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Dreamliner investigators shift focus

By control on January 28, 2013

The inspection teams investigating the B787 Dreamliner’s recent spate of technical incidents now suspect the problems do not lie directly with the aircraft’s lithium-ion batteries.

U.S. and Japanese officials, working jointly to identify the fault after all 50 of the 787s currently in service were grounded, are now looking instead at a system that monitors the batteries’ charging levels and temperature.
A spokesman for Japan’s transport ministry reported “no major quality or technical problem" with the batteries themselves, but said, "We are looking into affiliated parts makers. We are looking into possibilities."

Two aircraft, operated by Japan Airlines and All Nippon Airways, suffered smoke damage in the same week as a result of their batteries overheating.

Analysts said the problem was clearly electrical, but the longer it took safety officials to pin down the exact cause, the longer the 787 would be out of service–with potential impact on future deliveries.

Comments

Submitted by Kafantaris on
If the likely 787 culprit is the system that monitors the battery voltage, charging and temperature, then redundancy is our answer. Redundancy is what put us on the moon and is what affords us the foreseeable reliability of our Internet servers. Indeed, redundancy is allover the 787, though apparently not adequate for its lithium battery housekeeping system. Now that we know more about thermal runaway -- that self-fueled overheating of lithium batteries -- vigilant monitoring is our answer and redundancy is the true and tried solution. This is actually an easy fix and Boeing should be working on it even as the inspectors are finishing up their work.

Submitted by Charlie K on
Li battery cells have three important voltage levels. Fully charged (do not exceed) Storage or partially charged (The battery is not expected to be used immediately, and can be safely stored at this charge level) Discharged (Around 20-30% charge remains) Lower voltage or charge level can cause damage) A failure related question might be - - - What charge level/voltage existed before and during the battery failure? In the case of the on ramp failure, was the battery idle, being discharged, or charged? I'd assume without any other information that the in flight battery failure occurred while the battery was in use, and likely being charged by the planes electrical system. Do temperature sensors exist inside the cells? It does not look like that's the case. The delay in sensing internal cell temperature caused by heat transfer to an external sensor may contribute to the problem, by allowing the cell internal temperature to go too high before any possible remedial actions are started.

Submitted by rbp on
I hope Kafantaris is correct, and the battery charging and temperature monitoring systems are easily modified systems to eliminate these problems. However, one wonders why this problem didn't appear in the extensive ground and flight test programs.

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