January 28, 2013
Credit: Credit: EPA/NewsCom
More than a week into the grounding of the Boeing 787, a clear path to putting the fleet into the air again still appears to be some way off. And although investors and airlines claim they remain optimistic that Boeing can resolve the issue soon, the reality could be distressingly different.
“This is something we are expecting will not be solved overnight,” says U.S. NTSB Chairman Deborah Hersman. During a Jan. 24 press conference, Hersman confirmed that the lithium-ion battery that burned on a Japan Airlines Boeing 787 on the ramp in Boston experienced thermal runaway and short circuits, though investigators continue to search for contamination or defects that may have set one or other of the problems in motion. “We haven't said if this is cause or effect,” Hersman said. “We know there's something wrong, but we have yet to identify it.”
The NTSB and Japan Transport Safety Board (JTSB) continue to pursue their separate investigations into the Japan Airlines (JAL) and All Nippon Airways (ANA) battery incidents this month that prompted the FAA's Emergency Airworthiness Directive which grounded the 787. Yet, since the last of the 50 in-service aircraft shut down its engines on Jan. 17, conclusive indicators of the problem's cause and how to fix it remain elusive.
JTSB officials have concluded that the ANA battery fire shared similar characteristics to the Jan. 7 JAL fire at Boston but admit they are unsure where to look next for answers. Reporting on its initial findings on Jan. 23, JTSB Chairman Norihiro Goto said that “on the surface, it appears there was no overcharging.” He added that “we are finding it difficult trying to figure out what kind of investigative stance we should take.”
Investigators in Japan have visited GS Yuasa, the Kyoto-based manufacturer of the 787's two 32-volt main lithium-ion batteries, while in the U.S. the NTSB has been studying the burned JAL unit. NTSB has also been working its way through evaluations of other battery-related elements of the electrical system, including the charging system and auxiliary power unit controller.
However, while the search through the ancillary systems for a “smoking gun” remains prudent, initial findings seem to point to the battery itself and the safeguards built in and around it. Thus, the root cause could derive from manufacturing flaws in individual units or problems with systems designed to prevent the battery from over-discharging.
In its latest report on Jan. 24, the NTSB says detailed radiographic inspection using computed tomography (CT) and other techniques revealed thermal damage to all eight cells in the battery from the JAL aircraft. The battery is made up of eight 3.7-volt cells, six of which have so far been scanned and disassembled at the NTSB's Materials Laboratory in Washington. The final two cells were due to be similarly analyzed in the coming days, says the NTSB. Although the implications of the scale of the damage to all the cells remain unclear, it is widely expected that the findings will again implicate the battery rather than the supporting infrastructure.
In the case of the auxiliary power unit (APU) main battery which caught fire in the JAL aircraft, the unit is connected through the large motor power system in which a controller handles the input from the 235-volt alternating current (VAC) starter/generators on the main engines, external power (from the ground) and the battery itself. The forward (main) battery, which is the focus for the ANA investigation, is connected to the electrical system via a 28-volt direct current (VDC)/235-VAC power converter. The charger system was developed by Tucson, Ariz.-based Securaplane, which bills itself as a “pioneer” of lithium battery technology on commercial aircraft.