Boeing 787s grounded by Japan

[383LQ4SS]

Originally Posted by Fitter

My bad, it seems it does have an hydraulic pump, should be two I'd think, on the engine. In my defence in development world we only run with hyds when the test calls for them specifically and I only ran one Trent 1000 during training. My apologies for if I misled anyone.

No worries. This aircraft is quite different for sure. The schematic that show the dual ECS systems each driven by two electric motors is quite a shock to me. The amount of horsepower/electric current needed to maintain pressure and condition the air properly must be staggering. In the schematic it also shows each engine with dual starter/gens and the APU with dual starter/gens. That is one electrically HUNGRY aircraft. Basically a flying power station..lol.

The electric system is very elaborate...including 270 VDC systems...yes that's DC.
See page 9 on this link:
http://www.boeing.com/commercial/aer...7_article2.pdf

Quote:

. the ±270 VDc system is
supplied by four auto*transformer*rectifier units
that convert 235 VAc power to ±270 VDc. the
±270 VDc system supports a handful of large*
rated adjustable speed motors required for the
no*bleed architecture. these include cabin
pressurization compressor motors, ram air fan
motors, the nitrogen*generation*system compressor
used for fuel*tank inerting, and large hydraulic
pump motors.

I sincerely hope Boeing has done their homework. This is drastically different. I do believe it is better....on paper. But with 5000 psi hydraulics and all these motors and lithium batteries only time will tell.

Amazing feat of engineering.

[Puppycow]

Here's an article on the maker of batteries. They were unprofitable even before this incident (or at least the lithium-ion battery part of their business was). This may kill them I'm afraid. Unless they find out that it wasn't the batteries' fault after all.

Boeing 787 Deal Puts Battery Maker GS Yuasa in Spotlight

Quote:

For GS Yuasa Corp. (6674), winning the deal to supply Boeing (BA) Co. offered the chance to make its first profit from selling lithium-ion batteries. The recent grounding of the 787 fleet on concerns about battery safety means the company’s losses on the technology will likely widen.

In the year ended March 2012, GS Yuasa’s lithium-ion batteries business had an operating loss of 3.26 billion yen ($36 million), compared with a 1.27 billion-yen loss a year earlier, according to the company’s annual report. The company spent 30 billion yen, or 75 percent of its total capital investments, on the segment last year, according to its website.

GS Yuasa’s multi-year, multi-million dollar contract, announced in June 2005, to supply its batteries to Thales SA (HO) for the electrical system of the 787 was an opportunity to offset losses from sales to carmakers. While GS Yuasa announced in 2009 that lithium-ion batteries for vehicles will become a core business for the company, the battery maker since then hasn’t turned the technology into profit.

“They had been hoping to make up for the lack of sales to carmakers by selling to Boeing,” said Jun Yamaguchi, a Credit Suisse AG analyst in Tokyo. “Any inability to sell in the aviation market is going to make the lithium-ion battery business even more unprofitable for GS Yuasa.”

[383LQ4SS]

new report now claiming there is evidence at least one of the batteries was not overcharged.

http://www.cnn.com/2013/01/21/travel...html?hpt=hp_t3

Quote:

The examination of the Boston plane's flight recorder data indicated the APU battery did not exceed its designed voltage of 32 volts, according to Sunday's NTSB statement. It didn't appear to be overcharged, which might overheat the unit and cause a fire. But experts pointed out to CNN that there was no mention in the statement about how quickly the JAL 787 battery was discharging.

It also states in the article:

Quote:

Boeing is using the lithium-ion batteries to electronically assist some of the functions that were previously performed using hydraulics. A lighter plane is more fuel efficient, which is one of the 787's main selling points.

