spin recovery checklist
Source: Diamond Aircraft
Aerodynamic spins
An aerodynamic spin is a sustained spiral descent in which an aircraft’s wings are in a stalled condition, with one wing producing more lift than the other. This difference in lift sustains the rotation and keeps the aircraft in the spin. The nose angle can also vary considerably. In a fully developed, upright, left spin, an aircraft will simultaneously roll[5] to the left while yawing[6] to the left, making a vertical corkscrew path through the air. A spinning aircraft will descend more slowly than one in a vertical dive and it will also have a lower airspeed, which may oscillate.
Incipient phase The incipient phase occurs from the time the airplane stalls and starts rotating until the spin has fully developed. This phase may take two to four turns for most airplanes. In this phase, the aerodynamic and inertial forces have not achieved a balance. As the incipient phase develops, the indicated airspeed will generally stabilize at a low and constant airspeed and the symbolic airplane of the turn indicator should indicate the direction of the spin. The slip/skid ball is unreliable when spinning.
The pilot should initiate incipient spin recovery procedures prior to completing 360° of rotation. The pilot should apply full rudder opposite the direction of rotation. The turn indicator shows a deflection in the direction of rotation if disoriented.
Incipient spins that are not allowed to develop into a steady-state spin are the most commonly used maneuver in initial spin training and recovery techniques.
Developed phase The developed phase occurs when the airplane’s angular rotation rate, airspeed, and vertical speed are stabilized in a flightpath that is nearly vertical. In the developed phase, aerodynamic forces and inertial forces are in balance, and the airplane’s attitude, angles, and self-sustaining motions about the vertical axis are constant or repetitive, or nearly so. The spin is in equilibrium. It is important to note that some training airplanes will not enter into the developed phase but could transition unexpectedly from the incipient phase into a spiral dive. In a spiral dive the airplane will not be in equilibrium but instead will be accelerating and G load can rapidly increase as a result.
The New Zealand Civil Aviation Authority booklet, Spin Avoidance and Recovery provides further useful information. The booklet also provides the following guidance regarding developed spin recovery:
The minimum altitude loss for a textbook recovery will be about 1000 to 1500 feet.
The Australian Civil Aviation Safety Authority did not provide guidance defining the incipient spin manoeuvre.
During the investigation, the ATSB discussed the manoeuvre with the operator’s Head of Operations, the operator’s previous Head of Operations and the Head of Operations of the instructor’s previous employer.
The operator’s Head of Operations described conducting ‘wing-drop’ manoeuvres in the DA40.
The previous Head of Operations commented that incipient spins in the DA40 were risky as spins were prohibited for the aircraft type. This made training in the aircraft difficult.
The Head of Operations of the instructor’s previous employer advised that the flight test requirement was to conduct ‘wing-drop stalls’ and that this did not constitute spinning.
Civil Aviation Safety Authority
Appropriate use of aircraft
CASA provided the following comment regarding training operations using aircraft which are not approved for intentional spins:
If the operator does not have a suitable type of aircraft for a particular kind of training, then CASA would expect the operator to make appropriate arrangements to acquire or loan a suitable aircraft. The Head of Operations of a training operator has the responsibility to ensure the proper allocation and deployment of aircraft.
Incorrect guidance
While the ATSB assessed that the instructor’s incipient spin recovery knowledge was consistent with established guidelines and did not contribute to the accident, the investigation identified incorrect incipient spin recovery guidance provided by CASA.
The CASA publication Flight Instructor Manual, provides the following guidance for incipient spin recovery:
RECOVERY FROM THE INCIPIENT STAGE
As soon as the aeroplane has stalled and commenced to yaw take the appropriate recovery action. Increase power, apply sufficient rudder to prevent further yaw and ease the control column forward sufficiently to un-stall the aeroplane. Point out that if power is to materially assist recovery action it must be applied before the nose of the aeroplane has pitched too far below the horizon otherwise its use will only increase the loss of height.
Increasing engine power prior to an application of sufficient rudder to prevent further yaw and applying sufficient nose-down elevator un-stall the wings as described is inconsistent with established guidelines and manufacturer guidance.
To accomplish spin recovery, always follow the manufacturer’s recommended procedures. In the absence of the manufacturer’s recommended spin recovery procedures and techniques, use the spin recovery procedures in the spin recovery template. If the flaps and/or retractable landing gear are extended prior to the spin, they should be retracted as soon as practicable after spin entry.
Spin recovery template:
1. Reduce the Power (Throttle) to Idle 2. Position the Ailerons to Neutral 3. Apply Full Opposite Rudder against the Rotation 4. Apply Positive, Brisk, and Straight Forward Elevator (Forward of Neutral) 5. Neutralize the Rudder After Spin Rotation Stops 6. Apply Back Elevator Pressure to Return to Level Flight.
The handbook also provides further guidance regarding power use during spin recovery:
Reduce the Power (Throttle) to Idle. Power aggravates spin characteristics. It can result in a flatter spin attitude and usually increases the rate of rotation.
CASA advised the ATSB that this matter will be referred to Safety Education for review and correction as required.
Meteorological information
Data recorded by the automatic weather station at Beaudesert, Queensland, 7 km southeast of the accident site, was provided by the Bureau of Meteorology. The site recorded observations at 30-minute intervals. The recorded observations from 13 minutes prior to, and 17 minutes after the accident, indicated that light winds and clear conditions prevailed.
Video footage obtained from another aircraft operating in the Archerfield training area at the time of the accident showed smooth flying conditions, visibility in excess of 10 km and no cloud at, immediately above, or below 4,500 ft.
Flight data recording
The aircraft was not required to be, and was not, fitted with a flight data recorder.
The aircraft was equipped with Garmin G1000 instrumentation. When fitted with a data card in the relevant port, this system was capable of recording multiple parameters relating to the operation of the aircraft and its systems.
The aircraft did not have a data card installed in the relevant port during the accident flight, therefore no data was recorded.
Similar occurrences
A review of the ATSB occurrence database for the period 2009 to 2019 found the following occurrences involving incipient spin training in aircraft are not approved for intentional spinning:
Occurrence 201704820 – VH-YTE – S.O.CA.T.A. – Groupe Aerospatiale TB-10
At the end of the advanced stalling lesson, the instructor was intending to observe the student’s wing drop recovery. The instructor initiated a right wing drop, however the student’s incorrect use of full aileron during recovery led to spin entry to the right. The instructor took control and recovered the aircraft. The aircraft completed two full rotations and lost 1,200 ft during recovery.
Occurrence 201403058 – VH-EZT – Czech Sport Aircraft – PIPERSPORT
While practicing incipient spins, the instructor initiated a left wing drop. Once the aircraft stalled, the student was asked to recover. The student reduced power with slight delay and applied the incorrect rudder input. The aircraft then turned further left and the instructor directed the application of right rudder. The student did not respond and the instructor took control and initiated spin recovery. The aircraft continued to rotate before recovering about 20 to 30 seconds later. During the recovery the aircraft maximum design load factor was exceeded by 0.1G.[7]
The instructor and student were conducting a simulated Recreational Pilots Licence test in preparation for an actual test. This flight included a sequence of advanced stalls that increased the risk of spin entry and likely included intentional incipient spins.
The instructor’s note, found within the wreckage, along with radar data, indicated that they were conducting an advanced stall sequence at about 4,300 ft above ground level when the aircraft entered a spin.
Sufficient height was available for the aircraft to recover under normal conditions, however, the flight crew did not recover from the spin before colliding with terrain. Examination of the wreckage showed that the aircraft was in a left spin when it impacted the ground.
The absence of recorded data limited the ability of the investigation to determine how the aircraft entered and why it did not recover from a developed spin. It was not possible to determine whether correct recovery inputs were made during the spin without recovery, or other factors prevented recovery.
Examination of the wreckage and aircraft maintenance history found no outstanding issues or defects which may have contributed to the developed spin, or prevented recovery from an incipient spin.
Instructor spin recovery technique
During the advanced stalling sequence, an instructor initiates an incipient spin, or operates the aircraft in a way which may induce an incipient spin. A student then must demonstrate a prompt recovery to stable flight. Should the student not effect prompt recovery, an instructor should take control of the aircraft and effect recovery prior to entering a developed spin.
The ATSB were advised that a week before the accident flight, the accident flight student had mishandled the recovery from an incipient spin leading to an incipient spin in the opposite direction. The accident flight instructor had taken control of the aircraft and recovered, showing that he had the ability to recover from a spin at that stage of development. However, the aircraft movement or instructor and student actions may have been different on the accident flight.
Intentional incipient spinning not permitted in the aircraft
The flight was being conducted as a simulated Recreational Pilots Licence test. This test requires that a student demonstrate an ability to recovery from an incipient spin. Therefore, the flight requires that an intentional incipient spin be induced in order for the student to demonstrate that ability.
The aircraft flight manual included an operational limitation that prevented intentional spinning in the aircraft. The aircraft manufacturer clarified that this limitation includes intentional incipient spins, even if the aircraft is immediately recovered.
There was no clear and consistent definition of the point at which a manoeuvre becomes a spin (or incipient spin) for the purposes of flying training. Discussions with the operator and other flight training organisations, along with the instructor’s previous incipient spin training in the aircraft type indicated that different interpretations of the intentional spin limitation existed. The investigation found that the incipient spin manoeuvre has been considered at least by some in industry to not be an intentional spin, as prohibited by some aircraft types. Furthermore, the conduct of the incipient spin manoeuvre using non-spin-permitted aircraft types has been occurring in Australia.
Aircraft spin certification
The aircraft was not certified for and had not been tested for recovery from a developed spin. While test pilots had demonstrated the aircraft type’s prompt recovery from a spin of not more than one turn, the capability of the aircraft type to recover from a spin of more turns was not proven. Therefore, the possibility remains that recovery using correct inputs beyond about one full turn or three seconds may not have been not possible.
Findings
From the evidence available, the following findings are made with respect to the collision with terrain involving Diamond DA40, VH-MPM that occurred 42 km west of Southport Aerodrome, Qld, on 26 September 2017. These findings should not be read as apportioning blame or liability to any particular organisation or individual.
Contributing factors
The instructor could not or did not prevent the aircraft from entering a spin. The spin continued until the aircraft collided with terrain.
Other finding
Immediately prior to the spin entry, the aircraft was conducting the advanced stalling sequence which likely included incipient spins. Intentional spins were not permitted in the Diamond DA40. The aircraft manufacturer stated that the intentional spin limitation included intentional incipient spins.
The aircraft was not certified for developed spin recovery and the capability of the aircraft to recover from a developed spin had not been established.
Safety action
Safety advisory notice
Safety advisory notice to training organisations
The ATSB identified concerns relating to the conduct of incipient spin training in aircraft types for which spinning is prohibited.
The DA40 aircraft type is certified to recover from a one-turn spin or a three-second spin (whichever takes longer), and is not proven or certified to be recoverable from a longer spin. The aircraft’s manuals state that intentional spins are prohibited. During the ATSB investigation, the aircraft manufacturer clarified that this limitation prohibits any action that is intended to induce a spin, even if the aircraft is immediately recovered.
Aircraft types with similar limitations are currently in use throughout the world for flying training. In Australia, the Civil Aviation Safety Authority requires the demonstration of recovery from an incipient spin during flight tests. However, there is no clear and consistent definition of the point at which a manoeuvre becomes a spin (or incipient spin) for the purposes of flying training.
Crucially, the ATSB found that there can be varying interpretations of an ‘incipient spin’, and this has led to aircraft not approved for intentional spins being used for incipient spin training and assessment.
Operating an aircraft within the stated limitations is essential to the safe conduct of a flight. Training organisations are required to conduct incipient spin recovery training, which includes intentionally inducing a spin and recovering before it fully develops. Some organisations may be conducting this training in aircraft not approved for intentional spinning. The Australian Transport Safety Bureau advises these training organisations to clarify with aircraft manufacturers the extent to which the intentional entry into the early stages of a spin, including an incipient spin, is permissible.
Additional safety action
Whether or not the ATSB identifies safety issues in the course of an investigation, relevant organisations may proactively initiate safety action in order to reduce their safety risk. The ATSB has been advised of the following proactive safety action in response to this occurrence.
Civil Aviation Safety Authority
CASA has advised the ATSB that they have taken the following safety action:
Guidance material review
CASA is reviewing the Spins and Spirals section of the Flight Instructor Manual for correction as required.
Under Part 4, Division 2 (Investigation Reports), Section 26 of the Transport Safety Investigation Act 2003 (the Act), the Australian Transport Safety Bureau (ATSB) may provide a draft report, on a confidential basis, to any person whom the ATSB considers appropriate. Section 26 (1) (a) of the Act allows a person receiving a draft report to make submissions to the ATSB about the draft report.
A draft of this report was provided to the instructor and student’s next of kin, the flight training organisation, the aircraft maintainer, the aircraft manufacturer, the Civil Aviation Safety Authority, the Austrian Safety Investigation Authority, the Transportation Safety Board of Canada, the Queensland Coroner’s representative and the Hong Kong Civil Aviation Department.
Any submissions from those parties were reviewed and where considered appropriate, the text of the draft report was amended accordingly.
Purpose of safety investigations
The objective of a safety investigation is to enhance transport safety. This is done through:
identifying safety issues and facilitating safety action to address those issues
providing information about occurrences and their associated safety factors to facilitate learning within the transport industry.
It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action.
Terminology
An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue.
Publishing information
Released in accordance with section 25 of the Transport Safety Investigation Act 2003
Ownership of intellectual property rights in this publication
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On the evening of 8 September 2017, an instructor and student from the Australian International Aviation College were preparing to conduct night training circuits at Port Macquarie Airport, New South Wales, in a Diamond DA40 NG aircraft, registered VH-YPQ. As it was the student’s first time conducting night circuits, once lined up on the runway, the instructor took the aircraft controls for the take-off.
After take-off, as the aircraft climbed, the instructor heard and felt the engine and propeller surging. Propeller speed and engine power fluctuations occurred from about 200 ft above the runway and increased in amplitude as the aircraft climbed to about 400 ft. Recorded data showed that the engine was producing full power despite the fluctuations. The instructor interpreted the fluctuations as a partial engine power loss and commenced a left turn, aiming to return and land on the runway in the opposite direction to the take-off. The instructor had considered landing straight ahead but assessed that there was power available to turn and that they would be unable to see and avoid trees or to be sure to land in a suitable clearing ahead.
In the 10 seconds that the instructor was assessing and making decisions about a perceived partial power loss, the airspeed reduced from 75 to 69 kt due to the aircraft’s nose-up pitch attitude. Then, at the same time as commencing the turn back towards the runway, the instructor reduced engine power to 30 per cent, while maintaining a nose-up attitude, and the airspeed reduced rapidly.
During the turn, the aircraft aerodynamically stalled resulting in a loss of control. Although the aircraft pitched down and the instructor subsequently increased the power, control was not regained. The aircraft descended and collided with trees, coming to rest inverted. The student and instructor were seriously injured, and the aircraft was destroyed.
What the ATSB found
After reducing the power, the instructor did not maintain adequate airspeed during the turn. This resulted in an aerodynamic stall, loss of control and collision with terrain.
The aircraft manufacturer could not determine the reason for the engine speed fluctuations. Propeller speed fluctuations had occurred in other aircraft, and either resolved without pilot input or by moving the power lever.
Although not contributing to this occurrence, in the course of the investigation it was found that engine cylinder heads for the aircraft type were cracking prior to reaching their service life.
What's been done as a result
After the accident, the Australian International Aviation College:
added a requirement to the take-off safety briefing to include setting partial power safety speed in the event of a partial power loss
conducted partial engine failure after take-off training for instructors and students, comprising pre-flight planning and self-briefing, ground training, and flight training
performed flight simulator tests for partial engine failure after take-off conditions in each single engine aircraft model operated by the flying school to assess the power required to maintain altitude in the event of a partial power loss.
Safety message
In this accident, the instructor perceived there was a partial power loss. The ATSB research report Avoidable Accidents No. 3 – Managing partial power loss after take-off in single-engine aircraft provides information to assist pilots maintain aircraft control in the event of an emergency or abnormal situation after take-off. The report prescribed initial actions to be considered including:
Lower the nose to maintain the glide speed of the aircraft. If turning is conducted, keep in mind an increased bank angle will increase the stall speed of the aircraft.
Maintain glide speed and assess whether the aircraft is maintaining, gaining or losing height to gauge current aircraft performance.
Fly the aircraft to make a landing, given the aircraft’s height and performance, and the pre-planned routes for the scenario.
The occurrence
On the evening of 8 September 2017, an instructor and student from the Australian International Aviation College (AIAC) planned to conduct night circuits at Port Macquarie Airport, New South Wales, in a Diamond DA40 NG aircraft, registered VH-YPQ. The student taxied the aircraft to runway 21, then, as it would be the student’s first time conducting circuits at night, the instructor took over the controls for the take-off.
It was dark and the moon had just risen above the horizon when the aircraft commenced the take-off roll at 1957:12 Eastern Standard Time[1] (Figure 1). During the initial climb, about 20 seconds after lift-off, while still above the runway and passing 200 ft, the instructor noticed changes in the engine sound, felt acceleration changes and saw fluctuating indications on engine load and propeller RPM gauges, despite maintaining the power lever in the fully forward maximum power position.
The fluctuations increased over the next 20 seconds as the aircraft climbed. During that time, the aircraft pitched up to about 8 degrees, consistent with the normal attitude for initial climb and to achieve the best rate of climb speed, and the vertical speed increased to more than 900 ft per minute. The instructor assessed that the fluctuations were due to an engine problem and considered the options for landing.
The instructor considered landing straight ahead, however, while there were two fields that may have been suitable for a landing, they were not visible at night and the instructor was concerned the aircraft may land beyond the field in trees. While still above the runway and climbing through about 400 ft, and as the engine was still producing power, the instructor elected to conduct a left turn, aiming to land on the reciprocal runway, 03. The left turn commenced at 1957:58 and 1 second later, the instructor moved the power lever aft, reducing the engine load to about 30 per cent, where it remained for the next 10 seconds.
At 1958:01, the instructor broadcast on the common traffic advisory frequency[2] that they had engine problems and would land on ‘runway 21,’ although actually intending to land on runway 03.
The instructor recalled concentrating on trying to maintain adequate speed—not ‘nosing up too much getting closer to the stall speed or nosing down and not being able to make the runway.’ As the aircraft turned and the runway came into sight, the instructor assessed that the aircraft was not going to make it back as the runway was too far away and the airspeed was too slow. The instructor also recalled looking down and all that could be seen was the trees.
The instructor made changes with the power lever to see if the fluctuation issue improved. Engine data showed the power lever position moving to maximum power for 3 seconds, back to 25 per cent engine load for less than 2 seconds then to full power for the final 4 seconds. The instructor also noticed signs of an impending aerodynamic stall[3]—buffeting and sloppy controls, followed by a left wing drop. The aircraft entered uncontrolled flight, descended rapidly and impacted trees and terrain.
The aircraft collided with trees about 18 seconds after the left turn commenced, 325 m abeam the runway 03 threshold, and came to rest inverted (Figure 1). Both occupants were seriously injured and the aircraft was destroyed.
Figure 1: Aircraft flight path and key events
Source: Google Earth, annotated by the ATSB based GPS, engine control unit and radio recordings, and accident site assessment
The Australian International Aviation College (AIAC) was a flight training and charter organisation based in Port Macquarie, New South Wales. It conducted flight training for up to 90 Australian and international students, from initial training through to commercial pilot licence, and single and multi-engine aeroplane, instructor and instrument flight ratings. The AIAC operated a fleet of Diamond aircraft and an approved flight training device (simulator).
Instructor qualifications and experience
The instructor:
held a commercial aeroplane pilot licence issued in April 2014
held a valid Class 1 medical certificate issued in March 2017 with the restriction that distance vision correction must be worn
held instrument and instructor ratings
met the recency requirements for the planned night circuits
satisfactorily completed flight crew emergency procedures training at AIAC in February 2017
completed a flight instructor standardisation and proficiency check in January 2017 including attaining a Grade 2 instructor rating
obtained an instrument rating training endorsement for single-engine aircraft below 5,700 kg in June 2017
had accrued 1,160.9 hours total aeronautical experience, including 86.2 hours in command at night (73.7 in single-engine aircraft and 12.5 in multi-engine aircraft) and 680.7 hours instructing in single-engine aircraft
logged 124 hours in the DA40 NG and DA42 NG (diesel-engine) aircraft in 2017.
Student pilot experience
The student pilot commenced flight training at AIAC in March 2017 and completed a recreational pilot licence test on 24 May 2017. The student had accrued a total of 85.4 hours flying time, of which 19.8 were as pilot in command.
Weather and environmental information
The weather was fine with light winds and little to no cloud. The time of the occurrence was past astronomical twilight and the nearly full moon was just above the horizon. The township of Port Macquarie provided some light and a horizon reference to the east but the ground near the airport was dark apart from a few scattered dwellings. The instructor reported that the moon and town lights were below their field of vision during the initial stage of the flight.
The Bureau of Meteorology recorded the wind strength and direction at Port Macquarie Airport at 1-minute intervals. Nil wind was recorded at the aerodrome for the 20-minute period encompassing the short duration of the accident flight. Although the aircraft took off with nil wind at runway level, according to GPS data, it encountered an increasing tailwind of up to 8 kt during the climb and turn. As the aircraft climbed, the temperature increased from 12.5 °C at runway level to 16.5 °C at the maximum height reached.
Aircraft information
General information
The Diamond Aircraft Industries DA40 NG aircraft is a four-seat, low-wing, T-tail aircraft constructed from composite materials. The aircraft is factory-fitted with a turbo charged four-cylinder diesel Austro E4 engine, operated on aviation turbine fuel, and a three-bladed wooden composite variable-pitch MT-Propeller MTV-6-R propeller.
VH-YPQ
The aircraft serial number 40.N292 was manufactured in 2015 and placed on the Australian register in early 2016 as VH-YPQ (Figure 2).
The aircraft had a current certificate of airworthiness and maintenance release[4] with no outstanding maintenance or defects notated. The aircraft had a total time in service of about 906 flight hours before the accident flight. The logbook statement indicated that the aircraft was maintained in accordance with the Diamond Aircraft DA40 NG maintenance schedule. It was equipped and certified for operation under the instrument flight rules[5] and was maintained and operated in the Charter Class B category.
Figure 2: VH-YPQ
Source: Simon Coats
System description and information
Engine and propeller control
The constant speed propeller has a governor, which changes the blade pitch to maintain a constant RPM, regardless of the amount of engine torque, airspeed or altitude. The aircraft’s maximum take-off propeller speed was 2,300 RPM.
The engine and propeller were controlled by a single electronic engine control unit (ECU) with dual-redundant hardware that performed continual self-testing. A single power lever provided command input via two separate channels to the ECU and the ECU controlled the engine fuel injection to match the power lever command. For redundancy, there was a cockpit switch for selecting ECU channels in case of a fault.
Integrated instrument and avionics system
VH-YPQ was factory-fitted with a Garmin G1000 integrated avionics system, which consolidated all communication, navigation, surveillance, automatic flight control system, primary flight instrumentation, engine indication, and annunciation systems on two liquid crystal display units (DU) and an audio panel. The two DUs consisted of a primary flight display on the left (student pilot side), and the multi-function display (MFD) on the right (instructor side). The audio panel was located between the two display units. The aircraft was not fitted with the optional terrain awareness and warning system.
Recording capability
The G1000 avionics system was capable of storing up to 60 flight and engine parameters on a data memory card. Data was logged to a new file that was created each time the MFD was powered on. All parameters were recorded at 1-second intervals. The electronic ECU was capable of storing significant amount of engine data and had a backup battery for redundancy.
Aircraft weight and balance
The aircraft was assessed as being within the weight and balance limits throughout the accident flight, with a take-off weight of 1,143 kg.
Relevant speeds
Best glide speed is used to achieve the greatest distance for the height in case of engine failure. At any airspeed faster or slower than the best glide speed, the aircraft will travel less distance over the ground.
According to the Airplane Flight Manual, the best glide speed (‘airspeed for best glide angle’) for the aircraft with flaps up was 88 kt, and ‘airspeed for emergency landing’ with engine off and flaps in the take-off position was 78 kt.
The best rate of climb speed (VY) was 72 kt with take-off flaps set. Therefore, in the event of a power loss when in the climb at VY, the pilot would need to lower the aircraft nose to achieve the best glide speed, and the airspeed for emergency landing.
Accident site examination
The aircraft initially impacted trees causing significant structural damage to the wings, after which it impacted terrain inverted and at a nose-down angle of about 25°. The cockpit was partially collapsed, with the airframe resting on the instrument panel and seat backs. Both wings and the tail detached during the impact sequence (Figure 3).
Figure 3: Wreckage of VH-YPQ, which was partially disturbed during rescue of the occupants
Source: ATSB
Examination of the aircraft wreckage found no pre-existing airframe issues. The flap actuator was found in the take-off position. The aircraft’s fuel tanks were breached and there was evidence of fuel spillage. A small quantity of fuel was drained from the tanks and matched the characteristics of aviation turbine fuel. It tested negative to water content. Previous fuel records and the engine data both indicated that there was sufficient fuel on board the aircraft for the intended flight.
The engine was examined externally with the cowls removed and there was no noted fluid leakage or pre-impact defects identified. During removal of the engine and control parts, no defects were identified. The propeller blades were fragmented, consistent with the engine driving the propeller when the aircraft impacted with terrain. The propeller and propeller control unit were removed from the aircraft for function testing.
The G1000 avionics unit data memory card and electronic ECU memory module were removed from the aircraft and transported to the ATSB technical facilities for examination and download.
Component testing
Propeller hub and propeller control
The propeller hub and controller were sent to the propeller manufacturer for testing. No faults were identified during function testing or visual examination.
Manufacturer data analysis
The aircraft and engine manufacturers analysed the recorded data and could not determine the cause of the propeller speed fluctuations. The engine manufacturer reported that the oscillation was still in a normal range and did neither create an ECU warning nor a reduction of power. There are lots of possible reasons for RPM oscillation but in this case they were not engine related.
They advised that at the propeller speeds that were recorded during the last 40 seconds before the accident, the propeller should have been sitting on the fine pitch limit stops. Whether the propeller was at full fine pitch during the fluctuations could not be determined as the actual propeller blade pitch angle was not sensed or recorded. Fuel injection quantity and timing were not recorded on the ECU, but fuel quantity and fuel flow were recorded on the Garmin system. In the recorded Garmin data, the fuel flow rate increased and decreased in step with the propeller RPM and in response to the changes in power lever position.
Assessment of possible causes of RPM fluctuations
Figure 4 is an extract from the aircraft maintenance manual, which provided troubleshooting for fluctuating propeller RPM from a list of possible causes.
Figure 4: Extract from the aircraft maintenance manual
Source: Diamond Aircraft
From the listed possible causes, the post-accident inspection found the following.
The engine gearbox oil level was not measured, but the ATSB assessed its quantity as unremarkable. There was no sign of an oil leak on or around the engine that would have depleted the oil quantity.
No defects or metal debris were identified in the gearbox oil filter or magnetic chip detector.
No faults were identified with the electrical wiring harness.
The propeller governor was satisfactorily tested by the propeller manufacturer and all measurements and adjustments were found to be within tolerances.
Recorded data
Recorded data from the G1000 memory card and ECU memory module was analysed. The data from the two sources correlated to within about 2 seconds. Selected data is displayed in the graph in Figure 5. In this graph, the altitude, airspeed, ground speed, pitch and roll were retrieved from the G1000 and the propeller speed (RPM), power lever position and engine load were from the ECU. The altitude is accurate to within 30 ft.
Propeller speed fluctuations
According to the data, the aircraft lifted off at 1957:26. Twenty seconds later, the aircraft climbed through 200 ft at an airspeed of 74 kt. The propeller RPM began fluctuating about 10 RPM per second above and below 2,250 RPM. The power lever remained constant in the maximum power position and the engine load made small fluctuations around 98.5 per cent power, consistent with the RPM fluctuations.
The RPM and engine load fluctuations increased in amplitude as the aircraft climbed. The engine manufacturer advised that fluctuations up to ± 20 RPM were acceptable, although no normal operating range of fluctuations was defined. That ‘acceptable’ change in amplitude was first exceeded at 1957:47, 218 ft above the runway.
The fluctuations continued to increase in amplitude over the next 10 seconds to a maximum variation of 73 RPM in 1 second (which equated to about 3 per cent of an average 2,250 RPM) as the aircraft climbed to 361 ft.
Figure 5: Plot of selected engine and aircraft GPS data parameters
Image shows increasing fluctuations in propeller RPM and engine load, followed by a sequence of power lever movements with corresponding RPM and load variations.
Source: Austro Engine and Garmin 1000 data analysed by ATSB
Manoeuvring
As the aircraft climbed through 300 ft above the runway, the airspeed reached 75 kt, which was the maximum achieved on the flight. Over the next 10 seconds the airspeed decreased to 69 kt as the pilot maintained a pitch-up attitude of about 8 degrees, and the aircraft climbed at a rate of up to 938 ft per minute. After reaching a peak pitch-up of 8.3 degrees and still climbing at 928 ft per minute, the pilot started to reduce the aircraft’s pitch attitude.
At 1957:58, as the aircraft was climbing at 904 ft per minute through 389 ft, the airspeed had reduced to 69 kt and a left bank (roll) commenced. At that time, the aircraft was still pitched up about 7 degrees. One second later, the power lever was moved to a lower power setting that corresponded with an engine load reduction to about 30 per cent and the propeller speed decreased to about 1,750 RPM.
Over the next 4 seconds, the aircraft continued to climb albeit at a reducing rate, the airspeed continued to decrease, and the angle of bank increased. At 1958:05, the maximum altitude of about 430 ft was reached, airspeed was 59 kt and the aircraft nose then pitched down. The aircraft then started to descend. The last Garmin data recorded was at 1958:07 with the airspeed at 59 kt (which it had been for 4 seconds), a 29-degree angle of bank and a propeller speed of 1,720 RPM.
The ECU data indicated that at 1958:09, the power lever was moved forward for 3 seconds, back for 2 seconds then forward for the final 4 seconds and the engine load increased and decreased correspondingly. The last recorded ECU data at 1958:17 was consistent with the aircraft colliding with terrain.
Uncontrolled descent
The G1000 memory card was missing approximately the last 12 seconds of data. This was likely due to the unit’s power being cut abnormally during the accident sequence, instead of a normal system shutdown. Consequently, the aircraft’s final descent and flight path were not recorded. Based on alignment between the accident site location, direction of travel and the final recorded position, the left turn and steep descent continued until impact. The aircraft descended from 428 ft in 10 seconds, which was an average descent rate of 2,568 ft per minute.
The stalling speed with power off (VS) for the aircraft weight and take-off flap was 58 kt indicated airspeed (KIAS) at 0° angle of bank, and 62 KIAS at 30° angle of bank. The last recorded airspeed was 59 KIAS when the bank angle was about 30°, below the power-off stalling speed.
No ECU faults were recorded.
Aircraft performance testing
Following the accident, the AIAC conducted in-flight performance testing of partial engine failure scenarios. With an aircraft weight of 1,156 kg (similar to the accident flight), a DA40 NG aircraft maintained level performance (occasional 100 ft per minute climb) and airspeed at a safe margin above the stalling speed, with 30 per cent power, flaps in the take-off position and glide attitude set, including in a turn.
Regulatory requirements
The Civil Aviation Safety Regulations (CASR) Part 61 Manual of Standards (MOS) detailed competency standards for all flight crew qualifications as well as proficiency checks, flight reviews and flight test standards.
Competencies specified for private and commercial aeroplane pilot licence and single-engine aeroplane class ratings included managing a simulated engine failure after take-off in the circuit area, but not partial power loss. Underpinning knowledge of the competencies included ‘engine failure scenarios and procedures for partial and complete power loss.’
Competencies specified for the night visual flight rules (NVFR) rating included skills and knowledge required for managing emergency situations at night including that ‘(in simulated conditions) aircraft control is maintained.’ The Airservices Australia Aeronautical Information Publication En Route 1.1 did not permit simulated engine failures to be conducted below 1,500 ft at night in the circuit area.
The Part 61 MOS Unit A5 – Advanced stalling, included that a pilot is required to demonstrate recovery from a stall with full or partial loss of engine power. The Civil Aviation Safety Authority’s (CASA’s) Flight instructor manual stated:
Before carrying out any advanced stalling exercise it is important that sufficient height is gained to ensure recovery by 3,000 feet above ground level…
CASA advised that competency in this standard ‘should mitigate [against the] risk of partial power loss in the take-off.’
Operator procedures
Managing partial power loss after take-off
The AIAC syllabus of training was in line with the Part 61 MOS requirements and did not reference partial engine failure after take-off or in the circuit. However, the AIAC standard operating procedures included expanded procedures for engine failure immediately after take-off with insufficient/partial engine power. It listed the following considerations in managing a partial power loss after take-off:
When faced with a partial power loss, the pilot in command should not try to diagnose the engine problem at the expense of maintaining aircraft control;
Climbing at the aircraft’s best rate of climb speed will maximize options if a partial power loss or total power loss occurs;
Lower the nose to maintain the glide speed of the aircraft (if unable to climb);
If a partial power loss has occurred with remaining runway, the earlier a decision is made to cut remaining engine power, the greater landing distance is available; the immediate extension of landing flaps is recommended as this will also help to reduce the aircraft groundspeed prior to ground contact;
Conduct the Phase One checks as outlined in the QRH. However, this should only be done if there is sufficient time;
Maintain best glide speed and assess whether the aircraft is maintaining, gaining or losing height to determine current aircraft performance. This will assist in making decisions in the available options for landing.
Fly the aircraft to make a landing, given the aircraft’s height and performance, and the pre-planned routes for the situation. If any turning is conducted, be mindful that an increased bank angle will increase the stall speed of the aircraft. Keeping the aircraft in balance will also minimize rate of descent in any turn.
Re-assess landing options throughout any manoeuvers. Be decisive but be prepared to modify the plan if required.
Maintain glide speed up to the point of landing flare; this will ensure that when flaring there is enough energy to arrest the vertical descent rate.
Circuits under the night visual flight rules
At the time of the accident, the AIAC NVFR training syllabus included 5 hours of night circuits. Prior to commencing night circuits, students were given a briefing by an instructor. The briefing included human factors, illusions that can occur at night, lighting and flight with reference to instruments. It did not include emergencies, but students received a briefing on circuit emergencies earlier in their training. Additionally, at night, company pilots were required to conduct the climb after take-off at the best rate of climb speed.
Quick reference handbook
Emergency and non-normal procedures were detailed in the AIAC Quick Reference Handbook (QRH). These were derived from the emergency procedures detailed in the Airplane Flight Manual. The QRH included ‘Phase 1 checks’ that were printed in bold type. The Phase 1 checks were ‘recall items’ required to be committed to memory. The other, ‘Phase 2’ checks were not memory recall items and the QRH checklist was required to be used when carrying out these checks.
Two QRH procedures were relevant to the accident flight: the checklist for partial or full engine failure after take-off and the ‘defective propeller RPM regulating system’ checklist. The first of these is depicted in Figure 6. Nearly all the items were in bold and were therefore memory recall items. The first (memory recall) item was to achieve an airspeed of 88 kt with flaps up, or 77 kt with flaps in the take-off position. The second item, if time permitted, was to check the power lever was at maximum.
Figure 6: QRH checklist for partial or full engine failure after take-off
Source: AIAC
In this occurrence, the instructor assessed the speed fluctuations as symptomatic of a partial power loss, although the engine was still producing maximum power. The instructor reported confirming the power lever was in the full power position.
The engine manufacturer reported that the defective propeller RPM regulating system procedure had been in the airplane flight manual of the DA40 D aircraft, which had a different engine, since 2003. The procedure was introduced due to issues with the propeller control system of that engine type, but was still a valid procedure to be followed in case of oscillating RPM in the DA40 NG aircraft and in the DA40 NG flight manual.
The QRH defective propeller RPM regulating system checklist carried the following warning:
IN CASE OF DEFECTIVE RPM REGULATING SYSTEM, REDUCED ENGINE PERFORMANCE SHOULD BE ANTICIPATED.
For oscillating RPM, the first action, was:
POWER setting…………..CHANGE
If problem does not clear;
VOTER Switch……………Swap between ECU A and ECU B
If problem does not clear;
VOTER Switch……………AUTO
Land at nearest suitable airport
Revise ENGINE FAILURE DURING FLIGHT checklist (Page-322).
END OF CHECKLIST
The instruction to change the power setting was not a memory recall item. The AIAC Operations manual section QRH procedures stated that ‘the QRH should not be referred to unless flight crew workload is sufficiently low to operate the aircraft while the checks are conducted,’ and that, in visual meteorological conditions, the pilot was not to refer to the QRH (for non-recall items), unless the aircraft was at or above minimum/lowest safe altitude, and/or other safe conditions could be met.
The aircraft manufacturer advised that changing the power lever angle in accordance with the procedure should fix a problem such as that encountered in the accident occurrence, because ‘changing the operating state of the engine will typically stop periodic interactions of systems and thus stop RPM fluctuations.’
The AIAC head of operations considered that the engine fluctuations were ‘very small’ and should have been able to be remedied by changing power setting/moving the power lever slowly back and forth (then changing the ECU switches if necessary), in accordance with the QRH checklist. However, the instructor had not been aware of similar issues within the operator’s aircraft fleet before the accident and reported that similar events had not been discussed or trained for by the operator to a point of being memorable.
Decision making
Pilots operate in a safety-critical environment and need to be trained and supported to make the best possible decisions in challenging conditions. Orasanu (2010)[6] stated that
in many high-risk consequential environments, time for making a decision is limited, information is incomplete, conditions change dynamically, and goals shift, rendering analytic decision-making impractical, if not impossible.
Orasanu detailed ways in which expert knowledge contributes to cockpit decision-making. These included quick and accurate interpretation of a problem and performing rehearsed responses. Where a pilot made an error or did not select the best solution, it may be due to an incorrect interpretation of the situation, or choosing an inappropriate course of action.
