What happened
During a local training mission, an aircraft departed from Zurich-Kloten at 08:57 local time. The flight was carrying a total of nine people, including one instructor, five student pilots, two engineers, and one technician. While performing various circuits at altitudes ranging from 1,000 to 3,000 meters, the aircraft experienced a loss of control while flying over Constance Lake.
The plane entered a spin and impacted the water approximately 4 km from Romanshorn. Following the crash, the wreckage descended to a depth of 200 meters. Very little debris was recovered from the surface of the lake or from the shoreline located between Arbon and Romanshorn. The accident resulted in nine fatalities.
Findings
An examination of the wreckage provided no indications of mechanical failure or technical malfunction prior to the crash. At the moment of impact with the water, the aircraft's landing gear was fully extended, while the flaps remained retracted. Data from the engine indicators showed a discrepancy in RPM between the two engines, with the left engine at 1,550 RPM and the right engine at 1,350 RPM; additionally, the right propeller had not been feathered.
The investigation concluded that the accident was caused by the aircraft stalling due to a loss of airspeed, which subsequently triggered an unintentional spin. Because the flight was at an insufficient altitude, the crew was unable to recover the aircraft and level it off before hitting the lake.