Boeing 787 Dreamliner: NTSB details battery fire
A detailed description of a battery fire on board a Boeing 787 Dreamliner has been released by a US regulator but no cause has been specified.
The National Transportation Safety Board (NTSB) is investigating the incident in Boston on 7 January.
In its "interim factual report", released alongside hundreds of pages of related documents, the NTSB said it was still looking into the probable cause.
All 50 Dreamliners in operation have been grounded.Hissing loudly
Minutes after the Boeing 787 aircraft landed at Boston's Logan International Airport from Tokyo's Narita, cleaning staff discovered smoke near a kitchen at the back of the plane, the report said.
A mechanic investigating the area in the electronics bay "found heavy smoke and fire coming from the front of the auxiliary power unit battery case".
There were two distinct flames about three inches in length at the front of the battery case, the report said.
Airport security footage showed smoke coming out of the plane.
An aircraft rescue and fire fighting captain reported the battery was hissing loudly and liquid was flowing down the sides of the battery case.
He received a burn on his neck when, in his words, the battery "exploded".
After repeated attempts to put out the flames, the battery was removed from the aircraft.
The report said the situation was "controlled" one hour and 40 minutes after the initial notification.
Several reasons have been given as to why the lithium ion batteries used in the Dreamliner could emit smoke, including short circuits, however the report said only overcharging would cause it to burn.
In a separate incident on 16 January on board an All Nippon Airways (ANA) flight, smoke was reported coming from the plane's battery but no flames.Fuel-efficient
The ANA plane was forced to make an emergency landing, and that led to the grounding of all Dreamliners in operation.
The Dreamliner is the first plane in the world to use the lithium ion batteries, which are lighter, hold more power and recharge more quickly.
Boeing says the aircraft is 20% more fuel-efficient than similar sized airliners, a selling point for airlines for whom fuel costs are their biggest operational expense.
Airlines that operate Dreamliners have been forced to find alternatives for scheduled flights in their fleets.
Some have said they will seek compensation from Boeing for the losses arising from keeping the Dreamliners grounded.