Safety summary

What happened

On 7 April 2017, a Qantas Airways Boeing 747-438, registered VH-OJU, was operated as scheduled passenger flight QF29 from Melbourne, Victoria, to Hong Kong International Airport, in the Hong Kong Special Administrative Region of the People's Republic of China. On board were 17 crew and 347 passengers.

While descending toward Hong Kong International Airport, air traffic control instructed the flight crew to hold at waypoint BETTY.

When entering the holding pattern, the aircraft’s aerodynamic stall warning stick shaker activated a number of times and the aircraft experienced multiple oscillations of pitch angle and vertical acceleration. During the upset, passengers and cabin crewmembers struck the cabin ceiling and furnishings.

A lavatory smoke alarm later activated, however, the cabin crew determined the smoke alarm to be false and silenced the alarm. The aircraft landed at Hong Kong International Airport without further incident. Four cabin crewmembers and two passengers suffered minor injuries during the incident and the aircraft cabin sustained minor damage.

What the ATSB found

The ATSB found that while planning for the descent, the flight crew overwrote the flight management computer provided hold speed. After receiving a higher than expected hold level, the flight crew did not identify the need to re-evaluate the hold speed. This was likely because they were not aware of a need to do so, nor were they aware that there was a higher hold speed requirement above FL 200. Prior to entering the hold, the speed reduced below both the selected and minimum manoeuvring speeds. The crew did not identify the low speed as their focus was on other operational matters.

The ATSB also found that due to a desire to remain within the holding pattern and a concern regarding the pitch up moment of a large engine power increase, the pilot flying attempted to arrest the rate of descent prior to completing the approach to stall actions. In addition, the pilot monitoring did not identify and call out the incomplete actions. This resulted in further stall warning stick shaker activations and pilot induced oscillations that resulted in minor injuries to cabin crewmembers and passengers.

Additionally, the operator provided limited guidance for hold speed calculation and stall recovery techniques at high altitudes or with engine power above idle. This in turn limited the ability of crew to retain the necessary manual handling skills for the recovery.

What’s been done

In response to the occurrence, the operator updated flight crew training lesson plans and commenced retraining of flight crew in more complex stall recovery events. The operator also amended the Boeing 747-400, 787 and 737 flight crew training manuals and updated flight crew ground school lesson plans to ensure standardisation of training.

Safety message

Balancing competing attention or decision demands can interrupt trained flight crew responses leading to procedures not being completed in full, particularly so if flight crews are not receiving comprehensive and regular training in the application of these skills.

Comprehensive theory and practical training can ensure that flight crews have a complete understanding of aircraft systems and maintain effective manual handling skills. This training should provide flight crew with the knowledge to correctly configure the aircraft’s automatic flight systems and manual handling skills to respond adequately to in-flight upsets.

The occurrence

On 7 April 2017, a Qantas Airways Boeing 747-438, registered VH-OJU, operated as scheduled passenger flight QF29 from Melbourne, Victoria, to Hong Kong International Airport, in the Hong Kong Special Administrative Region of the People's Republic of China. On board were 17 crew and 347 passengers. The captain operated as pilot flying and the first officer as pilot monitoring.^[1]

At about 1745 Hong Kong Time (HKT),^[2] in daylight, the aircraft descended toward waypoint^[3] BETTY (Figure 1) with the autopilot engaged in lateral navigation (LNAV) and vertical navigation (VNAV) modes,^[4] and the autothrottle engaged. As the aircraft descended from flight level (FL) 300,^[5] the customer service manager (CSM) (following direction from the flight crew) advised the passengers to prepare for landing and fasten seatbelts, however, at this time, the fasten seatbelt sign was not illuminated.

Figure 1: BETTY 2A standard arrival route chart extract

The figure shows the position of the BETTY hold along with the inbound track of VH-OJU. Source:  Hong Kong CAD, annotated by ATSB

The flight crew anticipated that air traffic control (ATC) would direct them to hold at waypoint BETTY, at about FL 150 to FL 160, and they used the aircraft flight management computer (FMC) to plan for the hold. The FMC provided a calculated target hold speed (Figure 2) of 223 kt at FL156, which was the FMC-calculated crossing level at waypoint BETTY. The crew verified this calculated speed by comparing it to the flaps-up manoeuvring speed (see Hold speed below) using a heuristic of adding 80 kt to the flaps-30 landing reference speed of 143 kt, resulting in 223 kt.^[6] The captain asked the first officer to input 225 kt above FL 150 as the target hold speed.

Figure 2: Example of the FMC route hold page with the target speed and the best speed highlighted

The FMC route hold page, showing the best speed indication (representative and not indicating incident data).
Source: Operator, annotated by ATSB

Prior to crossing BETTY, ATC descended the aircraft from FL 300 in steps. This positioned the aircraft above the planned descent profile. As the aircraft approached BETTY at FL 230, ATC instructed the flight crew to descend to FL 220 and hold at BETTY. The flight crew then entered 22,000 ft in the autopilot altitude selection window, which directed the FMC VNAV function to level at FL 220. However, the flight crew did not adjust the target hold speed in alignment with the higher-than-expected hold level. The flight crew later reported that they were not aware of a higher speed requirement for holding above FL 200.

At this time, service in the aircraft’s forward cabin had been completed. The CSM, along with other cabin crewmembers from the forward sections, moved towards the rear of the aircraft to assist with preparing the rear cabin for landing. This led to more cabin crewmembers than normal being in the rear cabin.

While descending towards BETTY, the aircraft’s speed reduced below both the target speed of 225 kt and the minimum manoeuvring speed, which was indicated on the pilot’s flight display (PFD) as the top of an amber band (see Figure 5 in Operational information below).

At this time, the captain was reviewing the Hong Kong approach documentation and the first officer was looking out to the right of the aircraft in an attempt to identify aircraft traffic in the vicinity of the holding pattern. As a result, the captain and first officer did not identify the reducing speed. The second officer later reported observing the speed reducing close to, but not below, the selected speed of 225 kt.

At 1747:42, the flight data showed that the aircraft crossed BETTY at a speed of 222 kt, while descending through FL 227, with engine power at idle. The aircraft then began a right turn to enter the holding pattern. While still turning, the aircraft descended through FL 222 and the pitch angle^[7] began to increase as the autopilot prepared to level the aircraft at FL 220. Three seconds later, at 1747:59, the aircraft’s bank angle increased to a maximum of 32 degrees, its speed reduced to 220 kt and the aircraft began experiencing pre-aerodynamic stall buffeting.^[8] The flight crew reported the stick shaker also activated, although the recorded flight data does not show a stick shaker activation at this time. The captain also later commented that he did not recall seeing the stall warning indication approaching the indicated speed on the PFD (see Stall warning activation speed below).

After the onset of the buffeting, flight data shows the autopilot was disconnected, most likely by the captain. The captain then pushed forward on the control column to reduce the aircraft’s pitch angle and reduced the aircraft’s bank angle. Due to a desire to remain within the protected airspace of the holding pattern, the captain did not roll to wings level as recommended by the operator’s approach to stall recovery procedure (see Figure 7 in Stall warning recovery procedure below). The captain also did not disconnect the autothrottle as required by the procedure, however, he manually advanced the thrust levers. Due to concerns regarding an excessive increase in pitch resulting from a large power increase,^[9] he increased the engine power from about 37 per cent to about 73 per cent N1.^[10]

The first officer observed the captain’s actions and was satisfied that the appropriate actions had been undertaken. He did not identify, and therefore did not call out, that the stall recovery procedure had not been completed. As a result of the captain’s actions, the aircraft accelerated slightly, the buffeting stopped and the aircraft continued descending.

Six seconds later, at 1748:05, the aircraft descended through FL 220, the speed increased to the selected 223 kt and the thrust reduced. At the same time, the captain pulled back on the control column to increase the pitch angle to prevent further descent. Four seconds later, the stick shaker activated. In response, the captain again pushed forward on the control column to reduce the aircraft’s pitch angle and increased thrust slightly. The stick shaker deactivated and the aircraft continued descending. As the aircraft descended through FL 218, the captain pulled back on the control column to increase the pitch angle and the stick shaker again activated. In response, the captain again pushed forward on the control column to reduce pitch angle and the stick shaker deactivated. At about this time, the seatbelt sign was selected on.

Over the next nine seconds, the captain disengaged the autothrottle, increased power to greater than 90 per cent N1 and increased the selected speed to 252 kt. The oscillations reduced and the aircraft continued accelerating.

At 1748:31, the aircraft levelled off at FL 214 and the speed was increasing through 238 kt toward the selected speed. At about this time, the first officer alerted the captain that the aircraft had descended below the cleared level. In response, the captain asked the first officer to request a lower level from ATC, who immediately cleared the flight crew to descend to FL 210. The autopilot was then re-engaged in VNAV and LNAV modes with 21,000 ft in the altitude window of the mode control panel. However, as the altitude selector was not activated, 22,000 ft remained as the commanded altitude and the aircraft commenced climbing to FL 220.

As the aircraft climbed, ATC contacted the flight crew to confirm that they were descending to FL 210. The flight crew confirmed that they were descending and activated the 21,000 ft altitude selection. The aircraft then descended to FL 210 and re-joined the BETTY holding pattern. During the event, there was no loss of separation with any aircraft.

During the pilot-induced oscillations, the CSM, who was standing in the left aisle in the vicinity of rows 63 and 64 (Figure 3), struck the cabin ceiling before falling on a seat armrest, sustaining injuries. Five other cabin crewmembers also struck the ceiling, with three sustaining injuries. A passenger located in an L5 lavatory struck the cabin ceiling landing on the lavatory seat, resulting in minor injuries and damage to the lavatory fittings. A passenger in seat 63C who did not have her seatbelt fastened, was also injured.

Figure 3: VH-OJU main deck layout

The figure shows the aircraft main deck layout. The locations of the injured cabin crewmembers, injured passengers and L5 and R5 lavatories are identified. Source: Operator

After the aircraft stabilised, the CSM was alerted to the injured passenger in the L5 lavatory. The CSM provided assistance to this passenger and then conducted the call back procedure.^[11] During the call back procedure, cabin crew advised the CSM of further injured passengers and cabin crewmembers.

As the aircraft tracked on the outbound leg of the holding pattern, the lavatory smoke alarm activated and the flight crew received a lavatory smoke alarm warning. The captain asked the first officer to request a priority landing from ATC. ATC immediately cleared the flight directly to Hong Kong International Airport.

The cabin crewmembers established that the smoke alarm originated at the R5 lavatories and that there was no evidence of smoke, fire or fumes. The CSM reported to the flight deck that they believed the smoke alarm to be a false alarm caused by the lavatory damage.

While approaching Hong Kong International Airport, the smoke alarm activated a further six times. The cabin crewmembers determined that these alarms were also false. The aircraft landed without further incident.

Four cabin crewmembers and two passengers received minor injuries during the incident and the aircraft cabin sustained minor damage.

1. Pilot Flying (PF) and Pilot Monitoring (PM): procedurally assigned roles with specifically assigned duties at specific stages of a flight. The PF does most of the flying, except in defined circumstances; such as planning for descent, approach and landing. The PM carries out support duties and monitors the PF’s actions and the aircraft’s flight path.
2. Hong Kong Time was Co-ordinated universal time +8 hours.
3. Waypoint: A defined position of latitude and longitude coordinates, primarily used for navigation.
4. Lateral navigation and vertical navigation modes: In the lateral navigation mode, the roll command is calculated by the flight management computer based on the active flight plan. The vertical navigation mode supplies pitch control in response to vertical navigation data from the active flight plan.
5. Flight level: at altitudes above 10,000 ft, an aircraft’s height above mean sea level is often referred to as a flight level (FL). FL 300 equates to 30,000 ft.
6. The flaps-up manoeuvre speed could be calculated using the addition of a speed increment of 80 kt to the flaps-30 landing reference speed.
7. Pitch angle: the angle of the aircraft body as it moves about its lateral (wingtip-to-wingtip) axis in relation to the horizon.
8. Pre-aerodynamic stall buffeting occurs when the wing approaches the stall angle of attack. Airflow from the wing’s upper surface begins to separate and become turbulent. The turbulent flow passes across the horizontal stabiliser and is felt through the aircraft as buffeting.
9. The underwing location of the engines, low on the airframe, imparted a large pitch up moment upon a large increase in engine power.
10. N1: the rotational speed of the low pressure compressor in a turbine engine.
11. Call back: A procedure conducted after an incident, where each cabin crewmember contacts the CSM using the cabin interphone to advise of their welfare.

