What happened
On 29 September 1998, a Boeing 747-400, registration 9M-MPD, was undergoing engine start-up procedures at London Heathrow Airport. The aircraft had been pushed back from Stand J8 into the 'Juliet' cul-de-sac. Because the auxiliary power unit was unavailable, the crew had already started engines 1 and 4. During the attempt to start the number 3 engine, a fire ignited within the jet pipe, which was immediately reported to the flight deck by ground personnel.
While the crew had not issued an official evacuation order, a passenger moved toward the rear of the cabin and opened door 5L. This action triggered a 'door open' alert in the cockpit and caused the emergency slide to deploy. The passenger exited the aircraft via the slide, followed by several other individuals. Fearing that the jet efflux from the running engines posed a threat to the people on the ground, the pilots shut down all engines. Ground staff and airfield operations personnel attempted to direct the evacuees to lie down to avoid the engine blast. Ultimately, the passengers, including two who sustained minor injuries, were escorted to the terminal.
The investigation
Investigators examined the damage to the aircraft, which included scorch marks in the number 3 engine jet pipe, damage to the right high-speed aileron and certain flap sections, and the removal of the number 7 'boat fairing'. The investigation into the engine's condition was conducted in coordination with the airline's maintenance facility in Malaysia.
Data from the aircraft's Central Maintenance Computer showed no evidence that engine limitations, such as exhaust gas temperature, had been breached. To troubleshoot the issue, the crew performed a manual start of the engine, which functioned normally. As a preventative measure, the fuel pump, electronic engine control, and fuel management unit were replaced. The removed parts were sent to the manufacturers for analysis to determine if a component failure caused the fire. While investigators noted that pooled fuel from a previous shutdown could have been the cause, a definitive conclusion regarding component defects was pending.
Findings
- A fire ignited in the number 3 engine jet pipe during the start sequence.
- The unauthorized opening of the aircraft door by a passenger led to an unplanned evacuation and the deployment of the emergency slide.
- The crew shut down all engines to protect ground personnel from the danger of jet efflux.
- The fire may have been caused by fuel pooling from a previous engine shutdown.