Cirrus Design Corp SR22 N813JE incident near Burlington, Massachusetts

Probable cause

A loss of clamping load of the No. 5 cylinder crankcase through bolts due to maintenance personnel’s failure to properly torque the through bolts during recent maintenance, which resulted in displacement of the No. 2 bearing and the subsequent catastrophic engine failure.

NTSB analysis

The flight instructor reported that he and the pilot receiving instruction had completed a local instructional flight and were returning to the departure airport. While the airplane was about 1,700 ft mean sea level, the engine began running roughly and subsequently lost all power. The pilot receiving instruction immediately handed over the flight controls to the flight instructor. The flight instructor attempted to maneuver the airplane to a field for a forced landing but realized that the airplane would not be able to reach the field, so the pilots activated the ballistic parachute system. After the parachute deployed, the airplane touched down in an area of dense vegetation.

Postincident examination of the engine revealed that the crankshaft had fractured at the No. 2 main journal and that the camshaft had fractured between the Nos. 2 and 3 main bearing supports. The No. 2 main bearing had shifted, and fretting was present on the main bearing supports, consistent with a loss of clamping load on the crankcase, which resulted in movement of the No. 2 bearing and excessive loading on, and the ultimate failure of, the crankshaft. The nuts securing the No. 5 cylinder to its two crankcase through bolts had less torque than that specified by the engine manufacturer's installation guidance, and it is possible that the loss of clamping load on the crankcase was due to a loss of torque to the adjacent No. 5 cylinder crankcase through bolts. According to maintenance records, the No. 5 cylinder had been removed and replaced about 4 months, or 27 flight hours, before the accident. Although the logbook entry indicated that the through bolts were torqued "from each side to [the engine manufacturer's] specifications," it is likely that, while replacing the No. 5 cylinder, maintenance personnel did not properly torque the cylinder crankcase through bolts, which resulted in displacement of the No. 2 bearing and the catastrophic failure of the engine.

Text from the NTSB. Open the NTSB docket for ERA14IA301 for the full record.