What happened
Approximately 15 minutes following takeoff, a multiengine airplane was cruising at an altitude of 6,000 feet when the right engine suffered a catastrophic failure. Following this loss of power, the pilot chose to attempt a return to the departure airport, located roughly 30 miles away, rather than diverting to a closer suitable airfield situated only 10 miles from the aircraft's position. During this maneuver, the pilot reported an inability to maintain the necessary altitude. The aircraft subsequently descended into a wooded area and struck the ground approximately 3 miles from the departure airport. A significant portion of the wreckage was destroyed by fire.
Findings
Post-accident investigations identified a large hole in the upper right section of the engine crankcase. Detailed examination of the right engine determined that the No. 2 cylinder had detached from the crankcase during flight. Investigators discovered fatigue fractures on two of the No. 2 cylinder studs, which were attributed to insufficient preload on the bolts. Furthermore, a fatigue fracture was noted on the right side of the crankcase itself.
Technical measurements revealed that the top hold-down studs for the No. 2 cylinder exceeded the manufacturer's specified length from the case deck by .085 and .111 inches. At the time of the accident, the aircraft had flown 50 hours since its last annual inspection, which had occurred eight months prior. The right engine had accumulated 1,425 hours since its overhaul and 455 hours since the No. 2 cylinder had been reinstalled following a stud replacement. The pilot's decision to return to the departure airport instead of diverting to a nearer airport was a critical factor in the accident.