What happened

At 1433 Western Standard Time (WST), on 10 October 2016, a Cessna 210N aircraft, registered VH-UPN (UPN), departed Fitzroy Crossing, Western Australia (WA), for a passenger charter flight to Broome Airport, WA. On board were a pilot and three passengers.

At about 80 NM from Broome, the pilot began a descent from the cruising altitude of 8,500 ft. At 1540, as the aircraft approached 15 NM from Broome, Broome air traffic control (ATC) cleared UPN to conduct a straight-in approach to runway 28. The pilot manoeuvred the aircraft to join a 10 NM final approach to runway 28.

At 1545, passing 5 NM from Broome Airport, the pilot reported they levelled the aircraft at 1,000 ft and conducted the pre-landing checklist in accordance with operator procedures. The pre-landing checklist included selecting the landing gear down and confirming that the landing gear was extended. At about 1547, an individual located under the approach path to runway 28, about 800 m from the runway 28 threshold, observed a Cessna 210 on approach with the landing gear retracted. The individual contacted a member of Broome Airport operations to notify them of the sighting, however, the notification was not received until after the incident.

At 1548, the aircraft touched down on runway 28 with the undercarriage retracted (Figure 1). The aircraft slid along the runway on the underside of the fuselage before stopping. After the aircraft stopped, the pilot contacted ATC to request assistance. The pilot then raised the flaps to provide a clear evacuation path for the passengers. After raising the flaps, the pilot shut the aircraft down, selected fuel off and assisted the passengers with exiting the aircraft.

No persons were injured in the incident and the aircraft sustained minor damage.

Figure 1: UPN after the wheels-up landing

Source: Aircraft operator

Pilot comments

The pilot of UPN provided the following comments:

• The pilot’s roster required them to operate both the fixed landing gear Cessna 206 and the retractable landing gear Cessna 210. They found this difficult and felt that this may have contributed to the landing gear not being selected down prior to landing.
• Prior to departure, the pilot operated a flight from Broome to Fitzroy Crossing. The pilot initially planned to spend 30 minutes at Fitzroy Crossing, however late passengers delayed departure by about 50 minutes. The temperature at Fitzroy Crossing during this time was 41 degrees. The pilot was able to spend about 10 minutes of this time in an air-conditioned caravan, but the rest of the time was spent outside in the heat. A full bottle of water was consumed during this time, however, at the time of departure the pilot reported feeling agitated and slightly dehydrated.
• Prior to landing, as the aircraft passed over the runway threshold, at a height of about 50-100 ft, the pilot reduced engine power to idle. The pilot reported that they did not hear the landing gear unsafe warning horn prior to the landing.
• The pilot may have only completed the pre-landing checklist mentally without actually performing the required actions.
• The pilot felt that ATC personnel should have checked to confirm that the aircraft’s landing gear was extended prior to the aircraft landing.
• While shutting down and securing the aircraft after the incident, the pilot may have selected the landing gear down.
• After exiting the aircraft, the pilot observed the landing gear to be slightly extended and resting on the runway surface.

Operator report

The operator provided a report with the following comments:

• An engineering inspection conducted after the incident found no fault with the landing gear system or landing gear unsafe warning system.
• The damage to the underside of the fuselage and absence of damage to the landing gear indicated the landing gear was fully retracted during the landing.
• After the landing, the propeller pitch control was found approximately 5 cm from the high-RPM position, the fuel selected off, the flaps retracted and the landing gear selector in the down position.
• During straight in approaches, pilots are trained to select landing gear down at 5 NM from the destination airport and to complete the pre-landing checks at 3 NM if not already complete. Once established on final approach, pilots are trained to conduct a final check. This final check includes selecting the propeller pitch control to high-RPM, confirming the undercarriage is selected down and selecting full flaps. The final check is not included in the company operating procedures or aircraft checklists.
• The pilot was wearing a noise cancelling type headset, which may have prevented them from hearing the landing gear unsafe warning horn.
• Broome Airport ATC personnel did not detect that the landing gear had not been extended.

Landing gear warning system

The Cessna 210 is fitted with a landing gear warning system. This system is designed to help prevent a pilot landing with the landing gear retracted. The system will activate when engine power is reduced below about 12 inches of manifold pressure and the landing gear is not down and locked. When activated, the system emits an intermittent tone through the cabin speaker.

Air traffic control procedures

The provider of air traffic services within Australia, Airservices Australia, procedures require a controller to confirm the undercarriage is extended for a civil aircraft when:

• Doubt exists as to whether the aircraft’s landing gear is fully extended.
• Issuing a landing clearance to a general aviation aircraft with retractable undercarriage that has experienced abnormal operation.
• The controller on duty at the time of the incident acted in accordance with ATC procedures. The controller also reported that they checked the aircraft while it was on final approach and did not detect anything unusual.
• Airservices Australia advised that if anything unusual is detected by a controller, the pilot in command will be notified.

Safety analysis

The aircraft was observed on final approach with the landing gear retracted. The pilot commented that after exiting the aircraft the landing gear was found sagging against the runway surface. However, the absence of damage to the nose landing gear doors and the main landing gear legs and tyres indicated that the landing gear was fully retracted when the aircraft landed.

The propeller control was found positioned about 5 cm from the high RPM position required by the final approach check. This was a position consistent with a cruise and approach setting. Therefore, the pre-landing checklist and final approach check were likely not completed resulting in the aircraft landing with the landing gear selected up.

The operator did not have a documented distance from the airport by which the pre-landing checklist should be completed and the final approach check had also not been documented. Such measures increase the chance a pilot will detect incomplete pre-landing checks.

The pilot reported that they did not hear the landing gear warning system prior to the landing. The pilot reduced engine power to idle at a height of about 50-100 ft and glided to the landing. The system should have activated to alert the pilot to the retracted landing gear. The pilot’s noise-cancelling headset may have prevented the landing gear warning tone from being heard.

Findings

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

• The pilot did not complete the pre-landing checklist and the final approach checks resulting in the aircraft landing with the landing gear retracted.
• The operator’s procedures did not define a distance where the pre-landing checks should be completed and the final approach checklist was not documented.
• The landing gear warning system did not alert the pilot to the retracted landing gear, probably as the pilot was wearing a noise-cancelling headset.

Safety action

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

Aircraft Operator

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

Change to operating procedures

The final approach check has been added to the company operating procedures and aircraft checklists and a distance has been added to the pre-landing checklist to specify when the pre-landing checks should be completed.

Pilot training

Company pilots have been reminded to confirm the position of the landing gear during the pre-landing and final approach checks on all company aircraft, regardless landing gear type. This assists in building well established routines for operating aircraft with retractable landing gear.

Safety message

This incident provides a good example of the importance of checklist vigilance. Checklists are designed to ensure that flight crew properly configure the aircraft for any given phase of flight. Regular routine flying can lead to checklists, which are regularly completed, being conducted mentally without the required actions being completed. Vigilance is required to ensure that each checklist is completed correctly and in full.

Pilots should also familiarise themselves with the expected performance of an aircraft for a given power setting, configuration and loading. Extending the landing gear creates an increase in drag which must be balanced by an increase in engine power to maintain a given flight path. When aircraft performance deviates from expectations this may be an indication that aircraft configuration is not correct, such as landing gear remaining retracted when the phase of flight requires it to be extended. This should act as a trigger for the pilot to confirm the configuration of the aircraft.

The Flight Safety Australia article Those who won’t: avoiding gear-up landings includes the following information to assist pilots in avoiding gear up landings:

Most retractable landing gear aeroplanes have landing gear warning systems, but there are normal flight situations where warning systems won’t help.

For instance, most gear warning horns are rigged to sound when the throttle is brought to idle if the gear is not down. But if you use power to touchdown, which many pilots do in windy conditions, or to cushion even a normal landing, the gear warning horn will not sound. In some aeroplanes the gear warning also sounds if the flaps are fully down when the gear is not. This warning only works, however, if you select full flaps. Some pilots don’t use full flaps for every landing, especially in windy conditions, and in these cases the warning will not sound.

In some aeroplanes the gear warning also flashes an annunciator on the instrument panel. Pilots generally focus their attention outside the aeroplane on final approach, however, and may not see a cockpit warning. Conditions that prevent the gear warning horn from sounding will also inhibit the annunciator light.

