Late last week, we learned that in all likelihood, it will be several months before the FAA and other aviation regulators allow the Boeing Dreamliner to fly again. Now a front-page article (below the fold) in today's NYT reveals just how serious the problems were with the Dreamliner's lithium-ion battery.
The biggest buyer of Dreamliners, Japan's All Nippon Airways, revealed yesterday that it had to replace 10 of the batteries in December.
In five of the 10 replacements, All Nippon said that the main battery had showed an unexpectedly low charge. An unexpected drop in a 787’s main battery also occurred on the All Nippon flight that had to make an emergency landing in Japan on Jan. 16.
The airline also revealed that in three instances, the main battery failed to operate normally and had to be replaced along with the charger. In other cases, one battery showed an error reading and another, used to start the auxiliary power unit, failed. All the events occurred from May to December of last year. The main battery on the plane that made the emergency landing was returned to its maker, GS Yuasa, and that 10 other batteries involved in mishaps were sent to the airline’s maintenance department.
While ANA notified Boeing of the battery replacements, it wasn't required to tell regulators because it wasn't considered a safety issue at the time.
The NYT piece also reveals that Boeing was unwilling to redesign the batteries even after evidence surfaced that they were prone to overheating.
In a little-noticed test in 2010, the F.A.A. found that the kind of lithium-ion chemistry that Boeing planned to use — lithium cobalt — was the most flammable of several possible types. The test found that batteries of that type provided the most power, but could also overheat more quickly.
In 2011, a lithium-ion battery on a Cessna business jet started smoking while it was being charged, prompting Cessna to switch to traditional nickel-cadmium batteries.
The FAA test revealed that when lithium-ion batteries overheat, they're more prone to to dangerous jumps in temperature and pressure. The Cessna battery had dropped to only 5 percent of its power. At that level, the battery can't accept a charge, and trying to recharge it can cause it to catch fire.
With the NTSB no closer to finding out why these batteries have been such a bugbear, there's already talk that Boeing may have to go back to traditional NiCad batteries to restore confidence in the planes. If that were to happen, it would mean months of reengineering the plane, as well as the usual process of regulatory approval.