The pilot of the Piper Pawnee took off from Baxter Springs, Kan., then noticed a decrease in the engine’s oil pressure, followed by a loss of engine power. The pilot was slightly injured in the forced landing.
An examination of the engine revealed that the No. 2 piston had failed. In addition, each of the spark plugs had two washers installed, instead of one, and the oil filter contained many metal particles.
Investigators determined the two washers likely altered the detonation characteristics of the pistons, causing them to overheat. As the No. 2 piston degraded, metal particles collected in the oil filter.
Maintenance records indicate that the engine was overdue for a recommended oil change. The mechanic who performed the last annual inspection was not aware that additional spark plug washers had been installed on the engine.
The NTSB determined the probable cause as the loss of engine power due to improper maintenance by an unknown individual that led to the degradation and deterioration of the No. 2 piston, which was undetected because of overdue maintenance.
NTSB Identification: CEN13LA280
This May 2013 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.