What happened
On October 21, 2005, a privately owned Piper J3C-65, registration G-KIRK, departed Niigata Airport for a leisure flight destined for Hiroshima Airport. The aircraft, which was part of a global journey, was operated by a single pilot-in-command.
While traversing the airspace near Toyama Prefecture, the engine experienced a failure. The pilot attempted standard recovery procedures, including checking the carburetor and mixture, and switched fuel sources from the nose tank to the wing tanks. Although the engine briefly restarted, the pilot continued toward the destination, eventually flying near the coast to maintain emergency landing options.
As the aircraft passed over a hill near Kanazawa City, the engine failed a second time. At an altitude of approximately 600 feet, the engine intermittently regained power, but the pilot, observing the low altitude and the lack of suitable landing sites, decided to execute an emergency landing on a road currently under construction. During the descent, the aircraft struck a special-purpose vehicle, a mini-truck, and a cargo truck. The pilot sustained slight injuries, but the aircraft was substantially destroyed.
The investigation
The investigation focused on the mechanical failure of the engine and the presence of debris within the fuel system. Investigators conducted a teardown of the Continental C90-12F engine and analyzed the composition of the fuel and lubricating oil.
Key elements of the examination included:
- A microscopic analysis of the carburetor inlet screen, which revealed a significant accumulation of grease-like foreign matter.
- An inspection of the fuel tanks, which showed evidence of corrosion in several sections.
- An evaluation of the fuel used, which was identified as automotive gasoline, a substance permitted by the engine manufacturer's manual.
- An assessment of the aircraft's recent history, noting it had been parked outdoors in South Korea for approximately five months prior to the flight.
Findings
Technical analysis determined that the engine trouble was caused by a restriction of fuel flow resulting from the blockage of the carburetor inlet screen by foreign matter. This material, described as a grease-like substance, was found to be the same residue the pilot had previously encountered and attempted to clean using compressed air in South Korea.
While the pilot had successfully cleared the fuel strainer, the investigation concluded that the cleaning was insufficient to remove all debris from the wider fuel lines and the carburetor itself. The accumulation of this matter was likely a result of long-term storage in an outdoor environment, which allowed for fuel evaporation and the subsequent formation of gums and organic acids within the aluminum tanks.
Although the pilot's decision to continue the flight after the initial engine failure contributed to the sequence of events, the primary mechanical cause was the failure to completely eliminate the accumulated foreign matter from the fuel system.