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FAA Grounds 787 Part 12  
User currently offline777er From New Zealand, joined Dec 2003, 12171 posts, RR: 17
Posted (1 year 6 months 3 weeks 3 days 14 hours ago) and read 31140 times:
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Link to thread #11 FAA Grounds 787, Part 11 (by 777ER Feb 23 2013 in Civil Aviation)

WARNING: Due to thread 9 going off topic quickly and turning into a 'battle ground', the moderators will be watching this thread frequently and ANY offending/rule breaking posts will be removed. Please respect each others right to have their opinion.

213 replies: All unread, showing first 25:
 
User currently offlinercair1 From United States of America, joined Oct 2009, 1323 posts, RR: 52
Reply 1, posted (1 year 6 months 3 weeks 3 days 7 hours ago) and read 30698 times:
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I'm reposting this from the end of the last string. I put a fair amount of effort into it and if it is at the end of the string - it is lost. Hope the mod's don't mind. The links to quoted replies do not work - obviously - so I deleted them.

Quoting Wisdom (Reply 208(prev thread)):

I suspect 3 possible sources of issues:
1. Wild frequency generation is not converted as accurately as required, causing the battery to even out the loads and heat up under a thermal fatigue effect. The only way to find out is to fly or do run-ups on the accident NH B787 engines and hook some ultra-sensitive measuring equipment.
2. Static electricity build-up caused by sensing or converting equipment or even by the fuselage.
3. Earthing problems. On aluminum aircraft the metal fuselage is your negative port, what happens on a CFRP aircraft? Can a CFRP fuselage be conductive enough that it does mitigate the negative load sufficiently to avoid that your battery or your fuselage become a capacitor?

A combination of the above is also possible.

From a EE standpoint. (Yes - I'm a Fire Fighter, but my 'job' is a EE - BS, MS, Ph.D.) none of these are overlly compelling - basically you are throwing stuff on the wall and hoping it sticks.

1 - Wild frequency generation.
"Wild" sounds impressive and dangerous - but it is not. It just means variable frequency. The VFSG on the 787 generate 235V AC at a frequency of 360-800 hz - they are not generators, they are alternators and by using direct drive and variable frequency the complex mechanical systems required to turn the alternators at a fixed speed are eliminated.
Yes - that is correct, the frequency of AC power is directly related to the rotation speed of the alternator.
What is done in the 787 with this power is 4 fold.
A) Large, frequency insensitive, loads are driven directly by the 235V Variable Frequency current. Things like wing de-ice heaters do not care about the frequency.
B) Some of the power is converted to 115AC 400Hz - traditional power in the aircraft. This is done by a device called an Auto-Transformer. Auto transformers convert both frequency and voltage.
   The auto-transformer is the electrical equivalent of the constant speed mechanical drive in a traditional a/c system. Frankly - an auto-transformer is far more reliable.
C) Some of the power is converted to 28V DC - this is done with a rectifier. It is really a transformer-rectifier so that it can deal with the variable frequency. In the simplest configuration - a rectifier is a diode and capacitor. Of course, these are far more sophisticated. Again - nothing special here.
D) The last conversion is to 270VDC. This is a voltage step up as well as a rectification - so an auto transformer/rectifier is used.
   The reason you use high voltage DC is to minimize wire size. To deliver 1000 watts at 27VDC takes 37 amps -a large wire. To deliver that same 1000 watts at 270VDC is 3.7 amps.

   - BTW - the alternator in your car is a 'wild frequency'. It rectifies it to 14.7ish volts DC, and many cars then have inverters to power AC. Sound familiar? Same approach - smaller and not as well regulated. Some hybrids even use a pancake motor between the engine and the tranny - and use that as the starter.

Here is a diagram showing it:
B787 Electrical Architectur

B787 Electrical Architecture

2. Static electricity build-up caused by ..
Static discharge - or ESD (electro-static discharge) is always a design concern - however, it is much more likely to cause issues with small electronics that large power system. While there is plenty of potential (voltage) and energy to damage a microchip, that is not the case for large power systems. They can absorb ESD events with no issue. If the problems were were seeing were electronic components failing (I'm not talking chargers pushing lots of current), then ESD woudl be a likely culprit.
   Power surges from other high power system - i.e. ground systems - are much more likely IMO - if we are taking externally caused damage at all.

3. Earthing problems (we call them grounding problems here in the states).
I think it is very unlikely that Boeing, or anybody, is shunting large currents through the skin of either a carbon fiber or aluminum skin. Small currents - sure. Larger ones, no way. Again - if we were seeing damage to electronic components (chips and such), then yes. Batteries and large loads - not likely.
   One aspect of grounding problems that could cause issues would be a high resistance in the ground side of a voltage sensing circuit. That could cause the voltage to be mis-read as low and the applied voltage raised. But - you can be sure that if your are wiring a sensitive sensing circuit - you are not relying to the stray return path of a aluminum or CF skin.

