U.K. Safety Agency Confirms Pinched Battery Wiring Caused Ethiopian 787 Fire

June 18--A report by a U.K. safety agency Wednesday confirms the cause of the fire inside an Ethiopian Airlines 787 Dreamliner parked at Heathrow last July.

A battery inside a small locator beacon was installed incorrectly, with crossed wires pinched between the device case and the coverplate, causing a short circuit.

The update to the ongoing investigation shows that the supplier of the beacon, Honeywell, identified this precise installation problem and the potential for crossed wires six months earlier and modified the assembly instructions to prevent it from happening in the future.

Yet Honeywell did not inspect the devices already in service or even communicate the issue to aircraft operators and manufacturers.

The report suggests that the fact that it was a Dreamliner that caught fire was bad luck for the troubled program, not the fault of Boeing.

At the time of the incident, there were approximately 3,650 identical batteries in service, "fitted to numerous aircraft types." There were a further 2,900 very similar batteries in service on other aircraft.

No previous in-service overheating incidents had occurred.

After the Heathrow fire, mandatory inspections of the locator beacon device on 787s and other aircraft worldwide revealed a total of 28 with battery wires similarly pinched between case and coverplate.

Of those, only nine had exposed the wire and six of those were fully charged -- indicating that the wire had not made contact with the case to create a short circuit.

Of the remaining three devices with trapped and exposed wires, two failed benignly, protected by built-in safety features designed to kick in when overheating occurs.

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U.K. Safety Agency Confirms Pinched Battery Wiring Caused Ethiopian 787 Fire