Boeing says it remains "very confident" in the lithium-ion batteries used on the 787 despite a continuing investigation of a fire that grounded a Japan Airlines aircraft in Boston earlier this week.
The 32V eight-cell battery had accumulated 1.3 million flight hours across the fleet before a unit exploded on the ground at Boston Logan International airport, igniting a small fire that caused severe damage to the battery compartment, says Mike Sinnett, Boeing's 787 vice president and chief project engineer.
Boeing called a press conference on 9 January as public concerns about the 787 spread after the battery problem added to a series of electrical glitches plaguing the fleet in recent weeks. But Sinnett could not address the incident in Boston directly because it remains an active investigation by the National Transportation Safety Board.
The lithium-ion chemistry was selected to replace pneumatics as a means to start the auxiliary power unit under certain conditions because it is the only kind of battery that can supply sufficient power and be rapidly recharged, Sinnett says.
Lithium-ion batteries, however, can ignite fires if they are over-charged or are asked to supply too much energy. As a result, Boeing took several precautions to prevent fires in such circumstances, and to contain any fires that may start.
Asked whether Boeing could replace lithium-ion as a power source, Sinnett says Boeing has not looked at alternatives. "Knowing what I know now I'd make the same choice," he adds.
Boeing also provided the first update on its ongoing internal investigation of several publicized electrical system failures reported by United Airlines and Qatar Airways last month.
The electrical failures have been traced to a single batch of circuit boards manufactured by a sub-tier supplier, Sinnett says. However, Boeing is still seeking to determine a root cause for the failures that shut down one of six onboard generators, Sinnett says.
He adds that the 787 is certificated to fly for 5h using only one of the six generators, so the loss of only one is not a safety issue.
Overall, Sinnett still defends the 787 in-service record after delivering 50 aircraft over the last 15 months. Sinnett compares the 787 favourably to the introduction of the 777 in 1995, when the twin-aisle jet achieved a 97.9% dispatch reliability rate after one year in service.
"We're probably on the low side of that number. There's no metrics that are screaming at me that we've got a problem," he says.