What happened
On 20 December 2019, an Air France Airbus A318-100, registration F-GUGD, was performing a commercial passenger flight from Paris-Orly to Hyères-Le Palyvestre. During the approach to runway 05, the crew elected to perform a direct approach rather than a holding pattern, despite experiencing a significant tailwind of approximately 50 knots.
While descending, the aircraft leveled off at 1,900 ft due to a previously selected altitude on the Flight Control Unit. The crew, focused on landing configuration and checklists, did not realize the aircraft had ceased its descent. As the aircraft continued on a path that intercepted the 9° secondary lobe of the ILS glide slope, the autopilot received an inverted signal. This caused the autopilot to command a rapid nose-up movement, increasing the pitch attitude from 1° to 30° in roughly 20 seconds.
The sudden pitch increase led to a significant drop in airspeed, triggering a "Low energy" alert and the "SPEED SPEED SPEED" aural warning. The aircraft's angle of attack exceeded the Alpha Max threshold, activating the ALPHA PROT and ALPHA FLOOR flight envelope protections. The pilot flying responded by applying TOGA thrust and manually reducing the pitch. The crew subsequently executed a go-around, and a second approach was completed without further incident.
The investigation
The BEA examined the flight data recorder, cockpit voice recordings, and crew statements. The investigation focused on the transition from the descent to the level flight at 1,900 ft, the mechanics of the ILS secondary lobe, and the crew's management of the aircraft during the high-workload approach. The investigators also analyzed the aircraft's flight envelope protection logic and the impact of the strong tailwind on the crew's situational awareness.
Findings
- The crew underestimated the threat of the strong tailwind during the approach phase, focusing instead on landing performance and other threats like windshear.
- A loss of situational awareness occurred because the crew did not monitor the glide path closely while performing landing checklists and configuring the aircraft.
- The aircraft intercepted a false glide slope signal within the 9° secondary lobe, which provides inverted guidance.
- The crew did not react to the air traffic controller's suggestion to perform a missed approach.
- The pilot flying's recovery actions, while effective in stopping the pitch increase, involved following flight director commands that initially maintained a high angle of attack, prolonging the low-speed condition.