Amateur-built B N453WB accident near Springfield, Ohio

Probable cause

The flight crew’s failure to maintain airplane control following a partial loss of engine thrust during cruise flight. Contributing to the accident was the failed weld as a result of incomplete welding on the left propeller shaft, which led to the partial loss of engine thrust.

NTSB analysis

The experimental amateur-built replica airplane was on a test flight with two pilot-rated occupants. Another pilot heard a radio transmission from the accident airplane indicating that they were going to land in a field about 5 miles north of the departure airport. Witnesses reported that the airplane’s engine rpm varied while it was flying at a low altitude. The airplane was then observed in a spiraling descent to the ground. Postaccident examination of the airplane’s left propeller shaft revealed a broken weld, which would have prevented the left propeller from being driven by the engine. Further examination of the joint identified incomplete weld penetration during welding, thus about 25 to 35 percent of the through thickness of the propeller shaft tube was not welded to the propeller shaft end. This incomplete weld penetration occurred in the inner areas of the joint. Visible defects, such as pores and voids, were observed in the welded areas. The part’s engineering drawing specifies complete weld penetration. The on-scene accident examination of the wreckage did not reveal any other preimpact anomalies. Despite the resultant partial loss of thrust, the flight crew should have been able to maintain control of the airplane during the forced landing attempt.

Text from the NTSB. Open the NTSB docket for CEN11FA528 for the full record.