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27 April 2013

787 Dreamliners return to service

More than three months after being grounded by the FAA and by other aviation authorities around the world due to a pair of battery fire incidents, the 787 is flying once again. While US and Japanese investigations into the causes of the fires continue, the FAA has allowed the 787 to return to service once airlines install a number of required changes to the electrical system. These changes would either reduce or eliminate the likelihood of a battery problem, or would reduce the impact of a problem if it were to occur in the future.

Battery system problems
On January 7th of this year, a JAL 787 that was parked at the gate at Boston's Logan Airport had a battery fire in the aft electronics equipment bay. The fire produced a significant amount of smoke, but only a minor amount of damage. At the time, the aircraft had only a maintenance crew on board. Later that month, on January 16th, an ANA 787 experienced a battery fire in the forward electrical equipment bay while in flight, leading to an unscheduled landing and evacuation of passengers and crew by emergency slides.

During the 787 certification process, Boeing estimated that the battery would have an event that would emit smoke roughly once every 10 million flight hours. The two January 2013 battery smoke events occurred after only about 52,000 flight hours for the worldwide 787 fleet, a frequency that was roughly 190 times the predicted rate.

Electrical system changes
Boeing and the battery manufacturer have made a number of FAA-required changes to the electrical system, primarily to the battery systems that uses lithium ion batteries to power aircraft electronics and other aircraft systems like the auxiliary power unit. The changes are meant to prevent similar battery failures, or to contain the effects should they occur in the future:

  • Redesigned lithium ion battery that features a lower operating temperature
  • Addition of a sealed, stainless steel battery enclosure to help contain smoke and heat from a fire
  • Replacement of the battery chargers.
  • Installation of a venting system that would allow any smoke of fumes from a fire to vent outside of the aircraft.
  • An FAA Airworthiness Directive about the required changes estimated that the costs to implement the changes for the six aircraft covered by the AD (United Airlines 787s) would be about $2.8 million.

Return to service
The first operator to return the aircraft to service was Ethiopian Airlines on April 27, 2013. Other carries with grounded 787s will return their aircraft over the next few months, with Air India and United Airlines likely returning their aircraft. Boeing is sending teams around the world to put those changes in place, and any newly delivered aircraft will incorporate these changes.

Battery fire investigations
Both the NTSB and the JTSB continue to investigate the cause of the battery fires in the US and Japan. On April 23-24, 2013, the NTSB held an investigative hearing involving the FAA, Boeing, and the battery manufacturers. While the NTSB concluded that the original battery certification tests were inadequate, there was no determination of the probable cause of the battery fire in Boston. It is likely that it may be several months before the NTSb or the JTSB reach a conclusion about the cause of the fire.

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