Root cause and added containment question are key priorities as battery strip-down proceeds
While the hunt for the root cause of the 787 battery problems continues, at least one aspect of 's urgent recovery strategy is coming into sharper focus. The company remains adamant in its faith in the current lithium-ion technology and sees no fundamental reason to change its view as the pressure builds to return the airliner to service.
Despite the evidence from theand aircraft incidents in January, the latest signs indicate Boeing believes its best option for recovery is to modify the existing battery. If this remains the case, even after the root causes are known, the questions become: What extra safeguards are required? Will those satisfy the regulatory authorities? And how quickly can they be implemented? Among the modifications being examined by Boeing is a containment system for the 63-lb. battery improved to endure prolonged exposure to fire, as well as additional temperature monitors.
Officially, however, as the batteries continue to be inspected and torn down by the U.S.and Japan Transport Safety Board (JTSB), solutions remain elusive. For Boeing, the specter of certifying a new or replacement battery system and supporting hardware lingers, along with the inevitable lengthy certification effort and cost impact to the program.
Boeing is intent on steering clear of this fate, as indicated by CEO James McNerney during the company's Jan. 30 fourth-quarter results call. “Nothing we've learned yet has told us that we have made the wrong choice on the battery technology,” McNerney said, despite limitations imposed on him by the ongoing, NTSB and JTSB investigations. “We feel good about the battery technology and its fit for the airplane.”
According to airline officials, the grounding caught Boeing completely by surprise. Sources close to the company say top management did not expect the agency to take the step because the FAA was in agreement with earlier design decisions. Even after the initial action was taken, Boeing expected the aircraft to be back in the air after as little as three days. It also requested permission to ferry strandedto a central location to facilitate testing, as there is insufficient equipment—or in some cases none—at the involved airports, but the FAA turned down the request.
Behind the scenes, Boeing is emphasizing to its 787 customers that there are positives to be taken from the JAL and ANA events, which McNerney describes as being “very different” from each other. Beyond the obvious points—the JAL event occurred post-flight on the ramp at Boston, and the ANA incident happened in mid-flight—McNerney is likely referring more specifically to what investigators are learning from each failure. The APU battery on JAL's aircraft caught fire, while the forward-located main battery on ANA's, although badly damaged by burned electrolyte, is not yet confirmed by the JTSB as having caught fire.
According to airline sources, Boeing is saying that the JAL event, for instance, does not in fact show evidence of a classic “thermal runaway,” as described by the NTSB on Jan. 24, but was a more limited event in which only three of the battery's eight cells were involved in a chain reaction. Although the battery was completely gutted in the ensuing blaze, Boeing investigators believe the total damage resulted from long-term burning caused by the initial failure, not a full-scale thermal runaway.
Similarly, 787 operators have been briefed on the sequence of events in the ANA incident which, according to the aircraft maker, showed that the built-in safety systems worked as intended to warn the crew of the battery malfunction and vent smoke from the electronic/electrical equipment bay. The focus in that case is why the precautionary system that is designed to prevent the battery from over-discharging evidently failed.
But with the fleet grounded, and 787s now coming off the production line at a rate of around six per month, Boeing's reassurances could be seen as mere semantics by airlines that have already endured 3-4 years of delays. The two serious failures and the unexpectedly high number of battery changeouts throughout the fleet—more than 100—prior to the groundings reveal a system that was less than robust, at best, and unstable, at worst.
Boeing has no plans to interrupt or slow the 787 production rate, which McNerney confirms is on track to reach seven per month by mid-year and 10 per month by year-end.
“I don't expect to hear anything in the next 3-6 months,“ says the CEO of one major Boeing supplier. In his view, it would be extremely challenging to ramp down production now only to increase rates again within a short period of time. The supply chain would have a hard time handling such fluctuations, he argues. And for Boeing it is probably easier to keep production on pace and put aircraft in storage than to perform constant change management.
Despite the fact that engineers have been pulled off their assignments to deal with the battery situation and consider possible implications for the electrical system, McNerney says this is “not a significant” drain on resources. Because the efforts are focused on the battery, he adds that there has been no chain reaction or knock-on effect to the build-up for the 787-9, final assembly of which is due to start in coming months.
“I can assure that there is a comprehensive root-cause analysis and related series of technical efforts that I am confident will identify the root cause of these incidents. And so confidence in the process, confidence in the right resources, confidence that it's not distracting to the balance of Boeing, and when we know the answer, we'll know the answer, and we'll act on it,” McNerney says.
There are mixed signals as to whether ancillary charging control devices remain prime suspects along with the battery itself. Investigators are trying to determine if the short circuit, in the case of the JAL fire in particular, was caused by an undetected manufacturing flaw or something else, such as a foreign object.
Battery experts confirm to Aviation Week that NTSB testing at the Carderock Div. of the Naval Surface Warfare Center laboratories includes examination for signs of short-circuiting caused by the build-up of a structure inside the battery called a dendrite. These accumulate in lithium batteries, usually through uneven absorption and desorption of lithium ions, and they can penetrate the inner membranes that divide the anode and cathode. The dendrite formations, which can also be triggered by foreign-object particles on the electrode surface, introduce a physical contact between the positive and negative electrodes, thereby generating a short circuit.
Japan Airlines Chairman Masaru Onishi tells Aviation Week that “there must be some kind of modification” to the battery and the electrical system. “System integration must deliver protection against something like a cell failure, so we must find some improvement,” he says. Boeing has been constantly updating operators about the issues, Onishi says, and he believes that, while the manufacturer started with hundreds of possible root causes two weeks ago, “that has now been narrowed down to a short list of potential causes.” He says “some good progress” has been made, allowing Boeing to focus on the remaining options.
Onishi concedes that the impact on the aircraft's image is “an important issue, so we must fix it as soon as possible.” It is difficult to determine how long it will take to find a solution, though, he acknowledges. The operational impact on JAL will be limited because it has just six 787s, and it has seen no revenue loss, as the aircraft have been replaced byand . So far, JAL has not requested compensation for added costs, but Onishi does not rule it out, saying, “maybe at the next stage.”
CEO John Slosar also is confident that “Boeing will figure it out.” Although Cathay has not ordered 787s, the -900s and -1000s it has on order are also designed to use lithium-ion batteries. Slosar says he expects that Airbus is closely watching the battery investigations so as to draw conclusions for its own system.
Read AW&ST's report on the last FAA grounding of a commercial airliner fleet—in 1979— and stay up to date with developments in the Boeing 787 battery investigations in the digital edition of AW&ST on leading tablets and smartphones, or at AviationWeek.com/787