What happened
On 14 October 2013, a Boeing 747-436, registration G-BNLW, was operating a commercial passenger flight from Dallas/Fort Worth to London Heathrow. Approximately two hours before arrival, the flight crew and cabin crew began to notice a distinct, acrid electrical burning smell. This was followed by a cockpit alert indicating smoke in either a lavatory or the air conditioning cooling duct.
Shortly after the initial smell was detected, cabin crew reported visible flames and smoke emerging from an In-Flight Entertainment (IFE) component, specifically a Video Modulator (VMOD), located in the Galley 4 area. The crew attempted to suppress the fire using BCF extinguishers, but the fire repeatedly re-ignited. In total, five extinguishers were deployed to manage the event. The flight crew did not initiate a distress call or don oxygen masks, and they eventually opted not to follow certain checklist items due to concerns regarding the loss of cabin lighting.
The investigation
The investigation focused on the failure to effectively extinguish the fire and the subsequent re-ignition of the equipment. It was established that while the crew had attempted to isolate the electrical power, the VMOD unit likely remained energized. The investigation examined the procedures available to the crew, noting that the cabin crew's manual provided instructions for isolating seat and IFE power, but the crew's actions were inconsistent with a full isolation of the unit.
Furthermore, the investigation looked into the flight crew's use of the Non-Normal Checklist (NNC). It was found that the crew did not execute the 'Smoke, Fire or Fumes' checklist, which included instructions to turn off the main IFE and PC power switches and to switch off utility power. The investigation also noted that the crew's decision to avoid the utility power switch was motivated by a desire to maintain cabin lighting.
Findings
- The fire originated in a Video Modulator (VMOD) unit within the IFE system.
- The fire repeatedly re-ignited because the IFE power was not effectively isolated.
- The cabin crew had only partially actioned the isolation procedures, likely relying on memory rather than the manual.
- The flight crew did not perform the required actions in the 'Smoke, Fire or Fumes' checklist.
- There was a lack of specific training for cabin crew regarding the use of the 'B747 Quick Reference Guide'.
Safety action
Following the incident, the operator implemented several internal safety recommendations. These include improvements to cabin and flight crew training, specifically regarding the use of checklists, the proper operation of fire extinguishers, and a better understanding of the electrical isolation switches in the galley. The operator is also reviewing flight crew procedures to ensure that smoke warnings prompt the immediate use of the appropriate checklists.