I have no clue if this is truly accurate. And it could also mean several things. On one hand they continuously claim this is the APU battery, which typically would mean its primary job is to start the APU. But the above statement could be true as well. If the battery is used in the fashion outlined above...that typically means the battery is tapped to supplement power during momentary high current demands. Say...during landing gear retraction. Since all hydraulics are now run from electric motors...I could see that.
So it may be possible that the battery is used to start the APU as well as act as a buffer during momentary high demand functions in flight. However until I see better sources it will be difficult to get an accurate grasp of the exact nature that particular battery is used on this new fangled aireoplane.

[rwguinn]

My understanding is that the battery IS the APU--there is no turbine running systems when the engines are not running.

[383LQ4SS]

Originally Posted by rwguinn

My understanding is that the battery IS the APU--there is no turbine running systems when the engines are not running.

See thats where definitions get mixed up in the media. The term APU is mainly used for the small turbine that drives generators and/or provide limited bleed air and hydraulics. The APU battery would typically be the battery that starts that small turbine.
A particular batteries use is usually indicated by the word accompanying it.

Main batteries
Back up batteries
Emergency batteries
standby gyro battery
emergency lighting batteries

An APU could be a battery its self since a battery is a source of auxiliary power and any manufacturer could label it how they want to.
The term APU is used almost exclusively to describe the small turbine engine. That terminology is so typical that wiki makes no mention of alternate uses.
http://en.wikipedia.org/wiki/Auxiliary_power_unit

Also..the rudimentary schematic in my previous links show a battery primarily connected to the APU and it also shows it connected to main bus. However this schematic is almost certainly wrong or extremely limited. It seems to me it is very likely there are more batteries installed on this aircraft.
IMO that battery is way too small to be effective in much beyond the normal duties of supplying power during large momentary loads such as APU or engine start or supplementing power momentarily when one or more of the 787s very large electric motors has a large demand.

Not saying it couldn't have a drastically different role and terminology than traditional aircraft. It certainly could. I just haven't seen anything yet to indicate or verify that.

ETA: also...APU's are typically shutdown after take off. So on a typical aircraft....the battery provides the massive load to start the APU. Once the APU is online it has generators that power systems. Then when its time to start main engines (that have starter/gens as the 787 does) the APU gen provides power along with a battery to start the main engines. When the main engines are up and running...the dual stater/gens provide all power for all ships operation. The APU on some aircraft is typically left on until after take off as an emergency back up. The APU will typically be secured at some time shortly after take-off. The APU will be restarted in the air prior to landing again to provide emergency back up. So yes...during cruise the APU is typically shut down and only turbines running are the main engines which should be providing 100% of electrical power to systems.....including recharging batteries.

[383LQ4SS]

From the article posted earlier regarding the "no bleed architecture"

Quote:

the power source for Apu starting may be
the airplane battery, a ground power source,
or an engine*driven generator. the power source
for engine starting may be the Apu generators,
engine*driven generators on the opposite side
engine, or two forward 115 VAc ground power
sources. the aft external power receptacles may
be used for a faster start, if desired.

So it looks like the APU must be started to provide power for main engine start. And the APU starts primarily by the main battery. Although for most starts on commercial airliners a GPU or ground power unit will be hooked up for start. This tends to save wear and tear on batteries.

The interaction of particular airports GPU's should be looked at as well. Sometimes a common link between failing components is a GPU that is AFU at a particular location. We have had GPUs take out many electronic components in the past prior to discovering a problem with it.

[LTC8K6]

There are two main batteries. The APU start battery, and a main battery. Both batteries are primarily used for backup power. They can be used to start the APU and start the main engines, but that would be unusual. Ground power would normally be used. They can also power other things in an emergency, such as some flight instruments. They are not big enough to supply power for very long. No battery would be.

The 787 has a massive turbine powered APU for ground and backup power. The 787 can be dispatched with the APU inoperative, if necessary. It doesn't really need it to fly, even on ETOPS flights.

Each 787 engine has 2 generators, and the APU has 2 generators, making a total of 6. There is a lot of redundant power generating capability.

Including a backup RAT.

