Motor glider loss of control during mountain flight leads to terrain collision

Casualties unknown • Conséquences et dommages, FR

A motor glider crashed into a ridge in the Hautes-Alpes region of France after entering an asymmetric stall during a turn.

What happened

On August 13, 2011, a TST 10 ATLAS M motor glider, registration OK-A630, departed from Aspres-sur-Buech for a solo flight. Around 15:00, the pilot reported his position via radio at an altitude of 3,200 meters near Pic de Bure and proceeded east toward Mont Dauphin.

Shortly thereafter, a witness near Saint-Firmin observed the aircraft flying along the southeast face of the Chamousset ridge. The aircraft crossed the ridge, completed a full left turn, and then initiated a right turn. During the final stage of this turn, the aircraft banked sharply to the right while facing the terrain, entering a rapid rotation. The aircraft disappeared behind the ridge and collided with the terrain at an altitude of approximately 1,790 meters. The impact resulted in one fatality and the destruction of the aircraft.

The investigation

The flight sequence was reconstructed using witness testimony and data from the onboard FLARM flight computer. An examination of the wreckage revealed no mechanical anomalies, though the engine was not delivering power at the moment of impact.

Flight data indicated that the aircraft was losing altitude during the final turn, with the last recorded point showing a height of only about 80 meters. Meteorological conditions at the site were characterized by a 220° wind at 8 knots, scattered clouds at 2,100 meters, and a QNH of 1010 hPa. The accident occurred on the leeward side of the ridge.

The pilot, aged 45, held Czech-issued PPL(A) and glider licenses and had accumulated 1,280 total flight hours. He was described as an experienced pilot with significant local knowledge. Regarding the aircraft, the TST 10 ATLAS M is a Czech-designed motor glider. While not classified as a microlight under French regulations due to its mass and wing area, it was classified as such in the Czech Republic and lacked a certificate of airworthiness or DGAC authorization on the day of the accident.

Findings

  • The accident was likely caused by a lack of pilot vigilance.
  • The pilot misjudged his flight path, placing the aircraft at a low altitude on the leeward side of the ridge.
  • In an attempt to clear the terrain, the pilot likely increased the bank angle.
  • Due to insufficient airspeed, the aircraft entered an asymmetric stall at an altitude too low to allow for recovery.

Probable cause

The pilot's failure to maintain adequate situational awareness led to a miscalculated trajectory near the ridge. This resulted in an aggressive maneuver on the leeward side of the terrain, triggering an asymmetric stall from which recovery was impossible.

Frequently asked questions

What happened in the 2011-08-13 TST 10 ATLAS M accident near Conséquences et dommages, FR?

A motor glider crashed into a ridge in the Hautes-Alpes region of France after entering an asymmetric stall during a turn.

What aircraft was involved and where did it happen?

The accident on 2011-08-13 involved a TST 10 ATLAS M, at Conséquences et dommages, FR.

What was the probable cause of the accident?

The pilot's failure to maintain adequate situational awareness led to a miscalculated trajectory near the ridge. This resulted in an aggressive maneuver on the leeward side of the terrain, triggering an asymmetric stall from which recovery was impossible.

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