What happened
On March 17, 2009, a Diamond HK 36 TC motor glider, registration F-CHQI, was conducting a local instructional flight at Buno-Bonnevaux aerodrome. The flight was part of the student pilot's first training session in this specific aircraft type. After completing several successful circuits and a touch-and-go maneuver, the student was performing a third circuit. During the approach, the engine power was reduced and the propeller was set to full fine pitch.
As the aircraft reached the final approach, the student pilot perceived that the aircraft was above the descent path prescribed by the instructor. In an attempt to correct the trajectory, the student deployed the airbrakes and manipulated the elevator. At an altitude of approximately ten meters, shortly after passing the runway threshold, the aircraft entered a strong pitch-up attitude. The student further extended the airbrakes, prompting the instructor to take control. However, the motor glider subsequently stalled and collided with the unpaved runway approximately thirty meters from the threshold, resulting in damage to the aircraft.
The investigation
The investigation examined the flight profiles, the experience levels of the crew, and the operational procedures of the flying club. It was noted that the instructor had recently completed flight instructor training and was conducting the session under the supervision of a substitute chief pilot. The investigation also looked into the club's internal protocols regarding new instructors and the use of motor gliders for initial training sessions.
Findings
- The primary cause of the accident was inappropriate control inputs by the student pilot during the final approach.
- The instructor provided insufficient supervision during the critical phase of the landing.
- The student pilot's decision to deploy airbrakes while attempting to correct the glide path contributed to the loss of airspeed.
- The aircraft was not equipped with a stall warning device.
- There was a breakdown in club procedures, as the instructor had not conducted a required briefing with the chief pilot prior to the flight, due to the chief pilot's absence on the day of the accident.