Of course - the predictable response will be that something ESD'ish or grounding problems are causing problems with the chargers. Have we seen any evidence of charger problems (not wiring issues)?

Quoting BoeingVista (Reply 210-prev thread):

Boeing for whatever reason, chose the one with the most power but also the most volatile.

Because...

Quoting Stitch (Reply 203-prev thread):

Boeing and Cessna likely chose lithium cobalt oxide because even though it was known to be a volatile cathode chemistry, it was also one of the more mature ones a decade ago when they started development of their respective programs. So having made the decision to use lithium-ion batteries, both Boeing and Cessna went with the one with the most knowledge and experience rather then choose a new, untested cathode chemistry even if it appeared to be less volatile. There were risks with LCO, but they were known risks and Boeing (incorrectly) believed they had addressed them.


Finally...
Quoting ServantLeade (Reply 211-prev thread):
Quoting
Sorry, but that makes absolutely no sense. Boeing produces the airplane and the batteries are part of it, and you say that Boeing is not at fault when they fail?

Wrong - Boeing is "responsible" but may not be "At Fault". When the headlight on your brand new car fails because it was defective, you go to the car dealer. They are "responsible"- and they give you a new headlamp. But the party at "fault" is the one who produced the defective headlamp. Last I checked, no car manf was making headlamps.



rcair1
User currently offlineServantLeader From United States of America, joined Jan 2013, 69 posts, RR: 0
Reply 2, posted (1 year 6 months 3 weeks 3 days 7 hours ago) and read 30641 times:

Quoting rcair1 (Reply 1):
Wrong - Boeing is "responsible" but may not be "At Fault". When the headlight on your brand new car fails because it was defective, you go to the car dealer. They are "responsible"- and they give you a new headlamp. But the party at "fault" is the one who produced the defective headlamp. Last I checked, no car manf was making headlamps.

Your rationale for differentiating responsibility from fault is based on the assumption that the battery issue is isolated to the battery and that Boeing bares no responsibility for its design shortcommings given the application, neither of which are valid. Boeing owns this problem from A to Z.

[Edited 2013-03-01 06:34:09]

User currently offlinehivue From United States of America, joined Feb 2013, 1077 posts, RR: 0
Reply 3, posted (1 year 6 months 3 weeks 3 days 6 hours ago) and read 30488 times:

Quoting ServantLeader (Reply 2):
Boeing owns this problem from A to Z.

I don't think anyone disputes the fact that Boeing owns the problem (especuially not Boeing). But "A to Z" suggests that Yuasa, Thales, Securaplane, ANA, JAL, UA, etc. are all innocent bystanders. The official investigations have so far produced no facts to support this.


User currently offlinemjoelnir From Iceland, joined Feb 2013, 1450 posts, RR: 2
Reply 4, posted (1 year 6 months 3 weeks 3 days 3 hours ago) and read 30136 times:

As rcair1 is telling others to be exact on technical details, I have to nitpick a bit.

An alternator is always a generator, a generator is a device converting mechanical energy into electrical energy it includes alternators, dynamos and so on.

I do hope that Boeing is not using many transformers or auto transformers in the B 787, they are old fashioned, heavy and not used in modern AC/DC or DC/DC converters, frequency controllers, power supplies etc, switched thyristors are used instead.

Variable frequency generators are of course state of the art, apart from air planes and cars you find them in windmills, ships, some modern hydro power stations and so on. You run that through a frequency converter (switched thyristors) and you have the right frequency.
The part were wisdom (user) is coming in, you can get out of a badly designed or even broken frequency converter or switching power supply high frequency waves.
I expect Boeing to use good equipment not emitting high frequency waves.
And if something is broken, a Boeing engineer will find an oscilloscope to find that culprit.

Static electricity has been the bane of electrical installations. That is why you ground (or earth) everything in sight and bad grounding has been the reason for many strange electrical happenings.
You put a florescent lamp above some sheet metal and you get a static charge for example.
Lets not forget that the ground wire of the battery in the JAL B 787 was broken.

The Americans have so nice words "wild frequency generation" sounds so much more macho than variable frequency.

Some reading material on transformer you also find auto transformer.
http://www.electrical4u.com/electrical-transformer/index.php
I would say have look at the Wikipedia but that gives always a horrible reaction.

[Edited 2013-03-01 11:21:19]

User currently offlinercair1 From United States of America, joined Oct 2009, 1323 posts, RR: 52
Reply 5, posted (1 year 6 months 3 weeks 2 days 22 hours ago) and read 29646 times:
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Quoting mjoelnir (Reply 4):
An alternator is always a generator, a generator is a device converting mechanical energy into electrical energy it includes alternators, dynamos and so on.

A generator can also generate steam, oxygen, nitrogen, hot air (or am I confusing that will that some a.net posters. The point is that from an electrical engineering standpoint, not a generic standpoint - they are alternators, not generators.

