What happened
Roughly 15 minutes after departing, a multiengine airplane was cruising at 6,000 feet when the right engine suffered a catastrophic failure. Following the engine malfunction, the pilot decided to attempt a return to the departure airport, which was located 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 was unable to sustain the aircraft's altitude. The plane descended into a wooded area and struck the ground approximately 3 miles from the departure airfield. A significant portion of the wreckage was destroyed by fire.
Findings
Post-accident investigations identified a 5.5 by 6-inch 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 while the aircraft was in 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.
Technical measurements revealed that the top cylinder hold-down studs for the No. 2 cylinder extended beyond the manufacturer's specified limits from the case deck. At the time of the accident, the aircraft had flown 50 hours since its last annual inspection, and the right engine had completed 1,425 hours since its overhaul. The No. 2 cylinder had been previously removed and reinstalled 455 hours prior to the event for the replacement of six studs. While the specific reason for the loss of altitude following the engine failure remained unclear, the aircraft possessed the performance capability to reach the closer alternate airport.