Piper PA-28-181 N30997 accident near Casper, Wyoming

Probable cause

A total loss of engine power during cruise flight due to a failed piston pin plug, which resulted in engine oil contamination and subsequent oil starvation. Contributing to the loss of power was the failure of maintenance personnel to identify contaminants produced by the failing plug during the last oil filter inspection.

NTSB analysis

During cruise flight, the engine sustained a reduction in oil pressure followed by a total loss of power. The student pilot then performed a forced landing into a field. Subsequent examination of the engine revealed that a piston pin plug had disintegrated, the fragments of which contaminated the oil passages and caused oil starvation and the subsequent engine seizure.

The engine's manufacturer issued a service instruction warning of such piston pin wear, recommending oil filter element inspection or spectrographic oil analysis at each oil change, not to exceed 50 hours of engine operation. The engine had undergone an oil change about 8 flight hours prior to the accident and the mechanic reported that the oil filter element appeared to be normal. Based on the relatively short period between the last oil filter inspection and the engine failure, the oil filter inspection should have revealed ample evidence of piston pin wear.

Text from the NTSB. Open the NTSB docket for WPR12LA161 for the full record.