What happened
On March 10, 2011, an Air France Airbus A321-200, registration F-GTAE, was performing a scheduled passenger flight from Paris Charles de Gaulle to Marseille Provence. During the approach to runway 13R, the crew decided to execute a wide turn, known as a bayonet maneuver, to align with runway 13L due to the different threshold positions of the two runways.
During this maneuver, the crew transitioned to manual flight by disconnecting the autopilot and auto-thrust. While configuring the aircraft, the co-pilot inadvertently moved the flap lever to the '0' position instead of the intended '3' position. This error, combined with the aircraft's configuration, led to a rapid decrease in airspeed. The pilot flying, focusing on visual cues outside the cockpit, noticed a speed of approximately 170 knots but incorrectly assumed an instrument failure rather than a configuration error. In an attempt to reduce the descent rate, the pilot applied significant back-pressure on the side stick. This caused the angle of attack to rise sharply, eventually triggering the 'ALPHA FLOOR' protection, which automatically engaged maximum thrust.
The investigation
The BEA investigation focused on the crew's workload and the management of aircraft configuration during the transition between runways. The investigators examined the flight data recorder (FDR) and crew testimonies to reconstruct the sequence of events, as CVR data was unavailable. The investigation scrutinized the lack of a detailed briefing regarding the bayonet maneuver and the crew's failure to monitor the flap position during a period of high task saturation.
Findings
- The primary cause of the incident was the erroneable selection of the flap lever position, which went undetected by the crew.
- The crew's workload increased significantly following the disconnection of the autopilot and auto-thrust.
- A lack of a detailed briefing for the bayonet maneuver resulted in a lack of shared situational awareness between the pilot flying and the pilot monitoring.
- The pilot flying's reliance on external visual references led to a failure to recognize the decaying energy state of the aircraft.
- The 'SPEED' low-energy alarm did not activate because the aircraft was in a zero-flap configuration.
Safety action
Following the incident, the operator implemented new procedures to improve flap configuration monitoring. The pilot monitoring is now required to perform a 'speed check' and immediately verify the target flap setting on the ECAM after any movement of the lever. Additionally, emphasis has been placed on the appropriate use of automation during high-workload phases to maintain energy management.