Context

Flight crew

Captain

The captain held an Air Transport Pilot Licence (Aeroplane), a multi-engine command instrument rating and a Class 1 Aviation Medical Certificate. The captain had over 24,000 hours of flying experience, of which over 10,000 hours were on the Boeing 747.

First officer

The first officer held an Air Transport Pilot Licence (Aeroplane), a multi-engine command instrument rating and a Class 1 Aviation Medical Certificate. The first officer had over 16,000 hours of flying experience, of which over 5,000 hours were on the Boeing 747.

The investigation assessed whether the captain or first officer were experiencing a level of fatigue known to have an effect on performance. The ATSB found no indicators that increased the risk of either crew experiencing this level of fatigue.

Second officer

The second officer held an Air Transport Pilot Licence (Aeroplane), a multi-engine command instrument rating and a Class 1 Aviation Medical Certificate. The second officer had over 8,000 hours of flying experience, of which over 5,000 hours were on the Boeing 747.

Meteorological information

As the aircraft entered the holding pattern, the aircraft recorded wind direction was 268°M and speed was 41 kt. The flight crew reported visual meteorological conditions with slight haze prevailed at the time of the occurrence.

The flight crew also reported experiencing smooth conditions prior to, and throughout, the event. There was little to no recorded turbulence. The ATSB therefore concluded that turbulence did not contribute to the pre-aerodynamic stall buffeting or stick shaker activations.

Aircraft information

Autopilot holding with LNAV/VNAV active

When holding with LNAV active, the FMC tracks the holding pattern targeting a 25-degree bank angle up to a limit of 30 degrees of bank angle. The FMC computes holding patterns with constant radius turns based on the current wind and commanded speed.

The aircraft tracked 317°M as it crossed BETTY (Figure 4) and began a right turn, through a total of 207°, to track 164°M for the outbound leg of the pattern.

As the aircraft turned, the wind direction moved to a relative position behind the aircraft, increasing the aircraft’s ground speed. The increased ground speed required a greater bank angle to achieve the targeted turn radius and outbound track spacing. The first officer also later commented that when the holding entry required a turn in excess of 180°, the autopilot would initially command a bank greater than 30 degrees.

The aircraft manufacturer commented that the autopilot has the capability to increase bank angle beyond the FMC commanded angle. The manufacturer further commented that it was not unusual that the increasing ground speed led the autopilot to increase bank angle with an overshoot up to 32 degrees to achieve the FMC target turn radius and outbound track spacing.

Figure 4: BETTY holding pattern

The figure shows the BETTY holding pattern along with the recorded wind conditions, the approximate track of VH-OJU as it entered the holding pattern and the locations of the buffet/stick shaker occurrence and first smoke alarm. Source: Hong Kong Civil Aviation Department, annotated by ATSB

Operational information

Hold speed

The FMC calculated target hold speed and target level are based on the aircraft’s gross weight and programmed VNAV descent profile (see Figure 2). Below FL 150, this speed is based upon the flaps 30 landing reference speed with the addition of a speed increment. The speed increment varies with aircraft weight and is designed to provide a manoeuvre margin^[12] equivalent to a level turn at 40 degrees angle of bank or 1.3 G of vertical acceleration.

Above FL 200, the FMC calculated hold speed corresponds to the minimum drag speed.^[13]

Between FL 150 and FL 200 the FMC target hold speed is calculated using a linear interpolation between the speeds calculated for FL 150 and FL 200.

The FMC also calculates best speed, which is displayed on the hold page (see Figure 2). The operator’s flight crew operations manual (FCOM) contained the following guidance on the best speed function on the hold page of the FMC:

Displays best holding speed for airplane gross weight, altitude, and flap setting.

The displayed best speed may be different to the target hold speed in the hold planning stage as the hold may be planned using an altitude different to the current altitude. If no target speed is selected, the FMC will select the best speed.

The aircraft manufacturer provided the following advice regarding the hold speed for this event:

At 22,000 feet, the optimum holding pattern airspeed would have been approximately 240 knots based upon the event gross weight.

For holding when hold speeds are not available from the FMC, the operator’s flight crew training manual (FCTM) provided the following guidance:

Recommended holding speeds can be approximated by using the following guidance until more accurate speeds are obtained from the quick reference handbook:

- Flaps up manoeuvre speed approximates the minimum fuel burn speed and may be used at low altitudes^[14] (approximated by adding 80 kt to the calculated flaps 30 landing reference speed)

- If the FMC calculated hold speed is not available, when holding above FL 200 recommended holding speeds can be approximated by adding 100 kt to the calculated flaps 30 landing reference speed.

Following the above guidance would have provided an approximate hold speed of 243 kt.

The programmed VNAV descent profile crossed BETTY at FL 156. The FMC calculated a target hold speed of 223 kt at FL 156 for holding at BETTY. When ATC instructed the flight crew to hold at FL 220, the captain instructed the first officer to input a target speed of 225 kt at or above FL 150 into the FMC.

While hold speed data was available from the FMC, the flight crew were not aware that a different speed was required above FL 200 and used speed data for FL 156 for holding at FL 220.

Flight crew high altitude hold speed knowledge and training

The flight crew reported that in practice they used the flaps up manoeuvring speed and then added an arbitrary buffer when selecting a hold speed. This is contrary to the FCTM guidance, and there was no other operator or manufacturer guidance recommending this procedure or the size of the buffer to be used. The investigation found that the flight crew were not aware of the function, or use of, the best speed in the hold page of the FMC.

The operator provided training for flight crew on holding patterns and speeds during ground school training prior to the commencement of operations on the aircraft type and during recurrent operational training.

The operator reported that there were no documented training exercises where a holding pattern was conducted at high altitude (above FL 200). Holding patterns were generally conducted at lower levels prior to commencing a landing approach.

Minimum manoeuvre speed

The aircraft’s FMC calculated minimum manoeuvre speed provides 0.3 G of margin above the onset of pre-aerodynamic stall buffet. This is equivalent to a level turn at 40 degrees angle of bank or 1.3 G of vertical acceleration.

The minimum manoeuvre speed is indicated by the top of an amber band on the speed tape of the PFD (Figure 6: Figure 5). When operating at a speed within the amber band, reduced manoeuver capability exists.

Figure 5: Representation of the primary flight display as the aircraft crossed BETTY

This figure shows a representative presentation of the primary flight display as the aircraft crossed BETTY, derived from recorded flight data. The minimum manoeuver speed amber band and selected speed bug are annotated. Source: ATSB

Stall warning activation speed

The speed at which the aircraft’s stall warning system would activate was indicated on the PFD as a red dashed line (see Figure 5 above).

This indication was dynamic and moved in accordance with various factors such as aircraft configuration, gross weight and aircraft manoeuvring. This provided the flight crew with a real-time indication of the stall warning activation speed.

Recorded flight data

• Flight data was available from the flight data recorder and the quick access recorder.

Figure 6: Graphical representation of quick access recorder data

The figure shows a graphical representation of recorded flight data from stick shaker incident significant points of the occurrence are annotated. Source:  ATSB

The aircraft manufacturer reviewed the flight data and determined that during the stick shaker occurrence, the aircraft did not enter a stall. The manufacturer provided the following analysis:

For the 747-400, at the event flight condition, the estimated maximum vane angle of attack before stall is achieved would be approximately five degrees.^[15] During this occurrence, the highest recorded vane angle of attack was approximately -0.5 degrees, resulting in significant margin to the estimated maximum vane angle of attack when stick shaker activated.

The recorded data did not show a stick shaker activation at the time the autopilot disconnected,^[16] as described by the flight crew. At this time, the recorded vane angle of attack reached a value about 0.3 degrees below the estimated angle for stick shaker activation. However, as the stick shaker activation parameters are recorded at a rate of one sample per second, it is possible that the stick shaker activated momentarily and was not captured by the flight recorders.

The recorded vertical acceleration at the time of the initial buffet and possible stick shaker activation was 1.29 G. The maximum vertical acceleration value recorded during the occurrence was 1.45 G, the minimum recorded value was 0.09 G.

Stall recovery procedures and training

Stall warning recovery procedure

The aircraft was fitted with a stick shaker device to provide warning to the flight crew that the aircraft was approaching an aerodynamic stall. When activated, the stick shaker vibrated both control columns, providing an aural and tactile warning indication.

The operator procedures included the ‘approach to stall or stall warning’ procedure. In case of a stall warning, the procedural steps to be followed are shown in Figure 7:

Figure 7: Approach to stall or stall recovery procedure

Source: Operator

The recorded data showed that during the recovery after the initial buffet and possible stick shaker activation, the captain did not disconnect the autothrottle. While he reduced the bank angle, he did not level the wings or advance the thrust levers as needed to effect recovery. Nor were these actions completed during the second and third recovery attempts.

The autothrottle was not disconnected and the thrust levers were not advanced as needed to effect recovery until the fourth oscillation. After this increase in thrust, speed increased sufficiently for the captain to arrest the descent and stabilise the aircraft without further stick shaker activations.

During the oscillations, the first officer did not identify or call out the incomplete actions, as required by the procedure.

Approach to stall and stall recovery training

The operator provided approach to stall and stall recovery training to flight crew during type conversion training and their recurrent operational training in accordance with manufacturer recommendations and as approved by the Civil Aviation Safety Authority. Each flight crew member had undergone this training on multiple occasions, exposing them to various stall recovery scenarios.

The stall recovery scenario conducted in the most recent exercise was simulated with the aircraft:

• configured with landing gear down and flaps 20
• positioned on the downwind leg of a circuit (about 1,500 ft above ground level)
• weight of 266,000 kg.

During the exercise, a first officer, as pilot flying, closes the thrust levers while in level flight just before turning onto the base leg of the circuit. The crew should recover at first stall indication, using the correct recovery procedure. The exercise was then repeated with the captain as pilot flying.

The captain last underwent this training on 4 April 2017, three days prior to the incident flight. The first officer had last undergone stall recovery training in October 2014 and the second officer in February 2017.

The scenarios all commenced with the crew reducing the engine power to idle prior to the stick shaker activating, and all recoveries were initiated with engine power at idle.

In their internal investigation report, the operator provided the following analysis of the stall recovery training:

The investigation could not find any trained scenarios that approximated the conditions experienced by QF29; that is; stick shaker activation while manoeuvring at altitude. By limiting stick shaker recovery to non-realistic scenarios, with considerable lead in time giving Flight Crew ample opportunity to prepare for the forthcoming manoeuvring, there is limited exposure to the complexity of the required recovery actions at altitude in real life scenarios…

…Further enhancing stick shaker recovery by including realistic scenarios, during training may provide increased exposure for Flight Crew of the relationship between control column movement and true airspeed, preventing further Flight Crew over-controlling events brought about by startle effect.

Smoke alarm activations

The ATSB could not determine the reason why the smoke alarms in the R5 lavatory activated after the upset. However, the lavatories at R5 and L5 shared a ventilation system and it may have been that dust, from the lavatory fittings detaching in the L5 lavatory, activated the R5 smoke alarm.

During the smoke alarm activations, cabin crewmembers responded appropriately and acted in accordance with procedures. Additional crewmembers in the rear aircraft cabin also supported the response to the smoke alarm.

ATSB research report

In 2013, the ATSB released the research report AR-2012-172 Stall warnings in high capacity aircraft: The Australian context.

This research report reviewed 245 stall warnings and stall warning system events reported to the ATSB over a 5-year period (2008–2012). The ATSB identified 33 serious and higher risk incidents in which a stall warning occurred, and in several cases the stall warning speed was higher than normal (due to a higher vertical acceleration (G) factor in a turn, or an incorrect reference speed switch setting). The report contained the following safety message:

Stall warnings occur in normal operations, and are normally low risk events. In Australia, even the most serious events have not resulted in a loss of control, and have been effectively managed by flight crew to prevent a stall from occurring. To avoid higher risk stall warning events, pilots are reminded that they need to be vigilant with their awareness of angle of attack and airspeed.

