Bad idea: Flying with known oil leak

This November 2007 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.

Aircraft: Piper Super Cub. Location: Durbin, W.Va. Injuries: None. Aircraft damage: Substantial.

What reportedly happened: The day before the accident the pilot noticed an oil leak and oil covering part of the windshield and firewall. He informed his company, and was told if the leak was not too serious, he should fly the airplane to a nearby airport where a company mechanic could examine the engine.

Prior to departure on the morning of the accident, a local mechanic examined the engine and did not observe a significant oil leak, so the pilot decided to depart as instructed. While en route to the destination airport, at an altitude of 5,000 feet, the pilot began to smell oil and observed smoke emanating from the engine. Shortly after, he heard an “explosion” and observed a “chunk of oil” blow out of the engine and cover the windshield. The oil pressure gauge continually decreased. The pilot made an emergency landing on a dirt road. During the rollout the right wing hit a tree and was substantially damaged.

Examination of the engine revealed the crankshaft oil seal was partially dislodged, and protruding from the front of the engine case. The most recent condition inspection was completed two months prior to the accident, with no anomalies noted. The airplane flew 43 hours since the inspection.

Probable cause: The loss of engine power while in cruise flight due to the partially separated crankshaft oil seal.

For more information: NTSB.gov