The US Federal Aviation Administration (FAA) should re-evaluate the risk of internal short circuits within permanently installed lithium-ion batteries on commercial aircraft, the National Transportation Safety Board (NTSB) says in new recommendations released on 22 May.
The FAA also should improve testing of lithium-ion batteries during the certification process and consult with outside experts on all new technologies being installed on aircraft, the NTSB adds.
The six recommendations are the first proposals for change to come out from the two battery incidents in January 2013 that prompted a worldwide, four-month grounding of the Boeing 787 fleet and an investigation that is still ongoing.
The NTSB is still to complete its final report on the investigation of the 7 January 2013 battery fire on a Japan Airlines 787 at Boston Logan International airport. Japanese safety authorities are also probing the why a similar lithium ion battery overheated a week later on an All Nippon Airways 787 over Japan.
Although the investigations remain ongoing, the NTSB has already concluded that the testing process used by the FAA to approve certification of the 787's lithium-ion batteries supplied by GS Yuasa were inadequate.
The NTSB also discovered that other federal agencies were aware that a nail-penetration test would not conclusively ensure that a failure in one of lithium ion’s cells would not cause a chain reaction in other cells, called a thermal runaway.
The FAA instead relied exclusively on Boeing’s expertise to approve the lithium ion battery. As a result, the FAA should consult a panel of independent experts when considering how to determine the safety of new technologies, the NTSB says.
The FAA also approved Boeing’s solution to the battery crisis in 2013. Rather than switch to a new battery design, the FAA lifted the 787 grounding order after Boeing installed a kit aimed at preventing a thermal runaway event from causing damage to the rest of the aircraft. The battery cells are spaced farther apart and are contained within a stainless steel box with a vent used to channel any escaping fumes directly out of the aircraft.
But the NTSB also urges the FAA to “re-evaluate internal short circuit risk for lithium ion batteries now in-service”.