What happened
On May 17, 2007, a Socata Gardan GY 80-180, registration F-BNQV, departed Lyon Brindas for Villefranche Tarrare with a passenger on board. The initial flight was completed in approximately twelve minutes under marginal visual flight rules (VFR) conditions. After a 30-minute stop, the pilot departed Villefrually Tarrare alone to return to Lyon.
During this return leg, the aircraft encountered significantly deteriorating weather. Witnesses at the departure airfield noted that visibility had degraded, and an AFIS agent reported that no other aircraft movements had occurred during the aircraft's stop due to unfavorable VFR conditions. While flying near the Mont Mercruy ridge, the aircraft struck the treetops on the southern slope of the mountain at a high horizontal speed with a 60-degree bank angle. The aircraft then impacted the ground almost vertically with high energy. The wreckage was found nearly entirely consumed by fire.
The investigation
The investigation focused on the flight path, the aircraft's technical state, and the meteorological conditions at the time of the accident. Investigators examined the wreckage, which was located approximately 10 meters below the summit of Mont Mercruy. Technical analysis of the engine and the airframe revealed no mechanical malfunctions prior to the impact. A Garmin 496 GPS, which featured a ground proximity warning function, was recovered from the wreckage.
Meteorological data from Météo France confirmed a cold front was moving through the area, bringing rain, high humidity, and low ceilings. At the accident site, the cloud ceiling was estimated to be as low as 10 meters above the ground. Radar tracking from Lyon Mont Verdun confirmed the aircraft's flight path was relatively straight during the final minutes of the flight before it approached the terrain.
Findings
- The primary cause of the accident was the decision to operate the aircraft in meteorological conditions incompatible with VFR flight.
- The pilot's familiarity with the local geography and a high level of confidence in the GPS technology contributed to the decision to continue the flight.
- The pilot's desire to return to the original departure airfield despite the worsening weather was a contributing factor.
- The pilot failed to recognize the point at which a turnaround was no longer possible due to the encroaching cloud base.