As for the auto-transformers. As you see from the diagram I attached - which is a Boeing diagram, they call them "ATRU - Auto Transformer Rectifier Unit" and "ATU" - Auto Transformer Unit. I suspect these are advanced versions, but since I have no insider information on what the really use - I reported what they say. By the way - I most of this is from Hamilton Sundstrand - which also provides multiple subsystems for other aircraft manufacturers.
Here is a youtube video by Hamilton Sundstrand about their role in the 787.
http://www.youtube.com/watch?v=dPltBtBa7VQ&feature=player_embedded#!
It is not clear if they make the ATRU/ATU/TRU systems.



rcair1
User currently offlineKaiarahi From Canada, joined Jul 2009, 3005 posts, RR: 27
Reply 6, posted (1 year 6 months 3 weeks 2 days 22 hours ago) and read 29634 times:

Quoting ServantLeader (Reply 2):
Your rationale for differentiating responsibility from fault is based on the assumption that the battery issue is isolated to the battery and that Boeing bares no responsibility

Rubbish. That's not what rcair1 was saying. In my professional life, I'm accountable for many things where the "fault" was not mine, but I remain accountable. My executive assistant or my junior executives may make a mistake which is their "fault" but for which I'm nevertheless accountable to my client, even though I did not make the mistake. That doesn't mean I should personally supervise every single action they take - it just means I should hire carefully with due diligence and establish clear escalation matrices. Yuasa, Securaplane, Thales and Hamilton Sundstrand have specific, demonstrated expertise and I'm sure Boeing exercised due diligence before engaging them to design / produce components.

Some of the (respected) component / systems suppliers for the 787 include:

Mitsubishi (wings)
Kawasaki (fuselage sections)
Latecoere (passenger doors
Saab (cargo doors)
Messier-Dowty (landing gear)

Check out your own PC. Pretty much every component (motherboard, video board, audio, sound, RAM, fan, software) has a different manufacturer. If they didn't exist, you wouldn't have a PC.



Empty vessels make the most noise.
User currently onlineWildcatYXU From Canada, joined May 2006, 2613 posts, RR: 5
Reply 7, posted (1 year 6 months 3 weeks 2 days 19 hours ago) and read 29321 times:

Quoting rcair1 (Reply 5):
As you see from the diagram I attached - which is a Boeing diagram, they call them "ATRU - Auto Transformer Rectifier Unit" and "ATU" - Auto Transformer Unit. I suspect these are advanced versions, but since I have no insider information on what the really use - I reported what they say.

Well, even without an insider information is clear that these would be very advanced electronic devices. For starters, a plain auto transformer would convert the 230V variable frequency AC only into 115V variable frequency (not to mention that it would be large and heavy). To gain 115V/400Hz AC a voltage/frequency converter is needed. I have zero reason to believe it's not state of art. Similarly, the 230V/28V TRU is definitely not just a transformer with a diode bridge rectifier...
oh, how I wish to see at least the block diagram of both units.


User currently onlineYVRLTN From Canada, joined Oct 2006, 2469 posts, RR: 0
Reply 8, posted (1 year 6 months 3 weeks 2 days 18 hours ago) and read 29120 times:

Quoting mjoelnir (Reply 4):
Static electricity has been the bane of electrical installations. That is why you ground (or earth) everything in sight and bad grounding has been the reason for many strange electrical happenings.

So if there were faulty connectors, or if they were not installed correctly, even if it didnt result in arcing exactly it wouldnt be earthed, so could that result in the battery issues we have seen because it is the "weakest link" in the system?



Follow me on twitter for YVR movements @vernonYVR
User currently offlinemjoelnir From Iceland, joined Feb 2013, 1450 posts, RR: 2
Reply 9, posted (1 year 6 months 3 weeks 2 days 15 hours ago) and read 28492 times:

Quoting rcair1 (Reply 1):
Auto transformers convert both frequency and voltage.

No way you can control frequency with a auto transformer.

Auto transformer is kind of electrical transformer where primary and secondary shares same common single winding.
see:
http://www.electrical4u.com/electric...l-transformer/auto-transformer.php

I do not no why your diagram uses words like Auto transformer rectifier unit or Auto transformer unit.
Perhaps it sounds nice like wild frequency generation.

We in my company have not been using transformers with an rectifier to produce DC for around 25 years in the machines we produce.

The Equipment we are using today is called in the industry an AC to DC converter.
In the computer industry they call it a switching power supply.
The definition what it does is usually done with defining the input and defining the output.
The way it works is roughly using a rectifier with switched thyristors (IGBT).

Brown area 28V DC
25 years ago we would use a transformer from AC 230 V to AC 28 V, than a rectifier for AC to DC and a bank of capacitors to clean away the waves. For an output 30 V 10 A it would have been about 15 Kg.
Today the transformer less AC to DC converter does it with about 1.5 kg

Blue area 115V AC variable frequency
Frequency converter.
In the old days you used a motor and generator set. Very heavy and not really good for variable frequency's.
I do not know a way to do this with transformers
That was why fixed frequency was used.

