Amateur-built S7 COURIER N831RS accident near West Liberty, Kentucky

Probable cause

The pilot's failure to verify that the engine oil tank contained adequate oil for the cross-country flight, which resulted in a total loss of engine power as a result of lack of lubrication. Contributing to the accident was the incorrect oil consumption information listed in the pilot operating handbook.

NTSB analysis

While en route, about 2 hours into the cross-country flight, the engine lost all power. The pilot primed and restarted it twice; however, the engine would not sustain power. On the third attempt at restarting, the pilot noted that the propeller would not turn over, and he elected to perform a forced landing to a field. During the landing, the airplane struck a fence, which resulted in substantial damage to the left wing and engine mounts.

Examination of the engine revealed that the oil injection tank was empty, and the aft piston exhibited vertical scoring, consistent with lack of lubrication. It is likely that the aft piston seized in flight as a result of a lack of lubrication, which resulted in the total loss of engine power. Leak testing of the oil system revealed no leakage; therefore, it is likely that the pilot departed on the flight without sufficient oil. Although the pilot should have checked the oil before the flight, the pilot operating handbook, which was written by the builder, contained incorrect oil consumption information, which likely contributed to the pilot's misunderstanding of the amount of oil needed for flight.

Text from the NTSB. Open the NTSB docket for ERA20LA039 for the full record.