What happened
The pilot of a Piper J-5 had recently acquired the aircraft and was operating it on a personal flight back to his home airport. During this leg of the journey, the airplane experienced a complete loss of power due to fuel exhaustion. The aircraft had been in the air for approximately three and a half hours. According to the pilot's account, the engine was consuming roughly eight gallons of fuel per hour. Given that the Piper J-5 typically possesses an endurance capability exceeding four hours at cruise power settings, the depletion of fuel reserves was unexpected under normal circumstances.
As the situation became critical, the pilot initiated an emergency landing procedure. During this forced landing attempt, the aircraft struck a ditch on the ground. The impact caused the nose of the airplane to collapse forward, resulting in significant structural damage to the front section of the airframe.
The investigation
Following the accident, investigators examined the aircraft and the circumstances surrounding the fuel loss. A critical mechanical anomaly was discovered regarding the left wing fuel tank. The cap for this tank had been installed with the pressurization tube oriented aft rather than forward into the slipstream. This incorrect orientation allowed air to flow over the tube in a manner that created a siphoning effect.
Both the pilot and the responding FAA inspector concurred that the backward-facing cap was the primary mechanism for fuel loss. The airflow generated during flight actively siphoned fuel out of the tank, depleting the supply before the engine could be fed. There was no evidence found to suggest an engine malfunction or any other source of fuel leakage, such as a ruptured line or faulty valve.
Findings
The investigation determined that the root cause of the accident was the improper installation of the left fuel tank cap. This error led directly to fuel exhaustion via siphoning. The pilot's calculation of endurance was correct based on standard consumption rates, but the physical configuration of the fuel system rendered those calculations invalid for this specific flight. No other mechanical failures or environmental factors contributed to the outcome.