The instructor had not previously experienced propeller speed fluctuations and interpreted the problem as a partial power loss. The ATSB Avoidable Accidents No. 3 publication, Managing partial power loss after take-off in single-engine aircraft, stated that while following a complete engine failure, a forced landing was inevitable, a partial power loss required the pilot to make a decision whether to continue flight or land immediately. Research for the publication found that in 145 of 160 occurrences where a pilot turned back to the runway following a partial power loss, the aircraft made it to within the aerodrome grounds. However, the increase in stall speed during the turn and the associated potential for a loss of control meant that the consequences of a mishandled turn back were more serious than a controlled forced landing.
The publication suggested four main considerations when assessing if a turn back to the aerodrome is possible. These were:
• height available
• remaining engine power available – do you have enough power to climb?
• increased stall speed associated with any increase in angle of bank increasing the risk of an aerodynamic stall
• level of confidence in the remaining engine power – but assume the engine may fail at any moment.
Take-off safety briefing
The ATSB Avoidable Accidents publication also stated that pilots should self-brief prior to each and every take-off. The take-off brief ‘serves as a reminder of your planned actions in the event of an emergency such as a partial power loss.’ Planning actions under non-stressful and controlled circumstances prepares pilots for a quick response, reducing mental workload and mitigating some effects of decision making under stress, such as reduced short-term memory, if an emergency situation does eventuate.
The AIAC operations manual specified that a take-off safety briefing must be given by the pilot flying[7] at the completion of pre-take-off checks.
The company take-off safety briefing was:
1. Any emergencies prior to VR[8] I will reject the take-off.
2. Any emergencies at or after VR I will reject and land on remaining runway or clearway.
3. Any emergencies airborne with no runway remaining I will pick a landing area 30° either side of the nose and conduct a forced landing.
4. Special considerations – unique airport information, weather conditions, terrain or obstacles on departure, other known risks and intentions.
The take-off safety briefing did not specify what events constituted an emergency.
The instructor recited their normal take-off safety briefing as:
If there was anything on the ground, power to idle, brakes to come to a stop. Airborne with runway remaining, nose down land on the remaining runway. Airborne with insufficient runway remaining, pick an area either side of the nose, nose down, maintain glide speed, consider flap and then shutdown checks.
Related occurrences
Aircraft operator fleet events
After the accident involving VH-YPQ, the pilot of a twin-engine Diamond DA42 aircraft with a similar engine type to VH-YPQ and operated by AIAC, experienced a similar propeller RPM fluctuation event, where it varied about 50 RPM. In that event, the wind was gusting to 25 kt. During the take-off, there were some RPM changes due to wind gusting, but the pilot reported that was normal. Passing about 400 ft during the climb, fluctuation noise caught the pilot’s attention. The pilot reduced the power to 85 per cent and after 5 to 6 seconds returned it to full power, and the fluctuations, noise and vibration ceased. The reasons for that fluctuation could not be determined from post-event examinations.
The aircraft maintainer provided extracted data of five similar fluctuation events from the aircraft operator’s fleet. The last 3 hours of engine operating data were routinely downloaded from the ECU at each 100-hour maintenance event. Within that data, which represented 3 per cent of an aircraft’s operating time, the maintainer found that oscillations/fluctuations in RPM were present ‘quite a lot of the time.’ Of the five sample events provided to the ATSB, four had fluctuations of greater magnitude than the accident flight. Only one of the five sample events was reported to the maintainer by the flight crew, and they reported ‘hunting’ of power and propeller RPM and that the aircraft was operating in turbulent conditions at the time.
The aircraft maintainer advised that the level of oscillation recorded in the ECU data for the accident flight was ‘quite common’ for the aircraft type (in the AIAC fleet) and believed they were generally introduced by an outside influence such as slight turbulence. The aircraft operator also reported that it was ‘common to observe and hear changes in propeller pitch on DA40 NG aircraft when flying in gusting wind conditions.’
The aircraft manufacturer advised that they were not aware of RPM fluctuations caused by windshear, gusts or turbulence, and that these would normally be eliminated by the governor. The AIAC chief engineer reported that in other previous occurrences of propeller fluctuations involving AIAC aircraft, the fluctuations had reached a maximum amplitude then reduced to near zero without pilot input.
Other aircraft events
In addition to the two events involving AIAC aircraft, the engine manufacturer reported that it was aware of 16 other events on aircraft fitted with the AE300 engine worldwide, involving fluctuations in propeller speed and load, none of which resulted in an accident. The engine manufacturer reported that in all cases, fluctuations ceased with a change in power lever position. Fifteen of these 16 occurrences were found to be the result of either a fuel pressure issue, propeller imbalance, or faulty electrical connection in the propeller governor and the cause of one was not found.
One additional event occurred in 2019, which was traced to excessive play in the alternator rotor. This was fixed by replacement of the alternator.
The reason for the fluctuations was found in all but three of the total of 19 reported occurrences.
Cylinder head cracking
On 25 May 2018, another DA40 NG aircraft in the AIAC fleet, VH-YPJ, had an occurrence where the engine coolant system over-pressurised and the coolant leaked. Inspection of that aircraft found cracking in six of the eight pairs of cylinder valve openings on the cylinder head.
Inspections were then carried out on the remaining aircraft in the operator’s fleet of five DA40 NG aircraft. The findings of the inspections are summarised in Table 1. The time between overhaul for the cylinder head was 1,800 hours.
Table 1: Cylinder head cracking in AIAC DA40 NG fleet
Aircraft
Cracking
Hours in service
VH-YPH
5 of 8 cylinder valves and cylinder head
1,358
VH-YPR
5 of 8 cylinder valves and cylinder head
1,409
VH-YPF
Cylinder head
1,356
VH-YPN
Cylinder head
1,555
VH-YPJ
6 of 8 cylinder valves and cylinder head
1,549
VH-YPQ
Cylinder head
901
Source: AIAC
After the accident and under the supervision of the ATSB, the operator examined the cylinder head fitted to VH-YPQ. Hairline cracks were identified in the cylinder head in the same location as VH-YPJ (Figure 7), however those cracks were assessed as insufficient in size to create engine problems at the time of the accident.
Figure 7: Cylinder cracks in VH-YPQ and another aircraft
The aircraft experienced propeller speed fluctuations shortly after take-off, which although relatively small, the instructor had not experienced previously. The feel, sound and fluctuating engine indications were interpreted by the instructor as a partial power loss. The instructor considered landing ahead as for a complete engine failure. However, due to darkness, obstacles in the path, the aircraft position and the perceived power available, the instructor decided to turn back to the runway.
During the 10 seconds that the instructor was assessing and decision-making prior to commencing the turn, the airspeed decreased 6 knots due to the aircraft’s nose-up pitch attitude. At the same time as commencing the turn, the instructor reduced engine power, while maintaining a nose-up attitude.
Following the power reduction, the combination of nose-up pitch attitude and increasing angle of bank, resulted in an aerodynamic stall. The instructor recognised the signs of the impending stall and knew it was necessary to lower the aircraft nose to recover but did not do so due to the perceived proximity of the trees below. This resulted in the loss of aircraft control and collision with terrain.
In-flight performance testing of a DA40 NG aircraft demonstrated that 30 per cent power was sufficient to maintain level flight including in a turn. Therefore, in this occurrence, had adequate airspeed above the stalling speed been achieved and maintained by lowering the aircraft’s nose, it was likely aircraft control would have been retained, even following the power reduction commanded by the instructor.
Managing a perceived partial power loss
Although the engine did not sustain a partial power loss, the instructor perceived that there was an impending engine issue due to the noise and vibrations brought on by the propeller fluctuations. Therefore, the instructor managed the issue by dealing with it as a partial power loss. However, the instructor could not recall reducing the power at the same time as commencing the turn, or why.
Managing partial power loss after take-off in single-engine aircraft was not included in the units of competency within the Civil Aviation Safety Regulations Part 61 Manual of Standards (MOS) or the aircraft operator’s training syllabus, other than as ‘underpinning knowledge’. The instructor had previously demonstrated competence in managing simulated complete engine failure after take-off in single-engine and multi-engine aircraft and in managing simulated partial engine failure in multi-engine aircraft. The instructor was also required to have demonstrated competence in recovery from a stall with full or partial loss of engine power in accordance with the MOS.
Training for complete engine failure after take-off is straightforward and the trained response is primarily to lower the aircraft nose to achieve a safe airspeed and land ahead. Training for partial power loss is more complex as there can be significant variation in the power loss presentation. This includes anything from almost full to almost no power available, and the situation may resolve, worsen, or both. Following a partial power loss, a pilot will need to make an assessment of the power available, aircraft performance, suitable landing areas and other factors such obstacles and terrain. It may be that turning back to land on a runway is achievable. In any event, the first memory item stipulated in the aircraft’s quick reference handbook in case of full or partial engine power loss, was to achieve the stated (best glide) airspeed, which is essential to avoid a loss of control.
Research conducted for the ATSB publication Avoidable Accidents No. 3 – Managing partial power loss after take-off in single-engine aircraft, found proportionally more fatal accidents occurred following a partial power loss than a complete engine failure. In particular, loss of aircraft control occurred more often following a partial power loss, either during a turn back to the runway or as a result of pilot inaction to prevent airspeed decay. The consequences of these loss of control occurrences were more serious than landing ahead following a complete engine failure. The research identified that pilots generally used a take-off safety briefing that primed them for actions in case of complete engine failure after take-off but not for partial power loss.
The instructor’s take-off safety briefing was consistent with that used across the general aviation industry and included instructions (paraphrased):
In case of engine failure when airborne with no runway remaining, lower the nose to achieve best glide speed and land ahead.
As lowering the aircraft nose when close to the ground is counterintuitive, such priming may help the pilot resist pitching the nose up, thereby avoiding a stall and loss of control. However, in this occurrence, the instructor commenced the turn before lowering the aircraft nose to achieve a safe speed, and although knowing it was necessary to lower the nose, did not want to direct the aircraft towards the trees below.
In the Avoidable accidents publication, the ATSB assessed that including consideration of partial power loss in the take-off safety briefing by reminding the pilot to lower the nose to achieve best glide speed before assessing performance and decision-making, may improve outcomes following (actual or perceived) partial power loss after take-off.
Cylinder head cracking
While not contributing to this accident, engine cylinder head cracking in the aircraft operator’s fleet of DA40 NG aircraft had occurred before the service life of 1,800 hours was exceeded. A crack in an engine cylinder head may develop to a size that results in loss of compression or power, foreign object damage or engine failure.
Findings
From the evidence available, the following findings are made with respect to the collision with terrain involving Diamond DA40 aircraft, registered VH-YPQ, 1 km south of Port Macquarie Airport, New South Wales, on 8 September 2017. These findings should not be read as apportioning blame or liability to any particular organisation or individual.
Contributing factors
In response to increasing propeller speed fluctuations which were interpreted as a partial power loss, the instructor decided to attempt to turn back to land at the aerodrome. The instructor reduced power to 30 per cent and did not maintain adequate airspeed during the turn, resulting in an aerodynamic stall, a loss of control and collision with terrain.
Other factors that increased risk
The aircraft manufacturer could not determine the reason for the fluctuations. Propeller speed fluctuations have occurred in other aircraft with the E4 engine and MTV-6-R propeller, and either resolved without pilot input or by moving the power lever.
Cylinder heads for the aircraft type were cracking prior to reaching their service life.
Safety issues and actions
Additional safety actions
Whether or not the ATSB identifies safety issues in the course of an investigation, relevant organisations may proactively initiate safety action in order to reduce their safety risk. The ATSB has been advised of the following proactive safety action in response to this occurrence.
Australian International Aviation College
The aircraft operator, Australian International Aviation College, reported to the ATSB that after the accident, they:
added the following to their required take-off safety briefing:
In the event of a partial power loss, set partial power safety speed (DA40 NG – 78 kt take-off flap or 88 kt flap up), assess performance. If unable to maintain altitude find suitable place to conduct a forced landing.
conducted partial engine failure after take-off training for instructors and students, comprising pre-flight planning and self-briefing, ground training, and flight training
performed flight simulator tests for partial engine failure after take-off conditions in each single engine aircraft model operated by the flying school to assess the power required to maintain altitude.
Pilot details
Pilot details – Instructor
Licence details:
Commercial Pilot (Aeroplane) Licence, issued November 2015
Aircraft ratings and endorsements:
Manual Propeller Pitch Control; Retractable Undercarriage; Single Engine Aeroplanes less than 5,700 kg Maximum Take-off Weight; Multi Engine Aeroplanes
Ratings:
Multi Engine Aircraft Instrument rating; Instrument Approach 2 Dimensional and 3 Dimensional; Flight Instructor Rating Aeroplane Grade 2, Single Engine Aircraft, Night VFR Training, Design Feature Training, Instrument Rating Training
Medical certificate:
Class 1, valid to March 2018
Aeronautical experience:
1160.9 hours
Last flight review:
June 2017
Pilot details – Student
Licence details:
Recreational Pilot Licence, issued May 2017
Endorsements:
Nil
Ratings:
Nil
Medical certificate:
Unknown
Aeronautical experience:
85.4 hours flying time, of which 19.8 were as pilot in command.
Last flight review:
N/A
Sources and submissions
Sources of information
The sources of information during the investigation included the:
instructor
student
flight training school/aircraft operator
aircraft and engine manufacturer
Civil Aviation Safety Authority
Airservices Australia
Bureau of Meteorology.
References
Orasanu, J., 2010, Flight Crew Decision-Making, in Kanki, B., Helmreich, R. and Anca, J., Crew Resource Management, Elsevier, San Diego, USA
Submissions
Under Part 4, Division 2 (Investigation Reports), Section 26 of the Transport Safety Investigation Act 2003 (the Act), the Australian Transport Safety Bureau (ATSB) may provide a draft report, on a confidential basis, to any person whom the ATSB considers appropriate. Section 26 (1) (a) of the Act allows a person receiving a draft report to make submissions to the ATSB about the draft report.
A draft of this report was provided to the aircraft operator, manufacturer and maintainer, the engine and propeller manufacturers, instructor and student pilot, the Civil Aviation Safety Authority, Austrian Federal Safety Investigation Authority and the German Federal Bureau of Aircraft Accident Investigation.
Submissions were received from the aircraft manufacturer, operator and maintainer, the Civil Aviation Safety Authority, Austrian Federal Safety Investigation Authority and the instructor. The submissions were reviewed and, where considered appropriate, the text of the report was amended accordingly.
Purpose of safety investigations
The objective of a safety investigation is to enhance transport safety. This is done through:
identifying safety issues and facilitating safety action to address those issues
providing information about occurrences and their associated safety factors to facilitate learning within the transport industry.
It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action.
Terminology
An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue.
Publishing information
Released in accordance with section 25 of the Transport Safety Investigation Act 2003
Ownership of intellectual property rights in this publication
Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia.
Creative Commons licence
With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence.
Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work.
The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau
Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.
Preliminary report
Report release date: 02/11/2017
This preliminary report details factual information established in the investigation’s early evidence collection phase and has been prepared to provide timely information to the industry and public. Preliminary reports contain no analysis or findings, which will be detailed in the investigation’s final report. The information contained in this preliminary report is released in accordance with section 25 of the Transport Safety Investigation Act 2003.
Sequence of events
On the evening of 8 September 2017, an instructor and student were preparing to carry out night circuits at Port Macquarie Airport, Port Macquarie, New South Wales in a Diamond DA40 NG aircraft, registered VH-YPQ. The training flight was being operated by the Australian International Aviation College. As it would be the student’s first time conducting night circuits, the instructor was at the controls for the first take-off, which began at about 1957 EST from runway 21.
The instructor reported noticing a ‘surging’ sound and feel on initial climb towards the end of the runway (Figure 1) and felt as though the engine had lost a significant amount of power. The propeller speed and load instruments were showing oscillations. As there was insufficient time for troubleshooting, and no visible forced landing options in the immediate area, the instructor decided to turn left and attempt to land on the reciprocal of the take-off runway, making an immediate radio call to that effect. The instructor recalled pushing the power lever to ensure that it was fully forward, and possibly experimenting with power settings to see if the issue improved.
Figure 1: Aircraft flight path and key events
Times shown in this image are Universal Coordinated Time (UTC). Local time was UTC + 10. Source: Google Earth, annotated by the ATSB based on-board recordings (Garmin and ECU), radio recording, and accident site assessment.
The instructor later reported the aircraft would not maintain height through the turn and it collided with trees about 325 m directly abeam the runway 21 departure threshold, coming to rest inverted (Figure 2). Both occupants were seriously injured and the aircraft was destroyed. There was no fire.
Figure 2: Wreckage of VH-YPQ, which was partially disturbed during the rescue
Source: ATSB
Aircraft information
The DA 40 NG is a four-seat, low-wing, T-tail aircraft. VH-YPQ was manufactured in 2015 and first registered in Australia in January 2016. It was fitted with an Austro Engine AE300 E4-A four-cylinder intercooled turbodiesel engine running on aviation turbine fuel. The engine drove a three-bladed wooden composite variable-pitch MT Propellers MTV-6-R propeller.
The AE300 engine’s fuelling and the propeller pitch are controlled by a single engine control unit (ECU) which has dual-redundant hardware and performs continual self-testing. There is a cockpit switch for selecting ECU channels in case of a fault. The engine is controlled with a single power demand lever with two separate channels into the ECU for fault detection.
The last maintenance carried out on the aircraft was a 50-hourly engine check, landing gear wheel replacement, and coolant relief valve replacement on 28 August 2017. The last major inspection was carried out on 8 August 2017.
The operator’s flight manual for the DA 40 NG, based on that provided by the aircraft manufacturer, had an emergency procedure for a defective propeller RPM regulating system (Figure 3). It stated that in the case of oscillating RPM, pilots should move the power lever to clear the problem.
Figure 3: Operator’s procedure for a defective propeller RPM regulating system
Source: Australian International Aviation College
Recorded data
Recorded data was retrieved from the ECU and the Garmin G1000 navigation/display system. The data closely matched between the two ECU channels and the Garmin G1000.
The engine data showed oscillations in propeller speed and engine load that began at a height of around 110 ft and increased over the next 20 seconds (Figure 4). By that time the propeller speed was varying between 2,206 and 2,279 RPM and load was varying by about 2.5 per cent.
Figure 4: Selected engine parameters for take-off showing propeller RPM (dark blue) and engine load (purple) oscillations. Other parameters shown are power lever position (light blue), boost pressure (red), ambient air pressure (dark green), engine oil pressure (light green), and engine status data (orange).
Image shows increasing oscillations in propeller RPM and engine load, followed by a sequence of power lever movements. RPM and load vary with power lever movement.
Source: Austro Engine
The data presented in Figure 4 shows variations in power lever position following oscillations in propeller RPM and engine load. The movements were accompanied by a reduction in engine load and propeller speed. Full power was then applied and maintained until at least the end of the recording 4 seconds later. It was not clear whether any oscillations occurred after the initial power reduction. The last few seconds of engine data, below about 100 ft height, were lost due to the impact affecting the recording.
No ECU faults were recorded. The engine manufacturer reported that, other than the oscillations in propeller speed and engine load, which were not the result of power lever movement, no signs of engine problems were recorded throughout the flight.
The Garmin G1000 GPS data showed the aircraft banked left at about the same time as the power was reduced, with airspeed then decreasing to about 59 kt. The aircraft reached a height of about 431 ft above ground level before descending in a left turn, with the last recorded bank angle at 30°. Based on alignment between the accident site location, direction of travel, and the recorded data, the left turn and steep descent continued to impact. About 12 seconds of data were lost as a result of the impact.
Accident site examination
Examination of the aircraft wreckage found no pre-existing airframe issues. The aircraft impacted terrain in a northerly direction at a relatively slow speed and steep (about 20°) angle of descent. The cockpit was partially collapsed with the airframe resting on the instrument panel and seat backs. Both wings and the tail were structurally detached during the impact sequence.
The flap actuator was found in the take-off flap position. The aircraft’s fuel tanks were breached and there was evidence of spillage, although the fuel quantity could not be determined. A small quantity of fuel was drained from the tanks and matched the characteristics of aviation turbine fuel. It tested negative to water content. Previous fuel records and the engine data both indicated that there was sufficient fuel on board the aircraft.
Weather and environmental information
The weather was fine with light winds and little to no cloud. The time of the occurrence was past astronomical twilight and the moon, although nearly full, was on the horizon and would not have provided any significant light.
The departure end of runway 21 was surrounded by scrub and swamp. The township of Port Macquarie provided some light and a horizon reference to the east but the ground near the airport was dark apart from a few scattered dwellings.
Related occurrences
The engine manufacturer reported it was aware of 16 other events on aircraft fitted with the AE300 engine worldwide involving oscillations in propeller speed and load, none of which resulted in an accident. The engine manufacturer reported that in all cases, oscillations ceased with a change in power lever position.
Fifteen of these occurrences were later found to be the result of a fuel pressure issue, propeller imbalance, or faulty electrical connection in the propeller governor. Limited data from one occurrence of each type were provided by the engine manufacturer and exhibited different data signatures than that seen in the VH-YPQ accident.
The other occurrence involved a Diamond DA42, a twin-engine aircraft with a similar engine type to VH-YPQ. The reasons for that oscillation could not be determined from post-event examinations.
While acknowledging the difficulty of attempting to train pilots for a partial power loss event which has an almost infinite variability of residual power and reliability, analysis of the occurrences supports the need to raise greater awareness of the hazards associated with partial power loss and to better train pilots for this eventuality… Partial power loss occurrences have a very broad range of characteristics by nature. The most effective risk control method for managing these occurrences may be significantly different between pilots of varying experience and training, aircraft models and the environmental conditions.
Pilots and operators can significantly reduce risk following a partial or complete engine power loss using the following strategies:
Pre-flight decision making and planning for emergencies specific to the current location and conditions, taking into account the runway direction and the best direction of any turn, the local wind strength and direction on a particular day, terrain and obstacles, decision points (taking into account aircraft height and performance) where different landing options will be taken.
Taking positive action and maintaining aircraft control when turning back to the aerodrome or conducting a forced landing.
Safety actions
After the accident, the Australian International Aviation College:
introduced partial engine failure after take-off training into the syllabi for instructors and students, comprising pre-flight planning and self-briefing, ground training, and flight training
performed flight simulator tests for partial engine failure after take-off conditions in each single engine aircraft model operated by the flying school
amended procedures to ensure that pilots keep a hand on the power lever throughout the take-off
investigated the potential to introduce specific single engine escape procedures for partial and complete power loss situations for each runway regularly used by the flying school.
Continuing investigation
The investigation is continuing and will include further examination and analysis of the:
recorded data
propeller hub, governor, and engine control unit
aircraft maintenance documentation
weather conditions
pilot qualifications and experience
coordination and planning of the training flight
aircraft and flying school operational procedures
related occurrences.
____________________ The information contained in this web update is released in accordance with section 25 of the Transport Safety Investigation Act 2003 and is derived from the initial investigation of the occurrence. Readers are cautioned that new evidence will become available as the investigation progresses that will enhance the ATSB's understanding of the accident as outlined in this web update. As such, no analysis or findings are included in this update.
Purpose of safety investigations
The objective of a safety investigation is to enhance transport safety. This is done through:
identifying safety issues and facilitating safety action to address those issues
providing information about occurrences and their associated safety factors to facilitate learning within the transport industry.
It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action.
Terminology
An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue.
Publishing information
Released in accordance with section 25 of the Transport Safety Investigation Act 2003
Ownership of intellectual property rights in this publication
Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia.
Creative Commons licence
With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence.
Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work.
The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau
Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.
At 1136, on 12 August 2017, The Airplane Factory Sling 4 amateur-built aircraft, registered VH-BEG, departed Caloundra Aerodrome, Queensland, for a local private flight. There was a pilot and three passengers on board.
At 1143, the flight returned to Caloundra. Pilots of other aircraft reported that at the time wind conditions were light and aligned with runway 05.
The pilot positioned the aircraft to join the circuit for runway 12. The pilot of another aircraft advised runway 05 was in use and the pilot of VH-BEG then manoeuvred the aircraft to join the circuit for runway 05. While on the final leg of the circuit, the pilot selected full flap and observed parachutists descending to the right of the runway 05 threshold.
As the aircraft approached the runway, the pilot became concerned that the parachutists might drift into the path of the aircraft and focussed on the location of the parachutists. He then detected that the aircraft had deviated above and to the right of the desired approach path. The pilot then reduced power to idle and commenced a forward slip[1] to attempt to increase the approach angle and regain the desired approach path. As the aircraft approached the runway 05 threshold, he stopped the forward slip and began a left turn toward the threshold.
During the left turn, the aircraft aerodynamically stalled and the aircraft rolled to the left. Almost immediately, the left wing tip struck the ground and the aircraft collided with terrain. The fuselage fractured at the engine firewall, the engine was pushed rearward and intruded into the cabin.
The aircraft came to rest inverted and was destroyed (Figure 1). The pilot and all three passengers suffered serious injuries.
The figure shows the wreckage of VH-BEG after emergency services had attended. Source: Queensland Police
Video footage
Video footage taken by the passenger in the left rear seat captured the final eight seconds of the flight.
The footage showed the aircraft in a forward slip with the nose yawed[2] to the right and tracking parallel to, but right of, the runway extended centreline (Figure 2). The indicated airspeed was 58 kt,[3] and the tachometer indicated idle power. The forward slip then stopped and the aircraft turned left toward the runway threshold. At the same time, the descent rate increased.
Figure 2: Images from video footage
The figure shows images of the aircraft during the approach prior to the accident. The aircraft is shown in a forward slip (left) and at the beginning of the turn toward the runway 05 threshold (right). Source: Passenger, annotated by ATSB
The aircraft approached the runway threshold on a heading of about 010 degrees magnetic, and appeared to be undershooting the threshold. Pitch angle then increased, an aerodynamic stall occurred, and the aircraft rolled rapidly left. As the aircraft rolled, the slip indicator displayed a full right deflection, indicating that the aircraft had entered an incipient left spin. The footage stopped as the left wing impacted the ground.
Pilot comments
The pilot of the aircraft provided the following comments:
The pilot reported calculating the weight and balance of the aircraft prior to the flight using the aircraft electronic flight instrumentation system (EFIS) and using average weights for all occupants. He recalled the EFIS showing the aircraft weight and balance to be within the approved range.
He did not consider conducting a go-around.
The aircraft was fitted with a stall warning system, however, this did not activate prior to the accident.
Aircraft weight and balance
Weight and balance limitations were contained in the aircraft’s Pilot’s Operating Handbook (POH). The limitations defined the gross weight and centre of gravity limits. The maximum take-off weight of the aircraft was 920 kg and the aircraft was fitted with four seats.
The limits of the permissible centre of gravity range were defined as a percentage of mean aerodynamic cord (MAC):[4]
The forward limit of the permissible range was 18 per cent MAC up to a gross weight of 840 kg, above this weight, the forward limit was 24 per cent MAC.
The rear limit of the permissible range was 28 per cent MAC up to a gross weight of 700 kg, above this weight, the rear limit was 31 per cent MAC.
The empty weight of the aircraft was 461 kg. The weight of the front seat occupants was 190 kg and the weight of the rear seat occupants was 175 kg. The pilot estimated that at the time of take-off there was about 93 kg of fuel on board and reported that no items were carried in the baggage compartment.
Based on the above weights, the estimated take-off weight for the accident flight was 919 kg. The take-off centre of gravity position was 33.1 per cent MAC, and the zero fuel weight[5] centre of gravity position was 35.7 per cent MAC.
The centre of gravity position was outside of the permissible range for the entire flight (Figure 3).
Figure 3: Graphical representation of the aircraft centre of gravity for the accident flight
The graph shows the permissible centre of gravity range along with the calculated take-off and zero fuel weight centre of gravity positions. Source: Aircraft manufacturer, modified and annotated by ATSB
The pilot reported calculating the weight and balance to be within the permissible range using average weights.
The Civil Aviation Safety Authority advisory publication CAAP 235-1(1) Standard passenger and baggage weights provides the following guidance for using standard, or average, weights when calculating aircraft weight and balance:
Standard weights should not be used in aircraft with less than seven seats.
Because the probability of overloading a small aircraft is high if standard weights are used, the use of standard weights in aircraft with less than seven seats is inadvisable. Load calculations for these aircraft should be made using actual weights arrived at by weighing all occupants and baggage.
The New Zealand Civil Aviation Authority publication Weight and Balance contains the following information regarding the effects of operating an aircraft outside of the rear centre of gravity limit:
Your aircraft has centre of gravity limits, and any loading that puts the centre of gravity outside of those limits will seriously impair your ability to control the aircraft. The more aft the centre of gravity, the more unstable the aircraft. Forward pressure on the elevator control and full nose-down trim may be necessary to keep the aircraft from pitching up and stalling.
The further aft the centre of gravity is, the harder it is to recover from a stall.
ATSB comments
VH-BEG loading
Using the weight of the front seat occupants from the accident flight and allowing for no fuel and no baggage, the ATSB calculated that the maximum weight able to be carried in the rear seats of VH-BEG, while remaining within the allowable centre of gravity range, was just 118 kg. Using 105 kg of fuel as ballast, this weight increased to 148 kg. This allowed for 15 minutes of flight fuel and a 45-minute fuel reserve to be carried within the 920 kg maximum allowable take-off weight.
It was also found that when allowing for full fuel and any weight in the front two seats, the aircraft also required weight in the rear seats, or the baggage compartment, to ensure the centre of gravity was not located forward of the allowable range.
Warnings regarding weight and balance limitations included in the Sling 4 POH are shown in Figure 4:[6]
Figure 4: Warnings contained in POH
The figure shows warnings contained within the Sling 4 POH. Source: Aircraft manufacturer
Amateur-built aircraft regulations allow for some variance in construction which can lead to differences in the longitudinal balance and loading of individual aircraft. Pilots of amateur-built aircraft are reminded to be familiar with the weight and balance capabilities and limitations of their aircraft.
The weight and balance calculation blank form on page 6-13 lists the location of the front seats as 1959mm aft of the datum. The correct figure is 1902mm, as detailed on page 6-4.
The pilot did not use the POH to calculate the weight and balance, therefore the error did not contribute to the accident. However, pilots of Sling 4 aircraft should ensure that weight and balance calculations are conducted using the correct figure.
Safety analysis
The flight was conducted with the centre of gravity aft of the rear limit. This had the effect of making the aircraft less stable and more susceptible to an aerodynamic stall. This also made recovery from a stall more difficult.
After detecting that the aircraft had deviated from the desired flight path, the pilot attempted to continue the approach by manoeuvring the aircraft at low level and low speed. The aircraft was loaded outside of the permissible centre of gravity range, and the manoeuvring further reduced the remaining margins of controllable flight until the aircraft stalled and control was lost.
During the manoeuvring, the aircraft stalled and entered an incipient spin. The stall and incipient spin occurred at a height from which recovery was not possible and the aircraft collided with terrain.
Findings
These findings should not be read as apportioning blame or liability to any particular organisation or individual.
The aircraft centre of gravity position was aft of the rear limit.
During the approach, the aircraft stalled and entered an incipient spin at a height from which recovery was not possible and the aircraft collided with terrain.
Safety action
Whether or not the ATSB identifies safety issues in the course of an investigation, relevant organisations may proactively initiate safety action in order to reduce their safety risk. The ATSB has been advised of the following proactive safety action in response to this occurrence:
Aircraft manufacturer
As a result of this occurrence, the aircraft operator has advised the ATSB that they are taking the following safety action:
Change to documentation
The position of the front seats in the blank form on page 6-13 of the Sling 4 Pilot’s Operating Handbook, version 1.6 will be corrected to show 1902mm aft of the datum.
Safety message
This incident highlights the critical importance of operating an aircraft within prescribed limitations at all times.
After detecting that the aircraft had deviated from the desired approach path, the pilot did not conduct a go-around. While the aircraft centre of gravity was located outside of the permissible range, a go-around, rather than manoeuvring at low speed and low level, may have prevented the accident from occurring.
The Flight Safety Foundation Approach-and-landing accident reduction tool kit Briefing note 6.1 – Being prepared to go around, stated that the importance of being go-around-prepared and go-around-minded must be emphasised because a go-around is not a frequent occurrence.
Purpose of safety investigations
The objective of a safety investigation is to enhance transport safety. This is done through:
identifying safety issues and facilitating safety action to address those issues
providing information about occurrences and their associated safety factors to facilitate learning within the transport industry.
It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action.
Terminology
An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue.
Publishing information
Released in accordance with section 25 of the Transport Safety Investigation Act 2003
Ownership of intellectual property rights in this publication
Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia.
Creative Commons licence
With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence.
Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work.
The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau
Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.
On 15 August 2017, the pilot of a Robinson R44 helicopter, registered VH-HBV (HBV), conducted a private ferry flight from Cooktown to Mossman, Queensland. After refuelling in Mossman, the helicopter departed for a short ferry flight to Julatten, Queensland. The pilot was the sole occupant of the helicopter.
At about 1520 Eastern Standard Time,[1] the helicopter approached the landing site in a northerly direction. The pilot conducted an orbit at about 300–500 ft above the site to assess the conditions and then commenced the approach.
Just prior to touchdown, the pilot pulled back on the cyclic.[2] As a result, the tail rotor struck the ground behind the helicopter. The pilot felt the tail contact the ground through the airframe and pedals. The helicopter shuddered violently and yawed[3] rapidly to the right.
As the helicopter completed a 360 degree turn with the skids about 3–5 ft above the ground, the pilot lowered the collective[4] in an attempt to land on the helipad. The helicopter was still yawing as the skids contacted the helipad. It rolled over, the main rotor blades struck the ground and the helicopter came to rest on its left side.
The pilot was uninjured, and the helicopter sustained substantial damage (Figure 1).
Figure 1: Accident site showing damage to VH-HBV
Source: CASA
Pilot comments
The pilot commented that there were trees along the approach to the landing site, but it did not require a steep approach path and consequently he conducted a shallow approach. The wind at the time was from the south-east at 10 to 15 kt, but, due to the sheltered location, there was no wind at the landing site.
A company helicopter had landed shortly before HBV, and was parked on the front of the pad. The pilot commented that he may have looked at that helicopter as he touched down, which led to pulling back on the cyclic. HBV was an older model R44 helicopter than the pilot had flown previously and he reported that when the cyclic was in the neutral position, it sat slightly further forward than he was accustomed to. The pilot also commented that had he rolled off the throttle immediately after the tail rotor struck the ground, it would have reduced the helicopter’s rate of rotation and potentially prevented the rollover. He stated, however, that he did not recognise the developing situation, and roll off the throttle, before the helicopter began yawing. He also reported being unable to land the helicopter until it had rotated through 360° due to concern about terrain contact. Finally, the pilot recalled that he rolled off the throttle upon lowering the collective but the yaw did not stop completely prior to the skids contacting the ground.
The chief pilot, who witnessed the accident, indicated that the helicopter came in with the tail a bit lower than normal, the tail rotor struck a small mound of dirt, and the tail rotor and gear box detached. He commented that the pilot only weighed about 65 to 70 kg and, without any passengers or gear on board, the centre of gravity of the R44 is quite aft and the tail is therefore lower than when more heavily loaded. He further stated that the fuel tank was about three-quarters full, and the helicopter was within weight and balance limitations.
Safety analysis
The pilot applied aft cyclic just prior to touchdown, which resulted in a slightly tail-low attitude for landing. The tail stinger would normally contact the ground and prevent a tail rotor strike. However, because the ground sloped away behind the concrete landing pad, the stinger was over the slope, allowing the tail rotor to strike the ground and detach without prior warning (Figure 2).
Following separation of the tail rotor and gearbox, the helicopter yawed rapidly to the right through 360° in response to the torque associated with the still‑powered main rotor. As the pilot did not roll the throttle off quickly enough to reduce the rate of yaw of the helicopter prior to lowering the collective, the helicopter was still yawing when the skids contacted the ground. Consequently, it rolled over and the main rotor blades struck the ground.
Figure 2: Sloping ground away from helipad and tail rotor strike marks
Source: Queensland Police
Findings
These findings should not be read as apportioning blame or liability to any particular organisation or individual.
The pilot applied aft cyclic just prior to touchdown, resulting in a tail-low attitude.
The ground sloped downwards away from the landing pad and as a result, the tail stinger did not protect the tail rotor from ground contact.
The tail rotor struck the ground and detached, resulting in the helicopter yawing rapidly to the right. The pilot did not roll off throttle to reduce the yaw rate prior to lowering the collective, which probably led to the helicopter rolling over as the skids contacted the ground.
Safety action
Whether or not the ATSB identifies safety issues in the course of an investigation, relevant organisations may proactively initiate safety action in order to reduce their safety risk. The ATSB has been advised of the following safety action in response to this occurrence.
Helicopter operator
As a result of this occurrence, the helicopter operator has taken the following safety actions:
Company pilots were briefed immediately following the accident, and subsequently trained, with regard to flying alone or with very little cargo. R44s are inclined to have a nose-high attitude when light, which often results in tail and stinger encroaching too close to terrain.
The company hazard register was updated to highlight the issue and company pilots were required to read the updated register. Pilots were advised that higher flare and slower approaches can mitigate the hazard.
Company pilots were briefed regarding hazards associated with helicopter landing sites and bush landing sites with sloping terrain and any obstacle that may come into contact with tail rotor or helicopter.
Retraining of company pilots in special procedures, including the conduct of hovering autorotations was conducted between October and November 2017. The operator assessed that use of this technique would have reduced the damage to the helicopter.
Safety message
This occurrence highlights that a loss of tail rotor thrust at low speed and low height above the ground requires an immediate and correct response to maintain control of the helicopter. It is therefore important that pilots are primed for this emergency, particularly during the approach and departure phases of flight.
The United States National Transportation Safety Board Safety Alert Loss of tail rotor effectiveness in helicopters states that due to safety concerns, training for loss of tail rotor effectiveness (LTE) is rarely conducted in an actual helicopter. While this incident involved the detachment of the tail rotor rather than aerodynamic LTE, the stated pilot responses to LTE are applicable here and consistent with the manufacturer’s emergency procedures.
