Collision with terrain

Safety summary

What happened

At about 0825 Eastern Standard Time on 9 January 2019, an Insitu ScanEagle X200 (X200) unmanned aircraft system was launched to conduct ‘beyond visual line of sight’ aerial survey work in the Woleebee Creek area of Queensland. The flight crew consisted of two pilots and two ground crew.

Shortly after launch, one of the ground crew observed the X200 pitch up and then enter an aerodynamic stall. The flying pilot commenced the emergency procedures for a stall-spin, however the X200 self-recovered before the checklist was completed. At about the same time the pilots received an alert indicating an airspeed sensor failure and initiated the associated emergency procedure checklist.

Before visual sight was lost, the ground crew observed the X200 oscillating in pitch as it continued to fly to the programmed first waypoint. While the flying pilot was executing the emergency procedures checklist, the X200 entered a second aerodynamic stall. Following self‑recovery from a low height above terrain, the X200 commenced a climbing orbit. Shortly after, the X200 entered a third aerodynamic stall, this time from a height that was insufficient for recovery, and collided with terrain. There was no post-impact fire and the X200 was destroyed. There were no reported injuries to people or damage to infrastructure. A post-incident inspection of the X200 identified a partial blockage in the pitot system.

What the ATSB found

The investigation found that the blockage in the pitot-static system resulted in unreliable airspeed data being supplied to the autopilot. Unreliable airspeed data led to the X200 entering an aerodynamic stall at a height that was insufficient for recovery.

During the pre-flight checks, there were opportunities for the erroneous airspeed indications to be identified. However, they were not recognised by the crew or flagged by the ground control station.

What's been done as a result

Following the occurrence, the manufacturer revised their procedures to reduce the risk of aircraft being affected by a pitot blockage. Additionally, all of the operator’s pilots underwent refresher training. This included emergency procedures simulator experience.

The X200 manufacturer revised their procedures to provide support to pilots and ground crew in correct assembly of the articulated turret, identifying anomalies (on the ground and in-flight), and steps for aircraft recovery in the event of a departure from normal flight. In addition, updates to the operational software would ensure any spurious on‑ground anomalies were alarmed, to prevent the X200 being launched with an unidentified issue.

Safety message

This occurrence highlights the importance of confirming the significance of any unexpected observations during the pre-flight checks, to minimise the risk of the aircraft departing with an unserviceability. In addition, providing pilots and ground crew with the reasoning behind specific checks and procedures can enhance their ability to identify anomalies and perform the appropriate corrective actions in a timely manner.

Insitu ScanEagle X200

Source: Insitu Pacific

 

The occurrence

What happened

On the morning of 9 January 2019, the Insitu Pacific (the operator) crew prepared to conduct a 4‑hour ‘beyond visual line of sight’ survey flight, in the Woleebee Creek area, about 350 km west‑north‑west of Brisbane, Queensland. The flight was being conducted by an Insitu ScanEagle X200 (X200).

The crew consisted of two remote pilots^[1] (one acting as mission controller/pilot in command and one acting as pilot flying) and two ground crew (who were also qualified remote pilots).^[2] The two pilots for this flight were located in the ground control station (GCS).^[3] Headsets were worn by all crew members, to enable effective communication. All crew reported to being ‘refreshed’ and looking forward to the day’s flight.

The X200 was launched at 0825 Eastern Standard Time.^[4] The crew described the launch as ‘textbook’. The secondary ground crew member maintained visual contact with the X200, typically done until advised by the pilots that they had video feedback from the on-board camera.^[5] He reported that, about one minute after launch, the X200 pitched up ‘quite high’, before entering an aerodynamic stall.^[6] He immediately advised the pilot flying (PF) with the standard phrase ‘wings level, wings level, you’re stalling’. At this time, the primary ground crew member also observed the X200 in a ‘left-hand spin’ and advised the PF ‘you’ve stalled, wings level, wings level’.

At the same time, the GCS identified the stall condition and projected the ‘stall-spin’ emergency procedures checklist to the display. The PF commenced the checklist items, however the X200 self‑recovered before the checklist was completed. The ground crew reported the X200 recovered ‘low to the ground’ and then commenced a climb to return to the programmed flight altitude.

At about the time of the recovery from the first stall, the GCS initiated the warnings and emergency procedures checklist for an ‘airspeed failure’. Upon the mission controller’s direction, the PF commenced the airspeed failure checklist. The ground crew reported that following a ‘steep’ climb, the X200 was then observed to be ‘porpoising’ (oscillating in pitch) while it continued to the first programmed waypoint. Shortly after this, the X200 flew beyond visual sight of the ground crew.

Telemetry data showed that, about 90 seconds after the first stall, the X200 entered a second stall. The X200 self-recovered again, at about 150 ft above the ground, and commenced a climbing orbit. After about 30 seconds, the X200 entered a third stall and impacted the ground eight seconds later. The mission controller advised the ground crew that the X200 had been lost. Total flight time was less than four minutes and distance from the launch site to the collision with terrain location was about 4.75 km (Figures 1 and 2).

Figure 1: X200 flight path

Source: Insitu Pacific and Google Earth, modified by the ATSB

Figure 2: X200 flight profile

Source: Insitu Pacific and Google Earth, modified by the ATSB

Post-accident recovery and inspection

The aircraft impacted the ground near vertically, there was no post-impact fire and the X200 was destroyed. There was no evidence of in-flight break-up or collision with vegetation or infrastructure prior to the impact. In addition, there were no reported injuries. The operator conducted an examination of the occurrence X200 and identified a partial blockage in the pitot system, which was subsequently confirmed by the manufacturer. The blockage appeared to be a combination of a section of O-ring debris and grease.

Flight operations

The Civil Aviation Safety Authority (CASA) issued the operator with an authorisation to operate the X200 beyond visual line of sight, within a defined area. Some of the authorisation’s requirements included:

• all remote pilots were to hold a CASA authorisation
• a mode C transponder^[7] was to be operational, and transmitting accurate barometric altitude, on all flights
• a primary and secondary ‘fail safe’ mode to ensure that, in the event of data-link loss, the X200 did not depart the area of operation and would land at a pre-determined location
• air traffic control at Brisbane was to be advised of the intended operation 15 minutes prior to launch, and the crew were to maintain standard airspace radio procedures for the duration of the flight
• the operator was to ensure a current Notice to Airmen (NOTAM)^[8] was active for each operation
• the X200 was only to be operated in visual meteorological conditions.

In addition to the CASA authorisation, the operator’s procedures included:

• no flight over populous areas
• operations were conducted at altitudes intended to avoid agricultural and passenger aircraft.

Remote pilots underwent a 10-week course prior to being endorsed to operate the X200. This course included a theory component and time in the simulator. The pilots recalled that ‘airspeed failure’ was included in the course, however they felt that particular emergency procedure wasn’t focussed on as ‘heavily’ as others.

The accident site was located within the defined operational area, which was in accordance with the authorised requirements.

Aircraft information

The ScanEagle is a small, long-endurance, low-altitude unmanned aerial system (UAS) built by Insitu, a subsidiary of Boeing, and is used for defence and civilian applications (the X200 variant). The X200 (Figure 3) has a wingspan of 3.1 m, a length of 1.6 m, maximum take‑off weight of about 23 kg and a typical cruise speed of 50-60 kt.

The nose module (payload) on the X200 is interchangeable, depending on the type of mission being flown, and was supplied by the payload manufacturer. The payload fitted to the X200 at the time of the occurrence consisted of a camera assembly located in an articulated turret (turret). The camera could be directed through a defined fore/aft arc and the turret rotated through 360˚.

The pilot controls the X200 entirely through the aircraft autopilot from launch until recovery. The aircraft’s flight path is controlled by position, altitude and airspeed commands through the remote pilot station computer (part of the ground control station), which is then sent to the aircraft autopilot. The pilot does not have a control yoke, or equivalent, that links directly or indirectly to the aircraft control surfaces.

Typically, once the X200 has launched, the pilot commands it through a pre-planned sequence of locations and orbits around each location of interest. At the completion of the flight’s activities, the pilot would position the aircraft in preparation for the recovery phase using the same method of control. In this instance, the emergency procedure checklist actions involved the pilot utilising additional X200 autopilot control laws in order to negate the erroneous airspeed information.

Figure 3: X200 with articulated turret

Source: Insitu Pacific, modified by the ATSB

Pitot-static system

The pitot-static system senses ram air pressure through the pitot probe (on the forward face of the payload) and static air pressure through the static ports (on each side of the payload). The two pressures are used to calculate true airspeed (TAS) and barometric altitude (Alt). The autopilot uses this data to calculate the minimum and maximum airspeed in relation to the weight of the X200 and to maintain controlled flight.

The pitot and static tubes for the X200 were routed from the pitot probe and static port through the turret and connected to the pitot-static tubing in the fuselage. If not correctly oriented during assembly, the tubes could become pinched, blocked or damaged with turret operation. Obstructed pitot-static tubes have the potential to cause incorrect TAS and Alt calculations, affecting autopilot operation.^[9] In addition, the TAS and Alt indications to the pilots would also be unreliable. The manufacturer alerted X200 operators to this potential condition in November 2017, via both a service advisory and an operational advisory. Damage sustained to the X200 during this occurrence prevented testing for possible turret interference.

The service advisory (SA) provided expanded procedures for pitot and static tube routing and connection, and inspection procedures if an anomaly was identified during pre-flight checks. A review of the X200 maintenance records showed the turret had been installed as per the SA in July 2018. Since then, it had been operated for about 80 hours, without indication of turret interference.

The operational advisory (OA) included:

• information about how to identify and troubleshoot different types of incorrect TAS and Alt indications on the ground and in-flight
• a pre-flight function test to identify incorrect TAS and Alt indications shown on the ground control station (GCS) program
• in-flight emergency procedures to normalise the incorrect TAS and Alt indications and avoid loss of controlled flight.

The function test was to be completed before every flight and the OA provided examples of how anomalies with the pitot-static tubing may appear on the GCS display. Where inspection and routing of the pitot-static tubes did not rectify the anomaly, the turret was to be replaced prior to next flight. The OA procedures had been incorporated into the GCS program at the time of the occurrence.

In addition, the payload manufacturer identified a quality issue with the turret assembly procedures that had the potential to induce a blockage in the pitot system. The operator identified that the occurrence X200 was affected by this quality issue, consisting of excess grease and O‑ring debris forming the pitot-system partial blockage. The X200 manufacturer published procedures to inspect (and, if required, clean) turrets that were in-service and prior to fitment. The operator examined the remainder of their fleet with these revised procedures, with no further occurrences identified.

Pre-flight checks

As part of the pre-flight procedures, the primary ground crew conducted an inspection of the X200 while the secondary ground crew readied the launcher and recovery systems. At the same time the pilots, located in the GCS, conducted their pre-flight systems checks, which included a function test of the pitot-static system (Figure 4). This test included the primary ground crew fitting a sealed clear tube to the pitot probe, which increased pressure in the system and simulated an airspeed indication associated with forward flight (equivalent to TAS). The procedure stated that any reduction in pressure (TAS) indicated on the GCS during the test, equal to or greater than the specified limits, was indicative of a system leak that required rectification prior to flight.

During the test, a slow rise of about 10 kt TAS occurred, while the indicated altitude remained steady. The OA detailed that if the TAS ‘increases slowly without turret movement or pressurisation of the pitot-static system’, this was an indication of a blockage in the pitot-static system. As per the OA, turret movement had the potential to induce a restriction in the pitot system tubing, which could ‘clear’ with subsequent movement. The pitot system was pressurised and the turret was being operated for part of this test and as such, the rise in TAS as a possible indication of a blockage may have been difficult to identify. Following this occurrence, a revised OA amended the criteria for the slow increase in TAS to show ‘at any time’ during the procedure, removing any ambiguity surrounding pitot pressurisation and turret movement during the tests.

With no pitot system leak identified by the pilots, the tooling was removed. At this time, the pilot flying (PF) commented that the TAS was ‘slow to release’ (return to pre-check indication). The primary ground crew member reported that he heard this comment however, he took no action as he wasn’t aware of the significance of this indication. The pilot pre-flight checklist identified that slow to release pressure was indicative of a blockage in the pitot system.

Following completion of the crew’s pre-flight checks, the GCS continued with the system self‑checks, while the crew met outside for a pre-mission brief, as per their standard procedure. During the time the crew were outside, the GCS self-check indicated an anomaly within the pitot‑static system. In this instance, there was an increase over time in TAS, while the Alt decreased. For this indication, the procedures required an inspection of the pitot-static system prior to launch. However, this indication was not flagged or latched.^[10] Therefore, when the pilots returned to the GCS, there was nothing to alert them to this additional indication of a pitot system anomaly.

Figure 4: Pitot pressure test indications

Source: Insitu Pacific, modified by the ATSB

All subsequent pre-flight checks were described as normal. Weather conditions at the time were recorded as overcast conditions, 22˚C, a wind speed of about 6 kt and were described by the crew as ‘ideal’.

Autopilot and the occurrence flight

The X200 autopilot control loops rely on airspeed to control altitude. The target airspeed for the occurrence flight was 53 kt. Recorded data shows that following launch, the TAS reached 70 kt. This resulted in the autopilot commanding a rapid pitch up to try to arrest the perceived high TAS. The pitch attitude was too great for the actual airspeed, which resulted in the X200 entering an aerodynamic stall. Stall recovery took 12 seconds, with an altitude loss of 579 ft (at a rate of 48 ft/s), before the X200 began to climb back to the programmed flight altitude.

Erratic TAS is one of the parameters that can lead to a stall-spin in the X200. Flight data showed that erratic TAS was present from launch, before the turret was unlocked and operated. This was consistent with a blockage of the pitot system, rather than turret interference.

The erratic TAS also resulted in the porpoising flight profile following the first stall and recovery. Following about 80 seconds of porpoising flight, the data showed another rapid increase in TAS. The autopilot likely commanded the X200 to increase pitch attitude, which again resulted in an aerodynamic stall and rapid reduction in height. Within 12 seconds, the X200 had again self‑recovered from the stall, but at a much lower altitude than the first recovery. The second stall required 778 ft for self-recovery (at 64.83 ft/s rate of altitude loss).

This was followed by another extreme increase in TAS, leading to the third stall. This stall was at a similar rate to the second stall. Recovery was again initiated but only 591 ft was available and the X200 collided with terrain, about 9 seconds later (Figure 5).

Figure 5: Flight data showing erratic indicated airspeed and altitude

Source: Insitu Pacific, modified by the ATSB

Safety analysis

Following launch, the Insitu ScanEagle X200 (X200) twice entered an aerodynamic stall and self‑recovered. The X200 entered a third stall, this time at a lower height, and did not recover prior to collision with terrain. The analysis will examine the pre-flight indications of the pitot system blockage and its effect on the flight.

Pre-flight checks

The pre-flight checks provided three opportunities for anomalies in the pitot static system to be detected. There was a slow rise in TAS, which was indicative of an anomaly in the pitot system. The pressurisation of the pitot system and movement in the turret during the pitot-static function test, however, may have meant that the slow rise in TAS and the physical blockage was not obvious. The slow reduction in TAS after the pressure test was an indication of a pitot system blockage. This was noted by some of the crew, however the significance of this indication was not recognised.

The ground control station (GCS) system self-checks showed an additional indication of a pitot system anomaly, however it was not observed by the crew, as they were carrying out other duties at the time. At the completion of the self-checks, there was no ‘flag’ or other indication on the GCS that the pitot system irregularity had occurred. This resulted in the indications of pitot system anomaly not being identified by the crew or flagged by the GCS, resulting the X200 being launched with a blockage in the pitot system.

