On 21 December 2016, an Airbus A320 aircraft, registered VH-VGI (VGI), and operated by Jetstar Airways, was being loaded at Melbourne Airport, Victoria, prior to operating flight JQ792 to Sunshine Coast, Queensland (Figure 1).
Figure 1: Image of VH-VGI
Source: Medhi Nazrinia
At 0500 Australian Eastern Daylight-savings Time (AEDT),[1] a clerk at a freight organisation commenced their shift at the organisation’s Melbourne Airport freight office. As it was the week before Christmas, it was a very busy week.
The organisation had recently introduced a new system for processing freight, however, a decision was made to revert to the old system due to the amount of freight to be entered and issues which had been experienced with the new system the previous day.
A team of clerks organised which items of freight are loaded on specific unit loading devices (ULDs)[2] to be sent to aircraft for flights around Australia. They then send the loading information to the airline. The team was short one person and the person who had been called in to cover the shift was starting work at 0700. Until that person commenced their shift, the clerk was responsible for completing two freight uplift roles. This meant the clerk was responsible for processing freight on all narrow-body[3] flights the organisation sent freight to, departing from Melbourne.
Because of the large amount of freight to be processed, including a large amount of freight from the previous night still waiting to be processed, there was a lot of radio traffic between leading hands organising the loading/unloading of the ULDs, and the clerk regarding the management of the freight. The clerk spent about 20 minutes on the radio, and then processed freight for 9 or 10 flights over the next half an hour.
During this time, the clerk identified two pieces of freight, which needed to be sent to the Sunshine Coast. These two pieces of freight contained flowers and meat and weighed a total of 93 kg. Rather than informing the leading hand, the clerk put the freight in a ULD and wrote that ULD number on the same page they had previously written the details of a different ULD, one that was to be sent to Adelaide. The clerk then went to the office and the ULD was processed as going to the Sunshine Coast; however, when the clerk returned to the ULD with the freight, they inadvertently put the Sunshine Coast freight card on the ULD destined for Adelaide. This ULD contained medical goods with a gross weight of 245 kg. This ULD was subsequently loaded on the flight to the Sunshine Coast.
The clerk realised an error was made when the ULD, which was intended to go to Adelaide, could not be located. The clerk, who commenced work at 0700, noticed the same number ULD on the Sunshine Coast flight paperwork and they then found the ULD that was supposed to go to the Sunshine Coast. That ULD was put on the next flight to the Sunshine Coast.
Once the error was detected, the clerk rang the Sunshine Coast freight office. They were informed the incorrect container had been sent and provided them with details of the freight so the ULD could be sent back to Melbourne, then to Adelaide.
The aircraft remained within all weight and balance limits during the flight.
Freight processing systems
The organisation was transitioning between an old and new processing system. In the old processing system, all information (such as weight and container number) was entered into an office computer. It was also the clerks’ responsibility for planning which flight the freight will go on and they rely on information from the leading hands for the freight details. The clerk would write the number of the container down, enter the number via the computer and then they would itemise the freight that had gone into the container. The cards itemising the freight would be printed out and attached to the container.
In the new system, information is entered on tablet computers. It is the customer’s responsibility to book their freight onto flights themselves. Staff are on the floor and are required to put the piece of freight in a container and enter the details on the tablet in succession. The system has built in checks, which would not allow the same number ULD to be used. This new system had been introduced about a week prior to the incident, but due to technical issues, they had reverted to using the old system.
Clerk’s comments
The clerk provided the following comments:
They felt very busy. Within the first hour, they would have processed freight for about 9 to 10 flights, which was double the usual workload.
They had to process all flights to Adelaide, Brisbane, Canberra, Alice Springs, and Townsville, as well as all other narrow-body flights. Normally this role would be divided between two clerks.
If there is a person unable to work their shift, they try to find a replacement. They had done so in this case, but the replacement could not start until 0700.
Normally at Christmas time, they would have extra staff rostered, but that year they did not.
On the day, they felt under stress due to the busy time of year.
Previous occurrences
A search of the ATSB’s occurrence database found occurrences relating to incorrect loading information being processed, particularly when staff were under high workload:
On 16 May 2010, an Embraer ERJ 190 aircraft was operated on a positioning flight from Adelaide, South Australia to Brisbane, Queensland (ATSB investigation AO-2010-034). The pilot-in-command reported that the load and trim sheet for the aircraft was inaccurate due to items being counted twice. It was found that the error occurred when the airport movements coordinator inadvertently selected the incorrect aircraft configuration in the company’s computerised load and trim system during a high workload time.
On 8 September 2016, an Airbus A320 aircraft was being loaded at Sydney Airport, New South Wales to Brisbane, Queensland (ATSB investigation AO-2016-119). The leading hand received the deadload weight statement (DWS) and checked the containers. The third container number (1483) did not match the number listed on the DWS (4183), nor the container card (4183). The leading hand assumed that the freight handler had inadvertently transposed the numbers incorrectly and amended the card and DWS with 1483 and continued loading. When the aircraft was unloaded in Brisbane, it was found that the incorrect container (1483) was delivered and was nearly 650kg heavier than container 4183. The loading procedure if the DWS is incorrect, is that the container must not be loaded onto the aircraft. The leading hand noted that the short turnaround time and the flight was the last one of the day led to procedures being bypassed.
Safety analysis
An incorrect ULD, weighing 245 kg was loaded onto VGI operating the Sunshine Coast flight, where the load sheet recorded a ULD of 93 kg. The error occurred when the clerk put the freight card for the Sunshine Coast flight on the Adelaide ULD, and the card for the Adelaide flight on the Sunshine Coast ULD. The Adelaide ULD was then sent to the Sunshine Coast. Because these ULDs had the same ULD number, it is likely the clerk misread the flight details and put the cards on the incorrect ULDs.
In the old processing system, the same ULD number can be entered twice into the system. In the new system, this would result in an error feedback. Without the error feedback, the clerk would not have known that the same container was entered twice. Furthermore, this data cross check is completed by the same person who entered it, making it difficult to detect any errors, particularly if they are experiencing a high workload.
The same error involving heavier weights could have a significant impact on the handling and performance of an aircraft.
Findings
These findings should not be read as apportioning blame or liability to any particular organisation or individual:
The incorrect ULD card was placed on the Adelaide ULD, leading it to be sent to the Sunshine Coast.
There was no error feedback on the old system of entering information into an office computer meaning the clerk would not have realised they had entered the same container number twice in the system.
Due to the absence of a staff member and the time of the year, the clerk was experiencing a high workload as they were required to take the responsibility for organising freight for all narrow body flights, rather than dividing them between two people.
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.
Freight organisation
As a result of this occurrence, the aircraft operator has advised the ATSB that they are taking the following safety actions:
The operator issued a revised loading instruction to prevent a recurrence of this type of event. The instruction stated after weighing the ULD or barrow[4], immediately record the weight on the appropriate ULD or barrow card and immediately insert in the ULD/Barrow pocket. Then close load in the Cargo system and move the ULD/Barrow to the designated staging area away from build-up areas.
Safety message
This investigation highlights the effect of high workload on data input errors, as well as the importance of system feedback to indicate that the correct data has been entered. One of the ATSB’s SafetyWatch priorities is data input errors. These errors, such as using the incorrect loading figures occur for many different reasons. The consequence of these errors include a range of aircraft handling and performance issues.
The objective of a safety investigation is to enhance transport safety. This is done through:
identifying safety issues and facilitating safety action to address those issues
providing information about occurrences and their associated safety factors to facilitate learning within the transport industry.
It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action.
Terminology
An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue.
Publishing information
Released in accordance with section 25 of the Transport Safety Investigation Act 2003
Ownership of intellectual property rights in this publication
Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia.
Creative Commons licence
With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence.
Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work.
The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau
Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.
On 15 December 2016, a Boeing 737-476SF (Special Freighter) aircraft, registered ZK-TLK (TLK), conducted a night freight flight from Sydney, New South Wales, to Melbourne, Victoria. On approach to Melbourne Airport the captain noted the aircraft nose attitude appeared to be too high and airspeed appeared to be too low for that phase of flight. After landing at Melbourne Airport, the captain was notified that a loading error occurred at Sydney Airport.
On the evening of the incident, two 737 freighter aircraft, operated by the same freight company, with the same paint scheme, were conducting freight flights into and out of Sydney Airport. The loading supervisor received loading instructions for the two aircraft shortly after they[1] started their shift at 1600 Eastern Daylight-savings Time (EDT). The loading instructions included changes to the scheduled lower compartment loads for the two 737 freighter aircraft, TLK and ZK‑JTQ (JTQ) (Figure 1).
Figure 1: Boeing 737-476SF lower compartments
Source: Operator, annotated by ATSB
At about 1945, the loading supervisor completed their ramp report, which included the planned aircraft parking bays. At 2015, they travelled to the parking bays to prepare the tarmac for the aircraft arrivals and confirm the freight was prepared for loading. At 2030, they briefed their leading hand, who was responsible for directing the transfer of the road freight to the respective aircraft parking bays.
The planned loads for TLK and JTQ were distributed into containerised and non-containerised freight. Containerised freight is loaded into the upper compartments of the 737-freighter aircraft and non-containerised freight is loaded into the lower compartment. The freight was prepared on the international side of the airport and then delivered to aircraft parking bays 5 and 6 on the domestic side of the airport.
At about 2040, the loading supervisor received a phone call from their manager that there would be an aircraft swap at Sydney Airport (see aircraft swap). Therefore, the freight planned for TLK and JTQ, needed to be exchanged between the two aircraft. The supervisor was at the tarmac at the time of the phone call and did not have access to a computer, so they manually changed their ramp report and briefed the tarmac loaders about the change. However, they only swapped the aircraft registration, flight number and inbound port on their ramp report, they did not change the parking bay numbers. According to the supervisor’s ramp report, TLK was scheduled to park on bay 6 and JTQ on bay 5. However, when the two aircraft arrived at their parking bays, at about 2136 and 2138 respectively, TLK parked on bay 5 and JTQ parked on bay 6.
The staff responsible for loading the containerised freight into the upper compartments of the aircraft loaded the aircraft with reference to their copy of the load instruction report.[2] However, the non-containerised lower compartment freight was allocated to the aircraft by the loading supervisor with reference to their ramp report parking bay numbers, which were incorrect. Consequently, TLK was loaded with JTQs lower compartment freight and JTQ was loaded with TLKs lower compartment freight. The flight crew were then issued with the load instruction reports with their planned freight, which were correct for their upper compartments, but incorrect for their lower compartments. The aircraft taxied for departure at 2247 and 2253 and departed at 2300 and 2302 respectively.
Airport curfew
While the loading supervisor was supervising the distribution of freight for the aircraft, they were also mindful of the airport curfew time of 2300. The priority for the loading supervisor in this situation is to ensure that the aircraft can depart on time. Therefore, they were required to closely monitor and assess the progress of the loading in order to be prepared to make a decision to stop the loading of freight if it posed a risk of delay past curfew.
Aircraft swap
The normal schedule for the two 737 freighter aircraft were as follows:
Flight TFR 21 from Brisbane to Sydney would depart outbound from Sydney as TFR 22 for Melbourne.
Flight TFR 34 from Adelaide to Sydney, would depart outbound from Sydney as TFR 41 for Brisbane.
On the night of the incident, JTQ operated as TFR 21 from Brisbane to Sydney and TLK operated as TFR 34 from Adelaide to Sydney. The aircraft swap in Sydney required JTQ to depart from Sydney as TFR 41 for Brisbane and TLK to depart from Sydney as TFR 22 for Melbourne.
Weight and balance
The two 737 freighter aircraft had a maximum take-off weight of 68,039 kg. The centre-of-gravity limits for the aircraft, represented as an ‘index’,[3] varied with respect to the weight of the aircraft in a non-linear manner. Table 1 depicts the planned and actual data for TLK and Table 2 depicts the planned and actual data for JTQ. The actual weight and balance for TLK was within limits, but while the weight for JTQ was within limits, the centre of gravity was marginally forward of the forward centre-of-gravity limit.[4] The weight and balance calculation is used to provide the aircraft horizontal stabiliser adjustment setting for take-off. The difference between the planned and the actual required stabiliser settings was minimal for both aircraft.
Table 1: ZK-TLK weight and balance
Planned taxi weight
58,178 kg
Index
35.1
Actual taxi weight
59,937 kg
Index
35.7
Planned landing weight
54,217 kg
Index
33.4
Actual landing weight
55,976 kg
Index
34.0
Stabiliser adjustment figures:
Planned flaps 1 & 5
4.4
Planned flaps 15
3.6
Actual flaps 1 & 5
4.3
Actual flaps 15
3.6
Table 2: ZK-JTQ weight and balance
Planned taxi weight
58,629 kg
Index
23.3
Actual taxi weight
56,875 kg
Index
22.6
Planned landing weight
54,533 kg
Index
23.1
Actual landing weight
52,779 kg
Index
22.4
Stabiliser adjustment figures:
Planned flaps 1 & 5
5.0
Planned flaps 15
4.3
Actual flaps 1 & 5
5.1
Actual flaps 15
4.4
Safety analysis
Several changes to the planned loading of the aircraft were communicated to the loading supervisor on the afternoon and evening of the incident. The loading supervisor incorporated the initial change to the lower compartment freight into their ramp report and communicated the plan to the staff. When the loading supervisor was notified that an aircraft swap would occur in Sydney, they were on the tarmac and performed a manual update to their ramp report. However, their manual update did not include the change in parking bay numbers.
The loading supervisor referred to their ramp report to direct the loading of the lower compartment freight planned for TLK and JTQ. The staff loading the upper compartments referred to their load instruction reports, which had the correct parking bays. At this time, the supervisor’s attention was divided between the freight loading activities and the overall progress of the loading of both aircraft against the approaching airport curfew time. Consequently, the supervisor directed the planned lower compartment freight for TLK to JTQ, and the planned lower compartment freight for JTQ to TLK.
The pilot of TLK reported that the aircraft’s flight management computer determines the airspeed to be flown on final approach based on aircraft weight. They entered a zero-fuel weight into the flight management computer based on the planned load, which was less than the actual load. Therefore, the target airspeed flown was slower than required for the actual weight of the aircraft and the aircraft nose attitude increased in order to produce sufficient lift to maintain the approach flight path.
Findings
These findings should not be read as apportioning blame or liability to any particular organisation or individual.
