On 21 November 2016, at about 0730 Eastern Daylight-saving Time (EDT), a Bell 206B helicopter, registered VH-CHO, took off from a property about 30 km south of Bathurst, New South Wales. The pilot was conducting an aerial inspection of the property, with the farm manager on board as a passenger.
After overflying a flat area on high ground, the pilot raised the collective[1] and turned the helicopter to follow down-sloping terrain. At about 75 ft above ground level and an airspeed of about 40 kt, the pilot and passenger heard and felt a bang. The pilot looked outside to see if there was any obvious damage to the spray booms on the helicopter and in the back seat to see whether anything had fallen onto the floor, and assessed that the helicopter was too high to have collided with anything outside.
The pilot initially decided to land as soon as possible in order to check the helicopter to determine the cause of the bang, and started to slow it down. As the airspeed decreased, the helicopter started to yaw rapidly to the right and the pilot, unable to arrest the rotation with left anti-torque pedal, realised they had lost tail rotor authority. The pilot immediately rolled the throttle to the ground idle detent and as the helicopter stopped yawing, lowered the collective. The pilot saw that the rotor rpm had dropped to about 80 per cent and prepared for a hard landing. The pilot cushioned the landing by pulling back on the cyclic,[2] but the helicopter landed heavily. The belly tank (for spraying) absorbed some of the impact of the landing. The spray booms (fitted to the aircraft for spraying operations) probably helped prevent the helicopter rolling over.
The electronic locator beacon activated on impact. The pilot and passenger sustained minor injuries and the helicopter was substantially damaged (Figure 1).
Figure 1: Accident site showing damage to VH-CHO
Source: Aircraft operator
Post-accident inspection
The tail rotor driveshaft had fractured at the No. 2 bearing (Figure 2).
The tail rotor blades were undamaged in the impact, which indicated that they were probably not rotating when the helicopter collided with the ground. There were scrapes inside the tail rotor driveshaft cowling, which indicates that the shaft was probably rotating when it fractured.
There was no evidence of oil leakage, overheating, or vibration of the tail rotor driveshaft system.
Figure 2: Fractured tail rotor driveshaft
Source: Aircraft engineer
Maintenance history
The helicopter had serial number 714, and was fitted with a long tail rotor driveshaft. The manufacturer required the single long driveshaft to be replaced with a segmented shaft in serial numbers 1252 and above.
The helicopter was fitted with a data augmentation monitoring system, which did not show any abnormalities.
The tail rotor bearings were ‘on condition’ items, that is, were required to be replaced if worn on inspection. The driveshaft was inspected every 1,200 hours and was in good condition apart from the fracture after the accident.
On 18 August 2016, the No. 1 and No. 3 tail rotor driveshaft bearings and tail rotor gearbox were replaced. On 29 September 2016, the No. 1 tail rotor bearing and bearing hanger were replaced. Post-accident inspection did not reveal any abnormalities.
Manufacturer comments
The helicopter manufacturer (Bell Helicopter) reported that the single long tail rotor driveshaft (P/N 206-040-330-001) was replaced with the segmented shafts in Bell 206B helicopters about 45 years ago. At serial number 1252, all Bell 206B helicopters and follow-on Bell 206B3 helicopters were equipped with segmented shafts. The change was made for ease of maintenance in replacing hanger bearings. In addition, if a segmented shaft was damaged, only it would have to be replaced and not the entire long shaft. The long shaft is still procurable through Bell Helicopter. The manufacturer reported that the long tail rotor driveshaft has not been a safety concern with no recent failures recalled.
Manufacturer investigation
The helicopter manufacturer inspected the tail rotor driveshaft and found that it fractured as a result of fatigue cracking. The origin of the fatigue was associated with an area of corrosion pitting, intergranular corrosion and associated cracking on the outside surface of the driveshaft tube, around both sides of the second hanger bearing inner ring location. The driveshaft was otherwise found to comply with the manufacturer’s requirements.
Pilot comments
The pilot provided the following comments:
When the pilot heard the bang, the helicopter was at a very high-power setting with the blades highly pitched. Although the pilot rolled the throttle off, it took a couple of seconds before the yawing stopped, then they put the collective down and by that time the rotor rpm had dropped.
There were about 30 gallons (114 litres) of fuel on board and the helicopter was loaded well within weight and balance limitations.
The temperature was 18.5 °C, the wind light and variable, and the elevation about 3,200 ft above mean sea level. The conditions were well within the performance limitations of the helicopter.
If the pilot had been able to get into a position where they could do a run-on landing, there may not have been any damage.
The pilot did not know the tail rotor authority was lost until it was too late to do anything other than land immediately.
Safety analysis
The pilot and passenger heard a bang, which was probably the tail rotor driveshaft failing in flight, as indicated by the scraping inside the tail rotor driveshaft cowling. This resulted in a loss of authority of the tail rotor, and the lack of tail rotor blade damage suggests the blades were (near) stationary at the time of ground impact. The manufacturer’s examination found that the driveshaft tube fractured as a result of fatigue cracking that was associated with an area of corrosion pitting on the outside surface of tube, adjacent to the location of the second hanger bearing. The pilot slowed the helicopter to make an approach to land and check out the cause of the bang, which caused the helicopter to start yawing to the right. The pilot then realised they had lost tail rotor authority, rolled off the throttle to stop the yaw, and as the rotor rpm had dropped they were then committed to an immediate landing.
Findings
These findings should not be read as apportioning blame or liability to any particular organisation or individual.
The tail rotor driveshaft tube fractured as a result of fatigue cracking that likely originated from corrosion pitting on its outside surface. This resulted in a loss of tail rotor authority.
The helicopter was low and slow when tail rotor authority was lost, limiting the time available for the pilot to assess the circumstances and manage the forced landing.
Safety message
This incident highlights the importance of robust and current training in emergency procedures. Being able to identify a problem and react quickly can reduce the severity of damage and injuries.
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 27 September 2016, a Pulse Aerospace Vapor 55[1] remotely piloted aircraft (RPA), was operating a test flight at Lighthouse Beach, Ballina, New South Wales (Figure 1).
According to telemetry data[2] recorded on the remotely piloted aircraft system’s ground control station (GCS), at about 0910 Eastern Standard Time (EST), the RPA lifted off from its start position in front of the surf clubhouse (Figure 2). About 30 seconds later, when the RPA was at an altitude of about 36 ft, it entered ‘manual’ flight mode. The RPA then tracked according to manual inputs from the pilot for about 7 minutes, at which time (when at 124 ft altitude) the data-link signal was lost. Thirty seconds later, the RPA entered the ‘home’ flight mode, and commenced tracking to the programmed home position at an altitude of 154 ft. The last position of the RPA recorded by the GCS was about 165 m NNE of the start position, and about 4 km SE of Ballina/Byron Gateway Airport.
In the home flight mode, the RPA did not respond to the flight control inputs made by the pilot and the pilot subsequently lost sight of the RPA. The RPA was not found despite an extensive search.
Figure 2: Recorded RPA track
Source: Google earth and remotely piloted aircraft system operator, annotated by ATSB
Mission planning
Prior to the flight, the pilot’s preparation for the planned mission involved using Google earth on a computer (not the GCS), and selecting a north-western and a south-eastern reference point. These markers defined an outer rectangle, within which the flight was to take place (Figure 3).
Figure 3: Planned operating area defined using NW and SE markers
Source: Google earth, annotated by ATSB
The pilot then transferred an image of the google earth map for the area onto the GCS using a USB stick, and uploaded it to create the ‘Lighthouse Beach’ mission. To georeference[3] the image, the pilot then overlaid the markers in the image with a point icon on the controller, and entered the latitude and longitude of two positions into the dialogue box on the GCS. The north-western GCS marker is visible in the top left corner of Figure 4, but the latitude and longitude values visible are image text only.
Once the image had been georeferenced, the pilot then used the graphical interface to place the start and home icons and any intervening waypoints for the planned mission (Figure 4).
Figure 4: Image uploaded onto GCS with planned mission overlaid
Source: Remotely piloted aircraft system operator, annotated by ATSB
Incorrect georeference
The remote pilot reported that both they and an observer checked each waypoint before the flight, verifying latitude, longitude, altitude and height. However, the GCS data shows that during the planning phase, while the north-western marker was correctly assigned, the south-eastern marker was incorrectly assigned to a georeference point with a latitude in the northern hemisphere. This resulted in all of the waypoints and home location being incorrect, as they were created by dragging icons on the georeferenced image. Waypoints 2, 3, 6 and 7 had latitudes in the northern hemisphere, and the home position was assigned to 17.222395° S and 153.591582° E. That location was in the Coral Sea Islands about 1,200 km north of the start position (Figure 5).
Figure 5: Actual location of home position and select waypoints from the GCS
Source: Remotely pilot aircraft system operator, Google earth
The RPA’s start position was correct as it was obtained using the RPA’s GPS. As the aircraft entered manual mode after take-off and the pilot did not initiate the automatic mode to fly the programmed mission, it was only when the RPA lost the datalink, stopped responding to the pilot’s manual control inputs and commenced tracking for the programmed home position, that it left the planned operating area. The pilot can also manually give the ‘home’ command. In all home and automatic modes, the handheld controller is ignored unless the pilot gives the ‘manual’ command via the GCS application and manually takes control of the RPA.
