NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The commercial pilot reported that, during cruise on the fire reconnaissance flight, he heard a loud pop, followed by oil covering the windscreen; the engine subsequently experienced a total loss of power. Despite the pilot’s attempts, the engine would not restart, and he initiated a forced landing to an open field. During the landing roll, the nose landing gear separated from the airplane and the right wing impacted the ground. Postaccident examination of the engine revealed that the bottom portion of the No. 6 cylinder piston, piston pin, and connecting rod cap were separated.Metallurgical examination of the piston pin revealed evidence of a fatigue fracture originating from the outside of the pin that progressed inward until the final fracture along the middle of the pin cross-section. The fatigue crack initiation site did not reveal any material or mechanical defects, such as pits, voids, or inclusions. Examination of the piston, connecting rod bolts, and connecting rod cap revealed fractures consistent with overstress. No additional anomalies were noted with the engine.