Vapor lock contributes to crash

The pilot reported that he had started, warmed up, and then shut down the Zenith CH-750’s engine about an hour before the accident flight.

Shortly after takeoff for the personal flight, the airplane’s engine lost total power.

He conducted a forced landing on a hill near Morristown, Minnesota, which resulted in substantial damage to the nose landing gear, fuselage, and left wing. The pilot was seriously injured in the crash.

The pilot said he had fueled the airplane that morning with 82-octane automotive fuel that he had recently purchased from a service station.

However, post-accident examination revealed that the fuel was yellow in color and smelled like “aged” automobile fuel.

The top spark plugs appeared aged, and the electrodes were corroded, which could have affected engine performance.

The airplane was not equipped with a fuel vapor return line to prevent fuel vapor lock. Given that old automotive fuel was found in the fuel system and that a fuel vapor return line had not been installed, it is likely that the engine lost power due to vapor lock.

It is also likely that the corrosion of the spark plugs and the spacing of the electrode gaps contributed to the loss of engine power.

Probable cause: A total loss of engine power due to fuel vapor lock. Contributing to the loss of engine power were the corrosion of the spark plugs and the spacing of the electrode gaps.

NTSB Identification: CEN17LA021

This October 2016 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.