What happened
On 24 August 1998, a Pierre Robin HR100/210, registration G-BBPW, was conducting a flight for a Certificate of Airworthiness air test following a recent annual inspection. After performing preflight checks and refueling the aircraft to a specific weight, the pilot taxied for approximately 10 minutes and conducted engine power checks.
During the takeoff from Runway 27, the aircraft initially accelerated normally with no abnormal engine indications. However, upon reaching an altitude of roughly 400 feet, the engine experienced a sudden loss of power. The pilot attempted to troubleshoot the issue by checking the magnetos, fuel selector, and mixture, and even activated the electric fuel pump. Despite these efforts, the fuel flow dropped significantly from 14 gallons per hour to less than 6 gallons per hour.
As the aircraft had already passed the upwind end of the runway, the pilot focused on an emergency landing in the nearest unploughed field. The aircraft struck the ground heavily and, due to excessive speed, collided with a low stone wall. The impact caused the landing gear to break away and the aircraft to come to rest on its underside. There were no injuries to the two occupants, though the aircraft sustained damage to the wings, lower fuselage, and propeller.
The investigation
Investigators examined the aircraft's fuel system and engine compartment. The inspection revealed that the fuel selector was correctly positioned to the left main tank and the electric pump was set to the takeoff position. The engine was mechanically sound, and the fuel tank vents and outlets were unobstructed. Testing confirmed the electric fuel pump was functioning correctly, delivering approximately 53 imperial gallons per hour, and the fuel filter was clean. While the impact with the stone wall had disrupted the pipework below the cockpit floor and torn the strainer from its connections, these were consequences of the crash rather than causes of the power loss.
Findings
- The engine power loss was accompanied by a sharp reduction in fuel flow.
- Fuel vapour lock within the fuel lines, potentially caused by the extended taxiing period prior to takeoff, was suggested as a possible contributing factor.