Unreliable airspeed data

The X200 autopilot uses true airspeed (TAS) and altitude (Alt) data to maintain controlled flight. The blockage in the pitot system resulted in unreliable airspeed data being provided to the autopilot, affecting calculation of TAS. While there remained the possibility that the turret interference may also have been present, it could not be determined as contributory in this occurrence. Flight data showed that erratic (TAS) data was present from launch, before the turret was unlocked and operated. Subsequent movement of the turret may have alleviated any turret‑induced restriction in the pitot system but due to the presence of the identified blockage, the airspeed data was unreliable even without any turret interference.

Following launch, the autopilot interpreted the TAS as increasing and increased the pitch (nose up) to maintain target airspeed. This resulted in the X200 nose-up attitude being too great for the actual airspeed and led to an aerodynamic stall. The X200 self-recovered and recommenced the climb to operating altitude.

Following recovery from the first stall, flight data showed the TAS was oscillating by up to 30 kt, resulting in the ‘porpoising’ flight profile, indicative of the autopilot trying to maintain controlled flight using unreliable airspeed data. A rapid 30 kt increase in TAS likely led to the autopilot increasing pitch attitude, resulting in the second aerodynamic stall. Again, the X200 self-recovered, however at a much lower altitude. A third rapid TAS increase followed shortly after, leading to the final stall, with insufficient height available for recovery.

Findings

These findings should not be read as apportioning blame or liability to any particular organisation or individual.

• Erroneous airspeed system indications during the pre-flight checks were not identified by the crew or flagged by the ground control station, resulting in the X200 being launched with an unserviceable pitot-static system.
• A blockage in the pitot-static system resulted in unreliable airspeed data being supplied to the autopilot.
• Unreliable airspeed data led to the X200 entering an aerodynamic stall at a height that was insufficient for recovery.

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.

The operator

As a result of this occurrence, the operator advised the ATSB that the following safety actions, in cooperation with the X200 and payload manufacturers, have been undertaken:

Pilot training

Following the occurrence, all of the operator’s remote pilots underwent refresher training with a focus on identification and emergency procedures regarding incorrect true airspeed (TAS) and/or barometric altitude (Alt) indications. The training consisted of theory (including ‘how’ the system works and symptoms of pitot-static blockage) and several hours’ simulator experience of failures and use of emergency procedures. Feedback from the pilots following this training was positive. In addition, the ATSB was advised that the X200 manufacturer will amend the ab-initio pilot training to highlight pitot-static system anomalies and associated pre- and in-flight procedures.

Training and enhanced procedures can provide ‘reasoning’ behind the steps. This can assist pilots and maintainers in their understanding of indications and events, prompting effective actions and timely resolution.

The manufacturer

Documentation and procedures

The X200 manufacturer published a revised Operational Advisory (OA) on 18 February 2019. One amendment in this revised publication was the inclusion of an image from the occurrence X200, showing the Ground Control Station indication for ‘slow to release’ pitot pressure. The criteria for the slow increase in TAS was also amended to ‘at any time’ during the procedure, removing any ambiguity surrounding pitot pressurisation and turret movement during the tests.

In addition, the revised OA included an additional caution (in red text) warning that the ‘TAS error exceeds launch limit alarm is disabled for pre-flight pitot-static system checks. Therefore, it is critical to monitor the TAS-ALT-Tachometer plot throughout the on ground phase for any abnormal TAS or Alt signatures’. The operator reported that the X200 manufacturer advised a ‘latching system alarm’ would be incorporated into the next software release (scheduled for mid-2019) to alert the crew where the TAS has exceeded a threshold during on-ground checks.

Further, the manufacturer revised their procedures for assembly of the turret and provided a reworked procedure to X200 operators to reduce the risk of in‑service aircraft being affected by a pitot blockage.

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 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2019 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.

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1. A remote pilot licence (RePL) is required for commercial operations involving remotely piloted aircraft systems (RPAS) that are greater than 2kg maximum take-off weight.
2. Minimum crew for a deployment consisted of two pilots and one ground crew. When teams consisted of two ground crew, they were identified as primary and secondary. The secondary crew member assisting the primary as directed.
3. The computers and associated equipment required for flight operations were located in a converted climate-controlled shipping container and collectively known as the GCS. The pilots were located in the GCS for the entire flight, including launch and recovery. The launch and recovery sites were determined each mission and located to best suit the weather and intended flight, which could be some distance from the GCS.
4. Eastern Standard Time (EST): Coordinated Universal Time (UTC) + 10 hours.
5. The GCS provided location information via GPS and maps. The video feedback provided additional situational awareness for the pilots.
6. Aerodynamic stall: occurs when the airflow separates from the wing’s upper surface and becomes turbulent. A stall occurs at high angles of attack, typically 16˚ to 18˚, and results in reduced lift.
7. A mode C transponder transmits both aircraft identification and altitude.
8. A NOTAM advises personnel concerned with flight operations of information concerning the establishment, condition or change in any aeronautical facility, service, procedure, or hazard, the timely knowledge of which is essential to safe flight.
9. ‘TAS’ terminology in the remainder of the report refers to the TAS calculated from the unreliable pitot pressure (airspeed) data.
10. A flag, or latch, is a special mark indicating that a piece of data is unusual. This alert will remain, even if the event has passed, until a clearing action has been conducted by a member of the crew.

Preliminary report published: 30 January 2019

This preliminary report details factual information established in the investigation’s early evidence collection phase and has been prepared to provide timely information to the industry and public. Preliminary reports contain no analysis or findings, which will be detailed in the investigation’s final report. The information contained in this preliminary report is released in accordance with section 25 of the Transport Safety Investigation Act 2003.

What happened

On 24 November 2018, at about 0800 Central Standard Time,^[1] a Robinson R22 helicopter, registered VH-KZV, collided with terrain about 125 km east-north-east of Alice Springs Airport. The pilot was fatally injured and the passenger was seriously injured. The helicopter was substantially damaged.

The pilot held a private helicopter pilot licence and was employed by a cattle station for general flying duties, which included cattle mustering. On the morning of the accident, the pilot and passenger were tasked to assist with the recovery of a motor vehicle, located about 63 km east-north-east of Ambalindum Station (departure point). A station hand assisted them with preparing the helicopter for departure. The station hand could not recall the actual time of departure, but estimated it was between 0730 and 0745.

At about 0811, the pilot’s Spot Tracker device transmitted its location in SOS mode.^[2] A local helicopter company in Alice Springs was subsequently tasked by the Joint Rescue Coordination Centre to transport a paramedic to the reported location and conduct a search and rescue. In addition, Ambalindum Station dispatched two employees by road to investigate. The search helicopter pilot located the wreckage of the R22 at the reported location, and the paramedic subsequently attended to the accident pilot and passenger. At about 1045 the paramedic found the pilot deceased and the passenger in a serious condition. The rescue helicopter departed to collect the two station employees who were enroute to assist with the emergency response. The rescue helicopter pilot and the paramedic, with the assistance of the two station employees, retrieved the passenger and transported him to Ambalindum Station for treatment by a retrieval doctor, before transporting him to Alice Springs Hospital for further medical attention.

Figure 1: Robinson R22 helicopter, VH-KZV, main wreckage site

Source: ATSB

The ATSB attended the accident site on 26 and 27 November 2018. The helicopter’s clock had stopped at about 0756. The helicopter had impacted the ground on a downslope, in an easterly direction, and continued down the slope, producing debris as it struck rocks and trees, before crossing a dry creek bed. The helicopter came to rest on the far side of the creek bed, in a southerly direction, with the port side of the helicopter resting against the upslope of the far bank. The main rotor disc struck and separated the rear section of tailcone as a consequence of the accident sequence. Significant torsional deflection of the tail rotor driveshaft intermediate flexible coupling indicated that it was rotating when the strike occurred.

The ATSB found no pre-existing defect with the rotors, transmission, sprag clutch, drive belts or flight controls, which would have prevented normal operation. The main fuel tank had sufficient fuel for flight. A fuel test on site and at the point of departure did not identify any visual contaminates, including water. In addition, fuel samples were collected from the helicopter and departure point fuel pump, for future chemical analysis testing if required. The engine and a majority of the airframe was retrieved from the accident site and transported to Alice Springs. The engine was then removed from the wreckage and transported to Brisbane for further examination under the supervision of the ATSB. Several components and cockpit warning lamps were retained for examination.

Weather and terrain

The accident site was within the MacDonnell Ranges at an elevation of about 1,850 ft, 31 km east of Ambalindum Station. At the time of the accident the weather forecast included moderate turbulence throughout the area. At 0800 the Alice Springs Airport recorded a wind speed of 18 kt, with gusts to 29 kt, from 330 degrees, and a temperature of 29 °C. The Arltunga weather station, located about 40 km west of the accident site, recorded two observations each day. At 0800 it recorded a wind speed of 14 kt^[3] from 360 degrees, and a temperature of 30 °C.

Engine tests and inspections

On 8 and 9 January 2019, inspections and tests were conducted on the recovered engine. Representatives from the workshop, Civil Aviation Safety Authority, insurance company and helicopter owner were present.^[4] No fault was identified that would have prevented normal engine operation. Damage to the engine cooling fan and the presence of dirt inside the number 2 cylinder indicated the engine was operating at the time of initial impact. Scoring damage to the V-belt actuator was identified. The helicopter manufacturer advised the ATSB that the identified damage was consistent with the upper sheave rotating on contact with the actuator as the structure distorted on impact and that the actuator was in the extended position.^[5]

Further investigation

To date, the ATSB has examined the wreckage, interviewed witnesses, consulted with the helicopter manufacturer and collected weather data and analysis from the Bureau of Meteorology.

The ATSB will conduct further enquiries into:

• flight planning
• the weight and balance of the helicopter
• examination of individual components and warning lamps
• analysis of data recording devices
• pilot training and qualifications.

The information contained in this update is released in accordance with section 25 of the Transport Safety Investigation Act 2003 and is derived from the initial investigation of the occurrence. Readers are cautioned that new evidence will become available as the investigation progresses that will enhance the ATSB's understanding of the accident as outlined in this update.

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through: identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2019 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.

1. Central Standard Time (CST): Coordinated Universal Time (UTC) +9.5 hours.
2. The Spot Tracker is a global positioning system tracking device, which uses a satellite network to provide tracking and text messaging. The cattle station owners issued one to each of their employees. The SOS mode of activation indicated an emergency.
3. Mean wind speed recorded over a 10 minute period.
4. The helicopter manufacturer, engine manufacturer and maintenance organisation were invited by the ATSB but did not attend.
5. Normal position for flight.

 

What happened

On 31 October 2018 a Titanium Explorer Autogyro, registered G-0014, collided with terrain approximately 1 km south‑east of Orange Airport, New South Wales. The pilot and passenger sustained fatal injuries. The rotors and masthead were found some distance from the main wreckage, having separated at the cheek plates (Figure 1). The cheek plates sit on either side of the collapsible mast and are designed to secure the mast in the upright position during operation.

The Australian Sport Rotorcraft Association commenced an investigation into this accident and requested technical assistance from the ATSB to examine the cheek plates and their fracture surfaces. Specifically, the ATSB was requested to determine the direction of fracture progression through the plates and to identify any factors that may have contributed to their failure.

To facilitate this work, the ATSB initiated an external investigation under the Transport Safety Investigation Act 2003.

Results

The ATSB examination undertook physical, microscopic and chemical analysis of the cheek plates. These examinations found that the plates had failed due to ductile overstress, commencing at the leading edge and progressing to the trailing edge (when oriented in the direction of travel). The plate’s dimensions and chemical composition were in accordance with manufacturer’s specifications and there was no evidence of any pre-existing defects.

Figure 1: Port and starboard cheek plates as supplied to the ATSB

Source: ATSB

With the completion of the component examinations, the ATSB has concluded its involvement in the investigation of this accident. Any further enquiries in relation to the investigation should be directed to the Australian Sport Rotorcraft Association.

 

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This report has been released in accordance with section 25 of the Transport Safety Investigation Act 2003.

 

On 29 October 2018, Lion Air Flight JT610, a scheduled domestic service from Jakarta to Pangkal Pinang, Indonesia, collided with water in the Java Sea, north of Jakarta, about 13 minutes after take-off. The aircraft, a Boeing 737 MAX 8, registered PK-LQP, was destroyed and all 189 passengers and crew on board were fatally injured.

As the accident occurred in Indonesia, the Indonesian National Transportation Safety Committee (NTSC) was responsible for investigating this occurrence. In accordance with Annex 13 to the Convention on International Civil Aviation, the ATSB appointed an accredited representative to the NTSC investigation. The ATSB provided specialist expertise to support the NTSC in downloading and analysing the flight data recorder (FDR) and cockpit voice recorder (CVR) from the aircraft.

The ATSB has concluded its support of this investigation. On 25 October 2019, the NTSC released the final investigation report into this occurrence and it is available at http://knkt.dephub.go.id/knkt

Any enquiries regarding the investigation and report should, in the first instance, be directed to the NTSC.

On 31 October 2018, an Aeropro 3K, registration 24-7502, collided with terrain 65 km north of Wentworth in NSW. The pilot and passenger were fatally injured.

Recreational Aviation Australia (RAAus) commenced an investigation of this accident and requested technical assistance from the Australian Transport Safety Bureau (ATSB) to download the flight data from a Dynon data logging unit.

To protect the information supplied by RAAus to the ATSB and the ATSB's investigative work to assist RAAus, the ATSB has initiated an investigation under the Transport Safety Investigation Act 2003.

Any enquiries relating to the accident investigations should be directed to RAAus at: www.raa.asn.au.

Updated: 26 March 2019

The ATSB has completed its work attempting to download the recorded data from the Dynon SkyView SV‑D1000 unit supplied by RAAus. A report detailing the work undertaken by the ATSB was provided to RAAus on 15 March 2019.

Preliminary report published: 21 November 2018

This preliminary report details factual information established in the investigation’s early evidence collection phase and has been prepared to provide timely information to the industry and public. Preliminary reports contain no analysis or findings, which will be detailed in the investigation’s final report. The information contained in this preliminary report is released in accordance with section 25 of the Transport Safety Investigation Act 2003.

What happened

On 5 October 2018, at about 1120 Eastern Daylight‑saving Time,^[1] a Bristell Light Sport Aircraft, registered VH-YVX, departed Moorabbin Airport, Victoria, with a pilot and passenger onboard. The purpose of the flight was a navigation exercise in support of the pilot’s commercial pilot training requirements. The passenger held a student pilot licence, but his aviation medical certificate was not current.

At about 1240, following an overfly of the intended waypoint at Stawell Airport, the aircraft was observed by witnesses to conduct a 180° turn towards the east at about 1,500 ft above ground level (Figure 1). Following the turn the aircraft was observed to commence a number of manoeuvres before entering a spin. The pilot was unable to recover control of the aircraft before it impacted terrain.

Figure 1: Aircraft’s flight path and accident site location

Source: Google earth, with Airservices surveillance radar data. Modified by the ATSB

A witness at the aerodrome notified emergency services about the accident. Two other witnesses at the aerodrome utilised an aircraft to locate the accident site and guided the emergency services to its location. The pilot and passenger sustained significant injuries and were airlifted to hospital. The aircraft was destroyed.

Site and wreckage examination

The ATSB conducted an examination of the accident site and wreckage (Figure 2). This examination identified that the:

• aircraft was located in relatively flat and open farmland, which was about 1.7 km south‑east of Stawell Airport
• ground impact marks indicated that the aircraft had impacted terrain in a relatively flat, upright, counter clockwise spin
• flaps were in the retracted position
• elevator trim was in a neutral position.

