| Occurrence Briefs are concise reports that detail the facts surrounding a transport safety occurrence, as received in the initial notification and any follow-up enquiries. They provide an opportunity to share safety messages in the absence of an investigation. |
What happened
On 2 December 2018, an Airbus A330 aircraft departed Melbourne, Vic. on a scheduled passenger service to Kuala Lumpur, Malaysia.
Prior to take-off, the crew noted prevailing weather conditions could be challenging and it was decided that the captain would be pilot flying for the take-off and hand over to the first officer later during climb. The crew received a departure clearance from runway 16 on the BISON 5 Standard Instrument Departure (SID).
As the aircraft lined up, the crew received a report that the last aircraft to land encountered windshear. The captain assessed that it was safe to depart. Due to possible windshear, it was decided to use maximum take-off thrust[1]. The crew reported a normal take-off. Passing 500 ft above mean sea level (AMSL), the captain engaged the autopilot and reduced the power to climb thrust. The climb rate of the aircraft then reduced and the aircraft levelled off around 760 ft AMSL. The crew, suspecting windshear, retracted the flaps and then set take-off/go around (TOGA)[2] power. The ground proximity warning system “DON’T SINK” alert triggered and the airspeed increased beyond the flap retraction speed up to a maximum of 236 kts until the flaps fully retracted.
The aircraft continued to fly level to a position 4 NM from the airport, 400 ft above ground level, with an airspeed of 276 kts. 45 seconds after initial engagement of the autopilot, the captain then disengaged the autopilot and flew the aircraft manually. The captain commenced a climbing turn to follow the SID. During the turn, the angle of bank increased to a maximum of 46 degrees. The aircraft regained the SID, the autopilot engaged, and the flight continued to depart for Kuala Lumpur.
Post-flight, it was determined that altitude (ALT) mode[3] was selected on the autopilot. This caused the aircraft to level off and accelerate. The crew were not aware of this at the time. It is suspected that the captain inadvertently pushed the ALT button which was not detected by the crew. This resulted in the aircraft levelling off at low altitude and allowed the speed to increase, resulting in an airframe overspeed.
Safety action
As a result of this occurrence, the operator has advised the ATSB that they have taken the following safety actions:
The details of the event have been shared with all crews to highlight the incident and the need for crews to be autopilot mode aware.
The operator has also conducted further simulator training for the crew involved.
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, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.
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