Cirrus Design Corp SR22 N8135B accident near Cross City, Florida

Probable cause

A total loss of engine power resulting from the failure of the camshaft due to fatigue cracks. Contributing to the accident was the inadequate quality inspection of the camshaft after initial manufacture.

NTSB analysis

The airplane’s engine lost power during cruise flight at 9,000 feet, and the pilot declared an emergency. Air traffic control (ATC) personnel initially provided the pilot with headings to a nearby airport. However, when the pilot realized that he would not reach the intended airport, he deployed the airplane’s parachute, and the airplane came to rest upright in a field.

Postaccident examination of the engine revealed that the camshaft was completely fractured due to fatigue cracks near the flange at the oiling holes. Further examination showed that the fatigue cracks initiated at the edge of the oiling holes and were caused by burrs left when the camshaft was originally manufactured. The burrs folded over during subsequent shot-peening operations, which formed laps at the corners of the holes; the laps acted to concentrate stresses at the edges of the holes and also shielded the underlying material during shot peening. The laps prevented formation of the beneficial compressive stresses that result from shot peening. This allowed subsequent formation of fatigue cracks.

The accident camshaft was determined to have been the 19th camshaft of its type manufactured. Because the camshaft was not a serialized part, specific manufacturing records could not be located. However, the quality control inspection procedures that were in place at the time the camshaft was manufactured required an inspection of the oil holes for proper de-burring. A search of FAA database revealed no similar camshaft fracture failure between 1995, and February 2012, excluding the accident event.

Text from the NTSB. Open the NTSB docket for ERA11LA130 for the full record.