The GCS has a ‘flight plan’ tab, which shows the planned distance and time (among other items) for the mission, which could have alerted the pilot to the incorrect latitude references. However, a check of the flight plan tab had not been included in the operator’s pre-flight procedures. In addition, the flight plan tab includes a measure tool that can be used to check that the map size is correct.
The manufacturer advised that the following steps are included in their pre-flight procedure specified in the aircraft flight manual:
verify flight plans
verify lost communication home waypoint.
The operator stated that there was no further detail of the verification process in the manual.
The default hemisphere was north (N) in the GCS for entering positions. The manufacturer stated that there was no feature that would change the default (to south (S)). The manufacturer assessed that changing the default could lead to issues with the conduct of appropriate pre-flight checks.
The operator reported that information about the default setting to north was not provided in the Aircraft Flight Manual.
Loss of data-link signal
The RPA system commands homing after 10 seconds of data link loss when in automatic mode and 2 seconds if in manual mode. In this incident, as the RPA was in manual mode, it initiated homing after 2 seconds.
The cause of the lost signal could not be determined. The operator thought that there may have been interference from a media outside broadcast unit located about 30 m from the GCS. However, the media personnel advised the operator that they were using a satellite communications link and therefore should not cause interference.
Appropriate action
The manufacturer advised that once the aircraft commenced tracking to an incorrect home location, the appropriate action would have been to use the ‘hold’ or ‘manual’ command so that the joystick flight control could be used.
The remote pilot advised that they had attempted to use the ‘hold’ command, as they were shown in their training, but the RPA did not respond. No evidence of this was recorded in the GCS data.
Safety analysis
Although the pilot reported having completed the pre-flight preparations and associated checks, the data stored on the GCS showed that the incorrect (northern) hemisphere was assigned to the south-eastern georeference marker at the time the map image was created. This led to the home position being assigned a location in the Coral Sea Islands, so when the RPA lost signal and tracked for home, it headed north and was not recovered. The same outcome would have occurred if the pilot had selected the RPA to fly home, even with a continuous data-link signal. While all of the intermediate waypoints were also incorrect, as the GCS remained in manual mode, the RPA did not attempt to track to any of those waypoints.
Findings
These findings should not be read as apportioning blame or liability to any particular organisation or individual.
The south-eastern point used to georeference the image on the ground control station map was selected to a northern hemisphere latitude, which resulted in incorrect waypoints and home position for the mission.
The RPA data-link signal to the ground control station was lost, so it commenced tracking to the programmed home position, which was in the Coral Sea Islands at a latitude 17.22° S, about 1,200 km north of the start position.
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.
Manufacturer
As a result of this occurrence, the RPAS manufacturer has advised the ATSB that they are taking the following safety actions:
Audit of training curriculum to ensure that pilots understand how to verify GPS coordinates, interpret their values and signs. The training course will continue to train pilots on the tools available to them within, and outside of the GCS software.
Share this incident with operator trainers so that new operators can learn from the events of this incident.
Continued education and outreach discussions with RPAS operators pertaining to decreased mishap rates through training and currency policies.
Remotely piloted aircraft system operator
As a result of this occurrence, the remotely piloted aircraft system operator has advised the ATSB that they are taking the following safety actions:
The pre-launch checklists have been modified to include additional and enhanced procedures to verify data input and flight plans.
Investigate the fitting of either GPS or cellular tracking devices to remotely piloted aircraft.
Update the risk assessment form to include location of external broadcast stations such as television outside broadcast units.
Brief all company pilots on the event for safety and education purposes.
Continue liaison with the manufacturer.
Safety message
Incorrect reference data can have potentially serious consequences in remotely piloted and manned aircraft. It is imperative that remotely piloted aircraft systems incorporate means of minimising the opportunity for errors to occur and also for detecting and correcting errors that do occur.
The careful application of operational controls and procedures, underpinned by robust risk assessment, will become increasingly important as relevant technologies develop further and new RPA applications continue to emerge. RPA operators should expect data loss events and prepare for these appropriately.
The ATSB SafetyWatch highlights the broad safety concerns that come out of our investigation findings and from the occurrence data reported to us by industry. One of the safety concerns relates to data input errors.
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 (TSI 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 TSI Act requires the ATSB to publish a statement setting out the reasons for discontinuing an investigation.
At about 1000 Western Standard Time on 10 September 2016, an Air Tractor AT-502 aircraft, registered VH‑ULV, was conducting aerial agricultural spraying activities at Salmon Gums, near Esperance, West Australia. During a turn at about 200 ft above the ground, the pilot lost control and the aircraft collided with terrain. The aircraft was substantially damaged and the pilot sustained serious injuries.
Figure 1: VH-ULV showing damage Source: Operator
Preliminary enquiries by the ATSB suggest that the accident was attributable to pilot actions. The ATSB considered it was very unlikely that further investigation would uncover any systemic safety issues. The ATSB has discontinued the investigation.
Section 21 (2) of the Transport Safety Investigation Act 2003 (TSI 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 TSI Act requires the ATSB to publish a statement setting out the reasons for discontinuing an investigation.
At about 1000 Western Standard Time on 10 September 2016, an Air Tractor AT-502 aircraft, registered VH‑ULV, was conducting aerial agricultural spraying activities at Salmon Gums, near Esperance, West Australia. During a turn at about 200 ft above the ground, the pilot lost control and the aircraft collided with terrain. The aircraft was substantially damaged and the pilot sustained serious injuries.
Figure 1: VH-ULV showing damage Source: Operator
Preliminary enquiries by the ATSB suggest that the accident was attributable to pilot actions. The ATSB considered it was very unlikely that further investigation would uncover any systemic safety issues. The ATSB has discontinued the investigation.
On 5 June 2016, the pilot of a Cessna 206 floatplane, registered VH-NTK, was taking off from the Southport Broadwater about 6 km south-east (SE) of Southport Airport, Queensland, for a charter flight with two passengers on board.
The wind was blowing from the west-north-west (WNW) at about 18 kt, with gusts of variable speed. The take-off direction to the north-west (NW) was too restrictive due to the presence of boats in the area, so the pilot elected to begin the take-off towards the south-west (SW) (Figure 1). Taking off to the SW would be through a jet-ski course and a crosswind from the right. Once clear of the jet-ski course, the pilot intended to veer right onto a more westerly (into wind) heading to complete the take-off.
The pilot set 20° flap and left the water rudders[1] in the down position to assist with directional control at the start of the take-off run. The pilot applied full power to start the take-off run and the aircraft pitched[2] backwards into the plowing position.[3] The pilot retracted the water rudders about five seconds into the take-off run, and about two seconds later, pitched the aircraft forward from the plowing position into the step position.[4] As the aircraft pitched forward onto the step it veered to the left onto a south-south-west (SSW) heading (this increased the crosswind experienced – see textbox 4 in Figure 1). The pilot maintained the aircraft on this heading until they sighted barrels in the water that were used to mark the jet-ski course.
The pilot could not prevent the veer to the left, even with full right rudder, so after sighting the jet-ski course barrels, the pilot pitched the aircraft backwards into the plowing position to improve directional control on the water.[5] The pilot then alternated pitching the aircraft between the plow and step position in order to gradually veer to the right onto a more westerly heading (textbox 5 in Figure 1).
As the aircraft was passing a SW heading and was turning towards WSW, the right wing lifted and the aircraft rolled[6] to the left. The roll continued, despite the application of full right aileron by the pilot, until the left wing impacted the water. The aircraft rotated to the left through about 270° and the nose and propeller ploughed into the water. The aircraft then came to a stop in an upright position, facing in a westerly direction (Figure 1).
The pilot assessed the condition of the aircraft and elected not to evacuate the passengers. The aircraft was then towed to shore by a jet-ski. There were no injuries and the aircraft was substantially damaged (Figure 2 and 3).
Figure 1: Approximate take-off path and key events
Source: Google earth modified by ATSB
Figure 2: VH-NTK left wing damage
Source: Owner
Figure 3: VH-NTK rear strut fracture (view of the left float facing forwards)
Source: Owner
Pilot comments
The pilot provided the following comments:
the force that veered the aircraft to the left occurred when they pitched the aircraft forward from the plow position to the step position
they were turning the aircraft right through SW towards WSW when it rolled
they were holding full into wind (right) aileron control and therefore expected the left wing to lift prior to the right wing
when they rolled to the left they were ‘shocked’ by the crosswind and ‘surprised’ they could not control the floatplane
they estimated the strength of the gust that lifted the right wing was about 8–10 kt
they had about 110 litres of fuel in the left wing tank and about 60 litres in the right wing tank, which may have contributed to the left roll
the floatplane rolled left at about 30–35 kt airspeed
the crosswind limit is 20 kt
the take-off speed is 41 kt with 20° flap set.
Left turn effect
There are four distinct propeller forces, each of which produce a left turning force on an aeroplane, as follows:
Torque effect: As the engine internal parts and propeller rotate clockwise, as viewed by the pilot, an equal force tries to rotate the aircraft in the opposite direction. This force places more weight and consequently more hydrodynamic drag on the left float of a floatplane.
