Cirrus Design Corp SR22 N509SR incident near Northport, Florida

Probable cause

Inadequate torque on one of the No. 6 connecting rod bolt retaining nuts, which resulted in the connecting rod’s separation from the crankshaft and a subsequent total loss of engine power.

NTSB analysis

About 10 minutes after takeoff, when the airplane was in level cruise flight, the engine lost power. The pilot performed a forced landing to a road, which resulted in minor damage to the airplane when the right wing impacted a road sign. An initial examination of the engine revealed a hole in the upper deck in the vicinity of the Nos. 5 and 6 pistons. Further examination revealed that both of the No. 6 connecting rod bolts were fractured. One bolt was missing the self-locking nut, and fretting adjacent to the bolt hole on the split-line face of the connecting rod indicates that the bolt was probably not tightened with sufficient torque and backed off the bolt. The bolt then likely backed out of its hole on the connecting rod, enabling the cap to hinge open, and the loading of the other bolt in tension and bending to the point of overstress. The connecting rod then separated from the crankshaft and punched a hole in the crankcase.

Text from the NTSB. Open the NTSB docket for ERA09FA228 for the full record.