What happened
On May 27, 2018, an Aerospool Dynamic WT9 ultralight aircraft departed from the Hahnweide landing field for a private VFR flight. The pilot intended to fly for approximately 30 minutes to accumulate flight time. After an initial climb to 1,100 m AMSL and performing various maneuvers, the aircraft descended to approximately 700 m AMSL. While performing a left-hand turn over a forested area near the Sonnenhof hamlet, the aircraft struck trees on a hillside. The impact, which occurred at an angle of approximately 14.5 degrees, destroyed the aircraft and resulted in the fatal injury of the pilot.
The investigation
The BFU examined radar and GPS data, which showed the aircraft's flight path and altitude. The investigation included a physical examination of the wreckage, the Rotax 914 UL engine, and the aircraft's Turbo Control Unit (TCU). Investigators also reviewed the pilot's medical history, flight logs, and witness statements. The investigation focused on the pilot's physical state following strenuous activity earlier that day and the aircraft's weight and balance, which were found to be within permissible limits. Notably, the aircraft's emergency parachute system had not been activated because the safety pin was still in place.
Findings
Technical examination of the Aerospool Dynamic WT9 revealed no mechanical failures or engine malfunctions. The aircraft's weight and center of gravity were within limits, and the cockpit canopy remained closed during the collision. However, the investigation identified several contributing factors related to the pilot's physiological state. Prior to the flight, the pilot had engaged in physically demanding work assisting with glider retrieval in high summer temperatures. Evidence suggested the pilot had experienced inadequate food and fluid intake throughout the day.
During the final maneuver, a left-hand turn with a bank angle of approximately 40 degrees, the resulting centrifugal forces may have triggered orthostatic circulatory dysregulation, leading to a transient loss of consciousness or impairment. The pilot's lack of active control during the impact, evidenced by the injury patterns and uncompressed rudder pedals, supports the theory of a sudden loss of situational awareness or physical incapacity.