What happened
On July 4, 2009, a Schempp-Hirth Duo Discus T motor glider, registered F-CIDO, took off from Barcelonnette aerodrome as part of a friendly soaring competition. The flight was conducted with two occupants: the pilot in the rear seat and a second pilot in the front seat. The aircraft was released from a tow on the southern slope of the Chalanche mountain.
During the flight, the aircraft performed a spiral maneuver at a low altitude over a mountain ridge. While navigating this area, the glider encountered downdrafts. In an attempt to avoid the rising terrain, the pilot executed a sharp right-hand turn. This maneuver, combined with the high bank angle and the aircraft's high mass, led to a loss of control. The glider struck the terrain near the Bernarde ridge, resulting in two fatalities and the destruction of the aircraft.
The investigation
The investigation focused on the flight trajectory, meteorological conditions, and the decision-making process of the crew. Investigators analyzed GPS and flight data from onboard recorders, which allowed them to reconstruct the flight path. They also reviewed witness accounts from hikers and the tow pilot.
Technical examinations of the wreckage showed no mechanical failures; the engine, flaps, and airbrakes were all in the retracted position at the time of impact. The investigation also looked into the meteorological conditions, noting that while the pilots had been briefed on potential downdrafts, the specific conditions at the time of the accident involved significant turbulence and sinking air on the lee side of the mountains.
Findings
- The aircraft was operating near its maximum allowable weight, though the center of gravity was within limits.
- The pilots were highly experienced, but were likely subject to the pressures of the ongoing competition and accumulated fatigue from previous days of flying.
- The crew chose to be towed to the northern sector of the aerodrome despite a suggestion from the tow pilot to use the southern sector, where conditions were believed to be more favorable.
- The primary cause was the decision to perform a spiral maneuver at an insufficient altitude over the ridge while encountering downdrafts, which led to an unrecoverable loss of control during an evasive turn.