The US Federal Aviation Authority Advisory Circular 90-95 stated under effective recovery techniques (for LTE), that collective pitch reduction will aid in arresting yaw rate but may cause an increase in the rate of descent. If the rotation cannot be stopped and ground contact is imminent, an autorotation (i.e. rolling off throttle) may be the best course of action. While the pilot’s action in lowering the collective during this occurrence may have reduced the yaw rate, following the manufacturer’s emergency procedure for a loss of tail rotor thrust during hover will provide the best outcome when close to the ground. That is, if uncommanded yaw is experienced that cannot be stopped by application of opposing tail rotor pedal:
fully roll off the throttle and allow the helicopter to settle while controlling any drift
raise the collective just before touchdown to cushion the landing.
About this report
Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, a limited-scope, fact-gathering investigation was conducted in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.
Publishing information
Released in accordance with section 25 of the Transport Safety Investigation Act 2003
Ownership of intellectual property rights in this publication
Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia.
Creative Commons licence
With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence.
Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work.
The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau
Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.
At about 1615 Eastern Standard Time (EST), on 8 August 2017, the Aerodrome Reporting Officer (ARO) of Middlemount Airport, Queensland, inspected the runway prior to the arrival of two aircraft. The ARO found no abnormalities with the runway or runway lighting.
The first aircraft was an Embraer EMB-135LR, registered VH-JGB, operated by JetGo Australia as a charter flight from Brisbane, Queensland. On board the aircraft was a training captain, a captain under line training, a cabin crewmember and 23 passengers.
The captain under training had recently joined the aircraft operator. This was his second flight with the operator, and first to Middlemount. The flight was also his second flight on the aircraft type, having completed aircraft type training in a simulator.
During the flight, the flight crew reviewed the company briefing package for Middlemount and noted that the runway was not equipped with visual approach slope guidance.[1]
At 1643, the captain under training, acting as pilot flying,[2] positioned the aircraft on the downwind leg of the circuit for runway 11 at Middlemount. The flight crew elected to extend the downwind and final circuit legs beyond the standard length to allow the captain under training to familiarise himself with higher terrain to the north-west of the airport and radio masts in the vicinity of the runway 11 approach path. During the final approach leg, the training captain observed that the aircraft appeared to be slightly below the desired approach profile but determined that it did not require him to take corrective action.
At 1647, the aircraft landed on runway 11. The flight crew did not detect anything abnormal during the landing. The ARO observed the landing and noted that the aircraft appeared to touchdown early. The aircraft then taxied to parking normally.
A runway inspection was not carried out prior to the arrival of the second scheduled flight. The second flight arrived without incident, the ARO noted that the touchdown point for this flight appeared to be in the normal touchdown zone (Figure 1).
Figure 1: Overview of runway 11 threshold
Image shows the positions of the beginning of the runway, runway threshold lights, aiming point markers and touchdown zone. Source: Google earth, annotate by ATSB
At about 1840, the ARO conducted an inspection of the runway prior to the departure of the two aircraft. During the inspection, the ARO identified two damaged runway threshold lights (Figure 2) and fresh tyre marks (Figure 3) about four meters further along the runway from the damaged lights. The ARO immediately proceeded to VH-JGB, and advised the flight crew that he believed they had damaged the runway threshold lights during their landing. The training captain inspected the aircraft tyres and landing gear and determined that the aircraft had not sustained any damage.
Figure 2: Damaged runway threshold lights
Images shows the damage to the runway threshold lights (left and centre), and a tyre mark on a damaged light (right). Source: Airport operator, annotated by ATSB
At about 1935, the ARO cleared the debris and determined the runway to be serviceable.
At 1954, VH-JGB departed runway 11 at Middlemount for Brisbane. After the aircraft arrived at Brisbane, an engineering inspection of the aircraft found no damage.
No persons were injured, and the aircraft was not damaged in the incident.
Figure 3: Runway 11 threshold
Image shows the damaged runway lights, touchdown tyre marks and runway light debris. Source: Airport operator, annotated by ATSB
Training captain comments
The training captain made the following comments:
Middlemount is the only airport the operator regularly serves which does not have visual approach slope guidance.
The selected touchdown aim point was the aiming point markers.
During the late stages of the approach, the demands of acting in the pilot monitoring role and monitoring the captain under training resulted in a very high workload.
Captain under training comments
The captain under training made the following comments:
In his previous role, the captain under training received extensive training and operational experience in conducting approaches without visual approach slope guidance. These operations were on the Beechcraft King Air 200 turboprop aircraft. He had extensive experience in jet aircraft. However, the incident flight was the first time he had conducted an approach without visual approach slope guidance in a jet aircraft.
The simulator training provided by the company included narrow runway operations and approaches without visual approach slope guidance. The captain under training also commented that he would have liked to have received more simulator training for visual approaches without slope guidance, and it would be beneficial if these types of approaches were conducted later in the line training phase.
While the approach appeared to be slightly lower than normal, as the aircraft descended through about 500 ft above ground level, the training captain called ‘stable’, indicating the approach was within tolerances. This reassured the captain under training that the approach was proceeding normally.
The demands of operating a new aircraft type, with new operating procedures, to a runway without visual approach slope guidance resulted in a very high workload during the approach.
Aerodrome reporting officer comments
The ARO made the following comments:
There was no defined procedure in place to conduct runway inspections. However, where possible, runway inspections were carried out before and after JetGo arrivals. The second flight arrived about 15 minutes after VH-JGB. The time period between the two arrivals did not allow for a runway inspection.
The ARO regularly observed JetGo arrivals and had a good understanding of the expected touchdown point.
Flight recorders
The aircraft was equipped with a flight data recorder which recorded the flight data associated with the occurrence.
Approach path
The flight data shows (Figure 4) that at 16:47:10, the aircraft was positioned on about a three-degree approach path. At this time, the descent angle increased until the aircraft flared for landing.
Figure 4: Graphical representation of recorded flight data
The data plot shows the main landing gear air/ground switch position, engine power, ground speed and pressure altitude. A representative three degree approach path and the landing are annotated. Source: ATSB
Touchdown point
The recorded touchdown point of the aircraft was consistent with the fresh tyre marks observed by the ARO.
Flight crew workload
The flight crew reported that during the approach they experienced a period of very high workload.
The flight crew also reported not detecting anything abnormal during the landing and first becoming aware of the incident when notified by the ARO.
Under conditions of stress, an individual’s attention will channel or tunnel. Focus on peripheral tasks will be reduced and centralized on to main tasks. What differentiates a main task from a peripheral task depends on what the individual perceives to be of greatest importance or greatest salience. Tunnelling of attention can result in either enhanced performance or reduced performance, depending on the nature of the task and the situation.
Aircraft operator report
The aircraft operator conducted an investigation into the incident and provided the following observations:
The flight crew felt no urgency to land the aircraft before the touchdown zone due to performance limitations. The calculated landing distance required was 1,306 m, and the landing distance available was 1,550 m.
During the landing flare, the captain under training reported having to raise his head to maintain visual contact with the runway and had difficulty in determining if the landing would be before the aim point. An incorrect seating position likely contributed to the collision with the runway lights.
Standard length downwind and final circuit legs, along with a correct seating position and corrective callouts by the training captain would have been more representative of the simulator training received by the captain under training.
Safety analysis
During final approach the aircraft descended below the final approach path, and the aircraft landed prior to the selected aim point. Prior to landing, the main landing gear tyres collided with two runway threshold lights.
This was the captain under training’s first approach without visual slope guidance in a jet aircraft. Combined with the demand of operating a new aircraft under new operating procedures, resulted in a high workload for the pilot under training during the approach. The training captain also experienced a high workload due to the demands of acting in the pilot monitoring role and monitoring the captain under training.
The high workload of the flight crew during the approach, along with the absence of approach slope guidance, likely reduced the flight crew’s ability to detect the flight path deviation.
Findings
These findings should not be read as apportioning blame or liability to any particular organisation or individual.
The aircraft descended below the desired approach path and landed prior to the selected aim point. Prior to landing, the aircraft collided with two runway threshold lights.
A flight involving a captain under line training, with high workload during final approach associated with the line training, along with the absence of approach slope guidance, resulted in the flight crew not detecting that the aircraft had descended below the desired approach path.
Safety actions
Whether or not the ATSB identifies safety issues in the course of an investigation, relevant organisations may proactively initiate safety action in order to reduce their safety risk. The ATSB has been advised of the following proactive safety action in response to this occurrence.
Aircraft operator
As a result of this occurrence, the aircraft operator has advised the ATSB that they are taking the following safety actions:
Changes to procedures
Landings at Middlemount will be made by captains only.
Line training flights will not operate to Middlemount.
Training for operations without approach slope guidance will be conducted as standalone training following a period of consolidation of line flying after the completion line training.
Flight crew education and training
Aircrew notices were circulated to all flight crew, providing education on operations without vertical profile guidance and Middlemount operations. The landing technique contained within the FCOM was amended to include addition information regarding runway visual illusions.
The flight crew involved in the incident underwent additional training in approaches without visual approach slope guidance prior to resuming operations to aerodromes without visual approach slope guidance.
Safety message
The ATSB has identified descending too low on approach as a risk area requiring heightened attention. When compared to other phases of flight, the approach and landing has a substantially increased workload and is traditionally the phase of flight associated with the highest accident rate. Flight crews must continuously monitor aircraft and approach parameters, and the external environment to ensure they maintain a stable approach profile and make appropriate decisions for a safe landing.
The impact of workload can be insidious, the affected individual not realising an increase until it has reached a high level. The best way of managing workload is to reduce the level of work demands and distractions. If the work demands cannot be reduced, then another option is to ensure the flight crew have the experience, skills and techniques to effectively manage their task demands. Overall, high workload can have significant effects on flight crew performance and needs to be monitored and managed using a systemic approach, particularly for less experienced flight crew, but also flight crew who have recently undertaken a new role.
Purpose of safety investigations
The objective of a safety investigation is to enhance transport safety. This is done through:
identifying safety issues and facilitating safety action to address those issues
providing information about occurrences and their associated safety factors to facilitate learning within the transport industry.
It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action.
Terminology
An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue.
Publishing information
Released in accordance with section 25 of the Transport Safety Investigation Act 2003
Ownership of intellectual property rights in this publication
Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia.
Creative Commons licence
With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence.
Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work.
The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau
Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.
Section 21 (2) of the Transport Safety Investigation Act 2003 (the Act) empowers the Australian Transport Safety Bureau (ATSB) to discontinue an investigation into a transport safety matter at any time. Section 21 (3) of the Act requires the ATSB to publish a statement setting out the reasons for discontinuing an investigation.
On 29 July 2017, the ATSB commenced an investigation into a collision with terrain involving a Zaklad Remontow I Produkeji Spreztu Lotnicz MDM-1P FOX-P glider, registered VH-GPT, at Lismore Airport, New South Wales.
The ATSB found that while conducting an aerobatic display, the glider impacted the ground heavily during the final manoeuvre. The pilot was seriously injured. Examination of the aircraft identified no mechanical issues or faults that may have contributed to the accident.
The ATSB has also reviewed the safety and administrative procedures necessary to conduct air shows and found that, in this case, preparations were consistent with regulatory requirements. The ATSB investigation AO-2017-013, Mallard aircraft, Perth, January 2017 is examining a range of issues associated with air shows, including the suitability of the regulations, approval and oversight of air shows, and compliance with regulatory approvals during air shows.
In this case, the ATSB did not identify any organisational or systemic issues that contributed to the development of the accident or that might adversely affect the future safety of aviation operations. The ATSB assessed that no safety issues would be identified through further investigation. On that basis, the ATSB will discontinue this investigation.
On 28 June 2017, the pilot of a SOCATA TB-10 Tobago aircraft, registered VH-YTM, was conducting a community service flight from Mount Gambier Airport, South Australia, to Adelaide, South Australia. The flight was organised by the charity Angel Flight to transport a passenger for medical treatment and an accompanying family member. The aircraft took off at 1020 Central Standard Time as a private flight operating under visual flight rules. After reaching a height of 300 ft, the aircraft descended and impacted terrain about 70 seconds after take-off. The pilot and both passengers were fatally injured, and the aircraft was destroyed.
What the ATSB found
The ATSB found that the pilot took off in low-level cloud without proficiency for flight in instrument meteorological conditions. Shortly after take-off, the pilot likely lost visual cues and probably became spatially disorientated, resulting in loss of control of the aircraft and collision with terrain.
The ATSB has previously established that the fatal accident rate of private operations is substantially higher than commercial passenger transport (eight times higher than charter and 27 times higher than low-capacity regular public transport, with no fatal accidents on high capacity RPT). This ATSB investigation further established that community service flights conducted on behalf of Angel Flight Australia (Angel Flight) had substantially more occurrences, accidents and fatal accidents per flight than other private operations (including that the fatal accident rate was more than seven times higher per flight than other private flights).
It is almost certain this higher occurrence rate is due to community service flights being exposed to different operational risk factors when compared to other private operations. The ATSB found two aspects in particular likely contributed to this higher rate. These were the potential for some pilots to experience perceived or self-induced pressure by taking on the responsibility to fly ill, unknown passengers, at scheduled times to meet predetermined medical appointments, often with an expected same day return; and the required operation to unfamiliar locations, and limited familiarity with procedures in controlled airspace (associated with larger aerodromes). These factors were consistent with lessons learned from the US experience, the occurrence data analysis of Angel Flight organised flights, and submissions made to a Civil Aviation Safety Authority (CASA) public consultation on changes to community service flights.
The types of occurrences where flights organised by Angel Flight were statistically over-represented (as a rate per flight) compared to other private operations were consistent with these operational differences. In particular, occurrences which involved pre- and in-flight planning and decision-making errors were over-represented, which was a factor in this accident as well as in a previous fatal accident in 2011 which involved an Angel Flight organised passenger flight. The higher occurrence rate in particular types of occurrences indicated an elevated and different risk profile in Angel Flight organised private community service flights compared with other private operations.
Angel Flight had insufficient controls in place, and provided inadequate guidance to pilots for addressing the additional operational risks associated with community service flights. Furthermore, the ATSB found that there were limited opportunities for Angel Flight to be made aware of any safety related information involving flights conducted on its behalf, restricting its ability to identify and manage organisational risks.
It was identified that Angel Flight did not consider the safety benefits of commercial flights when suitable flights were available. While Angel Flight arranged and paid for commercial flights (18 per cent of all flights) for capital city transfers, or when private pilots cancelled, it was estimated that nearly two-thirds of the private flights conducted for Angel Flight had a commercial regular public transport option available, which offered considerable safety benefits when compared to private operations. Of these, at least 22 per cent had suitable same day return flights four or five days a week, with at least two-thirds of these regular public transport flights being of comparable cost to Angel Flight when compared with the volunteer costs. The ATSB acknowledges that there will be passengers who cannot travel on regular public transport flights, and that there are times and locations where this option is not available or suitable. However, Angel Flight should still consider the use of suitable commercial flights as a primary option when arranging and paying for flights to assist financially disadvantaged people. On the day of the accident, suitable and cost-comparative commercial passenger flights were available.
CASA did not have a system to differentiate between community service flights and other private operations that would allow for ongoing oversight and review of the safety of these flights. Differentiation would allow for the identification of areas of specific concern through evidence-based analysis, and consideration of appropriate risk controls to be applied to all organisations offering community service flights. The lack of this differentiation limited CASA’s ability to identify and manage risks associated with community service flights.
What's been done as a result
Angel Flight Australia advised it had received permission for all registered pilots to access the community service pilot education online course Public Benefit Flying: Balancing safety and compassion, developed in the United States by the Aircraft Owners and Pilots Association Foundation’s Air Safety Institute, while an Australian course is developed. It also indicated it was facilitating the sharing of all CASA safety seminar schedules, with a request for feedback on attendance and the content presented, and engaging a volunteer to develop systems and processes to manage its safety risks. Additionally, pilot, passenger and health referrer guidelines had also been updated. The ATSB will monitor the progress of these safety actions.
The ATSB has issued a safety recommendation to Angel Flight Australia to take action to consider the safety benefits of using commercial flights where they are available to transport its passengers.
The ATSB was advised CASA had implemented a new safety standard regarding the conduct of community service flights. These requirements commenced on 19 March 2019 and included:
A flight notification (full flight notification or SARTIME) that identifies the flight as a community service flight to be submitted to Airservices Australia.
Pilots to annotate that the flight conducted was a community service flight in their personal logbook.
These changes will allow CASA to conduct ongoing identification and monitoring of risks associated with community service flights to be able to manage and control those risks.
CASA has also promoted its updated human factors education package to the industry broadly, including the community service flight sector, and refers to it on the community service flight landing page on its website. CASA also intends to release targeted guidance information to further assist the community service flight sector in the coming months.
Safety message
Organisations conducting community service flights and their pilots should be aware of the additional operational risks present. It is important that organisations have appropriate operational controls in place, and ensure pilots have access to guidance and education regarding the risks, to enable them to make objective decisions.
The occurrence
On 28 June 2017 at about 0800 Central Standard Time,[1] the pilot of a SOCATA TB-10 aircraft, registered VH-YTM (YTM), departed Murray Bridge Airport, South Australia (SA), for Mount Gambier Airport, SA. The charity Angel Flight Australia (Angel Flight) had arranged for the pilot to conduct a private flight for two passengers from Mount Gambier Airport at 1000, to facilitate the passengers’ access to specialist medical services in Adelaide, SA. Both trips were conducted as private flights under the visual flight rules (VFR).[2]
Position and altitude information obtained from OzRunways[3] showed that the aircraft initially tracked directly from Murray Bridge toward Mount Gambier, at an altitude of about 4,500 ft above mean sea level (AMSL). About 23 NM north-north-west of Mount Gambier Airport, the aircraft descended to approximately 1,000 ft AMSL and there was a significant deviation from the direct route (Figure 1).
Figure 1: Track of VH-YTM approaching Mount Gambier Airport from Murray Bridge, the track deviation and approximate locations when initial CTAF calls were made, and inset, a map of South Australia showing the relative positions of Adelaide, Murray Bridge and Mount Gambier
Source: Google Earth and OzRunways, annotated by ATSB
At 0941, the pilot of YTM broadcast on the common traffic advisory frequency (CTAF)[4] that the aircraft was 7 NM from the aerodrome at an altitude of 1,000 ft. This was followed by a second broadcast 2 minutes later, about 5 NM to the north-west of the aerodrome in which the pilot requested the cloud base over the airport. The pilot of an aircraft operating under the instrument flight rules (IFR)[5] that was taxiing out at Mount Gambier Airport, responded that the ‘cloud base is at the minima…we’re departing out to the east where it’s a bit clearer…it’s fairly well fogged in to the west and to the south…you should get in.’ The pilot of YTM replied to this asking the pilot to confirm that he could get in from the south or west, and the pilot of the IFR aircraft indicated possible better visibility to the north-west.
After approaching the airport from the south-east, the aircraft made several manoeuvres at a low height, including a series of turns at about 200 ft above ground level (AGL) (Figure 2). Witnesses near the airport reported hearing an aircraft, but due to the low, thick cloud, the aircraft was not visible.
At 1003, as YTM passed over the top of runway 36 in a westerly direction, the pilot made a CTAF broadcast ‘lining up for 36’, indicating that he intended to land on runway 36. Witnesses reported that the pilot then conducted a go around after initially touching down on runway 36, and witnesses reported then seeing the aircraft climb back into cloud. The pilot then broadcast on the CTAF ‘going around for runway 24’. After another two low-level turns over the airport, in which the aircraft was captured emerging from the cloud on closed‑circuit television (CCTV) at low altitude, the aircraft landed on runway 29 at about 1008.
Figure 2: Track of YTM approaching Mount Gambier Airport, low-level manoeuvres, and location of CTAF calls
Source: Google Earth and OzRunways, annotated by ATSB
The pilot then boarded the two passengers to conduct the flight to Adelaide. The pilot broadcast that he was lined up and rolling on runway 24, and the aircraft took off from Mount Gambier Airport at 1020, approximately 20 minutes later than the intended departure time. At the time YTM departed, CCTV footage and Bureau of Meteorology (BoM) live weather cameras showed the presence of low cloud and reduced visibility conditions.
The OzRunways data showed that, just after take-off at an altitude of about 100 ft AGL, YTM’s track veered slightly to the left of the runway. The aircraft reached a maximum altitude of about 300 ft AGL, 45 seconds after take-off. The last recorded position, about 65 seconds after take-off, showed the aircraft at an altitude of 200 ft AGL (Figure 3). Soon after, the aircraft impacted terrain. A number of witnesses heard a loud bang, consistent with the ground impact.
Figure 3: Flight path of VH-YTM after departing runway 24 at Mount Gambier Airport. Each vertical line represents 5 seconds
Source: Google Earth and OzRunways, annotated by ATSB
The aircraft wreckage was located just over 200 m south of the last recorded position, approximately 2 km from the departure runway (Figure 3). Minutes after impact the aircraft was found by witnesses passing the accident site (Figure 4), and emergency services responded to the scene shortly thereafter. The pilot and two passengers were fatally injured, and the aircraft was destroyed.
Figure 4: Accident site, showing the engine and propeller location, the left- and right-wing impact marks and the main wreckage
The pilot obtained a Private Pilot (Aeroplane) Licence in December 2014, and held the appropriate aircraft endorsements required to operate YTM. His logbook showed a total aeronautical experience of approximately 530 hours. In the 90 days prior to the accident flight, he had conducted the three take-offs and landings required by Civil Aviation Safety Regulation (CASR) 61.395 to permit the carriage of passengers. At the time of the accident, he held a valid Class 2 Aviation Medical Certificate renewed on 6 June 2017. This included a requirement for reading vision correction to be available while exercising the privileges of the licence.
The pilot commenced training for a Night Visual Flight Rules (VFR) rating in December 2015; this included about 3.5 hours recorded as instrument flight time. The pilot completed a total of 12 hours of training in flight under night VFR between December 2015 and May 2016, however he did not obtain this qualification. The pilot did not hold an instrument rating and his logbook recorded a total of 7 hours of instrument flight time, the latest of which was 0.1 hours in simulated flight conditions during an aeroplane flight review on 29 November 2016.
The ATSB assessed whether the pilot may have been experiencing a level of fatigue known to have an effect on performance. Consideration was made of the pilot’s sleep obtained, time awake at the time of the occurrence, time on task, potential workload and environmental factors. Based on the available evidence, the pilot was very unlikely to have been experiencing a level of fatigue known to affect performance.
Medical and pathological information
The pilot’s medical records, postmortem examination and toxicological analysis identified no acute or pre-existing medical conditions that may have contributed to the accident.
Aircraft information
General
YTM was a SOCATA TB-10 five-seat, low-wing, all-metal, unpressurised aircraft designed and manufactured in France, with a fixed undercarriage. Power was provided by a Lycoming O-360-A1AD four-cylinder piston engine, rated at 180 horsepower, through a McCauley three-bladed constant-speed propeller.[6]
Maintenance release
The aircraft maintenance release was issued on 4 May 2017 for 12 months or 100 hours flight time, whichever occurred first. The aircraft had flown for approximately 44 hours since the maintenance release at the time of the accident. The maintenance release was issued in the IFR category[7] and the aircraft was appropriately equipped. The documentation did not identify any unserviceable equipment or defects at the time of the accident.
The maintenance release indicated that a ‘portable emergency locator transmitter’ was required to be carried to satisfy the requirements of Civil Aviation Regulation (CAR) 252A requiring the installation of a 406 MHz emergency locator transmitter. A personal locator beacon was found in the cockpit, but had not been activated. The aircraft was not fitted with a flight data recorder or cockpit voice recorder; nor were either required.
Weight and balance
Seating positions, and approximate passenger and baggage weight were known at the time of the accident. From this information, and taking into account any fuel loading, it was calculated that the aircraft’s centre of gravity would have been within the manufacturer’s permitted range when departing Mount Gambier Airport. The aircraft weight was also calculated to be below the maximum take-off weight at the time of the accident.
Wreckage and impact information
Ground scars and evidence from the wreckage indicated that the aircraft impacted the ground nose down in an inverted attitude, approximately 30° from vertical, and that the engine was producing power at the time of impact. A strong smell and presence of fuel was evident at the accident site, however, there was no evidence of a pre- or post-impact fire. The impact sequence was not survivable.
On-site examination of the wreckage established continuity of all flight controls, and that all of the primary structural components were in the immediate area of the accident site. No pre-impact damage or failure of the primary structural components or the aircraft flight control system were identified.
A number of instruments and other components were recovered from the accident site for further technical examination at the ATSB facilities in Canberra. It was determined that there was no pre‑impact damage or failure of any of the components.
Carburettor icing
The conditions recorded at Mount Gambier Airport at the time of the accident were applied to a Civil Aviation Safety Authority (CASA) carburettor icing probability chart. Based on this chart, the probability of carburettor icing at any power setting was serious.
Due to accident damage, the carburettor heat control settings could not be determined. However, the recorded flight path, witness statements, the impact sequence, ground markings and wreckage analysis indicated the engine was performing normally before the accident. It was therefore concluded that carburettor icing was not a factor.
Airport information
Mount Gambier Airport is located about 8 km to the north of the city of Mount Gambier. It was a non‑controlled aerodrome, in Class G airspace. As shown in Figure 5, it has three runways, aligned 18/36, 11/29 and 06/24. Instrument approaches were only available on runways 18/36.
Different minima[8] apply for aircraft depending on whether they are landing or departing, conducting flight under Instrument Flight Rules (IFR) or VFR, and the category of aircraft being flown.
As outlined in CASA’s Visual Flight Rules Guide, standard circuit procedure is normally a left‑circuit pattern (as shown in Figure 5). For aircraft such as YTM, the standard circuit height is 1,000 ft above the aerodrome elevation (Mount Gambier Airport elevation is 212 ft above mean sea level (AMSL)). To allow the aircraft to be stabilised for approach, the turn onto the final leg should be completed by not less than 500 ft above the aerodrome elevation.
For pilots operating under VFR, as was the case for YTM, for both landings and departures, they are required to remain clear of cloud, and have a visibility of at least 5,000 m.
Figure 5: A standard circuit approach is shown on the left, and alignment of Mount Gambier Airport runways is shown on the right
Source: Google Earth with ATSB annotations
For Category A,[9] Category B and Category C aircraft conducting an RNAV GNSS instrument approach,[10] the lowest approach minima was 518 ft AGL with a required visibility of 2,900 m. For aircraft conducting an approach using either non-directional beacon or VHF omnidirectional radio range the approach minima was 668 ft with a required visibility of 2,400 m (for Category A and B aircraft), or 768 ft AGL with a required visibility of 4,000 m for Category C aircraft.
For aircraft conducting a single engine IFR departure, a cloud ceiling of 300 ft and visibility of 2,000 m was applicable.
Meteorological information
Visual flight rules
CASA’s Visual Flight Rules Guide outlined that flight under VFR may only be conducted in visual meteorological conditions (VMC). For Class G airspace, as at Mount Gambier Airport, these conditions included:
For aircraft operating at or below 3,000 ft AMSL or 1,000 ft AGL (whichever is higher), a minimum visibility of 5,000 m, remaining clear of cloud and in sight of ground or water.
For aircraft operating below 10,000 ft, a minimum flight visibility of 5,000 m and a vertical and horizontal distance from cloud of 1,000 ft and 1,500 m respectively is required.
Forecast weather
The Bureau of Meteorology (BoM) provides observations, forecasts, warnings and advisories for aviation operations. For flight planning purposes, pilots are required to obtain the relevant information for the flight from Airservices Australia, the official provider of aeronautical information services.
Area forecasts (ARFOR)[11] for the proposed route included Area 50 and Area 30; Area 50 covered the proposed route from Murray Bridge to Mount Gambier Airport, and return to Adelaide, with Mount Gambier Airport located on the border of Area 50 and Area 30.
The ARFOR for Area 50 valid at the time of the pilot’s departure from Murray Bridge was issued by BoM at 0605 and was valid to 1730. The forecast included scattered showers, isolated thunderstorms and broken[12] low cloud until 1030, with isolated fog and mist forecast until 0930.
The ARFOR for Area 30 valid at the time of the pilot’s departure from Murray Bridge was issued by BoM at 0700 and was valid to 2030. The forecast included isolated to widespread showers, fog patches and broken low cloud.
The aerodrome forecast (TAF)[13] for Mount Gambier issued at 0744 included a forecast of fog, visibility of 500 m and broken low cloud at 300 ft AGL until 0930. It also included an INTER[14] from 0930 to 1230 for showers with associated visibility of 5,000 m and broken low cloud at 1,000 ft AGL.
An amended Mount Gambier TAF was released at 0942 while YTM was en route to Mount Gambier. The amended TAF included showers of rain, scattered cloud at 1,000 ft AGL, visibility of greater than 10 km, and included the same INTER as the previous TAF.
Shortly after 1030, a pilot operating in the vicinity of Mount Gambier telephoned the BoM aviation forecaster, to advise conditions at Mount Gambier Airport were worse than indicated by the TAF. In response to that call, at 1039 the TAF was again amended to include a forecast of fog and broken low cloud at 200 ft AGL with visibility of 800 m, from 1030.
From the evidence available, the ATSB could not determine if the pilot accessed the available weather forecasts or observations prior to departing Murray Bridge, or at any point en route.
Actual weather conditions
Weather recordings
Live weather observations were available to the pilot through the Automatic Weather Information System. Weather observations at Mount Gambier Airport were issued as a SPECI[15] every half an hour on the morning of the accident flight with the information seen in Table 1.
Table 1: Visibility and cloud height observation reports
Time of issue
Visibility (m)
Cloud (height AGL)
0730
350
Overcast at 200 ft
0800
350
Overcast at 200 ft
0830
450
Overcast at 200 ft
0900
1,500
Overcast at 200 ft
0930
1,800
Overcast at 200 ft
1000
3,400
Overcast at 200 ft
1030
4,000
Overcast at 200 ft
These observations indicated that visibility between 1000 and 1030 was still below the minimum required for VFR flight but was generally increasing as the morning progressed. The overcast (complete sky cover) cloud height observations also indicated that an aircraft would almost certainly not be able to remain clear of cloud or to keep the ground in sight above 200 ft AGL.
Observational weather data from the aerodrome automatic weather station (AWS) were recorded at 1-minute intervals, as were images from the live weather cameras. These were located near the runway junction, with images captured in four directions—north-east, north-west, south-east, and south-west. The AWS data and the weather camera images (Figure 6) indicated that low visibility conditions, with clouds broken or overcast at a ceiling of 200 ft, were present at the airport at the time of YTM’s approach and subsequent departure.
Figure 6: An image from the BoM weather camera at 1020, showing the direction of take-off
Source: Bureau of Meteorology, annotated by ATSB
An analysis of the local weather at the time of the accident flight was provided by BoM. The analysis concluded that:
…areas of patchy fog persisted until mid-morning then lifted into a mix of mist/haze and low cloud which persisted til late morning… It is considered likely that around the time of the incident conditions would have included broken low cloud and visibility reducing at times in mist.
Witness and camera observations
Airport closed‑circuit television (CCTV) footage of the approach, taxiing, and departure of YTM showed the aircraft passing in and out of cloud at low levels (Figure 7).
Figure 7: Mount Gambier Airport CCTV images of YTM conducting a low level manoeuvre on approach over the airport at 1006 with aircraft highlighted (top), and taxiing out to runway 24 at 1018 (bottom)
Source: Mount Gambier Airport, annotated by ATSB
A number of witnesses heard the aircraft in the vicinity of the airport (both when arriving and departing), however, due to low cloud, the aircraft was not visible. The cloud base was estimated by witnesses to the west of the airport be at about 200 ft AGL. Witnesses located at the airport observed the aircraft pass in and out of cloud during the low level manoeuvring on approach, and again on departure.
Pilots operating in the area at the time YTM approached, landed and took off, reported the weather was clearing to the east, but was below the required IFR minima (see Airport information section for minima) to the north and to the west. Due to the prevalent weather conditions at Mount Gambier Airport being below the VFR minima, witnesses assumed that YTM was operating under IFR, and the pilot responses on the CTAF referred to IFR criteria. The pilot of an aircraft that departed under IFR on runway 06 prior to YTM approaching the airport reported being in cloud with no visibility between 500 ft and 1,000 ft AGL.
Two regular public transport (RPT) flights were due to arrive at Mount Gambier Airport about the time YTM arrived and departed. Based on the forecast and observed weather conditions, one flight delayed its departure for Mount Gambier by approximately two hours, as the weather was below IFR minima for landing. The other aircraft, having attempted an approach to Mount Gambier Airport at 1030, conducted a missed approach, and remained in a holding pattern to the south of the airport for 50 minutes until the conditions cleared sufficiently to land. Both these RPT aircraft were operating under IFR. Another aircraft operating under IFR from Adelaide to Mount Gambier delayed its 0830 departure for two hours due to the forecast and observed weather. On approaching Mount Gambier Airport at approximately 1120, due to the weather present, the pilot was unable to sight the runway by the required minimum descent altitude and elected to divert to an alternate aerodrome.
Flight in low visibility conditions
Risks of flying in areas of reduced visual cues
The safety risks of VFR pilots flying from visual meteorological conditions (VMC) into instrument meteorological conditions (IMC)[16] are well documented. This has been the focus of numerous ATSB investigations and publications, as VFR pilots flying into IMC has been identified as a contributing factor in a considerable number of aircraft accidents and fatalities. The ATSB Avoidable Accidents series booklet (AR-2011-050) titled Accidents involving pilots in Instrument Meteorological Conditions outlines that:
In the 5 years 2006–2010, there were 72 occurrences of visual flight rules (VFR) pilots flying in instrument meteorological conditions (IMC) reported to the ATSB…About one in ten VFR into IMC events result in a fatal outcome.
Additionally, a study conducted by the United States’ National Transportation Safety Board (NTSB, 2005) found that reduced-visibility weather represents a particularly high risk to general aviation pilots, testing ‘the limits of pilot knowledge, training, and skill to the point that underlying issues are identified.’
The NTSB study also outlined that historically, about two-thirds of all general aviation accidents that occur in IMC are fatal; a rate much higher than the overall fatality rate for general aviation accidents. A study by Newman (2007) conducted for the ATSB titled An overview of spatial disorientation as a factor in aviation accidents and incidents outlined that there was a four times greater chance of fatality in a VFR flight into IMC accident than any other sort of accident (quoting Batt and O’Hare, 2005 and NTSB, 1989).
In the context of this accident, it is therefore important to outline why the risk of entering IMC is so high, which is linked directly to how and why pilots experience spatial disorientation when entering areas of low visibility.
Experiencing spatial disorientation
The ATSB Avoidable Accident booklet outlines that there are three sensory systems used by pilots to establish or maintain orientation relative to the environment. The visual system is by far the most important system, providing 80 per cent of orientation information. The remaining 20 per cent is split equally between the vestibular system, which obtains its information from the balance organs in the inner ear, and the somatic system, which uses the nerves in the skin and proprioceptive senses in our muscles and joints to sense gravity and other pressures on the body. In the absence of visual references, both the vestibular and somatic senses can be misinterpreted and are prone to illusions.
Spatial disorientation is defined by Benson (1999) as where ‘the pilot fails to sense correctly the position, motion or attitude of the aircraft or of him/herself’ with respect to the ground. For pilots flying under VFR, seeing the horizon is crucial for orientation of both the pilot’s sense of pitch and bank of the aircraft (Gibb and others, 2010). In conditions of low visibility, where the horizon may not be visible to the pilot, they can become rapidly disorientated.
Benson (1999) outlined that spatial disorientation would typically occur within 60 seconds of all visual cues being removed, while another United States study showed a loss of control by non-instrument rated pilots within an average of 178 seconds after the loss of all visual cues (Bryan, Stonecipher, and Aron, 1954).
Spatial disorientation presents a danger to pilots as the resulting confusion can often lead to incorrect control inputs and resultant loss of aircraft control. Gibb and others (2010) state that spatial disorientation accidents have a fatality rate of about 90 per cent, indicating how compelling the misperceptions can be.
A range of factors can influence the extent to which a pilot may experience or be able to recover from spatial disorientation. Common factors include limited or ambiguous visual cues outside the cockpit, not directing sufficient attention to the flight instruments due to workload or distraction, and not being proficient in instrument flying skills. The risk of experiencing spatial disorientation can be managed effectively in the absence of external visual cues by reference to suitable aircraft instrumentation. However, controlled flight by sole reference to cockpit instruments is a separate and complex learned skill from those skills associated with flight in visual conditions.
In the absence of visual information, a pilot’s perception (or lack of perception) of movement obtained from their vestibular system (inner ear) can lead to spatial disorientation. Two vestibular‑based illusions are the somatogravic and somatogyral illusions.
Somatogravic illusion
The vestibular illusion known as somatogravic illusion is associated with acceleration, particularly at take-off. Any vehicle that accelerates will push a forward-facing occupant backward in their seat. This generates a vestibular sense that is very similar to the sensation of tilting back. In the absence of supporting visual cues, it is possible for pilots to mistake this vestibular sense when accelerating (such as for take-off) with a sense of a pitch-up change in attitude. It is more pronounced with greater acceleration during the take-off run. A greater take-off speed, particularly if the aircraft continues to accelerate after take-off, can further amplify the illusion in the absence of significant external visual cues.
The risk of somatogravic illusion is that the pilot responds by pitching down, which is particularly dangerous soon after take-off. The illusion can be mitigated by pilots being aware of it and understanding it, and by effective use of flight instruments to control the aircraft in the seconds after take-off. This illusion is most prevalent and hazardous immediately after take-off in fixed wing aircraft, but can also occur when the aircraft is longitudinally accelerated.
Somatogyral illusion
This illusion relates to a pilot’s incorrect understanding of an aircraft’s angle of bank. The pilot’s vestibular system will register an angular acceleration (above a threshold level) when the aircraft’s angle of bank is changed. Once the aircraft is in a constant turn, the pilot’s vestibular system will stop registering any input because there is no angular acceleration. In the absence of any other sensory information or vestibular input a pilot may experience a sensation that the aircraft is no longer turning.
This sensation is normally overridden by the visual system that is influenced by seeing the world rotating as the turn continues. However, in the absence of external visual cues, successful orientation relies on the use of the information available from the aircraft’s flight instruments. The perceived conflict of information between the vestibular and the visual cues requires a pilot to disregard vestibular sensations in preference to flight by reference to the flight instruments alone.
