(Adds detail about safety recommendations)
By Alwyn Scott
NEW YORK, June 18 A fire that scorched the top
of a Boeing Co 787 Dreamliner at London Heathrow airport
last summer was likely caused by faulty wiring in an emergency
rescue beacon that led to "an uncontrolled discharge" from a
lithium-ion battery, the UK aviation safety agency said on
The agency also recommended five steps the U.S. Federal
Aviation Administration could take to ensure greater safety with
lithium batteries on aircraft, echoing comments the U.S.
National Transportation Safety Board made last month.
The battery likely discharged unevenly, causing one of its
cells to deplete more than the other four, then reverse polarity
and absorb energy from the others, the UK Air Accidents
Investigation Branch (AAIB) said in a special report.
"Several tests demonstrated that when a cell failed in this
manner, the heat released caused the failure to cascade to the
remaining four cells," the AAIB said.
Honeywell said it appreciated the AAIB's thoroughness and
noted it had worked with the FAA and Transport Canada on an
airworthiness directive requiring "that all applicable ELT units
are inspected to verify that the error is not present." It
added, "Honeywell is committed to ensuring the safety of all its
products and has implemented a redesign and amended
assembly/installation guidelines for this product."
The July 12, 2013, fire in the emergency locator transmitter
(ELT), made by Honeywell International Inc, burned the
top of the fuselage of the Ethiopian Airlines jet,
taking it out of service for an extended period and renewing
concern about use of lithium-based batteries on aircraft. No one
was injured in the incident and the jet was parked at the time.
Separately, the global fleet of Dreamliners was grounded for
three months last year after two other lithium-ion batteries,
not related to the ELT, burned in two incidents in Japan and the
No one was injured in those incidents, but out of concern
for safety, regulators halted flights while Boeing redesigned
the batteries and the charging system, and created a steel box
to contain a fire.
The AAIB said the FAA should develop better requirements to
certify use of lithium-metal batteries on planes that take
account of current knowledge about how they operate and fail.
It also recommended that the FAA require certification tests
for lithium-metal batteries be carried out with batteries
installed in surrounding equipment, to account for any problems
that could arise from integration.
(Editing by Jonathan Oatis)