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Secondary Emissions

Dreamliners Shouldn’t Smoke

(Update, January 16:  Aviation Week reported temporary grounding of part of the Japanese 787 fleet yesterday: ". . . reports of a battery malfunction being detected on the engine indication and crew alerting system (EICAS) . . . .   ANA s. . . expects to update the situation within the next few hours. JAL is also reportedly suspending its 787 flights."

The story identifies this battery.  It is made by GS Yuasa, it is "lithium-ion," there are two on each aircraft batteries, and they are are part of "the Thales-supplied electrical power conversion system . . . ." Extrapolating from previous reports the battery in the Logan event is used either to cold-start or back-up the Auxiliary Power Unit (APU), which provides ships power before the main engines are started.

Note that in this case, the problem seems to be a false-positive indication of a battery malufnction.  In automotive terms, one might say the "check-engine" light came on.  Just what a pilot does not want to see when he or she is halfway across the Pacific Ocean.)

[Here's where my comments from January 8 start:]

It’s Tuesday, January 8, and the newspapers are reporting an electrical fire in an empty JAL 787 Dreamliner at Logan. Cleaning crews reported smoke in the main cabin and the cause seems to have been an overheated backup battery for use when ships power is unavailable. (Updated, January 11. The New York Times says the FAA will undertake a further design review in the light of other recent incidents.  Meanwhile the commercial fleet of 777 and 787s will continue flying.)  The chilling part of the story (until you read to the end) is the mention of windshield cracks, which call up memories of the deHaviland Comet.  But then the Times says the cracks are in the topmost layer of a 5-layer sandwich and they're not structural, so never mind those mental images of the scene from the movie Goldfinger with people being sucked out the aircraft window.

[Originally, I said, referring to news stories of a week ago]:

. . . the battery fire, [the one at Logan] which is is the only thing I've read about that looks like a real worry, I’d like to think that would have had a fusible link as a last line of defense. But it’s hard to track down what the FAA might have said about that.  As a former aircraft owner (Taylorcraft, Stinson, 172, Challenger, PA26-235), I’m aware of Advisory circular 43-13-2B: Acceptable Techniques, Methods and Practices, Aircraft alterations, so I took a look in there. No joy.  Fuses and breakers go where the Certificate of Airworthiness says they should go.  But no doubt there’s a tome somewhere that has something to say about it. 

In any event, the incident reminded me of a conversation I had with an old time engineer when I was fresh out of school and working at Garrett AiResearch in the mid-1960s. (He was lead on some electromechanical control-actuation systems for the C5-A and I was “managing” the contractual engineering data, which primarily meant qualification testing.

Essentially, he warned me never to fly in a new aircraft type until it had several years of commercial service logged.  Case in point was the 747, which, as far as I know, was the first to have a common bus for controlling entertainment, overhead lighting, and such passenger amenities.  Sure enough, reports started coming in about seat-arm controls turning on lights across the aisle and things like that.  Nothing affecting safety of flight, but the sort of thing to make a thinking passenger nervous.

The big deal about the Dreamliner is its use of composites, which seems to be an issue with some people.  Never mind that the use of composites goes back to the F-111, which I also did some paper-shuffling on at Garrett.  (Aileron jackscrews, as it happens; I was trapped with a bunch of mechanical engineers for a while there.)  The boron-epoxy bits held up quite well there, and we’ve been using them for 43 years now.  By the way, there’s an interesting book (published 2001) that you can download here

(It’s a search result; I Googled C-17 and composite.)

Which brings us no closer to an explanation of the smoking battery at Logan.  Next week we’ll know more.

TAGS: News
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