Slipstream effect: The clockwise spiralling motion of the propeller slipstream means that the slipstream strikes the left side of the vertical fin. This produces a yawing[7] moment to the left.
P-factor: In a nose high attitude the ‘bite of air’ of the downward moving blade of the propeller is greater than the ‘bite’ of the upward moving blade, which moves the centre of thrust to the right side of the propeller disc. This also produces a yawing moment to the left.
Gyroscopic effect: The rotating propeller behaves like a gyroscope. As such, any time a force is applied to deflect the propeller from its plane of rotation, the resultant force is 90° ahead in the direction of rotation, and in the direction of the effective force (Figure 4). As such, the gyroscopic effect results in a yawing motion to the left when the aircraft is pitched forward from the plow position to the step position.
Figure 4: Gyroscopic effect
Source: FAA pilot’s handbook of aeronautical knowledge
According to the FAA Seaplane operations handbook, crosswinds can present special difficulties for floatplane pilots. If the aircraft turns towards the wind during a crosswind take-off, then centrifugal force will combine with the wind force to produce a rolling moment in the opposite direction to the turn (Figure 5). If strong enough, the combination of wind and centrifugal force may lift the upwind wing and submerge the downwind float, rolling the aircraft until the downwind wingtip strikes the water. This is known as a water‑loop (Figure 6).
Centre of gravity[8] location also affects the floatplane’s handling characteristics on the water. If the centre of gravity is located to one side of the centre-line, such as a fuel imbalance between the tanks, one float must support more weight and therefore displace more water than the other float, resulting in more water drag on that side (Figure 7).
Figure 5: Effect of wind force and centrifugal force
Source: FAA seaplane operations handbook
Figure 6: Water-loop
Source: FAA seaplane operations handbook
Figure 7: Effect of fuel imbalance on centre of gravity
Source: FAA seaplane operations handbook
ATSB comment
The pilot reported that it was the force from the forward pitching motion of the aircraft from the nose-high plowing position to a nose-level step position that resulted in the aircraft veering left from the planned take-off path. The force that produces this motion is the gyroscopic effect. At the time of the uncommanded roll to the left the aircraft was turning right with a strong crosswind from the right and more fuel distributed in the left tank than in the right tank. These factors probably combined to elevate the risk of submerging the downwind float and lifting the upwind wing, resulting in a water-loop.
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.
Operator
As a result of this occurrence, the aircraft operator has advised the ATSB that they are taking the following safety actions:
Changes to operating procedures
The operator is updating their operations manual to incorporate the following procedural changes:
The channel at the operating base is orientated north-south, which restricts movements orientated east-west, therefore if the wind is forecast to gust more than 20 kt from the west, or within 30° either side of west, the take-off must be rejected.
If the aircraft veers to the left during the take-off run and requires full control inputs, then reject the take-off.
Safety message
This accident highlights the risk of a water-loop event during a crosswind take-off in a floatplane. The combined forces acting on a floatplane have the potential to significantly reduce the margin of control available to the pilot. The FAA Seaplane operations handbook provides several recommended crosswind take-off techniques, including the considerations associated with arcing manoeuvres during take-off. If an arcing manoeuvre is to be attempted then the FAA handbook recommends placing the centrifugal force and wind force on opposite sides, and reducing the radius of the arc as the floatplane speed increases.
Refer to the FAA Seaplane operations handbook for a detailed explanation of the recommended crosswind take-off techniques.
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 May 2016, the pilot of a Maule MT-7-235 aircraft, registered VH-DRS, conducted a private flight from Greenfields airstrip (near Noosa), Queensland, with two passengers on board.
The aircraft departed Greenfields airstrip at about 1220 Eastern Standard Time (EST) and flew to Gympie ALA, where the aircraft was refuelled. The aircraft then departed from Gympie and flew north towards Maryborough before returning to Greenfields along a coastal route.
The aircraft joined the circuit at Greenfields on the downwind leg for runway 09. The pilot turned on to the final approach at about 800 ft above ground level, with an airspeed of about 70 kt. The pilot noticed they were getting low on the approach and at about 500 ft, they increased the power to regain their approach path. The pilot subsequently assessed that the aircraft was too high and lowered the nose to re-intercept the approach path.
The pilot flared the aircraft for landing, the aircraft landed heavily and bounced into the air. As the aircraft landed again, the nose wheel touched down first (before the main landing gear) with sufficient force that the nose wheel strut fractured. The nose landing gear and propeller then dug into the ground and the aircraft rotated over its nose and slid a short distance inverted before coming to rest.
The pilot and one passenger were uninjured, the other passenger sustained minor injuries, and the aircraft sustained substantial damage (Figure 1).
Figure 1: Accident site showing damage to VH-DRS
Source: Aircraft owner
Pilot comments
The pilot provided the following comments:
they taxied the full length of the strip before departure from Greenfields and noted the grass surface was in good condition
they had flown about five flights, totalling about 20 hours in the last 12 months
the pilot’s previous flight was about 4 to 5 weeks prior to the accident flight
the pilot had not operated the Maule aircraft with more than one passenger on board prior to the accident flight
the pilot thought that the higher all-up-weight of the aircraft with an extra passenger on board contributed to a higher sink rate on final than they expected
the pilot commented that they should have performed a go-around, rather than continuing with the landing manoeuvre.
ATSB comment
Currency versus proficiency
At the time of the accident the pilot was current for passenger-carrying operations, having conducted at least three take-offs and three landings in the last 90 days. However, it was more than one month since their last flight, which was also a local area scenic flight. The take-off and landing phases of flight are critical phases of flight, since the aircraft is operating closer to the stall speed and with less height to recover from a control problem, relative to cruise flight. The requirement for three take-offs and three landings in the last 90 days is a regulatory requirement of currency, but this does not guarantee proficiency. When flying infrequently, proficiency in take-offs and landings can be improved by dedicating a portion of the flight to practicing circuits. The United States Federal Aviation Administration safety briefing September/October 2010 described this as ‘imbuing the quantity of all your flying, however limited, with quality.’
Safety message
Go-around
The pilot commented that conducting a go-around could have prevented an unstable approach and initial bounce from escalating to an accident. General aviation pilots should set their own criteria for when to conduct a go-around manoeuvre, so that they can recognise and respond to the conditions in a timely manner. This will assist pilots to develop a mindset, which the Flight Safety Foundation (FSF) refers to as ‘go-around-prepared’. FSF Approach-and-landing Accident Reduction (ALAR) briefing note 6.1 emphasises the need to be ‘go-around-prepared’ or ‘go-around-minded’ because the execution of a go-around is an infrequent manoeuvre. FSF ALAR briefing note 7.1 provides further information on unstable approaches and how to develop personal lines of defence.
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.
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On the morning of 29 January 2016, a Piper Aircraft Corp PA-28 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 at 1227 Eastern Daylight-saving time, 6.6 km south-west of Point Lonsdale. All four occupants of the aircraft were fatally injured.
What the ATSB found
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.
Safety message
Pre-flight planning needs to include consideration of not only the conditions on departure, but at all stages of the flight. This informs the decision of whether to depart and allows for prior consideration of alternative actions in the case of deteriorating weather, such as returning or diverting.
It is always possible that the actual weather conditions will be different to those forecast. Pilots conducting a flight under the visual flight rules make every effort to avoid areas of low visibility and plan for unforeseen eventualities. However, this is dependent on the pilot perceiving the risks of the situation, which is not inherently easy. Education and training in the practical application of meteorological principles has been shown to enhance pilots’ ability to recognise and respond to deteriorating weather conditions.
The ATSB cautions that, on entering an area of reduced visual cues, the risk of experiencing spatial disorientation and a loss of control is high, measuring from between 60 to 178 seconds from the time of entering the area of low visibility. This risk is highest for those without proficiency or recent experience in instrument flying. Requesting assistance from air traffic control can increase the chances of re-establishing visual cues.
Safety analysis
While en route from Moorabbin, Victoria to King Island, Tasmania, Piper Aircraft Corp. PA‑28 aircraft, registered VH-PXD (PXD), entered an area of low visibility around Point Lonsdale. The aircraft’s track became increasingly erratic until its impact with the water. There were no significant defects or anomalies found with the recovered components of the aircraft that might have contributed to the accident.
Of the three aircraft occupants that held a pilot licence, the ATSB was not able to establish the pilot in command for the flight. None of these occupants held an instrument rating and the flight was being carried out under the Visual Flight Rules (VFR).
The following analysis examines the decision to depart on the flight and the various human performance factors that likely influenced a VFR pilot, who did not hold an instrument rating, to continue the VFR flight with reduced visual cues. The effect on human performance of spatial disorientation is also examined.
Decision to depart Moorabbin Airport
Prior to departing Moorabbin, the occupants on board PXD had retrieved a number of aerodrome and area forecasts, weather observations and notices to airmen for the day. During their pre-flight preparations, the two early arrival occupants formed a view that the weather conditions at Moorabbin Airport would improve and suggested the last two occupants make their way to the airport.
