Forced Landing After Engine Oil Leak and Power Loss (N4976M)

Incident Overview and Pilot Actions The pilot reported that approximately seven minutes after takeoff, the aircraft's engine lost oil pressure and began leaking oil, followed by a loss of engine power. The aircraft entered a descent that the pilot could not arrest, continuing to descend at a rate of about 100 to 200 feet per minute. The pilot then heard a loud bang, felt a shudder in the engine compartment, and experienced a complete loss of engine power. The pilot banked the aircraft toward a clearing and elected to make a forced landing in a field. During the approach, the engine compartment appeared to be on fire, and smoke began entering the cockpit. ## Engine Examination and Findings The engine was examined at the crash site, where a hole was noted in the case at the No. 4 cylinder. Oil was observed on the No. 4 cylinder wall, the oil dipstick did not show any oil, and there was evidence that oil had leaked out of the engine. A subsequent examination on February 12, 1999, revealed that oil had leaked at the engine oil filter adapter. Additionally, more threads were showing on one stud than on the other. A torque wrench was used to check torque on the nuts, and it was noted that one nut rotated 1 1/2 rotations before reaching the specified torque, while the other nut rotated 1 rotation before reaching torque. The oil filter adapter was removed for further examination, and the gasket was found with a gap at the corner with an opening of about 1/16 of an inch.