If a roll movement occurs gradually, it may be below the level that a pilot can detect through the vestibular senses. The human threshold for detecting a short duration roll movement (5 seconds or less) is about 2° per second, and for longer durations, it is about 0.5° per second (Cheung, 2004). When flying, these sensory thresholds are often higher, particularly when a pilot’s attention is directed elsewhere (Benson, 1999). With limited or no external visual information, gentle rolls can continue unnoticed unless detected through the monitoring of instruments.
However, if noticed from instruments and corrected, the return roll to straight flight often occurs faster and is therefore perceived by the vestibular senses. The pilot may end up with the sensation that the aircraft is now in a turn (in the opposite direction). This can also occur in longer turns when the initial sense of roll stops during the turn. Commonly known as ‘the leans’, this sensation will wear off in time each occasion it is experienced, but unless the aircraft is flown solely by instruments, it has the potential to disorientate the pilot.
Instrument flying proficiency
Entering IMC conditions with no instrument rating carries a significant risk of severe spatial disorientation (Frederick, 2002; Batt and O’Hare, 2005; Transportation Safety Board of Canada, 1990; NTSB, 1989). Furthermore, Groff and Price (2006) found that the risk of an accident in reduced visibility increases nearly five-fold for pilots that did not hold an instrument rating.
When there are no external visual cues, the ability to fly on instruments is essential. The NTSB (1988) also noted that ‘tests and experience have shown that non-instrument-trained pilots or non‑proficient pilots are rarely successful in overcoming spatial disorientation’. Gibb and others (2010) add that a visual-only general aviation pilot encountering weather or night conditions is severely at risk because of their total inexperience, education, and training in using instruments.
Although instrument flying proficiency is a very important defence against spatial disorientation, many studies have shown overall flying hours has little, if any, influence on spatial disorientation accident rates (Gawron, 2000). Importantly, Gawron (2000) stated that the level of training and recency of the training to be factors, with those inexperienced in instrument flight, or with a lack of recent instrument flying, being at higher risk of spatial disorientation. In an effort to communicate how pilots can reduce the risk, Newman (2007) outlined:
It is advisable for pilots to undertake regular instrument flight exposures, preferably with an experienced instructor. This can be combined with some inflight disorientation demonstrations and upset/unusual attitude recovery practice (Braithwaite, 1997; Collins, Hasbrook, Lennon, & Gay, 1978).
Weather-related pilot decision making
A study by Wiegmann and Goh (2000) suggested a number of possible factors that contribute to instances of VFR flight into adverse weather conditions. These included:
situation assessment (an inaccurate assessment by a pilot of the conditions)
risk perception (a pilot may not appreciate the risks involved with continuing the flight)
motivational factors (‘get-home-itis’ or personal/social pressures to complete the flight).
That is, pilots are seen to engage in VFR flight into IMC because they do not accurately assess the hazard (that is, the deteriorating weather conditions).
Specifically, one of the reasons why pilots may decide to continue a VFR flight into adverse weather is that they make errors when assessing the situation. However, pilots are often simply trying to make decisions to the best of their ability. The NTSB (2005) outlined that:
Even if pilots are able to correctly assess current weather conditions, they may still underestimate the risk associated with continued flight under those conditions, or they may overestimate their ability to handle that risk.
When outlining how weather-related decision making could be improved, Wiggins and O’Hare (1995) stated:
Because of the variable nature of operations in the aviation environment, weather-related decision making is often considered a skill that cannot be prescribed during training. Rather it is expected to develop gradually through practical experience. However, in developing this type of experience, relatively inexperienced pilots may be exposed to hazardous situations with which they are ill‑equipped to cope.
Wiggins and O’Hare (2003) also evaluated the effectiveness of a cue-based training system, which was designed to equip VFR pilots with the skills to recognise and respond to the cues associated with deteriorating weather conditions during flight. VFR pilots were more likely to use the cues following the training, with subsequent improvements in their weather-related decision‑making. CASA produced a Weather to Fly[17] education program which focuses on topics such as the importance of pre-flight preparation, making decisions early and talking to air traffic control, along with initiatives to help pilots establish personal minimums.
Related occurrences
The US NTSB investigated four accidents involving community service flights[18] in 2007 and 2008, which resulted in three Safety Recommendations being issued (see Identified community service flight risks below).
The ATSB has investigated one other fatal accident and one incident involving flights organised by Angel Flight Australia, which are summarised below. Additionally, a number of recent ATSB investigations examined VFR into IMC accidents.[19] Of these, two are summarised below, as is the ATSB research report AR-2008-045Improving the odds: Trends in fatal and non-fatal accidents in private flying operations.
ATSB investigated Angel Flight Australia occurrences
On 15 August 2011, the pilot of a Piper PA-28-180 Cherokee aircraft, registered VH-POJ, was conducting a private flight arranged by Angel Flight Australia, transporting two passengers from Essendon to Nhill, Victoria under VFR. The flight was arranged to return the passengers to their home location after medical treatment in Melbourne.
Global Positioning System data recovered from the aircraft indicated that when about 52 km from Nhill, the aircraft conducted a series of manoeuvres followed by a descending right turn. The aircraft subsequently impacted the ground at 1820 Eastern Standard Time, fatally injuring the pilot and one of the passengers. The second passenger later died in hospital as a result of complications from injuries sustained in the accident.
The ATSB found that the pilot landed at Bendigo and accessed a weather forecast before continuing towards Nhill. After recommencing the flight, the pilot probably encountered reduced visibility conditions approaching Nhill due to low cloud, rain and diminishing daylight, leading to disorientation, loss of control and impact with terrain.
On 9 December 2011 a SOCATA TBM 700 aircraft, registered VH-VSV, departed Bankstown Airport for a private flight arranged by Angel Flight Australia to Merimbula, New South Wales. Onboard the aircraft were the pilot and one passenger.
The pilot was cleared to depart Bankstown control zone on a downwind departure from runway 11 left, however, the pilot mistakenly conducted an upwind departure. The aircraft penetrated Sydney controlled airspace by 2.3 NM and came within 1.2 NM horizontally with no vertical separation of another aircraft on approach into Sydney Airport and a loss of separation occurred.
The investigation highlighted the importance of developing a technique to ensure a clearance is processed, understood and actioned correctly. It is also important to clarify a clearance if any ambiguity exists. Finally, pre-flight planning is essential to ensure safe flight.
At about 1730 on 7 November 2015, the owner-pilot of an Airbus Helicopters (Eurocopter) EC135 T1, registered VH-GKK, departed Breeza, New South Wales, on a private flight to Terrey Hills, New South Wales. The flight was conducted under VFR and there were two passengers on board.
About 40 km to the south-west of the Liddell mine, the pilot diverted towards the coast, probably after encountering adverse weather conditions. Witnesses in the Laguna area observed the helicopter overfly the Watagan Creek Valley in the direction of higher terrain. The helicopter was then observed to return and land in a cleared area in the valley.
After 40 minutes on the ground, the pilot departed to the east towards rising terrain in marginal weather conditions. About 7 minutes later and approximately 9 km east of the interim landing site, the helicopter collided with terrain. The pilot and two passengers were fatally injured.
The ATSB found that the pilot departed an interim landing site under VFR in marginal weather conditions. The pilot likely encountered reduced visibility conditions leading to loss of visual reference leading to the collision with terrain.
On the morning of 29 January 2016, a Piper PA-28-235 aircraft, registered VH-PXD, was on a private flight from Moorabbin Airport, Victoria to King Island, Tasmania. After passing over Point Lonsdale, the aircraft entered an area of low visibility. The pilot conducted a 180° turn and initially tracked back towards Point Lonsdale, before heading south over the ocean. After about 2 minutes, the aircraft was again turned right before entering a rapid descent. The aircraft impacted the water 6.6 km south-west of Point Lonsdale. All four occupants of the aircraft were fatally injured.
The ATSB found that continuation of the flight beyond Point Lonsdale, and towards an area of low visibility conditions, was likely influenced by the inherent challenges of assessing those conditions.
The ATSB also found that due to the presence of low cloud and rain, the pilot probably experienced a loss of visual cues and became spatially disorientated, leading to a loss of control and impact with the water. The risk of a loss of control in the conditions was increased by the pilot’s lack of instrument flying proficiency.
The ATSB research report Improving the odds: Trends in fatal and non-fatal accidents in private flying operations found that 44 per cent of all accidents and over half of fatal accidents between 1999 and 2008 were attributed to private operations.[20] These figures far surpassed the proportions for any other flying category, even though private operations contributed to less than 15 per cent of the hours flown in that decade.
Problems with pilots’ assessing and planning were identified as contributing factors in about half of fatal accidents in private operations, and about a quarter involved problems with aircraft handling. Other contributing factors associated with fatal accidents to a smaller extent were visibility, turbulence, pilot motivation and attitude, spatial disorientation, and monitoring and checking. Non-fatal accidents were just as likely to involve aircraft handling problems, but had fewer contributing factors than fatal accidents.
Action errors and decision errors were both common to fatal accidents. Violations, while less frequently found, were mostly associated with fatal accidents.
In light of the contributing factors that were associated with fatal accidents in private operations, the report provides advice to pilots for improving the odds of a safe flight. Pilots are encouraged to make decisions before the flight, continually assess the flight conditions (particularly weather conditions), evaluate the effectiveness of their plans, set personal minimums, assess their fitness to fly, set passenger expectations by making safety the primary goal, and seek local knowledge of the route and destination as part of their pre-flight planning. In addition, becoming familiar with the aircraft’s systems, controls and limitations may alleviate poor aircraft handling during non-normal flight conditions. Finally, pilots need to be vigilant about following rules and regulations that are in place—they are there to trap errors made before and during flight. Violating these regulations only removes these ‘safety buffers’.
Organisational information
Angel Flight Australia
Background
Angel Flight Australia (Angel Flight) is a charity that assists financially disadvantaged people who cannot readily access financial assistance from other sources, to access medical services that are not available locally. It was established in 2003 and was based on the model operating in the United States at the time. The Angel Flight website described the operation as:
a charity which coordinates non-emergency flights to assist country people to access specialist medical treatment that would otherwise be unavailable to them because of vast distance and high travel costs. All flights are free and may involve travel to medical facilities anywhere in Australia.
The Australian Charities and Not-for-profits Commission (ACNC) lists Angel Flight’s constitution. The objects in that constitution stated that Angel Flight:
… assists financially disadvantaged people throughout Australia by:
a) Arranging carriage of financially disadvantaged people with medical conditions, in non-emergency circumstances;
b) Arranging carriage of such people in aircraft which contain no specialised medical fittings or equipment;
c) Arranging carriage of such people in aircraft without any requirement for medically trained personnel to be on board;
d) Arranging carriage of such people on the condition that they are sufficiently fit to undertake normal travel without assistance, and in the case of children or persons with a disability, to travel with a carer who can render any assistance required;
e) Arranging carriage of such people without any charge being made and without any form of reward being received by the pilot, aircraft owner or the Company [Angel Flight] in respect of that carriage, provided however, that the Company [Angel Flight] may, from time to time, authorise reimbursement of the cost of fuel for flights;
f) Arranging, where possible, free air transportation of blood and blood products and transplant organs to needy recipients; and
g) Arranging further support, monetary or otherwise, to financially disadvantaged people in need of medical treatment in Australia.
h) Arranging ground transport at city venues for transportation of such people to and from medical or treatment centres, either by commercial taxi service or volunteer drivers/vehicle owners, and in the case of private volunteer drivers/vehicle owners, that no charge be made or reimbursement being received by the driver/vehicle owner, provided however, that the Company [Angel Flight] may, from time to time, authorise appreciation gift cards to be provided to drivers/vehicle owners.
For passengers (a patient and their travelling companion—if any) to be considered for a flight, a formal request must be submitted by a health professional registered with Angel Flight. In submitting the request, the health referrer certifies the patient and any travelling companion meet Angel Flight’s criteria of requiring financial assistance to travel for medical treatment that is not available locally.
Most flights co-ordinated by Angel Flight are conducted using volunteer pilots on flights classified as private operations, and Angel Flight did not hold an Air Operator’s Certificate (see Civil Aviation Safety Authority below). However, about 18 per cent of the passenger flights co-ordinated by Angel Flight were conducted on commercial RPT flights, with the cost of these flights covered by Angel Flight.
To enable the private flights to be provided to the passengers free of charge, Angel Flight negotiated waivers of the Airservices Australia landing and air navigation charges, and reimburses pilot fuel costs. As at June 2017 Angel Flight had co-ordinated the conduct of about 20,000 passenger carrying flights, referred to as ‘missions’, and had 3,180 registered pilots. A handbook provided to Angel Flight pilots specified that ‘it is the objective of this organisation to assist as many people as possible that need our services, within the scope of the Angel Flight charter and standards.’
Pilot and aircraft requirements
To volunteer for Angel Flight, pilots needed to have a minimum of 250 hours as pilot in command (PIC), with either 5 hours as PIC on the aircraft type for flight to be conducted under VFR, or 10 hours on aircraft type for flights to be conducted under IFR. They also needed access to a VH‑registered aircraft,[21] with public liability insurance. Pilots need to provide copies of their licence, aviation security identification card, and any required flight reviews, proficiency checks and medical certificate. Prior to being assigned to any planned flight, pilots have to re-confirm their license and currency requirements were met, that the aircraft was insured for public liability and all maintenance complied with relevant statutory provisions.
For this accident, consistent with Angel Flight requirements the pilot of YTM was appropriately licensed for the planned private VFR flight, had maintained currency and recency on the TB10 aircraft, and had undertaken numerous Angel Flight missions in the recent past, including flying the passengers involved in the accident flight. The aircraft was appropriately insured and maintained to complete the planned flight.
Pilot documentation
Once the minimum criteria were satisfied and a pilot was registered to conduct flights on its behalf, Angel Flight would send pilots a number of documents including a pilot handbook, a pilot affirmation form, its code of conduct, and information regarding work health and safety for volunteers.
The pilot handbook contained guidelines on how to complete a flight successfully on behalf of Angel Flight. It contained advice relating to the safety of the flight such as:
Ability to cancel the flight: the pilot was responsible for the conduct of the flight and could cancel the mission for any reason. ‘No flight will be for time-critical or emergency situations…The passengers will be aware that the flight may be cancelled should the pilot have any safety concern.’
Pilot competency: ‘Be competent. The release form signed by your passengers will show that they recognise the gains and risk. Act in a reasonable manner and be able to show that you know what you are doing.’
Prepare alternate plans: ‘Even the best plans go astray. Develop a ‘Plan B’. For example, an alternate airport due to a NOTAM[22] being issued or a change in the weather’, and ‘get a full weather briefing immediately before flying the flight.’ ‘There are always alternatives, such as: waiting until later in the day, waiting until the next day…or even cancelling the flight.’
Regulatory compliance: ‘CASA regulations must be adhered to for the flight to be legal…Angel Flight does not attempt to cover this issue. ... All pilots volunteering for Angel Flight are required by law to prepare for a flight in accordance with CARs and CASRs including but not limited to flight planning, weather briefing, pre-flight, airworthiness inspections, licensing etc. These subjects will not be addressed in this document.’
Additionally, when applying online for a flight, the following comment was displayed:
‘Please Remember: Never compromise safety in any way in order to complete a flight. Cancelling a flight is considered a demonstration of good judgement and will never be criticized.’
Flight planning requirements
Guidance provided by Angel Flight to its volunteer pilots stated that the PIC was wholly responsible for the planning, operation and management of the flight. Any topics considered to be part of PIC responsibilities, including flight planning, weather briefing, pre-flight, airworthiness, and licensing requirements, were explicitly not addressed in any Angel Flight documentation.
Pilots and passengers were made aware that if a flight could not be completed, that Angel Flight would do its best to make alternative provisions for the passengers. Additionally, passengers were aware that they may be required to make their own alternative travel arrangements.
Flight requests and pilot assignment
To initiate an Angel Flight mission, a flight request would be submitted by an Angel Flight registered health professional, along with a referral regarding the passenger’s medical condition, and all required signed passenger documents (see Passenger documentation). Angel Flight mission co-ordinators then posted the request details on an e-bulletin board, accessible to registered pilots and drivers. Flight details included origin, destination, date and details of the proposed flight, number and weights of passengers, passenger medical condition, and baggage requirements. Pilots then registered their interest in a flight, and once all required passenger and pilot documentation were confirmed, the flight was assigned. If no applications were made and the flight date was approaching, mission co-ordinators contacted pilots based in the area via email in an attempt to assign the flight. Where the flight could not be assigned, or the pilot cancelled at short notice, RPT flights would then be considered as an alternative.
For this accident, consistent with the Angel Flight processes, an initial flight request and all required forms were submitted by the health referrer about 2 weeks prior to the passengers’ first Angel Flight in May 2017. Following this, a subsequent trip request for regular flights was submitted to Angel Flight. Based on the passenger’s needs and the frequency of the flights it was determined that return flights once a fortnight could be supported. Four private flights had been successfully completed, with one of these flights being conducted by the pilot involved in the accident.
On being assigned the accident flight, additional information provided to the pilot of YTM included passenger contact details, information regarding the ground transport to and from the medical facility, and return flight details. For the two passengers involved in the accident flight, one was accessing medical services in Adelaide, and the other was a family member.
Pilot and passenger communication
On being assigned a mission, pilots were advised to contact all parties involved and confirm the schedule.
On the day of the accident, between 0850 and 0900, text messages were sent between the pilot and passengers. A further message was sent by the passengers just prior to the arrival of YTM into Mount Gambier at 1006. The ATSB was unable to establish the content of the messages.
Passenger documentation
Passengers acknowledged, through a Patient Guidelines Form, that the flight was not a charter or ambulance flight, and that the pilots and aircraft did not meet commercial standards relating to qualifications, training or maintenance requirements, as they were not a commercial flying operation. The documents also stated that it is important the pilot stay on schedule as set by the appointment time, location of the passengers and location of the appointment, and the presence of connecting pilots or drivers at each destination.
Passengers were also required to sign a liability waiver noting acceptance of aviation related risks; however, there was no information provided in the documentation package outlining the comparative risks between flight operation types (see Safety comparison between private operations and commercial air transport), nor guidance or direction to where this information could be found. The Angel Flight briefing paper stated ‘our volunteer pilots’ flight credentials exceed the requirements of the Civil Aviation Safety Authority and the aircraft meet specified CASA and insurance minimums.’ This referred to the minimum number of PIC hours required, including at least 5 hours on the aircraft type for VFR flight and at least 10 hours on type for an IFR flight.
Reporting of flight safety occurrences
Air Operator’s Certificate (AOC) holders are required by CASA to have a safety management system (SMS). One standard aspect of an SMS is for the operator to maintain a record of incidents and accidents (occurrences)[23] and safety hazards which are reported to them by its pilots and others. The organisation must examine and investigate these occurrences and hazards where necessary, find ways of reducing risks identified, and/or provide awareness education for pilots, in order to improve the on-going safety of its operation.
As Angel Flight is a charity and not an aviation organisation, it is not required to hold an AOC. Therefore there was no regulatory requirement for pilots to report to Angel Flight any safety hazards or occurrences that took place during a flight operated for it. Angel Flight only required its pilots to notify them if a withdrawal or suspension of its licence, ratings or endorsements occurred.
Angel Flight had implemented a voluntary fuel report, through which pilots submitted fuel records for subsequent reimbursement, which also included a comment section. This section was predominantly used to comment on the fuel usage; there was no request for any safety related information.
In response to the ATSB investigation AO-2011-100 into the 2011 fatal accident of an Angel Flight organised flight (see Related occurrences above), Angel Flight provided information in June 2013 that showed that it was aware of three accidents (including AO-2011-100) and two incidents that had occurred during the conduct of Angel Flight missions. These occurrences had been communicated to Angel Flight through a variety of informal channels. In response to two of the four non-fatal occurrences, Angel Flight requested the pilots involved provide further information and documentation in relation to the occurrences and, in one case, required that the pilot undergo remedial training and provide evidence of its satisfactory completion prior to undertaking further missions. These responses were additional and separate to any regulatory action taken by CASA in response to these incidents.
Civil Aviation Safety Authority
CASA is an independent statutory authority with the primary function of conducting the safety regulation of civil air operations in Australia and the operation of Australian aircraft overseas.
Under the Australian civil aviation regulations there were four separate classes of operations:
regular public transport (RPT)
charter
aerial work
private.
Different regulatory requirements apply to each class of operation, with RPT operations having the highest minimum standards and regulatory oversight, and private operations having the most limited.
Previous CASA advice, in relation to ATSB investigation AO-2011-100, outlined flights conducted on behalf of Angel Flight were classified as private operations. For flights conducted under private operations, all operational responsibility for the flight remained with the pilot in command (PIC). This was consistent with advice received from Angel Flight that it was not (and never had been), an AOC holder or operator.
CASA completed a regulatory review of the safety requirements outlined in the Civil Aviation Regulations and Civil Aviation Orders in 1996, with the revised legislation to be termed Civil Aviation Safety Regulations (CASRs). Following this review CASA identified the change in the operation classification, from the current four-tier system to a three-tier system, where all passenger carrying operations (RPT and charter) are to be combined into the same tier. This created an issue in relation to how Angel Flight operations could continue as private operations while carrying passengers as a service.
Discussion paper DP1317OS: Safety standards for community service flights
As part of CASA’s ongoing regulatory reform process, for each of the areas affected by the regulatory development, stakeholders were identified and consulted. Part of the consultation included the publication of a discussion paper DP1317OS – Safety standards for community service flights conducted on a voluntary basis’ in August 2014, for industry consideration and input regarding community service flights, and how they should be regulated under the new CASRs. The discussion paper considered the concept of community service flights as:
flights that are provided on a voluntary basis for public benefit. The term refers only to non-emergency flights provided as part of an organised voluntary or charitable activity and does not include the ‘one-off’ type of flight in which a pilot provides a flight to a friend or family member.
Prior to this discussion paper being published, CASA held preliminary consultation meetings with two charities identified as operating community service flights, which included Angel Flight, in which the proposed CASR operational regulations were discussed, along with their potential impact on established practices.
The discussion paper was to ‘stimulate discussion and invite comment’ from the industry and public. It outlined the objectives, background, key risks, and potential regulatory options under the proposed regulatory framework. The discussion paper acknowledged the valuable societal benefits provided by community service flights. The paper noted that full compliance with the proposed new regulations could result in community service flights becoming untenable, and therefore sought to establish an appropriate safety standard. Some of the key regulatory risks identified were varying pilot qualifications and experience, aircraft certification and maintenance standards, and pilot and aircraft selection for each flight. It was recognised that as the use of community service flights increased, these risk factors would become more significant without regulatory oversight.
At the time (2003) Angel Flight was established, it indicated to CASA that there was an expectation that 250-300 pilots would be conducting approximately 800 flights per year when fully operational. As these flights were being conducted as private flights, and were expected to constitute a small percentage of this regulated sector, CASA considered the overall risk impact was negligible, and a formal risk assessment was not conducted. In the period 2008-2017, an average of 1,686 flights per year were being conducted, and as at June 2017 a pool of 3,180 volunteer pilots were registered. Since that time (2003) other operators providing similar flights have also been established.
The paper identified that there was a lack of visibility of the conduct of community service flights, which in turn prevented a more informed view for evidence‑based decision making in this sector of the industry. It proposed 10 main options for consideration, ranging from administrative options through operational requirements, with the potential to combine a range of the proposed options, or consider additional options suggested through the consultation process.
The submissions received in response to the discussion paper highlighted strong opposition to the prospect of any regulatory involvement in the sector, indicating that community service flying would no longer be financially viable if any of the options were applied. Based on the submissions received, no regulatory changes were initiated, with the flights remaining as private operations with no additional regulatory requirements and no additional organisational-based risk controls.
Guidance material
CASA has developed numerous publications, videos and other education material to highlight and address the flight safety risks in private operations. Some of these included video series’ such as Weather to fly and Out ‘n’ Back, personal minimums checklists, online e-learning modules through AviationWorx, the Flight Safety Australia magazine, and safety seminars and workshops. Further, based on investigation outcomes and research studies, the ATSB also developed the Avoidable Accident series, which outlines common contributing factors to fatal accidents, and how to minimise the risks associated with these factors. Additionally, both the Aircraft Owners and Pilots Association (AOPA) Australia and United States AOPA provide education materials and training courses to their members addressing flight safety risks in private operations. The US AOPA also has material which directly addresses community service flight risks.
While no material in Australia has been specifically developed for pilots conducting community service flights, information regarding many of the flight safety risks and potential mitigating strategies is contained in information available to all private pilots.
Community service flights in the United States
Numerous organisations in the United States, generally referred to as volunteer pilot organisations, provided community service flights similar to Angel Flight Australia. All community service flights in the US are conducted as private flights. Each organisation was administered separately and operated within different geographical areas.
Regulator
United States regulations required volunteer pilot organisations to apply for exemptions if the flights included reimbursement of some or all of the flight costs incurred.[24] These exemptions relate to the fact that these community service flights are conducted as private flights, but compensation is received, resulting in the pilot paying less than their pro rata share of the operating expenses for that flight. They allowed the volunteer pilot of a charity organisation to be reimbursed some or all of the costs associated with the private flight. In doing so, these exemptions added operational limitations to manage risks associated with these types of flights.
Having assessed the volunteer pilot organisation submissions and identified regulatory risks, the United States aviation regulator, the Federal Aviation Administration (FAA), issued exemptions that contained conditions and limitations intended to raise the level of safety for these flights. Additional clarification of the FAA position was provided through the publication of a policy on community service flights (charitable flights) in February 2013. The policy outlined that this activity can be conducted safely by applying limits to organisations, pilots and aircraft, with the limitations outlined in the exemptions issued to each organisation. The requirements and operational considerations differ to some extent for each organisation, however all impose additional requirements in the following areas:
pilot qualification and training programs
minimum pilot qualifications
documentation for each pilot and mission flown
mandatory passenger briefings
higher aircraft airworthiness requirements
higher instrument flight rules operational minima (where applicable).
The FAA continuously updates these exemptions for each charity as necessary to best ensure these operations meet the required level of safety.
Identified community service flight risks
The United States NTSB investigation of four accidents in 2007 and 2008, which occurred during community service flights, resulted in three safety recommendations addressed to the Air Care Alliance (ACA)[25] in 2010. The safety recommendations[26] addressed the following aspects:
The need to verify pilot currency prior to each flight.
A requirement to inform passengers that the flight would not be conducted under the same standards that apply to a commercial flight.
To develop, disseminate and implement written safety guidance, best practices, and training material addressing, at a minimum, aeronautical decision making, proper pre-flight planning, pilot qualification, training and currency, and self-induced pressure.
These areas were identified by the NTSB as increasing the risk of incidents and accidents involving community service flights.
While it was acknowledged that there was some constraint in the ability to address safety issues that are the responsibility of the PIC, it was also recognised that volunteer pilot organisations could provide tools to assist with making better decisions. In correspondence regarding the NTSB safety recommendation A-10-104, the ACA stated:
ACA seeks to strike that balance between leaving all decision making in the hands of the pilot in command, while still providing the tools through the [Volunteer Pilot Organisations] to assist them to make better decisions. The intent is to rely on the [Federal Administration Regulations] for requirements but also to provide the pilots with the tools to assess what is reasonable for their level of proficiency and the demands of the flight to be undertaken.
In response to these recommendations, and in conjunction with the Aircraft Owners and Pilots Association (AOPA) Foundation’s Air Safety Institute (ASI),[27] the online training course Public benefit flying: Balancing safety and compassion was developed. The course focused on pressures and risks associated with these flights, and included mitigation strategies to manage them. Some of the potential additional risks to flight safety when operating community service flights identified in this course were:
managing passengers and passenger expectations
proper pre-flight planning
perceived or self-induced pressure.
For a period of time, this course, and various tools developed alongside it, were included specifically in the conditions and limitations listed in the FAA issued exemptions. However, more recently, as the FAA was not responsible for the content or quality control of the course, it has removed references to the course and tools, but added specific areas in the training program to address the identified risks. While it has been removed as a regulatory requirement, many organisations still require their pilots to complete the course, in addition to the minimum requirements contained within the relevant exemption.
The United States AOPA training course highlighted some of the areas pressure can arise from, and outlined some objective decision making strategies to assist pilots with recognising and managing these risks. A summary of each of these risks as identified in the training course is outlined below.
Managing passengers: Passengers often have limited knowledge and experience with light aircraft used in general aviation. For nervous or first time flyers, the pilot needs to be aware of and manage anxiety levels of the passengers, to ensure this does not become a distraction, particularly at critical stages of flight. For all passengers, and particularly those with little exposure to general aviation, a thorough passenger briefing can assist by outlining the forecast and expected flight conditions, discussing general aircraft safety and expected sounds during the flight, such as engine changes and gear extension/retraction, and the need for a sterile cockpit at various points in the flight. Periodically reviewing the passenger’s needs during the flight and informing them of progress can also assist in managing a passenger’s anxiety levels. If they are nervous or concerned this allows an opportunity to identify and discuss the concerns, and allows for appropriate deviations or breaks if required. Pilots should also outline go/no go decisions points and explain any back-up plans. This enables determination of suitable alternatives that meet the passenger’s needs, while not compromising flight safety. Conservative planning will help reduce any time pressures associated with delays or passengers requiring breaks during the flight. If delays are unacceptable, ensure passengers have a plan B, and maintain contact with trip co-ordinators, as they can assist in determining alternatives and help alleviate any stress felt by pilots from cancellations or delay.
Pre-flight planning: Proper pre-flight planning in the context of community service flights takes into account the additional considerations and pressures associated with this type of flying. An assessment of a pilot’s current state of physical and mental health, and their own capabilities and proficiencies is important in regard to the expected flight conditions. Development and implementation of personal minimums,[28] with requirements beyond the specified regulatory minimums, can assist in making safe, objective decisions in marginal conditions. Conservative time planning can avoid hurried passenger briefings and additional stress when delays occur. It is important to travel prepared for unexpected layovers, which may be due to unexpected weather, or passenger related instances, so that objective decision making is not influenced by a lack of preparation. Flights into unusual environments such as busy terminal areas, or less familiar airports with different procedures require thorough pre-flight planning to ensure familiarity with requirements, and for remote airports, obtaining local knowledge of weather patterns, runway layout and conditions can assist with safe decision making at times of higher workload. Pre-flight planning minimises in-flight decision errors because it removes the unforeseen element from situations that arise during the flight. Failure to carry out this prior planning can result in decisions being made under a situation of considerable stress and increases the likelihood of poor or incorrect decision making.
Perceived pressure: Perceived pressure was identified in the course as one of the biggest issues facing volunteer pilots. The pressure was often self-induced and motivated by the desire to please passengers and complete an agreed trip. Additionally, knowledge of a patient’s condition can put additional psychological pressure on the pilot, and needed to be recognised as a negative influence on objective decision making. The language used, including ‘missions’ in the context of these flights can also be interpreted that it is imperative the flight be completed. Pilots must remain aware that the volunteer flight is not an emergency. Maintaining contact with trip co-ordinators during times of delay or cancellation can help alleviate any pressure felt by the pilot in these situations.
Australian evidence of perceived pressures
In Australia, from December 2018 to January 2019, CASA sought public comment on proposed changes to community service flights. A summary of the submissions was provided in Summary of consultation on proposed safety standard – community service flights, and some submissions are available on the CASA website. The responses came from both the community and pilots, so not all respondents could comment on operational matters.
The CASA summary noted that while 10 per cent of respondents (22) commented that they believed community service flights were far more complex than other private flights, 19 per cent (42) considered there was no difference in complexity between community service flights and other private operations.
While not a specific question, some respondents discussed their views on operational pressures. Of the publically available submissions, 18 respondents, at least 12 of who were pilots who had conducted community service flights, identified that there were additional pressures and operational differences associated with this type of flying, when compared with other private flights.
Twelve respondents, including pilots who had conducted community service flights, commented that they did not believe there were any operational differences between community service flights and other private flights. For example:
Why is a community service flight different to any other private flight? The fact that a passenger may or may not know the pilot prior to the flight is irrelevant.
If I can fly people privately and the regulations deem that as being safe, I see no difference when it comes to CSFs [community service flights].
There is no difference between a PPL [private pilot licence] pilot transporting passengers from A to B for charitable purposes, and a PPL pilot transporting passengers from A to B for recreational travel.
I totally reject the suggestion that these volunteer community flights are different to any other private flight.
Why is it different to any other flight a passenger is a passenger in the non-commercial way. Also long as the pilot in command obeys the rules of there [sic] endorsements and is current.
However, as discussed above, other pilots provided submissions that show evidence that perceived pressures from community services flights do affect some pilots:
Having flown both critical EMS [emergency medical service] operations and pressured CSF flights,…. the pressures involved with CSF flights can be as great or even greater than full EMS operations, as the aircraft are usually single engine, the operation is single pilot, crewed by less competent and lower time pilots and at times, it is obvious that the passengers on the CSF flights are critically ill.
There have been too many incidents involving flights where passengers are in need to arrive at a medical appointment by a certain deadline which imposes the need to get them there by the pilot. These pressures can force pilots to fly in conditions that they would normally not operate in, and inexperienced pilots can and do find themselves in situations they should not be in. As a charter pilot ….
I think the nature of this flying - the transport of medically fragile patients and dealing with emotive relatives could benefit from a training package. It should cover special considerations for the transport of people with differing conditions in the aviation environment, medical divert considerations, mission pressures (patient having an episode etc).
Managing non aviation strangers with medical needs and often in less than perfect weather is an order of magnitude of difference from typical private ops with family when you choose to fly in perfect VFR weather, and have the option to change or cancel the flight if the weather deteriorates - and your family understands that. Saying no to strangers who need to get to medical treatment is hard.
Carrying pax [passengers] who are not your friends is a huge change for the average PPL.
The psychological factors for the pilot of you must not let vulnerable people down and of doing good work, helping sick disadvantaged people... The irresistible conclusion is that any CSF flight involving long distance transport of ill patients and patient family member has a complexity beyond any normal private flight.
There is an increased sense of responsibility carrying people who you may have never met before and a possible self imposed pressure to meet what might be seen as a commitment. It could be argued that the reason for VFR into IMC is the pressure of ‘having’ to get someone somewhere at a particular time. I would agree that is possible.
Although it is almost certain that at least some pilots at least some of the time have experienced operational pressures from community service flights that were beyond what is usually experienced during other private operations, the extent of this is difficult to determine. The ATSB considered conducting a survey of Angel Flight pilots to determine the extent of perceived operational pressure on Angel Flight pilots. However, this was not conducted for the following reasons:
Obtaining accurate responses to questions designed to elicit insights into a pilot having experienced implicit social pressures depends on their awareness of it having happened. In that case, the validity of answers pilots give will be limited as some will only indicate an absence of awareness of their susceptibility to these influences rather than an absence of these influences.
The social desirability of admitting to have been influenced by goals other than those of safety may be a challenge for some pilots.
Due to publicity surrounding potential regulatory changes for community service flights after this accident (described above), there was a potential for some responses to be biased, either in an attempt to protect the reputation of Angel Flight, or to advocate for additional oversight or regulation.
A large number of responses would need to be gained across a representative sample of Angel Flight pilots to allow for valid statistical tests to be conducted.
Safety occurrences during flights organised by Angel Flight Australia
The per flight risks associated with Australian community service flights[29] had not been established prior to this investigation. Two fatal accidents occurring on passenger-carrying flights organised by Angel Flight suggested that further understanding of the nature of non-fatal occurrences was necessary, to identify if differences with other private operations existed. Similarly, it would also identify if any differences could provide context to potential systemic safety concerns that may be present during Australian community service flights.
The risk to passengers on community service flights was a particular focus of this analysis. This is because the ATSB’s focus is on the risk to travelling public[30] and Angel Flight passengers are regarded by the ATSB as being consistent with this statement, as supported by Recommendation 2 of the Australian Senate Inquiry completed 23 May 2013.[31] However, an additional assessment of non-passenger carrying repositioning flights (flights to or from the pilot’s base prior to and following passenger carrying flights) was conducted to provide further context to the risk profile of these operations.
The analysis presented in the following section was focused on establishing a baseline of the safety risks associated with these flights. As noted above, twice the number of respondents believed that community service flights have no additional complexity to other private operations than respondents who believed they introduced additional complexities. However, Angel Flight stated that there are differences in the operational environments for many Angel Flight organised flights compared to other private operations. This analysis was intended to establish if there were differences and identify if there are any areas where Angel Flight organised flights are exposed to additional safety risks. This was conducted in order to direct efforts to improve safety, rather than to attribute blame or liability.
Safety comparison between private operations and commercial air transport
As Angel Flight conduct community service flights as private operations, an evaluation of private operations against commercial air transport (RPT and charter)[32] operations was conducted to compare the relative risk per flight. In addition to community service flights, such as Angel Flight, private operations include flights for pleasure and personal transport, parachuting operations and aerobatics. Non‑commercial flights for business are also included in this analysis. Although there are large differences between the types of flying conducted in private operations, the regulatory regime is the same, and as such, all of these operations were included to provide a holistic context of the relative risk of an accident occurring during an Angel Flight organised flight.
An ATSB research investigation published in 2010 (AR-2008-045Improving the odds: Trends in fatal and non-fatal accidents in private flying operations) reviewed trends in accidents in private flying operations in Australia. This research found that 44 per cent of all accidents, and over 50 per cent of fatal accidents in the ten years 1999-2008 were attributed to private operations, even though they accounted for less than 15 per cent of hours flown in VH-registered aircraft in Australia.
This is consistent with data used in this analysis from 2008-2017 showing that private and business operations (including flights conducted on behalf of Angel Flight) in Australia have a disproportionate number of accidents compared to commercial air transport operations relative to the number of flights conducted (Figure 8). This shows that despite conducting only 21 per cent of flights, private and business operations had 77 per cent of accidents, and 84 per cent of fatal accidents from 2008 to 2017. Further data for the number of occurrences, flights and flight hours in each category are in Table B1 of Appendix B – Additional data.
Figure 8: Number of flights and accidents in private and air transport operations as a percentage of all air transport and private operations in Australia, 2008-2017
On average, flights conducted for private or business were at least:
five times more likely to end in an accident when compared to charter operations
more than 46 times more likely than high capacity RPT
69 times more likely than low-capacity RPT.
