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What happened

On 15 May 2015 at about 0135 Eastern Standard Time, an Airbus A319 aircraft, registered VH‑VCJ and operated by Skytraders Pty Ltd, was positioning to commence an approach to runway 16 at Melbourne airport. Following the receipt of a clearance to descend the aircraft to 3,000 ft, the pilot flying (PF) made a number of autoflight mode selections. These mode selections led to the autothrust system disengaging and the engines entering the thrust lock condition. The PF’s actions to correct the condition resulted in an unexpected increase in thrust.

In response to the thrust increase, the PF made a number of pitch-down inputs and retarded the thrust levers. The pitch-down inputs, when combined with the increased thrust, resulted in the aircraft developing a high rate of descent with an accelerating airspeed. The aircraft descended below the cleared altitude and a Terrain Avoidance and Warning System (TAWS) alert activated. The PF responded to the alert by declaring an intent to ‘go around’ and advanced the thrust levers to full power. When the engines responded with increased power, the PF again reacted with pitch-down inputs. A further two TAWS alerts activated before the PF reversed the descending flight path and started to climb the aircraft.

What the ATSB found

The ATSB found that a number of autoflight mode selection errors led to the aircraft’s engines entering the thrust locked condition. The correct procedure when disconnecting the autothrust was not completed, which in turn resulted in the unexpected sudden power increase.

The ATSB also found that the PF likely experienced pitch-up illusions during periods of unexpected and rapid thrust increase. The PF instinctively responded with pitch-down side stick inputs that resulted in the initial high speed and high rate of descent, as well as continued descent after initiating a go-around.

The rapidly changing aircraft state led to the crew experiencing a high workload. This significantly limited their capacity to identify the autoflight system mode changes and respond to the aircraft's high airspeed and high rate of descent.

The pilot monitoring’s ability to identify and influence the rapidly changing situation was likely affected by the non-routine nature of actions of the PF, multiple autoflight system mode changes and alerts, the reduced communication between the crew, and a focus on the flap limitation airspeeds.

Safety message

A pitch-up illusion can affect the most experienced pilot. Ideally, adherence to instrument scan techniques, setting and maintaining known aircraft attitudes for specific phases of flight, and using flight aids such as autopilots and/or flight directors, are all strategies to reduce the risk of responding inappropriately to pitch-up illusions. However, when pilots are experiencing a high workload this can be difficult to achieve. In this case, there are benefits in increasing crew communication, to enable more time to identify issues and consider solutions as well as to facilitate the pilot monitoring’s ability to monitor the situation.

Aviation operators conduct non-technical skills training for their pilots. An occurrence such as this demonstrates the way in which topics such as human error prevention and detection, information processing, decision making and communication continue to be relevant.

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The occurrence

Context

Safety analysis

Findings

Sources and submissions

Glossary

 
General details
Date: 15 May 2015 Investigation status: Completed 
Time: 0137 EST  
Location   (show map):25 km N Melbourne Airport Investigation type: Occurrence Investigation 
State: Victoria Occurrence type: Flight below minimum altitude 
Release date: 24 November 2017 Occurrence class: Operational 
Report status: Final Occurrence category: Serious Incident 
 Highest injury level: None 
 
Aircraft details
Aircraft manufacturer: Airbus 
Aircraft model: A319-132 
Aircraft registration: VH-VCJ 
Serial number: 1880 
Type of operation: Charter 
Sector: Jet 
Damage to aircraft: Nil 
Departure point:Perth, WA
Destination:Melbourne, Vic.
 
 
 
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Last update 24 November 2017