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NTSB investigation into Dreamliner Li-ion fire finds signs of short circuiting, thermal runaway

24 January 2013

Ntsb0
Damaged electrode with sign of internal short circuit from the 787 Li-ion battery. Source: NTSB. Click to enlarge.

At a briefing on the progress in the investigation of the Li-ion battery fire on-board a JAL Boeing 787 at Logan Airpot in Boston (earlier post), NTSB Chairman Deborah Hersman reported that the investigating team had found signs of electrical short circuiting and thermal runaway in the cells. The NTSB is working to determine the cause.

The next steps in what appears will be a lengthy investigation will be to complete the in-house laboratory examinations; conduct examinations and testing of exemplar batteries; and to synthesize lab examination findings with fire forensics and aviation systems investigation.

Ntsb-cellct
Ntsb-cell6
Example of a cell CT scan. Source: NTSB. Click to enlarge.   CT scan of Cell 6. Source: NTSB. Click to enlarge.

So far, NTSB has performed an exam and teardown of the JAL battery at its Materials Laboratory. Boeing and its various suppliers have also performed component exam and teardowns:

  • Securaplane Technologies, Battery Charger Unit and Start Power Unit
  • United Technology Aerospace Systems, APU Controller
  • Boeing, Two General Purpose Modules
  • Kanto Aircraft Instrument, Battery Monitoring Unit

The battery itself comprises 8 GS Yuasa prismatic Li-ion cells each with a nominal capacity of 75 Ah, with a nominal voltage of 3.7 V. So far, NTSB has performed:

  • CT scan of the entire assembly.
  • Cell 1: CT scan
  • Cell 2: disassembly
  • Cell 3: CT scan
  • Cell 4: CT scan
  • Cell 5: CT scan, disassembly, scanning electron microscopy, energy dispersive electroscopy
  • Cell 6: CT scan, disassembly
  • Cell 7: CT scan, disassembly, SEM
  • Cell 8: disassembly
Ntsb-apu
Source: NTSB. Click to enlarge.

Boeing issued a statement after the update, welcoming the progress.

In order to ensure the integrity of the process and in adherence to international protocols that govern safety investigations, we are not permitted to comment directly on the ongoing investigations. Boeing is eager to see both investigative groups continue their work and determine the cause of these events, and we support their thorough resolution.

—Boeing statement

January 24, 2013 in Aviation, Batteries | Permalink | Comments (33) | TrackBack (0)

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Comments

Internal short circuiting, cause or effect? Bad separator material or excessive voltage or current leading to separator failure?

The claim is that the batteries were not overcharged, but how do we know this?  Log data from the charge controllers?  Do we know the software was reporting the voltage and SOC correctly?

This needs to be checked out forensically, because after Stuxnet we cannot discount sabotage in anything with loadable software that has come in contact with an Internet-connected development system.

Yuasa's cylindricity tolerance for prismatic cells seems to be a bit generous.

Bad cell - use good cell - backup the backup.

Why Boeing didn't test those batteries more rigorously during the 3+ years the 787s were delayed?

Somebody didn't do the job right?

How can they get anything out of that charred mess?

Building a potential time bomb into a passenger airliner is beyond comprehension. In the aircraft industry it is generally mandatory to use fail safe design rules. Clearly this was not the case in this instance.

It reminds one of the DC-10 case where the failure of the bagage door locks took out the main cabin passenger floor at altitude which in turn severed the empenage control cables. After a thorough NTSB investigation it was determined that managers refused to listen to advice of engineers because the roll out of the plane would have been behind schedule. Unfortunately, unlucky passengers paid the ultimate price in losing their lives.

I wonder who the culprit will be for the 787 fiasco?

Take the batteries out of there even if it means an extra 60 lbs. of added weight and go fly the friendly skies.