If you make full-stall landings you get used to hearing the stall warning horn on touchdown. You may not notice the difference between a steady stall warning and the intermittent gear advisory.

Lastly, modern noise-cancelling headsets often prevent the pilot from hearing a warning horn, unless the aeroplane has been modified to pipe the warning through the intercom.

Aviation Short Investigations Bulletin - Issue 56

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 2017 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

On 8 October 2016 the ATSB was advised that the United States National Transportation Safety Board (NTSB) had commenced an investigation into a collision with terrain involving a Fokker DR-1 aircraft, registered N83WR. Initial investigation by the NTSB indicated that the aircraft experienced a partial engine power loss shortly after take-off.

As Australia is the State of Manufacture of the engine, on 11 October 2016 the ATSB requested to be appointed as an accredited representative to the NTSB investigation in accordance with clause 5.18 of Annex 13 to the Convention on International Civil Aviation Aircraft Accident and Incident Investigation. An ATSB investigator was appointed as accredited representative to the NTSB investigation on 12 October 2016. To facilitate support to the NTSB investigation, the ATSB also initiated an investigation under the Australian Transport Safety Investigation Act 2003.

The NTSB determined the probable cause of the accident. Details are available on the NTSB website at https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20161006X61204&key=1

Any enquires relating to the investigation should be directed to the NTSB at : www.ntsb.gov

What happened

On 10 October 2016, a QantasLink Bombardier DHC-8-402, registered VH-LQM, conducted a scheduled passenger flight from Melbourne, Victoria, to Canberra, Australian Capital Territory. On board the aircraft were two flight crew, two cabin crew and 70 passengers. The captain was the pilot flying (PF) and the first officer was the pilot monitoring (PM).^[1]

During the pre-flight briefing at Melbourne Airport, the flight crew noted there was severe turbulence and severe mountain wave turbulence in the area forecast^[2] and SIGMET^[3] for their descent and approach to Canberra. They briefed the cabin crew to be prepared for a quick cabin service and that the seat belt sign would be activated early on the approach due to the forecast turbulence.

The aircraft departed from Melbourne at about 1158 Eastern Daylight-saving Time (EDT) and climbed to a cruising level of FL 210.^[4] The flying conditions were smooth at FL 210 and the flight was issued with the POLLI FOUR ALPHA standard arrival route into Canberra, which started at waypoint POLLI, to the south west of Canberra (Figure 1). The flight crew instructed the cabin crew to prepare the cabin for landing several minutes before the top of descent. However, the flying conditions continued to be smooth during the descent, so the flight crew waited until about FL 130 before activating the seatbelt sign. This was shortly after passing waypoint POLLI.

Between waypoints GOMAN and HONEY, the aircraft descended below FL 110 and the PF reduced the aircraft speed to 210 kt, which is the best speed for turbulence penetration. The PM estimated that the tailwind component reduced from about 70 kt to about 40 kt after the descent below FL 110. At this point, the aircraft was tracking about 060° and passing in and out of cloud over the Brindabella Ranges, which has ridgelines orientated north-south to the south-west of Canberra.

During the descent, the flight crew did not observe any weather radar indications of potential turbulence or visible indications from the shape or movement of the clouds. Between waypoints HONEY and DALEY at about 7,000 ft AMSL, while passing through a small cloud, the aircraft dropped abruptly. The flight crew reported that everything in the flight deck became airborne, the autopilot disengaged, and the PF struck the left side of their head on the overhead air-vent and light, which dislodged their headset. The captain handed control over to the first officer while they refitted their headset and re-established communications, then resumed their flying pilot role and reset the autopilot.

The flight crew continued the approach to land at Canberra without further incident and notified Canberra air traffic control of their severe turbulence encounter on the approach. After the aircraft landed, the PM contacted the cabin crew to check if there were any cabin injures to report. The cabin crew indicated they were uninjured and made a public address to the passengers to check for injuries. The PM then called their company to inform them the aircraft was unserviceable after a severe turbulence incident, and also noticed the captain’s minor injuries.

During the disembarkation of the passengers, the cabin crew informed the first officer that one passenger had hit their head on the overhead baggage locker. The first officer then asked a company ground agent to contact the emergency services so the passenger could be checked. However, the passenger declined treatment. The emergency services arrived and checked the captain. The captain was then advised by the company to visit a doctor where they were diagnosed with minor injuries.

Figure 1: POLLI FOUR ALPHA arrival track of VH-LQM

Source: Google earth, annotated by ATSB

Flight data recorder

The flight data recorder showed that as the aircraft descended through about 7,800 ft the aircraft was in a stable descent maintaining 210 kt and heading 042°. As the aircraft descended through about 7,300 ft the airspeed peaked at about 240 kt and the vertical acceleration oscillated rapidly between a maximum of +1.6G,^[5] minimum of -1G, then maximum of +1.6G before returning to +1G.

Maintenance inspection

After landing, the captain raised a defect report in the maintenance technical log for the severe turbulence encounter. Inspections were then conducted for the severe turbulence assessment. No defects were found, and the aircraft returned to service on 12 October 2016.

Weather forecast

The weather forecast for the Canberra area, issued for the period from 0840 to 2200 EDT on 10 October 2016 included severe turbulence below 12,000 ft and severe mountain wave turbulence above 5,000 ft. The wind was forecast as follows:

• 10,000 ft, from 300° at 60 kt
• 7,000 ft, from 300° at 45 kt
• 5,000 ft, from 290° at 30 kt.

Mountain waves

Mountain waves may be experienced on the lee-side of mountain ranges as smooth undulating airflow or may contain turbulence in the form of breaking waves and rotors (Figure 2). They typically form when the wind direction is close to perpendicular to a ridge line (+/-30°), the wind speed is at least 15 kt^[6] and increases with height, and there is stable air above the crest of the ridge with less stable air above that and a stable layer below the ridge. The formation of clouds on the lee-side may indicate turbulent flying conditions. Further information can be found in the ATSB website safety publications: Mountain wave turbulence.

Figure 2: Mountain wave turbulence

Source: US Federal Aviation Administration

Flight crew harnesses

The aircraft’s flight crew seats are fitted with five point harnesses. The harness consists of a lap belt, a rotary buckle, a crotch strap, two shoulder straps and inertia-reel assembly with emergency locking retractors and cable control assembly (Figure 3). At the time of the turbulence, both flight crewmembers had the five points of their harnesses fitted, but with their shoulder harnesses in the AUTOMATIC position. In the AUTOMATIC position, the shoulder harness inertia-reel permits the occupant to move forward slowly, but locks when the straps are pulled at 1.5G and remains locked until the force is removed. In the MANUAL position, the shoulder straps are locked. The shoulder harness is primarily intended to mitigate forward movement of the torso and head.

The lap belt combined with the crotch strap are the primary means of restraint for turbulence encounters and exposure to negative-G forces. The crotch strap is also referred to as the ‘negative-G strap’ and its purpose is to reduce upward movement of the lap belt during negative-G aircraft motion. The length of the crotch strap should be adjusted such that no slack exists in the strap when the lap belt is properly positioned in the pelvic region. In this position, the crotch strap will resist the upward pull from the shoulder harness in negative-G.

When the aircraft encountered the negative-G turbulence, the captain felt the aircraft drop from underneath them and struck their head on the overhead air-vent and light. The captain and first officer reported that they had their lap belts tightened to ‘firm but comfortable’. The first officer reported that they may have hit their head on the ceiling of the flight deck, but received no injuries. The captain reported that some crotch straps do loosen during flight. The captain also advised that they had set their seat height so their eyes were lined up with height bar markers on the screen. They estimated that provided them with about 20-25 cm head clearance.

Figure 3: Aircraft flight crew harness

Source: Operator

Safety analysis

The flight crew had briefed and prepared the aircraft for flight in forecast severe turbulence.

As the aircraft tracked from waypoint HONEY to DALEY, it entered the lee-side of the Brindabella Ranges, tracking towards the north-east with a strong tailwind component. The wind was forecast to be 30 kt at 5,000 ft, increasing to 45 kt at 7,000 ft and within 30° of perpendicular to the ridgeline, at this location. Therefore, the abrupt encounter with turbulence was probably the result of mountain wave activity.