The loading supervisor made a manual change to their ramp report but did not include a change to the aircraft parking bay numbers; this resulted in them directing the lower compartment freight for TLK to JTQ, and the lower compartment freight for JTQ to TLK.
JTQ was operated with a centre of gravity marginally forward of the limit.
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.
Loading supervisor
As a result of this occurrence, the loading supervisor has advised the ATSB that they have taken the following safety actions:
Cross-check
During loading of the aircraft lower compartment freight, an independent cross-check will be made of the freight destination against the load instruction report.
Safety message
This incident highlights the risk associated with a single source of error propagating through a safety critical process. Following this incident, the loading supervisor reported that the lesson they learned was to have their work cross-checked whenever feasible.
The objective of a safety investigation is to enhance transport safety. This is done through:
identifying safety issues and facilitating safety action to address those issues
providing information about occurrences and their associated safety factors to facilitate learning within the transport industry.
It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action.
Terminology
An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue.
Publishing information
Released in accordance with section 25 of the Transport Safety Investigation Act 2003
Ownership of intellectual property rights in this publication
Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia.
Creative Commons licence
With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence.
Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work.
The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau
Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.
On 17 December 2016, at about 0855 Eastern Daylight-savings Time (EDT), a Robinson R44 II helicopter, registered VH-SJK, departed Sydney Airport, New South Wales (NSW), on a private flight to Kangaroo Valley, NSW. On board the helicopter were the pilot and three passengers.
The helicopter departed Sydney Airport and was flown at 500 ft over water to Cape Banks, on the north shore of Botany Bay, and then turned south to fly a coastal route over the water outside controlled airspace. About 16 km south of Sydney Airport, the pilot initiated a climb to keep the helicopter near the upper limit of non-controlled airspace. The helicopter was about 200–300 m offshore and climbing through 650 ft when the pilot heard the warning horn for low rotor RPM activate.
The pilot checked the engine and rotor tachometer and noted that the engine RPM was in the normal flight range, but the rotor RPM had degraded to about 85 per cent (Figure 1).[1] They immediately turned right towards land (coastal cliffs) while considering the possibility that it was an instrument fault. However, during the turn and again when over land, the rotor RPM tachometer indicated a decay in RPM whenever the pilot raised the collective.[2] The rotor RPM response to the pilot’s collective movements indicated to the pilot that there was a genuine problem with the helicopter’s drive system (see Rotor drive system).
Figure 1: VH-SJK engine and rotor tachometers
Source: Platinum Helicopters, annotated by ATSB
As soon as the helicopter was over land, the pilot identified a landing site, raised the collective to test the rotor RPM response, and, noting a decay in RPM, they lowered the collective to enter autorotation[3] from about 300 ft above ground level at 70 kt. This was about 6–8 seconds after the warning horn activated, at which time the rotor RPM was about 80 per cent. The pilot landed the helicopter with about 7–8 kt forward speed using a standard autorotation flare and cushion technique[4] at their chosen landing site. The engine and rotor were still turning after the landing, so the pilot turned off the engine, electrics and fuel cock. The time was about 0910. A mobile phone was used to call rescue services. There were no injuries, and the helicopter was substantially damaged.
Maintenance inspection
The pilot’s maintenance organisation managed the recovery of the helicopter and post-recovery inspections and tests. On arrival at the landing site, the company’s chief engineer noted that the damage to the surrounding bush indicated the helicopter was level with minimal forward speed during the landing. A functional check of the clutch actuator (see Rotor drive system) was performed on site before recovery and no fault was found with the operation.
A post-recovery maintenance inspection was conducted, which included a visual inspection and ground run of the helicopter (Figure 2). No fault was found with the engine, drive system or flight controls, but the visual inspection did find chaffing damage to a rotor tachometer wire, which was in intermittent contact with earth. Damage to the helicopter prevented a maintenance test flight.
Figure 2: VH-SJK ground running post-recovery
Source: Platinum Helicopters
An initial ground run was performed below maximum gross weight, which reached a power setting of 22 inches manifold pressure without fault. A subsequent ground run was performed after loading the helicopter to 200 kg greater than the maximum gross weight. On the second ground run a power setting of 27 inches manifold pressure, which exceeded the red line for maximum power, was reached before the helicopter became light on the skids. There was no indication of RPM decay from the engine or rotor. The chaffed rotor tachometer wire was deliberately shorted to earth during the ground runs but did not produce any fault indications from the tachometer.
The drive belts and sheave alignment were inspected and found to be within the prescribed limits (see Rotor drive system). There was no indication of slippage between the drive belts and the sheaves. During the ground runs, there were no low rotor RPM faults and the low RPM horn activated at 97 per cent rotor tachometer indication, which was the correct setting in accordance with the manufacturer’s specifications. The clutch oil was inspected for metal contamination in accordance with the maintenance manual procedure and no evidence of a defect was found. Following a recommendation from the manufacturer, the maintenance organisation performed a disassembly and examination of the clutch assembly (see Rotor drive system). No defects were found to indicate that the clutch was slipping.
Manufacturer’s comments
The pilot operating handbook states that a ‘power failure may be caused by either an engine or drive system failure and will usually be indicated by the low RPM horn.’ The manufacturer reported that the low RPM horn and the rotor tachometer are on ‘completely separate circuits, including the sensors. A failure of both systems simultaneously is extremely unlikely.’ They also noted that the governor is only used to control engine RPM and operates on a separate system with its own sensor. Therefore, the reported fault was not associated with the operation of the governor if the engine RPM remained in the governed range.
The manufacturer noted that some power must have been being delivered to the main rotor, or the rotor RPM would have decayed rapidly before the helicopter entered autorotation. A situation in which the engine was running at normal RPM and the rotor at a low RPM could only occur if there was incomplete transfer of power between the engine and the input to the main rotor gearbox. The two power transmission junctures between the engine and input to the main rotor gearbox are the V-belts and the clutch (see Rotor drive system).
The manufacturer reviewed the maintenance organisation’s photographs of the disassembled clutch assembly and agreed that there was no indication of the clutch slipping at a high-power setting.
Rotor drive system
The rotors are driven by a V-belt sheave drive system, bolted directly to the crankshaft of the engine (Figure 3). Four, double V-belts (A) transmit power from a lower sheave to an upper sheave (B), which has a clutch in its hub (C). The clutch transmits power forward to the main rotor and aft to the tail rotor. A clutch actuator (D), positioned between the lower and upper sheave, extends to tension the V‑belts and prevent slippage.
A clutch caution light is situated at the left end of the row of caution lights at the top of the instrument console. The Robinson R44 II Pilot’s Operating Handbook provided the following explanation for the clutch caution light:
indicates clutch actuator circuit is on, either engaging or disengaging clutch. When switch is in the ENGAGE position, light stays on until belts are properly tensioned. Never take-off before the light goes out.
NOTE: Clutch light may come on momentarily during run-up or during flight to retention belts as they warm-up and stretch slightly. This is normal. If, however, the light flickers or comes on inflight and does not go out within 10 seconds, pull CLUTCH circuit breaker and land as soon as practical. Reduce power and land immediately if there are other indications of drive system failure (be prepared to enter autorotation). Inspect drive system for a possible malfunction.
The pilot observed the clutch light operation before take-off to be serviceable. However, they did not notice the clutch light during the emergency and therefore could not confirm if it activated. Their attention during the emergency was focussed on the rotor RPM, airspeed and identifying an emergency landing site.
Figure 3: R44 rotor drive system
Source: Manufacturer, annotated by ATSB
Low rotor RPM stall
During the emergency landing manoeuvre, the pilot reported that the rotor RPM reduced to about 80 per cent and was conscious of a potentially unrecoverable rotor stall condition if the RPM reduced any further. The manufacturer has previously published safety notice (SN-24) on the subject: Low RPM rotor stall can be fatal. The safety notice does not include a specific RPM at which this will occur, because there are several variables involved. However, it indicates that at heights above 40 or 50 feet above ground level, a low rotor RPM stall will likely be fatal. This is because the rate of descent airflow, following the initial stall, will deepen the stalled condition of the slowly rotating blades, ‘making recovery virtually impossible, even with full down collective.’
Safety analysis
During the emergency, the pilot reported that the engine RPM did not decay, and their only indications of a fault were the low rotor RPM horn and low rotor RPM as displayed on the rotor tachometer. The pilot could not exclude activation of the clutch light during the emergency, but there was no indication of belt slippage during the post-recovery inspections and ground run tests. An internal inspection of the clutch assembly did not find evidence of clutch slippage. When the pilot manoeuvred the helicopter prior to entering autorotation, they noticed the rotor RPM decay whenever they raised the collective. When they raised the collective to cushion the landing, the helicopter responded in a power-off manner. If there was no loss of power to the rotor, then the helicopter could be expected to climb as a result of the pilot raising the collective to cushion the landing. Therefore, the low rotor RPM was probably the result of a reduction of power input to the rotor from the engine. However, during the post-recovery inspections and ground run tests, no fault was found which could explain this condition.
ATSB comment
The ATSB notes that the pilot operating handbook directs the pilot to lower the collective immediately to maintain rotor RPM between 97 and 108 per cent, following a power failure. In this case the pilot elected to delay recovering RPM until they could reach a safe landing site, since immediately lowering collective would have resulted in ditching the helicopter in the ocean.
Findings
These findings should not be read as apportioning blame or liability to any particular organisation or individual.
The low rotor RPM was probably the result of a reduction in power input to the rotor from the engine, but the fault could not be reproduced during post-recovery tests.
There was no evidence of clutch slippage occurring at a high-power setting from the disassembly and inspection of the clutch assembly.
Safety message
The pilot reported that their lesson learned following this emergency was the importance of training and professional development. Although they only used their helicopter for private flights, they trained for a commercial helicopter licence to improve their knowledge and skill in handling their helicopter. They did not believe they could have flown a successful emergency landing without their previous recurrent proficiency training in practice autorotations.
The objective of a safety investigation is to enhance transport safety. This is done through:
identifying safety issues and facilitating safety action to address those issues
providing information about occurrences and their associated safety factors to facilitate learning within the transport industry.
It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action.
Terminology
An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue.
Publishing information
Released in accordance with section 25 of the Transport Safety Investigation Act 2003
Ownership of intellectual property rights in this publication
Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia.
Creative Commons licence
With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence.
Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work.
The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau
Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.
On 18 December 2016, at about 1047 Eastern Daylight-saving Time (EDT), a Beech Aircraft Corporation B200 aircraft, registered VH-ZOK (ZOK), was on descent to Horsham Airport, Victoria. The pilot, copilot, and six passengers were on board the charter flight.
Horsham Airport was hosting a gliding competition from the 12-20 December 2016 and a notice to airmen (NOTAM)[1] had been published with information on the event (see NOTAM section below).
At about 1000 that morning, the director of the gliding competition conducted a briefing for the glider pilots and other people involved in the event. At the briefing, the selected take-off point for the conditions on the day and the schedule for marshalling the gliders out to the take-off point were discussed.
After the briefing, two ground personnel associated with the event went out to the take-off point for the gliders on runway 17 and began to lay out the 14 ropes that would be attached to the gliders and the launch aircraft. Seven ropes were placed lengthwise on the grass within the runway strip[2] on each side of the bitumen runway,[3] where it was planned the gliders would launch from. Later in the day, the ropes were to be attached to each glider and their respective tow aircraft to launch the gliders.
At the time when the event ground personnel were laying out the ropes, a powered aircraft was conducting circuits on runway 08 (Figure 1).
Figure 1: Map of airport showing runways 08 and 17 and the approximate location of the ground personnel
Source: Google earth, modified by the ATSB
As ZOK approached the circuit, the pilot was aware of one other aircraft on the common terminal advisory frequency (CTAF) that was on the downwind circuit leg for runway 08. The other aircraft was significantly slower than ZOK and the wind direction was about 140 degrees, and the wind speed was about 7 kt.[4] The pilot of ZOK elected to land on runway 17. The pilot gave an inbound broadcast on the CTAF and another as they joined downwind for runway 17.
As ZOK turned onto the base circuit leg, the aircraft on runway 08 had just landed and was backtracking to vacate the runway. A broadcast on the CTAF was made alerting the pilot of ZOK to the NOTAM. The pilot of ZOK believed the voice was that of the pilot that had just landed. The pilot of ZOK was not able to identify any gliders in the air so continued with the approach. ZOK turned onto the final approach and the pilot was able to see the bitumen part of the runway was clear.
The ground personnel noticed the sound of another powered aircraft and looked up to see the landing lights of an aircraft on final approach for runway 17. The ground personnel were located on the grass on both sides of the runway, and each moved back about 10 to 15 m within the runway white gable markers.[5]
As ZOK was on short final, again a radio communication was broadcast on the CTAF indicating that runway 17 was closed that there was ground based activity on the runway and that ZOK should go around. Again, the pilot of ZOK believed the voice was that of the pilot that had just landed. The pilot and copilot double-checked the bitumen runway and did not identify any person on the runway. As the pilot believed that the runway was not closed, given the height of the aircraft above the ground and the risks associated with going around at this height, the pilot continued with the landing.
The aircraft landed just past the threshold and taxied the full length of the runway, turned around and back tracked runway 17 to access the aircraft parking bay near the airport terminal. While backtracking, the pilot noticed two people either side of the runway on the grass about 50 m from the runway 17 threshold. The pilot, copilot, six passengers, and two ground personnel were not injured, and the aircraft was not damaged.
Pilot comment
The pilot had received a copy of the NOTAM during their preparation for the flight. Their understanding of the NOTAM was that there was a gliding competition at the airport and that runway 17/35 was available by prior arrangement. The critical hours for the competition were from 1200 to 1400. The preferred runway for the gliding competition was runway 17/35 but they could change to runway 08/26 if required.
The pilot indicated that although their arrival time was outside 1200 to 1400, they contacted the competition director on the phone number provided in the NOTAM to discuss their arrival and departure. The pilot reported that they rang on the Saturday, the day prior to the flight.
The discussion with the acting competition director concerned the glider flying and their subsequent departure time from Horsham, as that may have posed a conflict with returning gliders and how that separation would be arranged. The pilot indicated that at no stage in the conversation was it mentioned that runway 17/35 was closed to powered aircraft or that there would be people on the runway setting up for the gliders to depart. The pilot indicated that the conversation ended with the pilot believing that there was no problem with the arrival as it was outside the critical time. At the time of their departure from Horsham, the pilot planned to contact the competition director if there was any glider activity.