The weather observations either side of PXD’s departure suggested scattered to broken cloud with a base of between 1,000 and 1,200 ft and a visibility of 10 km or more. The lower of those cloud bases, and content of the earlier Automatic Terminal Information Service ‘Papa’, would explain the use by a number of pilots of previous arrivals/departures to/from Moorabbin of special VFR.
The lack of evidence of the pilot of PXD accessing information ‘Papa’, or later information, could suggest that the pilot did not have that information on taxi. There was also no evidence of the pilot being on Moorabbin Tower frequency until about 1144, after the time the last of the preceding aircraft movements sought clearance under the special VFR. In this case, the pilot of PXD would not have developed an understanding of the implications of the content of information ‘Papa’ or the subsequent information, or of the earlier pilots’ clearance requests for departure from/entry to the Moorabbin control zone under special VFR. In the absence of that understanding, the successful arrival/departure of those aircraft could have contributed the decision by the pilot of PXD to depart Moorabbin.
ATSB analysis of the area forecasts relevant to the flight identified a complex weather system with showers tending to rain, low cloud with a minimum base of 500 ft and isolated thunderstorms over the sea, coast and adjacent areas. These conditions could be expected on the planned route to King Island. Although several sources of weather forecast information were accessed, the ATSB could not determine the extent to which the occupants of PXD considered these forecasts and the associated risk to their flight once they departed Moorabbin. In addition, the recorded weather conditions around the time of PXD’s departure from Moorabbin indicated minimal cloud cover en route to the Point Lonsdale area.
In the event, other pilots also departed Moorabbin for King Island. Of these, a preceding pilot returned to Moorabbin in response to the reduced visibility in the area of Point Lonsdale. The pilot of the returning aircraft indicated that the reduced visibility was due to what appeared to be storms. Two following pilots continued to King Island, although also reported reduced visibility conditions in the Point Lonsdale area.
The importance of careful study of all relevant weather and other operational information affecting a flight was highlighted in the ATSB Avoidable Accident Series booklet Accidents involving pilots in Instrument Meteorological Conditions. The benefits of thorough pre‑flight planning in minimising in-flight decision errors were highlighted as follows:
Prior to a flight, a pilot must study all available information appropriate to the intended operation, including the current weather forecasts. This is a requirement in the Civil Aviation Regulations (CAR 174) and [is] repeated in the Aeronautical Information Publication…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 following section examines the decision by the pilot of PXD to apparently continue the flight to King Island in the deteriorating weather conditions.
Flying into areas of low visibility
The United States National Transportation Safety Board (2005) found that ‘reduced-visibility weather represents a particularly high risk to [general aviation] operations’ and that ‘weather may…test the limits of pilot knowledge, training, and skill to the point that underlying issues are identified.’
After ascertaining that it was suitable to depart Moorabbin, the occupants of PXD encountered conditions over eastern Port Phillip Bay that allowed for flight to a recorded altitude of 1,400 ft. This may have strengthened a perception that continuing on their planned track past Point Lonsdale towards King Island was possible.
In contrast, closed-circuit television footage, witness statements and photographs taken by other pilots indicated localised precipitation and low cloud and low visibility conditions in the Point Lonsdale area. These conditions were consistent with the area forecast and would have affected PXD. Although audible, PXD was not visible to witnesses in the reported low cloud and visibility until it descended through, or appeared from behind the cloud and impacted the water.
Wiegmann and Goh (2000) explained that:
One reason why pilots may decide to continue a VFR flight into adverse weather is that they make errors when assessing the situation. That is, pilots are seen to engage in VFR flight into IMC [instrument meteorological conditions] because they do not accurately assess the hazard (i.e., the deteriorating weather conditions)…
The previously mentioned United States National Transportation Safety Board report (2005) added that in these cases, pilots who might appear to intentionally engage in risky behaviour may actually be making choices that they mistakenly believe to be safe:
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.
This would explain the pilot’s assessment of the risk associated with the low visibility conditions in the Point Lonsdale area and subsequent decision to continue towards these conditions, rather than to divert. Wiggins and O’Hare (1995) further explained how errors in assessment can take place, acknowledging that weather-related decision making can be highly complex and therefore more prone to errors:
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.
ATSB Aviation Research and Analysis Report B2007/0063 stated that pilots should not attempt to fly into instrument meteorological conditions under the VFR. Pilots should develop a plan prior to take-off on what to do if the weather en route is different from that expected, or deteriorates. This plan should consider a requirement to divert or turn back prior to entering instrument meteorological conditions. However, this depends on a pilot correctly assessing the weather conditions. The United States National Transportation Safety Board (2005) noted that targeted weather-related training programs have had some success in teaching pilots to recognise and respond to deteriorating weather conditions.
Additionally, Wiggins and O’Hare (2003) evaluated the effectiveness of a cue-based training system called Weatherwise, 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. The Weatherwise program was made available to pilots by the Civil Aviation Safety Authority (CASA). Additionally, CASA produced a Weather to Fly education program which focuses on topics such as the importance of pre-flight preparation, making decisions early and talking to ATC.
It was not known how the occupants understood the weather conditions ahead of them prior to entering an area of low visibility conditions. The occupants of PXD may have misperceived the severity of the conditions, resulting in them tracking into the area. In this case, the inherent challenges of assessing low visibility conditions in-flight likely influenced the pilot’s continuing towards an area of reduced visual cues, particularly when the pilots had limited instrument flying proficiency. This reinforces the benefits of comprehensive pre-flight planning to minimise the risk of in‑flight decision errors.
Spatial disorientation resulting from a loss of visual cues
PXD entered an area that was reported by witnesses to include low visibility at about 1223, just after passing Point Lonsdale. The pilot had already executed a number of left and right turns approaching this area, conceivably as they sought to avoid cloud or move towards areas of improved visibility. The decision to then undertake a 180° turn was likely an effort to track back over Point Lonsdale and avoid or exit the low visibility conditions.
On entry into the low visibility conditions, the pilot of PXD would have lost visual cues, in particular the horizon. It is well established that a loss of visual cues significantly increases the risk of spatial disorientation.
Along with the loss of visual cues, there was the potential that the 180° turn contributed to the development, or exacerbated the effects of spatial disorientation. Subsequently the aircraft tracked south over the water, initially in a right turn, with a series of climbs and descents varying in height between 500 ft and 1,200 ft. The final right turn was accompanied by a high rate of descent from 1,200 ft, followed by impact with the water.
The time from PXD entering the area of low visibility to impacting the water was about 180 seconds. This is broadly consistent with the time indicated by research between experiencing spatial disorientation and a subsequent loss of control. Reinforcing the high likelihood that, in the conditions, the pilot of PXD experienced spatial disorientation the:
pilot did not hold an instrument rating
aircraft’s track and height was erratic once it entered the area of low visibility
aircraft was seen to exit or appear from behind cloud in conditions of low visibility, reducing the available visual cues and likelihood of a reliable horizon.
The conditions that confronted the pilot of PXD are not alone in contributing to the development of spatial disorientation. All pilots are at risk given certain conditions. The ATSB publication Avoidable Accidents No. 4 – Accidents involving Visual Flight Rules pilots in Instrument Meteorological Conditions outlined that ‘disorientation can affect any pilot, no matter what their level of experience.’
As indicated previously (see the section titled Related occurrences), a pilot’s chances of avoiding and/or exiting disorienting conditions increase if they request the assistance of air traffic control. However, in reality the difficulties of identifying the risk faced in conditions of decreased visual cues, combined with what will likely be increased workload and stress, can often preclude a pilot considering this as an option. It is well-established that the likelihood of a loss of control when experiencing spatial disorientation remains very high.
The ATSB found that due to the presence of low cloud, rain and reduced visibility, the pilot of PXD likely experienced a loss of visual cues and became spatially disorientated, leading to a loss of control and impact with the water.
The occurrence
On the morning of 29 January 2016, a Piper Aircraft Corp. PA-28 aircraft, registered VH-PXD (PXD), was on a private flight under the visual flight rules (VFR)[1] from Moorabbin Airport, Victoria to King Island, Tasmania with four occupants on board. The ATSB was unable, given the physical evidence and available flight documentation, to establish which occupant was the pilot in command of the flight.
Several members of the Royal Victorian Aero Club (RVAC) were planning to fly to King Island throughout the weekend, although there was no coordination between the members.
Two of the occupants of PXD arrived at Moorabbin Airport by about 0800 Eastern Daylight‑saving Time[2] that day and ascertained that the weather in the vicinity of the airport was not yet suitable for departure. However, other pilots reported advising the occupants of PXD that the weather at King Island was good. It was also reported that one of the occupants formed the understanding that the weather was slowly moving east and that it was clearing to the west. At around 1000, the early arrivals contacted the other occupants of PXD. It was reported that the decision to go was made during that exchange. By 1100, all four occupants were at the airport and preparing for the flight.
At some stage during the morning, one of the occupants logged into their National Aeronautical Information Processing System account[3] and accessed a number of weather and aerodrome forecasts, weather observations and notices to airmen (NOTAM)[4] for the day. This same occupant also called the local Bureau of Meteorology phone number. Two of the occupants also made phone calls to the recorded Aerodrome Weather Information Services[5] for King Island (the evening before) and Moorabbin (that morning). Those products and services were broadly consistent with the intended route.