12. Manoeuvre margin is the available manoeuvre capability of the aircraft prior to activation of the stall warning system.
13. Minimum drag speed is the speed at which total aircraft drag, and therefore fuel consumption, is lowest.
14. The FCTM guidance advised that the flaps up manoeuvring speed guaranteed at least full manoeuvre capability, or at least 40° of bank to stall warning activation ‘within few thousand feet of the airport altitude’ and noted that ‘less manoeuvre margin to stick shaker exists for a fixed speed as altitude increases’.
15. Five degrees vane angle corresponds to 13 degrees body angle of attack.
16. The cockpit voice recorder was not available for analysis. Therefore, the investigation could not determine if the stick shaker activated during the initial buffet onset.

Safety analysis

Identification of necessity to recalculate hold speed

Prior to arriving at BETTY, the VNAV profile in the flight management computer (FMC) calculated holding at between FL 150 and FL 160. When selecting a target speed, the flight crew verified the FMC provided speed by comparing the speed to the flaps up manoeuvre speed calculation. However, the flight crew training manual advised that the flaps up manoeuvring speed guaranteed at least full manoeuvre capability, to stall warning activation at low altitudes. The flight crew were not aware of the requirement to use a different speed calculation verification for altitudes above FL 200.

Had the crew recalculated the hold speed for FL 220 using the flight management computer, it would have provided a target hold speed of 240 kt. In this case, the flight crew likely did not have an adequate understanding of how the FMC calculated the target hold speed. They also did not understand the use of the best speed provided on the hold page in the FMC. Using best speed would have provided the crew with a hold speed for the actual aircraft weight, altitude and configuration at that time. Orasanu (2010) outlines that decision errors in aviation are often a result of a lack of knowledge:

[They] typically are not slips or lapses in carrying out an intention, but errors of intention itself (Norman, 1981). The decision maker acts according to his/her understanding of the situation, and the source of error is in the decision maker’s knowledge base or in the process of reaching a decision.

The selection of an incorrect hold speed resulted in the aircraft entering the hold with a selected speed 15 kt below the required speed. Using the best speed in the FMC hold page or recalculating the hold speed using the FMC for the higher level would have resulted in the use of a speed which provided sufficient margin to prevent a stick shaker activation.

Absence of hold speed re-evaluation procedure

Neither the operator or aircraft manufacturer provided procedures or guidance which stated that a hold speed was required to be re-evaluated for a change in hold level when a speed was selected in the FMC during the planning stage of a descent. Therefore, the flight crew did not have the requisite knowledge to identify the need to re-evaluate the selected speed.

Reason (2008) explains that decision errors, such as not re-evaluating the hold speed, can be as a result of a ‘failure to detect a signal or problem’, and are more likely under conditions including ‘when the person did not expect to find a problem in that location…’. Detecting a problem, or an absence of an action can be particularly difficult when there are no cues to identify an issue. In this case, there was no procedural prompt for the flight crew to re-evaluate the speed for the higher level and select the correct speed. Therefore, the need to re-evaluate the hold speed relied on the crew’s knowledge of the higher speed requirement above FL 200.

This resulted in the remaining protections against a low-speed condition being the minimum manoeuvring and stall warning activation speed indications on the pilot’s flight display. At the time the speed reduced below both the selected speed and the minimum manoeuvring speed, the flight crew’s attention was focussed on other operational matters resulting in the crew not identifying the reduced speed.

In summary, a requirement to re-evaluate the speed for the higher than planned hold level would likely have provided the crew with a prompt to reselect the speed, which in turn would provide an adequate margin above the minimum manoeuvring speed.

Crew recognition of low speed prior to entering the hold

As the aircraft entered the holding pattern, the delay in the autothrottle system detecting and effecting changes in aircraft speed allowed the speed to reduce to 220 kt—below both the selected speed of 225 kt and the minimum manoeuvring speed of 223 kt.

These speeds, along with the stall warning activation speed were displayed on the PFD, but the flight crew did not detect that the speed had reduced as their attention was on other operational tasks. Reason (2008) outlines why focusing one’s attention on one task can be to the detriment of noticing other important tasks:

…attention is a limited resource. Direct it at one thing and it is withdrawn from another. When attention is ‘captured’ by something unrelated to the task at hand, actions often proceed unintentionally along some well-trodden pathway: strong habit intrusions.

Not noticing a visual indication well within one’s visual scan can be a common outcome to a crew’s attention being focused elsewhere, as explained by Wickens and McCarley (2008):

Change blindness…occurs when an observer fails to detect an event (e.g. discreet change) in the environment around him…[and is a] failure to notice that something is different from what it was…How do lapses occur? Very often, [change blindness] is a failure of attention. Data indicate that changes are likely to go unnoticed if they are not attended when they occur…[i.e.] if the observer is looking away…

It can be difficult to detect discreet changes, even with visual indicators of limits (i.e. speed bug on the PFD) in view of the crew, when attention is on other operational matters. In turn, this reduced the likelihood that they could detect an undesirable aircraft condition.

Pre-aerodynamic stall buffet and probable stick shaker activation

As the aircraft turned to enter the holding pattern, the bank angle increased and the aircraft began to transition from descent to level flight. The effects of these manoeuvres combined to increase the vertical acceleration and wing angle of attack. The increasing angle of attack initiated pre-aerodynamic stall buffeting.

At this time, although it was not recorded on the flight data, all flight crewmembers reported a stick shaker activation. The recorded angle of attack also indicated that a stick shaker likely occurred. The manufacturer advised that an activation of less than one second in duration may occur without being captured in the flight recorder data.

Pilot induced oscillations and cabin injuries

At the time of the initial buffeting and probable stick shaker activation, the captain commenced the approach to stall and stall recovery actions required within the operating procedures. However, after this, a number of the other actions required by procedures were not completed, including the following:

• due to a desire to remain within the protected airspace of the holding pattern, the wings were not levelled
• the autothrottle was not disconnected
• due to the captain’s concern regarding the pitch up moment resulting from a large engine power increase, engine power was not manually increased sufficiently to effect recovery
• the first officer assessed that the actions had been completed correctly and did not identify or therefore call out the missed actions.

After the captain did not complete the approach to stall recovery procedure, the aircraft entered a series of pilot induced oscillations during which the crew’s premature attempts to arrest the rate of descent without increasing power as needed and before the speed had increased sufficiently, resulted in a further two stick shaker activations. After a fourth oscillation (during which the flight crew did not recall a stick shaker activation and an activation was not recorded), the engine power was increased sufficiently to accelerate the aircraft to enable the flight crew to complete the recovery.

The ATSB considered whether the captain’s performance was affected by a startle response, which is defined by Landman and others (2017) as a ‘physiological reaction to a highly salient stimulus’ (e.g., sudden, intense, or threatening; Rivera, Talone, Boesser, Jentsch, & Yeh, 2014). Rivera and others (2014) add that it disrupts ‘cognitive processing and can negatively influence an individual’s decision making and problem-solving abilities’. They outline that the reaction can result in the following:

Studies have determined that motor response performance following a startling stimulus is disrupted for approximately 0.1 s to 3 s for simple tasks (May & Rice, 1971; Sternbach, 1960; Thackray, 1965)…In more complex motor tasks…startle may impact performance for up to 10 s following a loud intensity signal (Thackray & Touchstone, 1970).’

Rivera and others (2014) also stated that ‘one must also consider the time to cognitively recover after a startling stimulus’. Within this same reference citing Bürki-Cohen (2010), they outline the difference between startle and surprise.

…there are distinctive conceptual, behavioural, and physiological differences between the startle reflex and the surprise emotion.

In contrast to startle, which always occurs as a response to the presence of a sudden, high-intensity stimulus, surprise can be elicited by an unexpected stimulus or by the unexpected absence of a stimulus. Surprise can be described as a combination of physiological, cognitive, and behavioural responses, including increased heart rate, increased blood pressure, an inability to comprehend/analyze, not remembering appropriate operating standards, “freezing”…

In this case, it was not determined as to whether the tactile stimulus of the stick shaker and the aural alert was sufficient to elicit a startle response. However, the reaction of the captain in undertaking the initial approach to stall recovery did not largely appear to be adversely affected, as most actions were completed and the omitted or incomplete actions resulted from deliberate decisions. When then considering the continuation of the recovery steps, he was also able to outline the reasons for his actions, which do not necessarily demonstrate a negative influence on his decision making or problem-solving abilities.

With respect to the first officer, he perceived that the absence of his call-outs required of the pilot monitoring position (including not calling out any omissions during the recovery continuation and completion) were a result of experiencing the startle effect. Given that the approach-to-stall recovery actions overall were completed in about 10 seconds, this is possible. However, there was insufficient evidence to determine whether his was a response to a sudden, high-intensity stimulus. His reaction may appear more consistent with surprise, whereby there was a cognitive mismatch between new information and expectations, especially as he had no expectation of stick shaker activation.

The recorded flight data shows that during the oscillations, the aircraft underwent significant variations in vertical acceleration. The pilot-induced oscillation occurred at a time when the fasten seat belt sign was not illuminated and cabin crewmembers were standing in the rear cabin, completing the cabin preparation for landing. The variations in vertical acceleration resulted in several cabin crewmembers and passengers impacting the cabin ceiling and furnishings, sustaining minor injuries. The impact of occupants to the cabin ceiling and furnishings resulted in damage to these furnishings, in particular an L5 lavatory. This damage resulted in the L5 and R5 lavatory smoke alarm activations.

Limited guidance in high altitude manual handling and stall recovery training

All flight crew undertook simulator training exercises as part of a cyclic training schedule. The most recent exercise undertaken by the crew included an approach to stall recovery scenario exercise, which was simulated at low altitude and with the aircraft configured with flaps and landing gear extended. In this instance, the simulated aircraft response would be markedly different to that of an aircraft operating at higher altitudes (such as FL 200 and above) and with the landing gear and flaps retracted.

In this case, the flight crew had undergone this cyclic training exercise, including the captain who completed the training three days prior to the occurrence. In addition, after the event, they could recall the correct recovery actions indicating that the training was effective in providing the crew with the required knowledge to effect the recovery.

However, this training exercise did not familiarise the crew with the manual handling of the aircraft at higher altitudes. Hasleback (2014) states:

From [a pilot’s initial training onwards], pilots are faced with automation induced skill degradation (Balfe, Wilson, Sharples, & Clarke, 2012), caused by the automation taking over the responsibility for tasks previously performed by the human operators (Parasuraman & Riley, 1997).

There are ways to overcome this. In a study examining the relationship between pilot manual handling performance and recency, Ebbatson (2009) outlined that ‘significant relationships are identified between pilots’ recent flying experience and their manual control strategy’. Hasleback and others (2014) summarised this study to show that ‘recent flight practice including manual flying occurring a few weeks prior to the experiment had more influence on the measured performance than flight hours accumulated over a pilot’s entire career’.

Orlady and Orlady (1999) explain the importance of including manual handling exercises in training:

Using today’s automation more efficiently does not mean that today’s pilots do not need all of the old skills and knowledge… They need all of the old skills plus the new skills required by the automation…Manual skills must be a part of any recurrent or transition training and checking program in addition to the emphasis given to the proper use of the automatics.

In this case, the opportunity for flight crew to practice their high-altitude manual handling skills was limited, which in turn limited the ability of flight crews to retain the necessary manual handling skills for stall recovery at higher altitudes. As a result, the flight crew did not adequately respond to the initial buffet and probable stick shaker activation, leading to the in-flight upset.

Use of seatbelts

Prior to the occurrence, the cabin crewmembers prepared the cabin for arrival at Hong Kong. This included an announcement to fasten seatbelts, however, at this time, the fasten seatbelt sign was not illuminated.

At the time of the in-flight upset, a passenger was located in the L5 lavatory and cabin crewmembers were in the rear cabin preparing for arrival. During the upset, the aircraft cabin was subject to large variations in vertical acceleration. Due to the unexpected nature of the event, neither the cabin crewmembers or the passenger in the L5 lavatory, who did not have a seatbelt available, were seated and secured at the time of the event. As a result, four cabin crewmembers and the passenger in the L5 lavatory sustained minor injuries.

A passenger seated in seat 63C did not have their seatbelt fastened. During the upset, this passenger impacted cabin furnishings and sustained minor injuries. Other seated passengers did have seatbelts fastened and as a result were not injured.

In-flight upsets, while rare, can have the potential to cause injuries. Evidence from this incident along with other incidents demonstrates that while seated, keeping a seatbelt fastened and secure significantly reduces the likelihood of being injured during an upset.