Furthermore, when considering fatal accidents, private and business operations were eight times more likely on average to end in a fatal accident compared to charter operations, and about 27 times more likely than low-capacity RPT. Note that there were no reported fatal accidents for high capacity RPT, and the single low capacity RPT accident (AO-2010-019) was during training with no fare-paying passengers on board.
Identification of Angel Flight related safety occurrences
Safety accidents and incidents (occurrences) must be reported by pilots and others to the ATSB in line with the Transport Safety Investigation Act and Regulations. It was unknown how many safety occurrences related to Angel Flight operations prior to this analysis, because safety occurrences were not always reported as involving a flight conducted for Angel Flight (nor were these required to be). To enable a safety comparison between Angel Flight and other types of operations, Angel Flight related occurrences needed to be identified. To achieve this, the ATSB obtained flight records from Angel Flight, which included departure and arrival locations, date and time of departure, and aircraft registrations covering the period between 2005 and 2017. Flights hours were not provided. Only data for the passenger carrying flights was provided, and Angel Flight was unable to provide data from 2003 and 2004.
Identification of occurrences relating to flights prior to, during and following privately conducted passenger carrying flights was performed by comparing the records provided by Angel Flight Australia and ATSB safety occurrence records. The identification process is described in Appendix A – Data analysis methods. A summary of each occurrence is located in Appendix C – Angel Flight occurrence summaries.
Through comparison with the ATSB aviation occurrence database, Angel Flight records served two primary purposes, to:
identify safety accidents and incidents that occurred on passenger carrying flights (and repositioning flights) organised by Angel Flight
calculate the likelihood of accidents and incidents per flight organised by Angel Flight.
A total of four accidents and 52 incidents were identified as occurring on 16,451 passenger carrying private flights conducted on behalf of Angel Flight between 2005 and 2017. A further 21 incidents prior to the passenger carrying flight and 28 incidents following passenger carrying flights were also identified.
For the purpose of the analysis, data from the most recent 10 years was used, from 2008-2017.[33] During this time, there were 47 Angel Flight occurrences identified from a total of 13,389 flights conducted as passenger carrying private flights. Of the 47, four were accidents (two of which resulted in fatalities, including this accident), and 43 were reportable safety incidents. This equated to about one occurrence every 2 and a half months between 2008 and 2017. Furthermore, during repositioning flights, 16 incidents and one serious incident were identified in flights prior to, and 21 incidents were identified in flights following passenger carrying flights conducted for Angel Flight during this period.
Normalisation for comparison of Angel Flight operations with others
The number of safety occurrences per 10,000 flights was used as the primary means for comparison of Angel Flight safety occurrences and other operations. Referred to as normalisation, dividing the number of occurrences by flights allows for comparisons between groups even when the overall level of activity differs between the groups.
As stated in the ATSB’s annual Aviation occurrence statistics report,[34] aircraft flights (or departures) are widely used as a measure of exposure, that is, the opportunity for an event to occur within a certain amount of flying activity. Flights were the appropriate normaliser for this analysis, as the focus was on the likelihood a passenger would encounter a safety occurrence during a flight. The number of flights are also generally considered a more appropriate normaliser measure than hours flown, as most accidents occur either during the approach and landing or departure phases of flight.[35] As such, flights are usually used for operational safety analysis by the ATSB and others (for example, the annual International Civil Aviation Organization Safety Report[36]). A further description of the rationale behind this selection can be found in Appendix A – Data analysis methods.
To allow comparison against other operations, data on flight hours and the number of flights in each operation was obtained from the Bureau of Infrastructure, Transport and Regional Economics (BITRE). The number of flights for private (including business), and charter operations was calculated by combining reported data from 2014 to 2017, and estimated data between 2008 and 2013. BITRE data between 2008 and 2013 was only available in-flight hours for each operation, with only an aggregated number of flights per year known for each aircraft. The estimation process for the earlier data is detailed in Appendix A – Data analysis methods.
For the purposes of this analysis, accidents involving passenger carrying[37] community service flights organised by Angel Flight were considered separately to accidents involving other private operations. The objective of this analysis was to understand the risk to passengers per flight.
Figure 9 shows the number of accidents, fatal accidents and fatal injuries per 10,000 flights for privately conducted passenger carrying flights organised by Angel Flight, commercial air transport, and remaining private operations. The number of flights in each category were used to identify the relative likelihood of accidents occurring per flight. Further data for the categories shown in Figure 9 can be found in Table B1 of Appendix B – Additional data.
Based on the two fatal accidents[38] occurring within 13,389 privately conducted passenger carrying Angel Flights between 2008 and 2017, statistical analysis showed it is very likely[39] that there is an increased likelihood of a fatal outcome during a community service flight conducted on behalf of Angel Flight compared to other private operations, and almost certainly higher than all commercial air transport. This indicates that it is almost certain that the nature of passenger carrying Angel Flight operations differ from the other operations, and that these differences have resulted in the higher likelihood of a fatal accident per flight. The average likelihood of a fatal accident involving an Angel Flight organised passenger carrying flight was more than seven times higher than other private flights (purple bars in Figure 9).
The accident rate per 10,000 flights in Angel Flight passenger carrying operations was likely39 to be greater than other private operations, with almost three accidents per 10,000 flights for Angel Flight operations compared to about 1.5 accidents per 10,000 flights in other private operations (yellow columns in Figure 9).38 The accident rate per 10,000 flights for both private operations for Angel Flight and other private operations were considerably higher than commercial air transport.
Figure 9 shows further comparisons between the different operational categories of the accident and fatal accident rates.
Figure 9: Total accidents, and fatal accidents and injuries, by type of operation per 10,000 flights in Australia between 2008 and 2017
Passenger carrying community service flights organised by Angel Flight always carried at least one passenger. Consequently, more people were likely to be exposed to the risk of a fatal injury during an accident involving an Angel Flight compared to other private operations (pink bars of Figure 9). As the two fatal accidents involving Angel Flight were not survivable, the four passenger fatal injuries between 2008 and 2017 presented a higher risk of fatal injury per flight than all other operations compared (blue bars of Figure 9). The average exposure to passenger fatality per flight was 98 times higher than charter operations, and there were no fatal injuries recorded for passengers in high or low capacity RPT.
Compared to other private flights, the passenger fatal injury rate per flight was 21 times higher for flights conducted on behalf of Angel Flight. This was driven by both the higher average occupancy of Angel Flight fatal accidents (2 passenger fatal injuries in each fatal accident) compared to other private flights (0.7 passenger fatal injuries per fatal accident) and higher fatal accident rate compared to other private operations, and is expected to represent an ongoing increased risk.
Characteristics of passenger carrying Angel Flight occurrences
All safety occurrences reported to the ATSB are classified in accordance with the ATSB’s three-tiered safety occurrence taxonomy.[40] Due to the relatively smaller number of Angel Flight occurrences, the statistical analysis conducted focussed on the second tier types of occurrences. The number of occurrences in each occurrence type category were calculated for Angel Flight and other private occurrences for comparison. Further details can be found in Appendix A – Data analysis methods.
Privately conducted passenger carrying community service flights organised by Angel Flight had an average likelihood of 35 occurrences23 per 10,000 flights based on the 47 safety occurrences (4 accidents and 43 incidents) between 2008 and 2017. This was considerably higher than other private operations with an average of seven occurrences per 10,000 flights.
Due to the disproportionate average rate of safety occurrences per flight in comparison to other private operations, an in-depth analysis was conducted. The aim was to identify if any systemic trends existed within Angel Flight operations that may provide opportunities for safety improvement, by identifying and explaining the more common types of occurrences contributing to the higher rate of safety occurrences.
To aid this process, statistical comparisons between passenger carrying Angel Flight operations and other private operations were conducted for the different types of occurrences.[41] Figure B1 in Appendix B – Additional data shows the main groups of reported occurrences for Angel Flight passenger carrying flights between 2008 and 2017. A complete list of results showing all differences in types of occurrences between reported Angel Flight occurrences and other private operations are shown in Appendix B – Additional data tables B2 to B7.
The following areas were identified where Angel Flight occurrences were disproportionately higher[42] than other private operations per flight, and are displayed in Figure 10:
runway events – incursions and landing/departing on the wrong runway
Figure 10 illustrates the rate of each category of reported occurrences per 10,000 flights for Angel Flight flights (shown in blue), and other private operations (shown in red). Numbers above each column are the total number of occurrences identified for each operation category.
Figure 10: Largest statistical differences between occurrence type categories where passenger carrying Angel Flight operations were greater than other private operations, 2008-2017, as a rate per 10,000 flights (numbers indicate number of occurrences)
Runway events included runway incursions, and landing, departing or approaching the wrong runway, at times resulting in consequential missed approaches for other aircraft.
Communication breakdown occurrences included incorrect read backs, not using the correct frequency and misinterpreting verbal instructions. These occurrences resulted in loss of communication, and additional co-ordination requirements for ATC to ensure required aircraft separation is maintained.
Air Navigation Service Provider errors were also elevated in comparison to other private operations. This probably relates to flights conducted on behalf of Angel Flight entering controlled airspace relatively more often per flight compared to the collective average of other private operations. However, while elevated, the Angel Flight rate is lower in contrast to other occurrences more likely to be reported in controlled airspace, such as operational non-compliance, runway events and communications. This probably indicates that the other elevated rate of other occurrence types cannot be explained by the increased frequency of flights into these locations alone, and that other factors are likely to be present.
Flight preparation and navigation occurrences during Angel Flight passenger carrying flights included VFR into IMC, being lost or unsure of position, and flight below minimum altitude. These types of occurrences were notable due to being identified in both fatal Angel Flight accidents. Further, VFR into IMC accidents result in a fatal accident in a quarter of the instances reported to the ATSB. Air traffic control (ATC) provided assistance in other cases, to assist in vectoring aircraft out of cloud or to provide navigational assistance. The risks to flight safety for these types of occurrences are significant, and discussed in Risks of flying in areas of reduced visual cues above.
Airspace related occurrences included entering controlled airspace without a clearance (airspace infringements), not maintaining assigned altitudes or headings and not complying with published procedures or verbal instructions (operational non-compliance), and flying too close to other aircraft (aircraft separation). Operational non-compliance and airspace infringement occurrences all resulted in an additional safety event, such as an additional workload for ATC to maintain separation standards, loss of separation, and diversion of other traffic.
Airframe‑related issues predominantly involved landing gear indications and included mechanical faults resulting in landing gear not retracting, landing gear failure to extend, and gear indication failures or misinterpretation. One of these occurrences resulted in the collapse of the undercarriage on touchdown, and substantial damage to the aircraft.
Although Figure 10 shows occurrence type categories where flights conducted on behalf of Angel Flight were statistically more likely compared to other private operations, there were a number of occurrence categories that were similar or less likely. Most notably, powerplant and propulsion issues, in particular engine failures or malfunctions, were considerably lower in flights conducted on behalf of Angel Flight compared to other private operations. Fuel related occurrences were also relatively lower in flights conducted on behalf of Angel Flight compared to other private operations, driven mainly by the absence of fuel starvation. All areas of comparison are shown in Appendix B – Additional data tables B2 through to B7 and are grouped by categories shown in Figure B1.
The considerably higher rate of safety occurrences during passenger carrying flights organised on behalf of Angel Flight compared to other private operations is likely indicative of a different overall operational environment. The occurrence category comparison indicated that it is almost certain that additional operational risk factors are present in Angel Flight community service flights. In particular, this is shown by relatively more occurrences related to runway events, airspace related issues, communications, flight preparation and navigation and airframe issues. Analysis of the occurrences indicated that they were not attributed to a small number of pilots, rather, that the occurrences are spread across the volunteer group, with many pilots having similar, single occurrences, and therefore probably due to broader systemic issues, rather than a small subset of pilots within the Angel Flight group.
Angel Flight repositioning flights occurrences
While passenger carrying Angel Flight occurrences were the focus of the analysis, the elevated occurrence categories identified in the repositioning flights analysis were consistent with the passenger carrying flight analysis, with the comparative data presented in Appendix B – Additional data.
While the occurrence rate was not as elevated as the passenger carrying flights, the repositioning flights were elevated in comparison to other private operations. The passenger carrying rate of occurrences per 10,000 flights was more than twice as high as the non-passenger carrying rate. Furthermore, the non-passenger carrying Angel Flight occurrence rate was more than twice as high as the average of other private operations, with passenger carrying Angel Flights being more than four times higher. This indicates that each of the three groups have a different safety risk profile, with Angel Flight passenger carrying flights having the highest likelihood of a safety occurrence per flight. Results of this comparison is shown in Table B2 of Appendix B.
Consideration of alternative options
The investigation identified that on the day of the accident, there was an RPT service on the same sector (Mount Gambier to Adelaide), scheduled to depart within 15 minutes of the planned private Angel Flight. As outlined in Safety comparison between private operations and commercial air transport, RPT flights have a lower relative safety risk than private operations.
In the overview section of Angel Flight’s Health professionals flight request forms document, there is acknowledgement that regular public transport (RPT) flights between capital cities are much more economical than using light aircraft:
For long haul or capital city to capital city transfers Angel Flight does not engage our volunteer pilots as commercial flights are much more economical. Angel Flight Australia does save some funds available to cover the cost of commercial flights however we reserve these funds for use when weather conditions prevent the flight of light aircraft and the travel date is imperative.
Angel Flight did not actively consider RPT flights as a primary option where they were available, unless the flights were for capital city transfers. This was confirmed by Angel Flight, who further stated that it considered using RPT flights, other than as a back-up or for long distance compassionate flights, as inappropriate and not aligned with the model for which the charity was constituted. Angel Flight stated that its ‘policy is to use volunteer pilots wherever possible;’ RPT flights are only considered if the pilot cancels the private flight, and the passengers are located at an RPT base, the RPT flights are available, and the times suitable.
Identification of alternative options
Considering the lower relative safety risk of RPT flights, the ATSB undertook further examination of RPT alternatives and comparative sector costs. A review of all completed Angel Flight private flights was conducted to determine how often an alternative option was available. Using Angel Flight records, the review identified that between 2005 and 2017,[43] 3,669 flights were conducted using RPT (18 per cent), and 16,356[44] as private flights (82 per cent) (inner circle Figure 12). Private flights were mainly conducted in south-eastern Australia, covering the states of Victoria, south-eastern Queensland, eastern New South Wales and the south-east of South Australia (Figure 11).
Figure 11: Passenger carrying private flights flown on behalf of Angel Flight 2005-2017
Figure 12: Breakdown of regular public transport options for flights flown on behalf of Angel Flight in 2005-2017
Financial considerations of RPT use
The Angel Flight constitution quoted above determined that passengers would not have to pay for their own flights. Further, although the Angel Flight constitution allowed for pilots to be reimbursed for fuel costs ‘from time to time’, Angel Flight reported that pilots did not claim for fuel costs for between 10 and 15 per cent of completed flights. As such, at least 85 per cent of privately-operated flights on behalf of Angel Flight have come at a cost to the charity.
It was evident that RPT options were available for a considerable percentage of flights (over two-thirds of all conducted flights). However, since the service is funded by a charity, the costs involved are relevant when considering the choice between RPT and private operations. The ATSB conducted a cost-analysis of available RPT flight costs compared to the estimated fuel cost of a light aircraft (which Angel Flight provide the volunteer pilots) for the accident sector. This was determined using data provided by Angel Flight.
The two passengers involved in the accident had been flown from Mount Gambier to Adelaide (return) on two previous occasions. For each of those four flights, fuel costs had been claimed by the pilots.[45] The total fuel costs claimed of the four flights was $2,021. Angel Flight documents also included information related to ground transport times. That is, the time required to travel from the airport to the appointment and the planned return to the airport for the return flight. A review of the available RPT schedules showed that suitable return flights were available on both of those days, accounting for the additional time requirements associated with RPT travel. According to the publically available costs, economy flights on these sectors were between $175 and $250 per person per flight. For two people for two return flights, the RPT option would have cost Angel Flight between $1,400 and $2,000, comparable to the privately claimed fuel costs.
The pilot flying the accident flight had previously flown these passengers, on the same sector (one way from Mount Gambier to Adelaide), using the same aircraft with similar repositioning flights, and had claimed $361 in fuel costs. On the morning of the accident flight, two RPT departures from Mount Gambier would have had the passengers arrive in time for the scheduled medical appointment, and this had been nominated as a backup in the case of the private pilot cancelling the flight. For two passengers on the RPT flight, the potential costs would have been between $350 and $500.
As this accident sector analysis demonstrated that suitable RPT flights were available for a comparable cost for this route, the analysis was extended to other sectors flown on behalf of Angel Flight. The purpose of the analysis was to provide a generalised indication of an RPT alternative being available where data analysis had confirmed that these services had been historically utilised by Angel Flight. Where an RPT option was available, the potential costs were compared with the estimated theoretical fuel costs.
To estimate the potential fuel costs for a private flight, the Angel Flight fuel reimbursement guidelines were used. Consistent with the evidence provided, a multiplier for the repositioning flights was included in calculating the total distance flown. This was a conservative estimate, with the distance between the departure and destination pairs based on a direct route, which did not consider IFR waypoints and approaches.[46] Fuel costs were based on the average June 2017 price per litre.
RPT costs were estimated by using publically available sources, planned for a same day return trip. The daily return trip was calculated as if purchased between 4 and 7 days ahead of the planned departure, consistent with the Angel Flight required notice. These return trips were then averaged to provide an average return cost per person.
To compare the costs between an RPT and private flight it was assumed two passengers (a patient and a companion) were travelling. The cost of a private flight was then compared to the cost for two people to fly that same sector using the averaged RPT option. This analysis was conducted using the 22 sector pairs, which accounted for the highest proportion of private flights flown where Angel Flight had previously used an RPT flight. This analysis showed that for two-thirds of the assessed sectors, the average RPT costs were cheaper than the potential fuel costs for a private flight. This conservatively indicated that of the 62 per cent of private flights where RPT options had previously been used, at least an additional 15 per cent of flights could have been conducted using RPT operations for a comparable or cheaper cost than a private flight.
Other considerations regarding the suitability of RPT
Angel Flight outlined the following reasons that it considered made the use of RPT unsuitable to assist its clients to attend appointments:
The Angel Flight constitution and its policy to use volunteer pilots in private aircraft.
The volunteer drivers’ ability to assist with carry-on luggage to and from the aircraft is limited at RPT ports.
Many passengers are not located nearby commercial airports.
Many regional locations only have RPT operating on certain days, and flights may not be available on required dates.
The RPT timetabling does not allow for lengthy cross-city travel.
Additional travel time for RPT flights – check in, luggage collection (if needed), ground transport delays.
Private flights allow passengers to travel to their appointment and return home in one day, avoiding accommodation costs in major cities.
Additional parking costs apply for volunteer drivers at RPT ports.
Passenger cancellation at last minute, with associated non-refundable RPT costs.
Not all passengers are recommended to travel RPT (e.g. immunocompromised).
Number of passengers travelling.
While Angel Flight stated its objective was to use volunteer pilots in private aircraft, this policy was not documented, nor was it a requirement in its constitution. Additionally, Angel Flight’s constitution indicated that commercial taxi services could be used for ground transport. Health referrer information and passenger guidelines indicated that Angel Flight did not automatically arrange for ground transportation at the destination, and that passengers and health referrers must endeavour to arrange ground transport before requesting this service from Angel Flight. Further, this transport was only to and from the treatment facility, and did not include assistance between the passengers’ home and the originating aerodrome. Passengers were also requested to keep their luggage requirements to a minimum, due to the limited space and weight requirements of light aircraft.
As outlined in Identification of alternative options, analysis of the flight sectors indicated 62 per cent of private flights were over sectors that had previously used an RPT option, either on the same sector or with 50 km. This implied that many passengers were located near commercial airports. Additionally, 43 per cent of those flights conducted privately were conducted on an identical sector to an RPT service, indicating that there would not be additional travel requirements for the passengers. The 22 per cent of private flights reviewed had suitable daily return RPT flight options 4 or 5 days a week. Moreover, Angel Flight passenger carrying sectors were required to be completed in daylight hours; with delay at any point risking the return flight not being completed in daylight hours—a constraint that does not apply to commercial flights.
From the evidence provided approximately 35 per cent of completed flights were for passengers travelling alone, with two travellers (patient and one companion) accounting for a further 31 per cent, and about one-third of organised flights carrying three or more travellers. Of the flights flown, about 45 per cent of aircraft used by Angel Flight had a maximum capacity of three passengers, and with limited aircraft size and weight restrictions, baggage was also limited.
There was no available evidence that indicated the rate of short-notice cancellation by passengers. While short-notice cancellation may result in non-refundable RPT costs, this is dependent on the cancellation policy in place. With respect to a private flight, a potential fuel cost may be associated with the repositioning flights of a late cancellation.
The ATSB identified that there were no mechanical defects present, and that the aircraft was serviceable at the time of the accident. A review of the pilot’s medical records and postmortem examination results did not identify any acute or pre-existing medical conditions that may have contributed to the accident. In that context, the safety analysis will examine the factors that led a visual flight rules (VFR) pilot to fly into instrument meteorological conditions, land, and subsequently depart in similar conditions. In addition, identified flight safety risks related to community service flights, Angel Flight Australia risk controls, and regulatory aspects of community service flights will be discussed.
Pilot decision to depart Mount Gambier
As part of the investigation, careful consideration was given to the possible reasons behind the pilot’s decision to depart Murray Bridge, and to then land and depart from Mount Gambier Airport in instrument meteorological conditions (IMC). On departure from Murray Bridge at about 0800, the weather forecasts indicated marginal visual meteorological conditions (VMC) at Mount Gambier, but with conditions expected to improve from 0930, with the pilot’s planned arrival between 0930 and 1000. The Mount Gambier aerodrome forecast (TAF) released at 0942 also indicated marginal but improving conditions compared with the previous TAF. However, the SPECI and live weather observations available to the pilot en route indicated that the observed conditions, while improving, were not suitable for VFR. While it could not be determined if the pilot accessed this information en route, weather-related diversions were noted in the recorded flight path, and radio calls requesting the cloud base at Mount Gambier were made.
It is not known if the pilot fully comprehended the unsuitability of the weather conditions for visual flight on approach to and at Mount Gambier, or if any other options were considered. However, the following are some of the possible reasons for deciding to continue to land, rather than divert or hold, and subsequently depart. These have been outlined to highlight the risks to others, and are based on the three factors listed by the Wiegmann and Goh (2000) empirical study of factors affecting pilot decision-making relating to VFR flight into adverse weather: situation assessment, risk perception and other motivational factors.
Situation assessment
The ability to assess a situation accurately depends on a number of factors, in particular; domain knowledge based on learning, training received, flying hours, and expectations based on exposure to a variety of situations (Gawron, 2000). Wiggins and O’Hare (1995) also stated that pilots with greater practical experience were able to make more informed decisions. In this case, the ability to assess the situation accurately would have been limited by the pilot not having an instrument rating, having had limited exposure to instrument flight conditions in training, and only holding his licence for about four years at the time of the accident.
Decisions are usually made with an individual’s best intentions and based on the information they have to conduct an assessment. In this case, the pilot may have interpreted information from pilots of other aircraft on the Mount Gambier common traffic advisory frequency to indicate that a landing was plausible, when in fact the conditions were observed to be marginal even for flight under the instrument flight rules (IFR). After conducting a non-standard, high-risk approach and landing, in conditions not suitable for VFR flight, the pilot should have had enough evidence available to assess that a departure soon after would very likely result in flight in the same conditions despite his limited flying experience and training. However, there is insufficient evidence to establish whether the pilot accurately assessed the conditions.
The pilot’s assessment of the conditions prior to departure could also have been informed by checking the forecast and reported actual weather conditions, but the short duration between landing and take-off (considering passenger loading occurred in this timeframe) indicated a limited opportunity to do so.
Risk perception
A United States National Transportation Safety Board (NTSB) study (2005) outlined that ‘even if pilots are able to correctly assess current weather conditions, they may still underestimate the risk associated with continued flight under those conditions, or they may overestimate their ability to handle that risk’.
In this case, the pilot’s perception of the risk associated with departure from Mount Gambier is not known. It is known that en route to Mount Gambier, the pilot conducted weather-related track diversions, which indicated an awareness of the adverse weather in the area. However, he then conducted a non-standard approach and landed into Mount Gambier in low visibility conditions, in which he encountered difficulty in sighting and selecting a runway. He then elected to depart 12 minutes later in conditions similar to that which he arrived. It is possible he perceived that being able to land was a positive indicator for being able to depart.
Given the significant risks associated with entering IMC as a VFR pilot, it was considered unlikely that the pilot willingly flew into IMC without some assurance that he was able to handle it. However, the ability to do so depends on pilots possessing instrument proficiency. It was considered very unlikely in this case that the pilot possessed the instrument proficiency to sustain flight in the conditions encountered on the day of the accident. The ability to underestimate these risks is not exclusive to this one case; it is prevalent throughout the industry, particularly in general aviation.
Motivational factors
In addition to an assessment of the weather conditions, and perception of risk associated with this, it is possible that the pilot was influenced in his decision to take off by other motivational factors (Wiegmann and Goh, 2000). After landing in Mount Gambier and loading the passengers, the pilot was about 20 minutes later than his initial flight plan indicated. It is possible that inherent pressures associated with the purpose of the flight increased the perceived need to get to Adelaide (as outlined in the Context, Identified community service flight risks, and discussed further below in Potential for perceived pressures). Angel Flights are only offered to those who require financial and medical assistance. The pilot was aware of the medical condition of the passenger and the timing of the medical appointment, and having flown these passengers previously had knowledge of the family.
As stated at the start of this section, it is not known what influenced the pilot’s decision to approach, land and depart into IMC. The widespread nature of VFR into IMC accidents show that it is a common error in judgement, and one that should not indicate inherent failings of someone’s overall abilities as a pilot. It should be noted, however, that community service flights have a disproportionately high rate of flight preparation and navigation occurrences when compared to private operations.
Pilot proficiency for flight in instrument meteorological conditions
Although the pilot’s experience and recency were appropriate for the planned VFR flight, he was not qualified or experienced in conditions requiring instrument flying proficiency, which was what the conditions on departure from Mount Gambier required for safe flight. It was unlikely that a VFR pilot could overcome the risks posed by low visibility conditions when climbing into thick cloud (including a lack of a horizon and a loss of visual cues), and avoid experiencing spatial disorientation.
Spatial disorientation resulting from a loss of visual cues
The aircraft track recorded a departure on runway 24 and YTM entered an area of low visibility almost immediately. The recorded aircraft track then showed the aircraft slowly turning left while continuing to climb to a height of 300 ft above ground level. The last recorded position of the track indicated that the aircraft had started to descend whilst in a left turn. The aircraft wreckage indicated that just prior to impact the aircraft had been inverted.
On entry into low cloud, the pilot of YTM would have lost visual cues, in particular the horizon and visual reference to the ground. It is well established that a loss of visual cues significantly increases the risk of spatial disorientation.
The time between departure (which is also approximately the same time as entering the low cloud) and the aircraft’s impact with the ground was about 70 seconds. This is consistent with the range of times indicated by research between the loss of visual cues, experiencing spatial disorientation and a subsequent loss of control. Further evidence that the pilot of YTM experienced spatial disorientation due to the lack of visual cues included:
the aircraft’s track and height were not consistent with the expected track if a pilot were departing for Adelaide
the aircraft had started to descend while in a left turn suggesting the pilot had lost reference to the horizon
inverted state of the aircraft prior to impact indicated a loss of control.
In summary, the ATSB found that shortly after take-off, while in low level cloud, the pilot likely experienced a loss of visual cues and probably became spatially disorientated, resulting in loss of control of the aircraft and collision with terrain.
Considerations of the use of alternative options
It was established that commercial passenger flights, consisting of charter and regular public transport (RPT) have a lower risk of adverse safety outcomes than private operations. The ATSB considered whether RPT options were available for the passengers of the accident flight to travel between Mount Gambier and Adelaide for the specialist medical appointment they were attending and return home on the same day. It was determined that there were RPT options that would have the passengers arrive at their appointment in a similar timeframe, and allow them to return home on the same day. It was also determined the costs to Angel Flight to cover the fuel component for a private flight (which it did for most private flights) were comparable to the costs for two people to fly on a commercially available RPT flight.
While Angel Flight noted that RPT flights between capital cities were more economical, RPT flights were not considered as a primary option where they were available on other sectors. From the evidence available, and confirmed by Angel Flight, its ‘policy is to use volunteer pilots in private operations wherever possible’, and RPT options were only explored when there were no private pilots available to conduct the flight.
However, while Angel Flight agrees that RPT flights were not considered as a primary means of transporting passengers, it has stated that this was because such considerations would be against its constitution. The primary stated objective of the constitution was ‘Arranging carriage of financially disadvantaged people with medical conditions, in non-emergency circumstances’. This appears to be independent of whether volunteer private pilots or commercial flights were used.
The constitution’s objectives made no reference to the safety of passengers. If Angel Flight considered the safety of passengers was an important consideration to take into account, then consideration could be expected to be given to the safety benefits of using commercial passenger transport, taking into account availability, passenger suitability, and comparative costs.
The ATSB acknowledges that there will be passengers who cannot travel on RPT, and that there are times and locations where RPT is not available or suitable for the reasons outlined previously. However, where those flights are available and suitable, using the safer transport option would reduce the overall safety risk, while still achieving the stated constitutional objective of assisting people to attend medical appointments where they are not available locally.
In relation to the accident flight, while an RPT option was identified as a backup, this would only be used if the private pilot cancelled. The RPT option was not selected because the policy was to use private pilots wherever possible. No consideration was given to the safety benefits of using the available RPT, nor were the comparative costs considered. It is unlikely that any of the considerations outlined previously would have prevented the use of a commercial flight.
Risks associated with community service flights
During this investigation, the ATSB determined that per flight, the likelihood of a safety occurrence during an Angel Flight community service flight was higher than flights conducted in other private operations. Furthermore, there was an increased risk of fatal injuries in passenger carrying flights conducted by Angel Flight. This was driven by both the expected average higher occupancy of these flights compared to other private operations, and the very likely higher fatal accident rate. There was an increased prevalence of flight preparation and navigation errors in Angel Flight community service flights, compared with other private operations. This is a known precursor to fatal accidents, and was identified in both fatal accidents involving Angel Flight. It is almost certain that the risk profile associated with flights conducted on behalf of Angel Flight are not the same as other private operations. The identified occurrence type categories show that other events or conditions that increase risk are present during Angel Flight community service flights which are either not present or are effectively mitigated during other private flights.
It was considered that there would be no notable differences in the pilot skills, recency and experience, or the aircraft equipment, maintenance and reliability, as both groups are licensed and regulated in the same way.
Therefore, the ATSB considered the potential for Angel Flight pilots being exposed to factors different to other private operations associated with the key differences between the flights conducted for Angel Flight and most other private operations. The key differences are:
the carriage of ill, unrelated (and often unknown) passengers, rather than friends and family
flying at times to meet scheduled medical appointments rather than times chosen by the pilot
flying to and from pre-arranged locations, generally requiring cross country navigation and often into controlled airspace
operational costs (fuel and landing fees) of the private flight are covered by a third party.
These factors included considerations such as:
Implicit (rather than explicit) pressures of flying a ‘mission’ where the pilot is responsible for transporting unrelated passengers to necessary medical appointments.
Flying in and out of locations with which they may have limited familiarity, including small aerodromes in areas outside of ones they perhaps routinely use, and limited familiarity with procedures in controlled airspace.
Per flight, Angel Flight pilots were shown to be more likely to make operational errors (particularly associated with flight preparation and navigation, airspace, runway events, and communications breakdowns) when compared to other private operations. This required further consideration, and therefore the above topics have been explored in more detail below.
Potential for perceived pressures
The safety investigations and research conducted in the United States, and highlighted in the Aircraft Owners and Pilots Association training course Public Benefit Flying: Balancing Safety and Compassion, identified that pilots conducting community service flights may be exposed to factors that are detrimental to safe decision making. This included the identification of the potential for perceived or self-induced pressure due to the nature of the flight being undertaken, and the impact this could have on objective decision making. Key areas identified by the US research and investigations included the terminology used, feelings of personal obligation to provide a service on an assigned trip, knowledge of passenger’s condition, and managing passengers and their expectations.
Perceived or self-induced pressure is specific to each pilot, may come from a range of sources, and may not be evident or easily identifiable by the pilot. Not every flight will result in potential for pilots to experience pressure; some pilots may not have experienced pressure due to the flights they have been involved in, and some pilots may not feel pressure in circumstances where other pilots do. This is evident from submissions about personal experiences made to Civil Aviation Safety Authority (CASA) by Australian pilots during the 2018-2019 consultation on proposed changes to community service flights. Some pilots indicated they saw no differences to other private flights, while others indicated that there were significant pressures associated with community service flights consistent with the above United States investigations and research. The ATSB consider the following aspects of community service flying will likely be sources of potential pressure perceived by some pilots:
The terminology used in this sector, including referring to the flights as ‘missions’ and pilots as ‘heroes.’
Desire to complete the trip, having been assigned a ‘mission,’ when completion of such flights can lead to ‘satisfaction that cannot be described.’
Knowledge of the patient’s condition may motivate the pilot to continue when other factors may otherwise have them altering their plans.
Managing passenger expectations, when passenger briefing notes indicate an on time flight according to the scheduled times to meet the medical appointment.
Belief that there are limited other options for the passengers to attend their medical appointments.
Passenger requirement to travel to the appointment and return home in one day.
While it could be demonstrated that most of the elements outlined above were present in the accident flight, there was insufficient evidence available to determine the influence of each of these on the pilot’s decision to continue to land, and subsequently depart, rather than diverting or holding, or delaying or cancelling the flight.
It was evident through interviews with key organisational staff, and in documentation such as the Pilot Handbook, that Angel Flight does not pressure pilots to complete assigned missions. However, pilots undertaking these flights do not necessarily have the benefit of education and exposure to compelling evidence of how motivational factors can override other safety considerations when they are making decisions. They are also alone in their decision making for a ‘go/no go’ situation, unlike in other sectors where support staff and other crew influence the outcomes, and tools and procedures have been implemented to manage the identified risks.
Flight preparation and navigation
According to Angel Flight documentation, the flight times and locations of community service flights are determined by the passenger’s needs. This generally means the pilot will be flying into a small aerodrome near the passenger’s home, and then to a major city centre, with time requirements that align with the passenger’s specialist appointments.
The pilot may not be familiar with, or may not have flown to either of the locations previously, and may have limited exposure to flying into controlled airspace surrounding larger airports, as many private pilots flying recreationally are not necessarily exposed to these circumstances on a regular basis. This results in pilots flying through controlled airspace and into airports with unfamiliar layouts, while carrying passengers, which can lead to an increased workload when compared with recreational flying.
Flight in unfamiliar airspace requires additional pre-flight planning. This includes knowledge and familiarity with established procedures, radio communication protocols, the limits of restricted and controlled airspace, and airport runway and taxiway layouts. Pre-flight planning minimises in-flight decision errors because it removes the unforeseen element from situations that arise during the flight. Failure to carry out this prior planning can result in decisions being made under a situation of considerable stress and increases the likelihood of poor or incorrect decision making.
The training to obtain a private pilot licence and the aeroplane flight review conducted biannually included the operational requirements and knowledge to conduct these flights. However, while pilots may demonstrate knowledge satisfactorily during the biennial flight review, not all of these areas are tested under the flight review, and not all these skills are practiced regularly during recreational flying, potentially resulting in reduced proficiency in these skills.
In summary, the increased occurrence and fatal accident rates were almost certainly a result of community service flight pilots being exposed to a range of operational differences because of the task being undertaken. These operational differences included the carriage of passengers according to a scheduled time, with specific location requirements involving cross country navigation and flight into controlled airspace, and often with a same day return expectation. As a result of the operational differences present in these flights, some of the factors identified which may impact decision making, and consistent with the occurrence categories where the Angel Flight occurrence rate was higher, included the potential for perceived pressures, and flying in unfamiliar locations, with a resulting impact on flight safety.
Angel Flight organisational controls
The community could reasonably expect that a provision of services such as the community service flight organised by Angel Flight would have at least a level of safety commensurate with other private operations, if not higher. However, this investigation has showed that they are actually less safe than other private operations, and previous research has shown that private operations are also less safe than charter and regular public transport. When compared with private operations, this indicates that there are risk factors which are not currently being managed. Analysis of the occurrence types where the greatest differences were identified between private flights and community service flights were predominantly operational.
As community service flights are exposed to additional operational risks, it is important that those organising these flights have appropriate operational controls in place, and these pilots have access to guidance and education in what these risks are, and how to avoid adverse influences.
In the United States, in response to the NTSB recommendations, guidance related to the identified safety risks in the community service flight sector was developed to help pilots identify and minimise the flight safety risks. Additionally, for those community service flights conducted privately but with reimbursement from a volunteer pilot organisation, the Federal Aviation Administration determined these flights could be safely conducted by applying operational limitations on each organisation through their exemption process. This required organisations to ensure minimum pilot qualifications were applied, increased recency requirements and required additional training to be undertaken, and increased required flight rule minimums above the minimum required for private flights. Documentation must also be maintained for each pilot and mission flown, including in some cases a pre-flight risk assessment tool, which reinforced the organisational applied minima, to assist pilots with decision making in marginal conditions. The United States model shows that organisations like Angel Flight can sustain operations with additional operational risk controls in place to address the specific risks associated with community service flights, and which are ongoing and apply to individual flights.
At the time of this accident, similar guidance and educational material to that developed in the United States had not yet been developed for the Australian context. Although there has been material developed by CASA and the ATSB for private pilots which addressed some of the flight safety risks, these did not target pilots conducting community service flights, nor address the different operational factors present.
Angel Flight operational controls were limited to 250 hours as pilot in command, VH-registered aircraft, and 5/10 hours on aircraft type for VFR/IFR flights respectively. These are basic measures for a base line level of entry for registration as a pilot with Angel Flight. There is limited evidence flying hours alone are sufficient to make informed decisions. As outlined by Gawron (2000) and Wiggins and O’Hare (1995), pilots with greater practical experience, particularly made up of domain knowledge based on learning, training received (and its recency) and expectations based on exposure to a variety of situations, make more informed decisions. While the current licensing and endorsement requirements for private pilots ensures the flight related knowledge and skills are taught, it is also valuable for them to receive regular education, training and practice to maintain many of the skills needed to safely conduct community service flights.