The pilot indicated that runway 17 was selected for landing as it was the runway that was most appropriate for the wind conditions. Another aircraft was landing on 08, which was significantly slower than ZOK and this could result in a potential conflict as the other aircraft back tracked to clear runway 08, as well as catching up to it in the circuit.
The pilot was aware that there may be glider activity and had briefed the copilot to be extra vigilant. They both ensured that there were no gliders in the area at the time. They were not aware that there might be people working on the runway and at no stage noticed any people or vehicle on the runway.
The pilot commented that it would be hard to see a person against the grass section of the runway when travelling at about 200 km/h and that it was the bitumen part of the runway that they physically landing on.
The pilot also commented that they[6] have not experienced a situation where people were on the runway and had not communicated their intentions on the CTAF to arriving or departing aircraft.
Event ground personnel comment
The event ground personnel believed that runway 17/35 was closed for the gliding competition. They reported that the active runway for powered aircraft was runway 08 and a powered aircraft was operating on that runway. There was no traffic expected and generally, at that time of the morning there is not much wind.
A radio to communicate on the CTAF was located in the vehicle that was used by the ground personnel. As they were setting up on runway 17, near where the equipment was stored, the ground vehicle had not been used to transport the ropes and was not located on or near the runway. They did not feel that the radio was needed at this time.
At the time of the incident, the ground personnel were reported to be wearing bright yellow high visibility vests.
The ground personnel reported that the NOTAM had been written the same way for many years.
Acting competition director (16 December 2016 NOTAM contact)
The acting competition director remembered speaking to the pilot two days prior to the expected arrival of ZOK.[7] The acting director’s understanding of the conversation was that:
the arrival time would not conflict with the launching of the gliders
the pilot was aware the NOTAM was in force and that the pilot did not want to interfere with the glider traffic
the pilot mentioned that they would be able to land in a 15 kt crosswind, which further indicated that they were happy to land on runway 08/26.
The acting director believed that the pilot understood that runway 17/35 was ‘closed’[8] to powered traffic and that the pilot would use 08/26, which was the active runway for all powered aircraft, however this was not specifically discussed.
The pilot of ZOK rang two days prior to their arrival and in that time the weather conditions can change.
The acting directors understanding of the NOTAM was that:
17/35 was ‘closed’ to all powered traffic
there was high glider activity in the area
if anyone wanted to use 17/35 they had to ring the competition director up to 30 minutes before using that runway, but this was not specified in the NOTAM.
The vehicle that the ground personnel had available included a rotating flashing beacon (the vehicle was not used at the time of the incident).
The grass on the runway strip had been specially mowed for the event.
Competition director
The competition director indicated that the airport operator issued the NOTAM and they understood that the NOTAM closed runway 17/35 to non-glider related traffic during daylight hours. The NOTAM had been written this way for about 3 to 4 years. The wording of the NOTAM had evolved over 10 years. About 3 to 4 years ago, the wording changed from ‘closing’ runway 17/35 to powered aircraft for a short period, to ‘closing’ it to powered aircraft for the entire day to give powered pilots better notice.
The competition director indicated that they did not believe a general discussion of potential operations at unspecified times constituted either a request for or a granting of permission to use runway 17/35.
The director reported that generally at that time of the year the wind favours runway 17 and it could not be determined which runway would be the most suitable for the glider operations more than 2 hours ahead of time.
The director indicated that similar incidents have happened over the years but on this occasion, there were people and equipment on the runway strip. A search of the ATSB occurrence database did not find any reported events involving landing powered aircraft (see Previous incidents below).
The director indicated that permission for an aircraft to land or take off on runway 17/35 would need to be discussed at the time as it depends on the:
operational situation
wind
if gliders are on the strip waiting to be launched.
Notice to airmen (NOTAM)
The NOTAM for the glider flying competition was issued and applicable from 1000 on the 12 December 2016 to 2100 on the 20 December 2016 during sunrise to sunset (Figure 2). The NOTAM indicated that:
there was intensive glider flying confined to runway 17/35
the use of runway 17/35 during sunrise to sunset by other aircraft was only by prior arrangement with the competition director
runway 08/26 may be used for glider flying if runway 17/35 was not suitable
glider traffic information was available on the CTAF 118.8 and visiting aircraft should plan to arrive or depart outside the hours of 1200 to 1400 local time if possible
phone numbers were provided to contact the director for further details. On 16 December, a different mobile number was provided to contact the director.
Figure 2: NOTAM
Source: Airservices Australia, phone numbers redacted by the ATSB
The Horsham airport operator forwarded a copy of the NOTAM wording to CASA prior to submitting the NOTAM to Airservices Australia to be issued. CASA provided a response to the airport operator that based on the information provided they had no objection to the proposed NOTAM.
Previous incidents
A search of the ATSB database identified one other notification in the last ten years that involved a glider event and a powered aircraft at Horsham Airport. In 2016, during final approach, three gliders were required to manoeuvre to ensure separation from a single-engine aircraft that was taxiing up and down the runway at high speed before taking off. No radio calls were heard from the single-engine aircraft.
Safety analysis
The pilot of ZOK had received a copy of the NOTAM while conducting their preparation for the flight. After reading the NOTAM, they assessed that if they contacted the competition director prior to the flight, they could use runway 17/35.
They believed that by ringing the competition director before the flight, they had made a prior arrangement to use runway 17 and, as the intended arrival time was outside the ‘critical’ hours of 1200 to 1400 specified in the NOTAM, their arrival would not interfere with the competition. As neither party specifically talked about runway 17/35, a connection was not made that there was a different understanding of what the NOTAM meant, and that permission was not, nor could it have been granted to use runway 17/35 when the weather conditions for the launch day were not known.
The gliding club believed that the NOTAM ‘closed’ the runway to all aircraft during daylight hours, apart from the gliders and tow aircraft taking part in the competition. Due to this interpretation, the ground handlers for the event did not make any radio calls before they entered the runway strip to prepare for the competition. Nor did they carry the radio that was available in their vehicle.
The NOTAM is also not clear when permission is needed to use runway 17. The pilot assessed that as they had contacted the director and discussed the flight, they had made an arrangement to use the runway. The competition director believed that there was a requirement for the pilot of an aircraft intending to use runway 17/35 to contact them on the day of the flight.
An opportunity to alert the pilot that there was ground activity on the runway was missed, as the ground vehicle, which had a rotating beacon, was not used (located near or on the runway) due to the close proximity of the equipment to the launch site. In addition, the ground personnel did not have a radio with them to communicate on the CTAF.
Findings
These findings should not be read as apportioning blame or liability to any particular organisation or individual.
Landing on runway 17, the pilot of ZOK was not aware that two people were located inside the white gable markers denoting the runway strip and that ropes were located beside the runway in preparation for launching gliders.
The NOTAM for gliding operations was open to misinterpretation.
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.
Airport operator
As a result of this occurrence, the airport operator has advised the ATSB that they are taking the following safety actions:
Improved wording to the NOTAM issued for future gliding events will be developed with gliding event officials and CASA so prior approval would need to be obtained within two hours of the intended use of the runway, to ensure that current weather conditions and gliding operations could be considered at the time.
Safety message
This incident highlights the critical importance of communications and as discussed in the CASA Flight Safety Australia magazine September-October 2012, Mind your language the importance of what you say and how you say it for both the written and spoken word, ‘your words matter‑make no mistake’. The article identifies three ways that NOTAMs fail in relevance, ambiguity, and readability. NOTAMs should always be clear and concise and leave no room for misinterpretation.
The objective of a safety investigation is to enhance transport safety. This is done through:
identifying safety issues and facilitating safety action to address those issues
providing information about occurrences and their associated safety factors to facilitate learning within the transport industry.
It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action.
Terminology
An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue.
Publishing information
Released in accordance with section 25 of the Transport Safety Investigation Act 2003
Ownership of intellectual property rights in this publication
Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia.
Creative Commons licence
With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence.
Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work.
The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau
Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.
On 15 December 2016, an Airbus A330-202 aircraft, registered VH-EBA and operating Qantas Flight (QF) 652, was on descent to Brisbane Airport, Queensland, arriving from the south-west from Perth, Western Australia. QF652 was sequenced to follow another Qantas Airbus A330-303 aircraft, registered VH-QPG and operating QF62, which was also on descent to Brisbane Airport, but arriving from the north-west from Narita, Japan.
For noise abatement, reciprocal runway operations were in progress at Brisbane, with arriving aircraft landing on runway 19, and departing aircraft taking off from runway 01.
At 0516:25 Eastern Standard Time (EST), the approach controller cleared QF62 to descend to 5,000 ft.
At 0517:55, a Qantas Boeing 737-838 aircraft, registered VH-VXF and operating QF601, (departing Brisbane for Melbourne, Victoria) took off from runway 01 and was tracking to the south-west. At 0519:15, the approach controller cleared QF601 to climb to 8,000 ft.
Five seconds later, the approach controller cleared QF652 to descend to 9,000 ft for separation with QF601 travelling in the opposite direction. The controller advised the crew of QF652 that they would be cleared for further descent once they had passed opposite direction traffic. The controller then also advised the flight crew of QF601 that there would be a short delay at 8,000 ft due to opposite direction traffic above.
At 0520:20, the controller inadvertently cleared QF652 (instead of QF62) to descend to 2,500 ft and conduct an ILS approach to runway 19. The crew of QF652, still on descent to 9,000 ft, read back the clearance and set their assigned altitude to 2,500 ft (which was normal procedure having been cleared for the descent). The crew sighted the opposite direction aircraft out to their right and continued their descent.
About 30 seconds later, the air traffic system identified a discrepancy between the controller-cleared flight level of 9,000 ft and the flight crew-entered altitude of 2,500 ft. The controller received a predicted level mismatch (PLM) alert, which displays as ‘cleared flight level (CFL?)’.[1] The controller asked the crew of QF652 to confirm they were maintaining 9,000 ft, and the crew responded that they were on descent to 2,500 ft as cleared. The aircraft was passing 9,200 ft at this stage. The controller immediately responded ‘no, that was for Qantas 62, Qantas 652 maintain 9,000’. By that time, radar data indicated that QF62 was at 4,900 ft. No read back was heard from the crew of QF62 to the clearance inadvertently issued to QF652.
The flight crew of QF652 reported that they were passing about 8,600 ft, when the controller instructed them to maintain 9,000. The crew stopped the descent and climbed the aircraft back up to 9,000 ft. The crew received a traffic alert[2] for about 5 seconds on the reciprocal aircraft. At 0521:19, the controller cleared the flight crew of QF652 to descend to 8,000 ft and the aircraft subsequently conducted a normal approach to Brisbane.
Figure 1: Traffic disposition and PLM alert
Source: Airservices Australia – annotated by ATSB
Safety analysis
Separation
As the two aircraft passed each other, radar data showed QF652 at an altitude of 9,000 ft and QF601 at 8,000 ft, with 2.3 NM lateral separation (Figure 1). Figure 2 shows QF652 at 8,700 ft and lateral separation with QF601 of 2.6 NM (Figure 2). The incorrect descent clearance resulted in a loss of separation with QF601, where the separation required was 3 NM or 1,000 ft and the minimum separation recorded was 2.5 NM and 700 ft.
Figure 2: Loss of separation
Source: Airservices Australia – annotated by ATSB
Controller comments
The approach controller had been in the position since 0200 and reported feeling alert, well rested and that things were going very well in the minutes prior to the incident in adhering to noise abatement requirements and keeping the traffic moving. The controller commented that between 0500 and 0600 they get busy; departures tend to conflict with arrivals and traffic can be quite complex at times. The controller assessed that their workload at the time was moderate.
The controller commented that when they identify similar call signs, there are techniques they employ such as appending ‘heavy’, or the aircraft’s position in the sequence, to the call sign, but did not do that in this instance. Both inbound aircraft were ‘heavy’ so it would not have helped to resolve the possible confusion.
After giving the clearance (inadvertently) to QF652 that was meant for QF62, both aircraft appeared to descend.[3] When the flight crew read back ‘Qantas six fifty two’, the controller did not identify the mismatch of the data in the aircraft label with the response, possibly because it was the expected response to the clearance instruction.
Flight number call signs
According to the Australian Aeronautical Information Publication (AIP) General 3.4 paragraph 4.17, rules for aircraft call signs include that flight numbers should ‘take into account flight numbers already in use by the operator and other agencies in the intended control environment, operational area or nearby’.
Call sign confusion
The Manual of Air Traffic Services (MATS) 6.2.1.1 Callsign confusion stated:
When similar callsigns may cause confusion you may take action to minimise errors including:
a) emphasising certain numbers/letters;
b) repeating the entire callsign e.g. QANTAS451 QANTAS451;
c) repeating the prefix e.g. QANTAS451 QANTAS;
d) advising pilots that there are aircraft with similar callsigns on frequency; or
e) instructing pilots to use a different callsign either temporarily or for the duration of the flight.
Airservices Australia initiative
After a number of REPCON (confidential reports) related to flight number call sign confusion in the Brisbane area, Airservices Australia (Airservices) established a process to monitor and increase awareness of reported call sign confusion issues. The process involves reviewing the call sign confusion occurrences reported through their internal reporting system and notifying relevant airlines of the reported occurrence. In addition, Airservices provides a ‘call-sign conflict report’ to domestic aircraft operators each month.
Airservices advised that the distribution of the monthly call sign confusion reports to domestic operators was paused in 2016. This was to allow for an upgrade to an improved information system as the basis of the report. However, given a new system has yet to be commissioned Airservices has reinstated use of the previous system, and will continue to distribute monthly call sign confusion reports while working on improvements to the advice provided to industry.
Airservices also commented that a number of current mitigation measures currently exist for pilots and controllers to respond to call sign confusion, including documented AIP and MATS procedures to minimise the likelihood of call sign confusion. Additionally, Australia utilises 'group format' as the preferred means of transmitting call sign/flight number within Australian airspace in an effort to reduce the possible confusion with assigned flight levels or headings.
Findings
These findings should not be read as apportioning blame or liability to any particular organisation or individual.
The controller inadvertently assigned descent to QF652 instead of QF62 due to call sign confusion, resulting in a loss of separation with QF601.
The two inbound aircraft were operating on the same frequency with similar call signs and call sign confusion mitigation strategies were not used by air traffic control.
