North American SNJ N7969C accident near Agoura Hills, California

Probable cause

The failure of the No. 5 piston rod end due to fatigue, which resulted in a total loss of engine power.

NTSB analysis

The pilot reported that, shortly after departure, he heard two loud bangs followed by total loss of engine power. The pilot performed a forced landing to a highway, during which the airplane swerved to the left, the left wing impacted a concrete center divider, and a postimpact fire ensued.

Initial examination of the engine found that the No. 2 cylinder was cracked, and the No. 1 cylinder and the base between the Nos. 4 and 5 cylinders displayed damage. Disassembly of the engine revealed the piston-end master rod piece from the No. 5 cylinder fractured through the I-beam shaft. Microscopic examination of the fracture surface showed evidence of fatigue. The initiation point of the fatigue fracture was damaged due to mechanical contact during the failure sequence.

The accident is consistent with a total loss of engine power following the failure of the No. 5 master rod end. The initiating point and cause of the fatigue failure could not be identified based on the available evidence.

Text from the NTSB. Open the NTSB docket for WPR19LA014 for the full record.