In addition, the Angel Flight PilotHandbook included comments outlining a pilot’s ability to cancel a flight for any reason. It also stated that any subjects related to pilot in command responsibilities would not be covered, and that the flight must be conducted legally.
During this investigation, the ATSB found that community service flights had a higher occurrence rate, and a different risk profile than other private operations, almost certainly due to exposure to different operational factors which influence decision making. This higher occurrence rate indicated that insufficient organisational controls had been implemented to address the risks to flight safety.
Under the current regulatory framework, there is no specific oversight of community service flights. Therefore, organisational controls to address the areas of elevated risk can only be implemented by the community service flight organiser. Similarly, only the community service flight organiser can undertake the targeted promotion of relevant material to its pilots.
The ATSB acknowledges that Angel Flight cannot be responsible for the pilots’ preparation and conduct of flights, and is limited in its ability to address decisions that are the responsibility of the pilot in command. However, the ATSB considers that Angel Flight is in a position to implement organisational requirements and controls, and to facilitate access to material and relevant information that can assist pilots to identify risk factors associated with these flights. Pilots would then have an increased opportunity to develop and implement appropriate mitigation strategies to address these risks.
Availability of safety information to Angel Flight
It is well-understood in the aviation industry that ‘the effective management of safety is highly dependent on the effectiveness of safety data collection [and] analysis...’ and that ‘reliable safety data and safety information is needed to identify trends, make decisions and evaluate safety performance…and to assess risk’ (International Civil Aviation Organisation (ICAO), 2018). Identifying and collecting this data should be aligned with the organisations’ role and scope of influence.
The nature of safety information in this context relates to any hazards or occurrences that arise during a pilot’s Angel Flight mission. The utilisation of safety information by an organisation like Angel Flight will differ significantly from aviation operators responsible for the management of flight operations. By identifying these hazards or occurrences, it can inform decisions about future pilot requirements, any guidance or educative material that could be helpful, or any other risk treatment measures possible within the scope of Angel Flight’s role.
At the time of the accident, occurrence notifications from pilots, air traffic control and aerodrome personnel received by the ATSB and CASA were reported as private flights, and generally were not further identified as community service flights; nor were they required to be. As these notifications were not identified as community service flights, neither CASA nor the ATSB had awareness of the incidents as occurring during community service flights, and further, the ATSB public database could not differentiate these occurrences from other private operations, and so community service flight organisations did not have visibility of these occurrences.
Angel Flight did not request or require any information regarding flight safety related incidents from its pilots. Therefore, the only way for Angel Flight to be aware of a safety occurrence apart from when the organisation was formally investigated as part of an ATSB investigation, was for the pilot, passenger(s) or other involved person to report it directly. This informal system was limited in the ability to capture safety related information because:
the passengers likely have limited knowledge or exposure to general aviation regulations or knowledge of flight safety
in the absence of an established just culture policy[47] in relation to reporting of safety occurrences, pilots may be reluctant to report a safety occurrence to Angel Flight as they may perceive it would have implications for being considered for future missions
other involved persons may not be aware the private flight is a community service flight
if pilots are not specifically asked or required to provide information on safety matters, there is a reduced likelihood that they will consider it necessary to do so.
Where Angel Flight had been notified of incidents or accidents, further information had been requested, and in some cases, additional action taken for specific pilots. However, this was limited to the known incidents which constituted less than 10 per cent of occurrences identified during this investigation. If Angel Flight had sought to identify and understand systemic risks relating to flights conducted on behalf of the charity, the limited availability of safety related information to Angel Flight would have prevented this. However, it must also be noted that where punitive action has been known to be taken, this increases the risk of non-reporting to the organisation. This is due to well recognised concerns amongst pilots that reporting errors results in subsequent punitive action. It also does not allow for identification of, or address the broader systemic risks, which are present in all privately conducted flights on behalf of Angel Flight. This in turn prevented Angel Flight from identifying and applying appropriate risk controls to manage the safety risks associated with these flights.
Regulatory differentiation between community service flying and private operations
In order to identify risks and monitor safety performance of any one sector of the industry, it is necessary to have systems to differentiate the sector from other similar activities. In Australia, the regulator facilitates this.
CASA had previously identified key regulatory risks applicable to community service flights and outlined potential mitigation methods, which were communicated to the public and industry through a discussion paper in 2014. Many responses to the discussion paper indicated there was no evidence to support the need for additional oversight; however, as identified in the discussion paper, there was a lack of visibility of the conduct of community service flights (as they were considered private operations). Due to the predominantly negative responses, no regulatory changes were initiated, and the flights remained as private operations. This prevented a more informed view for decision making in this sector of the industry, as lack of identification or differentiation of the flights from other private operations prevented the regulator identifying ongoing areas of sector specific concern.
At the time of the accident, there were no legislated minimum qualifications or experience requirements for community service flights. While not required by regulation, organisations providing community service flights are able to apply their own risk controls; for example, Angel Flight applied requirements of minimum pilot in command hours and VH‑registered aircraft. Other organisations coordinating community service flights also specified minimum requirements for their volunteer pilots, which differed substantially between each organisation. However, these risk controls were voluntary and unregulated, and were applied by each organisation to address organisational identified risks. Where organisations are not aviation operators, organisational controls required to identify or address flight safety risks associated with these flights, and they can be altered or removed with no reference to external parties or the regulator.
A system to differentiate these flights would allow for ongoing oversight and review of the safety of these flights. This would allow for the identification of areas of specific concern through evidence-based analysis, and consideration of appropriate risk controls to be applied to all organisations offering community service flights.
A previous fatal accident involving Angel Flight in 2011 was as a result of VFR flight into low visibility conditions. The lack of visibility of community service flights in occurrence data made quantifying the risk by Angel Flight, CASA and the ATSB not possible. However, analysis from data obtained under the Transport Safety Investigation Act 2003 for this investigation shows that flight preparation and navigation related occurrences are over‑represented in Angel Flight operations relative to other private operations. If community service flights could have routinely been identified in the ATSB occurrence database, this analysis could have been part of routine safety analyses by CASA. Such analysis could have demonstrated that there were ongoing additional risks faced by Angel Flight pilots beyond those faced by other private pilots, and provided the justification for mitigating those risks. As discussed, the additional risks such as perceived pressure to complete missions can have a strong influence on pilot decision making, resulting in decisions to operate in marginal weather conditions. Decisions made by the pilot of YTM that resulted in VFR flight into IMC leading to this fatal accident were consistent with risks apparent in the data.
From the evidence available, the following findings are made with respect to the loss of control and collision with terrain involving a SOCATA TB-10 Tobago aircraft, registered VH-YTM, that occurred near Mount Gambier Airport, South Australia, on 28 June 2017. These findings should not be read as apportioning blame or liability to any particular organisation or individual.
Safety issues, or system problems, are highlighted in bold to emphasise their importance. A safety issue is an event or condition that increases safety risk and (a) can reasonably be regarded as having the potential to adversely affect the safety of future operations, and (b) is a characteristic of an organisation or a system, rather than a characteristic of a specific individual, or characteristic of an operating environment at a specific point in time.
Contributing factors
The pilot took off from Mount Gambier into low-level cloud without proficiency for flight in instrument meteorological conditions.
Shortly after take-off, while in low-level cloud, the pilot likely experienced a loss of visual cues and probably became spatially disorientated, resulting in loss of control of the aircraft and collision with terrain.
Angel Flight did not consider the safety benefits of commercialpassenger flights when suitable flights were available. [Safety Issue]
Other factors that increased risk
Community service flights conducted on behalf of Angel Flight had considerably more occurrences per flight than other private operations. It is almost certain this higher occurrence rate is due to exposure to different operational factors as a result of the task being undertaken.
Angel Flight had insufficient controls in place, and provided inadequateguidance to pilots to address the additional operational risks associated with community service flights. [Safety Issue]
There were limited opportunities for Angel Flight to be made aware of any safety related information involving flights conductedon itsbehalf. [Safety Issue]
The Civil Aviation Safety Authority did not have a system to differentiate between community service flights and other private operations, which limited itsability to identify risks. This hindered the Civil Aviation Safety Authority's ability to manage risks associated with community service flights.[Safety issue]
Safety issues and actions
The safety issues identified during this investigation are listed in the Findings and Safety issues and actions sections of this report. The Australian Transport Safety Bureau (ATSB) expects that all safety issues identified by the investigation should be addressed by the relevant organisation(s). In addressing those issues, the ATSB prefers to encourage relevant organisation(s) to proactively initiate safety action, rather than to issue formal safety recommendations or safety advisory notices.
Depending on the level of risk of the safety issue, the extent of corrective action taken by the relevant organisation, or the desirability of directing a broad safety message to the aviation industry, the ATSB may issue safety recommendations or safety advisory notices as part of the final report.
All of the directly involved parties were provided with a draft report and invited to provide submissions. As part of that process, each organisation was asked to communicate what safety actions, if any, it had carried out or were planning to carry out in relation to each safety issue relevant to its organisation.
Descriptions of each safety issue, and any associated safety recommendations, are detailed below. Click the link to read the full safety issue description, including the issue status and any safety action/s taken. Safety issues and actions are updated on this website when safety issue owners provide further information concerning the implementation of safety action.
Angel Flight Australia consideration of commercial flights
Safety issue description: Angel Flight did not consider the safety benefits of commercial passenger flights when suitable flights were available.
Safety recommendation description: The Australian Transport Safety Bureau recommends that Angel Flight Australia takes action to enable it to consider the safety benefits of using commercial flights where they are available to transport its passengers.
Insufficient organisational risk controls implemented by Angel Flight Australia
Safety issue description: Angel Flight had insufficient controls in place, and provided inadequate guidance to pilots to address the additional operational risks associated with community service flights.
Availability of safety information to Angel Flight Australia
Safety issue description: There were limited opportunities for Angel Flight to be made aware of any safety related information involving flights conducted on its behalf.
Regulatory differentiation between community service flying and private operations
Safety issue description: CASA did not have a system to differentiate between community service flights and other private operations, which limited its ability to identify risks. This hindered the Civil Aviation Safety Authority's ability to manage risks associated with community service flights.
Additional safety actions
Whether or not the ATSB identifies safety issues in the course of an investigation, relevant organisations may proactively initiate safety action in order to reduce their safety risk. The ATSB has been advised of the following proactive safety action in response to this occurrence.
Civil Aviation Safety Authority
A legislative instrument imposing conditions on pilots conducting certain non-emergency medical community service flights arranged by third party organisations (CASA 09/19 — Civil Aviation (Community Service Flights — Conditions on Flight Crew Licences) Instrument 2019) was made on 12 February 2019 and came into force on 19 March 2019.
The instrument sets out new minimum licence, experience and recency standards for pilots operating community service flights that are conducted by volunteer pilots and coordinated by a charity or for a charitable or community service.
Community service flights are flights:
where patients and their families or carers are transported
to a destination for non-emergency medical treatment or services; or
from the treatment destination back to the place from which they departed or to a destination where they reside; and.
medical treatment is not provided on board a community service flight, passengers can receive medication and treatment for an unexpected medical emergency; and
no more than five passengers can be carried, including the patient; and
cannot be operated under the visual flight rules (VFR) at night.
In addition to the above requirements, community service flight requirements include:
licence must be PPL CPL or ATPL (not RPL)
for a multi-engine aeroplane, at least 25 hours of flight time as pilot in command of a multi-engine aeroplane
for PPL holders only, at least 400 hours of flight time and at least 250 hours of flight time as pilot in command (does not apply to CPL/ATPL holders)
a current class 1 or 2 medical certificate
for a flight conducted under the VFR, pilots must have at least 10 hours of flight time in an aeroplane of the same type as being used for the Community Service Flight
for a flight conducted under the IFR, pilots must have at least 20 hours of flight time in an aeroplane of the same type as being used for the CSF
landed the same class rated or type rated aeroplane within the previous 30 days
aircraft maintained to the CASA maintenance schedule must have a current maintenance release with a periodic inspection conducted every 100 hours or 12 months (whichever is earlier).
A community service flight cannot be flown in:
an amateur-built aircraft accepted under an Amateur Built Aircraft Acceptance
The sources of information during the investigation included:
Angel Flight Australia
The Civil Aviation Safety Authority
Witnesses
The Bureau of Meteorology
Airservices Australia
Bureau of Infrastructure, Transport and Regional Economics
Federal Aviation Administration
Air Care Alliance
National Transportation Safety Board
References
ATSB 2011, Avoidable Accidents No. 4 Accidents involving pilots in Instrument Meteorological Conditions, Australian Transport Safety Bureau, Aviation Research and Analysis publication AR-2011-050.
Batt, R and O’Hare, D 2005, General aviation pilot behaviours in the face of adverse weather, Australian Transport Safety Bureau, Aviation Research and Analysis Report B2005/0127
Benson, A (1999) Spatial disorientation – general aspects. In J Ernsting, AN Nicholson, DJ Rainford (Eds.) Aviation medicine (pp.419-436). London: Butterworths & Co. Ltd.
Bryan, L., Stonecipher, J., & Aron, K. (1954). 180-degree turn experiment (Vol. 54(11), pp. 1-52): University of Illinois Bulletin.
Cheung, B. (2004). Nonvisual spatial orientation mechanisms, in FH Previc & WR Ercoline (Eds.) Spatial disorientation in aviation, Lexington MA, American Institute of Aeronautics and Astronautics, pp. 37-94.
Frederick, M 2002, AOPA Air Safety Foundation. 2002 Nall report: Accident trends and factors for 2001: AOPA Air Safety Foundation.
Gawron, V 2000, ‘Psychological factors’, in FH Previc & WR Ercoline (Eds.) Spatial disorientation in aviation, Lexington MA, American Institute of Aeronautics and Astronautics, Inc, pp. 145-195.
Gibb, R, Gray, R and Scharff, L 2010, Aviation Visual Perception: Research, Misperceptions and Mishaps, Ashgate Publishing Limited, Surrey, United Kingdom.
Groff, LS & Price, JM 2006, ‘General aviation accidents in degraded visibility: A case control study of 72 accidents’, Aviation, Space, and Environmental Medicine, vol. 77, pp. 1062–7.
Newman, DG, 2007, An overview of spatial disorientation as a factor in aviation accidents and incidents, Australian Transport Safety Bureau, Aviation Research and Analysis Report B2007/0063.
NTSB 1988, Commercial emergency medical service helicopter operations, National Transportation Safety Board Safety Study NTSB/SS-88-01, Washington DC, United States.
NTSB 1989, Safety report: General aviation accidents involving visual flight rules flight into instrument meteorological conditions, National Transportation Safety Board NTSB/SR-89-01, Washington, DC, United States
NTSB 2005, Risk Factors Association with Weather-Related General Aviation Accidents, National Transportation Safety Board Safety Study NTSB/SS-05/01, Washington DC, United States.
Parson, S. (2006, May/ June). Getting the Maximum from Personal Minimums. FAA Aviation News, 1-8.
Transportation Safety Board of Canada. (1990). Report of a safety study on VFR flight into adverse weather (90-SP002.). Gatineau, Canada: Transportation Safety Board of Canada.
Wiegmann, D and Goh, J 2000, Visual Flight Rules (VFR) Flight into Adverse Weather: An Empirical Investigation of Factors Affecting Pilot Decision Making, Federal Aviation Administration research DTFA 00-G-010, Illinois, United States.
Wiggins, M and O’Hare, D 2003, Weatherwise: Evaluation of a cue-based training approach for the recognition of deteriorating weather conditions during flight, The Journal of Human Factors and Ergonomics Society, pp.337-345.
Wiggins, M and O’Hare, D 1995, Expertise in Aeronautical Weather-Related Decision Making: A Cross-Sectional Analysis of General Aviation Pilots, Journal of Experimental Psychology: AppliedVol. 1 No. 4, pp. 305-320.
Submissions
Under Part 4, Division 2 (Investigation Reports), Section 26 of the Transport Safety Investigation Act 2003 (the Act), the Australian Transport Safety Bureau (ATSB) may provide a draft report, on a confidential basis, to any person whom the ATSB considers appropriate. Section 26 (1) (a) of the Act allows a person receiving a draft report to make submissions to the ATSB about the draft report.
A draft of this report was provided to the Civil Aviation Safety Authority, Angel Flight Australia, the Bureau of Meteorology, the National Transportation Safety Board, and Bureau of Infrastructure, Transport and Regional Economics.
Submissions were received from the Civil Aviation Safety Authority, Angel Flight Australia, the Bureau of Meteorology, the National Transportation Safety Board, and Bureau of Infrastructure, Transport and Regional Economics. The submissions were reviewed and where considered appropriate, the text of the report was amended accordingly.
Appendices
Appendix A – Data analysis methods
Identification of Angel Flight occurrences
The ATSB undertook a data matching exercise between Angel Flight Australia (Angel Flight) records and the ATSB’s aviation occurrence database to find safety occurrences that occurred during an Angel Flight organised private flight. A number of techniques were employed to identify Angel Flight occurrences recorded as other operations, and provide assurance that the occurrence data was related to passenger carrying Angel Flights.
A total of 4,434 ATSB occurrence records were identified as having a registration match with Angel Flight used aircraft. To identify those records that occurred during flights conducted on behalf of Angel Flight, the following techniques were applied. Twenty-four ATSB occurrence records already identified as a flight operated for Angel Flight were also validated using these techniques and removed from analysis if a positive match could not be identified.
An evaluation was conducted by matching Angel Flight and ATSB occurrence records on the following parameters: departure aerodrome, arrival aerodrome, aircraft registration (country and registration mark), within the same day. The time difference between the Angel Flight recorded departure time and the occurrence time was recorded and used for ranking and assessment purposes. Ninety-two distinct occurrence records were identified using this technique.
Occurrence location name matching
A probable airport for each of the 4,434 potential occurrence locations were identified. Matches were performed on the following parameters: departure and arrival aerodrome with occurrence location name according to aircraft phase of flight and flight plan details; time within 6 hours. The time difference between the Angel Flight time and occurrence time was recorded for validation. Twenty-four distinct occurrences were identified for further review.
Spatio-temporal matching of flight paths
The location of occurrences compared to the great circle flight path between the departure and arrival airport for Angel Flight records was evaluated. These were considered for occurrences within 50 NM of the flight path and up to 1 day between the recorded occurrence time and Angel Flight record. A significant benefit of this approach was where the specific departure and arrival airports were not known for the ATSB occurrence and where the occurrence was not recorded relative to the departure or arrival airport. One hundred and fifty-five records were identified in addition to Angel Flight records identified using the aforementioned techniques.
A total of 271 distinct Angel Flight records were matched with 233 reported occurrences using the techniques described above. Included in these occurrences were probable passenger carrying flights and re-positioning flights. Each Angel Flight record combined with occurrence records were ranked where more than one match was found. A probable match weighting was assigned to each match based on the reported proximity of the occurrence to the flights, time between the reported occurrence and the nominated flight time in the Angel Flight dataset, and location name matches. These weighting techniques were also used to exclude records where a match could not be identified.
This was calculated according to the following priorities:
Matched flight pairs – these were prioritised because the flight legs matched exactly with those recorded in the ATSB occurrence.
Records identified using flight path proximity were calculated next by multiplying ratios of distance and time together. A higher (more favourable) weighting was assigned to records that were nearest the reported time and distance.
The small number of location name matched-records were weighted by time.
All paired Angel Flight records and ATSB occurrences were manually verified using the calculated metrics to assist in the assessment. This also allowed a review of a reasonable expected time difference between the reported Angel Flight departure times and the time of the safety occurrence, given the distance from the departure. Occurrence times preceding the Angel Flight time were noted as likely to be the flight prior if a positive match could not be established for the aerodromes of arrival and/or departure. In other cases, the destination airport for Angel Flight was recorded as the origin for the ATSB occurrence at some time after the Angel Flight time. These were recorded as the flight after the Angel Flight. Both flights prior and following Angel flights were excluded from the primary analysis, but have been documented in the following appendices for reference.
Further use of Angel Flight records in analyses
Flight records used as normalisers
All flights not specifically labelled by Angel Flight as ‘regular passenger transport (RPT)’ were used as the primary normaliser for Angel Flight safety occurrences. This ensured the largest, and most conservative result with respect to occurrences and accidents per 10,000 flights analyses. A total of 13,389 flight records were identified as privately conducted flights on behalf of Angel flight between 2008 and 2017. One record was excluded as the label ‘NonPaxFlight’ was recorded in the Registration field.
Flight records used in RPT analysis
All non-standard aircraft registrations with the exception of flights labelled as ‘RPT’ were excluded from the analysis of private compared to RPT flight utilisation. A total of 20,025 records were used in this case, with 3,669 recorded as RPT, and 16,356 as private. 85 flight records were excluded from private operations. This was performed to provide a conservative count of private flights, and did not have any significant effect on results.
Number of flights as primary normaliser
Although the number of flights and flight hours are both commonly used as normalisers in aviation safety analysis, each provide different benefits. The total number of flights in each category were selected as the primary normaliser in this case for the following reasons:
To provide an indication of the likelihood that an Angel Flight community service flight is involved in a safety occurrence. In other words the likelihood of a passenger being exposed to a reduced level of safety during a flight.
To help identify systemic factors related to the conduct of Angel Flight community service flights.
Flight hours were considered by the ATSB as a normaliser, however were assessed as more limited in answering the safety objectives of the analysis, in particular where the duration of a flight may be a factor in a safety occurrence. Additionally, the number of flights for passenger carrying Angel Flights was known providing more confidence in the calculated rate compared to the number of flight hours, which required estimation. However, for reference, a comparison of the overall occurrence and accident rates is presented in Table B1 of Appendix B – Additional data.
Normalising by the number of flights around towered airports was also considered by the ATSB for analysis. This was not considered appropriate for the holistic, non-attribution based focus of the analysis. While this may provide an indication of the likelihood of pilot versus air traffic control errors around these airports, a comparison would not be possible between occurrences away from these locations. Furthermore, the primary objective of identification of relatively more likely occurrences relating to airspace related occurrences may be mis-represented in comparison to other private operations. Put in another way, even if Angel Flight airspace occurrences are elevated because they fly into these locations relatively more often, this represents an elevated safety risk, explained in part by them flying into these locations.
Estimation of Private, Business and Charter landings: 2008 to 2013
As of 2014, BITRE collected landing data in each operation category for each registration. Prior to this, the number of flights in charter, private and business operations required estimation due to landings data being collected by BITRE in aggregate form for each aircraft registration. Landing data (for example, number of flights conducted) for 2008 to 2013 was required due to the number of flights being known and flight hours being unknown for flights conducted on behalf of Angel Flight. The following process described how this was estimated using the known number of flight hours for private, business and charter operations and the ratio of these flight hours to total landings for each operation where there was a high proportion of a single operation category.
The objective was to approximate the typical flight length in each operation category, with the aim being to determine the number of landings given the number of hours flown in each operation category. This model was applied to each aircraft record individually based on ratios generated from the entire set of data given the breakdown of hours for each operation type. This model has three main assumptions based on a fixed proportion of operation category hours to landings.
The subscripts below denoted as x, y and z represent different operation types such as private, business and charter. For example, Hoursx denotes hours for operation type x.
Assumption 1: Within each operation category, there is the same ratio of hours to departures within the category which remains constant over all aircraft. That is,
Since individual hours are known for each operation type, and the constant can be derived for each from the sole operation types for some aircraft, the approximate departures can be derived for each operation type. The fixed ratio of departures to hours is defined as the average from those aircraft where the hours flown belong to one operation type.
Assumption 2: All aircraft conducting a particular operation, conduct similar length flights to those only conducting that operation. For example, those aircraft only conducting charter flights would have a similar flight length to those conducting charter flights 10% of the time.
Thus, the total departures for operation types x, y and z could be represented as:
Due to uncertainty and inherent variability in aircraft flying hours, and the likelihood that aircraft flying hours will change over time and for different aircraft operators, this model will have a high level of uncertainty.
Assumption 3: These flights follow the same model derived, and therefore the same proportion will apply to the original departures as per the ratio of the derived departures within each operation type.
The final calculation against each individual aircraft registration means that the total of the estimated departures always equals the total actual departures. To account for large differences between airframes, four groups were created and calculated separately for the combinations of fixed and rotary wing aircraft, and single and multiple engines, and were derived from aircraft that solely performed each operation type. For example, the landings per hour rate for fixed wing single engine private operations was derived from aircraft only used for private operations.
Note that Angel Flight landings were subtracted from the estimated total of private flights for analysis purposes, accounting for Angel Flight community service flights being a sub-set of private operations.
Estimation of city flight pairs
An analysis was conducted comparing known regular public transport (RPT) flight routes to privately conducted Angel Flight routes to provide a general indication of RPT as an alternative. To achieve this, the flight sector pairs of sponsored Angel Flight RPT flights were compared to the sectors of privately conducted Angel Flights.
Due to some private and RPT flights using different airports in similar regions, it was desired to identify regions rather than the specific airports. This is because it is expected that it may be practical to travel to and from different airports in the same region. To account for this, airports within 50 kilometres of the published Angel Flight departure and arrival airport were considered as viable options. This is illustrated in Figure A1.
Figure A1: Diagram of the region identification for determining availability of RPT options
A list of flight routes using direct RPT flights was developed based on records of RPT flights used by Angel Flight. Each privately operated community service flight was classified into the following categories: no RPT option used, exact RPT match or RPT within 50 kilometres. A limitation of this approach is that the availability of RPT flights has not been quantified for the day of travel – and as such, there may not have been availability (or indeed the conduct of an RPT flight) on that day. In contrast, it is possible that RPT flights may have available for use in some regions, however, have not been previously utilised. Due to this analysis relying on RPT routes historically used by Angel Flight, sectors never used by Angel Flight are not identified using this approach. As such, it should be noted that the purpose of this analysis is to provide a generalised indication of an RPT alternative being available where it is confirmed that these services have been historically utilised by Angel Flight Australia.
Estimation of repositioning flight totals
A supplementary analysis was conducted to evaluate safety occurrences on repositioning flights – that is, those flights occurring prior to and following privately conducted passenger carrying flights on behalf of Angel Flight Australia, for the purposes of flying from the pilot’s location to the passenger meeting point, and return. This occurrence data required normalisation to compare and combine this with other analyses. As the number of these repositioning flights was unknown, they required estimation based on the passenger carrying flight information provided by Angel Flight Australia.
Analysis of the passenger carrying flights revealed cases where passenger carrying flights using the same aircraft would be conducted in consecutive segments within a relatively short period of time. This was assumed to be cases where Angel Flight passengers were transported to medical aid, followed by the medical appointment and transport back to their homes. For example, a flight from Port Lincoln to Adelaide, SA would be conducted followed 5 and a half hours later by a return flight from Adelaide to Port Lincoln. In these cases, it was considered probable that repositioning flights were not required in between these passenger carrying legs when the same aircraft was being used.
Passenger carrying flights with the same aircraft registration and matching arrival / departure location were grouped when the recorded departure times were within 24 hours. The total number of groups were calculated and used as the estimated figure for the number of repositioning flights, as illustrated by Figure A2. This shows two hypothetical groups of Angel Flights covering a scenario where a pilot and their aircraft conduct a single Angel Flight leg requiring a flight from a home base to the passengers’ location, the repositioning flight prior, followed by the passenger carrying leg from A to B, and a possible return home to C, if B is not the home-base location. The second scenario in Figure A2 covers the potential where a prior repositioning leg is flown to location A to collect Angel Flight passengers to location B. Followed by a break, and then a return flight from B to A. In this case, the pilot may not need to return home between flights. Consequently, there would be only two repositioning flights, rather than four.
Figure A2: Estimation of repositioning flight legs using known passenger carrying flights
The estimations performed are expected to have two main conflicting limitations. It may be possible that pilots would return or fly to another location between legs, however, noting that although a maximum of 24 hours was used, the median time taken between flights was 5 hours and a half hours from the first departure time – this is expected to be around the time taken for a medical appointment, including return ground transport to the medical centre from the airport. Furthermore, the home base for the pilot may actually be located at one of the locations. For example, there may be pilots based at a metropolitan airport used for the passenger ground transport to the medical centre. This would mean only one repositioning flight per leg, rather than two. As such, these factors are expected to provide some balance, however, the precise breakdown is not known.
The analysis conducted revealed 1,246 consecutive flight pairs, and 38 flight triplets. Summation of the groups with single legs revealed a total of 12,068 groups. Therefore, 12,068 flights were attributed to both the prior repositioning and post repositioning flights, a total of 24,136 flights.
Occurrence data set comparisons
The entire sets of both Angel Flight and other private safety occurrences were used for the analysis. Comparisons between subsets of the same category were conducted between Angel Flight organised flights and other private operations, normalised by the respective number of flights in each group. For example, a comparison of the total number of flight preparation and navigation occurrences or fatal accidents. All remaining private occurrences excluding those associated with Angel Flight operations were used as the main comparison group to allow focus on the safety outcomes, rather than attribution to specific parties. For example, safety occurrences related to runway events are identified in the study as being disproportionately higher per flight for Angel Flight organised flight compared to the private average, revealing that this is an area of safety concern for Angel Flight. Although the explanation of why this is the case is likely to be due to a combination of factors, such as exposure to the particular airports that Angel Flight pilots are flying to or other operational factors, the likelihood of this safety occurrence happening is of primary concern.
The reasons why specific safety indicators were elevated for Angel Flight were outside the scope of the investigation. This was because the safety baseline for Angel Flight community service flights was unknown, and the ATSB’s primary concern being the identification of the most prevalent areas of safety concern, regardless of attribution. The rational of the ATSB’s safety focus is discussed in depth in ATSB report AR-2007-053.[48] However, the areas of safety concern identified in this analysis are encouraged to be used as drivers for further analysis. In these cases, each safety indicator could be evaluated against various confounding factors which may include normalising by the number of flights into specific airports, or case-control type studies to isolate and control for known factors. However, it is important to note that controlling for these factors in the first case was expected to bias the data and may have prevented these safety risks from being identified.
Quantification of uncertainty and probability based assessments
The calculated average rate of safety occurrences per flight allows the quantitative comparison of the likelihood of a safety occurrence between different operational groups, revealing elevated safety risks in one operational group compared to another, and the overall probability of a safety occurrence per flight within a group. To assess the likelihood that observed differences in the rate of occurrences per flight were unlikely to occur through random chance, statistical analyses were performed. All statistical assessments were performed in the R programming language[49] using base level functions unless specified. The main objectives were to indicate the probability, or chances of different types of safety occurrences being more likely during flights conducted for Angel Flight Australia compared to flights in other operational groups, and to quantify the uncertainty in the difference between occurrence rates.
The main statistical test used assesses the probability that Angel Flight occurrences are more prevalent per flight compared to other private operations and other operations in various categories. Additionally, the assessment uses credible intervals of the difference in proportions to show the possible magnitude of these differences.
Thresholds used for statistical assessment
Using the same rationale as the ATSB’s approach to the identification of potential safety issues, statistical thresholds in this report use burdens of proof in line with ATSB’s safety focussed approach to identify potential safety issues. This is to allow problems to be solved, thereby assisting in improving safety and the prevention of further loss of life. As such, the statistical assessments described below were conducted using the thresholds of greater than 67%, and greater than 95%. In the same way as for the evaluation of a single occurrence, it is expected that the mid-range standard of 67% used in this analysis will produce a reasonable, useful and appropriately qualified picture of the nature of Angel Flight safety occurrences (AR-2007-053 section 6.3)48. Note also that this threshold is the same as applied in most civil court proceedings in Australia. Descriptions to a 95% probability or credible interval were included to provide reference to traditional statistical analyses.
The ATSB uses IPCC definitions to communicate uncertainty regarding technical information, as noted in section 2.6.3 of ATSB report AR-2007-05348. In the case of this quantitative data analysis, probability and credible intervals are described against these specific thresholds. These are presented as where the data probably lies, within a 67% probability, and also where it is highly likely that the rate difference lies, to a 95% probability. It should also be noted that these statistical tests are not used in isolation, and in many cases, the results meet traditional ‘significance’ levels.
Calculation of probability
All assessments of safety occurrences were conducted using the Bayesian model for a Binomial proportion to calculate the probability of the relevant Angel Flight occurrence category being greater than private or other operations. The Binomial model was assumed to represent the probability of an occurrence, given the number of flights in each group.
The test was performed using Monte-Carlo methods, randomly sampling and comparing binomial distributions representing the rate of occurrences for private or other operations rate with the binomial distribution from the relevant Angel Flight operation category. One-million paired samples were taken from each of the two distributions and assessed. If the sample from the Angel Flight binomial distribution x-axis value had a lower proportion (representing the rate), a 0 was recorded against the paired sample, and if higher, a 1 was recorded. The probability was calculated by taking the proportion of values recorded as one from the one-million paired samples. This is equivalent to summing the right side of the distribution greater than 0 generated by calculating the difference between the binomial distributions for Angel Flight and comparison operation. This represents a right-tailed statistical assessment alternate hypothesis Angel Flight greater than comparison operation.
Throughout this report the rate of all safety occurrences was derived from the probability of an occurrence (per flight) using prior beta distribution with the Haldane prior. The Haldane prior beta (0,0) is the most appropriate prior for minimising the influence of prior data on the posterior distribution for a beta binomial model.[50] Probability is presented as a calculated ‘point value’, indicating the overall confidence that Angel Flight operations were greater or smaller in the tested category. A value of 50% indicates confidence that it is about as likely as not that Angel Flight had a higher likelihood of this occurrence group per flight compared to the comparison group.
Calculation of uncertainty between rates – credible intervals
The magnitude of the difference in occurrence rates per 10,000 flights between Angel Flight and other operations is presented in terms of credible intervals (CIs). These are calculated from the difference in binomial proportions, from the upper and lower bounds of the Highest Density Interval of the binomial proportions from each operational group. These were calculated using Markov Chain Monte Carlo (MCMC) within R.[51] The Highest Density Interval (HDI) is the shortest interval which a specified proportion of the data is contained. Alternatively, it can be defined as the interval in which there is a specified probability that the mode of the data resides.
The thresholds used for credible intervals were 67% and 95%, as described in Thresholds used for statistical assessment. As the distribution being assessed is the difference between Angel Flight and a comparison operational group, if the lower bound of the 95% credible interval is above 0, this indicates where a traditional two-tailed statistical test would be labelled as ‘significant’. The 67% CI indicates the range where the rate difference between the Angel Flight and comparison operation probably lies. However, it should be noted that as this is a safety focussed analysis, the calculation of probability is a right-tailed assessment driven by the primary hypothesis of the likelihood of Angel Flight having more safety occurrences per flight compared to other operations.
Appendix B – Additional data
Occurrences and injuries across operations
Table B1 outlines the occurrences and accidents by operation over the ten-year period from 2008 to 2017. The calculated rate of total occurrences, accidents and fatal accidents is also shown per 10,000 flights and per 10,000 flight hours. The number of flights and flight hours used to calculate the rates required estimation in some operational categories. These processes are documented in Appendix A – Data analysis methods, and are annotated against relevant figures in Table B1. Safety occurrences for both passenger carrying and non-passenger carrying repositioning Angel Flights are also included in the table below.
Table B1: Occurrences, accidents and injuries by operation, 2008 to 2017
Table B2 shows results of statistical analyses using the approach documented in Appendix A – Data analysis methods: Quantification of uncertainty and probability based assessments. Comparisons between private flights on behalf of Angel Flight Australia compared to all other private operations are shown. The data in the table is grouped by the occurrence categories where statistical analysis was performed for all occurrences, accidents and fatal accidents.
Statistical tests were performed for the number of safety occurrences for all three types of Angel Flight legs, including aggregated totals. However, due to no accidents being identified in non-passenger carrying repositioning flights, only the passenger carrying and combined Angel Flight rate was calculated based on the aggregate of all calculated passenger carrying and repositioning Angel Flights.
The first six columns of data show the number of occurrences, number of flights and rate of occurrences per 10,000 flights in pairs for Angel Flight (labelled AF), and other private (labelled PV) operations in each group. Data for each specific Angel Flight operation is shown in the column Angel Flight Operation Category as follows:
Pax Angel Flight – Passenger carrying private flights on behalf of Angel Flight
Prior AF Non-Pax – Non passenger carrying repositioning flights prior to passenger carrying Angel Flights
Post AF Non Pax – Non passenger carrying repositioning flights following passenger carrying Angel Flights
All Non Pax AF – All non passenger carrying repositioning flights prior to and following passenger carrying Angel Flights
AF Combined – All non passenger carrying repositioning flights prior to and following passenger carrying Angel Flights, and passenger carrying Angel Flights
The columns labelled ‘Probable rate differences: Angel Flight – Other private’ toward the right side of Table B2 show results from the calculation of difference in binomial proportions between the labelled Angel Flight Operational category and other private operations, as described further in Appendix A – Data analysis methods: Quantification of uncertainty and probability based assessments. The data in columns 67% CI and 95% CI show the credible intervals calculated from the difference in the binomial proportions of Angel Flight compared to other private operations. This indicates the expected difference in the rate of Angel Flight occurrences compared to private occurrences per 10,000 flights providing an indication of where the rate difference probably (67%) lies, and where it is very likely (95%) to lie.
For example, from the first row of data, there are probably (67%) between 22.4 and 32.3 more safety occurrences per 10,000 flights for passenger carrying Angel Flights compared to other private operations.
The column ‘Probability (Angel Flight > Other Private)’ shows the calculated binomial probability that Angel Flight has more occurrences per flight compared to other private operations. These calculations are also discussed further in Appendix A – Data analysis methods: Quantification of uncertainty and probability based assessments. The probability presented represents the statistical expected likelihood Angel Flight occurrences per flight were greater than other private operations in each occurrence grouping.
For example, from the first row of data, a probability greater than 99.9% was calculated that safety occurrences were more common per flight for passenger carrying Angel Flight operations combined compared to other private operations. This statistical calculation accounted for the number of flights (13,389 for private passenger carrying flights conducted on behalf of Angel Flight, and approximately 3.5 million flights for private operations) to provide confidence, maximising the use of the data available.