Findings

From the evidence available, the following findings are made with respect to the stick shaker activation event involving Boeing 747, VH-OJU, that occurred 110 km SE of Hong Kong International Airport (BETTY IFR), on 7 April 2017. These findings should not be read as apportioning blame or liability to any particular organisation or individual.

Safety issues, or system problems, are highlighted in bold to emphasise their importance. A safety issue is an event or condition that increases safety risk and (a) can reasonably be regarded as having the potential to adversely affect the safety of future operations, and (b) is a characteristic of an organisation or a system, rather than a characteristic of a specific individual, or characteristic of an operating environment at a specific point in time.

Contributing factors

• After overwriting the hold speed in the flight monitoring computer, the flight crew did not identify the need to re-evaluate the hold speed for the higher than expected hold level.
• Prior to entering the hold, the aircraft’s speed reduced below both the selected and minimum manoeuvring speeds. The crew did not identify that the aircraft was operating below these speeds.
• The reduced speed coincided with the turn to enter the holding pattern and the level capture. These factors resulted in pre-aerodynamic stall buffeting and probable stick shaker activation.
• The pilot flying attempted to arrest the rate of descent prior to completing the approach to stall actions. The pilot monitoring did not identify and call out the incomplete approach to stall recovery actions. These combined actions led to pilot induced oscillations and further stick shaker activations.
• The operator provided flight crew with limited training and guidance in stall prevention and recovery techniques at high altitudes or with engine power above idle. (Safety issue)
• The passenger in seat 63C was not wearing a seatbelt at the time of the stick shaker activations.

Other safety factor

• The operator provided flight crew with limited training and guidance relating to the need for crew to re-evaluate their holding speed for a change in altitude (specifically above flight level 200). (Safety issue)

Safety issues and actions

The safety issue identified during this investigation is listed in the Findings and Safety issues and actions sections of this report. The ATSB expects that all safety issues identified by the investigation should be addressed by the relevant organisation(s). In addressing those issues, the ATSB prefers to encourage relevant organisation(s) to proactively initiate safety action, rather than to issue formal safety recommendations or safety advisory notices.

All of the directly involved parties were provided with a draft report and invited to provide submissions. As part of that process, each organisation was asked to communicate what safety actions, if any, they had carried out or were planning to carry out in relation to each safety issue relevant to their organisation.

Descriptions of each safety issue, and any associated safety recommendations, are detailed below. Click the link to read the full safety issue description, including the issue status and any safety action/s taken. Safety issues and actions are updated on this website when safety issue owners provide further information concerning the implementation of safety action.

Stall prevention and recovery at high altitudes

Safety issue number: AO-2017-044-SI-01

Safety issue description:
The operator provided flight crew with limited training and guidance in stall prevention and recovery techniques at high altitudes or with engine power above idle.

Re-evaluating hold speeds for a change in altitude

Safety issue number: AO-2017-044-SI-02

Safety issue description:
The operator provided flight crew with limited training and guidance relating to the need for crew to re-evaluate their holding speed for a change in altitude (specifically above flight level 200).

Proactive safety action

The operator reviewed the training and guidance provided to other Boeing aircraft types in its fleet, the 787 and 737, and made the following changes:

Training and guidance

The operator amended recurrent lesson plans for the 787 and 737 fleets to incorporate more complex stall warning recovery events. The operator also updated lesson plans and distributed educational material to all flight crews.

The operator amended the 787 and 737 flight crew training manuals relating to hold speed selection to provide enhanced holding pattern information to flight crew. They also updated ground school lesson plans and information to ensure standardised flight crew training and ensure holding pattern training was adequately addressed during flight crew training.

General details

Pilot details – Captain

Pilot details – First officer

Pilot details – Second officer

Aircraft details

Sources and submissions

Sources of information

The sources of information during the investigation included the:

• Operator
• Boeing (manufacturer)
• Aircraft crew
• Hong Kong Civil Aviation Department

References

Australian Transport Safety Bureau (ATSB). (2013). Stall warnings in high-capacity aircraft: The Australian context 2008 to 2012. Canberra ATSB.

Ebbatson, M., Harris, D., Huddlestone, J. and Sears, R., 2010, The relationship between manual handling performance and recent flying experience in air transport pilots, Ergonomics, pp.268-277

Hasleback, A., Kirchner, P., Schubert, E. and Bengler, K., 2014, A flight simulator study to evaluate manual flying skills of airline pilots, Proceedings of the Human Factors and Ergonomics Society 58th Annual Meeting, pp.11-15

Landman, A., Groen, E., van Paassen, MM., Bronkhorst, AW. and Mulder, M., 2017, The Influence of Surprise on Upset Recovery Performance in Airline Pilots, The International Journal of Aerospace Psychology, 27:1-2, 2-14

Orlady, HW., and Orlady, LM., 1999, Human Factors in Multi-Crew Flight Operations, Ashgate Publishing Limited, Aldershot, England

Reason, J., 2008, The Human Contribution: Unsafe acts, accidents and heroic recoveries, Ashgate Publishing Limited, Surrey, England

Rivera, J., Talone, AB., Boesser, CT., Jentsch, F. and Yeh, M, 2014, Startle and Surprise on the Flight Deck: Similarities, Differences, and Prevalence, Proceedings of the Human Factors and Ergonomics Society 58th Annual Meeting, pp.1047-1051

Wickens, CD. and McCarley, JS., 2008, Applied Attention Theory, CRC Press, Florida, USA

Submissions

Under Part 4, Division 2 (Investigation Reports), Section 26 of the Transport Safety Investigation Act 2003 (the Act), the Australian Transport Safety Bureau (ATSB) may provide a draft report, on a confidential basis, to any person whom the ATSB considers appropriate. Section 26 (1) (a) of the Act allows a person receiving a draft report to make submissions to the ATSB about the draft report.

A draft of this report was provided to the flight crew, customer service manager, Qantas, the Civil Aviation Safety Authority, and Boeing.

Any submissions from those parties were reviewed and where considered appropriate, the text of the draft report was amended accordingly.

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through:  identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2019 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

What happened

On 18 April 2017, at about 0934 Western Standard Time (WST), a Bombardier DHC-8-315 aircraft, registered VH-XKI, departed from Meekatharra Airport, Western Australia (WA), for a charter flight to Leinster, WA. There were two flight crew, two cabin crew and 49 passengers on board.

The aircraft had departed from Perth Airport, WA, at about 0540 that morning, on a charter flight to Leinster, with Meekatharra as the alternate airport. While the aircraft was en route to Leinster, the flight crew received an updated weather report, which indicated there was fog present at Leinster. The flight crew conducted one approach at Leinster and as they did not get visual with the runway, they diverted to Meekatharra. While on the ground at Meekatharra, the captain received a report from their^[1] operations department in Perth that the weather at Leinster had improved. The captain elected to depart Meekatharra with sufficient fuel for the flight to Leinster while maintaining Meekatharra as the alternate airport.

The captain reported that the aircraft performed as normal during the take-off run. After take-off, the landing gear was retracted, followed by the flap.^[2] At some point between retracting the flap and 1,000 ft above ground level, the flight crew experienced a vibration through the airframe and noticed a change in the pitch of the aircraft noise (deep pitch sound). The flight crew noticed the right propeller was at about 500 RPM (normal governed flight range is 900–1200 RPM) and the engine torque was excessively high.^[3] The low propeller RPM and high engine torque led them to conclude the malfunction was an ‘unscheduled feather’^[4] incident.^[5]

While the aircraft climbed to the lowest safe altitude, the flight crew shutdown the right engine, in accordance with their emergency operating procedures. Once at their lowest safe altitude, the flight crew engaged the autopilot, completed the checklist actions and made a PAN^[6] radio broadcast to air traffic control. Noting that the aircraft was above the maximum landing weight, the flight crew reviewed the performance charts, and concluded that the runway at Meekatharra was suitable for an emergency landing and elected to return. The flight crew briefed the cabin crew that they were going to land overweight with one engine shutdown and therefore to prepare the cabin for an emergency landing. The aircraft landed without incident. No persons were injured, and the aircraft was not damaged.

Unscheduled autofeather

The autofeather system meets the regulatory requirements for an automatic take-off thrust control system, and in the event of an engine failure, the system:

• trims the opposite engine power by a pre-determined amount to permit continued safe take-off without pilot intervention
• feathers the propeller of the failing engine to minimise the drag after a three second time delay.

In the event of an engine failure on take-off (less than 29 per cent torque sensed), the failed engine torque signal conditioning unit (TSCU) initiates autofeathering by switching its logic from ‘arm’ to ‘arm and fail.’ A relay signals the engine control unit (ECU) of the other engine to increase power (uptrim) to compensate for the failed engine (Figure 1). After 3 seconds, the TSCU logic transitions from ‘arm and fail’ to ‘fail and feather’. This isolates the second engine’s TSCU to disable its autofeather system to ensure both propellers cannot be feathered at the same time, and energises the failed engine feathering solenoid to feather the propeller of the failed engine.

Figure 1: Autofeather overview for no.2 (right) engine failure

Source: ATSB (information from aircraft manufacturer)

Aircraft inspections

The operator’s maintenance organisation downloaded the flight data recorder for analysis by the engine manufacturer. It was determined that an uptrim signal was sent to the left engine by the right engine TSCU and the right engine experienced an over-torque event of 146% for 25 seconds.^[7] Both engine control units provided several fault codes, which were investigated with no defects found. The right engine TSCU and propeller hub and blades were replaced in accordance with the directions from the respective manufacturers. The right engine reduction gearbox^[8] and oil system were inspected with no defects found. In addition, the right engine electronic controller was replaced for troubleshooting purposes.

In 2002 the aircraft manufacturer published an in-service engineering and technical support letter titled ‘Autofeather arming and uncommanded autofeather events’. The purpose of the letter was to identify uncommanded autofeather events and suggest solutions. The maintenance organisation referred to this letter for troubleshooting and completed the procedures for ‘autofeather during power applications’ and ‘autofeather during take-off or climb with the system armed (uncommanded).’ No defects were found. It was determined from the flight data analysis that a heavy landing inspection was not required. After several engine ground runs were conducted at take-off power with the autofeather system armed, without any faults, the aircraft was flown to Perth. The flight to Perth was reported as uneventful and the aircraft was returned to service.

Safety action

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

Operator

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

Maintenance inspections

The operator’s continuing airworthiness management organisation has scheduled recurrent inspections of the reduction gearbox oil system and are following up with the engine manufacturer for their findings concerning the removed engine electronic controller and torque signal conditioning unit.

Safety message

The aircraft captain reported that they felt the incident was handled well by the flight crew and cabin crew. They found that the use of automation was effective in reducing their workload while responding to the malfunction. Despite the fact that both cabin crew were relatively new to the company, the captain could clearly hear them making their emergency landing calls to the passengers in accordance with their emergency operating procedures. The captain reported that the incident was completely unexpected, which highlighted to them the need for, and benefit of, regular simulator training.

Aviation Short Investigations Bulletin Issue 61

About this report Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, a limited-scope, fact-gathering investigation was conducted in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2017 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

__________

1. Gender-free plural pronouns: may be used throughout the report to refer to an individual (i.e. they, them and their).
2. Movable surface forming part of the trailing edge of the wing, which alters wing camber, cross section and area in order to exert a powerful effect on low-speed lift and drag.
3. Engine torque limits were 90% maximum continuous, 100% maximum 5 minutes, 115% maximum 20 seconds.
4. Feathering: the rotation of propeller blades to an edge-on angle to the airflow to minimise aircraft drag following an in-flight engine failure or shutdown.
5. The aircraft was fitted with an auto-feather system, which will automatically feather the propeller of a failed engine within specified operating parameters.
6. PAN PAN: an internationally recognised radio call announcing an urgency condition which concerns the safety of an aircraft or its occupants but where the flight crew does not require immediate assistance.
7. The over-torque was likely the result of the engine attempting to maintain normal propeller operating speed at the time that the propeller was attempting to feather.
8. The reduction gearbox is installed between the engine and the propeller and reduces the high rotational speed of the turbine engine to the slower rotational speed of the propeller.