No pre-impact defects were identified with the flight controls or aircraft structure.

A panel‑mounted avionics unit was removed from the aircraft and taken to the ATSB’s technical facility in Canberra for examination. The stored information was successfully downloaded and included numerous flight and engine parameters recorded during the accident flight.

Figure 2: Accident site of Bristell Light Sport Aircraft, registered VH-YVX

Source: ATSB

Ongoing investigation

The investigation is continuing and will include:

• interviews with parties involved in the accident
• analysis of the downloaded data from the avionics unit and other electronic devices
• examination of the pilot’s qualifications, experience and medical history
• assessment of the aircraft’s flight performance characteristics
• examination of aircraft maintenance and operational records
• examination of the training organisation records and procedures.

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The information contained in this preliminary report is released in accordance with section 25 of the Transport Safety Investigation Act 2003 and is derived from the initial investigation of the occurrence. Readers are cautioned that new evidence will become available as the investigation progresses that will enhance the ATSB's understanding of the accident as outlined in this update. As such, no analysis or findings are included in this update.

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through: identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2018 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.

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1. Eastern Daylightsaving Time (AEDT): Coordinated Universal Time (UTC) + 11 hours.

Safety summary

What happened

The pilot of a Cessna 208B aircraft, registered VH-FAY (FAY), was contracted by the aircraft operator to ferry FAY from Jandakot Airport, Western Australia to Mississippi, United States. On the morning of 27 September 2018 local time, the aircraft departed Saipan International Airport, Northern Mariana Islands, for a planned flight to New Chitose Airport, Hokkaido, Japan. After climbing for about an hour, the aircraft levelled off at flight level (FL) 220.

After 2 hours 20 minutes flight time, the pilot contacted Tokyo Radio flight information service at the first mandatory reporting position. The aircraft passed the next reporting point at the same altitude, 1 hour 20 minutes later, but the pilot did not contact Tokyo Radio as expected. Tokyo Radio made repeated attempts to communicate with the pilot, without success. Having received no communications from the pilot for 4.5 hours, two Japan Air Self‑Defense Force (JASDF) aircraft intercepted FAY. The pilot did not manoeuvre the aircraft in response, in accordance with international intercept protocols.

After about 30 minutes, the JASDF pilots observed FAY descend into cloud. The aircraft descended rapidly and disappeared from radar less than 2 minutes later. Within 2 hours, search and rescue personnel located the aircraft’s rear passenger door. No other aircraft parts were located and the pilot was not found.

What the ATSB found

While the aircraft was in the cruise on autopilot, the pilot almost certainly became incapacitated and did not recover. About 5 hours after the last position report, without pilot intervention to select fuel tanks, the aircraft’s engine stopped, likely due to fuel starvation. This resulted in the aircraft entering an uncontrolled descent into the ocean.

The cause of incapacitation could not be determined. While a medical event could not be ruled out, the pilot was operating alone in an unpressurised aircraft at 22,000 ft and probably using an unsuitable oxygen system, which increased the risk of experiencing hypoxia and being unable to recover.

What's been done as a result

The aircraft operator amended their operations manual to include additional guidance for international ferry flights. They also created an oxygen use guide and a specific risk assessment for positioning (ferry) flights.

Safety message

Operating unpressurised aircraft above 10,000 ft requires careful oxygen management and planning. Where an increased risk of hypoxia exists, good risk management practices should be used for flight planning. Because the effects of hypoxia can be insidious, training in recognition of early symptoms of hypoxia can increase the time available to react, descend and resolve any issues. The Flight Safety Australia (2014) article Do not go gentle: the harsh facts of hypoxia provides further information, including anecdotal experiences of hypoxia.

VH-FAY with full survey equipment installed

Source: Sid Mitchell, Aviation Spotters Online

Safety analysis

Introduction

After departing Saipan and climbing for about an hour, the aircraft levelled off at flight level (FL) 220. An hour later, the pilot made a mandatory position report on HF radio and then no subsequent communications. About 5 hours after the position report, while maintaining FL 220 and the flight planned route, the aircraft descended to the ocean. No wreckage other than a part of the aircraft door was recovered and the pilot was not found, limiting the evidence available.

The analysis will consider reasons for the pilot’s lack of any further communication and the aircraft’s subsequent descent. The investigation identified some operational factors that increased the pilot’s risk of experiencing hypoxia. These factors are explored in detail below.

Pilot incapacitation

The absence of any communication by the pilot after reporting at position TEGOD was almost certainly a result of pilot incapacitation. He did not make any further mandatory position reports, or respond to repeated attempts by Tokyo Radio to communicate on HF radio. The pilot had several alternative means of communication available in case of HF radio failure or failure of the aircraft’s electrical system. He would have been able to communicate using one of those means if not incapacitated, as demonstrated by having successfully sent messages from his standalone Garmin device prior to reaching TEGOD.

Additionally, the pilot did not respond in accordance with international intercept protocols, either by rocking the aircraft wings or turning, when intercepted by two Japan Air Self-Defence Force (JASDF) aircraft. The JASDF pilots were unable to see into the cockpit to confirm whether the pilot of VH-FAY was visibly incapacitated.

No evidence was available from which to determine the cause of incapacitation. The two most likely mechanisms for incapacitation were due to the pilot experiencing a medical event or hypoxia. Although the pilot had a valid medical certificate and was reportedly in good health, a medical event could not be ruled out. Similarly, the pilot’s last communications with Tokyo Radio were not of adequate sound quality to determine whether the pilot was affected by hypoxia at that time. In any case, there was ample time after TEGOD for the pilot to experience hypoxia and be unable to recover at the cruise altitude, before the aircraft reached the next reporting point.

With the pilot incapacitated, the aircraft continued on autopilot. The aircraft’s track and altitude were consistent with the flight director selected to hold flight level (FL) 220 and to follow the GPS programmed track.

Fuel starvation and uncontrolled descent

About 5 hours after the pilot’s last transmission, the JASDF aircraft radar showed FAY start to descend at an increasing rate, which was indicative of engine power loss. In the absence of pilot intervention, the power loss would have resulted from either engine failure or fuel starvation. An engine failure could not be ruled out, however this would had to have occurred in addition to pilot incapacitation, and the likelihood of both these events occurring in the same flight was considered to be low. The engine power loss was therefore considered more likely to have resulted from fuel starvation.

The estimated fuel used at the commencement of the descent was significantly less than the total fuel carried. However, as the pilot almost certainly became incapacitated relatively early in the flight, he would therefore not have been able to manually alter the fuel state after that point. It was possible to have starved the engine of fuel around the descent point by switching to the right tank and using some or all of the ferry tank (and venting some). However, this would have resulted in a fuel imbalance that was not evident in photos of the aircraft taken shortly before its descent. Given that the estimated fuel used was approximately equal to the usable fuel in the wing tanks, it was more likely that the wing tanks were selected for the duration and this usable fuel was exhausted, leaving the ferry tank full.

The aircraft’s last computed descent rate was below the dive speed for the aircraft, and was therefore indicative of an uncontrolled descent, rather than an in-flight breakup. There was no recorded data of the aircraft’s collision with the water, however the descent profile and wreckage indicated that the collision with water was not survivable.

Increased risk of experiencing hypoxia

In exploring the potential reasons for pilot incapacitation, there were several operational factors identified that increased the pilot’s risk of experiencing hypoxia and being unable to recover.

The pilot elected to fly solo at FL 220 where, without adequate oxygen supply, the time of useful consciousness (TUC) was in the order of 5-6 minutes. This was limited compared to FL 180, for example, where the TUC was two to three times longer.

The pilot had undertaken a hypoxia awareness course and reportedly knew the initial symptoms that presented in himself, which would aid in identifying and mitigating against the risk of hypoxia. However, particularly above FL 180, impairment and incapacitation can occur quickly, with little or no warning, rendering a person unable to take action to recover. The pilot also had a pulse oximeter to monitor blood oxygen saturation, but had been observed on a previous flight to use it intermittently rather than continuously. Given the limited TUC, had the pilot followed a similar regime on this flight, it may have resulted in insufficient time to alert the pilot to decreasing saturation levels. The pilot elected not to have a second pilot on board, as offered by the operator, which would have provided an additional risk control in assisting to identify the signs of hypoxia in each other and enable recovery action, as illustrated by previous occurrences. This would be especially pertinent at altitudes where there is limited TUC.

There was adequate oxygen on board for the flight, however the pilot was probably using a nasal cannula connected to the pilot’s electronic pulse-demand system (EDS) at all flight levels, as indicated by the fact that the Cessna mask was unused by the time the aircraft was in Saipan, despite having flown above FL180. This increased the risk of reduced oxygen-blood saturation levels.

The pilot had also indicated his intention to connect the EDS to the aircraft system without the in-line regulator that was required to ensure the EDS operated within its limits. At FL 220, this had the potential for the pilot to receive inadequate oxygen supply or for the EDS to be rendered inoperative, resulting in higher oxygen consumption than anticipated. However, it is noted that the pilot had the Cessna mask available which, if used with the aircraft system, would have mitigated this risk.

Findings

From the evidence available, the following findings are made with respect to the uncontrolled flight into water involving a Cessna Aircraft Company 208B, registered VH-FAY, that occurred 260 km north-east of Narita International Airport, Japan, on 27 September 2018. These findings should not be read as apportioning blame or liability to any particular organisation or individual.

Contributing factors

• During the cruise between Saipan and New Chitose, the pilot very likely became incapacitated and could no longer operate the aircraft.
• The aircraft’s engine most likely stopped due to fuel starvation from pilot inaction, which resulted in the aircraft entering an uncontrolled descent into the ocean.

Other factors that increased risk

• The pilot was operating alone in the unpressurised aircraft at 22,000 ft and probably not using the oxygen system appropriately, which increased the risk of experiencing hypoxia and being unable to recover.

Context

Pilot information

According to information provided by the aircraft operator, the pilot had accrued over 13,600 hours of aeronautical experience and had conducted more than 200 ferry flights for various companies. The pilot held a valid US First Class Medical Certificate issued on 19 March 2018, with the restriction of vision correction. The 66 year-old pilot was reported by acquaintances to be a non-smoker, in good health for his age, and there was no evidence of any underlying medical conditions. In the nights before FAY departed from Saipan, the pilot had reportedly not slept well, but there was insufficient evidence to determine whether he could have been experiencing a level of fatigue that would affect performance.

The pilot was a Norwegian/American dual citizen with a United States (US) Airline Transport Pilot Licence issued in January 2018. For the ferry flight, a Certificate of Validation was issued by the Civil Aviation Safety Authority (CASA) on 14 September 2018 for a Commercial Pilot Licence (Aeroplane). This included the conditions that the flight ‘must be conducted in accordance with [the aircraft operator’s] operations manual and CASA legislative requirements pertaining to the flight planned route.’ In January 2018, the pilot had ferried another Cessna 208B aircraft, VH-FHY (FHY) from Canada to Perth, WA.

Aircraft information

VH-FAY (FAY) was a Cessna Aircraft Company C208B aircraft manufactured in the US in 2001. At that time, the aircraft was issued with a Certificate of Airworthiness and an associated Airplane Flight Manual.^[5]

The aircraft was fitted with a Honeywell TPE331-12JR engine and a Hartzell Propeller Inc. HC-B4TN-5QL/LT10891NK (De-ice) propeller under a Supplemental Type Certificate (STC). Also under an STC, the aircraft had been fitted with an improved landing gear axle. This increased the maximum landing weight from 3,856 to 4,082 kg and the maximum take-off weight (MTOW) from 3,969 to 4,110 kg. Flight Manual Supplements (FMS) to the Airplane Flight Manual had been issued for each of these modifications.

FAY was fitted with a Garmin GTN 750 GPS. Among other options, the aircraft’s autopilot could be selected to ‘Altitude hold’, and lateral navigation mode could be selected to capture a GPS programmed flight plan.

The aircraft’s last Maintenance Release^[6] was issued on 7 September 2018 following completion of extensive maintenance in preparation for overseas operations. It was valid for 14 months or 230 hours. At issue, the aircraft had 9,269.8 hours total time in service and was approved in the aerial work category and for flight under the instrument flight rules (IFR).^[7]

On the morning of 27 September, prior to departure from Saipan, the aircraft had a total of 9291.7 hours in service.

Survey equipment

The aircraft was usually used for aerial survey work and had been fitted with an electromagnetic (EM) loop system under an Engineering Order^[8] (EO) and an associated FMS had been issued. The system consisted of a copper cable loop suspended around the aircraft and supported by nose, wingtip and tail stingers with a transmitter mounted in the cabin. A receiver (bird) could be towed behind the aircraft on a cable, extended and retracted using a winch. The cable, bird and its cradle, and wingtip stingers had been removed in preparation for the ferry, and the tail stinger had been shortened but was still fitted to the aircraft. EM equipment in the cabin had also been removed, except for some fixed cables.

As the equipment was fitted under an EO, the aircraft had a Special Certificate of Airworthiness (CoA) that limited aircraft operation to the restricted category, for the purpose of aerial surveying.

The FMS for the EM loop limited the aircraft to a maximum operating airspeed of 161 kt and a maximum operating altitude of 20,000 ft, however, most of the equipment had been removed from the aircraft for the ferry. The design holder of the EM loop system advised the ATSB that exceeding the altitude limit had no safety implications in that configuration.

Although the aircraft was permitted to operate in IFR conditions, flight into known icing conditions was prohibited.

Ferry fuel tank and special flight permit

An aircraft that is not operated in accordance with its Type Certificate (and approved Supplementary Type Certificates) is not permitted to operate in foreign countries without a Special Flight Permit (SFP) and the approval of all countries the aircraft flies over or into.

For the ferry, FAY had been fitted with a ferry fuel tank under an engineering order with an associated FMS. The ferry fuel tank fitment meant that the aircraft no longer met the design requirements for the aircraft. Therefore, the aircraft was required to operate under an SFP. An SFP was issued on 6 September 2018 by a person authorised by CASA to issue SFPs, but not to issue overweight approvals.

The aircraft Type Certificate Data Sheet (TCDS) stated that the aircraft was structurally satisfactory for ferry flight up to 130 per cent of the TCDS MTOW (which equates to 11,375 lb or 5,160 kg). However, without overweight approval, the aircraft was required to be operated not above the STC MTOW of 9,062 lb (4,110 kg). The ferry tank FMS stated that ‘the ferry tank may only be able to be partially filled to stay within the aircraft 9062 lbs MTOW.’

Weight and balance

The load sheet indicated that on departure from Saipan, the aircraft’s take-off weight was 4,430 kg and it was loaded within the centre of gravity and structural limits.

Journey logs

The pilot completed journey logs for each flight sector, which included a daily inspection certification, take-off, landing and flight times, and fuel information. The pilot had also recorded engine condition trend monitoring information including the exhaust gas temperature (EGT) and RPM percentage. These are depicted in Table 1.

Table 1: Trend exhaust gas temperature (EGT) and engine RPM

Date	EGT (°C)	RPM (%)
15 September	657	100.5
16 September	658	100.4
17 September	658	100.2

Source: Aircraft operator

Operating the engine at 100.2 to 100.9 per cent was within the normal continuous engine speed allowable range. The FMS for the engine specified the maximum EGT as 650 °C. The engine manufacturer advised that operating at an average EGT of 658 °C relative to 650 °C increased fuel flow by about 5 lb (2.8 L) per hour under the conditions of the accident flight. The aircraft operator’s head of airworthiness and maintenance control advised that no inspection was needed for the recorded temperature exceedances, which could be avoided if the pilot reduced RPM to 100 per cent.

