What happened
On July 11, 2017, a privately owned HALES CS RAND KR-2 (registration G-BYLP) was conducting a leg of an around-the-world flight, traveling from Niigata Airport toward Kounan Airfield. The aircraft, an amateur-built two-seater, was operated by a single pilot. During the flight, the aircraft encountered low clouds and a 15-knot headwind, necessitating frequent changes in altitude and power settings.
At approximately 15:45 JST, the pilot noticed the smell of gasoline fumes. Shortly after, the engine malfunctioned; although the pilot managed to temporarily restore engine function using the electric auxiliary fuel pump and carburetor heat, the engine failed completely at 15:51 JST. Seeking a safe landing site, the pilot targeted a golf course in Yano Town, Aioi City. During the forced landing, the aircraft bounced on the rough terrain and struck a two-meter-high stepped slope, which broke the fuselage and fractured both wings, resulting in the total destruction of the aircraft. The pilot sustained serious injuries.
The investigation
The Japan Transport Safety Board (JTSB) examined the aircraft's fuel system, the pilot's flight records, and meteorological data. Investigators analyzed the aircraft's liquid-level fuel gauge, which was designed to stop providing readings once the fuel level dropped below 7 UK gallons. The investigation also reviewed GPS data and video footage from the pilot's smartphone to determine flight parameters, including engine RPM and ground speed.
Findings
- The pilot was unable to monitor the decreasing fuel level once it dropped below the gauge's minimum threshold of 7 UK gallons.
- The aircraft's fuel tank structure, specifically an upward-tilted pipe at the bottom of the fuel gauge, likely caused inaccurate readings as the fuel level approached the minimum limit.
- The pilot's estimated fuel consumption rate was likely exceeded because the aircraft was operated at higher power settings (approximately 3,150 RPM) than the planned cruising and descent targets.
- Fuel exhaustion was the primary cause of the engine failure. While a fuel leakage may have contributed to the rapid depletion of fuel, investigators could not identify a specific source or location of a leak.
Safety action
- Pilots must maintain a precise understanding of remaining fuel by closely monitoring gauges and accounting for potential indication errors.
- Pilots should identify alternative aerodromes in advance to ensure a safe landing if actual fuel consumption exceeds planned estimates.