What happened
On 6 August 2014, a Socata TBM700, registered N129AG, departed Cannes-Mandelieu aerodrome for Courtrai, Belgium, under an IFR flight plan. The aircraft was carrying the pilot and four passengers. While cruising at FL240 within a thick cloud layer, the aircraft suddenly entered a right-hand turn and began a rapid descent to FL149. During this phase, the aircraft's speed increased significantly, triggering the VMO overspeed warning.
Approximately 45 seconds into the descent, the aircraft began a steep climb, reaching FL201 with a vertical rate exceeding 10,000 ft/min. During this climb, the pilot transmitted a radio message to ATC stating, "We have a problem." As the aircraft reached FL201, the airspeed dropped until the aircraft stalled while still in instrument meteorological conditions (IMC). The aircraft then entered a spin that eventually flattened out. As the aircraft emerged from the clouds at an altitude between 1,000 and 2,000 feet, it was in a flat spin. The pilot was unable to execute the necessary recovery maneuvers before the aircraft struck the ground in a nearly vertical path. The accident resulted in two fatalities (the pilot and one passenger) and three injuries to the remaining passengers.
The investigation
The BEA examined the wreckage, radar data, and flight simulator tests to reconstruct the flight path. Because the Socata TBM700 was not equipped with flight recorders, investigators could not definitively establish the exact cause of the initial descent. Simulator tests were used to replicate the radar-recorded trajectory, confirming that the sudden descent and subsequent high-rate climb were possible through specific pilot inputs. Investigators also examined the cockpit configuration, noting that the passenger in the front right seat was found in a slumped position, which could have potentially interfered with the control column or autopilot disconnection button.