The journey logs were sent to the operator each day, however they were not reviewed during the ferry flight.

Communications

Radio equipment

The aircraft was fitted with the following equipment:

• two VHF radios
• one HF radio
• a Spidertracks GPS connected via a switch on the instrument panel to a hot bus straight to the aircraft battery, so it would continue to operate in case of electrical failure
• one Artex G406-4 emergency locator transmitter fitted with a G shock and remote panel switch
• a satellite phone was installed in the aircraft, docked and with Bluetooth connection
• four personal locator beacons (MT410G) and one Kannad marine sport emergency position indicating radio beacon were on board, all of which needed to be manually activated.

The pilot had a Garmin inReach system from which he could send and receive messages, navigate and track flights and ‘if necessary, trigger an SOS to get emergency help from a 24/7 global monitoring via the 100% global Iridium® satellite network.’

Push to talk

When the company licenced aircraft maintenance engineer (LAME) arrived in Saipan, the pilot advised him that the pilot-side push-to-talk (PTT) button had only been working intermittently and reported that he had been using the co-pilot-side PTT. The LAME cleaned and tested the button, which the pilot then verified was transmitting correctly.

Recorded data

GPS data

The on-board Spidertracks and Garmin GPS devices recorded the aircraft’s position and geometric altitude at 2-minute intervals. The recorded altitude of all sectors flown from Jandakot Airport to the last recorded position is shown in Figure 4. About half of the first leg, from Jandakot to Alice Springs, was flown at FL 210 before descending to FL 130, which was also the cruise altitude on the following sector to Weipa. On the flight from Horn Island to Saipan, having conducted a climb to FL 200, the pilot then made a descent over Papua New Guinea, possibly to avoid weather near Mount Hagen, before climbing and then maintaining FL 200.

The geometric altitude for the occurrence flight from Saipan showed a gradual descent from top of climb at 23,412 ft to the last recorded position at 22,770 ft. This was consistent with the aircraft flying into reducing temperature and barometric pressure. The corresponding radar data recorded pressure altitude at intervals of about 10 seconds and showed a constant altitude at 22,000 ft AMSL.

The pilot sent several messages from the Garmin device after departing Saipan and before the aircraft reached reporting point TEGOD. The last position recorded by the Spidertracks and Garmin devices was at 0626 UTC at FL 220. The aircraft took less than 2 minutes to descend from FL 220 to the ocean and there were no GPS recorded points below that altitude.

Figure 4: Geometric altitude of all flight sectors

Source: Spidertracks analysed by ATSB

Radar and ADS-B data

Japanese air traffic services recorded mode C radar and automatic dependant surveillance broadcast (ADS-B) data from FAY. Secondary surveillance radar (SSR) returns depend on an aircraft transponder’s reply to an interrogation from the ground. In response to a mode C interrogation, the aircraft transmits an encoded return with the aircraft’s selected SSR code and pressure altitude.

Radar data recorded the aircraft’s position (in X and Y coordinates) from the ground radar site and pressure altitude (referenced to 1013 hPa and quantised to the nearest 100 ft) at approximately 10-second intervals. ADS-B data transmitted from FAY’s GPS included the aircraft’s altitude within about 25 ft.

The aircraft was recorded by radar at 22,000 ft at 0627:36 and there were five valid radar returns after that. The data showed that the aircraft descended from 22,000 to the last recorded position of about 11,500 ft in 62 seconds, with an increasing descent rate of up to 22,000 and 23,000 ft/min. That descent rate was less than the dive speed (VD)^[9] for the aircraft (250 kt calibrated airspeed), which corresponded to a vertical descent rate of about 25,300 ft/min.

Recorded audio transmissions

The ATSB obtained recorded audio of the pilot’s transmissions on HF radio to Tokyo Radio and VHF transmissions while tracking across Australia. Comparative analysis of these was carried out with the aim of determining whether the pilot was likely to have been using a nasal cannula and/or affected by hypoxia in the final transmission. Indicators of hypoxia include timing of microphone keying, voice onset time and fundamental frequency range of the pilot’s voice, but these could not be measured due to the noise in the HF channels. The pilot’s communications with Tokyo Radio at TEGOD included some hesitation and a misstated time, but the tempo of the pilot’s next transmission appeared normal and he corrected the time error. The ATSB was unable to make any conclusions based on the recorded audio.

Fuel

The aircraft was fitted with left- and right-wing tanks, which held a combined total of 1,257 L (2,225 lb) of usable fuel. The ferry tank held 924 L (1,635 lb) of usable fuel. The ferry tank was fitted under an engineering order with an associated FMS.

Based on the journey log and fuel dockets, the aircraft ferry and wing tanks were filled in Saipan on 18 September. Although the pilot had taxied the aircraft for maintenance, the fuel was likely close to full on departure. The LAME in Saipan had seen the pilot conduct a pre-flight fuel sample drain from the aircraft and check for contaminants, on the morning prior to departure.

There was no published fuel flow data for flight at FL 220, but the pilot reported an in-flight fuel consumption rate of 163 L/hr (288 lb/hr), which would have been relatively constant for the 6.4 hours in cruise. The aircraft took about 1 hour from taxi to reaching top of climb at 22,000 ft. The operations manual specified a planned fuel burn rate of 450 lb/hr in the climb and the design holder for the engineering orders estimated a taxi and climb fuel consumption of 353 lb. Given the pilot had previously started the aircraft and taxied for maintenance, an estimated fuel consumption for the taxi and climb was 400 lb. Based on these figures, the estimated total fuel used at the last recorded position was 1,241 L (2,196 lb), which was approximately the combined volume of the wing tanks.

Fuel transfer and imbalance

The fuel transfer protocol detailed in the ferry tank FMS was to conduct the take-off and climb to altitude using both aircraft main fuel tanks and, when established in the cruise, turn the left-wing tank selector to off, as fuel in the ferry tank could only be transferred to the right-wing tank. Two electric ferry tank pumps could be selected with different flow rates – 440 lb/hr (low) and 600 lb/hr (high). There was no gauge to indicate fuel quantity remaining in the ferry tank, and the pilot was required to monitor the fuel quantity of the right-wing tank to ensure fuel was transferring as planned and that fuel was not venting overboard.

The FMS specified 200 lb as the maximum permitted fuel imbalance between the left and right tanks. When more severe sideslip is maintained (due to imbalance), the unusable fuel quantity increases. In this occurrence, if the left tank selector was set to off at the top of climb and the right tank was used until empty, it was possible to have a 900 lb imbalance.

In August 1998, the Cessna Aircraft Company conducted flight tests at the request of the US National Transportation Safety Board to determine controllability of the Cessna 208B at various airspeed and lateral fuel imbalance combinations. A Cessna 208B aircraft was flown to a maximum 600 lb imbalance, at airspeeds between 70 and 120 kt at flap settings of 0° and 20°. The maximum control wheel deflection attained was about 28°, of the maximum available 55° control wheel deflection. Control deflection versus lateral imbalance curves were derived from the test. The ATSB extrapolated the data and found that for a 900 lb imbalance, at the aircraft’s likely airspeed, this equated to a control wheel deflection of +14°-17° and right aileron travel of +5-7°.

The aircraft manufacturer (now Textron Aviation) advised the ATSB that the autopilot servo was capable of driving the ailerons to the travel limits of 25° +4°/-0° up and 16° +1°/-0° down in the hangar. This indicated that if the aircraft had a fuel imbalance of 900 lb, there was adequate aileron control to maintain level flight at the aircraft’s likely airspeed, however the autopilot force required to maintain this was not assessed. Photos from the JASDF of FAY in the final 30 minutes of the flight did not show any visible aileron deflection.

Weather

During the last 30 minutes of the flight, the aircraft was observed to be situated between two layers of cloud. The weather conditions that the aircraft likely encountered at FL 220 included strong south-westerly winds averaging about 50 kt, temperature about -15 °C and moderate turbulence. Moderate icing and light rain were present in cloud.

Supplemental oxygen

Because of reduced atmospheric pressure, operation of unpressurised aircraft in Australia above 10,000 ft requires supplemental oxygen.

Flight crew oxygen requirements

Australian Civil Aviation Order (CAO) 20.4 – Provision and use of oxygen and protective breathing equipment, stated:

A flight crew member who is on flight deck duty in an unpressurised aircraft must be provided with, and continuously use, supplemental oxygen at all times during which an aircraft flies above 10 000 feet altitude.

CAO 108.26 – System specification – oxygen systems included that portable oxygen units may be used to meet the crew or passenger breathing requirements and that:

…flight crew members may use nasal cannula manufactured under the name “Oxymizer”, subject to the following conditions… (b) the flight crew members must use the nasal cannula only during private, aerial work, or charter, operations; (c) the aircraft must not operate above 18 000 feet altitude.

Further, it stated that ‘Dispensing units provided in an aircraft operating above flight level 180 must be designed to cover the nose and mouth.’

Aircraft oxygen system

The aircraft was fitted with a 13-port oxygen system with a 3.312 cubic metre (116.95 cubic foot) capacity oxygen cylinder located in the fuselage tail cone. The cylinder had been tested and maintained in accordance with requirements, was within its 15-year life limit and had been filled with aviator breathing oxygen (ABO) prior to the aircraft’s departure from Jandakot.

Oxygen from the cylinder was first reduced to 70 PSI by a pressure regulator and then by two altitude-compensating regulators located between the pressure regulator and oxygen supply lines, which automatically varied the flow of oxygen to the masks with changes in altitude. A remote shut-off valve in the overhead console was used to shut off the supply of oxygen to the system when not in use. A cylinder pressure gauge was located on the overhead console above the pilot’s (and copilot’s) seat.

A microphone-equipped Cessna mask with a vinyl plastic hose and flow indicator was stored under the pilot’s seat. It was observed to be in its packaging (unused) when the aircraft was in Saipan.

On-demand system

The pilot had a battery-operated Mountain High (MH) Pulse-Demand™ Electronic Delivery System (EDS) O2D1 (single-person) model (Figure 5). The EDS unit supplied a measured pulse of oxygen at the beginning of each inhalation and was oxygen-compensating (increasing flow with altitude). The unit had audible and illuminating flow fault and apnoea alarms. A representative from Mountain High advised that although the ceiling of the MH EDS is 25,000 ft, at 22,000 ft it is at the maximum flow rate requirement for oxygen.

Figure 5: Mountain High Pulse-Demand Electronic Delivery System O2D1

Source: Mountain High

Cannula

The pilot preferred to use a nasal cannula for oxygen delivery and he intended to use it for the ferry flight. This was consistent with the supplied oxygen mask being unused before departing Saipan, despite two previous sectors above 18,000 ft. The pilot had also sent a message on the previous sector, indicating that he was using the cannula at 19,000 ft.

The ATSB could not establish the cannula model used for the ferry, however the MH EDS manual stated ‘Use only the supplied MH EDS cannula, as other cannulas may not work properly with the EDS.’ The standard MH nasal cannula (Figure 6) differed from the Oxymizer specified in CAO 108.26, which had a reservoir that stored oxygen during the exhalation then added it to the delivery during inhalation to increase oxygenation. Mountain High advised that the risks of wearing a cannula are:

• it is ineffective if the pilot has nasal congestion, is eating, talking or mouth-breathing
• it can come away from the nose, which would also trigger the apnoea alert.

Figure 6: Mountain High nasal cannula

Source: Mountain High

In-line regulator

The EDS was required to be operated with an oxygen inlet pressure between 16 and 20 PSI, which could be achieved with an in-line regulator (Figure 7). The MH EDS manual indicated that the flow of oxygen would be unnecessarily high between 20-30 PSI. The manual also included the warning that higher pressure ‘will not only compromise the performance of the EDS, but is likely to damage the internal breathing sensor, rendering your EDS unit inoperable.’ MH advised that pressures above 30 PSI would cause the valve to open up and result in the EDS working like a constant flow system. In this situation, the apnoea alert would sound out constantly until the oxygen supply was nearly depleted.

The pilot did not have an in-line regulator for the flight. At altitudes above 17,000 ft, the aircraft’s system provided oxygen at 21.55 ± 2.5 PSI, which was higher than the EDS inlet pressure range. At 20,000 ft, this increased 24.45 ± 2.5 PSI. There was no data for the output pressure at 22,000 ft.

Figure 7: In-line regulator to connect EDS to aircraft oxygen outlet

Source: Mountain High

Mountain High aluminium cylinders

In his briefing before the aircraft departed Jandakot, the chief pilot understood that the pilot intended to plug his EDS directly into the aircraft system without an in-line regulator and was concerned about its effectiveness. Therefore, to ensure the pilot had an independent oxygen supply, the operator provided two MH aluminium (AL682) cylinders fitted with MH regulators, each of which had a maximum volume of 0.68 cubic metres (24.1 cubic feet) and a ‘typical volume’ of 0.63 cubic metres (22.1 cubic feet). The cylinders were filled with ABO and secured behind the copilot’s seat, which the pilot could reach if he slid his seat backwards.

Flight above FL 180

The MH EDS manual advised that pilots operating above 18,000 ft should have a supplementary oxygen cylinder gauge and an emergency backup oxygen system. The manual also provided full cylinder duration figures up to its ceiling of 25,000 ft and cylinder duration graphs from which to calculate usable oxygen for altitudes up to 18,000 ft.

The FAA pilot safety brochure Oxygen equipment: Use in General Aviation Operations stated that the use of cannulas was restricted by US Federal Aviation Regulations to 18,000 ft ‘because of the risk of reducing oxygen-blood saturation levels if one breathes through the mouth or talks too much.’

The aircraft operator’s operations manual approved the use of the MH EDS O2D2 and MH standard aviation nasal cannula up to FL 180, above which pilots were required to use a constant flow mask.

Pulse oximeter

To aid in identifying the symptoms of hypoxia, the pilot had a pulse oximeter, which showed blood oxygen saturation levels based on reading from the finger. On a previous flight the pilot was observed only to use the oximeter intermittently.

The US Federal Aviation Administration (FAA) cautions against relying on pulse oximeters as the sole indicator of hypoxia because by the time the oxygen saturation levels fall, it may result in a level of hypoxia sufficient to cause impairment. Further, the haemoglobin oxygen saturation in blood passing through the finger may not reflect oxygen available to the brain.

Pilot’s oxygen usage

An oxygen management plan from the pilot was not provided to the operator, however there were three sources of oxygen available to the pilot – the aircraft oxygen system and two aluminium cylinders, which were all filled prior to departure from Jandakot. It was not known which source the pilot used and when, but only one cylinder remained behind the copilot’s seat prior to the aircraft departing Saipan. This suggests the pilot had used one cylinder during the flights to Saipan. The pilot had not refilled the aircraft or portable oxygen cylinders since commencing the ferry.

The ATSB estimated whether the pilot had sufficient oxygen to complete the sector. This was based on the time at various altitudes flown for all sectors up to the last recorded aircraft position, and the expected endurance of the available oxygen, filled to typical pressures, according to the manufacturer’s documentation. The estimation was also based on using the available equipment as follows:

• oxygen was used at all altitudes above 10,000 ft
• the nasal cannula was used with the MH cylinders at all flight levels
• the aircraft system was used with a mask or cannula, with or without the EDS.

The pilot’s actual equipment usage may have varied from these assumptions and it is acknowledged that oxygen usage can vary significantly between individuals, especially with on‑demand systems. However, it represented realistic usage scenarios and approximate endurance for the available oxygen. Even when conditions of highest usage were considered, there should have been several hours of oxygen remaining at the completion of the sector to Japan.

