Piper PA-28-151 N4399X accident near Marana, Arizona

Probable cause

A total loss of engine power due to a failure of the No. 4 cylinder piston boss.

NTSB analysis

The flight instructor and student pilot were conducting a cross-country flight when the engine began to run rough and make grinding noises. The engine then stopped producing power, and the propeller would not windmill. The instructor attempted to restart the engine and performed a forced landing to a field, during which the airplane sustained substantial damage to both wings.

Postaccident examination of the engine revealed significant wear to the camshaft lobes, as well as evidence of catastrophic failure of the No. 4 piston assembly. The damage appeared to originate from the area of the piston pin and boss; however, the failure features were obliterated during the event, preventing an accurate assessment of its origin.

The engine was most recently overhauled about 21 years and 2,190 flight hours before the accident. The manufacturer’s recommended time between overhaul (TBO) interval was 2,200 flight hours or 12 years, whichever occurs first.

Text from the NTSB. Open the NTSB docket for ANC24LA027 for the full record.