What happened
On May 31, 2003, at approximately 15:15, a Siren PIK 30 glider, registration F-CFPH, crashed in a wooded area near Nistos, France. The pilot, an experienced aviator with approximately 15,000 flight hours, was participating in an interregional soaring competition.
After departing from Saint-Gaudens, the pilot utilized thermals near the Touroc mountain and moved toward the Estiver pass before turning northeast. Witnesses on the ground reported hearing a sharp cracking sound followed by seeing pieces of the left wing falling toward the earth. The aircraft was observed traveling at a high rate of speed before impacting the ground in a steep, inverted attitude. The accident resulted in one fatality and the total destruction of the aircraft.
The investigation
The investigation focused on the structural integrity of the aircraft and the aerodynamic forces acting on the wing at the time of the failure. Investigators examined the wreckage distribution, which confirmed that the left wing had detached in flight. Analysis of the fracture surfaces revealed that the outer portion of the wing separated due to combined upward bending and torsional loads (with decreasing angle of attack).
Investigators also reviewed meteorological data, noting a complex weather pattern involving a confluence of air masses that created localized moderate turbulence. While witnesses reported seeing many birds of prey in the area, no evidence of a bird strike was found on the wreckage. Data from the aircraft's GPS and variometer provided no additional relevant information for the reconstruction of the final moments.
Findings
- The primary cause of the accident was the structural failure of the left wing due to combined bending and torsional stresses.
- The pilot was likely flying at a high descent rate, possibly attempting to navigate between the terrain and the cloud base to reach a turning point or return to the airfield.
- The structural failure may have been triggered by a sudden, aggressive aileron input during a high-load maneuver, such as an avoidance maneuver or a recovery from a stall.
- An alternative contributing factor considered was a violent pitch oscillation caused by the deployment of air brakes during a high-speed descent, which could have placed extreme stress on the wing structure.
- Localized moderate turbulence and the presence of unstable clouds likely added additional structural loads that contributed to the wing separation.