On 24 September 1994, lack of understanding of automatic flight control modes, by the crew of an Airbus A-310, led to a full stall. The aircraft was recovered and landed safely at Paris Orly.
The following is extracted from the official report into the incident published by the Bureau d'Enquêtes et d'Analyses (BEA):
During the approach to Paris Orly, in day Visual Meteorological Conditions (VMC), mismanagement of the aircraft automatics by the flight crew led in a few seconds, to the pitch attitude reaching 60° at which point the aircraft banked sharply to the left and the right and stalled before adopting a strongly negative pitch attitude (MS 33 degrees) towards the ground.The maximum altitude reached was 4,100 feet, while a minimum indicated speed of 35 kts was recorded. The stall and ground proximity warnings sounded during the descent. The flight crew managed to regain control of the aircraft, with the lowest point being around a height of 800 feet from the ground. The crew managed to recover control of the aircraft and completed a circuit before a further sucessful approach to land. There was no damage to the aircraft and there were no injuries to the occupants.
- "…The Captain, at the controls, started an automatic approach.
- Approach control asked the aircraft to shorten its path, which led to ILS interception closer to the runway than provided for by standard procedure.
- According to the systems logic, the glide, encountered before the localizer, was not automatically captured . The Captain then disconnected both automatic pilots, leaving the auto-throttle in operation.
- An altitude of 4,000 feet was selected before establishment of the aircraft on ILS as go around altitude. The go around altitude in the procedures is 2,000 feet.
- When flaps were selected at 20 degrees, the speed was slightly greater than VMAX,which activated speed protection, leading to reversion of VS mode to LVL CHG mode.
- Due to the altitude selected being greater than that of the aircraft, the auto-throttle commanded an increase in thrust. The pilot maintained the aircraft on descent.
- He accidentally caused the trim to its electrical stop at thirteen degrees nose up, which put the aircraft in a totally out of trim situation.
- To counter the effect of THS deflection, he moved the elevator control to its mechanical stop of fifteen degrees nose down, by effort applied on the control column.
- A sudden increase in thrust was commanded manually.
- Under the effect of the additional force, the aircraft pulled up rapidly. The pilot continued to counter by continuous effort on pitch and by temporarily holding the thrust levers in the idle position. He neither corrected trim, which remained on pullup stop nor disconnected the auto-throttle.
- The aircraft took a path with a very steep slope, with roll angle reaching extremely high values. It climbed to an altitude of 4,100 feet and minimum speed recorded was 35 kt. Alpha-trim protection reduced the THS deflection by four degrees.
- Under the effect of strong drift on full and rapid rolls, the angle of attack sensors were disturbed, which led to automatic disconnection of the two pitch-trims. The auto-throttle was inhibited for the same reasons.
- Due to the dynamic of the aircraft’s movements, the stall warning and the stick shaker did not function in a preventive manner.
- The flight crew regained control of the aircraft after the stall."
"The direct causes of the unusual attitudes and the stall to which the aircraft was subjected were a movement of the THS towards the full pitch-up position and a rapid increase in thrust, both of which maneuvers were the due to the Captain, following an AFS mode reversion which was not understood. The pitch-up force caused a sudden change in attitude that the flight crew was unable to contain with the elevators.
The following elements contributed to the incident:
- Too rapid an approach, due to a late start in the descent, followed by a reduction of the standard procedure.
- Inadequate crew resource management.
- Premature selection of the go around altitude and precipitous setting of the configuration with slats and flaps at 20-20, which led to activation of the speed protection.
- Difficulty in understanding the action of the auto-throttle increasing thrust in its overspeed protection function.
For further information see the full Report published by the Bureau d'Enquêtes et d'Analyses (BEA).