Boeing may have to take back in that big sigh of relief it expelled when the Air Accidents Investigation Branch cleared the Dreamliner's two lithium ion back up power batteries from culpability in the fire aboard an Ethiopian 787 at Heathrow last week.
That's because a variation of the same controversial chemistry is used to power the emergency locator transmitter according to Lewis Larsen, a theoretical physicist whose work requires him to have a depth of knowledge about lithium ion batteries.
RESCU406 emergency locator transmitter without a blip of a worry. Along comes Ethiopian Airlines new Queen of Sheba Boeing 787, which has flown all of six months and darned if the ELT and its lithium manganese dioxide battery doesn't wind up in the middle of a fire that rips through approximately eight feet of the top of the airplane. The question Ethiopian and 787 designers have to be asking is, "Why this plane?"
Is it a coincidence that right after Boeing announced it had solved its first flammable battery problem it now may have another? It is worth considering if the Dreamliner's unique features have a role to play. Today Reuters reported that humidity and wiring are getting the attention of investigators in the U.K.. But I'm also pretty darn sure that the nature of the carbon fiber fuselage may also be under scrutiny.
"Advanced batteries with very different chemistries seem to have a marked propensity to misbehave when installed in Boeing 787 Dreamliners," Larsen told me when I called to get his take on the latest installment in the ongoing Dreamliner saga. Larsen was one of many people I interviewed while working on previous stories about the two fire events on Japanese-operated planes. I paid close attention. I was pretty sure I understood that the cobalt oxide flavored battery selected by Boeing for back up power on the Dreamliner was the bad-boy, super-scary formulation, picked because it was fast charging and packed a punch. But more volatile than iron phosphate and the ELT's manganese oxide.
|Investigators examine the Japanese airlines' batteries|
Stay with me here while I explain that the issue with all of these batteries is that during their lifetime they develop teensy-weensy internal structures called dendrites. That's a bad thing because if they get to close to each other the dendrites will arc. They will release a super hot 4,000 to 6,000 degree electrical spark. By way of comparison, the surface of the sun is about 10,000 degrees.
Okay so the blasted thing is hot, get it? That means the heat is sufficient to breaks down the chemical components in the battery and feed on this as fuel along with and anything else in its way all at a temperature that can melt titanium and - apparently ignite a carbon fiber composite airplane fuselage.
This is a shocking scenario to imagine on an airplane in flight. Lest you jump to the conclusion - as I did at first - that Larsen is some too-far-out-there voice of doom, take another look at the damage on the battery in the Japan Airlines Dreamliner that went bad in Boston.
|The battery destroyed in JAL's Dreamliner. Photo courtesy NTSB|
Or going back to the subject of this post, review the photograph of the Ethiopian Queen of Sheba and ask yourself, what kind of fire is this?
Unless one believes that Airbus executives are poking pins into a voodoo Dreamliner doll, you have to wonder of all the airliners flying with the RESCU406, why does it seem to have gone wrong for the first time on a 787?
digital nature (which I wrote about here) and its carbon fiber construction.
The Honeywell RESCU406S was the subject of a Canadian airworthiness directive in 2009 when two of the devices were found to have faulty ground wire connections. The company was given 2 years to replace them. AAIB is reportedly focusing on the possibility of a wiring problem internal to the ELT battery.
But Larsen is intrigued by the possibility that normal airplane vibrations can shake up dendrites and that those vibrations may be different in some way on a composite airplane. This could explain why the service history of the ELT has been so good on aluminum airplanes, but the device acted up pretty quickly on the Dream.
"In theory, some of the random vibrations on the airplane could trigger micro-arcs by resonantly coupling to nanostructures located inside the batteries," he said. "The plane is sitting on the ground, other planes are going around. There's all sorts of acoustic stuff in the air, the plane is like a big tuning fork."
|Lewis Larson photo by Lloyd DeGrane|
For the reasons Larsen suggests, this may not be the incident to dismiss as unrelated to previous battery problems. Quite the opposite, the Ethiopian Airlines fire seems to be pointing right back to the same source, battery technology that is simply not ready to fly.