Table B2 shows that the rate of total occurrences per 10,000 flights is almost certainly (>99%) higher for all Angel Flight operation categories compared to other private operations. It is highly likely that there are between 18.1 and 38.0 more safety occurrences per 10,000 flights for passenger carrying Angel Flights compared to the average of other private flights. This was a much larger difference compared to both prior and post non-passenger carrying Angel Flight operations. The combination of all non-passenger carrying Angel Flights were expected to have 3.7 to 13.6 more occurrences per 10,000 flights compared to other private flights.
The passenger carrying Angel Flight accident rate was probably higher (P=84.9%) compared to other private operations. When combining this with the estimated number of non-passenger carrying repositioning flights, it is unlikely (P=17.8%) that the accident rate was higher. In contrast, the fatal accident rate was calculated to be probably higher (P=82.0%) for Angel Flight operations when taking into account non passenger carrying repositioning flights, and very likely (P=96.8%) when considering passenger carrying flights alone. It is highly likely that the Angel Flight passenger carrying fatal accident rate ranges from -0.2 fewer to 3.4 more fatal accidents per 10,000 flights compared to other private operations.
Table B2: Comparison of Angel Flight occurrences with private operations flights prior to and following passenger carrying Angel Flights, 2008 to 2017
Angel Flight occurrence type analysis results
The following data displays the analysis results of the types of reportable safety occurrences (occurrence types) during flights conducted on behalf of Angel Flight in comparison to other private operations. A full list of occurrence types, along with their definitions, is available on the ATSB website Terminology page associated with the national aviation occurrence database.
Figure B1 displays the relative number of occurrences involving passenger carrying flights conducted on behalf of Angel Flight in five main categories, as shown in the inner ring. Secondary groupings shown in the outer ring of Figure B1 further refine the classification of these occurrences. It is common to have multiple occurrence types reported for each occurrence, therefore, these occurrences should not be aggregated by each sub-category. However, the total number of occurrences in each grouping are displayed in the left side column of tables B3 through to B7 below, with the grand-total occurrences in each table displayed in the title of each.
Relative proportions of occurrence groups in Angel Flight and other private operations (Figures B3 – B6)
Figures B3 – B6 show the proportion of occurrence types against the total occurrences in each operational category (as displayed in the legend). These figures are indicated as a pictorial illustration to complement the percentage difference column (labelled “PD”) in Tables B3 – B7 below, being the calculated difference of the percentages in each category.
This provides an indication of the relative prevalence of an occurrence group compared to all other safety occurrences between passenger carrying and non-passenger carrying Angel Flight operations, and other private operations. Numbers above each column show the total number of safety occurrences in each occurrence group. As for Figure B1, these occurrence groups should not be aggregated due to the possibility of multiple occurrence grouping per safety occurrence, however, the overall total presented in the legend can be used for this purpose. Note that the occurrence categories presented align with the outer ring in Figure B1, and in Tables B3 – B7 on the left side “Minor occurrence grouping” column.
For example, the total of five flight preparation and navigation forms about 10.6% (5/47) of all passenger carrying Angel Flight operations, compared to 4.2% (106/2530) of other private operations, equating to a percentage difference of 6.5% (rounded) as shown in Table B3. Note that non-passenger carrying flights are separated from passenger carrying Angel Flights in Figures B3 – B6 to compare and contrast these to each other and other private operations in each occurrence grouping. In contrast, Tables B3 – B7 present passenger carrying and the combined (passenger and non-passenger carrying total) for the statistical analysis due to the analysis focus on passenger carrying flights, and to reduce uncertainty in results.
Results of statistical analysis between Angel Flight and other private operations ordered by largest differences (Tables B3 to B7)
The five tables below B3 through to B7 display similar information to Figure B1, and compare the types of occurrences involving flights conducted on behalf of Angel Flight to all other private operations. Each table contains aggregates for each of the five major occurrence types, as shown in the inner circle of Figure B1. The left side of each table shows groupings of similar types of occurrences, as shown in Figure 10, the outer circle of Figure B1, and the horizontal axis categories of Figures B3-B6. This contains the number of occurrences (in brackets under the name), the rate of occurrences per 10,000 flights and two statistical measures – the beta-binomial probability, and the percentage difference between Angel Flight and other private operations. The occurrence groupings are ordered by the largest statistical differences where Angel Flight had more occurrences per flight compared to private operations.
Figure B2: Extract from Table B3 – Flight preparation and navigation safety occurrences
The following abbreviations are used in the column headings of Tables B3 – B7:
AF PC: Private passenger carrying flights on behalf of Angel Flight
AF PR: Repositioning flights prior to passenger carrying flights on behalf of Angel Flight
AF PO: Repositioning flights following passenger carrying flights on behalf of Angel Flight
All AF: All Angel Flight combined
PV: Other private flights
67%CI / 95%CI: Credible intervals – Probable range (67%) and Highly likely range (95%)
AF – PV: Angel Flight (Generalised) minus other Private
P AF > PV: Probability Angel Flight (Generalised) greater than other private
PD: Percentage difference between Angel Flight categories and other private operations.
The following describes the data under each column in Tables B3 – B7. To aid use of these tables, a sample interpretation using the known fatal accident pre-cursor flight preparation and navigation is also presented below. Reference data for the sample is contained in Figure B2.
Minor Occurrence Grouping: Description of the occurrence grouping containing similar occurrences. This shows the name of the occurrence grouping, for example “Flight preparation / navigation”, and shows the total number of occurrence in this group for each operational category, in this case, 5 passenger carrying, 1 prior and 2 post repositioning Angel Flights had flight preparation or navigational issues compared to 106 private flights.
AF PC (All AF): The five columns labelled AF PC (All AF) indicate where results of two parallel analyses are presented for Angel Flight occurrences; the primary passenger carrying analysis, labelled AF PC, and the combined analysis for all privately operated passenger and non-passenger carrying flights conducted on behalf of Angel Flight, presented in brackets.
Occurrences per 10,000 flights: The rate of nominated occurrences per 10,000 flights for Angel Flight, labelled AF PC (All AF), and all other private operations, labelled PV. In the example above: 3.7 (2.1), indicates the Angel Flight passenger carrying rate of 3.7 flight preparation or navigation safety occurrences per 10,000 flights, with a combined rate of 2.1 safety occurrences per 10,000 flights. For comparison, the private rate in this example is 0.3.
67%CI / 95%CI: The data in columns 67% CI and 95% CI show the credible intervals calculated from the difference in the binomial proportions of Angel Flight compared to other private operations. Further explanation of these can be found in the descriptions for Table B2, and Appendix A – Data analysis methods: Quantification of uncertainty and probability based assessments.
P AF > PV: Shows the calculated binomial probability that Angel Flight has relatively more occurrences per flight compared to other private operations. These calculations are discussed further in Appendix A – Data analysis methods: Quantification of uncertainty and probability based assessments, with other discussions explained for Table B2. In the example, a probability greater than 99.9% was calculated that flight preparation and navigation was more common per flight for both passenger carrying and all Angel Flight operations combined compared to other private operations.
Conversely, note also that a result of 37.2%, as shown in table B5 for occurrences relating to powerplant and propulsion, indicates a 62.8% chance that other private operations were greater. Records marked as N/A indicate where there were no Angel Flight occurrences identified producing an invalid statistical result with the techniques used. Statistical parameters used are discussed in Appendix A – Data analysis methods.
PD: Percentage differences shown indicate differences in each occurrence category between Angel Flight and other private operations against the total occurrences in each type of operation. This is calculated by subtracting the percentage of each operation in Angel Flight from Private operations percentage. It is also useful to provide an indication of the relative frequency of these occurrences where no Angel Flight occurrences were identified in a category (and no statistical result exists). For example, there were no reported fuel related occurrences for passenger carrying flights conducted on behalf of Angel Flight and this was 4.7% lower than fuel related occurrences in other private operations.
It is important to note that all percentages were calculated from the total of all occurrences in each operational group, for example, 47 occurrences from passenger carrying Angel Flights and 2,530 other private operations safety occurrences, shown in Table B1.
Further description for this calculation using the example of flight preparation and navigation can be found in the description for Figures B3-B6, where this is shown pictorially.
Occurrence types: Occurrence types shown on the right side of tables B3 to B7 display more specific information relating to the occurrence grouping. These are ordered by types of occurrence with the largest number of Angel Flight occurrences. This is shown for all four operational categories. For example, Flight preparation or navigation – VFR into IMC was recorded in three passenger carrying Angel Flights, 36 cases for private flights with no cases being recorded in either operational categories of non-passenger carrying Angel Flights.
Sample interpretation of data analysis – flight preparation and navigation
Tables B3-B7 are intended to be used as a tool to identify occurrence groups that are most different between the two types of operations, to drive safety actions in areas most likely to reduce the increased rate of occurrences for during flights conducted on behalf of Angel Flight. The following paragraph provides a brief interpretation of a comparison between Angel Flight and other private operations using the tabled data for the flight preparation and navigation occurrence grouping using the specific figures published. This rationale could be applied across all other occurrence groupings.
For both passenger carrying and the combination of all Angel Flight operations, there was a very high probability (more than 999 in 1,000 chance) that flight preparation and navigation occurrences were more likely to occur in comparison to other private operations. For every 10,000 flights conducted in each operational category, is very likely (95%CI) there would be at least 0.6 more flight preparation and navigation occurrences during passenger carrying Angel Flights compared to other private operations, probably (67%CI) ranging between 1.4 and 4.4. As the lower bound of the 95%CI is above zero, this also indicates statistical significance in this case.
Figure B3: Operational related safety occurrence groups by total proportion of operation category, 2008 to 2017
Table B3: Operational Angel Flight (Passenger carrying and combined) occurrences ordered by largest statistical differences to other private operations, 2008 to 2017 (Total occurrences: AF PC: Σ25, AF PR Σ7, AF PO: Σ13, PV Σ1,344)
Occurrence grouping
Occurrence types
Occurrences per 10,000 flights
95% CI AF - PV
67% CI AF - PV
P AF > PV
PD
Occurrences
Minor occurrence grouping
AF PC (All AF)
PV
AF PC (All AF)
AF PC (All AF)
AF PC (All AF)
AF PC (All AF)
Occurrence Type
AF PC
AF PR
AF PO
PV
Runway events AF PC: 14 AF PR: 7 AF PO: 9 PV: 277
10.5 (8.0)
0.8
4.5 to 15.3 (4.5 to 10.1)
6.5 to 11.8 (5.6 to 8.4)
>99.9% (>99.9%)
18.8% (24.3%)
Runway Incursion
11
5
8
72
Depart / App / Land Wrong Runway
3
2
1
20
Runway Excursion
1
0
0
182
Runway undershoot
0
0
0
6
Other
0
0
0
4
Communications AF PC: 6 AF PR: 2 AF PO: 1 PV: 140
4.5 (2.4)
0.4
0.9 to 7.7 (0.6 to 3.6)
1.9 to 5.2 (1.1 to 2.6)
>99.9% (>99.9%)
7.2% (5.1%)
Air-ground-air
6
2
1
128
Other
0
0
0
8
Transponder related
0
0
0
4
Flight preparation / Navigation AF PC: 5 AF PR: 1 AF PO: 2 PV: 106
3.7 (2.1)
0.3
0.6 to 6.7 (0.5 to 3.3)
1.4 to 4.4 (1.0 to 2.4)
>99.9% (>99.9%)
6.5% (5.2%)
VFR into IMC
3
0
0
36
Flight below minimum altitude
1
1
0
18
Lost / unsure of position
1
0
2
17
Other
0
1
1
13
Unsecured door / panel
0
0
1
11
Aircraft preparation
0
0
0
28
Miscellaneous AF PC: 2 AF PR: 0 AF PO: 0 PV: 42
1.5 (0.5)
0.1
-0.1 to 3.5 (-0.1 to 1.2)
0.1 to 1.7 (0.0 to 0.5)
98.8% (92.4%)
2.6% (0.7%)
Other
2
0
0
15
Security related
0
0
0
1
Unauthorised low flying
0
0
0
4
Warning Devices
0
0
0
22
Aircraft control AF PC: 3 AF PR: 0 AF PO: 0 PV: 365
2.2 (0.8)
1.0
-0.8 to 3.8 (-1.0 to 0.7)
-0.4 to 1.8 (-0.8 to 0.0)
83.6% (25.7%)
-8.1% (-10.9%)
Loss of control
3
0
0
143
Other
0
0
0
21
Stall warnings
0
0
0
1
Unstable approach
0
0
0
3
Wheels up landing
0
0
0
62
Airframe overspeed
0
0
0
1
Control issues
0
0
0
32
Hard landing
0
0
0
99
Incorrect configuration
0
0
0
17
In-flight break-up
0
0
0
4
Fumes, Smoke, Fire AF PC: 1 AF PR: 0 AF PO: 0 PV: 75
0.7 (0.3)
0.2
-0.3 to 2.0 (-0.3 to 0.6)
-0.2 to 0.6 (-0.2 to 0.1)
75.3% (45.2%)
-0.8% (-1.8%)
Fumes
1
0
0
22
Smoke
1
0
0
43
Fire
0
0
0
22
Terrain Collisions AF PC: 3 AF PR: 0 AF PO: 0 PV: 499
2.2 (0.8)
1.4
-1.2 to 3.4 (-1.3 to 0.3)
-0.7 to 1.4 (-1.2 to -0.4)
70.5% (10.3%)
-13.3% (-16.2%)
Collision with terrain
3
0
0
319
Ground strike
1
0
0
149
Wirestrike
0
0
0
30
Controlled flight into terrain
0
0
0
11
Ground operations AF PC: 1 AF PR: 0 AF PO: 0 PV: 147
0.7 (0.3)
0.4
-0.5 to 1.8 (-0.5 to 0.4)
-0.4 to 0.4 (-0.4 to -0.1)
57.3% (21%)
-3.7% (-4.6%)
Collision on ground
1
0
0
100
Foreign object damage / debris
0
0
0
13
Ground handling
0
0
0
2
Ground prox
0
0
0
1
Injury
0
0
0
2
Jet blast / Prop / Rotor wash
0
0
0
2
Other
0
0
0
7
Taxiing collision / Near collision
0
0
0
64
Ground proximity alerts / warnings AF PC: 0 AF PR: 0 AF PO: 0 PV: 1
0.0 (0.0)
0.0
0.0 to 0.0 (0.0 to 0.0)
0.0 to 0.0 (0.0 to 0.0)
N/A (N/A)
0.0% (0.0%)
Ground proximity alerts / warnings
0
0
0
1
Regulations and SOPs AF PC: 0 AF PR: 0 AF PO: 0 PV: 2
0.0 (0.0)
0.0
0.0 to 0.0 (0.0 to 0.0)
0.0 to 0.0 (0.0 to 0.0)
N/A (N/A)
-0.1% (-0.1%)
Other
0
0
0
1
Standard Operating Procedures
0
0
0
1
Aircraft loading AF PC: 0 AF PR: 0 AF PO: 0 PV: 4
0.0 (0.0)
0.0
0.0 to 0.0 (0.0 to 0.0)
0.0 to 0.0 (0.0 to 0.0)
N/A (N/A)
-0.2% (-0.2%)
Dangerous goods
0
0
0
1
Loading related
0
0
0
3
Significant event AF PC: 0 AF PR: 0 AF PO: 0 PV: 14
0.0 (0.0)
0.0
-0.1 to 0.0 (-0.1 to 0.0)
0.0 to 0.0 (0.0 to 0.0)
N/A (N/A)
-0.6% (-0.6%)
Other
0
0
0
14
Crew and cabin safety AF PC: 0 AF PR: 0 AF PO: 0 PV: 19
0.0 (0.0)
0.1
-0.1 to 0.0 (-0.1 to 0.0)
-0.1 to 0.0 (-0.1 to 0.0)
N/A (N/A)
-0.8% (-0.8%)
Depressurisation
0
0
0
5
Flight crew incapacitation
0
0
0
12
Unrestrained occupants / objects
0
0
0
2
Warning device AF PC: 0 AF PR: 0 AF PO: 0 PV: 27
0.0 (0.0)
0.1
-0.1 to 0.0 (-0.1 to 0.0)
-0.1 to -0.1 (-0.1 to -0.1)
N/A (N/A)
-1.1% (-1.1%)
Landing gear unsafe indication
0
0
0
27
Fuel related AF PC: 0 AF PR: 0 AF PO: 2 PV: 120
0.0 (0.5)
0.3
-0.4 to -0.3 (-0.3 to 0.9)
-0.4 to -0.3 (-0.3 to 0.3)
N/A (63.6%)
-4.7% (-2.4%)
Contamination
0
0
0
16
Exhaustion
0
0
0
12
Leaking or venting
0
0
0
14
Low fuel
0
0
0
6
Other
0
0
1
4
Starvation
0
0
1
70
Figure B4: Airspace related safety occurrence groups by total proportion of operation category, 2008 to 2017
Table B4: Airspace related Angel Flight (Passenger carrying and combined) occurrences ordered by largest statistical differences to other private operations, 2008 to 2017 (Total occurrences: AF PC: Σ20, AF PR Σ9, AF PO: Σ8, PV Σ369)
Occurrence grouping
Occurrence types
Occurrences per 10,000 flights
95% CI AF - PV
67% CI AF - PV
P AF > PV
PD
Occurrences
Minor occurrence grouping
AF PC (All AF)
PV
AF PC (All AF)
AF PC (All AF)
AF PC (All AF)
AF PC (All AF)
Occurrence Type
AF PC
AF PR
AF PO
PV
Operational Non-compliance AF PC: 14 AF PR: 4 AF PO: 4 PV: 78
10.5 (5.9)
0.2
5.1 to 15.8 (3.3 to 8.1)
7.1 to 12.4 (4.3 to 6.7)
>99.9% (>99.9%)
26.7% (22.8%)
Operational Non-compliance
14
4
4
78
Verbal instruction
9
3
3
22
Published information
3
0
0
13
ANSP Operational error AF PC: 3 AF PR: 0 AF PO: 0 PV: 15
2.2 (0.8)
0.0
0.2 to 4.7 (0.0 to 1.7)
0.6 to 2.8 (0.2 to 1.0)
>99.9% (>99.9%)
5.8% (2.9%)
Information / procedural error
3
0
0
14
Failure to pass traffic
0
0
0
1
Aircraft separation AF PC: 7 AF PR: 5 AF PO: 5 PV: 284
5.2 (4.5)
0.8
1.0 to 8.4 (1.7 to 5.9)
2.1 to 5.8 (2.5 to 4.6)
>99.9% (>99.9%)
3.7% (8.8%)
Loss of separation
6
3
0
46
Issues
1
2
3
152
Airborne collision alert system warning
0
1
0
12
Collision
0
0
0
3
Loss of separation assurance
0
0
2
7
Near collision
0
0
0
74
Airspace infringement AF PC: 3 AF PR: 1 AF PO: 2 PV: 29
2.2 (1.6)
0.1
0.1 to 4.7 (0.4 to 2.8)
0.6 to 2.8 (0.7 to 1.9)
>99.9% (>99.9%)
5.2% (5.9%)
Airspace infringement
3
1
2
29
PRD
2
0
1
2
Controlled airspace
1
0
1
13
Encounter with RPA AF PC: 1 AF PR: 0 AF PO: 0 PV: 12
0.7 (0.3)
0.0
-0.1 to 2.2 (-0.1 to 0.8)
0.0 to 0.8 (0.0 to 0.3)
95.6% (88.1%)
1.7% (0.7%)
Near encounter with RPA
1
0
0
12
Breakdown of co-ordination AF PC: 0 AF PR: 0 AF PO: 1 PV: 1
0.0 (0.3)
0.0
0.0 to 0.0 (0.0 to 0.8)
0.0 to 0.0 (0.0 to 0.3)
N/A (99%)
0.0% (1.1%)
Breakdown of co-ordination
0
0
1
1
Other AF PC: 0 AF PR: 0 AF PO: 0 PV: 4
0.0 (0.0)
0.0
0.0 to 0.0 (0.0 to 0.0)
0.0 to 0.0 (0.0 to 0.0)
N/A (N/A)
-0.2% (-0.2%)
Other
0
0
0
4
Figure B5: Technical failure safety occurrence groups by total proportion of operation category, 2008 to 2017
Table B5: Technical failures related to Angel Flight (Passenger carrying and combined) occurrences ordered by largest statistical differences to other private operations, 2008 to 2017 (Total occurrences: AF PC: Σ13, AF PR Σ3, AF PO: Σ3, PV Σ1,139)
Occurrence grouping
Occurrence types
Occurrences per 10,000 flights
95% CI AF - PV
67% CI AF - PV
P AF > PV
PD
Occurrences
Minor occurrence grouping
AF PC (All AF)
PV
AF PC (All AF)
AF PC (All AF)
AF PC (All AF)
AF PC (All AF)
Occurrence Type
AF PC
AF PR
AF PO
PV
Airframe AF PC: 8 AF PR: 1 AF PO: 0 PV: 400
6.0 (2.4)
1.1
1.1 to 9.0 (-0.2 to 2.9)
2.4 to 6.3 (0.3 to 1.8)
>99.9% (96.9%)
1.2% (-5.2%)
Landing gear / Indication
6
1
0
320
Objects falling from aircraft
1
0
0
31
Other
1
0
0
7
Windows
1
0
0
13
Rotors / tail rotor
0
0
0
1
Control surface
0
0
0
2
Doors / Exits
0
0
0
20
Furnishings and fittings
0
0
0
3
Fuselage / Wings / Empennage
0
0
0
4
Landing gear
0
0
0
64
Systems AF PC: 3 AF PR: 2 AF PO: 0 PV: 291
2.2 (1.3)
0.8
-0.6 to 4.0 (-0.5 to 1.7)
-0.2 to 2.0 (-0.2 to 0.9)
90% (79.9%)
-5.1% (-5.6%)
Avionics / Flight Instruments
1
0
0
98
Electrical
1
2
0
90
Other
1
0
0
8
Fire protection
0
0
0
1
Flight controls
0
0
0
27
Flight instruments
0
0
0
3
Fuel
0
0
0
32
Hydraulic
0
0
0
16
Air / Pressurisation
0
0
0
13
Anti-ice protection
0
0
0
3
Avionics
0
0
0
17
Powerplant / propulsion AF PC: 2 AF PR: 0 AF PO: 3 PV: 509
1.5 (1.3)
1.4
-1.4 to 2.1 (-1.1 to 1.1)
-1.2 to 0.4 (-0.8 to 0.3)
42.5% (37.2%)
-15.9% (-14.2%)
Engine failure or malfunction
2
0
2
411
Partial power loss / rough running
1
0
1
120
Propellers / Rotor malfunction
0
0
0
17
Total power loss / engine failure
0
0
0
107
Transmission and gearboxes
0
0
0
9
Abnormal engine indications
0
0
1
74
Other
0
0
0
27
Figure B6: Environmental related safety occurrence groups by total proportion of operation category, 2008 to 2017
Table B6: Environment related Angel Flight (Passenger carrying and combined) occurrences ordered by largest statistical differences to other private operations, 2008 to 2017 (Total occurrences: AF PC: Σ5, AF PR Σ0, AF PO: Σ1, PV Σ296)
Occurrence grouping
Occurrence types
Occurrences per 10,000 flights
95% CI AF - PV
67% CI AF - PV
P AF > PV
PD
Occurrences
Minor occurrence grouping
AF PC (All AF)
PV
AF PC (All AF)
AF PC (All AF)
AF PC (All AF)
AF PC (All AF)
Occurrence Type
AF PC
AF PR
AF PO
PV
Weather AF PC: 2 AF PR: 0 AF PO: 0 PV: 83
1.5 (0.5)
0.2
-0.2 to 3.3 (-0.2 to 1.1)
0.0 to 1.6 (-0.2 to 0.4)
95.9% (77.8%)
1.0% (-0.9%)
Other
1
0
0
37
Unforecast weather
1
0
0
9
Windshear / microburst
0
0
0
7
Turbulence / Windshear / Microburst
0
0
0
19
Icing
0
0
0
7
Lightning strike
0
0
0
7
Interference with aircraft from ground AF PC: 1 AF PR: 0 AF PO: 0 PV: 12
0.7 (0.3)
0.0
-0.1 to 2.2 (-0.1 to 0.8)
0.0 to 0.8 (0.0 to 0.3)
95.6% (88.1%)
1.7% (0.7%)
Interference with aircraft from ground
1
0
0
12
Wildlife AF PC: 2 AF PR: 0 AF PO: 1 PV: 200
1.5 (0.8)
0.6
-0.5 to 3.0 (-0.5 to 1.2)
-0.4 to 1.3 (-0.3 to 0.5)
82.3% (64.2%)
-3.7% (-4.4%)
Birdstrike
2
0
1
165
Other
0
0
0
10
Animal strike
0
0
0
26
Other AF PC: 0 AF PR: 0 AF PO: 0 PV: 1
0.0 (0.0)
0.0
0.0 to 0.0 (0.0 to 0.0)
0.0 to 0.0 (0.0 to 0.0)
N/A (N/A)
0.0% (0.0%)
Other
0
0
0
1
Table B7: Infrastructure related Angel Flight (Passenger carrying and combined) occurrences ordered by largest statistical differences to other private operations, 2008 to 2017 (Total occurrences: AF PC: Σ0, AF PR Σ0, AF PO: Σ0, PV Σ14)
Occurrence grouping
Occurrence types
Occurrences per 10,000 flights
95% CI AF - PV
67% CI AF - PV
P AF > PV
PD
Occurrences
Minor occurrence grouping
AF PC (All AF)
PV
AF PC (All AF)
AF PC (All AF)
AF PC (All AF)
AF PC (All AF)
Occurrence Type
AF PC
AF PR
AF PO
PV
Runway lighting AF PC: 0 AF PR: 0 AF PO: 0 PV: 4
0.0 (0.0)
0.0
0.0 to 0.0 (0.0 to 0.0)
0.0 to 0.0 (0.0 to 0.0)
N/A (N/A)
-0.2% (-0.2%)
Runway lighting
0
0
0
4
Aerodrome related AF PC: 0 AF PR: 0 AF PO: 0 PV: 7
0.0 (0.0)
0.0
0.0 to 0.0 (0.0 to 0.0)
0.0 to 0.0 (0.0 to 0.0)
N/A (N/A)
-0.3% (-0.3%)
Other
0
0
0
7
Other AF PC: 0 AF PR: 0 AF PO: 0 PV: 10
0.0 (0.0)
0.0
0.0 to 0.0 (0.0 to 0.0)
0.0 to 0.0 (0.0 to 0.0)
N/A (N/A)
-0.4% (-0.4%)
Other
0
0
0
10
Appendix C – Angel Flight occurrence summaries
The following tables show the summaries of each reported incident or accident identified as occurring on either a passenger carrying flight (Table C1), a repositioning flight prior to a passenger carrying flight (Table C2) or a repositioning flight post a passenger carrying flight conducted on behalf of Angel Flight Australia (Table C3). These incidents were identified using the techniques described in Appendix A, and all were reviewed manually to positively confirm the records related to Angel Flight organised flights.
Table C1: Summaries of reported safety occurrences during private passenger carrying flights conducted on behalf Angel Flight, 2005 to 2017
While the aircraft was en route at 7,500 ft in IMC, the alternator failed. The pilot elected to divert to Nowra for a landing without incident.
200506574
Incident
0
10 Dec 2005
19km E Chinchilla
Systems: Electrical
While en-route, the aircraft's alternator failed. The pilot advised ATC that the radio equipment had to be shut down due to the problem. They issued the pilot with a discreet transponder code and the aircraft proceeded to Archerfield without further incident.
200506905
Incident
0
27 Dec 2005
Coffs Harbour, Aerodrome
Runway events: Runway Incursion
While taxiing after landing, the aircraft crossed runway 10 without clearance.
During the landing roll, the right main tyre deflated. The pilot stopped the aircraft on the runway strip and the wheel fairing was removed before the aircraft was towed clear.
The pilot reported that shortly after turning onto the assigned SID heading within the GAAP CTR, his aircraft was overflown by another aircraft in close proximity.
When the landing gear was selected down, the pilot received an unsafe landing gear indication and diverted to Canberra. ATC declared a local standby for the aircraft's arrival.
200705246
Incident
0
11 Aug 2007
Bankstown Aerodrome
Runway events: Runway Incursion
The aircraft entered the runway without clearance. ATC instructed an aircraft on final approach to go around.
200707377
Incident
0
23 Oct 2007
Essendon Aerodrome, 050° M 15Km
Missed approach / go-around: Missed approach / go-around; Communications: Air-ground-air; Aircraft separation: Loss of separation assurance
While the aircraft was on approach, ATC could not establish communication with the pilot. A green light was displayed for a landing clearance, but the aircraft conducted a go-around. Communications were subsequently re-established.
200707648
Incident
0
5 Dec 2007
Bankstown Aerodrome
Runway events: Runway Incursion
The aircraft entered the runway without a clearance.
200800346
Incident
0
20 Jan 2008
Bankstown Aerodrome
Wildlife: Birdstrike
During final approach, the aircraft struck a bird that impacted the left main windscreen.
During the climb, the pilot incorrectly readback the assigned level. The trainee and supervising controller did not detect the incorrect readback. As the aircraft climbed through the assigned level the CLAM activated.
200806888
Incident
0
20 Oct 2008
Williamtown Aerodrome, N M 4Km
Aircraft separation: Loss of separation; Operational Non-compliance: Verbal instruction; Operational Non-compliance: Published information; Operational Non-compliance: Operational Non-compliance; ANSP Operational error: Information / procedural error
The pilot of the PA-28 was instructed to maintain runway heading after departure, but was subsequently observed to turn left. This resulted in an infringement of separation standards with a formation of F/A-18s operating in activated airspace 2 NM to the north. To avoid further conflict, the pilot of the PA-28 was given a heading away from the airspace, resulting in the aircraft operating below the minimum safe altitude in IMC.
200807761
Incident
0
1 Dec 2008
Benalla Aerodrome, E M 15Km
Interference with aircraft from ground: Interference with aircraft from ground; Encounter with RPA: Near encounter with RPA
During cruise at 7,000 ft, the pilot sighted a model aircraft at the same altitude. When the model aircraft turned towards the PA-34, the pilot took immediate evasive action.
During works on the runway 10 strip, the safety vehicle and the workers were located within the runway strip while an aircraft took off on runway 10. The safety officer did not hear the required taxi broadcast from the pilot.
While inbound, the pilot was instructed to join crosswind for runway 29R. The pilot read back the instruction correctly, but the aircraft was subsequently observed to be on a left downwind for runway 29L.
While inbound, the pilot reported at Prospect Reservoir and was issued tracking and circuit joining instructions relevant to the reported position. The aircraft was subsequently observed by ATC to be approximately 4 NM SSW of Prospect.
200907403
Accident
0
29 Nov 2009
Tara (ALA)
Aircraft control: Loss of control; Weather: Other; Ground operations: Collision on ground; Runway events: Runway Excursion; Terrain Collisions: Ground strike; Terrain Collisions: Collision with terrain
On touchdown, the aircraft encountered a small whirlwind which caused the aircraft to lift, rotate, and depart the runway. The aircraft subsequently collided with a drain and the propeller struck the ground. The aircraft was seriously damaged.
200907574
Incident
0
2 Dec 2009
Moorabbin Aerodrome
Runway events: Runway Incursion
After landing on runway 35R, the aircraft entered runway 31L without a clearance.
201000279
Incident
0
13 Jan 2010
Brewarrina Aerodrome, E M 19Km
Airframe: Windows; Airframe: Objects falling from aircraft
While on descent, the right emergency exit window detached from the aircraft.
201002067
Incident
0
20 Mar 2010
near Inverell Aerodrome
Systems: Other
During cruise, the vacuum pump failed. The pilot reported operations were normal and continued to Inverell.
The Cessna 210 (C210) was cleared outbound on the 200 omni radial and the SF-340 was cleared inbound on the 219 omni radial. The C210 tracked right and approached the 215 radial conflicting with the SF-340. Vertical separation was maintained throughout.
During taxiing, the crew did not comply with an instruction to hold position and the aircraft entered the runway without a clearance.
201103806
Incident
0
29 May 2011
Bankstown Aerodrome
Aircraft separation: Loss of separation; Aircraft separation: Loss of separation
The Cessna 550 was cleared to land while the Piper PA-28 was still partially within the runway strip resulting in a loss of runway separation.
201105079
Accident
3
15 Aug 2011
Horsham Aerodrome, 352.5° M 31Km
Flight preparation / Navigation: VFR into IMC; Terrain Collisions: Collision with terrain; Aircraft control: Loss of control
During the flight, the aircraft collided with terrain. The three occupants were fatally injured and the aircraft was destroyed. It was determined that the pilot probably encountered reduced visibility conditions approaching Nhill due to low cloud, rain and diminishing daylight, leading to disorientation, loss of control and impact with terrain.
The aircraft landed on an incorrect runway without a clearance.
201108462
Incident
0
9 Dec 2011
Sydney Aerodrome, 250° M 9Km
Aircraft separation: Loss of separation; Aircraft separation: Loss of separation; Airspace infringement: Controlled airspace; Airspace infringement: Airspace infringement; Operational Non-compliance: Operational Non-compliance
A S.O.C.A.T.A. Groupe Aerospatiale TBM 700 aircraft, registered VH-VSV (VSV) on a private flight was cleared to depart Bankstown control zone on a downwind departure from runway 11 left, however mistakenly conducted an upwind departure. The aircraft penetrated Sydney controlled airspace by 2.3 NM and came within 1.2 NM with no vertical separation of another aircraft on approach into Sydney Airport and a breakdown of separation occurred. This incident highlights the importance of developing a technique to ensure a clearance is processed, understood and actioned correctly. It is also important to clarify a clearance if any ambiguity exists. Finally, pre-flight planning is essential to ensure safe flight. CASA has published a Visual Pilot Guide for Archerfield, Jandakot, Melbourne, Parafield and Sydney areas to provide detailed assistance for operating in these areas.
During approach, the nose landing gear failed to extend and the aircraft returned to Moree. Engineers replaced an o-ring.
201206658
Incident
0
5 July 2012
Mangrove Mountain (ALA), 340° T 20Km
Powerplant / propulsion: Partial power loss / rough running; Powerplant / propulsion: Engine failure or malfunction
During the cruise, the left engine began to run roughly and the pilot shut down the engine. An inspection found a broken exhaust valve in the number two cylinder.
201300547
Incident
0
20 Jan 2013
Bankstown Aerodrome
Runway events: Runway Incursion
The aircraft entered a runway without a clearance.
201300955
Incident
0
31 Jan 2013
Sydney Aerodrome, 297° M 39Km
Flight preparation / Navigation: Lost / unsure of position; Airspace infringement: PRD; Airspace infringement: Airspace infringement
The aircraft entered controlled airspace without a clearance. ATC subsequently provided the crew with navigational assistance.
During climb, the pilot did not adhere to an ATC communication instruction.
201302684
Incident
0
20 Mar 2013
Oakey Aerodrome, W M 56Km
Flight preparation / Navigation: VFR into IMC
During cruise, the cloud layer became unbroken below the aircraft operating under VFR and the crew requested assistance from ATC to find a safe location to commence a descent. The aircraft subsequently descended through cloud with the assistance of ATC and the crew of a military helicopter operating in the area.
During the initial climb, the landing gear failed to retract. The crew conducted troubleshooting before returning to Bankstown. On short finals, the tower advised HPR to ‘check wheels’, the pilot confirmed that the green down and locked light was still illuminated and that the gear selector was in the down position. On landing, the landing gear collapsed and the aircraft sustained substantial damage. The landing gear mechanism was visually inspected and the worm drive was almost to the full retraction position, indicating the gear was retracted electrically. The reason for this electrical retraction despite the gear selector being in the down position was not determined.
During the approach, the pilot received unsafe landing gear indications and conducted a fly-by. Ground observers advised that the landing gear appeared to be down and locked. An investigation did not find any faults with the landing gear system and it was established that the three green indication lights were not visible due to the automatic dimming of the cockpit navigation lights.
201308964
Incident
0
16 Sept 2013
Moorabbin Aerodrome
Airframe: Landing gear / Indication
During approach, the crew recieved an unsafe nose landing gear indication. The engineering inspection revealed that a microswitch was not engaging due to a bent bracket.
201311746
Incident
0
27 Nov 2013
Jandakot Aerodrome
Airframe: Landing gear / Indication
During landing, a tyre deflated.
201401148
Incident
0
28 Jan 2014
near Jandakot Aerodrome
Systems: Electrical; Other: Other
During the cruise, the alternator failed. The pilot conducted a fly-by inspection to confirm that the landing gear was extended.
201407749
Incident
0
26 Aug 2014
Bankstown Aerodrome
Wildlife: Birdstrike
Passing 50 ft on final approach, the aircraft struck a bird.
201409556
Incident
0
4 Nov 2014
Bankstown Aerodrome
Aircraft separation: Loss of separation; Operational Non-compliance: Operational Non-compliance; Aircraft separation: Loss of separation
The inbound Piper PA-30 did not track as instructed by ATC which resulted in a loss of separation with the departing Beech 35.
201500555
Incident
0
22 Jan 2015
Cowra Aerodrome, WSW M 37Km
Powerplant / propulsion: Engine failure or malfunction
During cruise, the pilot detected abnormal engine indications and a loss of power from the right engine. The engineering inspection revealed a faulty inlet valve in the No. 1 cylinder.
The Piper PA-34 entered the runway without a clearance and the controller instructed the crew of the Bombardier DHC-8 on final approach to conduct a missed approach.
The Cessna 210 entered runway 29 without a clearance. The controller instructed the crew of the Alpha Aviation R2160 on approach to the same runway to conduct a missed approach.
201508190
Incident
0
25 Nov 2015
Williamtown Aerodrome
Aircraft separation: Loss of separation; Aircraft separation: Loss of separation
The controller cleared the Raytheon B200 to descend to FL 110 while the Beech 35 was in cruise at 10,000ft AMSL. This resulted in a loss of separation due to the QNH transition level at the time.
201505886
Incident
0
9 Dec 2015
Bankstown Aerodrome
Airframe: Landing gear / Indication; Miscellaneous: Other
During the descent, the landing gear extended uncommanded and the pilot conducted a fly-by inspection prior to landing. The engineering inspection revealed the pressure line to the undercarriage pressure switch had failed.
