What happened
On August 23, 2009, a private Diamond DA 42 Twin Star, registration D-GLBA, was conducting a flight from La Môle to Bremgarten, Germany. During the initial climb at approximately 800 feet, the pilot noticed a decrease in power and propeller RPM on the right engine. Although the pilot attempted to compensate by advancing the throttle to full power, the right engine and propeller eventually stopped at 1,500 feet. The pilot declared an emergency and diverted to Le Luc aerodrome.
During the approach, the pilot observed fluctuations in the power of the left engine. While performing a reconnaissance of the airfield, the left engine lost approximately 90% of its power. The pilot attempted to shorten the landing circuit to utilize runway 09. During the final turn, the pilot experienced what felt like wind shear, leading to a hard landing to the right of the runway. The impact caused the right landing gear to collapse, and the aircraft skidded along the ground for approximately 200 meters before coming to a stop.
The investigation
Investigators examined the aircraft's systems and engine control unit (ECU) data. The inspection of the right engine revealed a failure of a solenoid valve within the propeller regulation system. This failure caused the propeller blades to lock in the high-pitch position, creating significant aerodynamic drag that led to the engine's shutdown.
Regarding the left engine, data from the engine's electronic control unit confirmed the power fluctuations reported by the pilot. Because the system calculates power based on the position of the throttle lever via two independent sensors, the investigators concluded that the recorded power drops were likely caused by involuntary movement of the throttle lever during the emergency procedures.