Incident Overview
An aircraft collided with trees short of the runway after the engine ceased operating during final approach. The engine failure was attributed to an internal malfunction of the crankshaft gear retention system.
Teardown Examination
A subsequent teardown of the engine revealed that the crankshaft gear bolt had backed out, and the bolt head had made contact with the oil pump drive tank. Additionally, foreign material was found to have passed through the gear system. This material originated from severely spalled tappets.
Component Damage
The crankshaft gear dowel pin was found sheared. Several camshaft lobes exhibited wear, with corresponding spalling on the tappet faces.
Undetermined Initial Failure
The initial source of the failure mode was not determined during the examination.