Hypoxia

Hypoxia is the absence of an adequate supply of oxygen to the tissues. Hypobaric hypoxia is the most common form in aviation and is associated with breathing air at low barometric pressure. A deficiency in alveolar oxygen exchange due to low oxygen tension (partial pressure) of inspired air leads to inadequate oxygen supply to the blood and reduced oxygen available to the tissues.

Hypoxia can be prevented by pressurising the aircraft cabin or by breathing supplemental oxygen. However, hypoxia can still occur in unpressurised aircraft if, for example, the supply equipment fails and/or does not provide an adequate concentration of oxygen or if the supply is not managed appropriately. In an aviation context, acute hypobaric hypoxia is the ‘most serious single physiological hazard during flight at altitude.’ ^[10]

Signs and symptoms of hypobaric hypoxia include:

• darkening and restriction of the visual field and loss of peripheral vision
• increased heart rate, hyperventilation and light-headedness
• syncope (fainting/unconsciousness, pallor, sweating, nausea and vomiting)
• cyanosis (bluish colouration of the skin, nail beds and mucous membranes)
• impairment of mental performance and neuromuscular control, slowed reaction time
• muscular spasms.

From 15,000 to 20,000 ft ‘there is a loss of critical judgment and willpower…the subject is usually unaware of any deterioration in performance or indeed of the presence of hypoxia; it is this that makes the condition such a potentially dangerous hazard in aviation.’ Above 20,000 ft these symptoms and signs become more pronounced. Involuntary jerks of the arms, loss of consciousness and convulsions occur, and after several minutes, death.

Physical activity, cold, illness and certain drugs increase the onset speed and severity of hypoxia.

US FAA Advisory Circular AC_61-107B Aircraft operations at altitudes above 25,000 feet mean sea level or Mach numbers greater than .75 indicated that while the signs of hypoxia can be detected in an individual by an observer, signs are not a very effective tool for hypoxic individuals to use to recognize hypoxia in themselves. The circular carried the following warning:

A common misconception among pilots is that it is easy to recognize the symptoms of hypoxia and to take corrective action before becoming seriously impaired. While this concept may be appealing in theory, it is both misleading and dangerous for crewmembers.

The Skybrary Operator’s Guide to Human Factors in Aviation Briefing Note defined the fourth, or critical stage of hypoxia as above 18,000 ft. It stated:

Above this altitude, complete incapacitation can occur with little or no warning. All senses fail, and a pilot will become unconscious within a very short period of time. No stimuli such as the radio will be able to help a pilot suffering from hypoxia, especially [rapid onset] fulminant hypoxia, above 5,500 meters (18,000 feet).

A less common form of hypoxia in an aviation context is anaemic hypoxia, caused by carbon monoxide poisoning. This is most commonly associated with piston engine aircraft, in drawing air for cabin heating over a damaged or defective exhaust system. Turbine engines produce up to two orders of magnitude lower carbon monoxide emissions than piston engines and utilise compressor bleed air as opposed to an exhaust heat exchanger. In addition, in 1984, the US National Transportation Safety Board investigated the possible effect of engine oil bleed air contamination on pilot incapacitation, from Garrett TPE 331 engines. It was concluded that such contamination was not likely to occur.

Time of useful consciousness

The FAA circular referenced above (AC_61-107B) defined the time of useful consciousness (TUC) as ‘the period of time from interruption of the oxygen supply, or exposure to an oxygen-poor environment, to the time when an individual is no longer capable of taking proper corrective and protective action.’ There are significant variations in TUC between individuals, and it does not mean that everyone will be capable of performing complex tasks in a challenging environment for the duration.

The circular included a graph showing decreasing TUC with increasing altitude (Figure 8). At 22,000 ft, the TUC was 10 minutes, or 5-6 minutes following rapid decompression. However, it goes on to caution that slow decompression is as dangerous as, or more dangerous than, a rapid decompression, as the resultant hypoxia may be unrecognized by the pilot. The circular also carried the warning: ‘The TUC does not mean the onset of unconsciousness. Impaired performance may be immediate.’

Figure 8: Times of useful consciousness versus altitude

Source: FAA AC 61-107B

Pilot exposure and training for high altitude flying

There was evidence from previous flights that the pilot had some exposure to operating at higher altitudes. The pilot also held a valid US type rating for a Bombardier Challenger aircraft which had a service ceiling above FL 250. Under US Code of Federal Regulations Part 61.31 (g), this required completion of ground theory training including the effects, symptoms and causes of hypoxia and any other high-altitude sickness. The pilot had completed theoretical hypoxia awareness training and reported being aware of his own initial signs of hypoxia.

Altitude-induced decompression sickness

Flying unpressurised aircraft above 18,000 ft can not only induce hypoxia, but also result in altitude-induced decompression sickness (DCS). This is the formation of nitrogen bubbles in different areas of the body due to exposure to reduced barometric pressure. According to the FAA pilot safety brochure on decompression sickness, in most cases of DCS, the bubbles form in the joints, but in 10-15 per cent of cases, neurological manifestations occur. These can include similar symptoms to hypoxia such as confusion, seizures and unconsciousness.

While most cases occur at or above 25,000 ft, the risk of DCS increases with exposure to altitudes above 18,000 ft.

Oversight of the ferry flight

The aircraft operator’s Air Operator Certificate (AOC) was for aerial work and as such, it was not a regulatory requirement to have a formal safety management system. Despite this, the aircraft operator had implemented a health, safety and environmental operating management system (HSE-OMS) that applied to their aviation activities, most of which were low-level survey operations.

FAY was routinely ferried to new surveying locations with its specialised equipment installed. Although ferry flights were classed as private operations, they were normally carried out by company pilots, operating under the AOC. The flights were conducted in accordance with the standard operating procedures and the chief pilot was responsible for operational matters affecting the safety of flying operations. However, following the successful ferry of FHY from Canada to Western Australia by the contract pilot 6 months earlier, the operator elected to re‑engage the contract pilot to ferry FAY to the US.

Risk assessment for the ferry flight

The operator initially conducted a gap analysis to identify any changes that had occurred since the ferry of FHY. It identified several actions, including the need to audit the pilot’s qualifications, conduct a familiarisation flight and briefing on the aircraft and fitments, and for flight monitoring by company staff.

At the planning stage of the FAY ferry, the primary concerns of the operator were around managing:

• long sectors over water – fatigue, lack of alternate landing areas and distance from search and rescue assistance
• single-pilot operation – the operator required their own ferry flights to be conducted with two crewmembers, but the contracted ferry pilot preferred to operate alone

routing – including consideration of security in countries to be overflown.

In accordance with the HSE-OMS, the operator then conducted a risk assessment for the ferry flight. The operator’s risk matrix guidelines included:

The Risk Matrix must be used with good judgment, applying the following recommendations:

- Make use of the experience of several people, with a broad range of experience and backgrounds.

- Within the defined context, the relevant hazards should be identified and documented in the hazard libraries.

- For an identified hazard, the potential consequences (severity) are determined first. A hazard can have a consequence in several categories…

- Risk must be assessed in the context of an activity as hazards manifest themselves differently in different environments or conditions…

The aviation manager reported that he had done the risk assessment based on what the company had experienced in previous ferries and general risk assessment from their operations. The quality assurance manager and flight operations administrator were involved in the assessment process. He also obtained input from the company’s aviation specialist in Canada, who had been involved with the risk assessment for the previous ferry (of FHY). The assessment report was then provided through to their HSE manager.

The HSE manager commented that normally they would get flight operations personnel involved; he, the chief pilot, the aviation manager, a ferry pilot, and a couple of other pilots would form a team. However, the HSE manager had been on vacation during the ferry risk assessment and had not been involved in the process.

The risk assessment identified 32 hazards including one relating to hypoxia:

Unconscious pilot due to oxygen starvation [resulting in] uncontrolled flight into terrain.

It was initially rated as moderate and assessed as unlikely to occur. The nominated control to reduce risk was that there was an oxygen system fitted to the aircraft, with no resultant change to the risk rating (or likelihood). Consideration of specific operational or technical factors that could contribute to hypoxia were not included in the risk assessment. Nor was any form of pilot incapacitation other than hypoxia.

Nearly half of the identified hazards nominated the pilot’s experience (having conducted over 200 ferry flights, including multiple recent Pacific crossings) as one of, or the only risk control. The assessment did not detail whether the pilot had considered the hazards or associated risks, or how he proposed to mitigate them. However, the day before FAY departed Jandakot, the ferry pilot reviewed the risk assessment in conjunction with the operator and suggested additional risks, including road transport, ‘poor decision making due client pressure,’ and access to food and medical support. The chief pilot and a senior company pilot later outlined to the ATSB that they assessed the pilot as being ‘quite organised and competent’, albeit with a clear preference for doing things his own way.

Aircraft operator and pilot agreement

The contract between the pilot and aircraft operator for the ferry detailed the responsibilities of each party, and stipulated how the aircraft was to be operated, including the requirement to adhere to standard operating procedures as specified in the operations manual.

The ‘International Operations’ section of the operations manual included requirements for approvals, permits and documentation associated with travelling to foreign countries as well as flight planning, flight following and emergency equipment. In the agreement between the aircraft operator and the contract pilot, most of these responsibilities had been assigned to the pilot to manage. Of significance, the section stated that ‘In general, the Chief Pilot will manage an overseas operation. Close liaison between the aircrew and the Chief Pilot or their delegate is essential.’

The chief pilot had commenced with the operator on 28 August 2018, two weeks before FAY departed Jandakot on the ferry flight. The chief pilot had previously conducted ferry flights for a different operator, but was inexperienced on the C208 aircraft type. Additionally, because the ferry was assigned to a contract pilot, the chief pilot reported having been informed that he was not required to have involvement in the conduct of the operation, other than briefing the ferry pilot prior to departure.

Along with the risks inherent to the type of operation, the aircraft operator had considered the additional threats posed by financial incentive to complete the ferry as expeditiously and cost-effectively as possible. To this end, the contract included that the pilot would be paid for any days delayed on the ground to reduce pressure to continue the flight in adverse conditions. The pilot was responsible for fuel, oil and other en-route costs such as accommodation and food.

Pre-flight briefing and familiarisation flight

The day before the ferry flight departed from Jandakot, the pilot completed an aircraft familiarisation flight with a senior company pilot experienced in ferry flights, and a briefing with the chief pilot. The familiarisation flight focused on aircraft handling and use of the ferry tank fuel. The chief pilot’s briefing was primarily about the aircraft’s minimum equipment list and safety equipment. These measures had been identified in the gap analysis but not included in the risk assessment.

When the chief pilot briefed the ferry pilot, he was concerned about the pilot’s intention to connect his EDS unit to the aircraft oxygen system without the requisite regulator. To address the concern, he provided the pilot with the two portable oxygen cylinders that were appropriate for use with the pilot’s equipment. The risk assessment did not include the pilot’s oxygen management plan and further risk assessment was not done to assess the effect of the additional oxygen sources.

Flight following

The gap analysis indicated that company operations staff would be responsible for flight following. As required by the contract, the pilot sent the flight plan and journey logs to the operator each day, however they were not reviewed by the operator until after the aircraft disappeared from radar. The logs showed the pilot consistently operated the aircraft engine above the exhaust gas temperature (EGT) limit of 650 °C. Additionally, on the first sector to Alice Springs, the aircraft was flown at 21,000 ft and the final sector from Saipan was at 22,000 ft. Operations staff did not contact the pilot about exceeding the 20,000 ft limit.

Flight plan

The flight plan that the aircraft operator obtained, which was submitted for the planned flight from Saipan to New Chitose Airport, showed the flight planned altitude as FL 250, total estimated elapsed time of 10 hours and 15 minutes and (fuel) endurance of 9 hours and 30 minutes. The discrepancy with the planned flight time exceeding the endurance may have been a transposition error by the pilot, however neither this, the lack of alternates, nor the planned altitude in excess of the 20,000 ft limit was identified or amended prior to departure.

The flight plan obtained by Japan Civil Aviation Bureau was sent from Honolulu at 0507 UTC on 26 September, before the aircraft departed Saipan. That flight plan had a planned cruising level of FL 220 and a total estimated elapsed time of 8 hours and 53 minutes.

Summary of operational oversight

The aircraft operator had processes in place to identify and manage the risks associated with the ferry flight. This included conducting a gap analysis and risk assessment, familiarisation flight and pre-flight briefing, which identified the potential issue with pilot’s intended use of the oxygen system.

The operator also relied on the pilot’s extensive ferry experience to bring level of safety to the ferry flight. However, many of the risk controls relied solely on the pilot’s experience and did not provide any detail on the steps the pilot had taken to manage those risks. The flight also took place outside of the company’s standard procedures and without the normal level of oversight from operations personnel, both of which could have provided an additional opportunity to identify and manage the hazards associated with the ferry flight.

Previous occurrences

ATSB research publication Pilot Incapacitation – Analysis of medical conditions affecting pilots involved in accidents and incidents (2007), reviewed occurrences recorded by the ATSB from 1 January 1975 to 31 March 2006. It identified three cases of hypoxia, which was 3 per cent of the medical/incapacitation events. One of those was a Beech Super King Air aircraft (VH-SKC) near Burketown, Queensland on 4 September 2000. The ATSB investigation report (200003771) assessed that the incapacitation of the pilot and seven passengers was probably due to hypobaric hypoxia due to operating at high cabin altitude and not receiving supplemental oxygen. The report also identified that all the fatal accidents where medical conditions or incapacitation occurred were single-pilot operations where there was no second pilot on board who could assume control of the aircraft and prevent an accident.

The ATSB investigated an incapacitation event involving a Raytheon Aircraft Super King Air 200, VH-OYA, which occurred on 21 June 1999 (199902928). As the aircraft climbed through 10,400 ft, the pilot inadvertently selected the ‘bleed air off’, which prevented the aircraft from pressurising. As the aircraft reached the planned cruising altitude of FL 250, the aircraft deviated from the assigned track and the pilot was observed repeatedly attempting to program the GPS. Shortly afterwards, the pilot lost consciousness. The passenger in the co‑pilot seat took control of the aircraft and conducted an emergency descent, during which the pilot regained consciousness. The investigation findings included that hypobaric training did not provide an effective defence to ensure the pilot (or passengers) would identify the onset of hypoxia.

ATSB investigation AO-2014-134: Flight crew incapacitation involving a Reims F406, VH-EYQ near Emerald Airport, Qld on 1 August 2014. The pilot and navigator were planning to conduct a survey operation at FL 240. The aircraft was unpressurised but fitted with an oxygen system. Having selected the oxygen supply on and donned oxygen masks, passing about FL 180, the pilot noticed the blood saturation level reporting on his oxygen pulse meter was 77 per cent instead of above 90 per cent. In a hypoxic state, the pilot worked to rectify a problem with his oxygen system connection with assistance from the navigator and air traffic control. In this case, the pilot subsequently commented that his hypoxia awareness training had aided his appreciation of his symptoms and effects of hypoxia.

On 23 September 2012, a Metro 3 aircraft, VH-SEF, failed to pressurise on climb (ATSB investigation AO-2012-127). Passing FL 140, the captain started to feel the effects of hypoxia, donned an oxygen mask, and the first officer took over flying the aircraft and conducted an emergency descent to 10,000 ft.

