What happened
On May 20, 2016, a Cessna 172-R, registration F-HATK, was performing a general aviation flight from Carpentras to Aix-les-Milles. The aircraft was carrying a pilot and two passengers. During the final approach to runway 32, the pilot was cleared to land with a reported wind of 330° at 10 knots. While attempting the flare, the aircraft suddenly pitched downward with a high rate of descent. The nose gear struck the runway with significant force, causing the landing gear to break. The aircraft slid 124 meters along the runway before veering off into the grass, where it caught fire during the evacuation.
Two occupants sustained minor injuries, while one passenger was uninjured. The aircraft was destroyed in the accident.
The investigation
Investigators analyzed surveillance footage, which revealed the aircraft was in a nose-down attitude of approximately 20° with an average descent rate of 1,500 ft/min just before impact. The footage also confirmed that the flaps were extended, though their specific setting could not be determined.
Examination of the wreckage confirmed that the flight controls and flaps were functional and intact. However, the investigators found that the pitch trim stabilizer was positioned in an upward direction, which would induce a nose-down reaction.
Regarding maintenance, the investigation revealed that two required maintenance tasks related to the autopilot system were overdue by 498 days. Despite this, the aircraft's airworthiness certificate had been erroneously renewed by the CAMO (Continuing Airworthiness Management Organization). Additionally, the investigation noted that the autopilot had triggered alarms during both the previous day's ferry flight and the accident flight itself, which the pilot had attributed to turbulence.
Findings
- The primary cause of the accident was a nose-down pitch trim movement during the landing phase.
- The investigation could not definitively identify the exact trigger for the trim movement, but ruled out pilot incapacity or intentional action.
- An involuntary engagement of the autopilot during power adjustments on final approach was considered a possibility; if engaged, the system would maintain the existing vertical speed, potentially leading to a trim conflict when the pilot attempted to flare.
- The autopilot system had not been properly tested following recent maintenance, and the aircraft was operating with overdue maintenance requirements.