Investigators believe the blaze started in an emergency beacon, which showed some indications of disruption to the battery cells
Investigators have traced the source of a fire on an Ethiopian Airlines 787 Dreamliner at Heathrow Airport to an emergency locator transmitter (ELT).
Air accident investigators said they believed the blaze may have started in the emergency beacon’s lithium manganese battery which could have overheated or short circuited, or an external short circuit within the ELT.
The team from the UK’s Air Accidents Investigation Branch (AAIB) said detailed examination of the ELT had shown some indications of disruption to the battery cells.
The report said: “It is not clear however, whether the combustion in the area of the ELT was initiated by a release of energy within the batteries or by an external mechanism such as an electrical short, In the case of an electrical short, the same batteries could provide the energy for an ignition and suffer damage in the subsequent fire.”
It continued: “The history of this ELT product line indicated that a thermal event is extremely rare.
“However, large transport aircraft do not typically carry the means of fire detection or suppression in the space above the cabin ceilings and had this event occurred in-flight it could pose a significant safety concern and raise challenges for the cabin crew in tackling the resulting fire.”
The report said investigations would continue into what triggered the fire in the emergency beacon.
Confirming their findings on Thursday, they called on the Federal Aviation Authority to temporarily deactivate all ELTs on 787 aircraft until full airworthiness tests are carried out.
They also urged for a review of other similar emergency beacons, manufactured by US electronics firm Honeywell, which has also been asked to join the probe.
An ELT is a device used to give emergency services and authorities an accurate location for a plane following a crash.
Last Friday’s blaze caused serious damage to parts of the 787 aircraft’s fuselage, but luckily no one was on board at the time and there were no injuries.
However, thousands of passengers faced travel chaos after the aircraft, which has been plagued with problems since its launch, caught fire while on a remote parking stand shortly after 4.30pm.
Runways were closed to all flights for an hour and a half while emergency crews dealt with the blaze, which caused diversions and long delays for passengers
Boeing said in a statement: “The safety of passengers and crew members who fly aboard Boeing airplanes is our highest priority.
“As a party to the investigation, Boeing supports the two recommendations from the UK Air Accidents Investigation Branch (AAIB), which we think are reasonable precautionary measures to take as the investigation proceeds.
“We are working proactively to support the regulatory authorities in taking appropriate action in response to these recommendations, in coordination with our customers, suppliers, and other commercial airplane manufacturers.
“We are confident the 787 is safe and we stand behind its overall integrity.”
This problem is separate to the main electrical power supply battery faults, which led to the grounding of 787 aircraft worldwide earlier this year after batteries overheated on two Japanese jets in quick succession in January.
The action led to delivery delays which caused Thomson Airways to scrap plans to use the ultra-green aircraft in May and June. The carrier finally began Dreamliner services earlier this month.
British Airways has taken delivery of the first of its 24 Dreamliners, while Virgin Atlantic is due to receive the first of its 16 Dreamliners in September next year.
Tags: Boeing 787, Ethiopian Airlines, Heathrow