Recorded radio calls indicated that, as PXD was being prepared to depart, a number of other aircraft requested clearance for their arrivals/departures at Moorabbin under special VFR (refer to the section titled Additional information – Visual flight rules and visual meteorological conditions). This was due to a reported cloud base of 800 ft. The requests for special VFR were made by a pilot departing at 1138 and a pilot arriving into Moorabbin at 1213.
At 1144:32, a transmission was made by the pilot of PXD on the Moorabbin Ground frequency that the aircraft was positioned in the engine run-up bay and that they were ready for departure for King Island. At 1157:55, the pilot of PXD advised the Moorabbin Tower controller that they were at the holding point for runway 13L and ready for take-off. This call did not include a request for special VFR and ATC did not prompt the request. Three minutes later they received clearance for take-off before departing Moorabbin at 1203. The aircraft’s track to Point Lonsdale and a number of pilot actions and other observations are at Figure 1.
Around the same time, one of the RVAC aircraft flying to King Island was nearing Point Lonsdale. The pilot of that aircraft later reported having seen what appeared to be a storm cell over Point Lonsdale and the heads. The likelihood of reduced visibility in the area was reported to have prompted the pilot to return to Moorabbin Airport. The pilot of the RVAC aircraft landed back in Moorabbin at 1220 with a special VFR clearance. This was after PXD’s departure.
A transmission was made by the pilot of PXD on the Moorabbin Tower frequency at 1209. In this transmission, the pilot reported that the cloud base over Carrum was about 800–900 ft. No further radio contact with PXD was recorded. At 1212 the aircraft’s transponder code was switched to ‘1200’ per normal airspace procedures.[6]
At about 1222, after passing over Point Lonsdale, the pilot conducted a series of left and right turns, followed by a 180° turn to initially track back towards Point Lonsdale. This was followed by a gentle right turn heading south over the ocean for about 2 minutes, before again turning right and entering a rapid descent. At about 1227, PXD impacted the water 6.6 km south-west of Point Lonsdale. All of the aircraft occupants were fatally injured.
Witnesses who were fishing in the vicinity of Point Lonsdale at the time reported hearing an aircraft pass nearby at what they interpreted to be a ‘very low altitude’. Due to the low cloud and visibility in the area they could not initially see the aircraft. The witnesses recalled that, a few minutes later, they saw the aircraft just before it impacted the water. It appeared to be in a nose‑down, right wing-low attitude and the engine sounded as though it was producing power.
Another two aircraft that were also from the RVAC departed Moorabbin for King Island at 1230 and 1250 respectively. Whilst communicating with each other on the RVAC frequency, they discussed the area of low visibility around Point Lonsdale. Both pilots reported descending in the vicinity of Point Lonsdale in an effort to maintain better visibility, particularly over Barwon Heads. One pilot took several photographs whilst flying over the area that show the weather conditions. Showers were reported passing through this area, reducing the cloud base. The two aircraft continued on to King Island.
Figure 1: PXD’s track from Moorabbin Airport until the collision with water near Point Lonsdale with the area between Point Lonsdale and the impact with the water at inset. Noteworthy pilot actions and other observations are annotated.
Benson, AJ 1999, ‘Spatial disorientation – general aspects’, in J Ernsting, AN Nicholson & DJ Rainford (Eds.), Operational Aviation Medicine (3rd ed.), Oxford, England, Butterworth Heinemann, pp. 419-436.
Gawron, V 2004, ‘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.
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.
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 ofHuman 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: Applied Vol. 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 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.
Submissions were received from the Civil Aviation Safety Authority. The submissions were received and where considered appropriate, the text of report was amended accordingly.
Findings
From the evidence available, the following findings are made with respect to the collision with water involving a Piper Aircraft Corp PA-28-235, registered VH‑PXD, 33 km south-south-east of Avalon Airport, Victoria on 29 January 2016. These findings should not be read as apportioning blame or liability to any particular organisation or individual.
Contributing factors
Continuation of the flight towards an area of low cloud and rain was likely influenced by the inherent challenges of assessing low visibility conditions, particularly without instrument flying proficiency.
Upon entering an area of low cloud, rain and reduced visibility, the pilot likely experienced a loss of visual cues and became spatially disorientated, leading to a loss of control and impact with the water.
Other findings
During their pre-flight preparations, the occupants' understanding of improving weather conditions at Moorabbin Airport, potentially reinforced by with the successful departure/arrival of other aircraft at the airport, contributed to their decision to depart.
Context
Personnel information
Of the four occupants on board PXD, three were pilots. Of these, two held the necessary qualifications and a current medical to be able to conduct the flight. None of the pilots had ever held an instrument rating. However, there was insufficient evidence to definitively identify the pilot in command for this flight.
Fatigue
An assessment was undertaken of whether any of the aircraft occupants may have been experiencing a level of fatigue known to have an effect on performance. This included consideration of their possible time awake at the time of the occurrence, sleep history and potential workload associated with the task and environmental factors. However, the limited data available on the occupants’ activities in the preceding days meant there was insufficient evidence to determine whether fatigue was contributory to this occurrence.
Aircraft information
General
VH-PXD (PXD) was a Piper Aircraft Corp. PA-28 four seat, low wing, all metal, unpressurised, fixed undercarriage aircraft with a single reciprocating engine (Figure 2). It had current certificates of airworthiness and registration and a current maintenance release, with no noted defects.
The last periodic maintenance inspection on PXD was conducted in Bacchus Marsh on the day before the occurrence. During that inspection, the right-upper wing skin was replaced, the artificial horizon was repaired and all of the aircraft’s control cables were replaced. The maintenance was completed by an appropriately-qualified Licensed Aircraft Maintenance Engineer in an approved maintenance facility.
The 25-minute return flight to Moorabbin after the maintenance at Bacchus Marsh was completed with no reported issues.
Figure 2: VH-PXD, taken in April 2011 in Echuca, New South Wales
The ATSB was unable to determine the actual weights and seating positions of the occupants and amount of baggage on board at the time of the occurrence. Therefore, the actual weight of the aircraft and its centre of gravity was unable to be calculated.
It was reported that the aircraft was refuelled to full tanks prior to departing Moorabbin Airport that day. The weight of the aircraft on departure from Moorabbin Airport was estimated based on:
the recorded aircraft weight
the weight of the fuel
data from the Civil Aviation Safety Authority (CASA) medical examinations for three of the aircraft occupants[7]
a statistical average for the fourth occupant.
That estimate would have meant PXD was about 35 kg under the maximum permissible take-off weight for the flight. However, that weight did not account for the unknown amount of baggage on board. It was therefore concluded likely that the aircraft was close to its maximum take-off weight when it departed from Moorabbin Airport.
Meteorological information
Forecast weather
On the day of the occurrence, there was a complex weather pattern over south-eastern Australia. That weather pattern included a number of low pressure systems, along with upper atmosphere and surface troughs. This was forecast to result in significant areas of low cloud, showers and areas of rain.
An area forecast (ARFOR)[8] covering the proposed route indicated a surface trough to the east of Melbourne that was forecast to slowly move to the west during the day. There were isolated thunderstorms forecast over the sea, coast and adjacent ranges to the east of Melbourne. Showers of rain, with associated broken[9] low cloud with a minimum base of 500 ft were forecast in an area starting west of Melbourne and extending to the east. Additionally, there was forecast low cloud south-east of a line extending from King Island, north to Ballarat and then east to Bombala. A pictorial representation of these areas is shown at Figure 3.
Figure 3: Pictorial representation of the Area 30/32 forecast valid from 0900 on 29 January 2016
Source: ATSB
The aerodrome forecast (TAF)[10] for Moorabbin Airport that was issued at 1003 indicated that the wind would be from the south-east at 8 kt and that the visibility would generally be greater than 10 km. Light rain was forecast with a scattered cloud base at 1,200 ft above the aerodrome and a broken layer at 3,500 ft. The forecast noted that there would also be periods of up to 60 minutes duration, starting from 1100, where the visibility would decrease to 4,000 m in rain and the cloud base would lower to 1,000 ft and the amount of cloud increase to broken.
A TAF for Avalon Airport indicated that the wind would be variable in direction at 5 kt and that the visibility would generally be greater than 10 km. Light showers of rain were forecast and the cloud was forecast to be scattered with a base 1,000 ft above the aerodrome and a broken layer at 3,500 ft. The forecast indicated that, from 0800, there would be periods of 30 minutes duration where the visibility would decrease to 5,000 m in showers of rain, and the cloud base would be scattered at 1,500 ft.
Actual weather conditions
Weather reports (captured by automatic sensors) for Moorabbin between 1100 and 1200 indicated a scattered layer of cloud with a base between 800 and 1,200 ft above the aerodrome elevation and a visibility of 10 km or more. A special report (SPECI)[11] issued at 1209 indicated that the cloud base was broken at 1,200 ft. None of the weather reports suggested that decreased visibility might have affected PXD’s departure.
A weather report issued at 1130 for Avalon indicated the visibility had reduced to 9,000 m in drizzle with cloud overcast at 2,700 ft. A SPECI at 1133 reported a further decrease in visibility to 6,000 m with cloud unchanged. The 1200 SPECI for Avalon indicated scattered cloud but with a lower base of 1,100 ft, and that the visibility had increased to in excess of 10 km.
