Universal Stinson 108 N39443 accident near Portland, Maine

Probable cause

A fatigue failure of the No. 3 piston skirt, which resulted in a total loss of engine power and the subsequent ditching in the ocean.

NTSB analysis

The airplane was flying over the ocean, along the coast at altitudes between 500 to 1,000 feet mean sea level, when the pilot reported a total loss of engine power and indicated that he was not going to be able to glide to the shore. The airplane subsequently impacted water about 100 yards from the shore and sank to a depth of about 70 feet. Postaccident examination of the airplane’s engine revealed that the No. 3 piston skirt fractured, and the resultant debris entered the engine and camshaft gear, affecting the magneto timing. Metallurgical examination of the piston skirt revealed fatigue originating near a machined through-hole. Although the No. 3 piston was overhauled about 5 years before the accident, it was an original piston on the accident engine, which was more than 65 years old.

Text from the NTSB. Open the NTSB docket for ERA12LA411 for the full record.