On 09 April 2017, an ATR 72 aircraft, registered ZK-MCY, experienced unsafe landing gear indications on approach to Nelson, New Zealand (NZ). The aircraft diverted to Palmerston North, NZ, where it made an emergency landing. During the landing roll the right main gear tyre burst and the aircraft was brought to a stop on the runway. An investigation into the circumstances of the accident is being conducted by the Transport Accident Investigation Commission (TAIC) of New Zealand.

The TAIC requested assistance from the Australian Transport Safety Bureau (ATSB) to download the aircraft’s cockpit voice recorder (CVR).

To facilitate this support and to provide the appropriate protections for the CVR information, the ATSB appointed an accredited representative in accordance with paragraph 5.23 of ICAO Annex 13 and commenced an investigation under the Australian Transport Safety Investigation Act 2003.

The New Zealand TAIC is responsible for releasing the final investigation report regarding this accident.

The TAIC can be contacted via: www.taic.org.nz

What happened

On 6 April 2017, the operators of a Yamaha RMAX^[1] remotely piloted aircraft system (RPAS) (Figure 1) were conducting aerial spraying about 23 km west of Canberra, Australian Capital Territory. One operator was acting as the remote pilot in command of the RMAX and the other was mixing chemical, ferrying it to the aircraft and loading it into the chemical tanks, or canisters, on the aircraft.

Figure 1: Yamaha RMAX

Source: Yamaha

The aircraft had been operating normally that day for about 1 hour and 15 minutes of flight time. At about 1400 Eastern Standard Time (EST), the aircraft was about 2 to 3 m above the ground returning to land, when the pilot and loader heard a ‘clunk’. The aircraft started yawing to the left and descending. The pilot selected opposite direction yaw input (right rudder servo), but the aircraft did not respond. The aircraft collided with terrain upright but in a nose-down attitude and then rolled onto its side, resulting in substantial damage (Figure 2). The pilot did not receive any warnings on the aircraft’s ground control station prior to the accident.

Subsequent inspection revealed that the tail rotor had separated from the aircraft and landed about 30 m from the rest of the aircraft.

Figure 2: Damage to the RMAX

Source: Yamaha

Post-accident inspection

The manufacturer found that the tail rotor shaft had fractured, resulting in the tail rotor detaching from the aircraft (Figure 3).

Figure 3: Tail rotor showing fracture location

Source: Yamaha

The manufacturer assessed that the fracture had probably existed for some time, as one section of the fracture site was smooth, indicating a pre-existing fracture. Another section of the fracture was rough indicating the failure occurred during the accident flight (Figure 4). The tail rotor blade (Figure 3) probably struck the tail cover after the shaft failed, as this allowed excessive movement in the tail rotor head.

Figure 4: Fractured tail rotor shaft

Source: Yamaha

Manufacturer investigation report

The manufacturer had conducted routine maintenance on the aircraft in October 2016. At that time, they found chips in the tail rotors and a broken antenna (fitted to the tail of the aircraft). The manufacturer replaced the antenna and tail rotor blades but was unable to determine how long the aircraft had been operating with the damage to the blades. Damage to the tail rotor blades may have caused an imbalance and extra load on the tail rotor shaft.

The manufacturer found the following factors may have contributed to the failure of the shaft:

• Impact with a small branch at the time the blades sustained chip damage.
• Possibly flying with rotor blades out of balance after the first impact, for an unknown period.
• Other damage to the aircraft indicative of mishandling during transport, which may have resulted in stress fractures to the rotor shaft.

Findings

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

• The tail rotor drive shaft probably failed due to an existing fracture, resulting in the aircraft colliding with terrain.

Safety action

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

Aircraft manufacturer

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

Communication and reporting hub

Yamaha Motor Australia (YMA) is implementing an online form so that operators can send information and notification of incidents directly to Yamaha operations and maintenance departments.

YMA will modify operator’s manuals to better reflect handling standards.

Safety message

This accident highlights the importance of reporting all incidents and accidents, particularly to ensure adequate inspection and maintenance is conducted before returning the aircraft to operations.

Aviation Short Investigations Bulletin Issue 61

About this report Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, a limited-scope, fact-gathering investigation was conducted in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2017 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

__________

1. Yamaha RMAX is a remotely piloted helicopter, body length 2.75 m (3.63 m including rotor), with a load capacity of 28 kg.

What happened

At about 1500 Eastern Standard Time (EST) on 6 April 2017, a Robinson Helicopter R44 II, registered VH‑MQE (MQE), departed from Melanie Camp landing area, Queensland. The pilot and three passengers were on board the scenic charter flight.

After about half an hour into the scenic flight, the pilot commenced a large orbit around a lake that was located about 15 km NE of Melanie Camp. They turned downwind at about 550 ft above ground level (AGL), with an airspeed of about 65 knots and the main rotor RPM was about 101 per cent. About 15 seconds later, the main rotor low RPM horn sounded through the pilot’s headset. The pilot observed the main rotor low RPM warning light illuminate and a rapid decrease in main rotor speed. The pilot advanced the engine throttle and lowered the collective^[1] but found that this made little difference with no increase in main rotor speed even though full engine power was applied. Shortly afterwards, the pilot initiated an autorotation^[2] and prepared to land on a beach.

As the helicopter approached the landing spot, the pilot arrested the helicopter’s rate of descent and the skids contacted the sand in a run-on landing.^[3] After touchdown, the helicopter continued to travel forward about 3 m before the left skid dug into soft sand, which resulted in a dynamic roll over.^[4] The helicopter came to rest on the left side (Figure 1). The pilot unfastened their seat belt and noted that the engine was not operating. They turned the fuel selector to off, moved the engine throttle to idle cut off, and turned off the engine magneto switches and the electrical master switch. The pilot and three passengers exited the helicopter through the right forward and aft exits.

About 40 minutes later, a company helicopter that had also been flying in the area located them. There were no injuries, and the helicopter was substantially damaged (Figure 1).

Figure 1: VH-MQE accident site

Source: Pilot

Pilot comment

The pilot provided the following comments:

• They had flown in this area previously. On the day of the accident, they had flown MQE to Coen Airport to pick up the passengers and flown back to Melanie Camp landing area without any issues.
• They were using a noise-cancelling headset (active noise reduction), which cancelled out any ambient noise. The pilot noted that if they did not have this type of headset they may have been able to hear if there were any unusual engine noises.
• At an altitude of about 550 ft they felt that there was insufficient height to position the helicopter into wind for landing. From that height, it was not possible to estimate the slope or the nature of the landing surface. After the landing, the pilot determined that the sand was very soft with a slight downslope towards the direction of the landing.
• At about 10 minutes prior to the main rotor low RPM warning, the clutch light had illuminated. The light extinguished in about 4 seconds, which was within the normal operating limits for the clutch light. The pilot indicated that there had been no other issues with the clutch mechanism during the day.
• The helicopter had sufficient fuel for the flight and was within the weight and balance limits.
• They had not experienced such a dramatic decrease in main rotor RPM before, despite conducting practice autorotations.

Operator comment

The operator reported that subsequent to the accident, the helicopter sustained substantial damage due to ocean tide (Figure 2). The operator was not able to provide any information in relation to any mechanical defects that may have contributed to the accident.

Figure 2: Subsequent damage due to the ocean tides

Source: Operator

Previous accident

Another ATSB investigation (AO-2012-096 - Ditching involving Robinson R44, 83 km N of Horn Island Airport, Queensland) documented the accident pilot using a noise-cancelling headset on the flight. The accident pilot believed that the headset may have dampened any abnormal engine sounds. Consequently, they only became aware of the engine problems when the engine governor failed.

Safety analysis

Due to the nature of the subsequent damage to the helicopter after the accident the integrity of the helicopter systems prior to the accident were not determined. Consequently, the reason for the loss of main rotor speed was not determined.

The pilot indicated that if a noise-cancelling headset was not used then they would have been able to hear the ambient noises and detect any changes in the ‘normal’ sounds of the helicopter.

Findings

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

• At about 550 ft, after the main rotor low RPM warning system activated, the pilot initiated an autorotation and the helicopter rolled onto the left side after landing. The reason for the main rotor low RPM warning was not determined.
• The pilot was using a noise-cancelling headset that may have masked any abnormal sounds from the helicopter prior to the low rotor RPM warning.

Safety message

The noise-cancelling headset worn by the pilot may have masked changes in the ‘normal’ sounds of the helicopter. The Civil Aviation Safety Authority (CASA) Airworthiness Article 1-43 Noise Isolating Headsets highlights that noise attenuating and noise-cancelling headsets can in some circumstances reduce the effectiveness of aural cues, such as abnormal noises, which might give some warning of unusual operations.

About this report Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, a limited-scope, fact-gathering investigation was conducted in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2017 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

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1. Collective is the primary helicopter flight control that simultaneously affects the pitch of all blades of the lifting rotor. Collective input is the main control for vertical velocity.
2. Autorotation is a condition of descending flight where, following engine failure or deliberate disengagement, the rotor blades are driven solely by aerodynamic forces resulting from rate of descent airflow through the rotor. The rate of descent is determined mainly by airspeed.
3. A run-on landing refers to where the helicopter still has forward speed.
4. Dynamic rollover is when the helicopter starts to pivot laterally around its skid or wheel.

Aviation Short Investigations Bulletin - Issue 62

What happened

On 2 April 2017, at about 1730 Eastern Standard Time (EST), a Virgin Australia ATR - Gie Avions De Transport Regional ATR72-212A aircraft, registered VH-FVL, departed Moranbah for Brisbane, Queensland on a scheduled passenger service. There were two flight crew, two cabin crew and 38 passengers on board the aircraft. The captain was the pilot flying (PF) and the first officer was the pilot monitoring (PM).^[1] The flight also acted as line training for the first officer.

While in the cruise, air traffic control (ATC) cleared the aircraft for the LAVEG ONE standard arrival route for runway 19 at Brisbane Airport. Weather conditions were clear and at 5,700 ft the crew established visual contact with the runway. ATC then gave them radar vectors to intercept the final approach leg.

At around 2,500 ft on descent, the captain disconnected the autopilot and manually flew the aircraft. ATC instructed the crew to track to a 5 NM (9.3 km) final approach leg for runway 19 and cleared the aircraft to descend to 1,700 ft for a visual approach. At 2,300 ft, the captain directed the first officer to select flap 15 and to set 140 kt on the automatic flight control system. The first officer then confirmed that this had been completed. The landing gear was extended soon after.

While the aircraft was turning onto the final approach leg, the captain directed the first officer to select flap 30, set the airspeed indicator bug to the approach speed (V_APP),^[2] and start the before landing checklist. The first officer completed a radio call with ATC, moved the flap selection lever (Figure 1), set the approach speed (104 kt) and responded ‘V approach set’, and then started the checklist.

Figure 1: Location of flap lever on ATR72

Source: Virgin Australia

As the aircraft descended on the final approach leg, the crew noticed that the aircraft was not performing as expected. The captain had to keep adjusting the aircraft attitude and engine torque setting to control the speed. Passing about 1,000 ft, the captain recognised that the speed was too high, but thought that this could be corrected by 500 ft and continued the approach. The first officer also noticed the unusually high speed and called out ‘speed’ to alert the captain.

The flight crew had no recollection of completing the before landing checklist or completing the callout at 500 ft to ensure that aircraft was in a stabilised approach.^[3] Passing 173 ft, the enhanced ground proximity warning system^[4] (EGPWS) activated with the alert, TOO LOW FLAP. The captain immediately conducted a missed approach. During the subsequent climb, the captain called ‘flap 15, check power’ and the first officer responded accordingly.

When the aircraft achieved a positive rate of climb, the captain called ‘positive rate, gear up’. ATC cleared the aircraft to climb and then vectored them for a right base leg to conduct the same approach to runway 19. At this time, the first officer commented to the captain a concern that they may have left the flap at 15. After landing, the captain decided to stand the crew down and not conduct the next two sectors.

Recorded data

The operator extracted the flight data from the aircraft’s quick access recorder. It was recorded that the aircraft commenced the turn onto the final approach at 1,720 ft above the airport and was at 1,729 ft when the flaps lever was moved from 15 to 0 degrees at a calibrated air speed (CAS) of 139 kt.

At 900 ft, the air speed had increased to 148 kt and the aircraft was low on the approach. At 542 ft the aircraft had slowed to 123 kt, which coincided with the thrust lever angle set to idle.

