Boeing faces criticism for shortcomings that contributed to a fire that grounded its Boeing 787 Dreamliners for more than three months last year.
The US National Transportation Safety Board outlined a series of failures by the manufacturer and others in its final report into the battery fire on a Japan Airlines 787 at Logan airport, Boston, in January 2013.
Boeing failed to ensure that the lithium-ion battery was tested under the most severe conditions possible because it made an underlying assumption, which turned out to be wrong, that the effect of an internal short circuit within a battery cell would not cause a fire.
In the event, the battery, made by GS Yuasa, of Japan, short-circuited, resulting in a small fire when flammable materials were ejected outside the battery case. There were no injuries.
Another battery overheated on an All Nippon Airways 787 later the same month, prompting regulators to ground the global fleet until April that year.
Boeing redesigned the battery and charger and designed a steel box to contain fires and vent hot gasses outside the plane.
The manufacturer said it agreed with the NTSB’s conclusion that a short circuit led to the fire.
“We remain confident in the comprehensive improvements made to the 787 battery system following this event, and in the overall performance of the battery system and the safety of the airplane,” Boeing said.
The report also criticised the US Federal Aviation Administration for certifying the battery without subjecting it to sufficiently rigorous testing.
The NTSB identified several concerns during an inspection of GS Yuasa’s facilities, including the possibility of foreign objects interfering with the manufacturing process during welding operations.
The report also concluded that “the test battery was different than the final battery design certified for installation on the airplane”.
The FAA said: “The FAA already has implemented many of the NTSB’s recommendations about modifications in testing, safety standards and design as part of the 2013 certification of the 787’s redesigned battery system.”