Today you use also switched thyristors.
First you rectify and than you use thyristors to build the sine wave.
You control the frequency and can take down the output Voltage.
That is why you can today use variable frequency generation.

Green area.

230V AC to 260V DC

In the old days you would use an transformer to up the voltage and than an rectifier to make the DC.

Today you would up the voltage with a voltage multiplying rectifier and use a DC to DC converter with switched thyristors.
Or a voltage multiplying rectifier with switched thyristors.

No transformers or auto transformers in sight.


User currently offlinesweair From Sweden, joined Nov 2011, 1824 posts, RR: 0
Reply 10, posted (1 year 6 months 3 weeks 2 days 15 hours ago) and read 28476 times:

Is there Li-ion chemistry's in the market that are considered as safe as old batteries? Readily available? But changing chemistry will certainly not be a trivial task, as it has the be designed to fit the electrical system and everything else.

User currently offlinemjoelnir From Iceland, joined Feb 2013, 1450 posts, RR: 2
Reply 11, posted (1 year 6 months 3 weeks 2 days 8 hours ago) and read 27668 times:

Quoting rcair1 (Reply 1):
Quoting Kaiarahi (Reply 11):

What I find strange in the diagram is the 260 V DC.

Usually when you go for lightweight you would not convert AC to DC and up the voltage.
The best way would be to generate the right voltage in AC and rectify to DC.
If you want 400 V DC power you produce 400 V AC in the generator, and so on.
You produce the highest voltage you need and cascade down.
I speculate if the number for the 260 V DC is the top voltage of a pulsing wave or if it is the effective voltage.

The power supply's for the two lower voltages 115 AC or 28 V DC, usually do not care if you feed them
260 V AC or 230 V, they usually cover a range of Input voltages.

Transformers are heavy, you usually try to do without them for less weight.

You still use a lot of transformers to increase voltage or decrease voltage in Power distribution systems.
I would not expect them aboard an modern aeroplane.
Perhaps on board a AN 124 transporting them.

Regarding transformer.

The difference between a transformer and an auto transformer is, that a transformer uses double sets of windings one each for inputs and one for outputs.
The auto transformer uses the same windings for in and output.

[Edited 2013-03-02 05:25:06]
Big version: Width: 344 Height: 288 File size: 5kb
Big version: Width: 344 Height: 288 File size: 5kb


[Edited 2013-03-02 05:28:58]

User currently offlinemjoelnir From Iceland, joined Feb 2013, 1450 posts, RR: 2
Reply 12, posted (1 year 6 months 3 weeks 2 days 8 hours ago) and read 27566 times:

I have not worked with an alternator on board a modern commercial aeroplane.

But the alternators on board a ship do usually not only have a floating frequency, 45 to 65 Hz but also a floating voltage,
380 V AC to 440 V AC. The higher voltage is associated with the higher frequency.
For my equipment I have to install usually a frequency converter, out of that I would get a steady frequency and a fast voltage adjusted to the lowest voltage I will get, on the example above it would be 380 V.

[Edited 2013-03-02 05:57:08]

User currently offlineStitch From United States of America, joined Jul 2005, 31003 posts, RR: 86
Reply 13, posted (1 year 6 months 3 weeks 2 days 7 hours ago) and read 27453 times:
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Quoting sweair (Reply 10):
Is there Li-ion chemistry's in the market that are considered as safe as old batteries?

Lithium iron phosphate (FiFePO4) should be closest It has moderate power density (someone noted Boeing would need to add one additional cell to meet the same capacity as the current lithium cobalt oxide unit) and it effectively does not enter thermal runaway (temperature rise is on the order of a few degrees Centigrade per minute compared to a few hundred degrees per minute for LiCoO2).


User currently offlinecomorin From United States of America, joined May 2005, 4896 posts, RR: 16
Reply 14, posted (1 year 6 months 3 weeks 2 days 7 hours ago) and read 27401 times:

Quoting mjoelnir (Reply 14):

I'm an ex-EE and I appreciate your posts. It's been 50 years since I used an auto-transformer but surprised that they are used on aircraft given the heat losses from hysteresis. Has that tech changed over the years?

Modern systems indeed use high-current solid-state devices for both rectification and frequency control. A friend of mine (ex-Bell Labs) is working on programmable software-driven thyristors so much is happening in this field.

I am sure that rcair1 knows what he is talking about, given his excellent posts, and is not implying that we are using 19th century technology on the 787!  


User currently offlinemjoelnir From Iceland, joined Feb 2013, 1450 posts, RR: 2
Reply 15, posted (1 year 6 months 3 weeks 2 days 5 hours ago) and read 27206 times:

I am an mechanical engineer with a diploma from a German school.
My diploma work in 1983 was about computer programs to help to design cranes.
I have build my own computer hardware and boards and programmed in basic, Fortran, pascal and assembler and now in C++.
I have programmed industrial controllers for example Siemens in step.
In one firm I sell equipment for tank trucks, fuel depots and aircraft refuelling. I also sell ex proofed electrical equipment.
In another company I sell equipment for the fish processing industry. We have a service shop, machine tool shop, produce machines, sell other machines on land and on ships.
I have been a volunteer fire fighter and mountain rescue.
I am a private pilot.