Immediately after the TOO LOW FLAP warning at 173 ft, the thrust lever was moved to the go around position and the flap lever moved from flap 0 to flap 15.

The stall speed for the aircraft at flap 0 was about 106 kt at the estimated approach weight of 18 tonnes. The V_APP speed was set at 104 kt, which was below the flap 0 stall speed. The minimum speed recorded on approach was 114 kt at 507 ft.

The stick-shaker^[5] activates at 15.9 degrees angle of attack^[6] and the maximum angle of attack reached during the approach was 14.6 degrees.

Flap procedures

The operator’s ATR 72-500 standard operating procedures stated that all normal landings are conducted using flap 30. On approach, the pilot flying must call ‘flaps 30, set speed bug V approach’. The pilot monitoring is then required to check the speed, select flap 30, monitor the extension of the flap, and set the speed bug to V_APP and call ‘[speed] set’. The pilot flying then calls out the before landing checklist for the pilot monitoring to action. The last item on the before landing checklist is for both crew to check that flap 30 has been set.

The flap lever is in the 12 o’clock position for flap 0, in the 2 o’clock position for flap 15, and in the 5 o’clock position for flap 30. The flap position is also shown on the flap indicator where the needle points at 0, 15, or 30 (Figure 2).

Figure 2: A screen capture from the operator’s flight data showing the flap indicator positioned at 0 degrees while the aircraft was passing 1,000 feet on descent

Source: Operator, modified by the ATSB

Stabilised approach criteria

The operator’s stabilised approach criteria included that all approaches shall be stabilised by 1,000 ft above ground elevation. However, in terms of speed, if the pilot-in-command is confident the speed target will be achieved by no later than 500 ft above field elevation, the approach can continue.

The speed criteria is that the aircraft must be within -5 to +10 kt of the speed target.

If the speed remains outside the stabilised criteria at 500 ft above field elevation, or if at any time before it becomes apparent the stabilised criteria will not be met, then a go around must be initiated.

The VAPP set for flaps 30 on the day was 104 knots. At 507 ft, the airspeed was 114 kts, which was within the stabilised approach criteria. However, at 358 ft, the airspeed had increased to 128 kts.

The go around was initiated at 173 ft at an airspeed of 121 kts.

Captain’s comments

The captain provided the following comments:

The captain recalled seeing the first officer’s hand reaching out and grasping the flap lever when instructed to set flap 30, but was also busy hand flying the aircraft at the time.

While the aircraft is climbing on a go around, it is the pilot monitoring’s responsibility to call ‘positive rate’, but there was no call from the first officer so the captain made the call.

When they recognised that the aircraft was performing unusually, the captain thought it was an issue with the aircraft power settings because the aircraft was descending below the approach path.

Normally, both the pilot flying and pilot monitoring would check the flap settings when it is called in the checklist by checking the position of the flap lever, then the flap indicator, and say ‘set’. However, because the captain was busy controlling the aircraft, they may not have checked.

The first time the captain became aware that the flap was set to 0 degrees was during a review of the flight data animation produced by the operator.

The captain completed a fatigue report after the flight, although later reported not feeling overly tired during the flight. The captain had arrived at the airport to sign on at 1140 instead of 1340, due to confusion around the rostered flight time. However, to be safe the captain decided that the crew would not continue onto the next destination.

There are inherent risks with visual approaches at night, given that they are not using the instrument landing system.^[7]

First officer’s comments

The first officer provided the following comments:

The workload of the crew increased during the approach when there was a combination of turning onto the final approach path, conducting a visual approach, managing radio calls with ATC and responding to the unexpected aircraft performance.

Flap settings are generally confirmed through the completion of the before landing checklist, whereby the flap lever and indicator must be visually checked. However, in this case, this part of the checklist happened during a high workload period, and it was subsequently rushed. This checklist item may have been missed.

The first officer recalled looking at the flap indicator and seeing movement, but may have wrongly assumed that the flaps were moving to flap 30 in lieu of flap 0.

Previous occurrences

A search of the ATSB’s database found the following occurrences where the incorrect flap setting was selected on approach:

On 28 July 2011, the crew of an Airbus A320 was on approach to Melbourne, Victoria (ATSB investigation AO-2011-089).^[8] The approach brief included the requirement for flap 2^[9] to be selected. At about 245 ft, the captain realised the landing checklist had not been completed and the crew received an EGPWS warning TOO LOW FLAP. The captain identified the aircraft was not in the landing configuration, including flaps and called for a go-around.

On 24 July 2013, the crew of an Airbus A320 was on approach to Newman Airport, Western Australia (ATSB investigation AO-2013-149).^[10] Shortly after passing 500 ft above ground level, the crew received an EGPWS warning TOO LOW FLAP. Full flap was selected at about 185 ft and the aircraft landed shortly after.

On 2 April 2017, the crew of a Boeing 737 were on approach to land on runway 19 at Brisbane Airport (ATSB occurrence 201701579). At 1,400 ft the call for flap 30 was made, but flap 25 was selected. The landing checklist was commenced at 1,200 ft but interrupted by the issue of a landing clearance from air traffic control. The checklist was recommenced and completed at 1,000 ft, however, the flap setting was not identified. At 300 ft, the EGPWS warning TOO LOW FLAP activated and the crew conducted a missed approach.

Safety analysis

The approach and landing is known to be a phase of flight with a high workload due to the number of tasks to be completed in addition to monitoring the flight path. During the approach, as the aircraft was turning, the first officer was responding to a radio call and completing a checklist. It is likely that the first officer inadvertently selected the flap lever up from 15 to 0, instead of down to 30, and did not crosscheck the flap indicator before moving on to the other tasks. This inadvertent action led to an increase in the aircraft’s airspeed, which the flight crew recognised, but at the time were unable to ascertain why. The incorrect flap setting was not detected and a go around initiated after a ground proximity warning alerted the crew to an incorrect configuration at 173 ft.

Due to the high workload in managing the aircraft’s performance on approach, the crew did not detect the aircraft’s speed was exceeding the stabilised approach criteria of VAPP + 10 kts or that the aircraft was incorrectly configured with flap 0. Although at 507 ft, the airspeed was 114 kts, which was within the stabilised approach criteria with the VAPP set at 104 kts, at 358 ft, the airspeed had increased to 128 kts, which was outside the stabilised approach criteria.

Since the incorrect flap setting was not detected by the crew on approach, had they managed to slow the aircraft to the VAPP of 104 kts for flap 30, they would have been 2 kts below the stall speed for the actual flap setting (106 kts).

Findings

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

• During the approach, the first officer moved the flap lever up from flap 15 to flap 0, instead of from flap 15 to flap 30 as intended. This resulted in an unstable approach.
• The crew did not identify the incorrect flap setting until the ground proximity warning system alerted them to an incorrect configuration, likely due to workload.

Safety message

Approach and landing have a higher workload compared to other phases of flight because of the continuous monitoring of aircraft parameters and the external environment to maintain a stable approach. This investigation highlights the potential impact crew workload has on flight operations as it can lead to adding, shedding, or rescheduling actions. Handling approaches to land continues to be a safety priority for the ATSB.

About this report Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, a limited-scope, fact-gathering investigation was conducted in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions. Publishing information Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2017 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

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1. Pilot Flying (PF) and Pilot Monitoring (PM) are procedurally assigned roles with specifically assigned duties at specific stages of a flight. The PF does most of the flying, except in defined circumstances; such as planning for descent, approach and landing. The PM carries out support duties and monitors the PF’s actions and aircraft flight path.
2. Final approach speed (VAPP) is the speed on the final approach in landing configuration.
3. On the glidepath at correct airspeed, correctly configured, all checklists and paperwork complete.
4. An aircraft system that uses aircraft inputs with onboard terrain, obstacle, and airport runway databases to predict potential conflicts between the aircraft’s flight path and terrain or an obstacle.
5. A tactile warning to alert the flight crew that the aircraft was near an aerodynamically-stalled condition of flight.
6. The angle between the oncoming air or relative wind and a reference line of the aeroplane or wing.
7. A standard ground aid to landing, comprising two directional radio transmitters: the localiser, which provides direction in the horizontal plane; and the glideslope, for vertical plane direction, usually at an inclination of 3°. Distance measuring equipment or marker beacons along the approach provide distance information.
8. www.atsb.gov.au/publications/investigation_reports/2011/aair/ao-2011-089/
9. Flap 2 is equivalent to 15 degrees position.
10. www.atsb.gov.au/publications/investigation_reports/2013/aair/ao-2013-149/

Aviation Short Investigations Bulletin - Issue 62

What happened

On 1 April 2017, the pilot of a Cessna R182 aircraft, registered VH-JXX, conducted a private flight from Broken Hill to Bathurst, New South Wales, with one passenger on board.

The aircraft arrived overhead Bathurst Airport at about 1130 Eastern Daylight-saving Time (EDT) and the pilot elected to join the circuit on a left downwind for runway 35. The pilot reported that the approach was normal, and that they aimed to touch down slightly beyond the runway threshold.

Due to a crosswind of about 8 kt, the pilot recalled that the left main wheel touched down immediately before the right. The propeller then struck the runway and the nose landing gear collapsed. The aircraft skidded a short distance before coming to rest on the runway.

The aircraft sustained substantial damage and the pilot and passenger were uninjured (Figure 1).

Figure 1: VH-JXX showing damage to the propeller and nose landing gear

Source: Aircraft owner

Pilot comments

The pilot commented that the approach seemed normal, all indications were normal, and the landing did not feel particularly hard. The first time they were aware something was not normal was when the nose of the aircraft contacted the runway. They had lowered the landing gear on downwind and confirmed the green light indicated the gear was safely down and locked, and had also verified the main wheels were down by doing a visual check.

Post-accident inspection

An aircraft maintenance engineer inspected the aircraft after the accident. The nose landing gear had collapsed, and the gear doors were broken. The cowl flaps were damaged, the firewall was buckled and the area under the floor in the area near the pedals was bent. There was no evidence of any fault other than the damage sustained in the impact.

Findings

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

• The aircraft probably landed in a nose-low attitude resulting in a propeller strike and damage to the nose landing gear.

Aviation Short Investigations Bulletin Issue 61

About this report Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, a limited-scope, fact-gathering investigation was conducted in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2017 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

What happened

On the afternoon of 30 March 2017, the flight crew of a British Aerospace Jetstream 3206 aircraft, registered VH-OTE, prepared to conduct Pelican Airlines flight FP314 from Canberra Airport, Australian Capital Territory, to Newcastle Airport (Williamtown), New South Wales. The flight crew comprised the captain and the first officer.

All pre-flight checks, taxi and engine run-ups were normal, however the left engine single red line computer was unserviceable (see Single red line section below). This did not prevent the aircraft from operating the flight but meant that the flight crew had to set the power of the engine using the manufacturer’s documented torque tables.

At about 1545 Eastern Daylight-saving Time,^[1] the aircraft departed from runway 17 at Canberra Airport. As the aircraft passed about 7,000 ft on climb, the flight crew observed that the right engine was producing about 40 per cent torque, while the left was producing about 65 per cent torque. Fuel flow to the right engine and exhaust gas temperature (EGT) were also slightly lower than the left. The captain tried to use the power lever to increase torque to the right engine but it did not respond to produce greater than 40 per cent.

The first officer retrieved the appropriate section of the quick reference handbook (QRH), which they then actioned. The most common cause of low torque was icing on the compressor inlet pressure (P2T2) sensors (Figure 1). The QRH response was to turn on heat to melt the ice and wait 5 minutes to see if there was a power response.

Figure 1: Schematic diagram of Garrett TPE331 engine showing P2T2 inlet

Source: FAAsafety.gov, modified by the ATSB

After completing the actions and waiting the prescribed 5 minutes, there was still no positive response in the right engine to moving the power lever so the crew elected to return to Canberra Airport. At about 1559, passing about 9,000 ft, the first officer advised air traffic control (ATC) that they intended to return to Canberra and ATC provided a clearance for their approach.

About 5 minutes later, as the crew prepared for the approach to return, normal power returned to the right engine. Both engines were now responding to power lever inputs over the full range. Hence, the flight crew assessed that icing had been the cause of low torque and it had taken longer than 5 minutes for the ice to melt and the engine to respond.

At about 1604, when at about 9,000 ft, the first officer advised ATC that they had rectified the situation. The first officer advised that they intended to continue to Newcastle, and subsequently obtained a clearance to reroute.