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5. The Airplane Flight Manual (AFM) is produced by the aircraft manufacturer and contains detailed information about operation of the aircraft.
6. Maintenance release: an official document, issued by an authorised person as described in Regulations, which is required to be carried on an aircraft as an ongoing record of its time in service (TIS) and airworthiness status. Subject to conditions, a maintenance release is valid for a set period, nominally 100 hours TIS or 12 months from issue.
7. Instrument flight rules (IFR): a set of regulations that permit the pilot to operate an aircraft in instrument meteorological conditions (IMC), which have much lower weather minimums than visual flight rules (VFR). Procedures and training are significantly more complex as a pilot must demonstrate competency in IMC conditions while controlling the aircraft solely by reference to instruments. IFR-capable aircraft have greater equipment and maintenance requirements.
8. CASA defines an engineering order as the implementing document for a repair or modification and it contains all necessary instructions and references to carry out the task.
9. An aircraft must be designed to be capable of diving to the design dive speed (VD) without flutter, control reversal or buffeting.
10. Gradwell DP, Rainford DJ 2006, Ernsting’s aviation medicine, Edward Arnold (Publishers) Ltd London, Chapter 3.

Safety actions

Whether or not the ATSB identifies safety issues in the course of an investigation, relevant organisations may proactively initiate safety action in order to reduce their safety risk. The ATSB has been advised of the following proactive safety action in response to this occurrence.

Aircraft operator

As a result of this occurrence, the aircraft operator has advised the ATSB that they are taking the following safety actions:

Risk assessment and standard procedures

The aircraft operator reviewed their risk assessment processes and the standard operating procedures for conduct of ferry flights. As a result, they amended the guidance for international ferry operations in their operations manual including: maximum sector length, fuel planning, mandating two-crew operations, oxygen planning, management and training, operating altitude limitations, and use of contract pilots.

Oxygen use guide

The aircraft operator also created an oxygen use guide and a specific risk assessment for positioning (ferry) flights.

The occurrence

What happened

The pilot of a Cessna 208B aircraft, registered VH-FAY (FAY), was contracted to ferry the aircraft from Jandakot Airport, Western Australia (WA), to Greenwood, Mississippi in the United States (US). The pilot planned to fly via the ‘North Pacific Route’ (Figure 1).

At 0146 Coordinated Universal Time (UTC)^[1] on 15 September 2018, the aircraft took off from Jandakot Airport, WA, and landed in Alice Springs, Northern Territory at 0743. After landing, the pilot advised the aircraft operator that the aircraft had a standby alternator fault indication. In response, two company licenced aircraft maintenance engineers went to Alice Springs and changed the alternator control unit, which fixed the problem.

Late the next morning, the aircraft departed Alice Springs for Weipa, Queensland, where the pilot refuelled the aircraft and stayed overnight.

On the morning of 17 September, the pilot conducted a 1-hour flight to Horn Island, Queensland. About an hour later, the aircraft departed Horn Island with the planned destination of Guam, Micronesia. While en route, the pilot sent a message to the aircraft operator advising that he would not land in Guam, but would continue another 218 km (118 NM) to Saipan, Northern Mariana Islands. At 1003, the aircraft landed at Saipan International Airport.

The next morning, the pilot refuelled the aircraft and detected damage to the propeller anti-ice boot. The aircraft was delayed for more than a week while a company engineer travelled to Saipan and replaced the anti-ice boot.

Figure 1: North Pacific Route

Source: Aircraft operator – annotated by ATSB

At 2300 UTC on 26 September, the aircraft departed Saipan, bound for New Chitose Airport, Hokkaido, Japan. Once airborne, the pilot sent a message from his Garmin device, indicating that the weather was clear and that he had an expected flight time of 9.5 hours.

About an hour after departure, the aircraft levelled out at flight level (FL) 220.^[2] Once in the cruise, the pilot sent a message that he was at 22,000 feet, had a tailwind and the weather was clear. This was followed by a message at 0010 that he was at FL 220, with a true airspeed^[3] of 167 kt and fuel flow of 288 lb/hr (163 L/hr).

At 0121, while overhead reporting point TEGOD (Figure 2), the pilot contacted Tokyo Radio flight information service^[4] on HF radio. The pilot was next due to report when the aircraft reached reporting point SAGOP, which the pilot estimated would occur at 0244. GPS recorded track showed that the aircraft passed SAGOP at 0241, but the pilot did not contact Tokyo Radio as expected. At 0249, Tokyo Radio made several attempts to communicate with the pilot on two different HF frequencies, but did not receive a response. Tokyo Radio made further attempts to contact the pilot between 0249 and 0251, and at 0341, 0351 and 0405.

Figure 2: VH-FAY GPS recorded track

Source: Aircraft operator, Google Earth – annotated by ATSB

About 4.5 hours after the pilot’s last communication, two Japan Air Self-Defense Force (JASDF) aircraft intercepted FAY. The pilot did not respond to the intercept in accordance with international intercept protocols, either by rocking the aircraft wings or turning, and the aircraft continued to track at FL 220 on its planned flight route. The JASDF pilots were unable to see into the cockpit to determine whether the pilot was in his seat or whether there was any indication that he was incapacitated. The JASDF pilots flew around FAY for about 30 minutes, until the aircraft descended into cloud.

At 0626 UTC, the aircraft’s GPS tracker stopped reporting, with the last recorded position at FL 220, about 100 km off the Japanese coast and 589 km (318 NM) short of the destination airport. Radar data showed that the aircraft descended rapidly from this point and collided with water approximately 2 minutes later. The Japanese authorities launched a search and rescue mission and, within 2 hours, searchers found the aircraft’s rear passenger door (Figure 3). The search continued until the next day, when a typhoon passed through the area and the search was suspended for two days. After resuming, the search continued until 27 October with no further parts of the aircraft found. The pilot was not located.

Figure 3: Rear passenger door

Source: Aircraft operator

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1. Coordinated Universal Time (UTC): the time zone used for aviation. Local time zones around the world can be expressed as positive or negative offsets from UTC.
2. Flight level (FL): An aircraft’s height above mean sea level when the pressure at sea level is 1013.2 hPa, called pressure altitude. FL 220 equates to 22,000 ft pressure altitude.
3. True airspeed (TAS): the speed of the aircraft relative to the air mass in which it is flying.
4. A flight information service is a form of air traffic service available to aircraft within a flight information region that provides information pertinent to safe and efficient conduct of flight including information on other potentially conflicting traffic.

Sources and submissions

Sources of information

The sources of information during the investigation included the:

• Aircraft operator and maintainer
• Aircraft engineer and design holder
• Japan Transport Safety Board
• Civil Aviation Safety Authority
• Bureau of Meteorology
• Honeywell
• Textron Aviation
• United States National Transportation Safety Board.

References

Campbell RD, Bagshaw M 2002, Human performance and limitations in aviation, Blackwell Science Ltd.

Gradwell DP, Rainford DJ 2006, Ernsting’s aviation medicine, Edward Arnold (Publishers) Ltd London, Chapter 3.

Newman, DG 2004, Flying fast jets: Human factors and performance limitations, CRC Pres LLC.

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 aircraft operator, aircraft maintainer, aircraft insurance assessor, Civil Aviation Safety Authority, Japan Transport Safety Board, US National Transportation Safety Board, Textron Aviation, Honeywell, Thomson Design and Mountain High.

Submissions were received from the Japan Transport Safety Board, Honeywell, aircraft insurance assessor, aircraft operator, Thomson Design and Mountain High. The submissions were reviewed and, where considered appropriate, the text of the report was amended accordingly.

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 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2020 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

Preliminary report published: 15 November 2018

This preliminary report details factual information established in the investigation’s early evidence collection phase and has been prepared to provide timely information to the industry and public. Preliminary reports contain no analysis or findings, which will be detailed in the investigation’s final report. The information contained in this preliminary report is released in accordance with section 25 of the Transport Safety Investigation Act 2003.

What happened

On 7 September 2018, a Yakovlev Aircraft Factories YAK-9UM aircraft, registered VH-YIX (Figure 1), was being operated on a private flight from Latrobe Regional Airport, Victoria. The pilot/owner of the aircraft was the sole occupant.

The aircraft departed the airport at about 1425 Eastern Standard Time.^[1] Recorded air traffic control data showed that the aircraft initially tracked from the airport to the west toward Morwell, climbing to about 2,600 ft and heading north-west near Moe.

Several witnesses described seeing the aircraft conducting aerial manoeuvres to the north of Moe and video footage from a witness showed the aircraft in a steep spiralling dive shortly before it collided with terrain (Figure 2). Other witnesses described seeing the aircraft moments prior to the accident with the engine ‘not revving very loudly’, and ‘making popping noises’. The aircraft was destroyed, and the pilot was fatally injured.

Figure 1: Yakovlev Aircraft Factories YAK-9UM aircraft, registered VH-YIX

Source: Mike Yeo- jetphotos.net

Site and wreckage examination

On-site examination of the wreckage and surrounding ground markings indicated that the aircraft impacted terrain in a right-wing low, nose‑down attitude. The tail of the aircraft separated from the fuselage during the accident sequence. Both wings, the forward fuselage and the cockpit were substantially disrupted and compressed from vertical impact forces. An extensive area surrounding the accident site was contaminated with fuel that was released when the wing tanks ruptured. The degree of propeller damage observed on-site was consistent with the engine producing a level of power at the time of impact.

The ATSB recovered a number of components from the accident site for further examination. The aircraft was not equipped with a flight data recorder or cockpit voice recorder, nor was it required to be.

Figure 2: VH-YIX aerial picture of accident site

Source: ATSB

Ongoing investigation

The investigation is continuing and will include consideration of the:

• pilot’s qualifications, experience and medical history
• recovered aircraft components
• maintenance documentation
• operational documentation
• witness interviews
• electronic devices recovered from the aircraft.

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The information contained in this update is released in accordance with section 25 of the Transport Safety Investigation Act 2003 and is derived from the initial investigation of the occurrence. Readers are cautioned that new evidence will become available as the investigation progresses that will enhance the ATSB's understanding of the accident as outlined in this web update. As such, no analysis or findings are included in this update.

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through: identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2018 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.

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1. Eastern Standard Time (EST): Coordinated Universal Time (UTC) + 10 hours.

Safety summary

What happened

On the afternoon of 17 August 2018, the pilot of a Kawasaki Heavy Industries BK117 helicopter, registered VH-JWB, was conducting fire-bombing operations approximately 9 km west of Ulladulla, New South Wales (NSW).

The pilot was on the third flight for the day and was conducting repeated water bombing of a fire on Plot Road, Woodburn, NSW. On the fifth fire-bombing circuit, at this location, the pilot filled the slung Bambi Bucket (bucket) without incident from a nearby dam and departed towards the fire area. Shortly after, the aircraft diverted off course, the bucket and longline became caught in trees and the helicopter collided with terrain. The pilot was fatally injured and the helicopter was destroyed.

What the ATSB found

The ATSB found that it was likely the pilot suffered an incapacitating medical event. As a result, the pilot unintentionally diverted off track, leading to the bucket becoming tangled in the trees and causing the helicopter to collide with terrain.

The pilot’s post-mortem identified a focus of acute inflammatory change in the heart muscle, a condition known as lymphocytic myocarditis. This condition is capable of causing sudden impairment or complete incapacitation. The pilot is unlikely to have known they suffered from this condition. There are no risk factors for the development of this condition and it cannot be detected by medical screening.

The pilot’s post-mortem also identified coronary heart disease which is also capable of causing sudden impairment and incapacitation. This condition was being effectively managed by medication.

Despite the pilot suffering from these two heart-related conditions, there was insufficient evidence to determine if they contributed to the accident.

The ATSB also determined that the pilot was known to use an over the counter medication for the treatment of hay fever that, although labelled as non‑sedating, was not approved for use while conducting flying operations.

Finally, the pilot did not wear the upper torso restraint correctly. Although on this occasion the accident was unsurvivable, the use of such a shoulder harness restraint generally reduces the likelihood of fatal head injuries.

Safety message

Pilots are reminded that some medical conditions may be undetectable by the normal aviation medical screening process. Pilots should remain vigilant for any medical symptoms which may be the precursor to a more serious medical event.

Pilots should also exercise caution when using over-the-counter medications as their availability does not mean they are automatically safe for use while conducting aviation activities.

The occurrence

On 17 August 2018, a Kawasaki Heavy Industries BK 117 (BK 117),^[1] registered VH-JWB (JWB), was performing aerial work in the Ulladulla area, New South Wales (NSW). The operator had been tasked by the NSW Rural Fire Service (RFS) to support fire-fighting activities in the Bombaderry area, near Nowra, on 15 August 2018, then in the Ulladulla area from the afternoon of 16 August 2018 (Figure 1). The fire-bombing operations were being flown out of the Milton Showground during the day, with the fire-bombing aircraft flown back to Nowra, for overnight parking.

Figure 1 - Accident location

Source: Google Earth, annotated by the ATSB

On the morning of 17 August 2018, JWB departed Nowra for the Milton Showgrounds. The pilot was the sole occupant and conducted a number of flights that day, refuelling from the showground at 1030 Eastern Standard Time^[2]

In the afternoon, JWB and another BK 117, VH-FHB (FHB), were tasked to assist ground‑based fire crews extinguish fires near Plot Road, Milton (Figure 2). Both helicopters were operated with a Bambi Bucket^[3] (bucket) on a longline.^[4] The operation involved flying circuits between the fire area and a nearby dam, where the buckets were re‑filled with water.

Figure 2 - Area of operations

Figure 2 shows the area of operations with circuit direction arrows that are indicative of the average track of JWB during the previous 4 circuits.

Source: Google Earth, annotated by the ATSB

At 1400 the RFS Air Attack co-ordinator conducted an ‘operations normal’ radio call with all aircraft operating in the Ulladulla fire area. The pilot of JWB responded normally and did not report any difficulties.

At about 1407, the pilot of FHB observed JWB’s pilot fill the bucket at the dam before releasing a small quantity of water, consistent with normal operations. JWB then departed the dam in a south‑easterly direction towards the fire.

The pilot then moved FHB over the same dam to fill its bucket. On completion of filling the bucket, the pilot looked for JWB but could not sight the helicopter.

A witness on Plot Road, approximately 100 m east of the accident site, observed JWB tracking in a north-easterly direction, contrary to the established flight pattern. A number of witnesses in the same area then observed the bucket and longline become tangled in trees at the edge of a clearing, and the helicopter collide with terrain (Figure 3). The pilot was fatally injured and the helicopter was destroyed.

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1. The Kawasaki Heavy Industries BK 117 is a twin-engine medium utility–transport helicopter jointly developed and manufactured by Messerschmitt-Bölkow-Blohm of Germany and Kawasaki of Japan.
2. Eastern Standard Time (EST): Coordinated Universal Time (UTC) + 10 hours.
3. A Bambi Bucket, also known as a helicopter bucket, is a specialised bucket suspended on a cable carried by a helicopter to deliver water for aerial firefighting.
4. A longline is a long cable suspended from a hard point on the belly of the aircraft and connected to an external load such as a Bambi Bucket.

Context

Pilot information

General information

The pilot was a New Zealand citizen who had flown in several countries and had experience on numerous helicopter types. They held a valid Commercial Pilots Licence (Helicopter) that was initially issued by the Civil Aviation Authority of New Zealand, in June 1987 and then converted to an Australian licence by the Civil Aviation Safety Authority in October 1998.

The pilot held a Class 1 aviation medical certificate, valid until 5 June 2019, with a restriction requiring reading correction to be available whilst exercising the privileges of the licence.

The pilot’s logbook, combined with the operator’s flying record, showed a total flying experience of approximately 7,750 hours. The pilot had approximately 1,300 hours experience operating the BK117 and in excess of 3,000 hours of longline experience.

