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Aviation investigators have recommended that regulations governing the use of lithium-ion batteries on aircraft need be updated following the fire onboard a Boeing 787 Dreamliner last year.
A report published by the UK's Air Accidents Investigation Branch (AAIB) yesterday confirms that the cause of a fire onboard an Ethiopian Airlines 787 at Heathrow Airport last July was bad wiring in the lithium-ion battery of the aircraft's emergency beacon.
The report goes on to recommend that the US Federal Aviation Administration (FAA) updates the airworthiness certification process for lithium-ion batteries to take account of how the battery will operate once installed. “The guidance and requirements written in 1995 are now outdated and do not adequately take account of the progress in lithium battery technology and operational feedback over the intervening two decades...” it says.
“...the battery's ability to dissipate heat will depend on the materials, the case, its mounting structure, the ambient temperature in the aircraft and the presence of aircraft insulation. However none of the tests are required to be conducted with the battery installed in its parent equipment, nor with the equipment installed in the aircraft,” it adds.
The fire last year was the latest in a series of lithium-ion battery fires that have plagued Boeing's flagship Dreamliner passenger aircraft since it entered into service in 2011. Prior to the fire last July, lithium-ion batteries that supplied power to the aircraft's electrical systems caught fire on several occasions, leading to the FAA grounding the aircraft until the batteries were fixed.
The root cause of the problems which led to the fire within the Ethiopian Airline's 787's emergency beacon, which was supplied by engineering firm Honeywell, was found to be the wiring which had been trapped under the battery's cover-plate during their manufacture. When the battery short circuited, instead of rapidly depleting as expected, thermal runaway occurred in the battery's cells. The improperly sealed cover-plate also provided a gas path for flames the battery's materials to escape from the beacon into the surrounding aircraft.
Following the incident, all 3,650 affected beacons installed on aircraft were inspected and to date 28 have been found to have improperly installed wiring. Honeywell have subsequently redesigned the beacon and its battery.