Accident Sequence
The pilot conducted a preflight inspection of the turboprop airplane and performed an engine run-up, both of which revealed no anomalies. The subsequent takeoff roll and lift-off from the runway were normal. However, when the pilot initiated a landing gear retraction, the engine torque decreased while the revolutions per minute (rpm) remained unchanged. The torque then surged back to full power and continued to surge as the pilot attempted to return to the runway. During this event, the left wing of the airplane struck the ground, and the airplane came to rest in the grass adjacent to the runway.
Examination
A post-accident examination of the engine, engine accessories, and propeller revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation before the accident. No preexisting conditions were identified that could explain the partial loss of engine power.
Probable Cause
The probable cause of the accident was determined to be a partial loss of engine power for reasons that could not be determined based on the available information.