I started posting here when I could not read any longer without getting angry the following statemenst regarding the B 787 battery incidents:

- the containment worked (if it had worked the B 787 would not be grounded)
- the containment contained the flames (the Boston fire crew does not agree)
- when the NTSB talked about flammable liquid, and posters disregarding that as a danger
- there was no real danger, nothing happened
- the B 787 was prematurely grounded
- on the ANA flight there was no danger, the battery did not ignite.

Are that the "experts"?

When I hear vapours of flammable liquids are vented into an electronics bay, the cold sweat runs down my neck and I understand the instant grounding.

If somebody asks me what could ignite the vapours, my answer is the electrical cabinet.
You switch a mechanical relay and you have your spark plug.
That is why in an ex proofed environment you have a case around the relay filled with inert gas or equipment that can not produce a spark which excludes all high power equipment.

I do not like to hear if one has a different opinion, that one should to listen to the "experts". Physical and chemical properties do not change because they are applied to a aeroplane, we all work with the same stuff.

I can agree with many posts of rcair1, but in this case I do not agree.

I have never seen an auto transformer used to control frequency of an action current.

Using AC/DC, DC/DC and frequency conversion is my daily bread.

When I see this name, Auto Transformer Unit, I assume they do not talk about an auto transformer, but that the sales people had a field day finding catchy names.


User currently offlinemjoelnir From Iceland, joined Feb 2013, 1450 posts, RR: 2
Reply 16, posted (1 year 6 months 3 weeks 2 days 4 hours ago) and read 27121 times:

Quoting 777er (Thread starter):
230V AC to 260V DC

Quoting myself in reply 7

In the old days you would use an transformer to up the voltage and than an rectifier to make the DC.

Today you would up the voltage with a voltage multiplying rectifier and use a DC to DC converter with switched thyristors.
Or a voltage multiplying rectifier with switched thyristors.

Here I was talking absolute nonsense. You could use voltage multiplying rectifiers, but it is a bad solution for high power application.
You would need a transformer here to go from 230 V AC to 260 AC to rectify to 260 V DC.

I still do not understand why somebody would design a system that way, as you could either use 230 V DC or up the alternators to 260 V AC and you get rid of quite few Kg in transformers.

[Edited 2013-03-02 09:32:29]

User currently offlineXT6Wagon From United States of America, joined Feb 2007, 3409 posts, RR: 4
Reply 17, posted (1 year 6 months 3 weeks 2 days 3 hours ago) and read 26924 times:

Quoting Stitch (Reply 15):
it effectively does not enter thermal runaway (temperature rise is on the order of a few degrees Centigrade per minute compared to a few hundred degrees per minute for LiCoO2).

even better from the chart posted way back in this mess of threads its peak temp was roughly 1/2 that of the current battery chemistry. Which should prevent the burning of the connector through the containment vessel we saw in the boston fire. I'm not sure if the containment could be lighter as it looks like they were already running not too far over the minimum wall thickness required for handling during MX.


User currently offlineWisdom From , joined Dec 1969, posts, RR:
Reply 18, posted (1 year 6 months 3 weeks 2 days 3 hours ago) and read 26872 times:

RCair, you could be an electrical engineer all you want, I've seen very clever guys with 30 years of experience as a B2 electrical engineer working on aircraft and knowing it inside out, struggling to find an answer for simple problems in a simple wiring system that I solved in 30 seconds.

TRU converts AC current and tension into a pulsating current and tensions.
The big difference between a wild frequency and constant frequency generation is that in the latter case, both current and tension will pulsate at the same frequency while in the former, they will not be.

In wild frequency systems, these pulses will not be constant and it's very hard to filter them out using capacitor and regulator systems. So you have to place several of these in series to hope to achieve the required result.

360-800 Hz sounds about right given N2 rpm range.The frequency range is not so vast but still vast enough to create undetectable repetitive micro-surges that the filters can't filter out.

Given both battery incidents started occurring at or close to the ground when the engines and their generators were providing the most unstable frequency regimes, ie when the power lever is most moving during the approach, taxi and departure phases, it's not unlikely that this is what's causing the battery to heat up.

Quoting rcair1 (Reply 1):
  - BTW - the alternator in your car is a 'wild frequency'. It rectifies it to 14.7ish volts DC, and many cars then have inverters to power AC. Sound familiar? Same approach - smaller and not as well regulated. Some hybrids even use a pancake motor between the engine and the tranny - and use that as the starter.

Many cars have inverters to power AC? Camping cars and some cars that have sockets for cooling boxes maybe, most cars only have DC.
What you fail to grasp is that while your B787's battery is about the same size as your average car battery, your car's generator generates maybe around 1kVA, while your engines are around 1000kVA.
The issue is not the voltage, as it will be around 115V, the issue is your huge current pulses.

