What happened
On 30 July 2003, a Boeing 737-300, registration G-LGTI, was undergoing pre-flight preparations at Newcastle Airport for a scheduled passenger flight to London Gatwick. While the aircraft was connected to external ground power, the crew noticed that several ground service circuit breakers had tripped and could not be reset. During attempts by an onboard engineer to rectify the electrical fault, additional circuit breakers tripped.
Shortly after, the commander noticed a burning smell and increasing amounts of smoke within the flight deck. The commander ordered the aircraft to be shut down and initiated an immediate evacuation of all 6 crew members. Smoke was observed emanating from the forward electronics bay and the airstairs. The commander contacted the airport call centre to request the fire service, specifically requesting a single vehicle to avoid causing alarm to passengers in the terminal.
The investigation
An AAIB field investigation examined the aircraft and found fire damage to electrical wiring and insulation beneath the cockpit floor, specifically in the area of the forward toilet service panel. The investigation identified that several critical systems, including the autothrottle, engine ignition, and weather radar, had been affected by the damage.
Investigators found evidence of moisture and toilet sanitising fluid in the area. Laboratory analysis of the wiring conducted by the manufacturer revealed that the insulation on the 115V AC galley power feeder cables had been torn away, leaving wires exposed. It was noted that this damage may have been sustained during previous maintenance work on the toilet service panel in November 2002.
Findings
- The primary cause of the fire was arcing between exposed galley power feeder cables.
- The 115V AC galley feeder cables had pre-existing damage where the insulation had been mechanically torn away.
- This damage created a potential for arcing, which eventually led to arc tracking on the polyimide insulated wires, resulting in a short-duration flash fire.
- The investigation also noted that airport call centre procedures at the time did not explicitly instruct operators to notify the Airport Fire Service (AFS) or Air Traffic Control, which contributed to a ten-minute delay in the arrival of the AFS.
Safety action
- The aircraft operator performed visual inspections of the wiring in similar areas on six other Boeing 737 aircraft, finding no further issues.
- Newcastle Airport revised its emergency procedures to ensure call centre operators notify the Airport Fire Service directly during fire incidents.