What happened
On September 27, 2010, a Rolladen Schneider LS8 glider, registration F-CGZL, departed from Saint Auban aerodrome for a local flight. After being towed and released at an altitude of 1,460 meters near the Ruth summit, the pilot began performing maneuvers to exploit potential rising air.
Data recovered from a flight computer indicates that the pilot executed two full left-hand spirals over the southern crest of the ridge. During the second spiral, the aircraft began to lose altitude. As the glider moved east of the ridge, it encountered a descending air current (lee wave) caused by the prevailing northwest wind. The pilot likely realized too late that the decreasing altitude would prevent the aircraft from clearing the terrain. During the final moments, the aircraft entered an uncontrolled right-hand spiral, impacting the wooded slope at approximately 1,230 meters. The impact resulted in one fatality.
The investigation
The investigation focused on the flight path, the meteorological conditions, and the lack of timely alert. Investigators analyzed GPS and barometric data from a Zander GP940 computer, which allowed them to reconstruct the spiral maneuvers and the subsequent loss of altitude.
The investigation also examined why the accident was not detected sooner. On the day of the accident, the flight monitoring duties were being handled by student instructors who were preoccupied with welcoming new trainees. Because the pilot was a regular member of the flying center, her absence from the morning briefing was not viewed as suspicious. Furthermore, the usual 'starter' responsible for monitoring radio communications was absent, and the aircraft was not equipped with an active emergency locator transmitter (ELT), as such devices had been temporarily removed from the center's fleet due to frequency compatibility issues. This led to the wreckage being discovered only the following morning.
Findings
- The pilot was performing spiral maneuvers at an altitude too low to safely clear the ridge.
- The aircraft encountered a descending air current on the lee side of the terrain.
- The pilot likely entered an uncontrolled spiral or a stall while attempting to maneuver away from the rising terrain.
- Favorable meteorological conditions may have led to a reduction in the pilot's vigilance regarding potential threats.