During the encounter, the flight crew described their movement relative to the aircraft as vertical when the aircraft dropped from underneath them. The primary method of restraint for negative-G is the lap belt supported by the crotch strap. If there is slack in the lap belt, this will permit the body to move up relative to the lap belt, and if there is slack in the crotch strap, this will permit the lap belt to move up if it is pulled upwards by the shoulder harness. The captain reported that the crotch strap can loosen with occupant movement and the aircraft was subject to minor fluctuations in G before the turbulence incident. Therefore, the captain’s injury was probably the result of some measure of slackness in their crotch strap.

Findings

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

• The severe turbulence incident was probably an encounter with mountain wave activity in the lee-side of the Brindabella Ranges.
• The captain was probably insufficiently restrained by their crotch strap to prevent them striking their head during the encounter with turbulence.
• The flight crew were prepared for the risk of an encounter with severe turbulence during the descent and approach to Canberra.

Safety message

This incident highlights the importance of flight crew preparation for entry into an area of forecast turbulence and the importance of ensuring the correct adjustment of all harness straps. The captain planned to activate the seat belt sign early on the descent into Canberra and briefed the cabin crew accordingly. On descent into Canberra, all personnel were seated, the seat belt sign was activated and the aircraft speed reduced to turbulence penetration speed before the encounter with severe turbulence, which minimised the risk of injury to personnel and damage to the aircraft. However, despite the precautions taken by the crew, the captain received minor injuries.

Further information on flight crew harnesses can be found in United States Federal Aviation Administration Advisory Circular 21-34: Shoulder harness – safety belt installations.

Aviation Short Investigations Bulletin - Issue 56

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 2017 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. Pilot Flying (PF) and Pilot Monitoring (PM): procedurally assigned roles with specifically assigned duties at specific stages of a flight. The PF does most of the flying, except in defined circumstances; such as planning for descent, approach and landing. The PM carries out support duties and monitors the PF’s actions and the aircraft’s flight path.
2. Area forecast (ARFOR): routine forecasts for designated areas and amendments when prescribed criteria are satisfied. Australia is subdivided into a number of forecast areas.
3. Significant meteorological information (SIGMET): a weather advisory service that provides the location, extent, expected movement and change in intensity of potentially hazardous (significant) or extreme meteorological conditions that are dangerous to most aircraft, such as thunderstorms or severe turbulence.
4. Flight level: at altitudes above 10,000 ft in Australia, an aircraft’s height above mean sea level is referred to as a flight level (FL). FL 210 equates to 21,000 ft.
5. G load: the nominal value for acceleration due to Earth gravity. In flight, g load represent the combined effects of flight manoeuvring loads and turbulence and can have a positive or negative value.
6. This number varies between references with a lower limit of 15 kt and upper limit of 25 kt cited.

What happened

On 5 October 2016, at about 1600 Western Standard Time (WST), a Boeing 717 (B717) aircraft, registered VH-NXN (NXN), was being operated by Cobham Aviation Services as QantasLink, on a scheduled passenger flight from Paraburdoo Airport to Perth, Western Australia. On board were the captain, first officer, three cabin crewmembers and 115 passengers.

The aircraft had been parked on Bay 2 facing south-west towards the terminal building, and the flight crew planned to depart from runway 24 (Figure 1). The captain commenced taxiing, turning the aircraft around to the right in accordance with the normal taxi procedure. As the aircraft turned, the captain sighted a company B717 aircraft about to land on runway 06. The captain quickly assessed that due to limited apron space at Paraburdoo, they needed to taxi behind a Network Aviation Fokker F28 MK 0100 (F100) aircraft, registered VH-NHF (NHF), which was parked on Bay 1, also facing the terminal, to allow the inbound B717 room to pass and taxi to Bay 2, which they had just vacated.

Figure 1: Paraburdoo Airport showing runways and parking bays

Source: Google earth and aircraft operator – annotated by ATSB

After starting a left turn to taxi behind the F100, the captain was not confident there was sufficient clearance between the two aircraft, and asked the first officer to request a member of ground staff to come out as a ‘wing walker’.

An engineer for Network Aviation, who had been working on the F100, observed NXN taxiing. As NXN deviated from the painted taxi line, the engineer became concerned about the proximity of its left wingtip to the tail of the parked F100. As a result, as NXN taxied forward, the engineer checked the clearance between its wingtip and tail of the F100, and gave the captain the ‘thumbs up’ signal to indicate the aircraft was clear.^[1] The captain assumed therefore that the aircraft was clear and continued taxiing around the back of the F100, then turned the aircraft sharply around to the right (Figure 1 insert). The aim was to leave enough room for the inbound B717 to taxi past, and then continue onto the taxiway once they were clear.

The engineer had expected NXN to taxi towards the runway rather than turning around the back of the F100. The engineer immediately assessed that the horizontal stabilisers of the two aircraft may collide, and tried to signal the captain to stop, but was near the wing of the aircraft and no longer in the captain’s sight. The engineer ran towards the front of the aircraft and waved to the captain to stop. The captain braked heavily. The crew did not feel a collision. Some hours later, it was determined that the horizontal stabiliser of NXN had slid under that of NHF, scraping the surface, and both aircraft sustained minor damage (Figure 2). The passengers and crew of NXN were not injured and no one was on board NHF.

Figure 2: Horizontal stabiliser of NXN under that of NHF

Source: Cobham Aviation Services

Airport facilities

Paraburdoo Airport had one taxiway from the runway to the apron area. There were three parking bays, but only two were suitable for F100 and B717 aircraft. Bay 1 was occupied by the F100, NHF, and NXN had been parked on Bay 2. It was also not possible for a B717 to turn around on the runway except at the thresholds due to pavement restrictions.

Captain comments

Awareness of inbound aircraft

NXN was a few minutes late for their scheduled departure and the inbound B717 arrived several minutes earlier than scheduled. There was no procedure for the aircraft operator to notify pilots of the potential for multiple aircraft (from that company) to be at Paraburdoo at the same time.

The captain (and first officer) of NXN reported that they did not hear the inbound or final calls from the crew of the inbound B717. This may have been because at about the time of the inbound calls, the crew of NXN were resolving loadsheet issues with ground staff.

The captain commented that the ground staff were busy due to the arriving B717, and did not alert the crew of NXN to its imminent arrival. Furthermore, a wing walker was not at the parking bay when NXN started taxiing, which was the normal procedure.

The crew of NXN reported that they were not aware of the arriving B717 until they commenced taxiing. While the inbound aircraft had landed on runway 06, the conditions necessitated a departure from runway 24 for NXN.

Non-normal taxi manoeuvre

The captain reported that they would normally conduct a right turn out of the parking bay and taxi the aircraft directly onto the taxiway leading to the runway. This was what the crew were expecting to do until they sighted the inbound B717, landing in the opposite direction to their planned take-off direction.

When the captain of NXN saw the other B717 about to land on runway 06, they thought they were going to be ‘boxed in’ and formulated a plan in ‘about 10 seconds’ for the two B717s to pass on the apron area. The captain needed to formulate a plan with limited time available due to parking space constraints and noting that B717-size aircraft could only conduct 180° turns at the runway thresholds. The captain assessed that the only way they could pass the incoming B717 was to taxi behind the parked F100.

The captain later realised that they could have taxied to the runway 06 threshold, turned there, and taxied back to the runway 24 threshold, but that would have added about 2 km to their taxi and therefore increased fuel required.

Engineer comments

The engineer gave the ‘thumbs up’ having assessed that the wingtip of NXN would not collide with the (tail of the) F100, but did not expect the captain to continue taxiing around the parked aircraft. The engineer was only trying to ensure the aircraft did not collide having assessed the potential for a collision. They had not intended to act as a ‘wing walker’, did not know what the captain’s intentions were, and had no means of communicating with the captain other than by hand signals.

By the time the engineer assessed that there was insufficient clearance between the horizontal stabilisers of the two aircraft, they were no longer in sight of the captain. The horizontal stabiliser of NXN slid under that of the F100 before the engineer was able to signal the captain to stop.

