The Air Accidents Investigation Branch (AAIB) recently released its report regarding the fire on a parked Boeing 787 Dreamliner at London’s Heathrow Airport in July 2013. Investigators concluded that the fire was started as a result of “crossed and trapped” wires in the lithium battery that powered the Emergency Locator Transmitter (ELT). Contact between the wires caused a short circuit, which made the battery overheat and catch fire.
The flames directly impinged on the surrounding thermo-acoustic insulation blankets and on the composite aircraft structure in the immediate vicinity of the ELT. This elevated the temperature in the fuselage crown to the point where the resin in the composite material began to decompose, providing further fuel for the fire. As a result, a slow-burning fire became established in the fuselage crown and this fire continued to propagate from the ELT location, even after the energy from the battery thermal event was exhausted, the AAIB stated.
As a result of these findings, the Federal Aviation Administration (FAA) is re-evaluating the flammability testing that was conducted to certify Boeing’s 787 Dreamliner and is “investigating new test methods,” according to an article in The Seattle Times. The publication reports that an FAA official familiar with the certification standards said the incident “taught people something they weren’t aware of.”
The accident demonstrates that if an "intense fire starts on an airplane, the resin in the composites will burn and create a self-sustaining fire," the official told the publication.
Click here for the original report in The Seattle Times.