Incident Overview
A multi-engine airplane was cruising at flight level 210 when the pilot declared an emergency due to a rough-running right engine. The pilot diverted to a non-towered airport approximately 10 miles from the airplane’s position. About four minutes later, the pilot reported shutting down the right engine. During the descent, the pilot orbited around the diversion airport and informed an air traffic controller that assistance after landing was not expected to be needed.
Sequence of Events
The airplane initially approached the airport while descending through about 17,000 feet mean sea level (msl) and circled above the airport before entering a left traffic pattern for runway 22. At approximately 7,000 feet msl, the airplane was about 2.5 miles northeast of the airport. It descended through 2,300 feet msl when abeam the runway threshold on the downwind leg. According to the airplane information manual, procedures for landing with an inoperative engine call for “excessive altitude.” However, the last radar return showed the airplane at 700 feet msl (about 600 feet above ground level) and about three miles from the approach end of the runway. The airplane was configured for a single-engine landing and was likely on or turning to final approach when it rolled and impacted trees. The airplane came to rest inverted in a wooded area about 0.8 miles north of the runway threshold, in a flat attitude with no longitudinal deformation.
Post-Accident Examination
A postcrash fire consumed a majority of the airplane, including the cockpit, main cabin, and left wing. Search operations located the airplane approximately six hours after its expected arrival time. Due to the severity of the fire, occupant survivability after impact could not be determined. Examination of the airframe, left engine, and both propellers revealed no preaccident mechanical malfunctions or failures that would have precluded normal operation. The investigation determined that the right engine failed when the camshaft stopped rotating after a fatigue fracture of one tooth on the camshaft gear. The remaining gear teeth were fractured in overstress and/or crushed due to interference contact with the crankshaft gear. Spalling observed on an intact gear tooth suggested abnormal loading of the camshaft gear, though the origin of the abnormal loading could not be determined.
Probable Cause
The official probable cause findings state: The pilot's failure to maintain airplane control during a single-engine approach and his failure to fly an appropriate traffic pattern for a single-engine landing. Contributing to the accident was a total loss of engine power on the right engine due to a fatigue failure of the right engine cam gear.