Quote:

In the case of the 787, two 32-volt lithium-ion primary batteries provide power as key elements of the aircraft's more-electric architecture. The main battery, located forward in the electric/electronic (E/E) equipment bay below the cabin floor by the front passenger doors, provides power for aircraft start-up, ground operations such as refueling and towing, and acts as backup power for the electrically actuated brake system. It can also assist the second battery, located in the aft E/E bay, in starting up the auxiliary power unit (APU) and, in the event of a power failure, energizes essential flight instruments in the flight deck until the drop-down ram air turbine spools up.

The battery that caught fire on the Japan Airlines 787 in Boston was the second main battery. This unit's primary purpose is to electrically start the APU when neither of the engines is running and the aircraft is not connected to external ground power. In this case, the battery energizes the righthand of the two starter/generators connected to the APU. The aft battery also provides another minor role, namely to power navigation lights during battery-only towing operations.

http://www.aviationweek.com/Article....p22-537845.xml

[LTC8K6]

The 777 also has 2 generators per engine, and it can also be dispatched with it's APU inoperative.

The 747-400 series has an APU, but it's not expected that it would ever be used in flight. I have read that there is no normal in-flight start procedure for the 744's APU. The 744 has 4 engines, of course. So, it has 4 generators. In addition, the 744's engines are capable of windmilling and continuing to supply electrical and hydraulic power even if they quit running.

[rwguinn]

I stand corrected.
Must have been confused in that the APU is not used in flight...

[383LQ4SS]

Originally Posted by LTC8K6

There are two main batteries. The APU start battery, and a main battery. Both batteries are primarily used for backup power. They can be used to start the APU and start the main engines, but that would be unusual. Ground power would normally be used. They can also power other things in an emergency, such as some flight instruments. They are not big enough to supply power for very long. No battery would be.

The 787 has a massive turbine powered APU for ground and backup power. The 787 can be dispatched with the APU inoperative, if necessary. It doesn't really need it to fly, even on ETOPS flights.

Each 787 engine has 2 generators, and the APU has 2 generators, making a total of 6. There is a lot of redundant power generating capability.

Including a backup RAT.


http://www.aviationweek.com/Article....p22-537845.xml

Now that makes everything quite clear. So this is the APU battery. And when we say APU battery we mean the battery that primarily there to start the APU when needed and then is recharged after APU start. This is a fairly standard configuration for aircraft with starter/gens on APU and engines.
But we also now know that according to FDR info the APU battery did not see an over voltage scenario. This again puts the onus back on the battery manufacturer. I would not want to be them right now....lol.

ETA: it does state in the aviationweel article that the other "main" battery was the one that overheated. It seems likley these batteries are probably the same architecture if not the same part number. It also states in the article that the manufacturer of the batteries also makes the charging system.

[Fitter]

Originally Posted by LTC8K6

The 777 also has 2 generators per engine, and it can also be dispatched with it's APU inoperative.

The 747-400 series has an APU, but it's not expected that it would ever be used in flight. I have read that there is no normal in-flight start procedure for the 744's APU. The 744 has 4 engines, of course. So, it has 4 generators. In addition, the 744's engines are capable of windmilling and continuing to supply electrical and hydraulic power even if they quit running.

I can't imagine any engine windmilling fast enough to produce usable hydraulic pressure or to generate electricity.

[383LQ4SS]

Originally Posted by Fitter

I can't imagine any engine windmilling fast enough to produce usable hydraulic pressure or to generate electricity.

Why not?

[ben m]

I just want to thank the experts here, especially 383LQ4SS, for these detailed explanations. "Putting the E in jrEf" as they say.

Here's a question---probably unrelated. Do you have a sense of how much power and weight (including cabling) goes into the seatback-entertainment screens? It must be huge.

[Fitter]

Originally Posted by 383LQ4SS

Why not?

Low N2(3). I did say usable.

[SezMe]

Fitter, I don't understand that reply. Can you say more.

[383LQ4SS]

Originally Posted by Fitter

Low N2(3). I did say usable.

