Air France A321 at Marseille on Mar 10th 2011, &quot;Alpha Floor&quot; activation on approach

Last Update: May 22, 2015 / 19:25:01 GMT/Zulu time

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Photo of Air France F-GTAE, Airbus A321 — Air France F-GTAE, Airbus A321 (Photo credit: col29071962 / Flickr / License: CC by-nd)

Incident Facts

Date of incident
Mar 10, 2011

Classification
Report

Airline
Air France

Flight number
AF-7662

Departure
Paris Charles de Gaulle, France

Destination
Marseille, France

Aircraft Registration
F-GTAE

Aircraft Type
Airbus A321

ICAO Type Designator
A321

An Air France Airbus A321-200, registration F-GTAE performing flight AF-7662 from Paris Charles de Gaulle to Marseille (France) with 180 passengers and 7 crew, was on approach to Marseille's runway 13R, the captain (no data provided) was pilot flying. The crew had briefed the ILS approach to that runway, which was the active runway for landings, but also considered the option to land on runway 13L. The aircraft intercepted the localizer runway 13R at 3500 feet with the autopilot and flight directors engaged, the flaps were set to position 1. The captain decided to disengage autopilot and autothrust, the aircraft subsequentely intercepted the glideslope, the flaps were set to position 2. About a minute later the first officer, pilot monitoring, requested to land on runway 13L but advised the captain that this would put the aircraft above the glide due to less distance to the threshold runway 13L. The aircraft gets cleared to land on runway 13L, during the swing over the gear is lowered, however, the flaps were inadvertently retracted to position 0 instead of being placed into position 3. The aircraft aligned with the extended center line of runway 13L, the speed was 170 KIAS, the vertical speed increases to 2000 fpm of descent, the angle of attack and pitch increases with the thrust levers near idle until the "Alpha Floor" protection activates engaging autothrust at maximum thrust, when the aircraft was 5.7nm before touchdown and already slightly below the glideslope to runway 13L. The aircraft reached a minimum of 1700 feet MSL before starting to climb again, the crew retracts the gear and positions for another approach followed by a safe landing on runway 13R.

The French BEA released their final report in French concluding the probable cause of the incident were:

Wrong selection of flaps and slats, not detected by the flight crew, followed by inadequate pitch commands resulting in decrease of the aircraft's energy state, which was not immediately recognized and led to the activation of "Alpha Floor" Protection.

Inadequate preparation during the arrival briefing contributed to the inadequate management of workload during the simultaneous swing over and aircraft configuration.

The BEA complained that the cockpit voice recorder recordings were not available. Their report therefore was based only on testimony by the crew and flight data recorder.

The BEA annotated that the distance to threshold runway 13L was about 600 meters less than to threshold runway 13R.

The BEA analysed that the disengagement of the autopilot and autothrust increased the workload when the swing over was to be conducted simultaneously with the configuration of the aircraft for landing, when the commander instructed the first officer to extend the landing gear, activate the secondary flight plan for runway 13L. The first officer reported in his recollection he is not sure whether he was instructed to also set flaps to 3 or not. The BEA stated that the rapid succession of instructions may have caused the pilot monitoring to act mechanically without control, the rapid transition from a rather relaxed work load situation to high workload may have caused the inadvertent retraction of flaps rather than the extension to the landing setting.

The pilot flying was looking out of the cockpit windows while positioning the aircraft from the extended centerline runway 13R to the extended centerline of runway 13L. When he checked the instruments again he saw 170 KIAS, which would have been consistent with the flap configuration 2, which he thought was set. However, the speed was indicated below minimum speed, the captain believed this was an erroneous indication and thus did not take action to increase thrust and adjust the pitch. The warning "SPEED! SPEED! SPEED!" warning of the low energy state did not activate because the flaps were in position 0.

The BEA reported the operator took immediate safety actions in order to prevent a recurrence now requiring in their standard operating procedures that upon the instruction to set flaps the pilot monitoring needs to call out "speed check" in order to have both crew focus on the correct speeds, then after verifying at correct speed the first officer would, at the same as moving the flaps lever, announce "FLAPS X" before the flaps reached that position which would reduce the chances of interruption and execution of wrong selections. The operator also points out adequate use of automation to reduce workload even during visual approaches.