Less than 2 minutes after turning the aircraft to track towards Newcastle, the right engine issue recurred. The captain verified that they could not get more than 40 per cent torque but that by pulling the power lever back, they could get flight idle torque. In those circumstances, the flight crew elected to return to Canberra but not to shut down the right engine.

The flight crew did not declare an emergency,^[2] conducted a normal approach and, at about 1621, the aircraft landed on runway 17 at Canberra Airport without further incident.

Analysis

Flight crew assessment of issue

The aircraft was approaching freezing levels, with the outside temperature about 5 °C at the time the right engine torque decreased. The aircraft was not in visible moisture but there were showers in the area. The captain thought at the time that due to the venturi effect (lowering the temperature of the air flowing into the engine inlets), it could have been the start of freezing conditions for the engine and that they would have been turning on the anti-icing before long. The captain assessed that it was therefore possible that the P2T2 (and P3T3) inlets had frozen over and caused the reduction in available power.

Once the flight crew had turned the anti-icing system on (in accordance with the QRH checklist), they left it on. Therefore, when the problem recurred, they concluded that icing was not the cause.

Decision to return

The crew assessed that the engine was producing enough torque to operate the aircraft safely. As holding fuel was required in Newcastle and the cloud base was down to the minima specified for the approach, however, they elected to return to Canberra. There were no handling issues with the aircraft, and no adverse yaw. The crew assessed that with 40 per cent torque on the right engine, they could probably still cruise at the planned altitude of FL 150. ^[3]

During the descent, in accordance with normal procedures, the flight crew reduced the torque on both engines to 40 per cent, then 20 per cent on final approach and 12 per cent for landing. As they were able to reduce power on the right engine, the approach was therefore conducted without any asymmetric thrust.

Single red line

The single red line (SRL) simplifies how the pilot sets the engine torque. The SRL computer calculates the temperature difference between the turbine inlet temperature and exhaust gas temperature based on variables including pressure, altitude and true airspeed.

Without the SRL functioning, the flight crew use the manufacturer’s torque tables to determine the required values and, importantly, to ensure maximum EGT is not exceeded. The flight crew also used trend monitoring data (available in the cockpit) to see the relative torque and maximum EGT for each engine.

During the occurrence flight, the flight crew of VH-OTE were monitoring the EGT closely. According to the captain, the SRLs in the J3206 aircraft malfunctioned quite frequently but were readily rectified by maintenance engineers.

Weather

The captain reported that although there were some showers in Canberra at the time, the weather was ‘not too bad’. In Newcastle, however, there were severe storms, strong rain and winds, and the visibility and cloud were down to the approach minima. There was up to 60 minutes of holding fuel required in Newcastle due to the weather.

Engineering report

After the incident, aircraft maintenance engineers conducted ground runs of the engine. The engineers found no defects with the anti-ice valve, and the torque signal conditioner was normal. The engineers increased the maximum fuel flow setting on the fuel control unit (FCU) by 10 kg per hour and subsequent ground runs were satisfactory.

The aircraft subsequently operated several sectors with both engines operating normally. Three days later, the aircraft underwent scheduled maintenance. The maintenance engineers found that the No. 2 (right) engine FCU P3 piston was leaking into the P2 section. The P3-P2 is a dry section of the FCU so that any leaks are air-to-air.

The FCU was sent to an engine overhaul facility in the United States for further inspection. The FCU had accumulated 2,504.87 hours since new and had run for 1,713.97 hours while installed on VH-OTE. The inspection found corrosion on the P3 piston sleeve, which was replaced, along with a new piston seal and ring as part of the standard overhaul process.

The P3 air pressure positions the fuel metering valve to ensure the correct fuel to flow ratio. The facility engineers advised that an unresponsive power lever was not a normal result of a P3 piston seal leakage. The most frequent fault reported for P3 piston seal leakage was high flight idle fuel flows, which did not occur in this case.

The facility engineers had previously advised the aircraft operator that the engine inlet P2T2 sensor was known to be a possible cause of a non-responsive power lever and lack of control of engine power. An inspection of the sensor was carried out but no defect was found.

The FCU and P2T2 sensor were replaced and the issue did not recur.

Engine manufacturer comments

Honeywell advised that leakage of the FCU P3 piston into the P2 section can result in the inability of the FCU to reach the max fuel schedule. The symptoms of this condition would be similar to icing of the P2 inlet due to the increased pressure within the P2 section.

Threat and error management

When the problem occurred, the captain asked the first officer to retrieve the QRH. The first officer then read the relevant section and together the flight crew completed the actions. When the problem was not resolved after the prescribed 5-minute period, the flight crew discussed their options. They assessed that the weather in Newcastle was unacceptable, particularly with the possibility of having to conduct a missed approach if they were unable to get the required visibility at the minima. Therefore, the flight crew decided to return to Canberra Airport.

The flight crew also discussed the possibility of having to conduct a go-around. They assessed that a go-around with 40 per cent torque on the right engine was possible, that they would have been able to manage the asymmetric thrust, and that they would have been able to remain visual in the Canberra circuit area. There was a greater likelihood of having to go around at Newcastle due to weather, which reaffirmed their decision to return to Canberra.

Previous incident

The ATSB investigated an in-flight engine shutdown involving Pelican Airlines British Aerospace Jetstream 32 aircraft, registered VH-OTQ, that occurred in December 2016 (AO-2016-171). Shortly after the aircraft reached its cruising altitude, the right engine EGT gauge indicated a higher temperature than normal. The power lever did not respond to pilot inputs.

In accordance with the QRH, the flight crew shut down the right engine and returned to Newcastle Airport, New South Wales, from where they had departed. The flight crew did not declare a PAN, but the controller initiated an alert phase^[4] during the aircraft’s approach.

In that incident, the fuel control unit’s bearing cage was broken, with many small fragments found to be interfering with the unit’s operation. The bearing cage held the bearing balls and kept them separated from each other.

Findings

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

• During climb, the right engine was limited to a reduced torque value and the engine did not respond to the pilot’s power lever inputs to increase torque. Due to this reduced torque and poor weather conditions in Newcastle, the flight crew elected to return to Canberra.
• The reduced engine torque was consistent with leakage of the fuel control unit P3 piston into the P2 section.
• The flight crew used effective communication and threat and error management techniques in responding to the issue. Although making an urgency (PAN) broadcast would certainly have appropriately alerted air traffic control (ATC) to the situation, the flight crew did not consider a PAN broadcast was necessary in this case as they had advised ATC of the reduced engine torque, and because a normal approach was possible.

Safety message

This incident provides a good example of effective threat and error management techniques. The flight crew were faced with an abnormal situation and made the decision to turn back to Canberra in a collaborative way.

It is important to broadcast a PAN or MAYDAY call, as appropriate, when time permits to alert air traffic control to an emergency situation. In response, air traffic controllers will provide assistance such as a priority landing to allow an aircraft to land as soon as possible. Airservices Australia publications In-flight emergencies and What happens when I declare an emergency provide relevant information.

About this report Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, a limited-scope, fact-gathering investigation was conducted in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2018 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

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1. Eastern Daylightsaving Time (EDT): Universal Coordinated Time (UTC) + 11 hours.
2. 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.
3. Flight level: at altitudes above 10,000 ft in Australia, an aircraft’s height above mean sea level is referred to as a flight level (FL). FL 150 equates to 15,000 ft.
4. Alert Phase (ALERFA): an emergency phase declared by the air traffic services when apprehension exists as to the safety of the aircraft and its occupants.

What happened

On the morning of 29 March 2017, a Piper PA-31-350 aircraft (Figure 1), registered VH-JQS, was on a private visual flight rules flight from Moorabbin, Victoria (Vic.) to Barwon Heads/Geelong aeroplane landing area (Barwon Heads ALA),^[1] Vic. The pilot was the only person on board.

Figure 1: The occurrence aircraft, VH-JQS

Source: www.cqplanespotting.blogspot.com.au

At about 1015 Australian Eastern Daylight Time (AEDT), the aircraft was on approach to runway 36 at Barwon Heads ALA. The aircraft was configured with the landing gear extended and full flaps selected.

At a distance of about 0.5 NM (0.9 km) from runway 36, the pilot detected the aircraft becoming slightly low on the desired approach profile. The pilot retracted the flaps by 10° in an attempt to reduce the rate of descent. As the aircraft approached runway 36, the pilot noticed the aircraft was still lower than intended and decided to increase power. The pilot looked down momentarily at the throttle quadrant as they put their hand on the throttle control. As they looked back up, they observed a truck approaching from the left along Barwon Heads Road (Figure 2).

The pilot applied full power to conduct a go-around.^[2] As full power was applied, the aircraft passed over Barwon Heads Road and the left main landing gear impacted the truck. The pilot observed the truck continue on Barwon Heads Road without stopping and the pilot continued with the go-around. The pilot elected to leave the landing gear extended in case it had sustained damage.

Figure 2: Barwon Heads/Geelong aeroplane landing area (ALA).

Source: Google Earth, annotated by ATSB

After completing the go-around, the pilot conducted two low passes over the airfield to determine the extent of any damage. During the first pass, the pilot contacted another pilot on the ground who had recently landed. The pilot on the ground was able to confirm that all three landing gear appeared to be intact. On the second pass, the pilot yawed^[3] the aircraft left and right to ensure the landing gear was secure.

The pilot subsequently landed the aircraft without incident. The pilot was uninjured, and the aircraft sustained minor damage (Figure 3).

Figure 3: Damage to left main landing gear of VH-JQS.

Source: Pilot

Pilot comments

The pilot of VH-JQS provided the following comments:

• They had flown into Barwon Heads regularly over the previous five to six years and were familiar with the airport, including the displaced threshold and the vicinity of the Barwon Heads Road.
• In addition to flying duties, the pilot was also working as the company maintenance controller, and had recently taken on extra administrative duties. They stated that they were distracted during the incident flight by these additional pressures.
• The desired approach profile was about a 3° (5 %) descent profile. The pilot was aiming to land about a quarter of the way into the runway in order to ensure clearance over Barwon Heads Road.
• There were no issues with visibility or cloud cover but there was a gusting wind from the north-west. The aircraft became low on approach due to turbulence and windshear.
• When they realised they were becoming low on the approach the pilot reduced flaps by 10° rather than apply power. This was done to avoid reheating the turbo chargers as they had already cooled.
• The truck was not detected earlier as it had been obscured by a row of trees to the south-west of the airport.

Truck driver comments

The driver of the truck provided the following comments:

• The truck driver felt what they thought was downwash from the aircraft but was unaware that contact had been made. At no time did they see the aircraft. It was only when the truck driver reached their destination that they saw the impact marks and damage to the top of the truck and realised contact had been made.
• The truck was 3.950 m in height.

Airport operator comments

The airport operator provided the following comments:

• In late 2014, Barwon Heads ALA underwent a number of upgrades. These upgrades included sealing of runway 36 and improvements to the runway lighting. As part of these upgrades, the airport operator also proposed lengthening runway 36 to the north so that the displaced threshold could be moved further north. This would have allowed more clearance for aircraft flying over Barwon Heads Road. The operator stated that this aspect of the application was rejected by the local council (see Local council comment below) so the application went ahead without this component.
• The Aeronautical Information Package (AIP) En Route Supplement Australia (ERSA) states that prior permission is required to land at Barwon Heads ALA. This was done to convey information regarding the airport and runways. This information included the displaced threshold and road to the South of runway 36. The airport information was also available online (YBRS Runway Information - Barwon Heads Airport).

Local council comment

The local council commented that in general, the use of land as a transport hub (airport) is prohibited in a farming zone. However, the existing ALA site had operated as an airport for a period of almost 40 years and had existing use rights across the entire lot. These existing use rights, however, did not extend to the land north of the runway. Because of this, the council could not consider the part of the airport operator’s application relating to the extension of the runway to the north.

Adjusting decent rate during approach

The CASA flight instructor manual states that for an engine assisted approach:

The use of power on the approach enables the rate of descent to be adjusted safely over a very wide range.

Additionally, the Civil Aviation Authority New Zealand circuit training guidance states that:

The approach path is monitored by reference to the correct runway perspective. Throughout the descent the aiming point, commonly the runway numbers or threshold, is monitored and the power adjusted as required to maintain a steady rate of descent to touchdown.

