WPR19LA014

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.

On October 23, 2018, about 1344 Pacific daylight time, a North American SNJ-5 airplane, N7969C, was destroyed when it was involved in an accident near Agoura Hills, California. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations (CFR) Part 91 personal flight. The pilot reported that, shortly after departure, he heard two loud bangs, followed by total loss of engine power, and he performed a forced landing to a highway. After touchdown, the airplane swerved to the left, the left wing impacted a concrete divider, and a postimpact fire ensued. The airplane was equipped with an R-1340-AN1 nine-cylinder, radial engine. Examination of the engine showed that the No. 2 cylinder was cracked between the 10th and 11th (from bottom of head) cylinder head cooling fin. Another crack on the No. 2 cylinder extended from the sparkplug to the base of the head. Additional damage was noted at the base between the Nos. 4 and 5 cylinders, and on the No. 1 cylinder. Disassembly showed that the No. 5 master cylinder rod end had failed on the piston side. Examination of the master rod end by the NTSB Materials Laboratory showed a fracture initiation region on the I-beam shaft, based on fine chevron and river pattern markings. The fracture surface in the immediate origin region was damaged due to mechanical contact during the failure sequence. A higher magnification image of the fracture surface adjacent to the origin region exhibited striation features typical of fatigue crack growth in hardened steel.