ATSB comment
According to the article Callsign Confusion, the US Aviation Safety Reporting System (ASRS) receives a large number of reports of call sign confusion, some of which result in losses of separation. The article states that communications technique is pilots’ and air traffic controllers’ primary defence against confusion and that they need to continue to bring call sign problems to the attention of management.
The Skybrary article Call-sign confusion lists contributory factors including:
failure of operator to give sufficient consideration in allocation of call signs
pilot and controller workload
interruption or distraction
airspace and procedure design
traffic density.
Safety message
Air traffic control and flight crew need to be vigilant when they identify the potential for call sign confusion.
Flight numbers are assigned by airlines, some of which operate call sign de-confliction programmes. The ATSB encourages aircraft operators to use these strategies to help prevent similar incidents occurring. Air traffic control is encouraged to consider liaising with airlines to enhance call sign de-confliction programmes.
The objective of a safety investigation is to enhance transport safety. This is done through:
identifying safety issues and facilitating safety action to address those issues
providing information about occurrences and their associated safety factors to facilitate learning within the transport industry.
It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action.
Terminology
An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue.
Publishing information
Released in accordance with section 25 of the Transport Safety Investigation Act 2003
Ownership of intellectual property rights in this publication
Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia.
Creative Commons licence
With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence.
Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work.
The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau
Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.
At about 0730 Eastern Daylight-saving Time (EDT) on the 14 December 2016, a Pelican Airlines British Aerospace Jetstream 32 aircraft, registered VH-OTQ (OTQ), departed Newcastle (Williamtown) Airport for Dubbo, New South Wales (NSW). Two flight crew and six passengers were on board the regular public transport flight.
Just after the aircraft reached the cruising altitude of FL 160,[1] the captain who was the pilot monitoring,[2] noticed the right engine exhaust gas temperature (EGT) gauge was indicating just outside the top of the green arc (650 °C) and was indicating about 655 °C in the yellow arc. The captain reduced the power to the right engine, but there was no corresponding reduction in the EGT.
The flight crew conducted the quick reference handbook (QRH) emergency checklist for the lack of response to power lever movement, which included the engine ignition selected to continuous operation and the engine and airframe ice protection turned on. In accordance with the checklist, the power lever was checked after about 5 minutes and was found to still be unresponsive. The captain indicated that this was very unusual and turned off the engine computers to try to isolate the fault, but this made little difference and so they turned the computers back on. The captain then moved the power lever further back and noticed a momentary increase in EGT, by about 8 °C to 10 °C, as well as an increase in torque.
At this stage of the flight, the aircraft was at a position where they would ordinarily change frequency to a different air traffic controller. However, the flight crew decided to remain on this frequency and return to Newcastle Airport. When the controller instructed the crew to change frequency, the crew advised the controller of their situation and requested a new clearance to return to Newcastle. The crew also advised the controller that as a precaution they might conduct an in-flight engine shut down. The controller gave them a clearance to descend and track direct to Newcastle and subsequently confirmed with the crew that the airport emergency services were required to be available. The controller initiated an alert phase[3] and the airport emergency services were requested to be on standby.
The flight crew followed the guidance in the QRH checklist to continue to operate the engine and noted that an engine shut down may be necessary for the approach and landing. As the aircraft was lightly loaded, the captain believed that there would be no issues operating on one engine. The crew conducted the QRH engine in-flight shutdown checklist and shutdown the right engine prior to commencing their descent to Newcastle. The captain briefed the passengers through the aircraft’s public address (PA) system about the precautionary engine shut down and instructed them to familiarise themselves with the passenger safety card.
At about 50 km from Newcastle and on descent passing through about 8,000 ft, the captain became the pilot flying and the first officer the pilot monitoring. They reviewed the QRH abnormal checklist for landing with one engine inoperative. The crew conducted a visual approach and landed on runway 30 without further incident. The two crew and six passengers were not injured, and the aircraft was not damaged.
Captain’s comment
The captain reported that they were flying at a level where icing conditions may be encountered and from previous experience, flying in a different country, it was not uncommon to have an unresponsive power lever control in icing conditions.
The captain reported that they had adequate time to assess the unresponsive power lever, evaluate the performance of the aircraft with only one engine operating and plan for the landing. The workload was not high as they were flying in visual meteorological conditions with adequate time and no other traffic.
On reflection, the captain indicated that although the situation did not appear like an emergency, making a PAN PAN[4] call to the controller would have eliminated any uncertainty.
The captain indicated that they had only conducted engine shut downs in a training environment and this was the first time landing with one engine inoperative.
Operator comment
The operator reported that the aircraft had been in storage in Australia from 2007 to March 2016. Since March, the aircraft had undergone major maintenance at an aircraft maintenance facility. The right engine involved in the incident had undergone maintenance at an engine overhaul facility and had been preserved during its time of inactivity, prior to its installation on OTQ. The aircraft was released to service 11 days (about 26 flight hours) prior to the incident occurring.
Aircraft maintenance personnel inspected the right engine after the flight and found that the engine’s fuel control unit[5] was at fault. An examination of the fuel control unit at a component overhaul facility found that the input drive shaft was not free to move. The fuel control unit was inspected and a bearing was found to have failed (Figure 1). The phenolic bearing cage[6] that separates the bearings was found broken (Figure 2) with many small fragments found to be interfering with the operation of the fuel control unit in that area.
Figure 1: Failed bearing assembly
Source: Aircraft operator
Figure 2: Pieces of the failed phenolic bearing cage
Source: Aircraft operator
Findings
These findings should not be read as apportioning blame or liability to any particular organisation or individual.
The engine issue related to a failed fuel control unit bearing, where fragments of the bearing cage interfered with the unit’s operation.
Safety message
It is important when time permits to broadcast a ‘pan’ or ‘mayday’, whichever is applicable, to air traffic control to alert the controller and remove any uncertainty about the severity of the situation. If controllers receive a ‘pan’ or ‘mayday’ broadcast, they will organise (depending on the situation) a priority landing to allow an aircraft that might have a problem to land as soon as possible. A situation that seems relatively innocuous can deteriorate quickly. Hesitating or not broadcasting the situation can result in help being delayed.
Airservices Australia defines the two levels of emergency notifications as:
MAYDAY: My aircraft and its occupants are threatened by grave and imminent danger and/or I require immediate assistance.
PAN PAN: I have an urgent message to transmit concerning the safety of my aircraft or other vehicle or of some person on board or within sight but I do not require immediate assistance.
Additional information is provided in the following publications:
Airservices Australia In-flight emergencies, is available from the Airservices website.
The objective of a safety investigation is to enhance transport safety. This is done through:
identifying safety issues and facilitating safety action to address those issues
providing information about occurrences and their associated safety factors to facilitate learning within the transport industry.
It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action.
Terminology
An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue.
Publishing information
Released in accordance with section 25 of the Transport Safety Investigation Act 2003
Ownership of intellectual property rights in this publication
Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia.
Creative Commons licence
With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence.
Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work.
The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau
Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.
On 13 December 2016, a Beech Aircraft Corporation B200, registered VH-MVL, conducted a visual approach to Moomba Airport, South Australia (SA), following a medical services flight from Innamincka, SA. As the aircraft turned onto the base leg of the approach, the pilot observed the left engine fire warning activate. The pilot shut down the left engine and continued the approach to the runway. The aircraft landed in the sand to the left of the runway threshold and after a short ground roll, spun to the left and came to rest. There were no injuries, and the aircraft was substantially damaged.
What the ATSB found
The ATSB found that the pilot did not feather the left propeller (rotate the blades to an edge-on angle to the airflow) after the left engine was shut down, causing it to windmill, resulting in considerable drag. In addition, the aircraft was in a right turn, towards the engine developing power, with the landing gear extended and the flaps set to approach. This combination resulted in more thrust being required for continued safe flight than was available.
No engine fire damage was found and it was therefore concluded that the observed fire warning was almost certainly a false warning. The aircraft manufacturer had previously published a service bulletin for the optional replacement of the engine fire detection system with a system less susceptible to false warnings. However, the operator, who had limited experienced with false engine warnings in their fleet which were also considered as low risk, elected not to replace the fire detection system on the accident aircraft.
The accident pilot did not receive the operator’s published syllabus of training for the B200 King Air. Instead, a tailored training program was delivered in consideration of the pilot’s experience on the C90 King Air with another operator and advice the operator received from the Civil Aviation Safety Authority. This training did not cover all the elements required under the Civil Aviation Safety Regulations.
What's been done as a result
As a result of this occurrence, the Civil Aviation Safety Authority (CASA) intends to take steps to refresh industry and CASA officers’ knowledge of particular terms and concepts within the flight crew licencing regulations to remove any doubt that might exist as to their interpretation and applicability.
The operator has undertaken to take safety actions in the areas of pilot recruitment, training and checking, aircraft and systems, safety and quality assurance, and communications.
Safety message
Following the accident, the pilot reported that their biggest lesson was not to hesitate during emergency procedures. They believed that their doubt in the veracity of the warning resulted in their hesitation while completing the four engine fire drill (memory) actions, resulting in them missing the step to feather the propeller.
This accident also highlights the need for organisations to consider all the relevant information available to them when making decisions, such as the process for reviewing non‑mandatory service bulletins. Organisational decision-making should consider the potential consequences of human error when evaluating changes.
The occurrence
On 13 December 2016, a Beech Aircraft Corporation B200, registered VH-MVL, conducted a medical services flight from Innamincka, South Australia (SA) to Moomba, SA. On board the aircraft were the pilot and two passengers.
On arrival at Moomba at about 1250 Central Daylight-saving Time (CDT), the pilot configured the aircraft to join the circuit with flaps set to the approach setting and the propeller speed set at 1900 RPM.[1] They[2] positioned the aircraft at 150–160 kt airspeed to join the downwind leg of the circuit for runway 30, which is a right circuit.[3] The pilot lowered the landing gear on the downwind circuit leg. They reduced power (set 600-700 foot-pounds torque on both engines) to start the final descent on late downwind abeam the runway 30 threshold, in accordance with their standard operating procedures.
At about the turn point for the base leg of the circuit, the pilot observed the left engine fire warning activate. The pilot held the aircraft in the right base turn, but paused before conducting the engine fire checklist immediate actions in consideration of the fact that they were only a few minutes from landing and there were no secondary indications of an engine fire. After a momentary pause, the pilot decided to conduct the immediate actions. They retarded the left engine condition lever[4] to the fuel shut-off position, paused again to consider if there was any other evidence of fire, then closed the firewall shutoff valve, activated the fire extinguisher and doubled the right engine power[5] (about 1,400 foot-pounds torque).
The pilot continued to fly the aircraft in a continuous turn for the base leg towards the final approach path, but noticed it was getting increasingly difficult to maintain the right turn. They checked the engine instruments and confirmed the left engine was shut down. They adjusted the aileron and rudder trim to assist controlling the aircraft in the right turn. The aircraft became more difficult to control as the right turn and descent continued and the pilot focused on maintaining bank angle, airspeed (fluctuating 100–115 kt) and rate of descent.
Due to the pilot’s position in the left seat, they were initially unable to sight the runway when they started the right turn. The aircraft had flown through the extended runway centreline when the pilot sighted the runway to the right of the aircraft. The aircraft was low on the approach and the pilot realised that a sand dune between the aircraft and the runway was a potential obstacle. They increased the right engine power to climb power (2,230 foot-pounds torque) raised the landing gear and retracted the flap to reduce the rate of descent. The aircraft cleared the sand dune and the pilot lowered the landing gear and continued the approach to the runway from a position to the left of the runway centreline.
The aircraft landed in the sand to the left of the runway threshold and after a short ground roll spun to the left and came to rest (Figure 1). There were no injuries, and the aircraft was substantially damaged.
The pilot reported there was a left engine fire warning, which resulted in them performing an emergency engine shutdown and activating the fire extinguisher. On inspection by the operator, the left engine fire bottle was found to be discharged, but there was no evidence of fire damage. The activation of the master warning followed by the separation of the propeller speeds, as detected by the cockpit voice recorder, were consistent with the pilot’s report of a fire warning and left engine shutdown. Therefore, the ATSB concludes that the pilot likely experienced a fire warning, which was almost certainly a false indication.
The ATSB did not establish what initiated the fire indication. However, it was noted that the optical fire detection system fitted to the aircraft was susceptible to false indications. In 1995, Beechcraft issued a service bulletin (SB 2596) for a continuous loop fire and overheat detection system to ‘improve reliability and maintainability.’ In July 2003, after three reports of false engine fire indications earlier that same year, the operator reviewed the bulletin but elected not to incorporate the modification. The operator also decided not to incorporate the modification after a Civil Aviation Safety Authority (CASA) airworthiness bulletin in 2013 recommended incorporating the manufacturer’s modification. Neither review made reference to the flight risk of false engine fire indications. However, the operator’s previous false engine fire warning reports recorded them as low risk and their last report was in 2005.
The earliest safety management manual the operator was able to provide the investigation was dated 2006, some three years after the operator’s review of SB 2596. Therefore the operator’s risk assessment process, as it applied to the earlier false engine fire warnings and review of SB 2596 was not investigated any further.
In consideration of CASA’s findings of the effectiveness of SB 2596 to eliminate false fire indications, it is apparent that the incorporation of the manufacturer’s modification would have reduced the risk of a false fire warning occurring.
One engine inoperative performance
The pilot reported that, following their observation of an engine fire indication, they completed three of the four immediate memory actions, but omitted to manually feather the left propeller. They then experienced considerable difficulty handling the aircraft in the right turn and were unable to reach the runway, despite applying climb power to the right engine.
Although the aircraft was fitted with an autofeathering system for the propellers, the system was only operative at high power settings. As the pilot had reduced power for descent by the time of the engine fire indication, the autofeathering system was inoperative, as per design, when the engine was shutdown.
As a result, the approach was flown with the left propeller unfeathered and windmilling. When combined with the drag from the landing gear, flap and right turn, the additional drag from the windmilling propeller resulted in more thrust required for the approach than was available.
Pilot’s actions
The pilot reported that they hesitated in their decision-making and subsequent engine fire drill actions because of their uncertainty in the veracity of the indication and their proximity to landing. At the time of the master warning, they had just started the base turn on approach to land, which required their attention to be divided between the cockpit settings and indications, and the external cues for the visual approach. It is possible that divided attention, combined with their hesitation while performing the steps of the drill, contributed to them omitting the step to feather the propeller in their immediate actions.
