The 12 July fire in a parked, unattended Ethiopian Airlines Boeing 787 on a remote stand at Heathrow wasn’t associated with one of the aircraft’s two main battery power packs this time, according to an Air Accident Investigation Branch Special Bulletin on the event.
That 787 fire at Heathrow: what now?
By Stuart Clarke on 18 July, 2013 in Uncategorised
But it does seem likely that a rather smaller lithium battery might have been part of the fire cause – the one that powers the aircraft’s Emergency Locator Transmitter (ELT), an embedded signalling device that would enable the aircraft to be found if it went missing.
The AAIB has just released two urgent recommendations. The urgency stems from the fact that the fire, which took hold in the cabin ceiling area just ahead of the tail fin, would not extinguish when the fire crews discharged Halon fire extinguishant at it. They had to direct a water hose at the fire to put it out.
The risk is that if such a fire event had occurred during flight, the cabin crew might have been unable to extinguish it, and the structural heat damage visible in the Ethiopian aircraft would have spread more widely, posing a threat to the aircraft’s structural integrity, aircraft systems, and a smoke and fire risk to passengers and cabin crew.
The AAIB wants the US FAA to order the immediate inerting of the ELTs in all 787s, because this device and its integral lithium manganese battery are where the fire originated, and there are no other power or energy sources in that vicinity, the Board says. So although it doesn’t state categorically how the fire began, by process of elimination the AAIB thinks the ELT was involved.
At the time the fire started, the aircraft was completely unattended, no external power was supplied to it, and all the aircraft’s internal power sources were switched off. It was controllers in the Tower that saw the smoke and alerted the crash rescue services.
But the second AAIB recommendation takes the issue well beyond the 787 fleet: it asks the FAA to order a safety review of ALL lithium-powered ELT units in all aeroplanes.
Lithium batteries are a known potential heat source. Although Boeing is the only manufacturer so far to have used lithium batteries in its main battery packs, most manufacturers use smaller lithium units to power systems like emergency cabin lighting or to provide power for the auxiliary power unit starter.
This may be Boeing’s nightmare right now, but it’s going to keep the whole industry awake at night for a while yet.
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