Weather radar images from the Melbourne (Laverton) radar recorded the following:
At 1218, significant rainfall returns, from light to moderately heavy rain to the east of Melbourne, extending from the ranges to Bass Strait. There were also rainfall returns to the south-west of the radar location over land, the coastline and extending out to sea in the area of Barwon Heads. These indicated light rainfall, with the heaviest returns over the sea to the east of Anglesea.
At 1224, that the rainfall returns to the south-west had increased in area and intensity. The returns were generally orientated along a line in a north‑westerly to south‑easterly direction. That line covered an area estimated from 5 km inland to a point estimated to be 20 km out to sea. A portion of this image is shown in Figure 4, with the aircraft’s track superimposed.
At 1307, that the area of rain enlarged, extending from Torquay to Anglesea and out to sea.
The weather radar information from 1224, when overlayed with the aircraft track, indicated that the aircraft likely entered an area of low visibility associated with light‑to‑moderate rain at about 1223.
Moorabbin Automatic Terminal Information Service
Relevant aspects of the Moorabbin Automatic Terminal Information Service (ATIS) reports of the actual conditions and requirements at around the time of the flight by PXD are listed in Table 1.[12] When operating at a controlled aerodrome where an ATIS is in operation, pilots are required to listen to the facility prior to taxi and advise air traffic control of receipt of that information. This advice is part of the pilot’s taxi call.
Table 1: Actual weather conditions and requirements as reported in successive ATIS reports at around the time of the flight by PXD
Condition/requirement
ATIS and time issued
‘Papa’ of 1137
‘Quebec’ of 1152
‘Romeo’ of 1215
Approach type
Expect instrument approach
Expect instrument approach
Expect instrument approach
Visibility
Reduced to 6 km
Reduced to 6 km
Greater than 10 km
Weather
Showers in the area
Showers in the area
Nil reported
Cloud
Broken at 600 ft
Scattered at 800 ft and broken at 1,500 ft
Scattered at 800 ft and broken at 1,500 ft
The pilot of PXD made their taxi call at 1144:32. Although ATIS is a passive facility, there was no indication in the recorded radio calls that the pilot of PXD accessed ATIS information ‘Papa’.
Figure 4: Weather radar recording (orientated with reference to a Google earth map at inset) and associated ‘Rain rate’ at 1224, showing the aircraft’s track
Source: At inset, Google earth, modified by the ATSB and larger image Geoscience Australia (base map) and the Bureau of Meteorology (weather radar), both modified by the ATSB
Closed-circuit television images from Port of Melbourne cameras facing east across the water from Point Lonsdale, and north from Point Nepean both showed drizzle, light rain and reduced visibility including little natural horizon as PXD tracked south along the eastern shore of Port Phillip Bay (Figure 5).
Witnesses that saw the aircraft recalled that the visibility at that time was very low, such that it prevented them seeing the land. The witnesses estimated that the land was between 1 and 4 km away and indicated that it was raining at the time.
Figure 5: Still images taken at 1215 from two different closed-circuit television cameras owned by the Port of Melbourne. One camera (left image) was positioned on the Point Lonsdale lighthouse facing east. The other camera (right image) was positioned at Point Nepean, facing north. The image quality is affected by contaminants on the camera lens, but the extent of the low visibility conditions in the area is evident
Source: Port of Melbourne, modified by the ATSB
Recorded data
Recorded flight data was obtained from an ‘electronic flight bag’ iPad™ application that the occupants were using on the flight. This data was used to assist in the wreckage recovery and in the analysis of the aircraft track.
Flight track information was also obtained from air traffic control (ATC) radar information. This included recorded radar returns from the aircraft from its departure from Moorabbin Airport to the time of the occurrence.
Witnesses that saw the occurrence also provided the ATSB with their ‘fish finder’ Global Positioning System device. Data was downloaded from this device and assisted with locating the wreckage.
Wreckage and impact information
The aircraft impacted the water after a rapid descent, with parts of the wreckage descending to the sea floor. Evidence from the wreckage was consistent with the aircraft impacting the water in a nose-down attitude, with the engine delivering power.
Recovery of the wreckage
A search for the wreckage was commenced by the Victoria Water Police and Air Wing within an hour of the accident. Small items of wreckage had surfaced, or remained on the surface and were recovered by the water police and nearby witnesses. These included items such as a number of the occupants’ personal effects and the three pilots’ CASA flight crew licences and aviation medical certificates.
After several day’s search using surface sonar and underwater robotic equipment, on 2 February 2016 Victoria Police located a large portion of the aircraft wreckage on the ocean floor at a depth of 34 m. The wreckage was about 1 km from shore, off the Point Lonsdale lighthouse.
On the evening of 6 February 2016, the wreckage was recovered to the surface by police divers, supported by a barge and lifting equipment (Figure 6). On 7 February, the ATSB assisted with the removal and transportation of the wreckage to a secure site for inspection.
Figure 6: Recovery by Victoria Police of the aircraft’s fin and left horizontal stabiliser
Source: Victoria Police
Wreckage inspection
The majority of the aircraft’s fuselage, fin, horizontal stabiliser, engine and propeller, flight control cables, main landing gear assembly, instrument panel and some items from the cabin interior were recovered. Figures 7 and 8 show some of the airframe and other items and components that were recovered.
All identified fracture surfaces throughout the recovered wreckage were consistent with overload failure as a result of the impact with water. There was no evidence of pre-existing damage to the airframe, or failure of the primary control systems that may have contributed to the accident. However, the aircraft wreckage exhibited severe disruption.
Some components, such as the engine carburettor, right horizontal stabiliser assembly and left and right-wing structures were not recovered.
Figure 7: Some of the recovered aircraft wreckage. Note the extent of the disruption of the airframe
Source: ATSB
A detailed inspection of the engine and propeller was conducted in a CASA-approved maintenance facility. Nothing was identified during that inspection that may have contributed to the accident, or would have prevented the engine and propeller from normal operation.
Figure 8: Recovered aircraft engine, propeller and propeller spinner, looking at the lower surface of the engine
Source: ATSB
Medical and pathological information
Post-mortem and toxicological examination of all of the aircraft occupants found no underlying medical disorder likely to lead to incapacitation. All occupants on board PXD sustained multiple fatal injuries consistent with the aircraft impacting water.
Survival aspects
Due to the extent of the impact forces and aircraft break-up, the occurrence was not survivable. While the occupants of PXD were seen by witnesses to acquire life jackets prior to their departure from Moorabbin Airport, these were not found in the recovered wreckage.
Additional information
Visual Flight Rules and Visual Meteorological Conditions
The CASA Visual Flight Rules Guide outlined that flight under the visual flight rules (VFR) can only be conducted in Visual Meteorological Conditions (VMC).[13] This was provided that, when operating at or below 2,000 ft above the ground or water, the pilot is able to navigate by visual reference to the ground or water.
Moorabbin Airport was surrounded by Class D (controlled) airspace out to 3 NM (6 km) and below 2,500 ft above mean sea level. The visual meteorological conditions for class D airspace included:
a flight visibility of 5,000 m
a minimum horizontal distance from cloud of 600 m and height vertically above cloud of 1,000 ft or vertically below cloud of 500 ft.
When requested by a pilot, ATC could permit operations by day in Class D airspace under special VFR when the weather conditions did not meet the above VMC criteria. Operations under special VFR required pilots to:
remain clear of cloud
in the case of aeroplanes, ensure an in-flight visibility of 1,600 m
operate within the requirements of Civil Aviation Regulation 157 Low flying.
After departing class D airspace, the aircraft entered (uncontrolled) Class G airspace. The following conditions were stipulated for flight under the VFR in this airspace when below 10,000 ft:
a flight visibility of 5,000 m
a minimum vertical distance of 1,000 ft and horizontal distance of 1,500 m from cloud.
In addition, in the case of aeroplane operations in Class G at or below 3,000 ft above mean sea level or 1,000 ft above ground level (whichever is higher), the following minimum conditions were stipulated:
a flight visibility of 5,000 m
that the aeroplane shall be maintained clear of cloud and in sight of the ground or water
that a radio must be carried and used by the pilot on the correct frequency.
In this case, the area and aerodrome forecasts for Avalon and the surrounding area indicated that visibility was reduced to 5,000 m and a scattered cloud base of 1,500 ft around Avalon. In addition, there was an overall reduced visibility in the region.
Visual flight into Instrument Meteorological Conditions
The safety risks of VFR pilots flying from VMC conditions into instrument meteorological conditions (IMC)[14] are well documented. This has been the focus of numerous ATSB reports and publications, as VFR pilots flying into IMC represents a significant cause of aircraft accidents and fatalities. In 2013 the ATSB Avoidable Accidents series was re-published. Of these publications, the booklet titled Accidents involving pilots in Instrument Meteorological Conditions outlined 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 (2005) found that ‘about two-thirds of all general aviation accidents that occur in instrument meteorological conditions (IMC) are fatal’.
