Beech E33 N7697N accident near Lenoir, North Carolina

Probable cause

The mechanic’s inadequate annual inspection of the airplane and failure to comply with an applicable airworthiness directive, which resulted in a total loss of engine power due to oil starvation.

NTSB analysis

After an annual inspection on the airplane, the pilot was repositioning to his home airport. About 45 minutes into the cross-country flight, the engine rpm increased. The pilot reduced the rpm but about 5 minutes later the rpm increased again. The pilot tried to adjust the rpm again but the second time it would not adjust. He decided to land at the nearest airport but about 5 minutes later, the engine sustained a catastrophic failure, with engine parts exiting from the top of the engine cowling. The pilot glided to an airport and landed long and fast on a grass runway. The airplane departed the end of the runway and contacted a fence, resulting in substantial damage to both wings.

Postaccident examination of the engine revealed that the oil filter adapter was loose, and the gasket was split open, which allowed the oil to leak out from the engine. The lack of oil likely resulted the propeller governor decreasing the propeller blade angle and increasing the rpm. The lack of oil to the crankshaft and bearing journals also likely resulted in heat buildup and fracture the Nos. 5 and 6 connecting rods due to oil starvation.

The airplane’s most recent annual inspection had been completed about 1 month, and less than 5 operational hours before the accident flight. The engine and oil filter adapter installed on the accident airplane were the subject of an airworthiness directive (AD) that had been issued nearly 3 years before the annual inspection. The AD was prompted by previous losses of engine power due to oil starvation because the adapter vibrated loose and allowed oil loss. The AD required that the fiber gasket be removed and replaced with a copper gasket. Review of the airplane’s maintenance records revealed no evidence that the AD had been complied with. Had it been accomplished, the mechanic would have most likely removed the oil filter adapter, installed the new gasket, reinstalled the oil filter adapter, and tightened its associated hardware, which would have prevented the oil leak during the accident flight.

Text from the NTSB. Open the NTSB docket for ERA25LA157 for the full record.