When you have a 1kVA generator like in a car, your current pulses will be much smaller and less variable.
So there, even if you have a wider RPM and frequency range it doesn't matter because the pulses are barely detectable.

http://electriciantraining.tpub.com/14179/img/14179_172_2.jpg

Do the math, 1kVA, 12V. How much is your current?
Do the math, 1000kVA, 115V. How much is your current?
So as you realise, the car/B787 comparison doesn't stand as current pulses are in different dimensions.


User currently offline2175301 From United States of America, joined May 2007, 1071 posts, RR: 0
Reply 19, posted (1 year 6 months 3 weeks 2 days 2 hours ago) and read 26692 times:

Please be aware that industries develop their own internal lingo to describe things that is carried forward many decades.

As such, I have no doubt that the current use of the term "auto-transformer" does not mean an actaul "auto transformer" with windings and steel plates; just the modern equivalent that performs essentially the same function as the original "auto transformers" 30 or 40 years ago.

That should clear up some confusion.

Another item: I do remember that there was a way to wind an old style transformer such that the output was at 1/2 or 1/3 the frequency of the input. My memory is this involved multiple coils and some fancy wiring; but it did exists. It would not surprise me if this was called some kind of "auto frequency converting transformer" which got shortened to "auto-transformer" for the purpose of the airline industry.

The final item: Modern voltage and frequency conversion circuits are way beyond the example above in Wisdom's post 20 to effectively make his diagram and argument about possible frequency issues meaningless. Those issues were solved several decades ago.

I have decade old standard industrial pure sine wave output back up power supplies in my house which take 90-500 V input 48-62 Hz input, and outputs on one plug a pure DC output (I am not sure of the voltage - but the same as the battery circuit); and I have selected it to output 120V pure sine wave 60 Hz on the receptacles (I can program for several options). The batteries supply up to several days of power in the event of a power outage. I have this for my boiler/hot water (home heating) and for some medical equipment I own. I buy these used when they come up on the market. While I stick specifically to Liebert brand equipment in a specific model series for standardization; at least a half dozen companies have been selling this kind of equipment to companies and industry for 15+ years.

To suggest that Boeing (and the various companies involved in the design of the 787 electrical system) are not even using standard commercial circuits that eliminate the pass though noise of simple rectifiers and have been marketed by multiple companies for over 15 years in standard commercial equipment does not pass the common sense test.


Have a great day,


User currently onlineairtechy From United States of America, joined Dec 2006, 502 posts, RR: 0
Reply 20, posted (1 year 6 months 3 weeks 2 days 1 hour ago) and read 26597 times:

I suspect that a discussion of the aircraft electrical system at this level of detail should be carried on in the tech/ops forum. Also, I certainly don't and I suspect no one on this forum knows what is in the very upper level block diagrams of the electrical boxes. Functionality is often described in terms carried forward by years of common usage.

Unless I was able to peruse released schematics, I certainly wouldn't feel qualified to comment on the 787 electrical system and certainly not to criticize others on their comments about it.

I doubt that Boeing....or their subcontractors.... would use anything other than the latest technology despite how the block diagram may be labeled.


User currently offlineWisdom From , joined Dec 1969, posts, RR:
Reply 21, posted (1 year 6 months 3 weeks 2 days 1 hour ago) and read 26541 times:

Sorry, when your current is alternating or pulsating 800 times a second at 10.000 amperes, it's no longer noise we're talking about (remember that 1A can kill you), it's an "EMP". Even if the DC system doesn't require that much of the current, you still have to try to filter the ample pulses, plus all the variables you deal with such as switching other major "customers" off.

Whatever is used on aircraft is 20-30 years old technology in other industries. The technology has to be proven in other heavy duty applications before they can be installed on aircraft.

On A330's, you still have diode-based rectifier units. Having no knowledge of what is the standard outside the aerospace, this is what I know and it's been in use since a long time. It's proven to work well.

When you have a system pulsating at 800hz, I can't help but wonder whether a recording system like the FDR can record a momentary surge lasting only one period of 0,00125 seconds or a few such periods. Such a short surge would not be large enough to make it to your frequency read-out anyway, and that's usually where the recording is taken.
Also what happens when you switch heavy users like the huge airco system on/off?

Dear airtechy, I am trying to keep everything in simple terms for everything to be understandable for everyone to follow. It's useless to throw a bunch of technical terms and to pretend to know something better, we're not talking about rocket science here, it's simple AC to DC conversion.

Don't you suspect that AC to DC conversion can yield impurities resulting in problems at the battery level?

[Edited 2013-03-02 13:05:07]

User currently offlinemjoelnir From Iceland, joined Feb 2013, 1450 posts, RR: 2
Reply 22, posted (1 year 6 months 3 weeks 2 days ago) and read 26432 times:

Quoting Wisdom (Reply 24):
Sorry, when your current is alternating or pulsating 800 times a second at 10.000 amperes, it's no longer noise we're talking about (remember that 1A can kill you), it's an "EMP". Even if the DC system doesn't require that much of the current, you still have to try to filter the ample pulses, plus all the variables you deal with such as switching other major "customers" off.

