What happened
On July 18, 2015, at approximately 12:23 local time, a Glasflügel Club Libelle H 205 glider was performing a winch launch from runway 29 at the Flensburg-Schäferhaus airfield. During the ascent, at an altitude of roughly 15 to 30 meters above the ground, the towline became detached from the aircraft. Witnesses observed the glider drifting to the right before it stalled and pitched over the left wing. The aircraft struck the ground approximately 120 meters from the takeoff point, resulting in heavy damage to the airframe and serious injuries to the pilot.
The investigation
The BFU investigation focused on the mechanical state of the aircraft, the winch, and the towline. The investigation established that the towline and all required safety equipment, including the blue weak link, were intact and complete. The aircraft, a single-seat composite glider, showed significant structural damage, including multiple breaks and delamination in the cockpit area and a crack in the leading edge of the horizontal stabilizer. The flight controls remained functional, and no evidence of control impairment was found.
Regarding the winch, the investigation examined the custom-built unit, which was operated by a trainee and an instructor. Both winch operators reported that the engine had suddenly stopped at the time of the accident. Subsequent testing of the winch, conducted in the presence of police, demonstrated that the engine was functional, and the winch was capable of retrieving cables under full load without malfunction. The engine's automatic safety shutdown features, which trigger during low oil pressure or high coolant temperature, were also reviewed.
Findings
- The primary cause of the accident was the premature release of the towline from the glider during the initial phase of the winch launch.
- The sudden stoppage of the winch engine occurred simultaneously with the detachment of the cable.