What happened
On June 23, 2018, at approximately 13:45 UTC, a Pilatus B4-PC11 AF glider was undergoing a winch launch at the Mauterndorf aerodrome (LOSM) in Salzburg, Austria. The aircraft, which had been stored in a club hangar and was being prepared for its first flight of the season, was being launched via a winch system.
During the takeoff roll, the glider entered an unusually steep climb. At an altitude of approximately 30 meters above the ground, the aircraft experienced an aerodynamic stall due to an excessive angle of attack and insufficient climb speed. The pilot attempted to release the winch cable immediately upon recognizing the dangerous flight attitude. However, the glider entered a left-wing drop and a 18/0-degree roll around its longitudinal axis, resulting in a vertical impact with the ground at high speed. The pilot sustained fatal injuries, and the aircraft was destroyed.
The investigation
The SUB investigation examined the aircraft's configuration, the flight conditions, and the mechanical components involved in the launch. Investigators reviewed the pilot's experience, noting that while the pilot had significant total flight time, this was only his third winch launch of the year and his second on this specific aircraft type.
Physical evidence from the wreckage was analyzed, specifically focusing on the elevator trim settings and the winch cable's breaking strength. The investigation also reviewed the weather conditions, which involved north-westerly winds of approximately 40 km/h, and the procedures followed by the ground crew and the pilot during the launch sequence.