Raytheon Aircraft Company A36 N517DJ accident near Fallon, Nevada

Probable cause

A fatigue failure of the No. 5 connecting rod, which resulted in a catastrophic engine failure during the initial climb and a subsequent forced landing.

NTSB analysis

The pilot reported that, during climbout, when the airplane was about 1,000 ft above ground level, the engine lost power. The pilot subsequently maneuvered the airplane to attempt to land on the departure runway. The airplane touched down short of the runway in rough, desert terrain, which resulted in substantial damage to the wings, fuselage, and empennage.

A postaccident engine examination revealed that the No. 5 connecting rod cap and one of its two bolts had fractured midlength; the opposite bolt was intact with the nut still fastened. Metallurgical examination revealed that the No. 5 connecting rod had failed due to a fatigue crack that had initiated on the outer surface of the nut-facing boss. The crack propagated inward until the final cross-section of the connecting rod yoke failed in overstress, which then catastrophically breeched the left side of the engine case. The fatigue crack did not show any material imperfections; however, the surface finish of the boss where the fatigue crack initiated was consistent with it having been shot peened. Although shot peening is performed to impart compressive stresses to prevent fatigue crack initiation, excessive peening times may sufficiently alter the surface to create stress concentrators. However, the configuration of the fractured rod yoke precluded any accurate surface roughness measurements and, therefore, it could not be determined if improper surface modification had occurred.

Text from the NTSB. Open the NTSB docket for WPR13LA321 for the full record.