What happened
On 2 June 2002, a Rans S10 Sakota, registration G-BVCB, was conducting a private flight from CambridgesHDshire to Blackpool. While transiting the Manchester Low Level Corridor, the pilot noticed the fuel pressure gauge falling and agitation in the vapour return line. Despite switching the electric fuel pump on and selecting the right fuel tank, the engine stopped at an altitude of 1,200 feet.
During the subsequent forced landing, the pilot was distracted by a radio request regarding the number of persons on board. While on final approach at approximately 25 feet, the aircraft struck a powerline. The aircraft underwent a 360-degree turn before coming to rest in a field. The pilot sustained minor injuries, and while the aircraft suffered substantial damage to the landing gear, propeller, engine mount, wing, and tailplane, the fuselage remained intact.
The investigation
The investigation examined the aircraft's fuel system, which had recently been modified to allow the use of unleaded Mogas. This modification included a vapour return line designed to return surplus fuel and vapour to the left tank via a T-piece vent. Investigators found that the pilot had flown at a higher speed than usual to complete the journey, which likely increased fuel consumption.
While the aircraft had been refuelled the previous day, the investigation looked into whether the modification was properly documented and approved. It was noted that the pilot's previous experience was in aircraft where both tanks fed the engine simultaneously, whereas this aircraft required manual switching between tanks.
Findings
- The engine stopped because the pilot delayed switching to the right fuel tank until the left tank was depleted.
- Higher than normal fuel consumption was likely caused by the pilot cruising at a faster speed than usual.
- The fuel system modification to allow Mogas use lacked formal approval from the PFA Engineering Department.
- The ground test performed after the modification did not confirm that fuel was successfully returning to the left tank.
- Poor lighting conditions made it difficult for the pilot to visually assess the fuel levels in the translucent tanks.