Boeing Fix For 787 Problem May Not Require Identification Of Root Cause
Some of the media coverage concerning battery problems on Boeing's 787 Dreamliners makes it sound like months may pass before the planes can fly again. Not so. It may be a long time (if ever) before regulators identify root causes for battery-pack overheating on two Japanese Dreamliners, but the solution Boeing and its suppliers have crafted for the problems does not appear to require definitive isolation of causes.
Boeing's main concern is with assuring the safety of the planes and their passengers, which given the nature of the two heating incidents can be accomplished despite doubts on causes. The fix basically comes down to two steps. First, strengthen barriers between the cells in lithium-ion battery packs so that overheating in one cell cannot spread to the adjacent cells. Second, enclose the whole battery pack in a containment and venting system that precludes combustion by eliminating any oxygen.
The company also will have to figure out what was wrong with the testing methods used six years ago to certify the batteries for flight. That methodology seemed to indicate that on average one battery cell would fail in every ten million hours of flight. Although it was state-of-the-art testing procedure at the time, the incidents with the Japanese jetliners suggest the test findings were wrong. So more robust testing procedures will be needed in the future.
The paradox of the Dreamliner's current status is that it is stuck on the ground because testers can't find anything really wrong with the batteries. By throwing hundreds of engineers and millions of dollars at the problem, the company and regulators have gradually eliminated 90% of the possible causes for battery overheating, and it's possible that one of the five or six items left could eventually provide a "smoking gun." But it's just as likely that the National Transportation Safety Board will never release a formal finding of the probable cause.
What Boeing has done with its proposed fix is to sidestep the issue of root causes by proposing a permanent solution that would assure aircraft safety regardless of what led to the battery anomalies. In other words, the solution would be effective no matter what NTSB and the Federal Aviation Administration eventually discover about the workings of the batteries. FAA hasn't said yet what it thinks of the Boeing approach, but the company and the agency seem to be operating as a team to resolve the problems.
NTSB has been a bit more hotheaded, publicly describing the battery problem in terms that appeared calculated to raise fears. For instance, referring to the spread of overheating from one cell to the next in the same battery pack as a "thermal runaway" event seems to be a deviation from common usage; thermal runaway in this context would normally mean the migration of overheating from the battery to other parts of the plane. Loose use of technical terminology can be a boon to newspaper sales and cable ratings, but it's probably not the best way to conduct a technical investigation.
One takeaway from the Dreamliner investigation is how efforts to maintain the confidentiality of an investigation can distort news coverage. A few big outlets like the New York Times have been careful to not go beyond what is known in reporting the story, but others have indulged in misleading speculation or exaggerated coverage. For instance, the Wall Street Journal contained a story on Thursday about differences between Boeing and its battery supplier that seemed to be greatly overblown. Maybe reporters would be better off waiting until they have real news to report, rather than trying to produce a story about the 787 every day.