Ground crew resources

The flight crew could not visually confirm the relative position of the two aircraft due to the limited view from the flight deck. Ground handling agent staff would normally have been available to assist the crew, but their attention had shifted to management of the inbound company aircraft. The first officer was about to request a wing walker from the ground staff, when the engineer appeared and signalled the captain.

The crew would have considered the use of ground vehicles if they had been available, but there was no infrastructure such as a tug or tow bar available at Paraburdoo.

Safety analysis

Due to the inbound aircraft and tarmac constraints, the flight crew assessed that a non-standard taxi manoeuvre was necessary to allow the two B717 aircraft to pass.

There was no wing walker in position on the tarmac to provide the crew with a more timely warning of the proximity of the tail to the tail of the F100, and with whom the crew could communicate to discuss their intentions. The crew were about to request a wing walker because the captain was not certain they would be clear of the F100, when the engineer from another company appeared.

Although the engineer used a standard hand signal, the crew interpreted the ‘thumbs up’ to mean that both the wing tip and tail were clear. The crew had not communicated with the engineer until the engineer gave the signal.

The engineer did not anticipate the sharp right turn of the aircraft after it had apparently passed the F100. The engineer was not in a position to warn the crew about the position of the tail once the sharp right turn had commenced.

Findings

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

• The crew was unaware of the inbound company B717 until after taxi had commenced, then taxied on a non-standard path to accommodate entry of that aircraft onto the tarmac.
• A ground handling agent wing walker was not in place to assist the crew as they taxied.
• The inability to communicate verbally with the non-company engineer resulted in the crew interpreting the engineer’s thumbs up signal as meaning the entire aircraft was clear of the parked aircraft.

Aviation Short Investigations Bulletin - Issue 56

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 2017 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. The NXN company operations manual stated that the thumbs up signal means you are clear to proceed.

What happened

On 22 September 2016, at about 1000 Central Standard Time (CST), a Cessna 210M aircraft, registered VH-SQT (SQT), departed Jabiru Airport, Northern Territory (NT), for a scenic charter flight with the pilot and four passengers on board. The aircraft followed the scenic route ‘Charlie’ in the fly neighbourly agreement (FNA) promulgated by Parks Australia (red line in Figure 1).

Figure 1: Recorded track of VH-SQT and relevant locations

Source: Operator of VH-SQT

About twenty-five minutes after SQT had departed from Jabiru, a Gippsland Aeronautics GA8 aircraft, registered VH-KNB (KNB), departed Jabiru Airport for a scenic charter flight to Cooinda Airport, NT, with the pilot and three passengers on board. Another aircraft from the same company departed immediately behind KNB on the same route. Both aircraft were following route ‘Delta’ in the FNA (yellow line Figure 1). The pilot of KNB broadcast on the common traffic advisory frequency (CTAF) when departing Jabiru. The pilot of SQT heard this call but did not respond. KNB then tracked south via Lightning Dreaming.

After overflying Jim Jim Falls, the pilot of SQT broadcast on the CTAF that they were departing Jim Jim and tracking for Double Falls (about 10 NM north-east) at 1,500 ft, and did not receive a response. The pilots of KNB and the company aircraft did not hear that call.

At about that time, KNB was also at 1,500 ft. The pilot of KNB selected the second radio in the aircraft which was on their company frequency to talk to the pilot of the company aircraft. During that time, the pilot was able to hear broadcasts on both the CTAF and the company frequency except while transmitting. The pilot then spoke to the passengers to provide commentary as they overflew a waterfall and switched back to the primary radio to be able to transmit on the CTAF. As KNB was then at Double Falls which is about 10 NM from Jim Jim Falls, the pilot subsequently reported that they were then about to make a 10-mile inbound call for Jim Jim Falls.

After orbiting Double Falls in a left turn, the pilot of SQT rolled the wings level. Just as they did so, the pilot of SQT sighted a GA8 (KNB) pass within about 20 m horizontally to their left, and about 30 ft above SQT.

The pilot of SQT broadcast on the CTAF asking whether the pilot of the GA8 in the vicinity of Double Falls had heard their departure call from Jim Jim Falls. The pilot of KNB replied that they had not. The pilot of KNB then looked for SQT but did not see the aircraft at any time. When the pilot of SQT heard the callsign and response from the pilot of KNB, they realised that this company often had multiple aircraft operating in company and immediately looked for and sighted the other company aircraft at the same altitude about 300 m away.

Operator comments

The operator of SQT commented that they believe there is a need for a separate radio frequency for the Jabiru area. On the existing CTAF, pilots can hear broadcasts from Batchelor to the west and Numbulwar to the east. Most of those broadcasts are not relevant to pilots operating in the Jabiru area but increase radio congestion and can potentially lead to over-transmissions.

Fly neighbourly agreement scenic routes

Following consultation with local operators through the Northern Territory Regional Airspace and Procedures Advisory Committees, the FNA routes were agreed on and published by Parks Australia in 2010 and published in the En Route Supplement Australia (ERSA). The FNA was due to be reviewed by Parks Australia in 2015 and the review is expected to be conducted later this year (2016).

The FNA routes were designed to avoid sensitive areas and for ‘park amenity, tourism experience and nature conservation’. The routes were not intended to provide aircraft separation, but they are mandatory routes for aircraft operating below 2,500 ft (unless operating in accordance with a special permit).

SQT and KNB were following different routes published in the FNA with both aircraft at 1,500 ft on reciprocal tracks. SQT was following route Charlie and KNB was following route Delta from Jabiru to Cooinda.

This was the first of the flights on the wet season routes this year. There had been significant rain in the previous fortnight that closed the roads to the falls. Pilots from the two aircraft operators had identified the possible conflict of opposite-direction aircraft the previous year and had agreed that they would broadcast departing via Lightning Dreaming when tracking south to alert pilots of aircraft tracking north on the reciprocal track. However, when the pilot of KNB broadcast on the CTAF that they were departing Jabiru, the broadcast did not include that they were tracking via Lightning Dreaming.

The pilot of KNB commented that they could have a similar procedure as they use for flights to Oenpelli: they track to Oenpelli at 1,500 ft and back to Jabiru at 2,000 ft to ensure separation between aircraft travelling in opposite directions. The pilot of SQT commented that having a plan and agreed routes and specified altitudes would help to prevent similar occurrences.

Safety analysis

The pilot of the north tracking SQT broadcast when departing Jim Jim Falls for Double Falls but the pilot of the south tracking KNB did not hear that transmission, possibly due to communicating with the other company pilot on the other radio. Therefore, they were not aware of SQT until the pilot of SQT broadcast after the near collision. The pilot of KNB also commented that the CTAF was busy as it covered a large area, and this may have contributed to the missed communication.

The pilot of KNB did not include ‘via Lightning Dreaming’ in their departure broadcast when departing Jabiru Aerodrome. While the broadcast ‘via Lightning Dreaming’ was not mandatory, it may have alerted the pilot of SQT to the two aircraft tracking in the opposite direction on reciprocal routes at the same altitude.

Findings

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

• The aircraft were at the same altitude on reciprocal tracks on published FNA scenic routes and came into close proximity because the pilots were not aware of each other due to ineffective communication.

Safety action

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

Operator of VH-KNB

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

• A notice to pilots was distributed reminding them of the importance of effective radio usage as an aid to situational awareness in high traffic areas. Pilots were instructed to review and acknowledge Civil Aviation Advisory Publication (CAAP) 166-2(1) as it contains relevant information on alerted see and avoid radio techniques.
• Pilots of aircraft tracking towards Double Falls from the north are required to make an additional radio broadcast.
• All other scenic routes will be examined for potential conflict points and effectiveness of standard radio calls.
• They will discuss the incident with the operator of SQT and determine ways to reduce the risk of a similar incident occurring.
• Investigate alteration of flight routes and altitudes flown in conjunction with other operators.
• Investigate and review potential implementation of a dedicated radio frequency in scenic flight locations in Kakadu National Park.

Safety message

This incident highlights the importance of effective risk analysis by operators. An effective risk analysis of the FNA routes would probably have highlighted the potential for opposite-direction traffic. This may have led to risk management strategies such as implementation of vertical separation planning, radio broadcasts, and consideration of having a dedicated frequency.

