What happened
On 28 March 2004, a Boeing 777-236, registration G-VIIC, was operating a scheduled passenger flight from Barbados to London. Approximately three and a half hours into the cruise, the crew detected an unusual odour within the cabin. Shortly thereafter, a smoke warning was triggered for a toilet located near the R4 door, and smoke became visible beneath the compartment door.
Upon partially opening the door, the crew observed flames and smoke. The crew deployed a BCF fire extinguisher to suppress the fire. Once the flames were extinguished, an inspection revealed that the fire originated in a stowage area behind the toilet vanity mirror. The area's shelves were heavily stocked with servicing items, including paper towels and tissue boxes. Investigators found that a ballast assembly in the ceiling of the stowage area was hot to the touch and had come into contact with flammable materials, including a charred pack of paper napkins.
To mitigate further risk, the crew attempted to disconnect the electrical supply to the ballast assembly. After an initial attempt to trip a circuit breaker failed to turn off the lights, the crew successfully removed the electrical supply directly at the unit. The toilet was subsequently taken out of service for the remainder of the flight. There were no injuries and no fatalities among the 15 crew members or 176 passengers.
The investigation
Investigators discovered that a handwritten note in black felt-tip pen was present next to the stowage unit, warning: "Do not over stock, only 1 each item". The operator found similar warnings in all toilets across their Boeing 777 fleet, though the origin of the note remained unknown.
Furthermore, the investigation identified an ambiguity in the aircraft's electrical labeling. The circuit breaker intended to cut power to the ballast assembly for the right-side toilet was labeled "LAV LIGHTS LEFT". This breaker also controlled certain services for the left-side toilets, complicating the process of isolating the power supply.
Findings
- The fire was caused by contact between a hot ballast assembly and flammable servicing materials stored in the vanity area.
- The stowage area was overstocked with paper products, increasing the fuel load near the heat source.
- Ambiguous labeling of the circuit breaker hindered the rapid isolation of the electrical supply to the ballast assembly.