After the pilot shutdown the left engine, they experienced increasing difficulty controlling the aircraft in the right turn. They checked to confirm the left engine was shutdown, applied full right aileron and rudder trim, applied climb power to the right engine, retracted the landing gear and flap, and finally extended the landing gear for the landing. However, they did not attempt to feather the propeller at any stage during the approach. This indicates that the pilot did not recognise that their asymmetric handling difficulties were the result of a windmilling propeller, despite the need for climb power on the right engine. The aircraft configuration and performance on approach resulted in the aircraft operating within the airspeed caution range for a loss of directional control.
The pilot’s training and assessment reports indicated that their asymmetric flight experience on the B200 extensively involved engine failures on take-off and engine fires in cruise. In the case of engine failures on take-off, the autofeather system will feather the propeller of the failed engine. In the case of engine fires in cruise, the propeller is manually feathered by the pilot in the emergency engine shutdown procedure. The operator’s performance standards for asymmetric flight included that the pilot was able to identify the correct control lever and feather the propeller, which was consistent with the performance standards required in the Part 61 Manual of Standards. The pilot was assessed as competent to this standard by the operator with no knowledge deficiencies identified. The pilot’s previous successful handlings of an engine fire in the simulator, and their inability to stop the aircraft descending, likely contributed to them continuing the approach.
Based on the above asymmetric training experience, it is likely the pilot had no prior experience of the B200 handling characteristics with a windmilling propeller, which likely contributed to them not recognising (and recovering) from that condition within the timeframe of the accident sequence. However, the pilot’s C90 training experience with another operator was not investigated for potential knowledge transfer to the B200. The ATSB only offers this as a possible explanation for why the pilot did not associate the performance and handling difficulties with a windmilling propeller. Operating the aircraft with a windmilling propeller was not a competency requirement.
Differences training
Within CASR Part 61, differences training applied to the ‘type rating’ system, but not the ‘class rating’ system. The training requirements for a type rated aircraft are considered more complex than for a class rated aircraft. Therefore, differences training is employed in the type rating system to transition a pilot from the variant[24] the pilot conducted their type rating on, onto another variant covered by the same type rating.[25] The legislative instrument ‘Prescribed aircraft, ratings and variants for CASR Part 61 Instrument 2014’ (Edition 1), indicated when differences training was required for type rated aircraft, in addition to when initial type-specific training was required for class rated aircraft. The instrument identified the Beechcraft King Air 90 series and King Air 200/250 series as aircraft types, which required initial type-specific training.
Within the differences training system, it is permissible to not deliver all the units of competency from the Part 61 Manual of Standards.[26] This avoids unnecessary duplication of training while ensuring the pilot receives the training necessary to operate variants, which are different to the variant the pilot conducted their type rating on. In contrast, a class rated aircraft requires all the units of competency relevant to the aircraft type to be delivered. However, for a class rated aircraft there may be no additional training requirement for a pilot to operate different models (variants) of the same type, as prescribed in the respective legislative instrument. Therefore, the requirement for differences training increases the overall training burden within the type rating system, in line with the greater complexity of the aircraft, when compared to the class rating system.
The ATSB acknowledges that an operator may consider previous qualifications and training in determining the number of sequences required to deliver the units of competency within the class rating system. However, reference to differences training may inadvertently imply that not all units of competency are required to be delivered or assessed. In the case of the accident pilot, the ATSB could not find a training or assessment record for the competency ‘A5.1 – Enter and recover from stall’[27] in addition to the upper air asymmetric sequences.[28] This would have been captured if the operator delivered their B200 syllabus of training to the pilot.
Upper air asymmetric training sequences are used to teach a pilot the performance and handling characteristics, specific to the aircraft type, in various configurations and flight path parameters. It provides the opportunity for the instructor to direct the trainee pilot’s attention to changes in aircraft performance associated with changes in attitude and configuration, without the distraction of checklist actions or instrument approach procedure requirements. This can lead to more effective learning of the underpinning knowledge and skills required to operate a new aircraft type. At the time of the accident, the pilot had operated the B200 for 22 months without training or assessment in stalling.
The ATSB determined that the application of differences training, as defined in CASR Part 61, to the transition of a pilot onto the B200 was inconsistent with the requirement for initial type-specific training in accordance with CASR 61.747. The omission of training or assessment in flight regimes near to or in a loss of control situation (for example, VMCA demonstration and stalling), may result in a degradation of knowledge and skills that are only required in rare, but time-critical, emergency situations.
Whether or not the ATSB identifies safety issues in the course of an investigation, relevant organisations may proactively initiate safety action in order to reduce their safety risk. The ATSB has been advised of the following proactive safety action in response to this occurrence.
Civil Aviation Safety Authority
As a result of this occurrence, the Civil Aviation Safety Authority (CASA) advised the ATSB that they concur that the regulatory requirements for pilots transitioning between aircraft models of a type listed in Schedule 13, including from the Beechcraft King Air 90 series to the King Air 200/250 series aircraft, might be open to misinterpretation, and they are taking the following safety action:
Education
CASA intends to take steps to refresh industry and CASA officers of particular terms and concepts within the CASR 1998 flight crew licensing suite to remove any doubt that might exist as to their interpretation and applicability. For example, terms such as differences training, flight review, competency, competency-based-training, recognition of prior learning, qualifications and experience will be clarified.
Operator
As a result of this occurrence, the aircraft operator conducted an internal investigation and advised the ATSB that they are taking the following safety actions:
Recruitment
Conduct a review of their current recruitment process, including entry standards and consideration of additional processes to the current standard of interview and simulator test.
Engage with a university to study pilot recruitment in order to better understand the ideal pilot traits required for the company’s operations.
Training and checking
Conduct a review of existing pilot induction/training/clearance to line procedures, and increase use of Level D simulator wherever possible for initial and recurrent emergency procedures.
All new pilots will complete the company’s full induction training, including aircraft endorsement training.
Review and rewrite of the company operations manual, and training and checking manual.
Safety and quality assurance
Accelerate the introduction of the flight data analysis program and undertake a trial of line orientated safety audit.
Aircraft and systems
Install flight data recorders on all aircraft and include flight data recorders as a mandatory item for aircraft standards.
Install Pratt & Whitney flight acquisition, storage and transmission (FAST) on all aircraft and include FAST as a mandatory item for aircraft standards.
Communications
In-person briefing program with the pilot workforce to discuss findings and agreed safety actions from the company’s internal investigation with a focus on lessons learned from the accident.
Findings
From the evidence available, the following findings are made with respect to the collision with terrain involving Beech Aircraft Corporation B200, registered VH-MVL that occurred at Moomba Airport, South Australia on 13 December 2016. These findings should not be read as apportioning blame or liability to any particular organisation or individual.
Contributing factors
The operator did not modify the aircraft to include a more reliable engine fire detection system in accordance with the manufacturer’s service bulletin, and as subsequently recommended by the Civil Aviation Safety Authority’s airworthiness bulletin. The incorporation of the manufacturer’s modification would have reduced the risk of a false engine fire warning.
During the approach phase of flight, the pilot shutdown the left engine in response to observing a fire warning, but omitted to feather the propeller. The additional drag caused by the windmilling propeller, combined with the aircraft configuration set for landing while in a right turn, required more thrust than available for the approach.
Other factors that increased risk
The advice from the Civil Aviation Safety Authority to the operator, that differences training was acceptable, resulted in the pilot not receiving the operator’s published B200 syllabus of training. The omission of basic handling training on a new aircraft type could result in a pilot not developing the required skilled behaviour to handle the aircraft either near to or in a loss of control situation.
Other findings
The pilot met the standard required by the operator in their cyclic training and proficiency program and no knowledge deficiencies associated with handling engine fire warnings were identified.
Sources and submissions
Sources of information
The sources of information during the investigation included the:
Civil Aviation Safety Authority
Textron Aviation (B200 Type Certificate Holder)
operator
pilot.
References
Civil Aviation Safety Regulation Part 61, dated 4 November 2014
Civil Aviation Safety Authority legislative instrument ‘Prescribed aircraft, ratings and variants for CASR Part 61 Instrument 2014’ (Edition 1), dated 5 January 2015
Civil Aviation Safety Authority explanatory statement ‘Prescription of aircraft and ratings – CASR Part 61 (Edition 1), dated 5 January 2015
Civil Aviation Advisory Publication 5.23-2(0): Multi-engine aeroplane operations and training, dated July 2007
Civil Aviation Advisory Publication 5.59A-1(0): Competency based training and assessment in the aviation environment, dated July 2009
Raytheon Aircraft Company, Beechcraft King Air B200 & B200C pilot’s operating handbook and FAA approved airplane flight manual, dated 2004
Raisbeck Engineering Company, pilot’s operating handbook and FAA-approved airplane flight manual supplement for the Beechcraft Super King Air models B200/B200C/B200T/B200CT, dated 2016
Operator’s training and checking manual, version 2.1, dated 19 January 2015
Operator’s quick reference handbook for Raisbeck B200/C, dated 15 June 2004
Beechcraft service bulletin 2596, Fire protection – continuous loop fire and overheat detection system installation, dated October 2015
Civil Aviation Safety Authority airworthiness bulletin 26-005, Beech B200 series engine fire detection systems, issue 1, dated 10 April 2013
Super King Air 200 series maintenance manual, propeller autofeathering system – description and operation, revision D4, 1 November 2016, printed from Beechcraft Corporation Interactive Maintenance Library
H. H. Hurt, Jr., Aerodynamics for naval aviators, NAVAIR 00-80T-80, University of Southern California, USA, 1965.
United States Federal Aviation Administration advisory circular (AC 120-53B CHG 1), guidance for conducting and use of flight standardisation board evaluations, dated 5 November 2013
Submissions
Under Part 4, Division 2 (Investigation Reports), Section 26 of the Transport Safety Investigation Act 2003 (the Act), the ATSB may provide a draft report, on a confidential basis, to any person whom the ATSB considers appropriate. Section 26 (1) (a) of the Act allows a person receiving a draft report to make submissions to the ATSB about the draft report.
A draft of this report was provided to the Civil Aviation Safety Authority, Textron Aviation, the operator and the pilot.
The submissions from those parties were reviewed and where considered appropriate, the text of the draft report was amended accordingly.
Context
Cockpit voice recorder key events
Table 1 is a list of key events from the accident flight cockpit voice recorder. Events marked with inverted commas (‘’) are automated voice from aircraft systems, such as the ground proximity warning system. Time is from the start of the recording in minutes and seconds.
Table 1: Key events
Time from start
Event
26:10
Pilot reported joining downwind runway 30 Moomba
26:41-26:47
Sound of mechanical movement (consistent with pilot report of lowering landing gear)
27:32
Warning horn activation (consistent with master warning horn frequency, repetition rate and duty cycle) (consistent with pilot report of observing a left engine fire warning)
27:47-end
Propeller speeds separate – one maintains about 1,900 RPM and the other reduces to and then fluctuates around 1,650 RPM (consistent with pilot report of shutting down left engine)
28:17
Warning horn activation (consistent with master warning horn frequency, repetition rate and duty cycle) (consistent with the pilot report of observing activation of the left engine oil pressure and fuel pressure light after the left engine was shutdown)
28:20-28:26
Sound of mechanical movement (consistent with pilot report of raising the landing gear)
Intermittent warning horn activation (likely stall warning, but different frequency to the frequency supplied by the manufacturer (windmilling propeller is slowing down and flaps are retracted))
30:21-30:27
Sound of mechanical movement (consistent with pilot report of lowering the landing gear)
30:25
Sound of momentary impact
30:29-end
Subsequent sounds of impact
Post-accident aircraft information
Following the accident, an inspection of the left engine revealed the fire extinguisher bottle was discharged, but there were no physical indications of a fire. Damage to the left propeller was consistent with rotation of the propeller at impact and the propeller appeared to be in an unfeathered position (Figure 1). Both propeller control levers were at the 1900 RPM setting (Figure 2). The pilot reported that after the aircraft came to rest, they shut off fuel and activated the firewall shutoff valve for the right engine, but were unsure of any other changes they made to switches and controls in the cockpit.
Figure 2: VH-MVL pedestal
Source: Operator, annotated by ATSB
Engine shutdown information
Engine fire emergency procedure
A left engine fire warning is annunciated by the aircraft master warning system, which activates the master warning horn, master warning light and L ENG FIRE light on the master warning panel. The operator’s emergency checklist procedure applicable for an inflight engine fire was the ‘emergency engine shutdown’. The procedure included boxed bold type immediate actions, which were performed from memory. The company procedure was to complete the immediate actions from memory and then reference the checklist to confirm immediate actions were completed before completing the remainder of the actions. The immediate actions for the emergency engine shutdown were:
Condition Lever……FUEL CUT OFF
Prop Lever...…FEATHER
Firewall Shutoff Valve……CLOSED
Fire Extinguisher……ACTUATE (If required)
The pilot reported that their attention was drawn to the warning light in the top left corner of the master warning light panel (location of the left engine fire warning light).[6] They pulled the condition lever, then paused, then closed the firewall shutoff valve and pressed the extinguisher and confirmed it had discharged, all from memory, but there was no time to reference the checklist during the approach.
Propeller autofeathering system
The aircraft was fitted with an automatic feathering system of the propeller, which required the activation of two electrical interlocks for operation. The first interlock is achieved by setting the autofeather switch in the cockpit to ARM. The second interlock is achieved by advancing the power levers to a position which equates to about a 90 per cent N1[7] power setting. When both power levers are advanced to this position, a mechanical activator, connected to each power lever, will close its respective switch and complete the circuit to the high- and low-pressure switches mounted on each engine. This will activate the green AUOTFEATHER advisory lights for the left and right engine in the cockpit.
The autofeather switch is required to be set to ARM in the approach checks. However, the engine fire warning activated after the pilot had set their descent power of about 600–700 foot‑pounds torque[8] (about 75–80 per cent N1) and the left engine was shut down from this power setting. This was below the setting which would activate autofeather when the system is armed.
One engine inoperative performance
The B200 aeroplane flight manual (AFM) recommended procedure to obtain best performance[9] with one engine inoperative is to bank the aircraft 3° to 5° into the operating engine while maintaining a constant heading. The AFM one engine inoperative best rate of climb speed was 121 kt.
