Cessna 172 N8311X accident near Pleasant Valley, New York

Probable cause

A total loss of engine power due to failure of the magnetos, which were not overhauled in accordance with the manufacturer’s time specifications.

NTSB analysis

The student pilot was practicing takeoffs and landings when the engine sputtered and lost all power while on final approach. The student pilot tried to restart the engine to no avail and subsequently made a forced landing in a wooded area. The airplane came to rest inverted in swampy terrain amongst trees.

The magnetos were removed from the engine during the postaccident examination, and they failed to produce sparks when tested. Further examination of the magnetos revealed extensive corrosion present on the coil laminations between the coil and magnet. It is likely the rotor was unable to transmit electricity to the coil and therefore the magneto was unable to produce a spark. The magneto manufacturer maintenance manual and overhaul manual states the magneto time in service allowance is the time before overhaul for the engine or 12 years. The magnetos had not been overhauled and were 14 and 23 years old. No other engine anomalies were identified that would have prevented normal operation.

Text from the NTSB. Open the NTSB docket for ERA21LA091 for the full record.