CEN20LA301 · Vans RV4 Undesignat

After a full stop landing to refuel on a cross-country flight in the experimental airplane, the pilot noticed a chaffed oil line leading to the propellor governor. The pilot, with assistance from a local mechanic, removed the damaged oil line and replaced it with a used serviceable line. The pilot pre-flighted the airplane, took off, and continued his flight. About 70 minutes into the flight, the pilot observed oil on the windscreen. As the pilot maneuvered for a precautionary landing at a nearby airport, the engine stopped producing power. About 1/2 mile from the airport, the pilot attempted to land on a roadway. The airplane impacted power lines and the ground. The pilot stated that he could not see the power lines through the oil-covered windscreen. The airplane came to rest in a ditch adjacent to the roadway, resulting in structural damage to the fuselage and empennage. Examination of the airplane and engine after the accident revealed a crack in the oil line leading to the propeller governor from its connection at the engine case. There was no clamp installed to secure the line. A conditional airworthiness inspection had recently been completed on the experimental airplane. According to Federal Aviation Administration Airworthiness Directive (AD) 90-04-06R1, a clamp should have been installed on the oil line leading to the propeller governor. The pilot reported that when he replaced the oil line, there was no clamp present, so he did not install a clamp and was not aware of the applicable AD. He stated that had he been aware of the AD, he would have installed a new oil line and clamp. The available evidence indicates that the pilot’s improper installation of the oil line resulted in the in-flight loss of oil and subsequent total loss of engine power.

Verbatim NTSB analysis and probable cause from the NTSB dataset