What happened
On August 14, 2017, at approximately 12:34 UTC, a DG-808B motor glider was conducting a flight near the Pfenning mountain in the municipality of Steyregg, Austria. The pilot had departed from Linz–Ost airport via winch launch and was searching for thermal lift. While maneuvering near the leeward side of the mountain, the aircraft was suddenly struck by a gust or an asymmetrical thermal, causing the aircraft to roll abruptly around its longitudinal axis.
In an attempt to correct this sudden rotation, the pilot applied aileron input. This maneuver triggered a one-sided stall, which subsequently transitioned into a spin. At the time of the spin, the aircraft was at an altitude of only 100 to 150 meters above ground level. Although the pilot successfully executed the recovery procedures to end the spin and regain controlled flight, the altitude loss was too significant to avoid an impact. The aircraft struck trees, which significantly dissipated the kinetic energy of the crash, before finally coming to rest on the forest floor. The pilot sustained one minor injury and was able to exit the wreckage after being freed by emergency responders.
The investigation
The Austrian SUB investigation reconstructed the flight sequence using pilot statements and evidence from the local police. The investigation examined the aircraft's technical condition, the pilot's experience, and the meteorological conditions at the time of the accident. The investigators analyzed the flight manual's specifications for stall and spin recovery, noting that while the pilot performed the correct maneuvers, the low altitude left no margin for error. The investigation also reviewed the aircraft's maintenance records, weight and balance, and the local weather reports (GAFOR) to determine if external factors contributed to the loss of control.