Maule MXT-7-180A N152HS accident near Magnolia, Arkansas

Probable cause

The mechanic's failure to properly install an oil drain line after he replaced a cylinder, which caused the engine to seize in flight due to a lack of lubrication.

NTSB analysis

The pilot was on a night cross-country flight when he heard a knocking sound in the engine. He immediately proceeded toward the nearest airport, declared an emergency, and noted that the oil pressure gauge read "0" and the oil temperature gauge read "high." When the airplane was about 5 miles south of the airport, and at an altitude of 1,700 feet, the engine seized. The pilot made a forced landing to a field and subsequently collided with a fence, causing substantial damage to the airplane. Examination of the engine revealed a large hole in the top of the crankcase and that the oil drain line for the No. 4 cylinder was not connected. A review of the engine logbook indicated that the No. 2 cylinder had been removed on the day of the accident, which would have required the No. 4 cylinder oil drain line to be disconnected. When the cylinder was placed back on the engine, the oil drain line was likely not reconnected and properly torqued per the manufacturer's maintenance manual.

Text from the NTSB. Open the NTSB docket for CEN11LA005 for the full record.