A search for other traffic is eight times more effective when a radio is used in combination with a visual lookout than when no radio is used. In areas outside controlled airspace, it is the pilot’s responsibility to maintain separation with other aircraft. For this, it is important that pilots use both alerted and un-alerted see-and-avoid principles.

Pilots are encouraged to ‘err on the side of caution’ when considering when to make broadcasts and whether specific frequencies should be monitored, particularly noting the fundamental importance of communication in the effective application of the principles of see-and-avoid. The ATSB report Limitations of the See-and-Avoid Principle outlines the major factors that limit the effectiveness of un-alerted see-and-avoid.

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 2016 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.

What happened

On 27 September 2016, a Pulse Aerospace Vapor 55^[1] remotely piloted aircraft (RPA), was operating a test flight at Lighthouse Beach, Ballina, New South Wales (Figure 1).

Figure 1: Photo of a (different) Vapor 55 RPA

Source: www.skylineuav.com.au

According to telemetry data^[2] recorded on the remotely piloted aircraft system’s ground control station (GCS), at about 0910 Eastern Standard Time (EST), the RPA lifted off from its start position in front of the surf clubhouse (Figure 2). About 30 seconds later, when the RPA was at an altitude of about 36 ft, it entered ‘manual’ flight mode. The RPA then tracked according to manual inputs from the pilot for about 7 minutes, at which time (when at 124 ft altitude) the data-link signal was lost. Thirty seconds later, the RPA entered the ‘home’ flight mode, and commenced tracking to the programmed home position at an altitude of 154 ft. The last position of the RPA recorded by the GCS was about 165 m NNE of the start position, and about 4 km SE of Ballina/Byron Gateway Airport.

In the home flight mode, the RPA did not respond to the flight control inputs made by the pilot and the pilot subsequently lost sight of the RPA. The RPA was not found despite an extensive search.

Figure 2: Recorded RPA track

Source: Google earth and remotely piloted aircraft system operator, annotated by ATSB

Mission planning

Prior to the flight, the pilot’s preparation for the planned mission involved using Google earth on a computer (not the GCS), and selecting a north-western and a south-eastern reference point. These markers defined an outer rectangle, within which the flight was to take place (Figure 3).

Figure 3: Planned operating area defined using NW and SE markers

Source: Google earth, annotated by ATSB

The pilot then transferred an image of the google earth map for the area onto the GCS using a USB stick, and uploaded it to create the ‘Lighthouse Beach’ mission. To georeference^[3] the image, the pilot then overlaid the markers in the image with a point icon on the controller, and entered the latitude and longitude of two positions into the dialogue box on the GCS. The north-western GCS marker is visible in the top left corner of Figure 4, but the latitude and longitude values visible are image text only.

Once the image had been georeferenced, the pilot then used the graphical interface to place the start and home icons and any intervening waypoints for the planned mission (Figure 4).

Figure 4: Image uploaded onto GCS with planned mission overlaid

Source: Remotely piloted aircraft system operator, annotated by ATSB

Incorrect georeference

The remote pilot reported that both they and an observer checked each waypoint before the flight, verifying latitude, longitude, altitude and height. However, the GCS data shows that during the planning phase, while the north-western marker was correctly assigned, the south-eastern marker was incorrectly assigned to a georeference point with a latitude in the northern hemisphere. This resulted in all of the waypoints and home location being incorrect, as they were created by dragging icons on the georeferenced image. Waypoints 2, 3, 6 and 7 had latitudes in the northern hemisphere, and the home position was assigned to 17.222395° S and 153.591582° E. That location was in the Coral Sea Islands about 1,200 km north of the start position (Figure 5).

Figure 5: Actual location of home position and select waypoints from the GCS

Source: Remotely pilot aircraft system operator, Google earth

The RPA’s start position was correct as it was obtained using the RPA’s GPS. As the aircraft entered manual mode after take-off and the pilot did not initiate the automatic mode to fly the programmed mission, it was only when the RPA lost the datalink, stopped responding to the pilot’s manual control inputs and commenced tracking for the programmed home position, that it left the planned operating area. The pilot can also manually give the ‘home’ command. In all home and automatic modes, the handheld controller is ignored unless the pilot gives the ‘manual’ command via the GCS application and manually takes control of the RPA.

The GCS has a ‘flight plan’ tab, which shows the planned distance and time (among other items) for the mission, which could have alerted the pilot to the incorrect latitude references. However, a check of the flight plan tab had not been included in the operator’s pre-flight procedures. In addition, the flight plan tab includes a measure tool that can be used to check that the map size is correct.

The manufacturer advised that the following steps are included in their pre-flight procedure specified in the aircraft flight manual:

• verify flight plans
• verify lost communication home waypoint.

The operator stated that there was no further detail of the verification process in the manual.

The default hemisphere was north (N) in the GCS for entering positions. The manufacturer stated that there was no feature that would change the default (to south (S)). The manufacturer assessed that changing the default could lead to issues with the conduct of appropriate pre-flight checks.

The operator reported that information about the default setting to north was not provided in the Aircraft Flight Manual.

Loss of data-link signal

The RPA system commands homing after 10 seconds of data link loss when in automatic mode and 2 seconds if in manual mode. In this incident, as the RPA was in manual mode, it initiated homing after 2 seconds.

The cause of the lost signal could not be determined. The operator thought that there may have been interference from a media outside broadcast unit located about 30 m from the GCS. However, the media personnel advised the operator that they were using a satellite communications link and therefore should not cause interference.

Appropriate action

The manufacturer advised that once the aircraft commenced tracking to an incorrect home location, the appropriate action would have been to use the ‘hold’ or ‘manual’ command so that the joystick flight control could be used.

The remote pilot advised that they had attempted to use the ‘hold’ command, as they were shown in their training, but the RPA did not respond. No evidence of this was recorded in the GCS data.

Safety analysis

Although the pilot reported having completed the pre-flight preparations and associated checks, the data stored on the GCS showed that the incorrect (northern) hemisphere was assigned to the south-eastern georeference marker at the time the map image was created. This led to the home position being assigned a location in the Coral Sea Islands, so when the RPA lost signal and tracked for home, it headed north and was not recovered. The same outcome would have occurred if the pilot had selected the RPA to fly home, even with a continuous data-link signal. While all of the intermediate waypoints were also incorrect, as the GCS remained in manual mode, the RPA did not attempt to track to any of those waypoints.

Findings

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

• The south-eastern point used to georeference the image on the ground control station map was selected to a northern hemisphere latitude, which resulted in incorrect waypoints and home position for the mission.
• The RPA data-link signal to the ground control station was lost, so it commenced tracking to the programmed home position, which was in the Coral Sea Islands at a latitude 17.22° S, about 1,200 km north of the start position.

Safety action

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

Manufacturer

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

• Audit of training curriculum to ensure that pilots understand how to verify GPS coordinates, interpret their values and signs. The training course will continue to train pilots on the tools available to them within, and outside of the GCS software.
• Share this incident with operator trainers so that new operators can learn from the events of this incident.
• Continued education and outreach discussions with RPAS operators pertaining to decreased mishap rates through training and currency policies.

Remotely piloted aircraft system operator

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

• The pre-launch checklists have been modified to include additional and enhanced procedures to verify data input and flight plans.
• Investigate the fitting of either GPS or cellular tracking devices to remotely piloted aircraft.
• Update the risk assessment form to include location of external broadcast stations such as television outside broadcast units.
• Brief all company pilots on the event for safety and education purposes.
• Continue liaison with the manufacturer.

Safety message

Incorrect reference data can have potentially serious consequences in remotely piloted and manned aircraft. It is imperative that remotely piloted aircraft systems incorporate means of minimising the opportunity for errors to occur and also for detecting and correcting errors that do occur.

The careful application of operational controls and procedures, underpinned by robust risk assessment, will become increasingly important as relevant technologies develop further and new RPA applications continue to emerge. RPA operators should expect data loss events and prepare for these appropriately.

The ATSB SafetyWatch highlights the broad safety concerns that come out of our investigation findings and from the occurrence data reported to us by industry. One of the safety concerns relates to data input errors.

