On landing, technicians discovered the battery “venting fluid,” with fluid dripping from the forward vent relief system, the titanium box and pipes Boeing installed after the airplane was grounded in 2013.
Hobart would not answer other questions but the Aviation Herald reported the airplane was in Paris for four days and brought to Denver, where it remained on the ground for another two days before returning to service.
Paul Bergman, a spokesman for Boeing said "the plane experienced a fault with a single cell," adding that it was not a safety of flight issue.
This is not the first Dreamliner battery to go haywire in the three and a half years since the plane was released from its four-month, fleet-wide safety grounding by the Federal Aviation Administration in 2013. That came after battery malfunctions on two Japanese-operated 787s within two weeks of each other destroyed the breadbox sized batteries and the area in which they sat, prompting three safety investigations.
The Dreamliner was only allowed back in the air in April 2013, when Boeing got approval to move the batteries into a housing designed to contain the toxic fumes and high temperature fire that occur when a lithium-ion battery goes into thermal runaway.
The housing did not change the characteristics of the battery and this most recent event on a United flight is a clear sign that it still flies with an undiagnosed and unresolved problem.
In January 2014, a battery cell on another Japan Airlines 787 vented as the plane sat on the ground at Narita Airport. Later that year in October, a Qatar Airways 787 was forced to divert because of a battery malfunction. And while I was told there were two other diversions resulting from batteries going bad in flight in the first 18 months after the plane began flying again, neither Boeing nor the FAA would provide details.
When I asked again today if Boeing would provide a list of battery failures since the resumption of 787 flights, Bergman declined. "More than 2.7 billion revenue miles have been flown by the approximately six hundred 787 Dreamliners currently in service," he said in an email.
Battery failures on those 600 airplanes are only knowable to Boeing because the FAA previously said it does not require notification; not from Boeing not from the Dreamliner's operators because the titanium housing removes the safety threat from thermal runaways.
Battery experts disagree. After the Qatar diversion, Jeff Dahn, a physics professor at Canada's Dalhousie University told me that battery failures are an indication of a problem within the cells.
“Normally they will do nothing unless they are being mechanically abused or electrically abused. Since they are in the box, they are probably not being mechanically abused, so there is something going on with those cells.”
Now that Dreamliner battery failures have been deemed "non-reportable" by aviation safety authorities, it is impossible gauge the size or the scope of the problem and that's how some folks seem to want it. The question is "why?"
(Christine Negroni - Forbes)