Understood. I do not know enough about the specifics of usuable air across the N2/N3 sections on 747's in flight. But at 250-350 kts I would not doubt it could still spin a decent enough to provide some system power. Especially hydraulics. I am sure someone has read a 747 manual and can confirm or deny.

For those that dont know...the main fan (N1) does not directly drive hydraulic pumps or generators. Those are driven by the inner core or the high pressure turbine (N2 and/or N3). When looking from the front the cross section of the high pressure turbine is significantly smaller than the large low pressure fan section. It really hugs the center of the engine. As a matter of fact it can be difficult to even see.This high pressure section is directly connected to the gearbox typically...and in no way connected to the low pressure fan (the big one in front, N1).
N1, N2 N3 are speeds of the various turbine sections. Typically displayed in the cockpit as % of RPM...such as 99.1% N1. This would mean the main fan is turning 99.1% of rated design rpm.

[383LQ4SS]

Originally Posted by ben m

I just want to thank the experts here, especially 383LQ4SS, for these detailed explanations. "Putting the E in jrEf" as they say.

Here's a question---probably unrelated. Do you have a sense of how much power and weight (including cabling) goes into the seatback-entertainment screens? It must be huge.

Hmmm..I really dont. I have never worked on one of the ultra modern large jets with all the interior gizmos. I too would guess it to be quite significant. A portion of that may be offset on modern aircraft that incorporate LED lighting. LED lighting is ideal for use in passenger jets for many reasons.

[Shadow the Poodle]

Originally Posted by Fitter

I can't imagine any engine windmilling fast enough to produce usable hydraulic pressure or to generate electricity.

British Airways flight 9 ( Speedbird 9 ) which suffered a four engine flameout due to volcanic ash ingestion over Indonesia, had both Hydraulic and (Intermittant) electrical power from its windmilling engines.

ETA: I have seen full hydraulic pressure from a C-130 Allison T56 engine during airstarts prior to ignition (<16%rpm), when doing multiple air tests.

[SezMe]

Originally Posted by 383LQ4SS

This high pressure section is directly connected to the gearbox typically...and in no way connected to the low pressure fan (the big one in front, N1).

Then what drives N1?

[383LQ4SS]

The high pressure section (n2) provides the usuable thrust/energy to the LP turbine (n1)...which in turn spins the large LP fan at the front.

here is a decent video.
http://flyopia.com/turbine-videos-ho...-engines-work/

Its basically a jet engine in the middle sandwiched by a turbine at the rear to extract thrust energy that turns the front fan. When I say not connected...I mean mechanically connected.

[SezMe]

Originally Posted by 383LQ4SS

When I say not connected...I mean mechanically connected.

Aha. Gotcha. That was what I thought - just wanted to make sure.

BTW, do you know why that little white spiral is painted on the ... er ... little hub at the center of the intake? Probably crappy description but I hope you know what I mean.

[Fitter]

Sezme, it provides a visual indication that the fan is turning. On Rolls-Royce maintainers also use it to locate the number one blade for maintenance purposes. Not sure if GE uses it for blade identification or not, I've only worked on fighter engines from them.

[Puppycow]

Boeing proposes full 787 battery fix to FAA: sources

Quote:

(Reuters) - Boeing Co on Friday gave U.S. aviation regulators its plan to fix the volatile battery aboard its new 787 Dreamliner, even though investigators have not yet determined what caused the batteries to overheat on two planes last month.

Boeing did not propose abandoning the lithium-ion batteries and is not working on a backup or longer-term fix for the problem that has grounded its entire fleet of 50 Dreamliners for nearly five weeks, three sources familiar with the plan said.

. . .

The proposed fix includes adding ceramic insulation between the cells of the battery to help keep cells cool and prevent a "thermal runaway" in which one cell overheats and triggers overheating in adjacent cells. It also includes building a stronger, larger stainless steel box with a venting tube to contain a fire and expel fumes outside the aircraft should a battery catch fire again, the sources said. In addition, the plan proposed wiring changes, self-torquing screws that will not come loose and battery alterations to prevent moisture and vibration problems, one of the sources said.