Aviation Short Investigations Bulletin - Issue 56

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 2017 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. The Pulse Aerospace Vapor 55 is a helicopter, gross weight 25 kg, with a maximum cruise endurance of 60 minutes, controlled via a laptop computer operating the ground control station and flight controls (joystick).
2. The telemetry data is sent from the RPA to the ground station and stored.
3. Georeferencing means to assign a physical location (coordinates) with a position in an image.

What happened

On 23 September 2016, a Network Aviation Fokker F28 MK 100 aircraft, registered VH-NHY, departed Newman Airport, Western Australia (WA), on flight 1623 to Perth Airport, WA. On board were two flight crew, three cabin crew and 97 passengers.

About 550 km north of Perth, at 1048 Western Standard Time (WST), the flight crew were alerted to a caution for low quantity in hydraulic system 1. The flight crew completed the checklist actions, which included selecting the hydraulic system 1 pumps off. The loss of hydraulic system 1 results in the loss of the following systems:

• normal landing gear extension (alternate gravity landing gear extension required)
• normal flap extension (electric power used to extend flaps)
• nose-wheel steering, speed brakes and thrust reversers.

The flight crew notified air traffic control (ATC) of the fault and discussed the implications of the failure. Without nose-wheel steering, they planned to land the aircraft on runway 21 at Perth Airport and roll through to the end of the runway, where a pre-positioned tug would connect to the aircraft and tow it to the allocated gate for passenger disembarkation. Rather than use the engines for electrical power and air-conditioning during the aircraft tow, the captain elected to start the auxiliary power unit (APU) during the approach. The APU would then supply air for the air-conditioning system after landing and electrical power after the engines were shut down.

The flight crew discussed the issue with the cabin crew manager (CCM), advised them of the implications of the fault and their plan for when the aircraft landed. The flight crew subsequently advised the company of their plan and made a PAN^[1] call to ATC with their landing intentions. They started the APU and then configured the aircraft early for the approach and landing. The aircraft landed without further incident and rolled through to the end of runway 21.

Figure 1: Emergency evacuation of VH-NHY

Source: Airport operator

At the end of runway 21, the flight crew could not see a tug waiting for the aircraft, so they used differential braking to turn the aircraft off the runway and onto the taxiway before stopping. The first officer completed the after landing checks, while the captain called the CCM to explain the situation and discuss the public address requirements. While on the interphone to the captain, the CCM reported that there were fumes present in the cabin. The captain turned the APU bleed off, to prevent the APU supplying air to the cabin. However, the CCM then reported that the fumes in the cabin were getting worse. Consequently, the captain suspected the fumes could be from the engines and in consultation with the CCM they elected to conduct an emergency evacuation (Figure 1).

The flight crew started the emergency evacuation checklist and the captain called for the evacuation over the public address system. The cabin crew opened the two front doors and the four over-wing emergency exits were removed by the passengers (Figure 2). The forward left door (L1) slide did not automatically inflate when the slide deployed, so the CCM manually inflated the slide. When the CCM checked on the forward right door (R1) slide they observed that it was not deployed and the cabin crewmember was blocking the exit. The passengers evacuated through the forward left door and the over-wing exits.

The flight crew completed the emergency evacuation checklist and the captain directed the first officer to take the fire extinguisher from the flight deck and join the passengers. The captain then left the flight deck about one minute after the evacuation started with the passenger manifest. They noted there were only a couple of passengers left in the cabin, and the CCM was directing one of them to leave their baggage behind and evacuate. The captain waited for all personnel to leave the aircraft, completed an inspection of the cabin and then exited the aircraft to join the passengers, provide them with support and liaise with the authorities. During the emergency evacuation, three passengers received minor injuries.

Figure 2: Aircraft emergency evacuation routes

Source: Operator, annotated by ATSB

Maintenance findings

The maintenance organisation found the number 1 engine thrust reverser selector valve (see Thrust reverser selector valves), located in the left outboard APU (see Auxiliary power unit) compartment (zone 313), leaked hydraulic fluid from a damaged O‑ring (Figure 3). Further inspection found the APU and air-conditioning system were contaminated with hydraulic fluid.

A gap between the APU intake door actuator rod cut-outs was identified as the path for contaminated air to enter the APU inlet. When the APU inlet door is open inflight, air is scooped into the inlet creating an area of high pressure. However, when the aircraft is on the ground with the APU running, the APU inlet becomes an area of lower pressure as the APU is now ‘sucking’ air into the inlet.

Figure 3: Location of APU and thrust reverser selector valves

Source: Operator, annotated by ATSB

The R1 door was found by the maintenance organisation to be in the ‘DISARM’ position (‘MANUAL’ mode; see Cabin emergency exits) and an inspection was conducted on the slide and associated mechanism. No defects were found. Inspections of the L1 door slide could not identify a reason for this slide to not inflate automatically.

Auxiliary power unit

The APU is located in the aft fuselage, behind the rear pressure bulkhead. It supplies pneumatic power for starting of the main engines and air-conditioning on the ground, and electrical power if the number 1 and 2 engine driven generators are not supplying power. If the APU is started while airborne, it will not supply air to the air-conditioning system until the ground-flight logic switch detects the aircraft is on the ground.

Thrust reverser selector valves

The thrust reverser selector valves supply hydraulic fluid under pressure to the thrust reverser actuators. Hydraulic fluid for the thrust reverser selector valves is supplied by hydraulic system 1. The number 1 selector valve (left side) is installed in the rear aircraft fuselage behind the pressure bulkhead in zone 313 adjacent to the APU compartment.

Cabin emergency exits

The aircraft is fitted with one forward left side passenger door with an inflatable slide, one forward right side door with an inflatable slide, and four over-wing escape hatches. The inflatable slides will deploy automatically when the door is opened from the inside with the door selector set to ‘AUTOMATIC’. If the slides do not inflate in the automatic mode, then the red inflation handle on the right side of the slide pack must be pulled for inflation. When disarmed (‘MANUAL’ mode), the slide is not attached to the aircraft doorway and remains inside the door assembly when the door is opened. Once the door is opened in the MANUAL mode, there is no way to deploy the slide.

Previous incidents

A search of the ATSB database revealed two previous incidents of fumes entering the cabin on Fokker F28 aircraft from the same operator following a hydraulic leak when the APU was supplying air to the air-conditioning system:

• 21 November 2014: VH-NHM cabin fumes present on pre-departure. Source of hydraulic leak found to be from the horizontal stabiliser actuator.
• 21 January 2016: VH-NHP hydraulic system 1 low quantity inflight followed by cabin fumes during aircraft tow to the gate. Tail section was found wet internally with hydraulic fluid. Speed brake actuator found with damaged O-ring, which was identified as the source of the leak.

In response to the incident in 2014, the operator contacted the aircraft manufacturer to propose the design of a seal located at the entry point of the APU air intake. This would mitigate the potential for contamination of the air-conditioning system following a hydraulic leak. The manufacturer considered the proposal plausible and reasonable, but elected not to initiate action as this was their first reported occurrence.

Following the latest incident, and in light of the two previous incidents, the aircraft manufacturer considered if an amendment to emergency procedures was required to warn flight crew of the potential risk of a fumes incident from operation of the APU following a hydraulic leak. The manufacturer decided this was not supported based upon the following service experience:

The majority of the reported hydraulic leaks are not located in the tail section. Hydraulic fumes entered the cabin or flight deck in less than 1% of the non-tail origin events. The APU was not implicated in the non-tail origin events.

A change to the hydraulic quantity low emergency procedure was considered, but their review indicated that only a small percentage of tail origin hydraulic leak events that could potentially lead to fumes were associated with a hydraulic quantity alert.

Safety analysis

The hydraulic leak was the result of a failure of an O-ring in the number 1 thrust reverser selector valve. The checklist actions resulted in switching off the pumps supplying the number 1 hydraulic system with the loss of the associated systems, which included the nose wheel steering. The loss of nose wheel steering necessitated a tow to the gate by a tug after landing. The captain elected to start the APU inflight so that it would be available to supply air for the air-conditioning system after landing and electrical power after the engines were shutdown. However, unknown to the flight crew, the location of the hydraulic leak relative to the APU air intake, and a gap between the APU intake door actuator rod cut-outs, resulted in the contamination of the air-conditioning system. This occurred when the ground-flight logic switch detected the aircraft was on the ground and the APU started to act as a source of air supply for the air-conditioning system.

