Beech F33A N3291X accident near Uvalde, Texas

Probable cause

The loose oil filter, which resulted in oil starvation and a total loss of engine power in flight.

NTSB analysis

The pilot departed on a cross-country flight, which was the second flight after recent maintenance. The pilot reported that, about 48 minutes into the flight at 8,500 ft mean sea level, the manifold pressure suddenly dropped with a simultaneous engine explosion; oil was on the windshield, and "there was fire everywhere." He reduced the mixture, throttle, and propeller controls. The pilot reported the emergency to air traffic control and received vectors to the closest airstrip, which was about 6 nautical miles south-southeast. He indicated that he had difficulty maintaining glide speed because the nose of the airplane was pitching upward. During the descent, he extended the landing gear, and the airplane impacted trees and terrain and came to rest about 500 yards west of the intended runway. The airplane was destroyed by a postimpact fire.

A postaccident examination of the airplane revealed that the engine exhibited excessive heat signatures consistent with a lack of oil lubrication. The lack of oil resulted in the No. 2 connecting rod becoming disconnected from the crankshaft, which punctured a large hole in the crankcase. The engine oil filter was found loose on its mount and safety wired in the counterclockwise direction. During the examination, when the oil filter was manually rotated about one-half turn clockwise to tighten, the safety wire prevented it from further rotation; however, the oil filter could have rotated further. Due to the fire damage, investigators could not determine if there had been a gasket installed between the oil filter and mount. The exhaust manifold directly underneath the oil filter had burn marks, which were likely from oil that had leaked from the oil filter onto the exhaust manifold. Based on the available evidence, it is likely that the loose oil filter allowed oil to leak from the engine and resulted in oil starvation and a total loss of engine power.

Text from the NTSB. Open the NTSB docket for CEN18LA213 for the full record.