The pilot last completed an aerial application rating proficiency check on 9 August 2018, which was valid until 31 August 2020, and included Bambi Bucket operations. The pilot was qualified to conduct helicopter fire operations and had a low-level rating and a sling operations endorsement. The pilot’s logbook contained evidence of fire operations first being conducted in 1997. The pilot obtained an Agricultural Pilot (Helicopter) Rating Grade 2 from the Civil Aviation Safety Authority Australia in March 2003.

Fatigue assessment

The ATSB assessed whether the pilot may have been fatigued at the time of the accident. The pilot’s start times, rest time available, accommodation facilities, environmental factors and workload associated with the task were all reviewed. From the evidence available it was considered unlikely that the pilot was experiencing a level of fatigue known to affect performance.

Meteorological information

Bureau of Meteorology data was available from an automatic weather station located on the coast at Ulladulla, approximately 9 km east of the accident site. One-minute observations at the time of the accident indicated that the wind was from the south-east, between 8‑10 kt.

The other pilot operating in company with JWB at the time of the accident similarly reported the wind to be about 10 kt from the south‑east, which was roughly in the direction of the up-wind leg of the fire-bombing circuit.

Visibility was estimated to be in excess of 5 km by another pilot operating in the same area. Photographs taken shortly after the accident were consistent with that visibility assessment. Other pilots reported that the conditions were good for fire-bombing operations, with no turbulence or visibility issues.

Aircraft information

General

The Kawasaki Heavy Industries BK117 helicopter is a multi-purpose, twin-engine, skidded, medium helicopter with ten seats in the basic configuration.

Airworthiness and maintenance

The helicopter was built in 1994 and operated in Japan before being imported to Australia in 2015. A Certificate of Airworthiness inspection was completed on 24 September 2015. JWB had a current maintenance release, issued on 5 September 2017 and was valid for a period of 300 hours or 12 months, whichever occurred sooner.

The helicopter was maintained in accordance with an approved System of Maintenance. A general maintenance review was conducted on the helicopter’s history since being imported into Australia. This review did not identify any anomalies with the aircraft’s maintenance. At the time of the accident, there were no outstanding defects or maintenance requirements.

Weight and Balance

It was calculated that at the time of the accident the aircraft’s weight and balance were within the operational limits for the helicopter.

Engines

The helicopter was powered by two Lycoming (now Honeywell) LTS101-750B-1 engines. The engines were initially examined on site by the ATSB and also subject to detailed disassembly and technical examination by the manufacturer (see the section titled Wreckage examination).

Hydraulic System

The hydraulic system consists of two independent subsystems of which construction, function and performance are identical.

Bambi Bucket

JWB utilised a Bambi Max bucket that is a lightweight, low‑power draw, quick‑operating multiple drop valve Bambi Bucket. The bucket was attached to the helicopter cargo hook via a 130 ft longline. The pilot controlled the bucket using a push button switch mounted on the cyclic.^[5]

Cargo Hook

JWB was fitted with an Indraero Siren Equipment cargo hook. The hook allows external cargo to be released via a collective^[6] ‑mounted electrical switch. In addition, a foot‑activated manual release lever was located to the right of the pilot’s tail rotor pedal. This lever was used to release cargo in the event of an emergency or failure of the electrical release system.

During the course of the investigation, the ATSB was informed that the pilot sometimes operated with the circuit breaker for the electrical hook release pulled. The operator advised that the company procedure was to fly with the circuit breaker in and the electrical hook switch armed during flight. Additionally, even if the pilot had flown with this circuit breaker pulled, they would still have had the foot‑activated manual release lever available in the event of an emergency.

Operational information

The pilot of FHB commented during interview that each time JWB was overhead the fire‑bombing area there was a substantial level of clearance between the bucket and the trees. This pilot estimated that water was consistently dropped from JWB at about 6‑9 m above the trees.

None of the ground or airborne crews heard any radio transmissions from JWB immediately before the accident. During water bombing operations it is standard practice to make a radio call when leaving the circuit for any reason, to inform other airborne assets of the helicopter’s tracking.

Ground fire-fighting crews were also operating in the immediate area. Those personnel advised that there were no other spot fires in the immediate area. Additionally, the crew of the air attack helicopter reported to the ATSB that when they came into land at the accident location minutes after the accident, they did not see any fire in the area that may have caused JWB to turn away from the circuit.

Fuel

JWB and the other helicopters on task, had all refuelled using Jet A1 fuel from the same onsite tanker based at the Milton Showgrounds. In addition, other helicopters operating in the area were using fuel from the same source and there were no reported issues with fuel quality. Fuel records confirmed the fuel on-board the tanker conformed to the relevant specification.

JWB had refuelled twice from the tanker on the day of the accident with the last refuel of 435 litres conducted approximately 2 hours and 20 minutes prior to the accident. Considering the helicopter’s fuel consumption rate, there was adequate fuel onboard at the time of the accident.

Wreckage and accident site information

Accident site

The accident site was located 9 km west of Ulladulla, New South Wales. The wreckage of JWB was approximately 200 m from the average circuit path and the aircraft final track was estimated to be 90° off the circuit direction (Figure 2).

The main cabin of the helicopter was found inverted in a clearing with the bucket and longline still attached (Figure 3). The bucket and longline were caught in a 22 m tall tree at the edge of the clearing.

Rub marks from the longline were found on the trunk of the tree that the bucket was hanging from. These marks indicated the bucket snagged the tree at least 13 m down from the top of the tree.

In the later part of the circuit the helicopter bucket would normally have a minimum of 6–9 m clearance above the treetops. Taking this into account, and the tree contact 13 m below the canopy, the bucket was at least 19–22 m lower than expected when it snagged the tree and brought the helicopter down.

Figure 3 - Accident site and wreckage

Source: ATSB

The bucket, while suspended from the tree, still contained a large quantity of water. After removal, examination of the bucket showed that the cable required to operate the drop valve had broken at the attaching point to the motor, either during the accident sequence or as the bucket was removed from the tree. However, during post‑accident repairs the main valve was tested and found to be serviceable.

Wreckage examination

The ATSB examined the wreckage and did not identify any pre-existing aircraft defects that may have contributed to the accident sequence. The aircraft and all its components were accounted for at the accident site. There was no evidence of fire.

There was extensive damage to the fuselage with heavy vertical compression evident. One main rotor blade detached, while the other three remained attached to the head, with varying degrees of damage due to contact with the airframe and terrain. The vertical fin, including the tail rotor assembly, intermediate and tail rotor transmissions, fractured from the tail boom at the lower section of the vertical fin. The horizontal and vertical stabilisers had been struck by the main rotor blades multiple times.

Consistent with normal firefighting operations, the pilot door was not fitted at the time of the accident. The cabin doors were forced from their closed position due to impact forces.

All flight controls were observed to be connected at the time of the accident and did not indicate any pre-existing defects. There was no visible damage to the cockpit controls.

Several circuit breakers in the overhead panel were found in the ‘tripped’ position, including the cargo hook, annunciator warn and main rotor RPM warning. However, due to the nature of the accident sequence, these circuit breakers may have tripped due to impact forces.

The serviceability of the cargo hook mechanical release mechanism was verified after disconnecting the cargo hook from the helicopter. This was necessary due to the damage at the hook end of the actuating cable.

The ATSB tested the hook assembly electrically with the use of another BK117 and it was found to be serviceable. The hook was cycled a number of times and released and relatched without any anomalies observed.

Each engine assembly was examined on-site and found to be complete, with no evidence of pre‑accident defects that influenced the accident.

Both engines were removed from the wreckage and shipped to the manufacturer in the United States for detailed examination under the supervision of the United States National Transportation Safety Board.

The disassembly and examination of the engines identified that the type and degree of damage was indicative of both engines rotating and operating normally at the time of impact. No pre‑existing conditions were noted that would have affected their operation.

Examination of the tandem hydraulic unit assembly showed three of the four filter bypass indicators in the ‘popped’ condition. An examination of the filters in each location showed them to be clear of blockages and debris. Consequently, the ‘popped’ indicators were probably impact related. The fluid level indicators for each reservoir showed that both systems had adequate fluid to operate.

While moving the wreckage upright, approximately 100 litres of fuel leaked from JWB. This fuel was clear in appearance and indicated sufficient fuel on-board for use.

Recorded information

The aircraft was not fitted with a flight data recorder or a cockpit voice recorder and neither were required.

A Spidertracks system was installed in the helicopter. Spidertracks provides a real-time flight tracking service using satellite communications. The device reports position and groundspeed at a pre-set time interval, in this case every 2 minutes.

The last recorded point for JWB was at 1408 (Figure 2). At that time, the helicopter was departing the dam, where it had just taken on water, and was heading towards the fire ground. This was consistent with previous circuits.

Medical and pathological informational

Post-mortem examination

The forensic pathologist who conducted the post-mortem examination concluded that the pilot succumbed to injuries sustained during the accident sequence. The examination also identified a widespread area of acute lymphocytic myocarditis, likely of viral origin, and ischaemic (coronary) heart disease. The examining pathologist noted that the myocarditis and/or coronary heart disease found during the post-mortem may have caused sudden incapacitation.

The post-mortem also identified injuries to the pilot’s left arm and both hands. Specialist opinion was that this injury pattern evidence was inconclusive in determining whether the pilot was manipulating the flight controls at the time of the accident.

No witness marks were identified during the examination to indicate the pilot was wearing the available upper torso restraints over the shoulders and the time of the accident.

Finally, toxicological examination identified that a level of 5 per cent carboxyhaemoglobin was present in the pilot’s blood (see the section titled Carbon monoxide below). No other substances were identified that were likely to have impaired the pilot’s performance.

Lymphocytic myocarditis

Lymphocytic myocarditis (myocarditis) is an inflammatory change in the heart muscle, usually caused by an acute viral infection. Acute viral myocarditis can involve a period with mild early symptoms which can be followed by chest pain, heart rhythm abnormalities, heart failure, or sudden cardiac death. Myocarditis may also have a sudden onset with no early mild symptoms. The signs and symptoms of myocarditis vary, depending on the cause of the disease. Common myocarditis signs and symptoms include:

• chest pain
• rapid or abnormal heart rhythms (arrhythmias)
• shortness of breath, at rest or during physical activity
• fluid retention with swelling of the legs, ankles and feet
• fatigue
• other signs and symptoms of a viral infection, such as headache, body aches, joint pain, fever, sore throat and/or diarrhoea

The ATSB engaged two external aviation medicine specialists (consultants A and B), to provide advice regarding the pilot’s health, medications and medical conditions in relation the accident sequence.

The consultants advised that the standard aviation medical examination procedure would not have detected myocarditis. Myocarditis cannot be detected by medical screening, and there are no risk factors for the development of viral myocarditis. The only avenue for prevention is for pilots to self-monitor for any symptoms or signs of illness prior to and during each flight.

Advice was sought from the medical consultants as to the likelihood of the pilot having symptoms of the condition based on the post-mortem report. Consultant A, in conjunction with a cardiologist, reported that the presence of a focus of acute myocarditis in the pilot was a finding ‘likely to have functional significance for the risk of sudden impairment or sudden complete pilot incapacitation.’ Consultant A also stated that viral infections of all kinds are often characterised by quite severe illness developing suddenly, sometimes with early mild symptoms. They also advised that the risk of cardiac arrhythmia due to viral myocarditis and the apparent cessation of pilot control inputs were strongly suggestive of severe and sudden loss of situational awareness and/or loss of consciousness occurring as a result of myocarditis in the final moments of the flight.

Consultant B reported that it was possible the myocarditis was an incidental finding in the post‑mortem and did not cause any symptoms. However, they also advised that it was equally possible the pilot was suffering some medical incapacitation from this condition, however there was no evidence for this prior to the flight.

Coronary heart disease

Coronary heart disease describes a condition where narrowing of the coronary arteries by fatty deposits in the artery walls, or hardening of the arteries, causes a reduction of the blood to the heart muscle, reducing the oxygen supply. If this condition causes a blockage to one of the major arteries supplying blood to the brain, a stroke can occur. Depending on the part of the brain affected, sudden incapacitation and the inability to operate an aircraft may result.

Common symptoms of this disease include:

• chest pain
• dizziness
• shortness of breath
• decreased ability to function normally

The ATSB medical consultants advised that the pilot had undergone an aviation medical examination, including an electrocardiogram, by an aviation medical examiner three months prior to the accident and was found to be fit to fly. In addition, consultant A advised that the pilot’s medical examination and medical certification processes were appropriate and took into account the effective management of cardiovascular risk factors.

Opinion was sought from the consultants on the potential for the condition to have influenced the accident. They commented that coronary artery disease of the level found at post-mortem is often found in healthy people and can be regarded as part of the normal degenerative process of aging. The presence of calcification indicated that the pilot’s heart disease was longstanding and would not necessarily have caused symptoms.

Consultant A also commented that coronary artery narrowing without evidence of inadequate blood supply was reported at post-mortem, but the changes were longstanding and unlikely to have caused symptoms.

Observed behaviour

Several people were interviewed as part of the investigation who had contact with the pilot on the day of the accident and during the days immediately preceding the accident. With one possible exception, all commented that the pilot was generally well and in good spirits.

Following a lunch break on the 16 August, the pilot was observed having difficulty writing down the latitude and longitude of a new task location. The pilot was passed the latitude and longitude three times over the radio and the pilot was observed to write part of the numbers correctly, part incorrectly or just stop writing mid sequence. The latitude and longitude was described as being passed via the radio very clearly.

The observer knew the pilot in a professional capacity and had witnessed the pilot landing, taking off and attending briefings that day and the previous day with no indications the pilot was having any difficulties. The observer made comment that, when the pilot had difficulty writing down the latitude and longitude, nothing in the pilot’s movement, speech or facial expression appeared unusual.

With regard to this observation of apparent impairment, consultant A commented that it may have been associated with myocarditis-related arrythmia or transient ischaemic attack.

Consultant B commented that this apparent episode of confusion was non-specific and while it could be attributed to myocarditis, or the effects of heart disease, it could also have been unrelated.

Medication

During the wreckage examination four prescription medications and one over the counter antihistamine medication were found with the pilot’s possessions. It was confirmed with the pilot’s designated aviation medical examiner (DAME) that all four prescription medications had been taken by the pilot for a number of years and were consistent with their age and health. It was reported by a family member that the pilot did not suffer any side effects from the prescription medications.

Opinion was sought from medical consultant A, in conjunction with an aviation cardiologist, whether the medications could have influenced the accident. The potential for side effects such as sedation and drug interactions, were all considered and excluded by these specialists. The potential for cardiac irregularity due to an interaction between one of the antihypertensive drugs and the antihistamine was also assessed as very unlikely.

The antihistamine medication was for the treatment of hay fever and the pilot’s DAME was not aware of its use. The active ingredient of this medication is listed in the CASA guidance as prohibited. It was reported that the pilot was known to suffer from hay fever and used this medication to treat the symptoms.

Medical opinion regarding the possible sedating side effects of this medication was that, while some people experience sedation when taking this non-sedating antihistamine, this was recognisable on taking the first dose. The pilot was known to have been taking this medication regularly, so any adverse effects on the day of the accident were considered unlikely.

Carbon monoxide

Carbon monoxide (CO) is a colourless, odourless and tasteless gas. It is the by-product of the incomplete combustion of materials containing carbon. The Agency for Toxic Substances and Disease Registry (2012) stated that CO is produced from both human-made and natural sources.

