What happened
On August 8, 2013, a SOCATA TBM700N, registration N850GC, crashed near Vertaizon, France, during an instrument approach to Clermont-Ferrand Auvergne Airport. The aircraft, operating a private flight from Toussus-le-Noble, was performing an ILS Z approach to runway 26 under instrument meteorological conditions (IMC).
While the aircraft remained aligned with the localizer, it failed to descend along the glide slope, maintaining a level altitude of 4,000 ft well past the final approach point. The pilot attempted to manually intercept the descent path from above, but the maneuver became unstable. Following an aborted approach, the pilot executed a series of erratic turns and altitude changes. During this period of high workload and low visibility, the aircraft entered a steep dive and struck the ground, resulting in 3 fatalities and the destruction of the aircraft.
The investigation
The BEA investigation focused on the interaction between the aircraft's Garmin 1000 avionics suite and the programmed approach procedure. Investigators discovered a significant discrepancy between the official Jeppesen approach charts and the coding within the Garmin 1000 database. Specifically, the database incorrectly placed the Final Approach Fix (FAF) and the Missed Approach Point (MAP) in a manner that shifted the transition from GPS to localizer navigation.
Because the transition from GPS to conventional radio navigation occurred after the aircraft had already passed the actual glide slope intercept point, the autopilot was unable to capture the descent path. This caused the aircraft to remain in level flight despite the approach mode being engaged. The investigation also examined the pilot's recent flight experience, training history, and the impact of spatial disorientation during the unstable maneuvers.