After the fumes were detected in the cabin, the first action by the captain was to switch off the air supply from the APU. Following this action, the air for the air-conditioning system was supplied by the engines. However, by this stage various parts of the air-conditioning system were contaminated with hydraulic fluid. Therefore, fumes continued to enter the cabin through the air-conditioning system.

During the emergency evacuation, the R1 door slide did not deploy. The maintenance inspection found the R1 door was disarmed and no fault was found with the door operating mechanism. Therefore, it is likely that during the emergency evacuation procedure the cabin crewmember at the R1 door reverted to previous experience and disarmed the door prior to opening it, which prevented the slide from automatically deploying.

Findings

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

• A damaged O-ring in the left engine thrust reverser selector valve resulted in a hydraulic leak.
• Hydraulic fluid, or vapour, entered the APU air intake through a gap between the APU intake door actuator rod cut-outs.
• The cabin fumes were the result of the APU supplying air contaminated with hydraulic fluid to the air-conditioning system after the ground-flight logic switch detected the aircraft on the ground, which resulted in the contamination of the air-conditioning system.
• The R1 door slide did not deploy automatically because the door was disarmed when it was opened.

Safety action

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

Operator

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

Air quality checks

Following the replacement of parts contaminated with hydraulic fluid and cleaning of the APU area and air-conditioning system, the operator and their maintenance organisation conducted air quality checks on the aircraft before return to service.

Flying operations advisory bulletin

The operator’s flight operations department issued flying operations advisory bulletin (FOAB) 031/16: Fumes ingestion by the APU. The bulletin advises flight crew of the potential for ingesting fumes through the APU intake in the event that the APU is operating with a hydraulic leak in the tail section of the aircraft.

Human factors review

The human factors review of the incident was conducted for learning points and future training considerations.

Maintenance program

Changes to the aircraft maintenance program have been introduced to proactively identify potential issues, such as detailed visual inspections within areas which may lead to potential air quality issues.

Safety message

This incident highlights the importance of training and procedures, and the need for organisations to educate their workforce about safety incidents. The flight crew on board NHY were confronted with two consecutive emergencies. They responded to each situation in accordance with their training and procedures, which resulted in everyone safely evacuating the aircraft with only minor injuries reported.

Further information about the risk of fumes can be found in ATSB research report

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1. PAN PAN: an internationally recognised radio call announcing an urgency condition which concerns the safety of an aircraft or its occupants but where the flight crew does not require immediate assistance.

Aviation Short Investigations Bulletin - Issue 57

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 2017 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.

Discontinuation notice

Published 8 January 2020

Section 21 (2) of the Transport Safety Investigation Act 2003 (TSI Act) empowers the Australian Transport Safety Bureau (ATSB) to discontinue an investigation into a transport safety matter at any time. Section 21 (3) of the TSI Act requires the ATSB to publish a statement setting out the reasons for discontinuing an investigation.

On 23 September 2016, the ATSB commenced an investigation into the descent below segment minimum safe altitude involving Airbus A330-343X, 9M-XXI, near Gold Coast Airport, Queensland, on 11 September 2016.

The aircraft was cleared to conduct a RNAV-Z (GNSS) instrument approach to runway 14 (Figure 1) at Gold Coast Airport in visual meteorological conditions. During the approach, the aircraft was observed to descend below the 1,700 ft segment minimum safe altitude between the instrument approach’s intermediate fix (OOLNI) and a position 2.5 NM from the final approach fix (OOLNF).

Figure 1: The Gold Coast RNAV-Z (GNSS) Rwy 14 non-precision instrument approach

Source: Jeppesen

The ATSB interviewed the flight crew and also examined the operator’s policies and procedures for the conduct of the RNAV-Z type approach. The flight crew reported that they had briefed the approach. That briefing included identification that the 2.5 NM position was not included in the aircraft’s navigation data base and that there was a segment minimum safe altitude requirement associated with this position.

The approach was flown using the autoflight system in a managed mode. As the aircraft approached the OOLNI, the aircraft was in a shallow descent and the flight crew commenced configuring the aircraft for landing (Figure 2). At OOLNI the aircraft was fully configured for landing and at a speed of 150 kt. As the aircraft passed through OOLNI, the autopilot pitched the aircraft down. The flight crew attempted to recover the speed through the application of speed brake. However this, coupled with the aircraft pitching down, resulted in an increased rate of descent, which in turn led to the penetration of the 1,700 ft segment minimum safe altitude. The aircraft subsequently returned to its targeted flight profile by OOLNF and continued the approach for landing.

Figure 2: The instrument approach vertical profile

Source: Jeppesen

The Flight Crew Training Manual (FCTM) for the A330 stated that the activation of the approach phase will initiate a deceleration towards the approach speed or a speed constraint inserted into the Final Descent Point (FDP). The FDP was defined as the capture point of the final descent segment coded into the navigation data base. The two approach techniques for the final descent segment were the decelerated approach and the early stabilised approach.

For the decelerated approach, the vertical flight profile was managed by the aircraft’s Flight Management Guidance and Envelope System (FMGES) using data in the aircraft’s navigation database, modified as required by the flight crew. This was described as using the autoflight system in a ‘managed mode’. The deceleration profile targeted having the aircraft at 1,000 ft above the landing point, in the landing configuration and at the approach speed. This profile generally equated to the aircraft being configured with the first stage of flap/slat and at the required speed at the FDP. In the discussion on the use of a managed vertical profile for a non-precision approach, the FCTM noted that for some non-precision approaches, ‘the final approach flies an “idle descent” segment from one altitude constraint to another, followed by a level segment’.

The early stabilised approach technique required the flight crew to have the aircraft in the landing configuration and at the approach speed at the FDP. The final descent segment was then flown using a selected vertical profile mode, such as the Flight Path Angle (FPA) mode.

The ATSB obtained the navigation database used by the FMGES for the RNAV-Z (GNSS) Rwy 14 approach. That database included initial (OOLNI) and final (OOLNF) approach fixes and their associated altitude limits, but did not include the point 2.5 NM from OOLNF and its associated segment minimum safe altitude limitation. The database also included a three degree approach profile from the OOLNF, but did not include a three degree profile before OOLNF.

The operator’s investigation into the occurrence identified that, as the three degree glide path started at OOLNF, the aircraft would conduct a stepped descent between OOLNI and OOLNF. The stepped approach profile was reflected by the autopilot pitching the aircraft down as it passed through OOLNI. In a stepped approach, on passing an altitude constrained position (such as OOLNI), the autopilot will fly an idle descent to the new altitude constraint and then fly level until the completion of that segment. The operator also noted that the step down limitation between OOLNI and OOLNF was not coded into the database due to specific coding rules. In response to the occurrence event, the operator custom coded the RNAV-Z (GNSS) Rwy 14 approach to include a 3 degree slope from OOLNI. The operator also issued a memorandum to all pilots requiring all non-precision approaches into Australia to be conducted using the selected vertical guidance Flight Path Angle mode only. Based on this information, the ATSB determined that it was unlikely that further ATSB investigation would identify any systemic safety issues. Consequently, the ATSB has discontinued this investigation.

Section 21 (2) of the Transport Safety Investigation Act 2003 (TSI Act) empowers the Australian Transport Safety Bureau (ATSB) to discontinue an investigation into a transport safety matter at any time. Section 21 (3) of the TSI Act requires the ATSB to publish a statement setting out the reasons for discontinuing an investigation.

At about 1000 Western Standard Time on 10 September 2016, an Air Tractor AT-502 aircraft, registered VH‑ULV, was conducting aerial agricultural spraying activities at Salmon Gums, near Esperance, West Australia. During a turn at about 200 ft above the ground, the pilot lost control and the aircraft collided with terrain. The aircraft was substantially damaged and the pilot sustained serious injuries.

Figure 1: VH-ULV showing damage

Preliminary enquiries by the ATSB suggest that the accident was attributable to pilot actions. The ATSB considered it was very unlikely that further investigation would uncover any systemic safety issues. The ATSB has discontinued the investigation.

