What happened
On August 21, 1998, a Piper PA-28RT-201T Turbo-Arrow IV, registration D-EDEV, departed from Eggenfelden, Germany, bound for Annemasse, France. The flight, operated for private purposes with the pilot and one passenger, initially proceeded under visual flight rules (VFR). As the aircraft moved through Swiss airspace, the pilot encountered increasing cloud cover and requested higher altitudes to avoid instrument meteorological conditions (IMC), for which he was not rated.
While climbing toward FL190 to escape potential icing conditions, the aircraft's flight path deviated sharply from instructions. Instead of following a suggested southern route, the aircraft entered a high-speed right turn. Radar data and eyewitness accounts indicate the aircraft entered a steep dive at speeds exceeding structural limits. During this descent, the aircraft began to disintegrate in mid-air; the wings and parts of the tail assembly separated from the fuselage. The wreckage impacted a slope below Lischboden in the Gurnigel area at approximately 12:05 local time. Both occupants sustained fatal injuries.
The investigation
Investigators from the Swiss Transportation Safety Investigation Board (SUST) examined the wreckage and reconstructed the flight path using radar data, radio communications, and witness statements. Technical analysis of the wreckage, conducted alongside specialists from EMPA, revealed that the elevator stops were heavily compressed and the horizontal stabilizer had been torn from the tail. The investigation also focused on the physiological state of the occupants and the availability of life-support equipment.
Findings
- The aircraft was not equipped with an oxygen system at the time of the accident, as the necessary unit had been left in the hangar.
- Medical examinations of the victims revealed histological evidence of hypoxia, specifically fat-free bubbles around heart muscle cells, indicating hypoxia occurred 10 to 30 minutes prior to death.
- The aircraft's structural failure was caused by aerodynamic flutter of the horizontal stabilizer due to excessive airspeed, which subsequently led to the failure of the wing spars during negative G-loading.
- The pilot's ability to maintain control was compromised by a lack of oxygen at high altitude.
Safety action
No specific safety recommendations were recorded in this report, though the investigation established that the pilot's decision to climb into higher altitudes without an oxygen supply and without IFR capabilities was a critical factor in the loss of control.