Full report at:
Investigation: AO-2014-049 - Flight envelope protection event involving an Airbus A320, VH-VQY, near Mildura Airport, Vic on 12 March 2014
On 12 March 2014, at about 0920 Eastern Daylight-savings Time, an Airbus A320 aircraft, registered VH-VQY, departed Melbourne, Victoria on a ferry flight to Darwin, Northern Territory, with a captain and first officer on board.
After about 5 minutes in the cruise at FL 360, the captain temporarily left the cockpit. When abeam Mildura, Victoria, the first officer received a clearance from air traffic control (ATC) to climb to FL 380.
Approaching FL 380, at about FL 373, the first officer observed the airspeed increase and the airspeed trend indicator approaching the maximum operating Mach number (MMO). He attempted to reduce the airspeed by selecting the speed back to M 0.76 however he observed the airspeed and the trend continue to increase. The first officer reduced the thrust to idle, which disconnected the autothrust, in an attempt to reduce the airspeed. He extended the speed brake and disconnected the autopilot to adjust the pitch attitude of the aircraft in an attempt to maintain the selected altitude.
When at about FL 383, the first officer re-engaged the autothrust, and returned the thrust levers to the climb detent. He applied forward pressure on the sidestick to lower the nose attitude of the aircraft in an attempt to recapture FL 380.
The aircraft then descended and the airspeed slowed below the VLS speed. The first officer then applied rearward pressure on the sidestick in an attempt to regain FL 380 and reduced the thrust levers towards idle but short of idle stop position. The application of back pressure increased the aircraft’s angle of attack. At the Alpha Protection speed, the Alpha Floor function activated.
This incident provides a reminder of flight crew of highly automated aircraft, to understand the implication of the intended and actual level of automation applied.