What happened
On March 24, 2019, a LAK-17B FES mini motor glider was involved in a fatal accident during a winch launch at the Hahnweide airfield. The pilot had been performing several flights earlier that day, including a successful training flight with an instructor. During the preparations for the winch launch, witnesses observed the pilot performing the cockpit checklist, specifically announcing the flap setting.
As the launch commenced at 14:5 and the aircraft was being towed, witnesses noted that the glider initially trailed behind the cable. Upon a command for increased speed, the aircraft accelerated and entered the initial climb phase. Shortly thereafter, the glider entered a very steep climb at a low altitude and subsequently pitched to the right. The aircraft struck the ground approximately 200 meters from the launch site, impacting with the right wing and cockpit first. The pilot sustained fatal injuries at the scene, and the aircraft was destroyed.
The investigation
The BFU investigation examined the aircraft, the winch, and the flight procedures. The aircraft, a 2017 model, was operating under a Permit to Fly. The investigation included a review of the weight and center of gravity (C.G.) calculations, which confirmed the aircraft was within permissible limits with a takeoff mass of 339.2 kg. The winch used was a powerful diesel-powered unit capable of a maximum tow mass of 750 kg.
Investigators also reviewed the Flight Manual, which contained specific instructions for winch launches. The investigation found no technical defects in the aircraft's control surfaces or the release mechanisms. Medical examinations of the pilot revealed no evidence of impairment or loss of consciousness prior to the accident.
Findings
- The aircraft experienced a rapid increase in the angle of climb followed by a loss of control.
- The flight manual instructions for winch launches, which required the pilot to push the stick forward during the transition arc, were found to be inaccurate for high-performance winches.
- The winch used was a high-power diesel engine that could provide significant acceleration.
- The aircraft's right winglet was severed upon impact, and the cockpit area was heavily damaged.