Acceleration and climb performance is a function of the excess thrust and power. Therefore, any increase in drag will reduce the aircraft performance. A windmilling propeller can produce a significant amount of drag, which is estimated to be comparable to a parachute canopy of the same area as the propeller disc area (Figure 3).[10]
Figure 3: Windmilling propeller drag
Source: Aerodynamics for naval aviators, annotated by ATSB
The pilot reported that, from their simulator experience, the aircraft performed well with one engine shut down. If an engine was shut down for an approach, then doubling the power on the other engine was sufficient to maintain the correct profile. In the accident flight they initially set about 1,400 foot-pounds torque on the right engine, but then increased the power to the climb power setting of about 2,230 foot-pounds torque. Based on the ground proximity warning height annunciations, the rate of descent from 1,000 ft to 700 ft was about 1,000 ft/min, which then reduced to about 440 ft/min from 500 ft to 200 ft.
In this configuration,[11] there would be a yawing moment to the left produced by asymmetric thrust, (which would be exacerbated by a windmilling left propeller), and a rolling moment to the left from the right propeller slipstream over the right wing. This results in asymmetric lift. The left engine is the critical engine for asymmetric flight.[12] Consequently, full right rudder trim and full right aileron trim were applied by the pilot during the (right) base leg turn.
A right turn flown against these forces will produce more drag than a left turn, which will produce more drag than maintaining a constant heading (Figure 4). The extension of landing gear and flap will also increase drag. The combination of factors which increase drag can lead to a critical condition where the thrust required to maintain the planned flight path exceeds the thrust available.
Figure 4: Thrust required for asymmetric turning flight
Source: Aerodynamics for naval aviators, annotated by ATSB
The Raisbeck Engineering[13] flight manual supplement for the B200 indicated that the minimum control speed - air (VMCA) is 88 kt (indicated airspeed) with the flaps in the approach setting and 91 kt with the flaps retracted.[14] However, there is a flight manual supplement caution that ‘with one-engine either at idle or inoperative, flaps up and propeller windmilling, VMCA may be as high as 108 kt.’ This was inside the approach airspeed range reported by the pilot (100-115 kt).
Training and checking
Pilot’s training
The pilot joined the operator in early 2015. The operator noted that the pilot had a licence for multi-engine aeroplane with endorsements for gas turbine engine and pressurisation, and had flown the Beechcraft C90.[15]
In February 2015, the operator provided the pilot with 26.1 hours of line training on the B200 aircraft, which started on 10 February. They were also provided with two simulator training sessions of 3.7 hours, which included instrument approaches and asymmetric flight exercises. On completion of the second simulator session, the trainer reported that the pilot had ‘very good asymmetric control of aircraft’ and could progress to the instrument proficiency check (IPC). They progressed to a third simulator session of 1.9 hours, which was their IPC on 22 February. During the IPC, the pilot was exposed to an engine fire in the cruise and engine failure after take-off. The testing officer reported that the IPC was ‘completed to a very good standard.’ The pilot’s line check was conducted on a medical flight on 27 February. They were assessed as ‘all ok’ and cleared to line for clinic operations only.
The pilot completed three further flight checks within the operator’s cyclic training and proficiency program (CTPP) between their conversion and the accident flight. In 2015, the pilot conducted two checks in the simulator. In 2016, the pilot conducted their March check in the aircraft and their August check in the simulator.
The simulator field of view for the pilot is less than what is available in the aircraft. Due to the restricted field of view to the sides, the operator assessed it as inappropriate to initiate emergencies in the simulator from a circuit base leg position. Therefore, critical situation emergencies, such as an engine fire indication on approach, were generally initiated on the final approach of an instrument approach. This provided a critical decision-making scenario for the pilot, in which they could initiate the immediate actions while in the final stages of an approach, or alternatively land the aircraft before initiating the immediate actions.
The pilot was exposed to engine fire indications in the cruise and on instrument approach during the CTPP. No knowledge deficiencies were noted with their immediate actions and the four CTPP checks were assessed as completed to the required standard.
Development of the pilot’s training program
The pilot started training with the operator about five months after the introduction of the then new flight crew licencing regulation, Civil Aviation Safety Regulation (CASR) Part 61. Under the previous regulation for flight crew licencing (Civil Aviation Regulation (CAR) 5), the C90 and B200 aircraft were separate class endorsements (BE-90 and BE‑200, respectively). However, with the introduction of CASR Part 61, both aircraft types were included in the ‘multi-engine aeroplane (MEA) class rating’ and did not require type specific ratings.[16]
In January 2015, the Civil Aviation Safety Authority (CASA) published edition 1 of legislative instrument ‘Prescribed aircraft, ratings and variants for CASR Part 61 Instrument 2014’. Paragraph 25 and Schedule 13 of the instrument identified the Beechcraft King Air 90 series and King Air 200/250 series as aircraft types, for which each required initial type-specific training. The training required was in accordance with all the units of competency published in the Part 61 Manual of Standards[17] for the class rating that are relevant for the aircraft type. Although both aircraft may be referred to as King Air series aircraft, they have different Type Acceptance Certificates and therefore are different aircraft types.
The explanatory statement associated with the legislative instrument indicated that the aircraft listed in Schedule 13 were ‘identified as being sufficiently complex or have performance or handling characteristics[18] that warrant initial type-specific training and a flight review in the specific type’. However, the operator was not aware of this instrument or associated explanatory statement at the time of the pilot’s employment. The pilot started training about one month after the publication of the legislative instrument and the operator developed their training program before the pilot started their training.
The operator tailored the pilot’s training program in consideration of the fact that the pilot was trained on the C90 King Air with a previous operator. Consequently, the pilot did not receive the operator’s B200 syllabus of training, as published in their training and checking manual, which included five simulator training sessions (excluding IPC). The operator’s training and checking manual permitted this for a pilot with previous King Air series experience.[19] This was the operator’s understanding of CASR Part 61 after consultation with their respective CASA Flying Operations Inspector.
During the course of the investigation, the ATSB received several responses from different positions within CASA that ‘differences training’[20] was an acceptable approach to transition a pilot from the C90 to the B200. This included the CASA Flying Operations Inspector assigned to the operator and the CASA Flight Standards Branch. On review of the pilot’s training records, the ATSB could not find evidence that the pilot received training in stalling or upper air asymmetric handling in accordance with the operator’s B200 syllabus.
Civil Aviation Safety Regulation 61.747
The relevant regulation to transition a pilot onto a new aircraft within the multi-engine aeroplane class rating system was CASR 61.747 ‘Limitations on exercise of privileges of class ratings in certain aircraft-flight review’. Regulation 61.747 was a competency-based training regime, which required pilots to be trained in all the units of competency in the Part 61 Manual of Standards relevant for the aircraft type, followed by a flight review. Competency based training allows an operator to consider the pilot’s previous qualifications and experience in developing their training and assessment program to demonstrate all the relevant units of competency.
Civil Aviation Advisory Publication 5.23-2(0)
In July 2007, CASA published Civil Aviation Advisory Publication (CAAP) 5.23-2(0) ‘Multi-engine aeroplane operations and training’. CAAP 5.23-2(0) was the second CAAP written on this subject and has been superseded by CAAP 5.23-1(2), published September 2015. The CAAP was written following ‘a number of multi-engine aeroplane accidents caused by aircraft systems mis‑management and loss of control by pilots.’ The CAAP indicated that during training, ‘pilots should be shown all the flight characteristics[21] of the aircraft, and be given adequate time and practice to consolidate their skills.’
The VMCA (minimum control speed – air) demonstration sequence was identified in the CAAP as one of the ‘more important in asymmetric training.’ The instructor should ‘point out the yaw, wing drop and change to attitude.’[22] When a trainee pilot conducts the VMCA exercise, the instructor should ask them to ‘identify when the aircraft starts to yaw and roll’ to determine if they are ‘recognising these conditions early enough.’ The CAAP also discussed the technique to recover from a critical asymmetric situation, with low airspeed near the ground and a windmilling propeller. The risks associated with VMCA training are explained in the CAAP. The operator had managed the risks associated with VMCA training by moving their syllabus of training for the B200 from the aircraft to the simulator.
The CAAP highlighted that it was important for the pilot to recognise and avoid a stall in any aircraft and that instructors must conduct this exercise in multi-engine aeroplanes. Instructors should ‘stress the characteristics and devices that warn the pilot of the stall’ and allow the trainee pilot to ‘experiment with these characteristics and practice them in different configurations and flight situations.’
The references to CAAP 5.23-2(0), published July 2007, were consistent with the guidance in CAAP 5.23-1(2), which was the current CAAP on the subject at the time of the accident.
Flight review
The pilot successfully completed an instrument proficiency check during their initial B200 training, which the operator believed fulfilled the requirements for a flight review. However, CASR 61.747 required the pilot to demonstrate competency in all the units of competency prescribed for the multi-engine aeroplane class rating. A flight review means an assessment of the competency of a flight crew member to perform an activity authorised by the rating. Following advice from CASA Flight Crew Licencing, an instrument proficiency check could fulfil the flight review requirements of CASR 61.747 provided the check included all the units of competency for the multi-engine aeroplane class rating. If units of competency are missed, then the flight review does not comply with the intent of the CASR 61.747 flight review.
Fire detection system
Beech service bulletin 2596
In 1995, Beech Aircraft Corporation[23] issued a service bulletin, SB 2596, which announced the availability of a ‘continuous loop fire and overheat detection system’ as a replacement for the aircraft engine optical fire detection system. This was the most recent design incorporated into production aircraft to improve reliability and maintainability of the engine fire detection system.
The operator reviewed SB 2596 and the decision was made not to incorporate the modification on 15 July 2003 due to cost considerations. An earlier service bulletin, SB 2005, which relocated one of the fire detectors to an area less susceptible to external light and added an additional light shield to the system, was already incorporated in the aircraft from manufacture.
On 10 April 2013, CASA issued an airworthiness bulletin (AWB 26-005) for the Beech B200 Series engine fire detection systems. The purpose of AWB 26-005 was to ‘provide information to operators and maintainers regarding improved engine fire detection systems to avoid false in-flight engine fire indications’.
AWB 26-005 indicated that operators using the optical flame detectors continue to experience false indications of engine fire warnings and that the continuous loop and overheat detection system kits introduced in 1995, through SB 2596, have proven reliable and eliminated false indications. CASA strongly recommended operators install the continuous loop engine fire detection systems to avoid false in-flight fire warnings.
The operator reviewed AWB 26-005 on 12 April 2013, but elected not to incorporate the modification, based on their prior review and decision on SB 2596.
Previous false engine fire warnings
The operator identified four previous reports of false in-flight engine fire warnings recorded in their database for their B200 aircraft fleet, three incidents in 2003 and one in 2005.
A left engine fire warning, which extinguished after about 30 seconds (13 March 2003).
A left engine fire warning, which extinguished after about 30 seconds. A fire detection probe was replaced (22 March 2003).
A left engine fire warning. The pilot conducted the immediate actions. The response recorded in the report was to check the fire detection probes for serviceability (24 April 2003).
A left engine fire warning which activated momentarily on approach. After landing, the warning activated and remained illuminated. The pilot conducted the immediate actions. There was no evidence of fire found and a fire detector was replaced. The warning light activated three times on the return flight. A fault in the wiring harness connector was recorded as the reason (10 July 2005).
The pilot commented that they were aware that the fire detection system was susceptible to false indications due to sunlight entering the engine compartment, but had not previously experienced such an incident. The operator acquired VH-MVL in 1997 and had no prior reported incidents of false fire warnings for that particular aircraft prior to the accident.
Purpose of safety investigations & publishing information
Purpose of safety investigations
The objective of a safety investigation is to enhance transport safety. This is done through:
identifying safety issues and facilitating safety action to address those issues
providing information about occurrences and their associated safety factors to facilitate learning within the transport industry.
It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action.
Terminology
An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue.
Publishing information
Released in accordance with section 25 of the Transport Safety Investigation Act 2003
Ownership of intellectual property rights in this publication
Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia.
Creative Commons licence
With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence.
Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work.
The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau
Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.
On 27 September 2016, at about 0030 Eastern Standard Time (EST), an Avions de Transport Regional ATR42-300 aircraft, registered VH-TOX (Figure 1), was being loaded at Sydney Airport, New South Wales, for a freight charter flight to Brisbane, Queensland.
The freight had arrived from a freight facility where it had been weighed and a load plan completed, with a total freight weight of 2,281 kg.
Prior to loading the freight, a representative from the aircraft operator was unsure of the accuracy of the provided weights and requested ground staff reweigh the freight using calibrated scales at the airport. The measured total weight was 3,215 kg, which was 934 kg more than stated on the load plan.
The flight crew, consisting of a captain and first officer, completed the trim sheet using the actual weights, and the aircraft was within its weight limitations and the allowable centre of gravity envelope. The aircraft operated to Brisbane without incident.
Figure 1: VH-TOX
Source: Daniel Vorbach edited by ATSB
Freight weighing
The freight was weighed at the freight facility using a forklift fitted with scales. Each item of freight was then allocated to a loading position on the aircraft using a spreadsheet from which the aircraft load plan was derived.
The aircraft operator commented that they had previously advised the freight company that forklifts should not be used for the weighing of freight when intended for carriage by air, as they were not sufficiently accurate. The loading supervisor, who was employed by the freight company and responsible for loading the aircraft in accordance with the load plan, was not aware that the weights recorded on the load plan were inaccurate.
The ground handling agreement between the aircraft operator and freight company did not include Sydney as a port of service at the time of the incident. Until recently, the operator’s Sydney operations were based at Bankstown Airport, where calibrated floor scales were used to weigh the freight.
Findings
These findings should not be read as apportioning blame or liability to any particular organisation or individual.
The freight company weighed the freight using inaccurate (forklift) scales, resulting in a discrepancy of 934 kg from the actual freight weight. The aircraft load plan was derived from the inaccurate freight weights.
The aircraft operator discovered the inaccuracy before loading and the aircraft was subsequently loaded within its weight and balance limitations.
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 of port
The operator ceased operations into and out of Sydney Airport and reverted to Bankstown Airport, where calibrated floor scales are used to determine the freight weight for the load plan.
Safety message
Accurate aircraft weight and balance information is vital for the safety of flight, particularly during take-off. Inaccurate weight of freight items can lead to incorrect flight management selections such as power and trim settings. Discrepancies in these can result in reduced take-off performance and incidents such as tail strikes and runway overruns.
The objective of a safety investigation is to enhance transport safety. This is done through:
identifying safety issues and facilitating safety action to address those issues
providing information about occurrences and their associated safety factors to facilitate learning within the transport industry.
