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Monday June 24, 2019

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New 787 battery incident, notable for all the right reasons

The January 14th Dreamliner incident is just the latest in a string of battery issued that have troubled the new airliner. However, this latest incident is notable for all the right reasons.

JAL's 787, registion JA834J, was undergoing its daily A-check prior at Tokyo Narita airport when maintenance staff saw white smoke rising from the bottom of the fuselage.

The smoke was short lived, but on-board systems indicated a failure of the "Main Battery & Main Battery Charger".

On inspection of the new stainless-steel battery enclosure, engineers found that a pressure relief valve from one battery cell had opened, dispersing electrolyte into the protective casing.

Including this latest event, there have been four seperate incidents involving the 787's main batteries.

The previous three involved damage to the airframe, after fires broke out in the aircraft batteries.

THE FIX

Boeing and the FAA addmitted some deficiencies in the design of the new, high capacity and high voltage batteries. The individual cells were able to impact on each other in an overheat condition, and should thermal runaway occur the casing was unable to contain the resulting fire.

Boeing redesigned the battery internals to prevent issues in one cell spreading to others. They also enclosed the batteries in stainless-steel enclosures, capable of containing even extreme fires. These enclosures vent to the outside air, which explains the smoke event we have seen.

THE RIGHT REASONS

This latest incident is notable for all the right reasons. A single cell within the battery suffered a thermal event, but this was contained and did not spread to the others.

There are 8 cells in each 787 battery.

The battery enclosure also perfomed as designed, safely venting gasses and liquid overboard. Although the underlying battery issues were never addressed, Boeing can be assured their solution is robust.

DESIGN REVIEW

In early 2013 the FAA launched a design review of the electrical systems on-board the 787. They stated they would issue their final report in the Summer of 2013, but as of January 2014 they still have not done so.

The Guardian reports that they now expect to issue the report in March this year, with the caveat that this latest incident might delay proceedings.

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