What happened
On July 3, 2015, at approximately 17:29 UTC, a Pilatus glider, registration B4-PC11 AF, was performing an aerobatic display training session at Seitenstetten Airfield, Austria. The pilot was practicing maneuvers intended for an airshow scheduled for the following day.
After being towed to an altitude of 1,000 meters, the pilot executed a series of maneuvers. The sequence concluded with a knife-edge flight (inverted) from west to east, maintaining an altitude of approximately 5 meters above runway 10. During the transition from this maneuver, the pilot initiated a 30-degree climb followed by a left roll into upright flight and a simultaneous left turn. During this maneuver, the leading edge of the left wing made contact with the ground. The aircraft subsequently impacted the ground approximately 40 meters from a hangar, resulting in the total destruction of the aircraft.
The investigation
The investigation conducted by the SUB examined the aircraft's maintenance history, the pilot's qualifications, and the environmental conditions at the time of the accident. The wreckage was analyzed, revealing that the control surfaces were intact and the aircraft had been maintained in excellent condition. The damage to the fuselage and wings was determined to be the result of the impact forces rather than pre-existing structural failures. The investigation also reviewed the pilot's experience, noting that the pilot held valid aerobatic ratings and had sufficient experience with this aircraft type.
Findings
- The primary cause of the accident was an insufficiently low altitude during the maneuver.
- High ambient temperatures (30°C) contributed to the accident by reducing air density.
- The aircraft was in a well-maintained, airworthy condition with no pre-existing technical defects.
- The pilot's weight and balance were within permissible limits.