What happened
On August 26, 2018, a Schleicher ASW17 glider, registration F-CBIP, was performing a local flight at the Villefrube Tarare aerodrome. After being towed and released at approximately 850 meters, the pilot attempted to find thermals near the airfield but was unable to gain altitude.
At approximately 15:00, while performing right-hand spirals at an altitude between 100 and 200 meters, the aircraft entered a spin. The pilot was unable to recover control before the glider struck the ground approximately 350 meters to the right of runway 36. The accident resulted in one fatality and the destruction of the aircraft.
The investigation
Investigators examined the wreckage and found no mechanical malfunctions that could explain the accident. All observed structural failures were consistent with the impact. The aircraft struck the ground in a vertical orientation, with the landing gear retracted and the left airbrake extended.
Data from a GNSS logger and the Open Glider Network allowed investigators to reconstruct the flight path. Additionally, surveillance footage from the aerodrome showed a wind gust occurring at 15:00:20, with wind speeds increasing from less than 5 knots to approximately 20 knots. The footage captured the glider in a steep nose-down attitude and a heavy right bank, performing one and a half turns in a spin before disappearing behind trees.
Witnesses, including the tow plane pilot and an aircraft mechanic, corroborated the sequence of events. The mechanic noted that the glider was flying at a low speed and entered a spin during a right-hand turn.
Findings
- The glider entered a right-hand spin likely due to a decrease in airspeed and lift caused by an increase in tailwind during a wind gust.
- The low altitude of the aircraft prevented the pilot from recovering from the spin and avoiding the ground impact.
- The difficulty for a pilot to perceive or identify a wind gradient without continuous and attentive monitoring of flight instruments may have contributed to the loss of control.