Whatever is used on aircraft is 20-30 years old technology in other industries. The technology has to be proven in other heavy duty applications before they can be installed on aircraft.

On A330's, you still have diode-based rectifier units. Having no knowledge of what is the standard outside the aerospace, this is what I know and it's been in use since a long time. It's proven to work well.

When you have a system pulsating at 800hz, I can't help but wonder whether a recording system like the FDR can record a momentary surge lasting only one period of 0,00125 seconds or a few such periods. Such a short surge would not be large enough to make it to your frequency read-out anyway, and that's usually where the recording is taken.
Also what happens when you switch heavy users like the huge airco system on/off?

Dear airtechy, I am trying to keep everything in simple terms for everything to be understandable for everyone to follow. It's useless to throw a bunch of technical terms and to pretend to know something better, we're not talking about rocket science here, it's simple AC to DC conversion.

Don't you suspect that AC to DC conversion can yield impurities resulting in problems at the battery level?

I think aircraft are usually old technology as far as I have come near to it.
They do not follow modern technology because it is just too expensive to certify something new every year.

There is one exception, usually when they make a new type they take all the new stuff.

When you look at AC/DC, DC/DC converters and frequency controllers it is a new world.
Forget transformers, diode based rectifiers and banks of capacitors.
You do not need any longer shielded cables to run a variable frequency drive.
The converters pick the incoming wave into pieces and build with fast switching thyristors a new sine wave or a very clean DC.
This technology started really with computers and is there called a switching power supply.


User currently offlineWisdom From , joined Dec 1969, posts, RR:
Reply 23, posted (1 year 6 months 3 weeks 1 day 22 hours ago) and read 26176 times:

I must be honest with you, I've never heard about Thyristors in an aaerospace context.


Regarding the B787, I found this:

Thales’s power conversion system has achieved a very high power density benchmark,
further contributing to reductions in both weight and volume onboard the B787. Lightweight
electrical circuits now replace some hydraulic circuits, meaning a greater range of systems
are now powered by electricity. For instance, the B787 features electrical brakes. The newgeneration power conversion system includes an innovative transformer and rectifier solution
that supports the B787 high-voltage DC network.
Boeing chose Thales’s lithium-ion battery technology, which provides higher reliability and
improved maintenance compared to traditional solutions, for the B787 low-voltage DC
emergency back-up subsystem. This is a first in civil aviation, with Thales as prime contractor
in association with Securaplane of the United States and GS Yuasa of Japan.

http://www.thalesgroup.com/Press_Rel...2010/20100119_-_PR_press_kit_B787/


User currently offlineWisdom From , joined Dec 1969, posts, RR:
Reply 24, posted (1 year 6 months 3 weeks 1 day 21 hours ago) and read 26169 times:

Well wisdom doesn't ask questions like these:

Quoting rcair1 (Reply 214):

Couple of questions:
- Can the RAT on the 787 start the APU?
- Can the main battery on the 787 start the APU?
- Are the 2 engines on the 787 (or any plane) considered 'independent'.
- Are the 2 alternators on each 787 engine/APU considered independent?

A RAT starting an APU... that's the best one. Are you an avionics engineer or just an electrics engineer?
If the RAT is starting the APU, who's going to power the flight controls and your essential bus? I doubt that starting the APU is anymore important than flying the airplane, or is it?

Can the main battery start the APU?
Of course the main battery can start the APU. There's no aircraft in the world that can't start an APU from the main battery. However, a separate APU battery is useful when you're dealing with larger APU's, so as to avoid purging huge capacities from your main batteries and also as a redundancy when you're dealing with an electrical failure. When you're running on your main batteries after an electrical failure, the last thing you want to do is to waste the little capacity you have on trying to start the APU.

Are the 2 engines considered independent? If you have experience working with aircraft, you should have gotten training about that, so why ask?

Are the 2 alternators on each 787 engine considered independent?
Except for general aviation aircraft and some military aircraft, in civil aviation we always speak about generators. On the B787 we also speak about generators. So why insist about "alternators"?

Something's fishy here.
Definitely not questions an avionics engineer would ask.