What happened

On 22 September 2016, at 1608 Eastern Standard Time (EST), a Jetstar Airways Airbus A320-232 aircraft, registered VH-VFY (VFY) (Figure 1), operated a scheduled passenger flight, JQ956, from Sydney, New South Wales, to Cairns, Queensland (Qld).

At about 1630, as the aircraft climbed, the cabin manager (CM) was on the flight deck. A cabin crewmember notified the flight crew and the CM of an unusual odour in the cabin. The CM left the flight deck to conduct an inspection of the cabin and detected a burnt electrical type odour present in rows 1 to 5. They notified the flight crew and continued to inspect the cabin.

At 1632, the flight crew received an ENG 2 OIL FILTER CLOG message on the electronic centralised aircraft monitor (ECAM) system. This message indicated that the engine management system had detected an increase in pressure across the engine oil filter of more than 12 psi. However, the increase in pressure did not reach the required level of 20 psi for the engine management system to automatically bypass the engine oil filter. The ENG 2 OIL FILTER CLOG message was an advisory message and did not require any flight crew actions. During this time, all engine indications were within normal limits.

At about the same time, the CM returned to the flight deck having conducted an inspection of the full cabin and reported that the unusual odour had dissipated. The cabin manager returned to the cabin to monitor the situation. The flight crew continued the climb and levelled the aircraft at the planned cruising level of flight level (FL) 340.^[1] The flight crew then reviewed the engine oil system and, anticipating a possible diversion, obtained the weather for Brisbane Airport, Qld.

Figure 1: Airbus A320 VFY

Source: Tony Coles

At 1644 the cabin crew detected smoke entering the cabin and the CM instructed the cabin crew to stop the cabin service and stow the cabin carts. The CM reported to the flight crew, via the aircraft interphone, that light smoke was entering the full length of the cabin through the overhead air conditioning vents. As the flight crew received this report, they detected a vibration and unusual noise from the right engine and the aircraft yawed^[2] to the right. At the same time, the ECAM displayed the message ENG 2 FAIL.

The flight crew then commenced the engine failure checklist and switched on the seat belt sign in the cabin. While conducting the checklist, they observed a small amount of smoke coming from the cockpit ventilation system. At the same time, the cabin crew observed heavy smoke entering the cabin through the overhead air-conditioning vents. The flight crew donned oxygen masks, and in accordance with the engine failure checklist, depressed the right engine fire button. This action isolated the engine systems from the rest of the aircraft and shortly after, the flight crew observed that the smoke had dissipated and they removed their oxygen masks.

The smoke also dissipated in the cabin after a short time.

After completing the checklist, the flight crew diverted the aircraft to Brisbane, declared a PAN^[3] to air traffic control and began a descent to FL200. During the descent, the flight crew briefed the CM and advised them of the engine failure and the diversion.

The flight proceeded to Brisbane Airport and landed at about 1720 without further incident. No persons were injured in the incident and the aircraft was not damaged.

Captain comments

The captain provided the following comments:

The aircraft communications addressing and reporting system (ACARS) notified the company operations centre as the incident unfolded. The information provided by ACARS to the operations centre enabled the company to prepare for the aircraft arrival at Brisbane and reduced the workload of the flight crew during the diversion.

Training previously undertaken by the captain and first officer was very similar to the incident. This enabled the first officer to anticipate many of the captain’s needs and ensured the flight crew worked well as a team during the incident.

The captain had not met any member of the cabin crew prior to this flight. The captain commented that the procedures in place and training that all crewmembers had undertaken ensured that the flight crew worked very effectively with the cabin crew to manage the incident and diversion.

The flight crew calculated that the landing would be at a weight above the aircraft maximum landing weight^[4]and assessed that the emergency facilities and long runway at Brisbane provided the most suitable airport for diversion.

Donning the oxygen masks greatly hindered communications with the first officer, performance as a team improved markedly after removal of the oxygen masks.

Cabin manager comments

The cabin manager provided the following comments:

Due to training requirements, there were five cabin crew on board the flight, rather than the usual four. The additional crew member assisted in the management of the passengers and cabin during the incident and diversion.

The cabin crew training and procedures were very effective. Two of the cabin crew on the flight were new to the role, however they were able to effectively carry out their tasks during the incident and diversion.

Engineering examination

After the incident, the engine manufacturer, International Aero Engines (IAE), conducted an engineering examination of the engine and detected that the number 3 bearing had failed. A detailed examination of the bearing was conducted. IAE reported that due to secondary damage, the engineering examination could not determine the cause of the number three bearing failure.

IAE reported that the ball material was found to be compliant with manufacturing quality requirements.

Airworthiness directives

In 2007, the Civil Aviation Safety Authority released airworthiness directive (AD) AD/V2500/3 relating to failures of the number 3 bearing within IAE V2500 series engines within a specified range of serial numbers.

This airworthiness directive did not apply to the IAE V2527-A5 engine fitted to VFY, as the serial number (V17515) for the engine was outside the specified range, however the AD contained the following information:

The issuing of this AD is to prevent failure of the number three bearing, which could result in an in-flight shutdown and smoke in the cockpit and cabin. The smoke is a result of oil escaping from the bearing compartment due to a fracture of the numberthree bearing race.

The United States Federal Aviation Administration released AD 2016-25-11, which has an effective date of 20 January 2017. This AD also required inspections and corrective actions for damage to the number 3 bearing. The FAA released this AD after the premature failure of number 3 bearings resulted in nine in-flight engine shutdowns. The AD does not apply to the engine fitted on VFY, as the serial number was once again outside of the specified range.

Applicability of airworthiness directives

The ADs were introduced after failures of the number three bearing led to the discovery of microstructural defects in some bearing components, introduced during the manufacturing process. Following this discovery, the engine manufacturer reviewed manufacturing records to determine the extent of engines with affected bearings.

The engines with the highest level of number 3 bearing material defects, and therefore the highest risk of failure, were included in the original AD. Engines determined to have a lesser level of defects required additional inspections and/or were subject to reduced service life. The second AD was introduced to increase the number of engines affected.

IAE advised that V2500 series engine-powered A320 aircraft currently achieve an in-flight shut down rate of 0.00136 per 1,000 flight hours. This is less than IAE’s target in flight shut down rate, of 0.02 per 1,000 flight hours.^[5] IAE investigates the cause of each in-flight shut down and takes corrective actions with the goal of maintaining the target in-flight shut down rate. IAE will continue to monitor the performance of the bearings and will adjust the fleet management plan if required.

The engine manufacturer and the United States Federal Aviation Administration advised that no further actions were planned beyond the current ADs.

The Civil Aviation Safety Authority (CASA) commented that they are monitoring the situation and awaiting reports from the aircraft operator and engine manufacturer.

Safety analysis

The initial odour detected by the cabin crewmembers during the aircraft’s climb, along with the ENG 2 OIL FILTER CLOG ECAM message, likely resulted from the early stages of the number 3 bearing failure. The later instance of smoke in the cabin and flight deck occurred as the bearing failed. The failure of the number 3 bearing resulted in a complete power loss from the right engine.

Findings

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

The right engine number 3 bearing failed, resulting in engine power loss and led to smoke entering the flight deck and cabin.

Safety message

This incident highlights the importance of effective crew management techniques, training and robust emergency procedures. The captain had not met any of the other flight and cabin crewmembers prior to the flight. In addition to this, some cabin crewmembers were new to the role. Despite this, the emergency procedures and training undertaken by the crewmembers ensured that they were able to fulfil their roles and work effectively as a team to manage a difficult situation safely and efficiently.

Aviation Short Investigations Bulletin - Issue 59

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 2017 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. At altitudes above 10,000 ft in Australia, an aircraft’s height above mean sea level is referred to as a flight level. Flight level 340 represents 34,000 ft.
2. Yaw is the motion of an aircraft about its vertical or normal axis.
3. PAN is an internationally recognised radio call announcing an urgency condition which concerns the safety of an aircraft or its occupants but where the flight crew does not require immediate assistance.
4. Maximum landing weight is the maximum gross weight an aircraft may land at due to structural or performance limitations. Landing at a weight above this weight may require a structural inspection of the aircraft.
5. 0.02 per 1,000 flight hours is the rate required for an engine and airframe combination to achieve the acceptable in-flight shut rate for 180 min extended operations.