Amateur-built ONEX N1950J accident near Fresno, California

Probable cause

The pilot/builder's failure to properly align the Force One Main Bearing, which resulted in a blockage of the oil transfer hole and culminated with a total engine power loss. Contributing to the accident was the pilot's failure to arrest the bank and sink rate prior to impact.

NTSB analysis

The pilot/builder was carrying out the initial flight test after recently building the amateur experimental airplane. Shortly after takeoff, the airplane's engine experienced a total power loss and the pilot initiated a descending left turn in order to avoid an airport fence. Subsequently, the airplane impacted terrain, in a nose down attitude with the left wing low.

An examination of the engine revealed that the Force One Main Bearing seized to the crankshaft. Further, there were multiple circular impressions on the bearing surface. Based on this evidence, it is likely that while building the experimental engine, the pilot did not properly align the Force One Main Bearing, and the oil feed hole was inadvertently used as the dowel pin hole, which resulted in a blockage of the oil transfer hole, thus preventing oil into the bearing and resulted in engine seizure and total power loss.

Text from the NTSB. Open the NTSB docket for WPR16LA050 for the full record.