Wiggins and O’Hare (1995) explained that when pilots are not trained or qualified to fly in IMC and find themselves in these conditions, ‘the result will almost inevitably involve loss of control of the aircraft resulting in a fatal crash’.
Loss of visual cues and spatial disorientation in low visibility conditions
Gibb and others (2010) explain that seeing the horizon is ‘crucial for orientation of the pilot’s sense of pitch and bank of the aircraft.’ In conditions of low visibility, the horizon may not be visible to the pilot, during which time they can become rapidly disorientated. Newman (2007) found that ‘the major environmental factors [that contribute to spatial disorientation] are related to time of day and the ambient weather conditions. Poor visual cues are a function of most disorientation illusions, so flight at night or in conditions of bad weather can set a pilot up for a disorientation experience’.
In a discussion of spatial disorientation, Benson (1999) defined the experience as follows:
Spatial disorientation is…[where] the pilot fails to sense correctly the position, motion or attitude of the aircraft or of him/herself [resulting in] errors in perception by the pilot of their position, motion or attitude with respect to their aircraft...
Newman (2007) summarised the primary reason for spatial disorientation as follows:
The visual system is by far the most important of the three systems, providing some 80 per cent of the raw orientation information. In conditions where visual cues are poor or absent, such as in poor weather or at night, up to 80 per cent of the normal orientation information is missing. The remaining 20 per cent is split equally between the vestibular system and the proprioceptive system, both of which are prone to illusions and misinterpretation. In poor or absent visual cue situations, humans are forced to rely on the remaining 20 per cent of orientation information, which is less accurate…In the aviation setting, such a situation can then result in any number of well-described SD [spatial disorientation] illusions being experienced by the pilot…The majority of disorientation events are associated with poor visual cues (as in IMC or night flight).
Extensive research on spatial disorientation indicates that loss of control will likely occur between 60 seconds (Benson, 1983 in Gibb and others, 2010) and 178 seconds (Newman, 2007) after the loss of visual reference. This is the case even when the aircraft is in straight and level flight at the time vision is lost, and is shorter still if the aircraft is in a turn. Gibb and others (2010) state that ‘spatial disorientation accidents have fatality rates of 90–91 percent, which indicates how compelling the misperceptions can be’.
Pilot instrument flying proficiency
When there are no external visual cues, the ability to fly on instruments is essential. Research from the United States has shown that pilots without instrument ratings are five times more likely to have accidents in degraded visual conditions than pilots with instrument ratings (Groff and Price, 2006). The National Transportation Safety Board also noted that ‘Tests and experience have shown that non-instrument-trained pilots or non-proficient pilots are rarely successful in overcoming spatial disorientation’ (NTSB, 1988).
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.’ Simulator experiments at the University of Illinois determined that on average, a pilot with no instrument training can expect to retain control of their aircraft for 178 seconds after entering bad weather and losing visual contact (ATSB, 2011).
Although instrument flying proficiency is a very important defence against spatial disorientation, many studies have shown overall flying experience has little, if any, influence on spatial disorientation accident rates (Gawron, 2004). Newman (2007) noted that spatial disorientation can affect ‘any pilot, any time, any where, in any aircraft, on any flight, depending on the prevailing circumstances’.
Related occurrences
The previously-discussed ATSB research reports and educational material were based on occurrences up until 2013 (see the section titled Visual flight into Instrument Meteorological Conditions). In the period 2014 through to October 2016 there were 28 reported occurrences (not including this accident). Six of these included a decision by the pilot to divert or return to the departure airport, and another eight pilots sought assistance from ATC.
In addition, a number of recent ATSB investigations examined VFR into IMC occurrences. Of these, three are summarised below and are available at www.atsb.gov.au.
On 15 August 2011, the pilot of a Piper PA-28-180 Cherokee aircraft, registered VH-POJ, was conducting a private flight transporting two passengers from Essendon to Nhill, Victoria under the 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[15], 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 21 February 2014, the pilot of a Piper PA-28R aircraft, registered VH-TBB, departed Scone, New South Wales on a private flight to Warwick, Queensland. The flight was planned under the VFR.
The flight proceeded normally until the pilot encountered an increasing amount of cloud and light rain showers while en route between Inverell and Warwick. The pilot initially attempted to pass beneath the cloud, but had difficulty maintaining VMC. Although the pilot reported the cloud appeared to be relatively light with ill-defined edges, they found that forward visibility was restricted. The pilot advised ATC of occasionally encountering IMC, and with the aircraft intermittently identified on radar, ATC was able to assist the pilot with relevant advice.
The pilot had undertaken some instrument flight training about 2 years prior to the incident, which they reported had provided some confidence with respect to aircraft control in marginal conditions.
On 9 July 2014, at about 1340 Eastern Standard Time, a Cessna 206, registered VH-NCR, departed Dubbo, New South Wales on a private flight to the Gold Coast and Archerfield, Queensland, under the VFR, with three passengers on board.
When about 15 NM (28 km) south of Inverell, the pilot observed the weather deteriorating with low cloud about the ranges, and elected to climb and operate VFR on top of the cloud. As the aircraft climbed above 5,000 ft, the pilot observed a widespread frontal mass of cloud with tops around 12,000 ft. As a result, they contacted Brisbane Centre ATC and requested navigation assistance and ATC provided updated weather information.
The pilot initially considered a diversion to Moree, however, they were able to descend through a break in the cloud and elected to divert to Inverell. A turn was commenced, but passing about 3,800 ft during the turn, the aircraft entered cloud. The pilot immediately applied full power and commenced climbing until the aircraft cleared cloud at about 5,000 ft. The pilot diverted to Gunnedah.
One of the safety messages included in the report was to encourage pilots to make conservative decisions when considering how forecast weather may affect their flight. If poor weather is encountered en route, timely and conservative decision making may be critical to a safe outcome.
Purpose of safety investigations & publishing information
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 1 September 2015, a Cessna 180C aircraft, registered VH-FDH (FDH), departed Normanton for Karumba Airport, Queensland at about 1435 Eastern Standard Time (EST). The pilot and two passengers were on board for the private flight. The aircraft had a tail wheel landing gear and the landing technique planned to be used was a wheel landing (see Landing techniques below).
At Normanton, the aircraft was refuelled and departed at almost maximum take-off weight. The aircraft climbed to about 1,000 feet for the short distance to Karumba (about 20 NM). On approaching Karumba, the pilot used the aircraft radio to contact another pilot who had just landed at Karumba to ascertain the weather conditions and to determine the most suitable runway for a landing. The pilot of the aircraft that just landed indicated to the pilot that the wind was directly across the runway from the north-west and either runway direction would be suitable for a landing. They decided to land on runway 21 (Figure 1) and joined the circuit on the downwind leg. On downwind, the windsock was observed and confirmed that the wind direction was directly across the runway from the north-west and the pilot estimated the wind speed to be about 10 knots.
Accident site of Cessna 180C, VH-FDH
Source: Carpentaria Shire Council
Figure 1: Map of Karumba Airport
Source: Google earth, modified by the ATSB
The aircraft was established in a stable final approach and the pilot determined that there was no crosswind correction required. The main wheels touched down firmly on the runway and the aircraft bounced about 3 to 4 feet. The pilot moved the control column forward slightly to stop the tail from touching the runway. The main wheels touched again at about the same time as the pilot noted that the nose started to move to the right (turning into wind). The pilot moved the aircraft controls to straighten the aircraft in line with the runway, but the aircraft did not respond to the correction. The tail continued to move quickly around (ground loop) [1] before the pilot could take any other action. The pilot was pushed up against the cockpit door. A very loud bang was heard as the left main landing gear failed, the left wing folded up and the fuselage tilted onto its side where the aircraft skidded a short distance to a stop. The aircraft stopped, almost pointing back in the opposite direction to the landing, partly on the grass beside the runway (Figure 2). The pilot turned off the engine magnetos, aircraft fuel, and electrical master switch. The two passengers exited the cockpit right door with the help of bystanders and then the pilot exited the same way. The pilot received minor injuries and the two passengers were uninjured. The aircraft was substantially damaged.
Figure 2: Cessna C180 FDH accident site
Source: Carpentaria Shire Council
Landing techniques
There are two landing techniques that can be used in tail wheel aircraft. A wheel landing is where the tail of the aircraft is held off the runway and the main wheels touch down first and then the tail wheel. The other landing technique used in a tail wheel aircraft is the three-point landing where the two main wheels and tail wheel touch the runway together.
Pilot training and tail wheel experience
The pilot had about 1,200 total flight hours with about 84 hours in tail wheel aircraft. The majority of landings in those tail wheel aircraft were three-point landings. The pilot commenced training in 2006 for a tail wheel endorsement, initially training in an Avions Mudry CAP 10, where only three-point landings were practiced. The pilot gained further training in an American Champion Super Decathlon, focussing on the wheel landing technique. During an aerobatics and formation endorsement in the Super Decathlon, the pilot revised both wheel and three-point landings. The pilot was also checked-out to fly an Aviat Aircraft Husky and a de Havilland Chipmunk, although reported only having a few hours in each. The pilot conducted a biannual flight review in March 2015 in a Cessna 172 (tricycle landing gear aircraft). The pilot had flown one other Cessna 180 and in that aircraft, had conducted three-point landings.