It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action.
Terminology
An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue.
Publishing information
Released in accordance with section 25 of the Transport Safety Investigation Act 2003
Ownership of intellectual property rights in this publication
Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia.
Creative Commons licence
With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence.
Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work.
The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau
Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.
On 9 December 2016, a QantasLink Bombardier DHC-8-402, registered VH-LQG (LQG), departed runway 16 left at Sydney Airport. The aircraft was operating a scheduled passenger flight from Sydney to Tamworth, New South Wales. The captain was the pilot monitoring (PM) and the first officer the pilot flying (PF).[1] At the time of departure, windshear conditions existed in the vicinity of Sydney Airport and because of this, the flight crew used normal take-off power.[2]
When LQG departed, an Air New Zealand Boeing 777-219ER, registered ZK-OKF (OKF), operating a scheduled passenger flight from Auckland, New Zealand, was on descent to Sydney from the east, assigned 6,000 ft by the Sydney Approach controller. The projected routes of the aircraft crossed approximately 11 km east of Sydney (Figure 1) and the Approach controller had assigned OKF an altitude of 6,000 ft to provide separation with LQG, who would be assigned 5,000 ft.
At 1407 Eastern Daylight-saving Time (EDT), LQG became airborne and after passing 500 ft, the PF turned the aircraft to an assigned heading of 090. When this turn was made, the flight crew had the go-around (GA) vertical mode selected on the aircraft flight guidance control panel with the altitude select (ALT SEL)[3] mode. After passing the acceleration altitude[4] of 1,100 ft, the PF requested the PM to select the indicated airspeed mode and a speed of 185 kts. The PM did this and then, at 1407:45, they contacted Sydney Departures while the PF engaged the autopilot.
When the PM contacted Sydney Departures, they reported passing 1,900 ft, heading 090 and climbing to an assigned altitude of 3,000 ft. Sydney Departures identified LQG on radar and instructed them to climb to an altitude of 5,000 ft. The PM read back this instruction and the flight crew correctly updated the autopilot with the new altitude and engaged the ALT SEL mode.
At 1408:12, as the aircraft climbed through 2,600 ft, Sydney Departures instructed LQG to track direct to waypoint KAMBA.[5] The position was entered into the flight management system and the autopilot was set to the lateral navigation mode. The aircraft then commenced turning left towards KAMBA.
At 1408:38, as the aircraft climbed through 3,800 ft (Figure 1), Sydney Departures advised LQG there would be a short delay at 5,000 ft due to traffic above them. This was acknowledged by the PM.
Figure 1: Disposition of aircraft when LQG was passing 3,800 ft direct KAMBA and showing the projected point of crossing.
Source: Airservices Australia, modified by the ATSB
Also, around this time, with the aircraft now tracking to KAMBA, the PF increased the airspeed setting from 185 knots to 210 knots. Almost simultaneously, the autopilot altitude mode changed to capture the assigned altitude.
The adjustment of the airspeed setting, while the autopilot was in altitude capture mode, resulted in the autopilot reverting from altitude capture mode to pitch mode, which meant the autopilot would now not stop the aircraft climb at 5,000ft.
Consequently, the PF decided to disconnect the autopilot and commenced hand flying the aircraft. They pitched[6] the aircraft nose down, to reduce the rate of climb, and simultaneously the PM selected the autopilot indicated airspeed and ALT SEL modes. Once these modes were selected, the PF attempted to reconnect the autopilot so the aircraft would maintain 5,000 ft. Before ensuring the autopilot had reconnected, they became aware of the conflicting traffic (OKF) and obtained its position by referencing the traffic alert and collision avoidance system (TCAS)[7] display. During this time, as the autopilot had not been correctly reconnected, the aircraft continued to climb.
After sighting OKF, the PF looked back at the aircraft instrumentation and observed the aircraft had climbed through 5,000 ft. This coincided with an altitude alert from the autopilot, which indicated that the selected altitude was exceeded. The PF responded by again pitching the aircraft nose down to stop the climb and return the aircraft to 5,000 ft. The maximum altitude LQG reached was 5,600 ft[8] before the aircraft began to descend.
Prior to the altitude excursion, the air traffic control system presented a short-term conflict alert (STCA), to both the Sydney Approach and Departures controllers. In response to the STCA, both controllers monitored the altitude of LQG to ensure the aircraft would maintain 5,000 ft. When the Sydney Departures controller observed LQG continue to climb, they issued the flight crew a safety alert,[9] requested confirmation that the aircraft was maintaining their assigned altitude and issued them a heading instruction to turn away from OKF. The Sydney Approach controller issued the flight crew of OKF a safety alert and instructed them to stop their rate of descent. In response, the flight crew of OKF advised they would level out and reported they were over the top of LQG and would be able to sight them again shortly. During the conflict, the lowest altitude OKF reached was 6,800 ft.
Separation Standards
The Sydney Approach and Departures controllers had anticipated that LQG and OKF would pass with less than the required 3 NM (5.6 km) surveillance separation between the aircraft. LQG subsequently passed approximately 0.5 NM (1 km) behind OKF. As surveillance separation did not exist, 1,000 ft vertical separation was required. In applying vertical separation, using pressure derived altitude information, tolerances need to be applied. When these tolerances are considered, the 1,200 ft displacement between the aircraft was not adequate to apply vertical separation. Consequently, the level excursion by LQG resulted in a loss of prescribed separation.
Operation of Autopilot
In multi-crew operations, standard operating procedures are established to support the principles of crew resource management (CRM). This includes defining the roles of the PF and PM in relation to autopilot selections. The captain of LQG reported that if the autopilot is engaged, the PF will make the autopilot selections. If the PF is hand flying the aircraft, the PM will make the selections, under the direction of the PF. In both sets of circumstances, visual and verbal cross-checks are made to help identify any potential errors.
Pilot monitoring comments:
After they had selected the correct modes, they believed the PF had reconnected the autopilot. At this time, their attention was divided between managing other radio transmissions and monitoring the PF’s actions.
The requirement to maintain 5,000 ft on departure was received regularly and something they monitored closely. In normal circumstances, the autopilot would remain engaged.
The PM advised that they should have been monitoring the PF’s actions more closely.
Pilot flying comments:
They were aware that when the autopilot mode changed to altitude capture, as they used the speed control, the autopilot mode could change to pitch. So, when this occurred, they disconnected the autopilot rather than concentrating on changing the modes with a high rate of climb close to the required altitude.
They thought they had reconnected the autopilot after the PM had reset the modes, but were distracted by looking outside the aircraft for the conflicting traffic and did not confirm the autopilot had reconnected.
Safety analysis
When the PF initiated the speed increase to 210 knots, the autopilot had not commenced capturing the assigned altitude. The speed increase at this stage of flight was reported as consistent with company practice of increasing speed when tracking towards the intended destination.
As the PF increased speed, the autopilot started to capture the assigned altitude. These near simultaneous events resulted in the autopilot reverting to pitch mode. The potential for the autopilot to behave in this manner was known to the flight crew. It is probable that the altitude capture occurred earlier than expected, due to the aircraft’s rate of climb being unusually high. The selection of normal take-off power on departure contributed to this high rate of climb.
The PF became concerned that the autopilot was not correctly configured to maintain the assigned altitude and disconnected the autopilot to hand fly the aircraft. After the PM had selected the correct autopilot modes, the PF, believing the autopilot would successfully maintain the aircraft at 5,000 ft, decided to reconnect the autopilot. They attempted to do this but the action was not successful. The PF did not realise this and the PM did not correctly confirm the status of the autopilot.
It was probable that the PF was distracted with looking for the conflicting traffic, rather than ensuring they had successfully reconnected the autopilot.
The loss of separation subsequently occurred after LQG did not maintain 5,000ft on a track that conflicted with OKF.
Findings
These findings should not be read as apportioning blame or liability to any particular organisation or individual.
The PF increased the aircraft speed at approximately the same time as the autopilot commenced capturing the selected altitude. This resulted in the autopilot mode changing and influenced the PF’s decision to disconnect the autopilot.
The PF did not engage the autopilot correctly and became distracted before ensuring it was connected, resulting in the aircraft climbing through the assigned level. The PM was also not aware that the autopilot had not been correctly reconnected.
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 action:
Further training was provided to both the PM and PF in the areas of situational awareness, human factors and operational decision-making during high workload scenarios, including a review of aircraft automation technology and procedures. The crew members were also required to demonstrate competency prior to return to flying duties.
Safety message
Maintaining separation in high traffic terminal areas, such as Sydney, requires that flight crews strictly adhere to air traffic control instructions. As highlighted in this occurrence, any deviation has the potential to reduce safety margins.
During this occurrence, the interactions between the crewmembers were not effective in responding and managing the encountered threats and highlights the importance of effective CRM.
CRM is described as the practical application of all aspects of human factors including situational awareness, decision-making, threat and error management, team cooperation and communication.
One important aspect of effective CRM, is related to successful monitoring of aircraft systems and ensuring crewmembers actively cross check each other’s actions. These skills can be improved through standard operating procedures and increased emphasis and practice.
Key flight crew monitoring principles include:
be technically proficient
keep all team members informed
ensure the task is understood, supervised and accomplished
The objective of a safety investigation is to enhance transport safety. This is done through:
identifying safety issues and facilitating safety action to address those issues
providing information about occurrences and their associated safety factors to facilitate learning within the transport industry.
It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action.
Terminology
An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue.
Publishing information
Released in accordance with section 25 of the Transport Safety Investigation Act 2003
Ownership of intellectual property rights in this publication
Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia.
Creative Commons licence
With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence.
Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work.
The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau
Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.
On 7 December 2016, a Boeing 737-8FE aircraft, registered VH-YFT (YFT) was parked on bay 3 (Figure 1) at Hobart Airport, Tasmania, as the crew prepared to conduct Virgin Australia flight VA1531 to Sydney, New South Wales. The flight crew consisted of a captain and first officer, and a check captain seated in the jump seat between them.
Figure 1: Hobart Airport – aerodrome diagram
Source: Airservices Australia annotated by ATSB
At about 0945 Eastern Daylight-saving Time (EDT), another Virgin Australia Boeing 737-8FE aircraft, registered VH-VUP (VUP), landed at Hobart Airport and parked on bay 2, adjacent to and north of YFT. The bays required that the aircraft departs using a power-out taxi[1], as there were no tug facilities available at Hobart Airport.
By 0950, the flight crew of YFT had received the final load sheet[2] electronically via the aircraft communications addressing and reporting system (ACARS). Due to an issue with printing a copy of the load sheet on the ACARS printer, the crew requested, and received, a paper copy of the load sheet from the dispatcher.[3] This issue caused a slight delay in pre-flight preparations. After starting the engines, the captain gave the dispatcher the instruction to disconnect their headset from the aircraft, which the dispatcher did, then exchanged thumbs up to indicate all was clear. The dispatcher then walked to the left wingtip of the parked aircraft (VUP) and stood with their arms out and thumbs up to indicate YFT was clear of obstacles, particularly the wingtip of VUP.
At 1012:12, the first officer of YFT contacted the Hobart surface movement controller (SMC) on Ground frequency and requested a clearance to taxi. The SMC then instructed the crew of an Airbus A320 aircraft that had commenced taxiing from bay 4, to vacate the apron area via taxiway H (Figure 2).
Figure 2: YFT starts taxiing from bay 3 at Hobart Airport
Source: Airport operator annotated by ATSB
The SMC then advised the crew of YFT that the A320 on their ‘left hand side’ was taxiing out via H and that they were to follow that aircraft via H (and D) to holding point D for runway 30. The first officer read back ‘follow Jetstar A320 behind, behind him via hotel holding point delta runway 30’. At about 1013, the captain commenced turning the aircraft to the right, out of the bay, with the nose wheels just inside the marked lead-out line (Figure 3).
Figure 3: Hobart apron area showing the lead-out line on bay 3
Source: Google earth annotated by ATSB
At that time, another A320 aircraft had landed and was taxiing in towards the parking bays from the north. During the initial turn out of the parking position, the captain became aware of the inbound A320 on taxiway A and became uncertain as to which A320 the controller had instructed them to follow, and whether the inbound A320 would taxi past them via taxiway F. The first officer had also seen the A320 taxiing down A towards F and pointed it out to the captain.
The captain elected to stop the aircraft and clarify their taxi clearance. YFT stopped part way through the turn, about 90° from its parked position (Figure 4). At that time, the nose wheels were inside the lead-out line, and the aircraft was pointing towards the left wingtip of VUP.
Figure 4: YFT stopped taxiing during the turn out of bay 3
Source: Airport operator annotated by ATSB
The ramp supervisor[4] was at the far side of the parked aircraft (VUP) preparing it for departure, when YFT stopped. The ramp supervisor saw that YFT had stopped during the turn out, which was unusual, therefore moved to a position near the dispatcher, who was at the left wingtip of VUP, to where they could communicate with the flight crew if required and have line of sight to check for wingtip clearance between the two aircraft (Figure 5).
Figure 5: VUP parked on bay 2 with ground crew marshalling and A320 inbound
Source: Airport operator annotated by ATSB
When YFT had stopped, the flight crew noticed that they had inadvertently omitted to write the automatic terminal information service (ATIS)[5] reference letter on their take-off data card. The first officer switched their radio to the appropriate frequency to listen to the ATIS, while the captain temporarily took over responsibility for communications with air traffic control (ATC) on Ground frequency.
At 1014:00, after seeing YFT stop during the turn, the SMC instructed the crew of YFT to ‘continue to taxi via taxiway H, you are number one to inbound traffic and the other traffic is well clear’. About 20 seconds later, after confirming the clearance with the captain (and switching the radio back from the ATIS to the Ground frequency), the first officer acknowledged the clearance with the call sign ‘Velocity 1531’.
By the time the first officer acknowledged the clearance, the captain had recommenced taxiing, while watching the A320 on taxiway A to make sure that it was going to hold its position. After stopping, the captain removed their hand from the tiller, which caused the nose wheels of YFT to centre. Therefore, the aircraft moved forwards in a near straight line for about 2 seconds and crossed the lead-out line, before the right turn resumed.