[a_unique_person]

If anyone was hoping for a quick fix, it's not going to happen. Boeing will have to demonstrate that what it is proposing works to the satisfaction of the NTSB and FAA, then implement that on each plane.

It will also have to fly the batteries around the to the planes on the ground, but transporting them as standard cargo now is also a problem. They aren't safe for that, either.

Airlines that have the 787 are reportedly making plans out for up to six months for alternatives.

[Mikemcc]

Originally Posted by Shadow the Poodle

British Airways flight 9 ( Speedbird 9 ) which suffered a four engine flameout due to volcanic ash ingestion over Indonesia, had both Hydraulic and (Intermittant) electrical power from its windmilling engines.

ETA: I have seen full hydraulic pressure from a C-130 Allison T56 engine during airstarts prior to ignition (<16%rpm), when doing multiple air tests.

Seen a Hercules 'bump-started' by using a second in front turning at high revs, using the wash to turn the blades on the second one

[Puppycow]

Setback to Boeing’s Hopes for Longer Range for 787

Quote:

With the technologically advanced 787, Boeing offered airlines big fuel savings and better comfort for passengers. It also promised something else: the ability to reach just about any airport on the globe without having to stop.

Boeing designed the jet to fly 330 minutes — five-and-a-half hours — from the nearest airport at any point on its routes, a feature that would allow extended flights over water or deserted regions like the North Pole. That held tremendous appeal for airlines, which often must stay within three hours of emergency landing spots, and Boeing estimated that 450 new routes would be created.

But Boeing is struggling to get past the 787’s recent smoke and fire episodes with its lithium-ion batteries that have led to the grounding of all 50 planes delivered so far. And with investigators in the United States and Japan still looking for the cause of those problems, it could be months before federal regulators would feel confident enough in Boeing’s redesign of the batteries to approve extending 787 flights to ultralong distances from the jetliner’s current three-hour limit.

That could dilute its appeal to some airlines and further raise the costs of the program for Boeing, which already was unlikely to make a profit on any 787s for at least two years. The company could lose orders and have to pay penalties to carriers if the 787 failed to meet its performance targets.

What a shame. I hope they get this problem solved, and I'm sure they will eventually, but it's a costly setback.

[Shadow the Poodle]

Originally Posted by Mikemcc

Seen a Hercules 'bump-started' by using a second in front turning at high revs, using the wash to turn the blades on the second one

Yep thats a procedure in the Flight Manual known as a "Buddy Start" used to start an engine with an inoperative starter motor. I have done one for practice and it is very unpleasant and even though carried out on a concrete pad still resulted in the aircraft being peppered with debris.
Our prefered procedure was to carry out a "windmill taxi start" which involves setting the propellor blades on the inoperative engine to 90 degrees than charging down the runway and carrying out essentially the airstart procedure and reducing the blade angle to cause the propellor to spin, until either 16% rpm, 100 Kts or 3000 feet of runway remained at which point we carried out an abort and all being well the engine accelerated to on speed.

These were massive examples of crew coordination with all three on the flight deck kept very busy.

Good times.

now back to the scheduled programme

[catsmate1]

Originally Posted by Shadow the Poodle

Yep thats a procedure in the Flight Manual known as a "Buddy Start" used to start an engine with an inoperative starter motor. I have done one for practice and it is very unpleasant and even though carried out on a concrete pad still resulted in the aircraft being peppered with debris.
Our prefered procedure was to carry out a "windmill taxi start" which involves setting the propellor blades on the inoperative engine to 90 degrees than charging down the runway and carrying out essentially the airstart procedure and reducing the blade angle to cause the propellor to spin, until either 16% rpm, 100 Kts or 3000 feet of runway remained at which point we carried out an abort and all being well the engine accelerated to on speed.

These were massive examples of crew coordination with all three on the flight deck kept very busy.