NTSB? Are these the same goofs that crash tested the Volt, then disconnected the lead acid battery and drained the gasoline, but left the high voltage battery charged? You remember, then a week later one of the several Volts they crash tested started on fire and they made a big stink about it like it was a dangerous technology. Maybe that was NHTSA, but they're the same team right? They can act like they are the experts but many of us know better. What the hell do they know about batteries, and if they knew anything about batteries why would they approve a liquid electrolyte cobalt oxide cathode battery for an airline application. The talking heads in suits have assumed control so no rational decision will ever be made again.

Are these comments coming from the same people that complain that new technology to save weight is ignored by industry?

A 787 is 502,500 pounds, I don't think an extra 10 pounds for batteries is going to make a big difference.

Ten pounds of batteries is ten pounds of cargo lost, or a substantial fraction of a pound of fuel to haul it on each leg.  These savings add up.

Let's not forget that this design was probably locked in many years ago with this specific cell. Similar cells have been used for many years successfully in satellites and rockets.

Every system on an airplane is designed for minimum practical weight – because they must fly.

When a problem occurs, someone can always say that the system involved could have been more robust if it were designed 10 pounds heavier – and maybe they do design main battle tanks that way.

But do NOT fly on a passenger airliner; they are all potential time bombs filled with electrical devices and fuel.

After the A300 - Fight 587 out of New York City crashed in Queens on November 12, 2001 killing all 260 people on board and five on the ground, they attributed the crash to overuse of the rudder in response to wake turbulence from a preceding Boeing 747.

Until retired in August 2009, these A300s continued in service with a rudder that was very sensitive (with no force feedback) and a vertical stabilizer that COULD NOT withstand “lock-to-lock” actuation at final segment climb speed.

Despite ten previous recorded incidents with A300 tail fins; the NTSB concluded that the vertical stabilizer's structural performance was consistent with design specifications and had failed because it had been stressed beyond its design limits.

At this time it is probably cheaper for Boeing to do a re-certification of the aircraft using a more conservative Ni-MH battery sets.

This way they can restart test fight and people can see there is light at the end of the tunnel.

Hard to say, Tex.

Both Boeing and Airbus are trying to retain all of their options.

Unlike the FAA, the NTSB has a reputation for being estranged from practicality and common sense.

The NTSB does investigations; it's the FAA's job to issue airworthiness directives (ADs).  When the change to the 787 comes along the pike, it'll be pursuant to an AD.

The point was if they used a safer battery chemistry resulting in a 5-10 pound increase for a box with the same Wh capacity, the added safety with 5 pounds more considering the 500,000 weight of the plane would be acceptable.

No, the point is that time flows from the past to the present.
1A. They designed the battery
1B. The design included various reliability, longevity, failure rate, failure mode and failure effect studies (hazard analyses).

2.- They concluded that the battery met all requirements (with required Boeing and FAA MARGINS) for performance, reliability and safety; and that it will NOT have a safety or performance problem in the field.

3-. They have a problem in the field.

They should buy boeing 777 instead, it's almost the same thing but with less fancy problems.

TT, the discussion was about the battery pack weight and safety. 5 pounds more weight for a safer battery chemistry makes sense...to most people.

Except you can use safer battery chemistry, LiFePO4, at the same weight. Because this was an older version of the LiCo chemistry the specific energy density is about the same as today's LiFePO4. Change the operating voltage parameters for the system slightly and stick in a bunch of LiFePO4 cells. Or just have Tesla design the battery since they have experience with LiCo and variants in large packs that don't catch fire. Using newer versions of LiCo Tesla could increase the energy density and safety at the same time.

That IS the point, there are safer batteries. Even if those safer batteries weigh a bit more, the safety is worth it. I believe most rational people would agree.

The problem isn't getting LiFePO4 cells in the right quantity and form factor.  The problem is finding a manufacturer willing to devote enough engineering time to document everything to FAA standards.  I doubt that the 787 market is big enough to be very attractive, and the battery makers already have their best people working on other things.  Taking on a major distraction could mean falling behind in the race against the other battery-makers, and that means serious damage to the company.

@ Engineer-Poet

"that means serious damage to the company."

So damage to the company takes precedence over safety.

Better stick to poetry than engineering.

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