What happened
On August 20, 1997, a DG 500 Elan-Trainer glider, registration HB-3134, was performing a training flight at the Montricher airfield in Switzerland. During a winch launch, while the aircraft was at an altitude of approximately 30 meters, the student pilot accidentally released the tow cable.
Immediately following the release, the glider entered a steep right-hand turn with a high bank angle, climbing toward a nearby forested area. Despite the instructor's attempt to take control and fly straight toward a safe landing area, the aircraft entered an unrecoverable state. The glider eventually struck a hangar, causing significant damage to the building, an electric pole, and other aircraft stored inside. The impact was violent enough to eject the student pilot from the cockpit, resulting in his death upon striking a structural beam within the hangar. The instructor sustained serious injuries to his spine and experienced partial amnesia following the crash.
The investigation
Investigators examined the release mechanism and found that the tow hook could only be opened by a deliberate and vigorous pull on the release handle. The investigation concluded that the student likely intended to adjust the rudder pedals but mistakenly grabbed the larger release knob instead.
Technical analysis of the cockpit revealed that the control linkages were damaged; specifically, a broken weld in the control system meant the rear stick lost effectiveness for lateral control. The investigation also determined that the student was no longer secured by his seatbelt at the moment of impact, which led to his ejection from the aircraft.
Findings
- The primary cause was the accidental release of the tow cable by the student pilot at an altitude far below the required safety margin of 80 meters.
- The student's subsequent flight maneuvers, characterized by a steep, climbing right turn, placed the aircraft in an unrecoverable stall.
- The student's physical interference with the controls, likely due to extreme psychological stress, prevented the instructor from stabilizing the aircraft.
- The low altitude at the time of the release left no margin for error or for executing an emergency landing procedure.