What happened
During the initial climb phase, the aircraft was approximately 800 feet above the ground when the left engine suffered a sudden loss of power. The pilot lost control of the aircraft's direction, causing it to swerve violently off the left side of the runway. The plane collided with a drainage ditch located adjacent to the airfield and came to rest in an inverted position.
The investigation
A thorough mechanical examination was conducted on the damaged components to determine the root cause of the failure. Inspecting the fuel control unit revealed that the bellows within the assembly were in an extended position, which indicated a leak into the evacuated area. A specific failure was noted at the seam of these bellows.
Further inspection of the propeller system showed that the start locks were fully engaged at the moment of impact. The blades were held firmly in the start lock position. This mechanical state occurs when the power lever is moved to reverse during shutdown with engine RPM below 50 percent. To disengage, the pilot must retard the levers to reverse after starting; however, the locks will not disengage once the power lever is set to the flight range.
Findings
The primary contributing factor was the improper disengagement of the propeller start locks. The mechanical design prevents disengagement once the power lever enters the flight range, meaning the pilot failed to perform the necessary shutdown procedure correctly before the next takeoff attempt.