Cessna P210N N4839P accident near Elizabeth, Colorado

Probable cause

the loss of engine power due to the fatigue failure of the camshaft gear. Contributing to the accident was the lack of suitable terrain for the forced landing.

NTSB analysis

During a normal descent on approach for landing at 8,500 feet mean sea level, the engine "let go/popped into a higher pitch sound, and the power dropped off. [The pilot] checked the fuel flow, tried to get power with the throttle, but no response." During a forced landing, the airplane impacted the side of a gravel road, traveled across the road, struck a ditch, and skidded on the fuselage bottom for approximately 75 feet were it came to rest upright in a residential yard. Examination of the engine exhibited fretting on all six cylinder decks and the main bearing case half sections. The number 2 main bearing support bearing tang lock-slot was found elongated. Various degrees of wear were noted on all crankshaft main bearings, and the number 2 main bearing showed additional wear. The crankshaft number 2 main journal exhibited signatures of thermal discoloration. All oil transfer galleries were free and clear of debris. The camshaft was intact, however, the camshaft gear had a semi-circular section with 7 gear teeth separated, which was found in the gearbox. Metallurgical examination showed the fracture initiated at the surface and progressed in fatigue. The initiation site was damaged; however, the approximate location was identified by crack arrest lines, which encircled the origin. The reason for the fracture initiation could not be determined.

Text from the NTSB. Open the NTSB docket for DEN08LA069 for the full record.