Casualties unknown

Piper J-5 Fuel Exhaustion After Improperly Installed Fuel Cap (N35931)

Broadus, MT, US

On April 17, 1992, a Piper J-5A (registration N35931) operated by Patten, Clayton P. was involved in an aviation accident near Broadus, MT. Investigators recorded the probable cause as: The left fuel tank cap was installed backwards, causing fuel siphoning that led to fuel exhaustion. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.

Sourcesthe U.S. National Transportation Safety Board (NTSB) historical archivePrimary reportUpdated 2026-06-10Data APIEditorial standards

A Piper J-5, recently purchased, ran out of fuel during a return flight. The left fuel tank cap was installed backwards, causing fuel siphoning. The aircraft struck a ditch and nosed over during the emergency landing.

Accident Details

The pilot of a Piper J-5 had just purchased the aircraft and was returning to his home airport when the engine stopped due to fuel exhaustion. During the subsequent emergency landing, the aircraft struck a ditch and nosed over. The pilot reported that the aircraft had been burning approximately eight gallons of fuel per hour. The flight had been airborne for about three and a half hours, and the aircraft should have had an endurance of over four hours at cruise.

Fuel System Examination

After the accident, it was discovered that the left fuel tank cap had been installed with the pressurization tube facing aft instead of forward into the slipstream. Both the pilot and the FAA inspector who responded to the accident determined that the backwards cap had siphoned off some of the fuel, leading to fuel exhaustion. No evidence of an engine malfunction or other source of fuel leakage was found.

Probable cause

The left fuel tank cap was installed backwards, causing fuel siphoning that led to fuel exhaustion.

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001211X14530. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.