Boeing works to fireproof its 787 batteries (pictures)
With its Dreamliners grounded after a pair of fires, Boeing has a plan for a comprehensive set of safety improvements to its lithium ion batteries.
Boeing 787 in JAL livery
Two months ago, the Federal Aviation Administration ordered airlines to ground their Boeing 787 Dreamliners because of the "potential battery fire risk" from the airplane's onboard lithium ion batteries. The FAA's action came after a small fire aboard a Japan Airlines 787 on the ground at Boston's Logan International Airport was traced to a battery pack in that plane's auxiliary power unit, as well as a separate incident that forced the evacuation of an All Nippon Airways 787 in Japan.
Today Boeing announced today that it has commenced production on what it calls comprehensive improvements to the safety features of the Dreamliner's lithium ion batteries and said that it could be ready to proceed witih initial installation within the next few weeks. It is also building new enclosures for 787 batteries that could be be installed in airplanes in the weeks ahead.
This photo from March 2012 shows a Japan Airlines 787 taxiing towards the runway at Paine Field in Everett, Wash.
Matt Fox, a materials engineer with the National Transportation Safety Board, examines the casing from the battery involved in the JAL Boeing 787 fire in Boston. Last week, the NTSB issued an interim report on that incident, in which it said heavy smoke and fire were discovered coming from the front of the battery case of the aircraft's auxiliary power unit (APU).
The APU battery contains eight lithium-ion cells. The NTSB's examination of the battery's external casing showed that the right side of the case had the most extensive damage. Most of the cells were found to be electrically short-circuited.
This is one of several views that Boeing has now released of its new 787 battery enclosure, which the company says adds another layer of protection and eliminates the potential for fire.
Boeing today described its "comprehensive set of improvements" to the lithium ion batteries this way, in part:
"Changes inside the battery will help to reduce the chances of a battery fault developing and help to further isolate any fault that does occur so that it won't cause issues with other parts of the battery.
"To better insulate each of the cells in the battery from one another and from the battery box, two kinds of insulation will be added. An electrical insulator is being wrapped around each battery cell to electrically isolate cells from each other and from the battery case, even in the event of a failure. Electrical and thermal insulation installed above, below and between the cells will help keep the heat of the cells from impacting each other."
Here's another view of the new 787 battery enclosure, shown within electrical equipment rack. Boeing's explanation of the changes continues this way:
"Wire sleeving and the wiring inside the battery will be upgraded to be more resistant to heat and chafing and new fasteners will attach the metallic bars that connect the eight cells of the battery. These fasteners include a locking mechanism.
"Finally, a set of changes is being made to the battery case that contains the battery cells and the battery management unit. Small holes at the bottom will allow moisture to drain away from the battery and larger holes on the sides will allow a failed battery to vent with less impact to other parts of the battery."
The dark object to the right is the cover for the new battery enclosure. It's made of 1/8-inch stainless steel, the material that will be used for the entire enclosure designed to isolate the battery from the rest of the equipment in the electronic equipment bays. "The addition of the new enclosure isolates the battery so that even if all the cells vent, there is no fire in the enclosure and there is no significant impact to the airplane," said said Mike Sinnett, vice president and chief project engineer for Boeing's 787 program, in a statement.
As part of its investigation, the National Transportation Safety Board last month offered up this photo of an undamaged Boeing 787 auxiliary power unit battery (which weighs about 63 pounds and measures 19 inches by 13 inches by 10 inches), in contrast to ...