Of the pilots 84 hours in tail wheel aircraft, 30 were in a Cessna 180, and in the preceding 30 days, about 23 hours were in FDH.
Pilot comment
The flight was part of an air race and prior to the accident they had conducted about 20 hours of flying, departing Jandakot, and landing at Esperance, Forrest, Ayers Rock, Alice Springs, Davenport Downs, Winton, and Normanton. Of those landings, the pilot reported not being happy with any of the landings. The pilot indicated that this was the first landing in the aircraft that was conducted at almost the maximum landing weight and with a significant crosswind. All the other landings were with little to no crosswind component.
The pilot reported that the owner of FDH, who was also a pilot (medical not current), was extremely proficient at conducting wheel landings and wanted the pilot to conduct wheel landings in FDH. The pilot had conducted circuits with the owner about 2.5 weeks prior to the air race and recalled mentioning to the owner that they felt more comfortable conducting three-point landings.
The pilot reported that during the landing, they were very focused on keeping the aircraft straight with the runway and recovering from the bounce. On another landing in FDH where the aircraft had bounced about 3 to 4 feet, the pilot reported resolving the landing without going around.
Safety message
The US Federal Aviation Administration (FAA) discusses in their publication Airplane Flying Handbook Chapter 13 Transition to Tailwheel Airplanes the importance to land with the aircraft in the longitudinal axis exactly parallel to the direction the aircraft is moving along the runway. If the aircraft lands while in a crab or while drifting, it imposes severe side loads on the landing gear and imparts ground looping (swerving) tendencies. The handbook is available from the FAA website.
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 20 July 2015, the pilot of a Bell 206L3 (Longranger) helicopter, registered VH-BLV (BLV), conducted a charter flight from Essendon Airport to Falls Creek, Victoria, with five passengers on board. The aircraft took off from Essendon close to its maximum take-off weight. Due to the weight, and therefore fuel limitations, the pilot landed and refuelled at a property near Lake Eildon. At about 1000 Eastern Standard Time (EST), the helicopter departed from the property for the 60 NM flight to Falls Creek, again close to its maximum take-off weight.
At about 1030, while 700 ft above ground level and tracking from the north-west, the pilot conducted a shallow approach towards the helipad at Falls Creek (Figure 1). As the helicopter descended to about 50 ft above ground level, the pilot found that significantly more power was required to conduct the approach than anticipated. The pilot assessed that there was insufficient power available to continue to land, and elected to abort the approach. The pilot pushed forwards on the cyclic[1] to increase the helicopter’s airspeed and conducted a left turn towards the valley.
Figure 1: Falls Creek helipad, approximate helicopter track and wind direction
Source: Google earth and pilot recollection – annotated by the ATSB
As the helicopter turned left, it started to yaw[2] rapidly towards the right. The pilot applied full left pedal to counteract the yaw, but the helicopter continued to yaw. The helicopter turned through one and a half revolutions, as the pilot lowered the collective.[3] Lowering the collective reduced the power demand of the power rotor system, thereby increasing the ability of the anti-torque pedals to stop the right yaw. The combination of lowering collective and applying forward cyclic to gain forward airspeed, allowed the pilot to regain control of the helicopter. The pilot then conducted a left turn towards the helipad and made an approach to the helipad from an easterly direction. The helicopter landed following the second approach without further incident.
The pilot and passengers did not sustain any injuries and the helicopter was undamaged.
Weather
The pilot expected that the wind at Falls Creek would be variable at 2 kt, as it had been on departure from Essendon. The pilot did not see the windsock at the helipad prior to conducting the approach.
The Bureau of Meteorology provided the ATSB with a report of weather observations for Falls Creek. The automatic weather station is located south of the helipad at about 5,790 ft above mean sea level, above the village. Between 1020 and 1040, the recorded wind speed was from 17 to 20 kt, gusting to 24 kt, and wind direction was from 327° to 344° (degrees true), or 314° to 331° (degrees magnetic). The temperature was 1 °C.
Pilot comments
The pilot reported that the following combination of factors contributed to the incident:
Unfamiliarity with the landing site and area.
Inexperience operating at altitude, and unfamiliarity with the associated power requirements. The helipad at Falls Creek is at an elevation of about 5,000 ft above mean sea level.
Lack of experience in the aircraft type – although the pilot had about 60 hours experience in the Bell Jetranger, this was only the pilot’s second flight in the Longranger.
High all up weight.
Incorrect assessment of the wind direction – the pilot assumed that the wind would be light and variable at Falls Creek as it was had been on departure from Essendon. During the approach, the pilot assessed that the wind was from the right or a tailwind gusting to about 15 kt.
Operator comment
The operator of VH-BLV assessed that the unanticipated yaw was a result of too little pedal input, applied too late. This was most likely due to a combination of the pilot’s inexperience on the 206L3, and being surprised by the downwind approach.
Hover ceiling
Hovering requires more power than any other flight regime. Additionally, hovering at higher altitudes requires more power than to hover at lower altitudes. The ‘hover ceiling’ is the height at which the power available equals the power required to hover. An increase in power increases the main rotor torque. This additional torque needs increased tail rotor thrust, to prevent the helicopter from yawing.
The Bell 206 L3 flight manual provides a Hover ceiling – out of ground effect[4] chart. At 5,000 ft, a temperature of 0 °C, and a gross weight of about 1,814 kg (4,000 lb), the helicopter was just within the chart’s hover ceiling envelope. This indicates that adequate power should have been available to hover with those parameters. However, the wind direction and velocity also affect hovering performance.
A stronger head wind reduces the power required to hover, while a tailwind increases the power required to hover. On the initial approach to the helipad, a tailwind meant that an increase in power and tail rotor thrust was required. The increased tail rotor thrust absorbs power from the engine, which means less power is available for the main rotor to produce lift. This led to the pilot’s assessment of insufficient power available, and decision to discontinue the approach.
Unanticipated right yaw
The US Federal Aviation Administration (FAA) Helicopter flying handbook describes loss of tail rotor effectiveness (LTE) or an unanticipated yaw, as ‘an uncommanded, rapid yaw towards the advancing blade which does not subside of its own accord’. It is caused by an interaction between the main rotor and tail rotor.
At high altitudes, the lower air density reduces tail rotor thrust and efficiency. Therefore, when operating at high altitudes and high gross weights, particularly while hovering or at low airspeeds, the tail rotor thrust may not be sufficient to maintain directional control. This can result in unanticipated yaw or LTE. In these circumstances, the hover ceiling is effectively limited by the tail rotor thrust, rather than the power available.
In this incident, other factors may also have contributed to the unanticipated yaw: low and slow flight outside of ground effect, a low speed downwind turn and a large change of power at low airspeed as the pilot aborted the approach.
The US Federal Aviation Administration Advisory Circular, Unanticipated right yaw in helicopters, stated that unanticipated right yaw, or loss of tail rotor effectiveness (LTE) has been determined to be a contributing factor in a number of accidents. These mishaps have occurred at low altitude and in low-speed flight, often on final approach to landing. Unanticipated right yaw may occur during any manoeuvre in which the pilot is operating in a high-power, low-airspeed environment with a left crosswind (in aircraft with counter-clockwise blade rotation) or tailwind.
Three additional factors can significantly influence the severity of LTE:
gross weight and density altitude
low indicated airspeed
a rapid application of power, causing power droop.
In order to reduce the onset of LTE, when manoeuvring between hover and 30 kt, the pilot should:
Avoid tailwinds.
Avoid out of ground effect hover and high-power demand situations, such as low-speed downwind turns.
Be aware of wind direction and velocity. A loss of translational lift results in an unexpected high-power demand and an increased anti-torque requirement.
Be aware that if a considerable amount of left pedal is being maintained, a sufficient amount of left pedal may not be available to counteract an unanticipated right yaw.
Stay vigilant to power and wind conditions.
If a sudden unanticipated right yaw occurs, the pilot should:
apply full left pedal
simultaneously move cyclic forward to increase speed
if altitude permits, reduce power.
Safety message
Pilots should understand and avoid conditions that are conducive to uncontrolled yaw or loss of tail rotor effectiveness. Pilots can reduce their exposure to LTE by maintaining awareness of the wind and its effect on the helicopter. If a pilot encounters unanticipated yaw, quick application of the correct response is essential to recover control of the helicopter. The ATSB reported on an incident involving LTE in AO-2013-121.
This incident also highlights the effect of gross weight and airfield elevation on aircraft performance. Understanding controllability issues at the limits of the normal operating envelope can assist pilots in recognising the symptoms of reduced aircraft performance. Further information is available in ATSB report AO-2013-203.
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.
The pilot had planned to land the aircraft in a paddock on his father's property. During the attempted landing, the nose landing gear broke off and the aircraft overturned. Investigation revealed that the landing was attempted in a paddock covered in dense grass ranging from 500 to 700 millimetres in length. The density of the grass caused the nose gear to break off. The pilot said that he was "misinformed on strip conditions and unable to identify grass length" from the air.
Significant Factors
The surface condition of the landing area selected by the pilot was unsuitable for use as a landing area.
The pilot was unaware of the surface condition prior to attempting to land.