Good times.

now back to the scheduled programme

Rather reminds me of my great-uncle telling me of starting large aero-engines back in the twenties using hand pumps to spray a petrol/ether mix into the engine inlets and detonating it with a cranked magneto.

[Shadow the Poodle]

Originally Posted by catsmate1

Rather reminds me of my great-uncle telling me of starting large aero-engines back in the twenties using hand pumps to spray a petrol/ether mix into the engine inlets and detonating it with a cranked magneto.

Sounds like fun, I was doing these starts up until 2008 when I left the Airforce, at that point it was still a training item for bothe Hercules and Orions.

[Puppycow]

More on the shortcomings of the previous design and testing regime, and the new design:

Initial Tests of Battery by Boeing Fell Short

[LTC8K6]

http://www.faa.gov/news/press_releas...m?newsId=14394

Quote:

FAA Approves Boeing 787 Certification Plan

The Federal Aviation Administration (FAA) today approved the Boeing Commercial Airplane Company's certification plan for the redesigned 787 battery system, after thoroughly reviewing Boeing’s proposed modifications and the company’s plan to demonstrate that the system will meet FAA requirements. The certification plan is the first step in the process to evaluate the 787’s return to flight and requires Boeing to conduct extensive testing and analysis to demonstrate compliance with the applicable safety regulations and special conditions.

“This comprehensive series of tests will show us whether the proposed battery improvements will work as designed,” said Transportation Secretary Ray LaHood. “We won’t allow the plane to return to service unless we’re satisfied that the new design ensures the safety of the aircraft and its passengers.”

The battery system improvements include a redesign of the internal battery components to minimize initiation of a short circuit within the battery, better insulation of the cells and the addition of a new containment and venting system.
...

[LTC8K6]

http://news.yahoo.com/boeing-says-pr...--finance.html

Quote:

TOKYO (Reuters) - Boeing Co said its 787 Dreamliner jets could be airborne within weeks with a fortified power pack that would eliminate the risk of fire, confident the U.S. aviation authority would approve the redesigned battery soon.

Regulators grounded all 50 of the carbon-composite Dreamliners in use by airlines worldwide in January after a battery caught fire on a Japan Airlines Co Ltd 787 jet at Boston's Logan airport and a battery melted on an All Nippon Airways Co Ltd flight in Japan.

Boeing, which has Federal Aviation Administration (FAA) approval to test its new battery for certification, said Friday it will encase the redesigned power pack in a steel box, pack it with added insulation, heat-resistant material and spacers, drill drain holes to remove moisture, and vent any gases from overheating directly to the atmosphere outside the aircraft.

"If we look at the normal process and the way in which we work with the FAA, and we look at the testing that's ahead of us, it is reasonable to expect we could be back up and going in weeks, not months," the 787's chief engineer, Mike Sinnett, said at a briefing in Tokyo.

But the Civil Aviation Bureau (CAB), FAA's counterpart in Japan, dismissed Sinnett's prediction, saying it was still too early to say when 787 operations could resume.

Investigations by Japanese and U.S. transport regulators are still ongoing.

The investigators may never uncover the root cause of those failures, Sinnett said.

"Because we did not find the single root cause, we looked at everything that could impact a battery and set a broad set of solutions," Sinnett said.

The fortified power pack can withstand 80 possible malfunctions covering all the potential failure scenarios that Boeing engineers could envisage, he said.

Boeing is now about a third of a way through the certification process of the new battery, Sinnett said.

The aircraft maker will also bolster quality control at battery component makers GS Yuasa and Thales Sa and install a new charger that would be keep voltage within a tighter range to guard against possible overheating.

...

[dlorde]

Having the new batteries able to vent gases outside the plane sounds like a major rework; surely you can't just punch a hole in the fuselage and seal a tube to it that leads to the battery containment? Wouldn't you then have a whole bunch of new concerns, like temperature & pressure variations, water ingress & icing, robustness & resilience, etc. ?