During approach in IMC, the aircraft descended below the lowest safe altitude on several occasions and ATC had difficulty contacting and maintaining communications with the pilot.
201602694
Incident
0
19 May 2016
Moorabbin Aerodrome
Runway events: Runway Incursion
During taxi, the aircraft entered runway 31L without a clearance.
201700715
Incident
0
9 Feb 2017
Adelaide Aerodrome
Airspace infringement: Airspace infringement; Aircraft separation: Loss of separation; Aircraft separation: Loss of separation
During cruise, the Diamond DA40 infringed controlled airspace resulting in a loss of separation with the Piper PA-32.
201702311
Incident
0
15 May 2017
Adelaide Aerodrome
Runway events: Runway Incursion
After landing, the pilot did not contact ATC for clearance and subsequently entered runway 12 without a clearance.
201702907
Accident
3
28 June 2017
Mount Gambier Aerodrome, 202.37° T 5Km (Suttontown)
Terrain Collisions: Collision with terrain; Flight preparation / Navigation: VFR into IMC; Aircraft control: Loss of control
The aircraft collided with terrain and the pilot and two passengers were fatally injured. The investigation is continuing.
Table C2: Summaries of reported safety occurrences during private flights prior to passenger carrying flights conducted on behalf Angel Flight, 2005 to 2017
ATSBReferenceNumber
Occurrence Category
Fatal Injuries
Date
Location
OccurrenceTypes
ATSBSummary
200502940
Incident
0
21 June 2005
Tamworth, Aerodrome
Flight preparation / Navigation: VFR into IMC
During the aircraft's arrival, ATC observed the VFR aircraft frequently fly through cloud in IMC. The pilot advised being IFR capable but did not change the flight category to IFR.
While the aircraft was en route, the transponder failed.
200605438
Incident
0
14 Sept 2006
Essendon, Aerodrome
Runway events: Runway Incursion
The aircraft was taxied for takeoff and entered runway 35 without a clearance.
200706488
Incident
0
15 Oct 2007
Mansfield (ALA), 217° M 20Km
Diversion / return: Diversion / return; Powerplant / propulsion: Partial power loss / rough running; Powerplant / propulsion: Engine failure or malfunction
While on climb passing FL130, the engine failed. Power was restored during the enforced descent. The aircraft diverted to an adjacent airfield and landed safely. Engineering inspection revealed a faulty waste gate controller and actuator.
200803246
Incident
0
14 May 2008
Moorabbin Aerodrome
Runway events: Runway Incursion
While taxiing for takeoff, the aircraft entered runway 35L without a clearance.
While the aircraft was en route, the electrical system failed. The pilot diverted the aircraft to Tamworth for a landing.
200808252
Incident
0
20 Dec 2008
Moorabbin Aerodrome
Runway events: Runway Incursion; Aircraft separation: Loss of separation; Aircraft separation: Loss of separation
The Cessna 172 was observed by ATC to have crossed the holding point for runway 17R without a clearance, resulting in an infringement of separation standards with a Cessna 182 departing from that runway.
200907176
Incident
0
19 Nov 2009
Sydney Aerodrome, 282° M 48Km
Airspace infringement: Controlled airspace; Aircraft separation: Loss of separation; Airspace infringement: Airspace infringement; Aircraft separation: Loss of separation
The Piper PA-28 was observed by ATC to have entered controlled airspace without a clearance, resulting in an infringement of separation standards with a Mooney M20J.
During the approach, the crew received an unsafe landing gear indication and conducted a missed approach. The subsequent engineering inspection revealed a sticking squat switch.
After landing on runway 35R the aircraft vacated onto runway 31R without a clearance.
201501073
Incident
0
5 Feb 2015
Gold Coast Aerodrome, 230° M 6Km
Runway events: Depart / App / Land Wrong Runway
The aircraft did not track in accordance with ATC instructions and joined the circuit for an incorrect runway.
201502590
Incident
0
13 May 2015
Archerfield Aerodrome, 260° M 24Km
Aircraft separation: Loss of separation; Aircraft separation: Loss of separation; Airspace infringement: Airspace infringement
The outbound Beech A36 entered controlled airspace without a clearance resulting in a loss of separation with the inbound Beech B200.
201505500
Incident
0
26 Nov 2015
near Armidale Aerodrome
Aircraft separation: Airborne collision alert system warning; Aircraft separation: Issues; Aircraft separation: Airborne collision alert system warning; Aircraft separation: Issues
During the approach, ATC advised the crew of the SAAB 340 of an aircraft on a conflicting track, that was subsequently identified at the Piper PA-28. The 340 crew established communication and mutual separation with the PA-28 crew. The 340 crew subsequently received a TCAS RA on the PA-28 and manoeuvred to ensure that separation was maintained.
During taxi, the aircraft entered runway 12 without a clearance.
201700806
Incident
0
15 Feb 2017
Adelaide Aerodrome
Runway events: Runway Incursion
After landing on runway 23, the aircraft vacated the runway onto runway 12 without a clearance.
Table C3: Summaries of reported safety occurrences during private flights following to passenger carrying flights conducted on behalf Angel Flight, 2005 to 2017
ATSB Reference Number
Occurrence Category
Fatal Injuries
Date
Location
Occurrence Types
ATSB Summary
200503504
Incident
0
21 July 2005
Essendon, Aerodrome
Runway events: Runway Incursion
While it was taxiing for departure, ATC observed the aircraft to cross the holding point and enter the runway strip without a clearance.
200602754
Incident
0
1 May 2006
7km W Moorabbin, Aerodrome
Fumes, Smoke, Fire: Fumes
While the aircraft was on approach, the pilot detected electrical fumes in the cabin. The aircraft was landed without incident and submitted for maintenance.
While the aircraft was en route, the pilot reported a loss of oil pressure and considered returning the aircraft for a landing. The pilot subsequently reported that all systems seemed normal and the flight would continue to Bankstown. The pilot also reported that the fault could have been an electronic monitoring problem rather than a mechanical problem.
The aircraft was observed on radar descending without clearance to below LSALT. The pilot did not respond to calls from ATC until the aircraft passed 7,800 ft on descent to 7,000 ft in VMC. The pilot reported that the immediate descent was to escape severe turbulence. The pilot had received the SIGMET forecasting severe turbulence.
On 14 February 2007 at about 1127 Eastern Daylight-saving Time, the pilot of a Cessna Aircraft Company 182T (182) was positioning to conduct a sector entry for an area navigation (RNAV) global navigation satellite system (GNSS) arrival procedure to runway 06 at Camden Aerodrome, NSW. The aircraft was approaching the aerodrome from the east. At the same time, the pilot of a Cessna Aircraft Company 210L (210) was approaching Camden from the south-west with the intention of conducting a Camden runway 06 straight-in RNAV (GNSS) approach. The two aircraft had similar estimated times of arrival at the approach commencement waypoint. They were both being operated under the instrument flight rules (IFR), in Class G airspace. The air traffic controller provided the pilots with mutual radar based traffic information. The pilot of the 210 contacted the controller and was provided with traffic information about the 182. The pilot of the 182 climbed the aircraft to minimise the risk of a collision as he was unsure of the intentions of the pilot of the 210. Recorded radar data showed that, when the aircraft passed, there was 500 ft vertically and 2.1 NM laterally between them.
200702530
Incident
0
21 April 2007
Moorabbin Aerodrome, 37Km 025° M
Operational Non-compliance: Operational Non-compliance; Flight preparation / Navigation: Other
The aircraft was inbound to Moorabbin from the north-east. ATC advised the pilot to expect an NDB approach due low cloud at 800 ft and visibility 6 km in rain. The pilot replied that he could not fly the approach due to his documentation and approach charts being in the back of the aircraft. With IMC prevailing and the aircraft only having approximately 60 minutes fuel remaining, ATC declared an Alert Phase. When the aircraft was overhead Moorabbin, the pilot advised he had the airport in sight and could descend visually. The aircraft landed safely.
During cruise, the pilot found that the throttle could not be moved. The pilot declared a PAN and continued to Moorabbin. During descent, the engine was shut down due to excessive power at lower altitude. While on downwind the pilot restarted the engine and the aircraft landed safely.
200802722
Incident
0
24 April 2008
Bankstown Aerodrome
Wildlife: Birdstrike
During the landing roll, the aircraft struck a plover.
200802738
Incident
0
24 April 2008
Griffith Aerodrome, E M 37Km
Powerplant / propulsion: Partial power loss / rough running; Diversion / return: Diversion / return; Powerplant / propulsion: Engine failure or malfunction
During the cruise, the crew reported a rough running engine. The aircraft was returned to Griffith.
200805056
Incident
0
4 Aug 2008
Moorabbin Aerodrome
Runway events: Runway Incursion
The aircraft was observed by ATC to have entered the runway 35L strip without a clearance.
200806797
Incident
0
20 Oct 2008
Essendon Aerodrome
Runway events: Runway Incursion
The aircraft was observed by ATC to have entered the runway 17 strip without a clearance.
200900479
Incident
0
27 Jan 2009
Bankstown Aerodrome
Runway events: Runway Incursion
The aircraft entered the runway 29R strip without a clearance.
The pilot did not comply with the route clearance direct to Essendon. ATC issued a visual heading to assist the pilot.
200906344
Incident
0
16 Oct 2009
Moorabbin Aerodrome
Runway events: Runway Incursion
The aircraft entered runway 22 without a clearance.
201007041
Incident
0
6 Oct 2010
Essendon Aerodrome
Operational Non-compliance: Verbal instruction; Runway events: Runway Incursion; Aircraft separation: Loss of separation assurance; Operational Non-compliance: Operational Non-compliance; Aircraft separation: Loss of separation assurance
The Beech 35 crossed runway 35 without clearance when the Beech 200 was on 1 NM final for the runway and had been cleared to land. ATC cancelled the Beech 200's landing clearance until the Beech 35 had vacated the runway.
The pilot had requested navigational assistance from the controller prior to aircraft entering restricted airspace without a clearance. The aircraft was returning to Essendon due to an open door.
During cruise, the pilot diverted to Chinchilla due to low fuel indications and subsequently landed on a closed runway.
201504794
Incident
0
29 Oct 2015
Wollongong Aerodrome
As the Piper PA-34 was landing on runway 08, the Jabiru J170 started crossing the runway. The PA-34 crew applied heavy braking and stopped the aircraft short of the J170's position. The J170 crew subsequently reported that they had assumed that the PA-34 was landing on runway 34.
201603962
Incident
0
25 Aug 2016
East Sale Aerodrome
Aircraft separation: Loss of separation assurance; Breakdown of co-ordination: Breakdown of co-ordination
ATC cleared the military aircraft to climb into the adjacent sector before coordinating with the sector controller. As a result, a loss of separation assurance occurred with the Piper PA-32 in the adjacent sector.
201702322
Incident
0
15 May 2017
Adelaide Aerodrome, 0° M 9Km
Communications: Air-ground-air
The aircraft was not in normal communication with ATC.
During approach, the aircraft descended below its assigned level, resulting in ATC issuing a safety alert to a formation of super hornets on approach. The aircraft climbed back to its assigned level to maintain separation.
The objective of a safety investigation is to enhance transport safety. This is done through:
identifying safety issues and facilitating safety action to address those issues
providing information about occurrences and their associated safety factors to facilitate learning within the transport industry.
It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action.
Terminology
An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue.
Publishing information
Released in accordance with section 25 of the Transport Safety Investigation Act 2003
Ownership of intellectual property rights in this publication
Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia.
Creative Commons licence
With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence.
Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work.
The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau
Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.
Preliminary report
Report release date: 01/08/2017
This preliminary report details factual information established in the investigation’s early evidence collection phase and has been prepared to provide timely information to the industry and public. Preliminary reports contain no analysis or findings, which will be detailed in the investigation’s final report. The information contained in this preliminary report is released in accordance with section 25 of the Transport Safety Investigation Act 2003.
At about 0800 Central Standard Time[1]on 28 June 2017, a SOCATA TB-10 aircraft, registered VH-YTM (YTM), departed Murray Bridge Airport for Mount Gambier Airport, South Australia.
Position and altitude information obtained from OzRunways[2]showed that the aircraft’s inbound path (Figure 1) from Murray Bridge was straight and at an altitude of about 4,500 ft. At about 42 km north-north-west of Mount Gambier Airport, the altitude decreased and there was a significant deviation from the direct route. Several manoeuvres were then made at low altitude in the vicinity of the airport, including a possible attempted landing on runway 36. After a series of low-level turns, the aircraft landed on runway 29 at about 1008.
Figure 1: Approach path of VH-YTM showing the initial deviations from the direct flight path on the left, and the series of low level turns prior to landing on runway 29 on the right
Source: Google Earth and OzRunways, annotated by ATSB
The pilot then refuelled the aircraft and boarded two passengers, to conduct a flight to Adelaide arranged by the charity Angel Flight Australia.[3]The flight was to be conducted as a private flight under visual flight rules (VFR).
Witnesses in the vicinity of Mount Gambier Airport reported fog in the area at the time of landing and take-off. Similarly, CCTV footage showed the fog and reduced visibility conditions at the airport at the time of landing and take-off.
OzRunways data (Figure 2) and CCTV footage showed the aircraft took off from runway 24 at about 1020. Just after take-off, YTM veered to the left of the runway, at an altitude of approximately 300 ft above mean sea level (AMSL). The aircraft reached a maximum altitude of about 500 ft, 45 seconds after take-off. The last recorded information, about 65 seconds after take-off, showed the aircraft at an altitude of 400 ft.
A number of witnesses heard a loud bang, consistent with the aircraft’s impact with terrain.
Figure 2: Flight path of VH-YTM after departing runway 24 at Mount Gambier Airport, where each vertical line represents 5 seconds, and an indication of the wreckage location
Source: Google Earth and OzRunways, annotated by ATSB
Transmissions from the pilot of YTM on approach and take-off were recorded on the common traffic advisory frequency for Mount Gambier Airport. However, no emergency call was recorded. The aircraft was not equipped with a flight data recorder or cockpit voice recorder, nor was it required.
Minutes after impact the aircraft was found by witnesses passing the accident site, and emergency services responded to the scene shortly thereafter. The aircraft wreckage was located 212 m south of the last recorded position, just over 2 km from the departure runway (Figure 2). The pilot and two passengers were fatally injured, and the aircraft destroyed.
On-site examination of the wreckage and surrounding ground markings (Figure 3) indicated that the aircraft impacted terrain at approximately 30° from vertical, in an inverted attitude. The engine and propeller were located at the initial impact point. The fuselage and remainder of the aircraft had detached from the engine at the firewall, and came to rest in an upright position about 10 m beyond the engine, with the tail and wings attached. The wings had sustained significant impact damage to the leading edge. A strong smell and presence of fuel was evident at the accident site, however there was no evidence of fire. The aircraft did not have an emergency locator transmitter fitted, nor was it required. A portable locator beacon was found in the cockpit, but had not been activated.
Figure 3: Accident site looking north-west, showing the engine and propeller location alongside the left- and right-wing impact marks, about 10 m from the main wreckage, which is upright and facing in a north-north-easterly direction
Source: ATSB
Several components and documentation were removed from the accident site for further examination by the ATSB.
The investigation is continuing and will include examination of the following:
recovered components and available electronic data
aircraft maintenance documentation
weather conditions
pilot qualifications and experience
coordination and planning of the charity flight
the use of private flights for the transfer of passengers for non-emergency medical reasons
similar occurrences.
____________ The information contained in this web update is released in accordance with section 25 of the Transport Safety Investigation Act 2003 and is derived from the initial investigation of the occurrence. Readers are cautioned that new evidence will become available as the investigation progresses that will enhance the ATSB's understanding of the accident as outlined in this web update. As such, no analysis or findings are included in this update.
Purpose of safety investigations
The objective of a safety investigation is to enhance transport safety. This is done through:
identifying safety issues and facilitating safety action to address those issues
providing information about occurrences and their associated safety factors to facilitate learning within the transport industry.
It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action.
Terminology
An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue.
Publishing information
Released in accordance with section 25 of the Transport Safety Investigation Act 2003
Ownership of intellectual property rights in this publication
Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia.
Creative Commons licence
With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence.
Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work.
The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau
Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.
On 16 June 2017, a Pacific Aerospace Limited FU24 Stallion, registered VH-EUO, was conducting aerial agricultural operations from an airstrip 40 km north‑east of Bathurst, New South Wales. The purpose of the operations was to apply fertiliser and seed to private grazing land.
At about 1405 Eastern Standard Time,[1] the aircraft took off from the airstrip for the second flight of the second job of the day. When the aircraft did not return as expected, the loader raised the alarm and a search for the aircraft commenced at approximately 1600. Early the next morning, the wreckage of the aircraft was found in dense scrubland to the east of the application area. The pilot received fatal injuries as a result of the collision with terrain.
What the ATSB found
The ATSB found that shortly after the end of the third application run, the aircraft was flown into an area of rising terrain that was outside the normal operating area for that job site. While subsequently repositioning the aircraft for the fourth application run, it was likely that the aircraft aerodynamically stalled leading to a collision with terrain. Based on the available evidence, it was not possible to determine the reason for the loss of control.
Additionally, there was no evidence of any in-flight failure of the airframe structure or flight control systems. The engine appeared to have been producing significant power at impact.
Safety message
Operators and pilots are reminded of the dangers of aerial application near rising terrain and the importance of pre-flight planning of application runs to account for nearby terrain. Although it could not be established that not dumping the hopper contributed to this accident, in an emergency, reducing the aircraft’s weight by dumping the hopper load will optimise an aircraft’s flight performance.
The Aerial Application Association of Australia (AAAA) have published strategies in their pilot’s manual. With regard to the dumping of the load, the manual states ‘The only safe rule is ‘if in doubt, dump’.’
On 16 June 2017, a Pacific Aerospace Ltd FU24 Stallion, registered VH-EUO (EUO), was conducting aerial agricultural operations from a private airstrip at Redhill, 36 km north‑north‑east of Bathurst, New South Wales (NSW). The operations planned for that day involved the aerial application of fertiliser on three properties in the Upper Turon area of NSW (Figure 1).
Figure 1: Accident location
Source: Google, annotated by the ATSB
At about 0700 Eastern Standard Time[2] on the morning of the accident, the pilot and loader drove to Bathurst Airport to fill the fuel tanker and then continued to the worksite at the Redhill airstrip in the Upper Turon area, arriving at about 0830. Work on the first property started at about 0900, with the first flight of the day commencing at 0920. Work on the first property continued until 1350 with two refuelling stops at 1048 and 1250. Approximately 40 tonnes of fertiliser was applied on the first job.
In preparation for the second job, fertiliser and seed were loaded into the aircraft and maps of the second job area were passed to the pilot. At 1357, the aircraft took off for the first flight of the second job. The aircraft returned to reload, and at 1405 the aircraft took off for the second flight. A short time later, at 14:06:59, recorded flight data from the aircraft ceased.
When the aircraft did not return as expected, the loader radioed the pilot. When the loader could not raise the pilot on the radio, he became concerned and drove his vehicle down the airstrip to see if the aircraft had experienced a problem on the initial climb. Finding no sign of the aircraft, he returned to the load site, while continuing to call the pilot on the radio. He then drove to the application area to search for the aircraft before returning to the load site. With no sign of the aircraft, the loader called emergency services to raise the alarm. By about 1500, police had arrived on site and a ground search commenced. A police helicopter also joined the search, which was eventually called off due to low light.
The next morning, at about 0630, the search recommenced and included NSW Police State Emergency Service personnel, and local volunteers. At about 0757, the wreckage of the aircraft was found in dense bush on the side of a hill to the east of the application area. The pilot was found deceased in the aircraft. The aircraft was found approximately 17 hours after the last recorded flight data and there were no witnesses to the accident.
Figure 2: Area of operations
Figure 2 shows the area of operations including Red Hill airstrip and the location of the wreckage. The red shaded areas shows the approximate area of application for the first and second job sites. Source: Google, annotated by ATSB.
The pilot held a Commercial Pilot Licence (Aeroplane) issued on 11 August 2008 and an Aerial Application Rating (Aeroplane) Grade 2. A review of the pilot’s logbooks showed that his flying experience was predominately in survey operations. He had completed his low level and aerial mustering endorsements on 2 June 2009 and subsequently obtained his Grade 2 agricultural (aerial application) operational rating on 13 May 2011.
The pilot’s logbook showed a total of 4,688 hours flying experience. Of this, 786 hours were on the FU-24 Fletcher aircraft and 1,001 hours were on the Pacific Aerospace Corporation (PAC) 750XL. The former of these two aircraft is a piston-powered version of the Stallion airframe, while the PAC 750XL is also a similar airframe to the Stallion, but fitted with a Pratt & Whitney Canada PT6 turboprop engine. On 19 May 2017, he obtained a FU-24 Stallion (turbine-powered) aircraft endorsement. A review of the pilot’s logbook and operator flight records indicated he had accrued about 43 hours in the FU-24 Stallion, all of which were within the 30 days before the accident.
Pilot training
Regulation 61.1130 of the Civil Aviation Safety Regulations 1998 requires that, after the initial issue of an aerial application endorsement,[3] a pilot is required to remain under direct[4] and indirect[5] supervision of an appropriately qualified pilot for at least 110 hours of aerial application operations. The initial 10 hours of this period shall be under direct supervision, while the following 100 hours is under direct or indirect supervision. The pilot’s logbook stated that 10 hours of direct supervision had been completed as at 8 April 2017 and 90 hours of indirect supervision had been completed as at 18 May 2017. The pilot had accumulated an additional 43 hours of agricultural flying since being signed-off. The operator advised that these hours would have satisfied the requirements of indirect supervision required by regulation 61.1130.
The pilot obtained the aircraft endorsement for the Honeywell (formally Garrett) TPE331-powered FU-24 Stallion on 19 May 2017. The Chief Pilot reported that he flew with the pilot a couple of times during this process and assessed the pilot as being competent on the type. Exposure to the aircraft’s stall characteristics and recovery methods was not part of this process, nor was it required to be.
Medical information
The pilot held a Class 1 Aviation Medical Certificate that was valid until 29 July 2017, with no restrictions. The pilot was reported to be a non-smoker who exercised regularly and rarely drank alcohol. Additionally, he reportedly displayed normal behaviour on the morning of the flight and was well-rested. He was not reported to be taking any prescription medications and had no reported medical condition that could have affected his ability to operate an aircraft that day.
A post-mortem examination identified no significant background natural disease, which could have contributed to the accident. Toxicological analysis concluded that the toxicology was also non‑contributory to either the accident or cause of death.
Aircraft information
Overview
VH-EUO (EUO) (Figure 3) was a Fletcher FU-24 Stallion agricultural aircraft manufactured in 1980 in New Zealand by Pacific Aerospace, formerly Air Parts (NZ). The aircraft was a conventional low-wing monoplane with tricycle undercarriage, aluminium construction and pronounced dihedral[6] on the outer wing panels. Side-by-side seating was forward of the wings and a hopper was located inside the fuselage, in line with the wings. EUO was first registered in Australia in 1980 and was operated in the ‘agricultural’ operational category, later defined as ‘aerial work’. The certificate of registration was transferred to the current owner on 18 April 2017.
Figure 3: Image showing VH-EUO
Figure 2 shows VH-EUO, a turbine-powered FU-24 Stallion. In the background is a piston-powered FU-24 Fletcher.
Source: Operator.
While undergoing repairs following an accident in 1993,[7] the aircraft was modified under supplemental type certificate (STC) 209. The modification involved replacing the Lycoming IO-720 piston engine with a Honeywell TPE331 turbine engine, including associated structural and avionics modifications. The Hartzell constant speed propeller was also replaced with a McCauley C661 series propeller in accordance with supplemental type certificate (STC) 209-1. EUO was returned to service in 1996.
Following an incident in 2001, an overhauled TPE331 engine was installed and EUO was returned to service in February 2002. A review of the aircraft maintenance logbooks identified no other major repairs. Only records from 1 March 2000, however, were made available to the ATSB.
EUO was maintained by a CASA-authorised maintenance facility and in accordance with an approved system of maintenance. A periodic inspection was completed on 4 May 2017, at 11,004.8 hours total time in service (TTIS). The current maintenance release (MR) was issued at that time, authorising EUO for aerial work operations in day VFR[8] conditions. This maintenance release was valid for 1 year or 100 hours, whichever came first. Before the first flight on 16 June 2017, the aircraft had 11,059.8 hours TTIS, meaning the maintenance release was valid at the time of the accident.
Stall warning system
The aircraft was equipped with a stall warning system, which was designed to illuminate a light in the cockpit. It also had an audible warning, which produced a steady signal approximately 5‑10 kt before the stall in all configurations.
Aircraft weight and balance
The maximum take-off weight (MTOW) for the aircraft in the normal category was 2,204 kg. Operations in the agricultural category allowed for an increase in the MTOW to 2,463 kg. Weight calculations, based on performance data provided by the operator, indicated the aircraft was below the agricultural MTOW at take-off for the accident flight. Further, the aircraft was within the weight and balance envelope at the time of the accident.
Meteorological information
Area weather forecasts (ARFOR)[9] that encompassed the area of operations, together with the aerodrome forecasts (TAF) and meteorological aerodrome report (METAR)[10] for both Bathurst and Mudgee Airports, were obtained from the Bureau of Meteorology. The forecasts predicted no significant weather in the area of operations for the duration of the accident flight. The METAR for Bathurst Airport (about 34 km south‑south‑west of the accident site) indicated that at 1400, the surface wind was 320° (true) at 1-3 kt, with a QNH[11] of 1023.5 and the conditions were CAVOK.[12] Similar conditions were observed at Mudgee Airport (about 68 km north‑north‑west of the accident site) with the METAR reporting that at 1400 that the surface wind was 020° (true) at 4-6 kt with a QNH of 1022.9. Conditions at Mudgee were also CAVOK.
Observations of the conditions on the day were consistent with these reports, with the aircraft loader reporting that conditions at the time of the accident were overcast with high clouds, well above the highest ridge. He also recalled that wind on the day was light and variable.
Wreckage and accident site information
Accident site
The accident site was located about 40 km north‑north‑east of Bathurst, in the Upper Turon area of New South Wales (Figure 1). A ridgeline running approximately north-south was located on the eastern edge of the property where EUO was conducting flight operations on the day of the accident (Figure 4). Knights Gully lies to the east of this ridgeline, flowing northward to join the Turon River. The terrain on the west side of Knights Gully rises from about 746 m at the eastern edge of the operating area to about 1,007 m over about 1.15 km. The wreckage of EUO was located about 220 m in from the eastern edge of the operation area and part way up an approximately 28˚ slope rising to the north. Elevation of the site was about 790 m and the aircraft was oriented with the nose toward 286˚ (approximately west‑north‑west). The surrounding terrain rose in both the south to north and west to east directions.
Figure 4: Topographical map showing the area of operations
Figure 4 shows the area of operation in relation to a ridgeline to the east of the application area.
Source: Map data: Google, annotated by ATSB
The accident site was located in a wooded area, with tree heights of about 10 m (Figure 5). Site examination indicated that the final aircraft trajectory was approximately 35˚ downwards in a steep nose-down attitude. Several large trees about 3 m from the initial ground impact halted forward momentum of the aircraft.
Figure 5: The accident site
Source: ATSB
Wreckage examination
The aircraft was examined for pre-impact defects, with none identified that were likely to have influenced the accident sequence. All of the aircraft and its components were accounted for at the accident site. There was no indication of any fire. The forward fuselage, including engine and cabin, was compressed and twisted. The condition of the wreckage, with minimal structural damage to the fuselage, in addition to the short length of the wreckage trail, was indicative of a relatively low energy impact. These observations are consistent with an aircraft that had stalled at a low level and collided with terrain at low horizontal speed.
All primary and secondary flight control surfaces were identified in the wreckage trail. Additionally, all control cables were attached to either the appropriate control surface or control mechanism. Cables that were fractured were identified as having failed due to overstress, consistent with impact forces.
All primary flight instruments were identified in the main portion of the wreckage. A number of electronic devices, including a TracMap GPS (see the next section titled Recorded flight data) were retrieved from the accident site for further examination.
On-site examination of both the engine and propeller did not identify any mechanical defects that may have contributed to the accident. Damage to the propeller blades and a number of severed branches indicated that at the time of the accident, the engine was producing significant power.
Fuel
The aircraft was refuelled throughout the day via a fuel tanker located at the airstrip. This tanker had uplifted Jet A-1 from Bathurst Airport on the morning of 16 June 2017. The aircraft was fully fuelled the day before, as well as twice on the day of the accident. The last refuel was at 1250, approximately 77 minutes before the accident. The endurance of the aircraft was about 120 minutes. A fuel sample was not available at the accident site due to the significant disruption of the aircraft fuel tanks, however, first responders and ATSB investigators identified a strong smell of fuel at the accident site. A sample of fuel was taken from the tanker and found to be clear with no water contamination. In addition, there were no reports of fuel quality concerns from Bathurst Airport fuel users.
Hopper load
An on-site visual inspection of the aircraft’s hopper identified that the hopper was approximately half-full. The operator also inspected the wreckage and advised that the amount remaining corresponded to approximately half of what the aircraft was loaded with for the accident flight, which was consistent with the operator’s reporting that each application run used approximately half the loaded amount (see Figure 7 for details of application runs).
Additionally, the on-site inspection found that the hopper outlet control quadrant was at the lower ‘closed’ end of travel and the dump control mechanism was observed to be fully forward (closed) position. The position of these levers and the half-load in the hopper are indicative of the hopper’s contents not being dumped or applied in the lead-up to the collision with terrain.
Additional information
Recorded flight data
The aircraft was fitted with a TracMap Flight GPS device. The in-aircraft device, which forms part of the TracMap job management system, logged GPS flight data as well as fertiliser application coverage data. The damaged device was recovered from the wreckage and sent to the manufacturer for download. Flight data for work undertaken on June 16, provided by the TracMap manufacturer, is shown in Figure 6 and Figure 7. When questioned about the time at which the unit stopped recording data, the manufacturer advised that the unit had a buffering time of 60 seconds. This meant that once data was recorded to volatile memory,[13] it took 60 seconds for that data to be transferred to non-volatile memory.[14]
Figure 6 shows TracMap data for the flights involved in the first job on 16 June. Work on this job started at about 0900 and continued until about 1350. During this time, two hot refuels[15] were conducted, one at 1048 and one at 1250. Approximately 40 tonnes of fertiliser was applied during this job.
Figure 6: TracMap data of the flights involved in the first job on 16 June
Figure 6 shows the aircraft’s flight tack (shown in green) as well as the areas where fertiliser was applied (shown in orange).The red shaded area shows the approximate area of application for this job. Also shown by the annotation is the location of the Red Hill airstrip.
Source: Google, annotated by ATSB.
TracMap data for the penultimate flight and the accident are shown in Figure 7. Data for the penultimate flight (shown in white) shows the aircraft taking off to the north and turning east to the job site. The aircraft then circles, perhaps to confirm the location of the application area, and then proceeds to the east across the northern border of the application area. The coverage data, shown in orange, shows that fertiliser was applied for 49 seconds on the first run to the east. At the end of the first run, the aircraft turned to the north to avoid the ridgeline, circled back, and applied fertiliser for 30 seconds on the second run before landing to reload with fertiliser and seed.
Figure 7: TracMap data of the penultimate flight (shown in white) and the accident flight (shown in red)
Figure 7 shows TracMap flight data for the accident flight in red and the previous flight in white. Areas on the previous flight where fertiliser was applied are shown in orange. The red shaded area shows the approximate area of application for this job. Also shown by the annotations are the Red Hill airstrip and the location of the wreckage.
Source: Google Earth, annotated by ATSB.
Data for the accident flight, identified in red in Figure 7, showed the aircraft taking off to the north at 1405. This time the aircraft turned earlier to the southeast before turning back to the northeast on a track similar to that of the previous flight. At 14:06:59, just before the aircraft reached the application area (the shaded red area in Figure 7), recorded flight data ceased. About 17 hours later, the wreckage of the aircraft was found about 3 km to the east of the last recorded position.
Analysis of the TrackMap data of the procedure turn conducted on the penultimate flight (Figure 7), as well as a number of standard procedure turns conducted on the previous job (Figure 6), indicated that it took the pilot between 30 and 35 seconds to reposition the aircraft safely onto a reciprocal track using a procedure turn. Additionally, analysis of a number of previous flights by the pilot that day indicated that application runs were conducted at an average speed of 100 kt.
Operational information
A planning meeting for the work to be undertaken on 16 June was conducted on the afternoon prior between the pilot, the loader and the property owner. Risks associated with the job were discussed and the ridge to the east of the application area was identified as a potential hazard. The Bingletree job site (shaded red in Figure 7) was significantly longer in the east-west direction, than the north-south direction. As such, the operator noted that the normal procedure for this site would be to conduct runs in an east-west direction to minimise the number of turns that would be required. The chief pilot also indicated that when undertaking work on the Bingletree site, both prior to and after the accident, the runs were conducted in an east-west-east orientation.
The operator and the chief pilot both indicated that the normal procedure would have been to cut the run short of the end of the property and turn away from the ridgeline, in either a north or south direction, and then conduct a procedure turn to reposition the aircraft for the return run. The job would then be finished with a couple of north-south runs to fill in any gaps at the end of the job site.
Figure 7 shows that this is exactly what the pilot had done on the first flight of the Bingletree job. The first application run was conducted in an easterly direction. At the end of the first run the pilot turned north, away from the ridgeline, before conducting a procedure turn to reposition the aircraft for the return run in a westerly direction. If this procedure were continued for the rest of the job, there would have been no operational reason for the aircraft to enter the area of rising terrain to the east of the application area where the accident occurred.
While top dressing a property in the Upper Turon area of New South Wales, an Airparts NZ FU-24 ‘Stallion’, registered VH-EUO, entered an area of rising terrain shortly after the end of an application run. While repositioning the aircraft for the next application run, control of the aircraft was lost, resulting in a collision with terrain.
Site and wreckage examination did not identify any defects or anomalies that might have contributed to the loss of control. Additionally, a review of the pilot’s medical records, post-mortem and toxicology results indicated that it was unlikely that the pilot became incapacitated during the flight. Therefore, this analysis will focus on the examination of the operational factors that led to the loss of control.
Development of the accident
Timing of the accident
The recorded flight data ceased at 1406:59, 2,870 m from the eastern end of the application area. Analysis of previous flights by the pilot that day indicated that application runs were conducted at an average speed of 100 kt (51.4 m/s) and that procedure turns took about 30 to 35 seconds. Assuming the aircraft travelled at 100 knots and in a straight line, it would have taken about 56 seconds for the aircraft to travel from the point of last recorded flight data to the other side of the application area.
Given the buffering time of the TrackMap, it is very likely that the aircraft collided with terrain within 60 seconds of the last recorded flight data. This leaves only about 4 seconds for the aircraft to travel an additional 220 m to the accident site, turn onto a nearly reciprocal track and impact terrain. Given the required 30–35 second timeframe previously established, it is very unlikely that the pilot had sufficient time to conduct a procedure turn before colliding with terrain. It is therefore unlikely that this manoeuvre was achieved in a controlled manner in the timeframe available.
Loss of control
On-site examination indicated that the wreckage was consistent with the aircraft aerodynamically stalling at a low altitude resulting in a low speed, low-energy collision with terrain.
The investigation explored several possible factors that may have contributed to the loss of control, including birdstrike, pilot distraction, mishandling of a procedure turn, among others. In this instance, the evidence available was insufficient to make a determination.
The loss of control occurred shortly after the end of the third application run, while repositioning the aircraft for the fourth run. While the pilot was very experienced in aircraft similar to the Stallion, he had only accrued about 43 hours in EUO. It was likely the pilot would have had stall training in other aircraft types, however, the chief pilot reported that stalling the aircraft was not included as part of the endorsement on the Stallion aircraft (nor was it required to be). It is therefore likely that the pilot had never experienced a stall in the Stallion aircraft-type. Although the Stallion was fitted with an audible stall warning system, additional training may have given the pilot familiarity with the stall characteristics of the aircraft. In this case, however, it is unknown if the absence of type‑specific stall training influenced the development of the accident.
Findings
From the evidence available, the following findings are made with respect to the collision with terrain involving a FU24 Stallion, VH-EUO, 40 km north‑east of Bathurst, New South Wales on 16 June 2017. These findings should not be read as apportioning blame or liability to any particular organisation or individual.
Contributing factors
The pilot flew the aircraft into an area of rising terrain that was outside the normal operating area for this job site.
For reasons that could not be determined, the aircraft aerodynamically stalled and collided with terrain during re-positioning at the end of the application run.
Other findings
There was no evidence of any defect with the aircraft that would have contributed to the loss of control.
General details
Pilot details
Licence details:
Commercial Pilot Licence (Aeroplane), issued August 2008
Class 1 Aviation Medical Certificate, valid until 29 July 2017
Aeronautical experience:
4,688 hours
Last flight review:
7 November 2016
Sources and submissions
Sources of information
The sources of information during the investigation included the:
Civil Aviation Safety Authority (CASA)
operator
Bureau of Meteorology (BoM).
References
Aerial Application Association of Australia (AAAA), Aerial Application Pilots Manual 3rd Edition, 2011.
Submissions
Under Part 4, Division 2 (Investigation Reports), Section 26 of the Transport Safety Investigation Act 2003 (the Act), the Australian Transport Safety Bureau (ATSB) may provide a draft report, on a confidential basis, to any person whom the ATSB considers appropriate. Section 26 (1) (a) of the Act allows a person receiving a draft report to make submissions to the ATSB about the draft report.
A draft of this report was provided to CASA, the New Zealand Transport Accident Investigation Commission (TAIC), TrakMap, Pacific Aerospace, the operator and the chief pilot.
Submissions were received from the operator. The submissions were reviewed and where considered appropriate, the text of the report was amended accordingly.
Purpose of safety investigations
The objective of a safety investigation is to enhance transport safety. This is done through:
identifying safety issues and facilitating safety action to address those issues
providing information about occurrences and their associated safety factors to facilitate learning within the transport industry.
It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action.
Terminology
An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue.
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