When inhaled, CO is absorbed into the bloodstream where it readily binds with the haemoglobin to form carboxyhaemoglobin (COHb). The binding affinity of CO for haemoglobin is 200-300 times stronger than that for oxygen. Therefore, CO reduces the oxygen carrying capacity of the blood.

An individual’s COHb levels increase as the duration and intensity of the CO exposure increases.

Normal levels of carbon monoxide and effects

There have been a considerable number of studies examining CO exposure, though very few regarding such exposure in helicopters.

Hampson et al. (2007) cited various publications that indicated that there were differing views regarding the correlation between COHb levels and a patient's clinical symptoms.

Further, when comparing the COHb levels detected in individuals, Rathore and Rein (2016) highlighted that it was important to note that ‘both the concentration and length of time are key distinguishing factors. It is vital to note however that individuals exposed to the same source simultaneously can exhibit differing levels of COHb’. Taking this into consideration, when discussing the normal levels of CO contained in an individual’s blood, Consultant B stated that:

Normal levels of carbon monoxide in non-smokers are less than 2-3%. Smokers may have elevated levels around 3-5% or even as high as 9%, depending on number of cigarettes smoked and time since last cigarette smoked.

A police forensic pharmacologist involved in a previous ATSB investigation^[7] reported similar levels, where a non-smoker’s maximum COHb level would be around 5 per cent, while smokers could have levels up to 10 per cent and up to 16 per cent for heavy smokers.

While the research shows some variability in what was considered to be the normal production of CO without occupational exposure, generally less than 3 per cent COHb saturation was considered normal for non-smokers. For smokers, levels up to 10 per cent, or even more were expected.

Recognising the potential for variability, physical symptoms and cognitive effects of CO exposure generally start to occur at COHb levels of around 10 per cent. These include headaches, nausea, dizziness, confusion, and disorientation.

ATSB report AO-2017-118 contains further details on the effects of CO.

Possible sources

Aviation fuels contain carbon so exhaust gasses are a source of carbon monoxide that can potentially enter the cabin during flight. Piston engines produce the highest concentrations of CO, however turbine engines also produce CO (Salazar).

Based on the configuration of the helicopter, with the engines above and behind the cabin as well as the cabin doors closed, it was considered unlikely for significant exhaust gasses to enter the cabin, even with the pilot door removed.

Carbon monoxide is also produced during combustion from bushfires. Studies have been conducted regarding the effect of the smoke on firefighters on the ground, however there is no data in relation to pilots conducting airborne firefighting. One study conducted by Reinhardt and Ottmar (2004) found 5‑10 per cent of firefighters exceeded exposure standards for respiratory irritants, of which carbon monoxide is one, while attending bushfires.

In a study conducted by MacSween et al (2019) it was noted that emissions and subsequent exposure levels were highly variable over the duration of a burn. Carbon monoxide levels present during fire-fighting activities depend on numerous variables, including fuel properties, temperature, moisture, ventilation of the area and proximity to the fire (De Vos, et al, 2008). The pilot was operating at varying altitudes and proximity to the fire and considered to be further from the fire source than ground-based firefighters.

The pilot’s smoking history was also examined. The pilot had been a non-smoker for more than 20 years and it was considered by consultant B to not be a factor in the elevated levels of CO found in the toxicology. 

In summary, the source of the pilot’s slightly elevated CO could not be determined.

Medical opinion

The forensic pathologist, who performed the post-mortem, considered the level of carbon monoxide found in the pilot’s blood was unlikely to have had an effect on the pilot’s ability to fly the helicopter.

Consultant B reviewed the results of the CO testing and the post-mortem report. Taking into account the circumstances of the accident and the CO level found in the pilot’s toxicology, they similarly concluded it was extremely unlikely that the level of CO in the pilot’s blood would have affected their operation of the helicopter.

Survival aspects

Due to the inverted nature of the accident and resulting vertical compression of the fuselage, the accident was not considered survivable.

It was noted, however, that evidence from the first responders showed the upper torso restraint (UTR) was worn incorrectly. The UTR was fastened around the pilot’s waist rather than over the shoulders, meaning the upper torso was unrestrained. A photograph from a previous flight also showed the pilot with the UTR being worn in the same manner as found in the accident flight.

Related occurrences

The ATSB report

examined medical conditions and incapacitation events between 1 January 1975 and 31 March 2006. This report concluded that the majority of pilot incapacitation events do not involve a chronic or pre-existing medical condition. That is, they are largely unforeseeable events, often involving acute illnesses or injury. Of the 10 accidents that resulted in fatalities, all involved single-pilot operations and in half of these, heart conditions were identified as a significant contributing factor.

The ATSB safety education publication Pilot incapacitation occurrences 2010–2014 (AR‑2015‑096) documents recent pilot incapacitation occurrences in high capacity air transport, low capacity air transport, and general aviation to help educate industry about the causes and risks associated with inflight pilot incapacitation. Part of the safety message reminded pilots to assess their fitness prior to flight. Assessment of fitness includes being aware of any illness or external pressures they may be experiencing.

ATSB investigation AO-2015-145: Flight crew incapacitation – Lake Macquarie Airport, NSW, on 15 December 2015

On the morning of 15 December 2015, a SOCATA TBM 700, aircraft, registered VH-YZZ, departed Gold Coast Airport, Queensland for Lake Macquarie Airport, New South Wales. On board were the pilot and one passenger.

The flight to Lake Macquarie was uneventful. However, when the aircraft was just about to land on the runway the pilot started to feel ‘woozy’ and, shortly afterwards, lost consciousness. The aircraft impacted the runway, bounced and impacted the runway a second time before the pilot regained consciousness. The pilot and passenger were not injured during the accident and exited the aircraft. Medical tests and monitoring after the accident found that the loss of consciousness was due to a previously undiagnosed heart condition.

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5. Cyclic: a primary helicopter flight control that is similar to an aircraft control column. Cyclic input tilts the main rotor disc, varying the attitude of the helicopter and hence the lateral direction.
6. Collective: a primary helicopter flight control that simultaneously affects the pitch of all blades of a lifting rotor. Collective input is the main control for vertical velocity.
7. See AO-2017-118 at www.atsb.gov.au.

Findings

ATSB investigation report findings focus on safety factors (that is, events and conditions that increase risk). Safety factors include ‘contributing factors’ and ‘other factors that increased risk’ (that is, factors that did not meet the definition of a contributing factor for this occurrence but were still considered important to include in the report for the purpose of increasing awareness and enhancing safety). In addition, ‘other findings’ may be included to provide important information about topics other than safety factors. These findings should not be read as apportioning blame or liability to any particular organisation or individual.

From the evidence available, the following findings are made with respect to the collision with terrain involving Kawasaki Heavy Industries BK117, VH-JWB, which occurred 9 km west of Ulladulla, New South Wales, on 17 August 2018.

Contributing factors

• While conducting fire-bombing operations, the pilot likely experienced an incapacitating event resulting in deviation off track, entanglement of the bucket in trees and subsequent collision with terrain.

Other factors that increased risk

• The pilot had acute lymphocytic myocarditis which is known to affect heart rhythm and/or blood pressure. This can cause dizziness, impaired consciousness, and incapacitation.
• The pilot had coronary heart disease which is known to reduce the supply of blood to the heart muscle. This can cause chest pain, dizziness, shortness of breath and possible incapacitation.
• The pilot used an over-the-counter medication for the treatment of hay fever that, although labelled as non‑sedating, was not approved for use while conducting flying operations.
• The pilot did not wear the upper torso restraint correctly. Although this accident was unsurvivable, the absence of such a shoulder harness restraint generally increases the likelihood of fatal head injuries.

Safety analysis

Introduction

During daytime fire-bombing operations the aircraft deviated off track without making a radio call, flew too low and caught the bucket in trees resulting in a collision with terrain.

Site and wreckage examination did not identify any defects or anomalies that might have contributed to the accident. The following analysis will focus on possible reasons why the aircraft diverted off track as well as medical and survivability aspects.

Pilot incapacitation

The pilot of JWB was familiar with the area of operations and the conditions on the day, having flown several circuits in the area that afternoon. No weather or mechanical issues were identified during the course of the investigation that could have influenced the accident.

The absence of any communication by the pilot after filling the bucket for the final time was unusual as it was standard practice to make a radio call when leaving the circuit for any reason and was a simple action to perform.

At any time during the flight the pilot had the option to dump the water and/or release the bucket and longline in total from the aircraft hook should circumstances have required it. However, this action was not completed by the pilot. Had the observed flight deviation been the result of the pilot responding to a mechanical issue, dumping the water and/or releasing the bucket would have increased the aircraft performance and made dealing with a mechanical malfunction easier.

If the pilot was attempting an emergency landing, then it would be expected that they would have tracked for one of the nearby suitable landing areas and, depending on the emergency, dumped the water and/or released the bucket and made a radio call. The area the accident occurred in was not a suitable emergency landing site due to the slope of the terrain and surrounding obstacles. In addition, the pilot did not perform any of the expected actions associated with an emergency. Therefore, it was considered unlikely that the pilot was attempting an emergency landing at the time of the accident.

The on-site assessment indicated that JWB was at least 19–22 m lower than expected at the time the bucket caught in the trees. The bucket and longline contacted the tree at least 13 m below the top of the tree. The pilot was aware of terrain having completed four circuits in the area and was on the fifth at the time of the accident. In addition, the pilot had been observed flying with a substantial level of clearance between the bucket and the trees on previous circuits.

With the pilot’s extensive experience working with a longline and at low level, as well as several standard pilot actions that were missing, it is unlikely that the pilot knowingly diverted off track, did not make a radio call and flew significantly lower than was safe resulting in the bucket snagging in the trees and the helicopter colliding with terrain.

In the absence of any mechanical issue, and considering the significant, unannounced tracking and height deviation from the normal operating procedure, the evidence indicated that the pilot probably suffered an incapacitating event. Due to this event the pilot unintentionally diverted off track, was unable to make a radio call and was unable to react to the low altitude of the helicopter. This led to the bucket becoming tangled in the trees and caused the helicopter to collide with terrain.

Possible sources of incapacitation

Although 5 per cent carboxyhaemoglobin was present in the pilot’s blood, the level was considered by medical specialists to be too low to have affected the pilot’s ability to operate the helicopter. Recognising the potential for individual variability, the conclusions of the specialists were consistent with research that indicated about 10 per cent carboxyhaemoglobin was generally required to produce adverse effects. As such, it was considered unlikely that carbon monoxide was the source of pilot incapacitation.

Lymphocytic myocarditis

Both medical consultants engaged by the ATSB agreed that myocarditis may have a sudden onset with no initial mild symptoms. In addition, the signs and symptoms of myocarditis vary depending on the cause of the disease and can include sudden incapacitation.

However, the consultants’ opinion differed in relation to the strength of the link between this specific condition and the outcome of the flight. Consultant A stated that the presence of a focus of acute myocarditis in this pilot was a finding likely to have functional significance for the risk of sudden impairment or sudden complete pilot incapacitation. However, consultant B concluded that it was possible that the pilot was suffering some medical incapacitation from myocarditis or heart disease or other causes that were not identified.

Due to the variation between the specialist conclusions, the ATSB was unable to determine if the effects of myocarditis contributed to the accident.

Coronary heart disease

Both medical consultants commented that the level of coronary heart disease found at the post‑mortem examination was likely typical of a large proportion of the population of similar age to the pilot and was not known to produce symptoms.

The pilot had undergone and passed a Class 1 aviation medical within 3 months prior to accident which included an electrocardiogram.

Due to the pilot’s current effective management of their cardiovascular risk factors and a lack of any other evidence linking this condition to the outcome of the flight, it was considered unlikely to have influenced the accident.

Over the counter medication

During the examination of the wreckage, the ATSB found an over-the-counter antihistamine in the pilot’s possessions, and it was reported that the pilot regularly took this medication for the treatment of hay fever. The Civil Aviation Safety Authority (CASA) provides guidance on medications that are approved, hazardous and prohibited for flight. CASA notes that just because a medication is available over the counter does not mean it is automatically safe for aviation. CASA also recommends that a pilot should always consult their designated aviation medical examiner or CASA about the safe use of medication.

The active ingredient of this medication is listed in the CASA guidance as prohibited in aviation. While the label stated it was non-sedating, it is classed by CASA as a sedating antihistamine. ATSB medical consultant A commented that the sedating effects of this medication would be recognisable on taking the first dose. The pilot had been taking this antihistamine for some time and had not reported any side effects. Therefore, any adverse effect on the day of the accident was considered unlikely.

Upper torso restraint

The pilot was found to have not been wearing the upper torso restraint correctly at the time of the accident. The ATSB medical consultant commented that had this been an un-inverted impact, or an impact with significant longitudinal aircraft deceleration, the absence of the shoulder harness restraint would have increased the likelihood of head injuries, with possible fatal consequences in an otherwise survivable accident.

Sources and submissions

Sources of information

The sources of information during the investigation included the:

• Civil Aviation Safety Authority (CASA)
• operator
• pilot’s and crew of other helicopters airborne in the area
• New South Wales Police Service and Rural Fire Service
• aircraft and engine manufacturers
• maintenance organisation for VH-JWB
• Airservices Australia
• next of kin
• medical consultants
• accident witnesses
• recorded data from Spidertracks

References

Civil Aviation Safety Authority’s aviation medicine guidance, Medication, available from the CASA website.

De Vos, A. Reisen, F. Cook, A. Devine, B & Weinstein, P. (2008). Respiratory Irritants in Australian Bushfire Smoke: Air Toxics Sampling in a Smoke Chamber and During Prescribed Burns. Arch Environ Contam Toxicol (2009). 56:380-388.

Agency for Toxic Substances and Disease Registry. (2012). Toxicological profile for carbon monoxide. Retrieved from https://www.atsdr.cdc.gov/toxprofiles/tp201.pdf

Hampson, N.B. & Hauff, N.M. (2007). Carboxyhemoglobin levels in carbon monoxide poisoning: do they correlate with the clinical picture? The American Journal of Emergency Medicine, 2008(26), 665-669.

MacSween, K. Paton-Walsh,C. Roulston, C. Guerette, E. Edwards, G. Reisen, F. Desservettaz, M. Cameron, M. Young, E & Kubistin, D. (2019). Cumulative Firefighter Exposure to Multiple Toxins Emmitted During Prescribed Burns in Australia. Exposure and Health.

Rathore, O. & Rein, G. (2016). Carbon Monoxide Toxicology: Overview of Altitude Effects on the Uptake and Dissociation of COHb and Oxygen in Human Blood. Retrieved from RFImpactAltitudeCOToxicology.ashx (nfpa.org)

Reinhardt T.E, Ottmar RD (2004) Baseline measurements of smoke exposure among wildland firefighters. J Occup Environ Hyg 1(9):593–606. https://www.tandfonline.com/doi/full/10.1080/15459620490490101

Salazar, G.J. Federal Aviation Administration. (n.d.). Carbon Monoxide: A Deadly Menace. Retrieved from CObroforweb (faa.gov)

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 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2021 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 Australian Transport Safety Bureau was an accredited representative to assist the South African Civil Aviation Authority (SACAA) for their investigation of a General Dynamics Convair 340, registered ZS-BRV, which collided with a building near Wonderboom Airport, South Africa, on 10 July 2018.

During the initial climb, smoke was observed emanating from the left engine. The aircraft subsequently collided with a building. One person on board the aircraft was fatally injured and 18 people were injured. One person on the ground was fatally injured and two people sustained serious injuries.

The SACAA’s Accident and Incident Investigations Division has completed the investigation and the final report is now available. Any enquires relating to the investigation should be directed to the SACAA at: www.caa.co.za