SYNOPSIS
The aircraft took-off from Ireland West Airport Knock (EIKN) with two persons on board. Shortly afterwards the Pilot reported engine problems to Air Traffic Control (ATC) and attempted to return to EIKN. Following power loss the engine subsequently failed. A forced landing was attempted in difficult terrain and resulted in the aircraft impacting the ground in a steep nose down attitude. The Pilot was fatally injured and the passenger was seriously injured.
The engine failure was caused by a fatigue fracture of cylinder No. 2 inlet[1] valve head, a segment of which transferred to and contaminated cylinder No. 4. This, combined with a resulting disturbed inlet manifold airflow, caused the engine to fail. Metallurgical testing determined that the initiating cause of the fatigue fracture in the No. 2 inlet valve head was overheating, but the cause of this could not be not conclusively determined.
[1] Inlet valve: Also known as an intake valve.
