Amateur-built RV-6 N6383W accident near Paulden, Arizona

Probable cause

A total loss of engine power due to oil starvation as a result of a leak from the inadequate weld repair of a high-pressure oil line. Also causal was the pilot's failure to maintain adequate airspeed while maneuvering that resulted in a stall during an attempted off-field landing and the pilot's decision to continue flight with a known discrepancy.

NTSB analysis

A witness observed the accident airplane performing turns to the left and right and trailing white smoke. The witness stated that the airplane was about "tree-top level" when it pitched down and impacted the ground. Examination by a Federal Aviation Administration inspector revealed oil along the bottom side of the fuselage and on the tailwheel. A friend of the pilot, who was also an aircraft mechanic, reported that prior to the accident flight he and the pilot found an oil leak originating from a stainless steel high-pressure oil line from the propeller governor to the forward area of the engine crankcase. The mechanic stated that he had removed the oil line and the pilot had it repaired by a local weld shop. After reinstallation of the oil line, the mechanic conducted an engine run and did not observe any oil leaks originating from the oil line. The pilot then decided to fly the airplane around the area on a test flight. According to the mechanic, as the airplane departed the runway, he observed a trail of white smoke originating from the airplane. Despite two requests by the mechanic to return to the airport, the pilot stated that "everything was fine" and he was going to continue to a nearby airport. No further radio communication was received from the pilot. Examination of the engine revealed that the stainless steel high pressure oil line from the propeller governor was in place. The oil line exhibited a repair weld on the forward area of the line, and corresponding wear marks were observed on the engine crankcase. The oil line was removed and the forward end of the oil line was capped off using a bolt. The area of the weld was placed under water and compressed air pressure was applied to the opposite end of the oil line. A leak was observed originating from the area of the weld. Partial disassembly of the engine revealed that the number two connecting rod was separated from the crankshaft and exhibited signatures consistent with oil starvation.

Text from the NTSB. Open the NTSB docket for WPR09LA153 for the full record.