Accident Overview
A Piper PA-24 aircraft experienced a total loss of engine power during the climbout phase of flight. The pilot executed a forced landing, during which the aircraft impacted the terrain.
Investigation Findings
Examination of the engine revealed that the accessory drive gear was loose on the end of the crankshaft. As a result, the gear was not driving the accessory section, leading to the engine failure.
The aircraft had previously sustained a propeller strike. Repairs performed after that event did not comply with the instructions in the Textron Lycoming Service Bulletin. The bulletin required the installation of a new-style drive gear and gear retaining bolt. However, old-style parts were used instead.
According to Lycoming, the new-style parts are necessary to ensure that the gear seats properly on the crankshaft mounting face and remains secure during engine operation. The failure to follow the bulletin allowed the gear to work loose over time.
Probable Cause
The probable cause of the accident was the improper repair following a propeller strike, wherein old-style accessory drive gear and retaining bolt were installed instead of the new-style parts specified in the Textron Lycoming Service Bulletin. This led to the gear loosening and subsequent total engine failure.