Fpna Llc A-22 Valor N721FP accident near Hunting Island, South Carolina

Probable cause

Maintenance personnel's inadequate inspection of the oil system's fittings during a routine oil servicing, which resulted in oil starvation due to a loose and/or detached oil line B-nut fitting that led to the engine seizing while in flight.

NTSB analysis

While maneuvering as part of a formation flight, the pilot noticed that the electronic instruments were dimming and that the oil pressure gauge indicated zero. About 10 seconds later, the engine seized and the pilot performed a forced landing on a dirt road. The airplane incurred substantial damage during landing when it veered into a ditch. A postaccident examination of the engine revealed that the No.1 cylinder's connecting rod was protruding through the top of the engine case. Upon removal of the engine cowling, the brass B-nut was found separated from the oil cooler fitting. There was no apparent damage to the threads on the inside of the nut and no damage on the outside of the fitting. Oil was present in the oil sump and on the oil dipstick.

The engine had a dry sump forced lubrication system. The oil pump extracts the oil from the oil tank via the oil cooler and forces it through the oil filter to the engine. According to notations found in the airplane's maintenance logbook, the engine's oil had been changed 1.6 flight hours prior to the accident. According to the owner, maintenance personnel did not touch the oil cooler or fittings during the oil change service. The engine manufacturer’s Service Instructions manual had a warning associated with servicing and purging of the oil system. The warning stated that maintenance personnel should carefully check all lubrication system connections, lines and clamps for leaks and security.

Text from the NTSB. Open the NTSB docket for ERA10LA100 for the full record.