As the aircraft recommenced taxiing, the dispatcher initially observed the wingtips of the two aircraft clear each other. However, as YFT then tracked towards the tail of the parked aircraft as it started to turn, the ramp supervisor assessed that a collision between the left wingtip of YFT and left horizontal stabiliser of VUP was imminent. The ramp supervisor commented that they then lowered their arms towards a crossed position to show that clearance between the two aircraft was reducing,[6] and attempted (unsuccessfully) to make eye contact with the flight crew (Figure 6).
Figure 6: Collision imminent
Source: Airport operator annotated by ATSB
About 30 seconds after recommencing the taxi, as YFT continued to turn, the left wingtip collided with the horizontal stabiliser (tailplane) of VUP (Figure 7).
Figure 7: Contact between YFT left winglet and VUP left horizontal stabiliser
Source: Airport operator annotated by ATSB
The winglet of YFT was damaged (Figure 8) as was the horizontal stabiliser of VUP (Figure 9). No one was injured.
Figure 8: Damage to YFT left winglet
Source: Aircraft operator
Figure 9: Damage to VUP left horizontal stabiliser
Source: Aircraft operator
Safety analysis
Parking bays
The Hobart Airport operator reported that the bays were surveyed regularly to ensure they met the required standards. The airport operator constructed a schematic diagram of the aircraft’s taxi path from the CCTV footage and the aircraft dimensions on the surveyed apron markings (Figure 10).
The flight crew commented that the design standard for the parking bays meant that they were far too close to be comfortably safe to conduct a power-out taxi when there is an aircraft in the adjacent bay. Furthermore, a bit more spacing between the bays may prevent a similar incident occurring. The captain also commented that consideration of operational acceptability criteria, in addition to technical design specifications, prior to the commissioning of any parking bay and its associated taxi guidance line would facilitate required changes to the bay and mitigate additional threats peculiar to the local environment.
The captain commented that the (power-out) bays in Hobart are not aligned at right angles to taxiway H. This tends to give a false sense of being clear of adjacent aircraft once the cockpit is well past the aircraft and heading towards taxiway H, as the wingtips are so far behind the flight deck and outside the normal viewing arc of the pilots.
Figure 10: Airport survey markings showing B737 aircraft taxi track with nose wheel on lead-out line (left) and approximate incident taxi path (right)
Source: Airport operator
Position of VUP
VUP was parked with the nose wheels approximately 450 mm aft of the stop mark on bay 2, and the main landing gear was offset longitudinally (relative to the aircraft’s heading on the bay) about 380 mm left of the bay centreline. These were well within allowed tolerances and the aircraft was assessed by ground crew to be parked in the correct position. The crew of VUP had been guided to the parking position by ground marshals.
However, the position of VUP’s tail slightly left of centreline and aft (measured after the accident), reduced the available clearance between the two aircraft.
Turning geometry
When the aircraft stopped, the nose wheels straightened, and the aircraft subsequently taxied outside the marked turning circle.
When the captain releases the tiller on a Boeing 737 aircraft[7] during taxi, it will tend to centre the nose-wheel steering and straighten the nose wheels. When the aircraft then starts to move, the captain cannot immediately turn the nose-wheel steering before the aircraft moves without considerable use of thrust and excessive load on the nose landing gear. As the aircraft starts to move forwards, the captain turns the tiller in the desired direction and the nose wheels will start to turn the aircraft.
When YFT stopped, the nose wheels were inside the lead-out line. If the nose wheels track on (or inside) the lead-out line, the wingtip will clear a correctly parked aircraft on the adjacent bay, but it is necessary to keep a continuous turn going. The check captain commented that if you stop the aircraft, particularly if it is heavy, a significant amount of thrust is required to then keep the aircraft on the line. The captain commented that they used caution with the thrust setting because of passengers boarding the aircraft on the adjacent bay. The check captain also stated that there was not a lot of manoeuvring room with ‘power-out’ bays. There is a risk that the aircraft has to go straight ahead for 2-3 m to get the turn going again and there is no allowance made for that in the geometry of the bay.
The captain commented that there is an inherent error in determining where the nose wheel is tracking in relation to a taxi guidance line, in the Boeing 737, during turns. The nose wheel is behind and laterally offset from the captain’s seating position. As such, its position in relation to the line can only be estimated. On power-out bays, flight crew cannot see the position of the aircraft on the lead-out line at any time.
After stopping, the captain could no longer see the lead-out line, which was then beneath and behind the cockpit. The aircraft taxied forward across the lead-out for about 1–2 seconds then turned to the right towards the H taxiway line. There was no marked line connecting the lead-out line with taxiway H.
Ground crew interpretation of taxi track
When the aircraft stopped, the dispatcher noticed that the nose wheels were inside the line, which was normally an indication that the aircraft would stay well clear of an aircraft parked on bay 2. The aircraft then proceeded for about 2 seconds at an angle that was not normal, and both the ramp supervisor and the dispatcher thought the aircraft may have been heading towards taxiway A via the exit (F) behind bay 2 rather than continuing to turn to the right and along the normal path onto taxiway H.
The dispatcher reported that they were not initially concerned about the aircraft’s track, because a bit of momentum was needed to turn the aircraft and get moving. When the wingtip of YFT taxied clear of the wingtip of VUP where the dispatcher was standing, they assumed the aircraft would continue turning and exit the bay, but instead it kept going towards the parked aircraft, which they commented was very unusual.
Communication between ground crew and flight crew
In accordance with normal procedures, the dispatcher unplugged their radio connection to the flight crew before the aircraft commenced taxiing.
The dispatcher commented that they were unsure as to why the aircraft had stopped during the turn, but assumed it was because the flight crew were communicating with ATC. The ground crew radios are not on the ATC frequency and therefore they cannot hear transmissions between ATC and flight crew.
When the aircraft stopped, the ramp supervisor moved to where they could see if the flight crew flashed the nose-wheel lights to indicate a reconnect (of ground-air crew radio communications) was required, but they did not. There were also no hand signals from the flight crew to indicate they needed to reconnect. The ramp supervisor is the only person in the ground crew with a ground-to-air licenced, hand-held radio, so they wanted to get into position to communicate with the flight crew if they requested a reconnect.
As the aircraft continued its turn off the bay, YFT’s wingtip clearance was decreasing due to its proximity to the tailplane of VUP, although it had safely cleared the wingtip of VUP. The dispatcher was then no longer in sight of the flight crew. The ramp supervisor was unable to make eye contact with the captain (seated in the left seat) and commented that the captain appeared to be looking directly forwards.
The ramp supervisor commented that they lowered their arms towards a crossed position to indicate reducing clearance, but that action was not apparent on the CCTV footage of the accident. The check captain commented that lowering of the arms to the crossed position as stated by the ramp supervisor was not shown in the operator’s manual as a procedure to show reduced wing tip clearance.
According to the manual, the correct signal for requiring the aircraft to stop was ‘arms repeatedly crossed above head (the rapidity of the arm movement should be related to the urgency of the stop (i.e. the faster the movement, the quicker the stop)’.
The captain commented that they had seen the thumbs up from the wing walker at the wingtip of the parked aircraft (the dispatcher) and the wing walker near the tailplane of the parked aircraft (the ramp supervisor). They were the only signals the captain sighted and assumed therefore that they were clear of the parked aircraft. If there was any doubt about their clearance from the parked aircraft, they would contact ground staff via radio on their company operations frequency and request assistance, but they did not have any doubt. They had received the all clear signal from the ground crew and thought that they were clear of the parked aircraft and safe to continue.
The captain commented that it would be better to have verbal communication with the marshallers all the way out of the parking bay to have immediate communication if the clearance is insufficient. A verbal warning would be an immediate trigger to stop.
Training
The check captain commented that they consider the turning bays at Hobart to be tight. When training new captains, they always encourage them to ensure that they apply sufficient tiller during the turn out, and that sufficient thrust is applied to keep the aircraft turning. In addition, they suggest using the technique of using slightly more thrust on the outside engine to assist in keeping the aircraft turning.
The check captain also stated that there was no standard procedure in the company for training captains to taxi the aircraft. Training captains instil the importance of using a minimum radius turn out of the bay, appropriate power application and tiller technique, and instruct how to go about requesting assistance with marshaller guidance. Captains are instructed on the visual (hand) signals and where there is any doubt about clearance, to rely on the marshaller and keep a good lookout. If unsure of the clearance from any obstacle, they should stop, but in a turn, it is also important to keep the turn going – if you do stop you potentially have a problem.
When taxiing out of a power-out bay, they try to turn inside the lead-out line to ensure adequate clearance.
Role of ground crew
The operator commented that at the time of the incident, although provision of ‘wing-walkers’ was included in the ground handling contract between the aircraft operator and ground handling provider at Hobart Airport, the ground personnel were not specifically trained in wing walking. The dispatcher and ramp supervisor had proactively positioned themselves at the wingtip and horizontal stabiliser of VUP to assist the flight crew in maintaining clearance between the two aircraft. Wing walking or marshalling was normal procedure for the ground crew at Hobart Airport and both ground crewmembers had substantial experience in doing so.
Once the wingtip of YFT had passed the wingtip of VUP, the dispatcher’s responsibility was over because the next marshaller (ramp supervisor) was in line and the dispatcher was then out of line of sight of the flight deck. There was not usually a marshaller positioned beyond the wingtip.
The dispatcher commented that normally once the aircraft was clear from that position on the wingtip, the dispatcher would give a salute or wave to the captain and they would acknowledge with a wave, but that did not happen on this occasion. The dispatcher commented that the captain appeared to be looking straight ahead towards the exit, or they may have been focused on the marshaller ahead (the ramp supervisor).
Attention and time pressure
The captain initially got the thumbs up from the dispatcher and the ramp supervisor. Immediately before the collision, the captain’s attention was on the inbound A320, and they did not see any indication from the ground crew of reducing clearance with VUP (nor was there any evidence of such on the CCTV footage).
The captain commented that during the turn out, their attention was divided between the wing walker, watching where the aircraft was going, listening to ATC, communicating with the first officer, maintaining situational awareness and being aware of other traffic in the area.
The captain also commented that they[8] had to rise at 0345 to commute to Sydney Airport for the flight and had not slept particularly well as the flight was a line check. There was some pressure to perform well having a check captain in the jump seat. However, the captain felt fit to operate the flight and did not feel tired.
While waiting for the final load sheet to come out on the aircraft communications addressing and reporting system (ACARS), they had a problem with the ACARS printer and had to unjam it as the scheduled departure time was approaching. They requested a hard copy of the load sheet from the dispatcher but were also able to get the printer fixed and printed the load sheet from the ACARS. This caused them a slight delay and they were ready to go about 2 minutes late (scheduled departure was 1010 and they released brakes at 1013). This created some time pressure.
Clearance and traffic disposition
The presence of two A320s led the captain to doubt their taxi clearance after they started taxiing. The operator commented that the first officer’s read back of the taxi clearance, where they stated the A320 ‘behind’ rather than to their left, may also have affected the captain’s perception of which of the two A320s they were to follow. Once the aircraft started to turn, the captain could not see the A320 taxiing out (via H) but was concerned about the one inbound. The captain wanted to confirm that the inbound aircraft was going to stop.
Normally the captain would clarify the clearance with the first officer, but the first officer was listening to the ATIS at the time.
Findings
These findings should not be read as apportioning blame or liability to any particular organisation or individual.
When the captain became aware of the incoming A320, they became uncertain of their clearance and stopped the aircraft to clarify.
The aircraft taxied outside the marked lead-out line after stopping and without the application of sufficiently increased thrust or tiller input this resulted in insufficient clearance from the parked aircraft. The captain was unable to see the aircraft’s position relative to the lead-out line after stopping and the line did not continue to intersect the taxiway ahead of the aircraft.
The bays were marked according to the standards, but the standards probably did not allow sufficient margin for non-normal situations, such as stopping during the turn.
There was no documented procedure for either flight or ground crew to follow in the case of an aircraft stopping during the turn or crossing the lead-out line.
The operator did not have a standard training syllabus or assessment criteria for teaching captains to taxi the aircraft.
There was no direct means of verbal communication between ground marshallers and the flight deck once the aircraft started taxiing, although the crew could contact the movement coordinator if required.
Wing walkers should remain in sight of the flight crew, but the captain did not see the ramp supervisor signal to indicate reducing clearance between the two aircraft. The captain’s attention was to the incoming A320.
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.
Aircraft operator
As a result of this occurrence, the aircraft operator has advised the ATSB that they are taking the following safety actions:
Flight crew operational notice
The aircraft operator issued a flight crew operational notice (FCON)[9] which stated that:
When taxiing out of power-out bay, crew shall ensure the aircraft maintains the apron lead-out line until:
the end of the lead-out line; or
the lead-out line joins a taxiway centreline.
This may involve an exit turn of more than 180 degrees to assure clearance from adjoining bays.
Should the aircraft be stopped before completion of the entire turn to exit the apron, caution should be made when re-initiating movement to ensure the above requirements are maintained.
If at any time aircraft clearance cannot be assured, the aircraft should cease taxiing and request assistance.
Training and checking notice
The aircraft operator also issued a training and checking notice (TCN) that stated ‘All Check Captains and Training Captains are requested to ensure that wingtip geometry, turn markings, turn procedures and hazards are well understood by flight crew during line training and recurrent line checks’.
Flight crew information bulletin
The aircraft operator published a flight crew information bulletin (FCIB) for educational and standardisation purposes titled Wingtip Clearance Hazard and applicable to Boeing 737 aircraft. The FCIB included information about taxiing in accordance with lead-out lines, appropriate use of ground crew, images of Hobart and other airports used by the operator, and wing and tail turning geometry for the aircraft.
The FCIB stated:
In summary, it is recommended that taxi guidance lines be adhered to, whenever practical. Continued vigilance should be employed by crews in the monitoring of obstacles during ground manoeuvring.
If there is any doubt whatsoever regarding wingtip clearance, STOP and seek guidance.
Safety message
This incident highlights the importance of aircraft operators conducting a thorough risk assessment where ground movement is confined, particularly movements involving congested power-out bays. Effective risk assessments ensure that hazards are clearly identified and well understood, and that the associated risks are appropriately managed.
To manage clearance in congested areas, communication tools between ground and flight crew should be used where possible when ground crew are providing marshalling or wing walking assistance. Hand signals rely on constant visual contact, which cannot be guaranteed. Appropriate training of ground crew regarding the use of standard hand signals is required to ensure mutual understanding and communication between flight and ground crew.
Where possible, airport authorities should consider additional margins to accommodate unusual or irregular circumstances during taxiing.
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
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