[LTC8K6]

Originally Posted by dlorde

Having the new batteries able to vent gases outside the plane sounds like a major rework; surely you can't just punch a hole in the fuselage and seal a tube to it that leads to the battery containment? Wouldn't you then have a whole bunch of new concerns, like temperature & pressure variations, water ingress & icing, robustness & resilience, etc. ?

Yes, you can just punch a hole and install a tube and valve system.

Essentially, that's what regulates cabin pressure anyway. Holes in the fuselage with valves installed in them.

[a_unique_person]

They haven't found the root cause of the battery failures, so they are effectively going to mitigate the effects of a fire more effectively, and make the battery design more robust. This may be enough to get them flying again, but it's going to take longer than weeks to get that fully tested and certified. Perhaps Boeing was using '787' time to make the claim.

[383LQ4SS]

Originally Posted by dlorde

Having the new batteries able to vent gases outside the plane sounds like a major rework; surely you can't just punch a hole in the fuselage and seal a tube to it that leads to the battery containment? Wouldn't you then have a whole bunch of new concerns, like temperature & pressure variations, water ingress & icing, robustness & resilience, etc. ?

Yeah...that wont be too big of a deal. There is already holes and tubes and vents all over that thing. Adding another likely wont be too big of a deal.

Very surprised it has taken this long. I sill think they should have redesigned for dual batteries types. Lithium as well as the more common Lead/acid. That would have given them massive flexibility in the future.

[dlorde]

Originally Posted by LTC8K6

Yes, you can just punch a hole and install a tube and valve system.

Essentially, that's what regulates cabin pressure anyway. Holes in the fuselage with valves installed in them.

Oh, OK.

[Puppycow]

There's some more details and pictures here:

Boeing Discloses Fixes for Lithium-Ion Batteries

Quote:

Boeing officials have detailed for the first time their proposed fixes for the lithium-ion batteries aboard its 787 planes, and the changes include better insulation between the eight cells in the battery, gentler charging to minimize stress and a new titanium venting system.

But to prevent any new fire and smoke episodes like the ones that have grounded its fleet, Boeing proposed the crudest tool in its considerable technological arsenal: the battery itself will be sealed inside a steel box that would serve as the last safety rampart if everything else fails.

. . .

But the new safety features, made public late Thursday, were an admission that despite its substantial resources, Boeing might never determine what went wrong with the batteries. Still, the changes are intended to reassure regulators and the public that the planes are safe and should be allowed to fly again soon.

“This enclosure keeps us from ever having a fire in the beginning,” Mike Sinnett, the 787’s chief engineer, said during a news conference in Japan along with Ray Conner, the president and chief executive of Boeing’s commercial airplane division. “It eliminates the possibility for fire.”

Mr. Sinnett said that Boeing engineers had identified 80 different ways that the batteries could fail and modified the batteries as a result. But if, for whatever reason, a cell did overheat and combust, the steel casing would contain the smoke and fire, the venting tube would open, and the smoke would be pushed outside the plane instead of venting inside the cabin.

[tsig]

Originally Posted by Puppycow

There's some more details and pictures here:

Boeing Discloses Fixes for Lithium-Ion Batteries

Quote:

“This enclosure keeps us from ever having a fire in the beginning,” Mike Sinnett, the 787’s chief engineer, said during a news conference in Japan along with Ray Conner, the president and chief executive of Boeing’s commercial airplane division. “It eliminates the possibility for fire.”

Mr. Sinnett said that Boeing engineers had identified 80 different ways that the batteries could fail and modified the batteries as a result. But if, for whatever reason, a cell did overheat and combust, the steel casing would contain the smoke and fire, the venting tube would open, and the smoke would be pushed outside the plane instead of venting inside the cabin.

If the kind of contradictory thinking shown by the chief engineer is representative of Boeing engineering then this fiasco becomes more understandable.

[Puppycow]

It's not necessarily contradictory. The enclosure may serve two or more functions, not just one.