Power controls the rate of descent

With the aeroplane trimmed to maintain the required attitude (airspeed), if the aiming point moves up the windscreen, the aeroplane is undershooting – increase power. If the aim point moves down the windscreen, the aeroplane is overshooting – decrease power.

Runway 36 displaced threshold

The Civil Aviation Safety Authority (CASA) provides guidance regarding the recommended minimum physical characteristics of landing areas in the Civil Aviation Advisory Publication (CAAP) 92-1(1): Guidelines for aeroplane landing areas.

Both ends of a runway, not intended solely for agricultural operations, should have approach and take-off areas clear of objects above a 5 % slope for day and a 3.3 % slope for night operations.

Barwon Heads Road is in close proximity to runway 36 (Figure 2). The start of runway 36 was about 25 m from the road, and the displaced threshold was 78 m from the road. Additionally, the elevation of the runway at the threshold was 0.31 m higher than that of the road. Using the 5 per cent approach recommended by CAAP 92-1, a distance of 78 m results in a height of 3.9 m (see Figure 5) over the runway elevation, providing a total road-crossing height of 4.21m. The VicRoads vehicle height limit in Victoria for road vehicles was 4.6 m.

Figure 5: Diagram showing a 5 per cent (3 degree) approach profile for Barwon Heads runway 36 and the proximity of Barwon Heads Road. A 5 per cent descent gradient aiming at the threshold results in aircraft passing over Barwon Heads Road at 4.21m which is lower than the VicRoads vehicle height limit of 4.6m.

Source: ATSB

While this incident occurred during daytime, runway 36 at Barwon Heads ALA is available for night use and is equipped with pilot activated lighting. Using the 3.3 per cent slope recommended by CAAP 92-1 for night operations, a distance of 78 m results in a height over Barwon Heads Road of 2.88 m (including the 0.31 m elevation difference). A review of the ATSB’s aviation occurrence database showed no similar occurrences on approach to runway 36 at Barwon Heads ALA have been reported to the ATSB.

Safety analysis

At about half a nautical mile from the runway, the aircraft became low on the approach. When the pilot recognised that the aircraft was too low, they elected to reduce the flap setting by 10° rather than add power. As the aircraft got closer to the runway, the aircraft was still lower than the desired approach profile, at which point the pilot elected to add power to gain height. Despite this action, the aircraft remained below the desired approach profile until it made contact with the truck.

The threshold of runway 36 was 78 m from Barwon Heads Road (Figure 2). Using the 5 per cent approach recommended by CAAP 92-1, a distance of 78 m results height of 3.9 m above the runway elevation. Combining this with the 0.31 m elevation difference, results in a clearance of 4.21 m which is less than the 4.6 m road vehicle height permitted in Victoria. Therefore, a normal approach aiming for the threshold of runway 36 at Barwon Heads can intersect with road vehicles on Barwon Heads Road.

Findings

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

• The aircraft descended below the desired approach profile and the corrective action was not effective in sufficiently reducing the rate of descent.
• The displaced threshold on runway 36 at Barwon Heads does not provide the level of clearance recommended by the Civil Aviation Safety Authority Civil Aviation Advisory Publication 92-1.

Safety message

The guidance provided by CAAP 92-1 regarding the recommended minimum physical characteristics of ALAs is not compulsory. Therefore, pilots should not expect the same conditions and protections at an ALA as they would expect at a registered airport. When preparing to operate to ALAs, pilots should gain as much local knowledge about the landing site as possible. This can be achieved by consulting the ERSA and calling ahead for prior permission and/or airfield information. Aerodrome operators can help facilitate this by distributing relevant information in the ERSA, on their website or by requesting prior permission, as done by Barwon Heads ALA.

This occurrence involved an experienced pilot with over 4,000 hours total flying time and over 1,000 hours as an instructor. Additionally, the pilot had flown into Barwon Heads ALA numerous times previously and was familiar with the displaced threshold and the proximity of the road. Despite this experience, and even with local knowledge, this occurrence resulted in the aircraft impacting a truck while on approach to Barwon Heads ALA. The ATSB’s aviation occurrence database shows that experience does not grant immunity from fatal accidents and in 2013 the ATSB published its sixth report of the avoidable accident series Experience won’t always save you.

Aviation Short Investigations Bulletin - Issue 62

About this report Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, a limited-scope, fact-gathering investigation was conducted in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2017 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

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1. Aeroplane landing area: An area of ground suitable for the conduct of take-off and landing of aeroplanes.
2. Go-around: the procedure for discontinuing an approach to land, is a standard manoeuvre performed when a pilot is not completely satisfied that the requirements for a safe landing have been met. This involves the pilot discontinuing the approach to land and may involve gaining altitude before conducting another approach to land.
3. Yawing: the motion of an aircraft about its vertical or normal axis.

What happened

On the afternoon of 23 March 2017, the pilot of Gippsland Aeronautics GA-8 Airvan, VH-AZH, prepared for a departure from Avoid Island aeroplane landing area (ALA)^[1] (Figure 1), Queensland (Qld) for a passenger charter flight to Mackay, Qld.

The company had elected to split the load of five passengers and cargo between two aircraft, a Cessna 206 and the GA-8.^[2] On board the GA-8 were the pilot and three passengers, along with 30 kg of cargo and 92 kg of fuel, resulting in a take-off weight of 1,521 kg.^[3]

While preparing for the departure, the pilot observed a 5–10 kt wind from the south-east and elected to use runway 14 for take-off. Runway 14 was a grass runway, 800 m long and included a slight rise in the middle. At the end of the runway was a vertical drop of about 2 meters down to a rocky beach.

Figure 1: Avoid Island ALA

Source: Google Earth, annotated by ATSB

At about 1555 Eastern Standard Time (EST), the pilot in the GA-8 commenced the take-off run ahead of the Cessna 206. During the take-off run, the pilot maintained slight back pressure on the control column to minimise the weight on the aircraft nose wheel. The rotation^[4] speed for the take-off was 58 kt. The pilot elected to use a point about halfway along the runway as the decision point for the continuation of the take-off, this point was located just after the crest in the runway. As the aircraft passed the decision point, the pilot noted that the airspeed was about 40 knots and engine indications were normal. As the aircraft performance was satisfactory, the pilot elected to continue the take-off.

As the aircraft continued on the downhill side of the crest, the aircraft encountered a soft patch of runway surface, resulting in a slight deceleration. As performance quickly returned, the pilot did not consider this to be an issue.

As the aircraft approached the end of the runway, just prior to reaching the rotation speed, the pilot felt a significant deceleration. The pilot identified that insufficient runway remained to stop the aircraft, and in an attempt to avoid the aircraft falling over the vertical drop, elected to continue the take-off.

The aircraft did not take-off before overrunning the runway and became airborne as it passed over the vertical drop at a speed of about 50 kt. While manoeuvring to avoid large rocks and obstacles (Figure 2), the pilot maintained a nose high attitude to minimise the effect of any impact. The aircraft was unable to maintain height and descended over about a further 100 m until the landing gear and underside of the rear fuselage impacted rocks. As the aircraft decelerated, the impact through the rudder pedals forced the pilot’s ankle against the control column.

Figure 2: Accident site

Source: Operator, annotated by ATSB

After the aircraft came to rest, the passengers began to evacuate the aircraft. The pilot secured the aircraft and assisted the passengers with the evacuation. After securing the aircraft, the pilot then contacted the pilot of the Cessna 206 and advised them not to attempt to take-off.

The pilot of the Cessna 206 taxied that aircraft to the end of runway 14, contacted emergency services and provided assistance to the occupants of the GA-8.

The pilot of the GA-8 suffered a fractured ankle, the passengers were uninjured in the accident.

Pilot comments

The pilot of VH-AZH provided the following comments:

• The pilot landed on runway 14 at Avoid Island ALA about 15 minutes prior to the accident flight. After landing, the pilot taxied the full length of the runway before turning around to return to the threshold of runway 14 to meet the passengers. While taxing, the pilot did not detect the soft patches in the runway. The pilot observed that the grass was dense and about 100 mm in length.
• Performance calculation charts in the GA-8 pilot operating handbook did not provide for a runway with long wet grass and both an uphill and downhill component. Therefore, the pilot had used the ‘worst case’ scenario when calculating the take-off distance required^[5] for runway 14 at Avoid Island ALA. The pilot calculated the take-off distance required to be 590 m when assuming a two percent upslope for the entire take-off run and short dry grass.
• The wind conditions at the time of the take-off were not consistent. A change in wind speed or direction may have contributed to the accident.
• The company chief pilot operated from Avoid Island ALA three days prior to the accident flight and found the ALA to be in good condition.

Operator comment

The operator of VH-AZH provided the following comments:

• After the accident, the grass on the runway was mowed and the runway was inspected. The operator found the significant deceleration toward the end of the take-off run was the result of an area of soft runway surface and mud. During the pilot’s taxi after the previous landing, and during the accident take-off run, this area had been concealed by grass.
• The pilot had received training at Avoid Island ALA and had recently operated to the ALA.

Weather and prior rainfall

The pilot reported 5–10 kt of wind from the south-east, cloud at about 1,500 ft and patches of drizzle in the Avoid Island area at the time of the accident.

Avoid Island did not have recorded weather observation data. Weather stations at nearby locations, Middle Percy Island and St Lawrence (Figure 3), reported the below rainfall totals^[6] over the days prior to, and the day of the accident (23 March).

Table 1: Rainfall totals at Middle Percy Island and St Lawrence

Figure 3: Avoid Island location

Source: Google Earth, annotated by ATSB

Safety analysis

The Chief Pilot had visited the island three days prior to the accident flight and found the ALA in good condition, however, rainfall over the intervening period created soft patches in the runway surface.

The operator chose to split the load between two aircraft to provide more margin for the operation and the pilot calculated that sufficient runway was available for the GA-8 take-off. However, the soft patches, along with wet grass, prevented the aircraft from completing the take-off in the runway available.

Findings

• The soft patches in the runway surface, concealed by grass, very likely degraded aircraft performance during take-off. The location of the soft patches towards the end of the runway prevented the aircraft taking off before the runway end.

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 action:

Aeroplane landing area management

The operator has taking over management of maintenance of the Avoid Island ALA. This will enable the operator to ensure that the ALA is suitable for proposed operations.

The operator is investigating the feasibility of works to improve drainage on the ALA.

The guidance documents for all regularly used ALAs have been updated and significantly expanded.

More rigorous pilot training of ALA operations will be conducted in future. The operator is investigating the use of an ALA which simulates the conditions of Avoid Island ALA and also has a cross runway to provide for crosswind training and assessment.

Safety message

When operating from an ALA, the pilot must take great care to ensure that the ALA condition is suitable for the proposed operation. ALA operations can present numerous and varied challenges which may affect the safety of flight. In this case, the Chief Pilot had visited the island just three days prior, however, rainfall over those three days had greatly impacted on the serviceability of the ALA. In addition, the dense grass present created difficulties in identifying the soft patches of runway.

The Civil Aviation Safety Authority advisory publication: CAAP 92-1 Guidance for aeroplane landing areas provides the following information on the use of ALAs:

The surface of a landing area should be assessed to determine its effect on aeroplane control and performance. For example, soft surfaces or the presence of long grass (over 150 mm) will increase take-off distances while moisture, loose gravel or any material that reduces braking effectiveness will increase landing distance.

Aviation Short Investigations Bulletin Issue 61

About this report Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, a limited-scope, fact-gathering investigation was conducted in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2017 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

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1. Aeroplane landing area: An area of ground suitable for the conduct of take-off and landing of aeroplanes.
2. The Cessna 206 can be fitted with up to five passenger seats, the GA-8 can be fitted with up to seven passenger seats.
3. The structural maximum take-off weight of VH-AZH was 1,905 kg.
4. Rotation: the positive, nose-up, movement of an aircraft about the lateral (pitch) axis immediately before becoming airborne.
5. Take off distance: The horizontal distance required for an aircraft to accelerate from stationary, take-off and climb over a 50 ft (15 m) obstacle. As runway 14 at Avoid Island ends with small bushes, the remaining climb to 50 ft may be calculated to be conducted over the beach and water after clearing this obstacle.
6. Daily rainfall for the listed day is the 24 hour total rainfall from 0900 on the day prior until 0900 on that day.