What happened
On 8 May 2001, a Boeing 757-236, registration G-BPEC, was operating a public transport flight from London Heathrow to Milan. Shortly after departure from Heathrow, air traffic control notified the crew that another aircraft on the ground had reported thick black smoke emanating from its left engine. While the crew monitored engine instruments for abnormalities during the climb, no immediate signs of failure were detected. Following a visual inspection by the cabin services director and consultations with ground engineers, the flight proceeded toward Milan.
During the flight, the crew identified an emerging fuel imbalance. Although no smoke or visible fuel loss was noted by the first officer during a cabin inspection, the decision was made to divert to Geneva Airport. Upon arrival, the aircraft declared a 'PAN' and was instructed by ATC to stop on the runway. After landing, the left engine was shut down, and the aircraft was met by the Airport Fire Service (AFS).
As the AFS applied foam to the left engine, the commander established contact with fire officials, who confirmed a substantial fuel leak was occurring. The fire service reported that fuel was leaking near the main landing gear, where heat from the brakes was causing the fuel to vaporise, creating a significant fire hazard. Consequently, an emergency evacuation was ordered. While 89 passengers successfully exited via the right-side slides, two elderly passengers were unable to use the slides and remained on board with the crew until they could be safely disembarked via steps.
The investigation
An engineering investigation by the operator determined that the leak originated from the high-pressure fuel pump, a component that had been replaced the previous night. The investigation established that a leak had developed at the joint between the pump and the pipe. This was caused by a failure of a securing bolt to properly hold the pipe due to a damaged helicoil thread insert.
Prior to the flight, the engine had undergone both idle and high-power ground leak checks following the pump replacement, neither of which had revealed any leakage.