25 Post contains links BoeingVista : An ex NTSB board member thinks that the FAA is inappropriately using the Airworthy Directive system and should have pulled the 787's type certificate.
26 par13del : From the article: It’s a lot easier to say that an AD has been complied with than to ensure that the requirements of a type certificate have been me
27 7BOEING7 : The APU can be started by the APU battery with the assistance of the main battery. The front external or any engine generator can also provide power
28 CaliAtenza : What about using batteries from a different supplier and testing those to see if the same problems occur? Im sure this has been brought up in the othe
29 sweair : So would swapping to the safe Li chemistry even satisfy the worst critics here? Or is the only way to satisfy them going the route of their favorite p
30 Wisdom : I know that very well. The question was literally whether the main battery can start the APU, and the answer is yes. The question was not whether the
31 rheinwaldner : Current pulses happen - by voltage pulses. There is no current pulse without a voltage pulse, that causes it (unless the load is higly capacitive). S
32 2175301 : Not only would all of this been tested in the lab; Boeing (and all other Aircraft Mfrs) fly heavily instrumented test aircraft for many months to ove
33 Post contains links Wisdom : I appreciate the last 2 posts. At least we are discussing rationally and constructively. 2175301, regarding the FDR, I read somewhere that due to a wi
34 2175301 : However, the batteries have a built in low voltage cut off to prevent damage (in this case I am defining the assembly of cells and control circuits w
35 Wisdom : Boeing engineers? Where? You mean those guys "sharing details" on why the FAA and the NTSB are wrong and that despite the safety factor, keeping the a
36 RickNRoll : I don't recall that they did. IIRC, they all take the incident seriously, but do object to speculation and bickering on the matter.
37 Post contains images lightsaber : Actually, engineers are about the last to bend to commercial pressure. A few? Sure. Now that the 787 has this much attention? The 787 will fly again
38 777ER : Please remain on topic and not discussing what your job/qualification etc is. This thread is for the discussion regarding the current grounding of the
39 seahawk : I personaly think flying the aircraft needs to be done. Preferably the 2 that had the incidents and 2 others to cross check. If possible improve the m
40 AeroWesty : News has gone dark on the fate of the JAL plane sitting at BOS. No updates on whether it is flyable as is, with just a new battery installed, or if B
41 Post contains images rcair1 : Internet is down - so I haven't looked at stuff in several days - and it will continue to be down for about a week. The price of living in the boonies
42 Post contains images lightsaber : We'll keep on topic. And that topic is the need to get the 787s back flying. I agree with the suggestion that the two to fly are the ones that had iss
43 Post contains links ServantLeader : Boeing Airplane head Ray Conner sees no reason to adjust 787 delivery forecasts for 2013 -- gee, what a surprise. The corporate bubble world must be a
44 7BOEING7 : Right now there is no reason to think differently. If, big if, the FAA buys off the fix and everything is wrapped up by June or July getting 60-70 ai
45 Post contains links art : (Reuters) - Boeing Commercial Aircraft Chief Executive Ray Conner said the company is very confident about its proposed fix for batteries that melted
46 Post contains links KarelXWB : See http://www.aviationweek.com/Article.aspx?id=/article-xml/awx_02_28_2013_p0-554228.xml
47 BestWestern : Just like they saw no reason to adjust the original first flight schedule. This is corporate governance at it's worst.
48 mjoelnir : You could fly the ANA B 787 again in unchanged condition, new battery of course. In case of the Boston JAL, she will hardly fly but everything being
49 par13del : I would agree that was, this as in now is different. As of today, they are: 1. Continuing to build 787 as per schedule 2. Ramp up production to meet
50 7BOEING7 : They've got plenty of pilots to handle the load, any hiring they do would not be related to getting all the battery delayed airplanes out the door.
51 7BOEING7 : The airplanes they were delivering just prior to the grounding were going out the door with fewer flights than the first half of last year. December
52 ServantLeader : Boeing's credibility on the 787 program says otherwise. Of course Conner needs to deliver the company line that all's well and move along folks nothi
53 7BOEING7 : Their past credibility does have some issues but if the grounding is lifted in the next couple of months he'll be proven correct.
54 PlanesNTrains : I guess I'm not clear on what you want him to say. "Gee, we have no clue what to expect"? "We won't deliver planes this year"? If the only informatio
55 packsonflight : This statement from Conner is a bit funny: "It is important to recognize that batteries are not used in flight." But still there was an in flight div
56 B777LRF : Or, strictly speaking, the landing gear. I agree with those who say Connor couldn't really say anything apart from what he did, but I do have this sn
57 Sassiciai : I'm surprised so far in all these threads, no-one has asked "Is there a doctor in the house?". Where's Doctor X when you need one? His posts of some y
58 Post contains images Stitch : I'm confident Boeing will assemble 60-70 787s this year. Whether regulatory authorities will allow them to deliver that many is another story... You
59 Sassiciai : Captain X - indeed, thanks for the correction! It was a few years ago! Maybe a Doctor X would be more useful now, with the current issues, as the engi
60 Post contains images hivue : But apparently a functioning APU battery is required for the APU to operate, so if the APU is running in flight then the APU battery is being used. C
61 kanban : I believe we've covered this ad nausium.. the battery is required to start the APU.. and no current is drawn once started.
62 Sassiciai : I thought that this thread was beginning to raise its head from the dire details and opinions about batteries, something that has dragged on for almos
63 rheinwaldner : That is not the point I would stress in Boeings position. Move "really carefull" is the impression the world needs to get. They can have quick progre
64 Post contains links AeroWesty : I wonder how much longer it will take the FAA to review and approve Boeing's proposal. According to the article from FlightGlobal last week, we shoul
65 KarelXWB : The FAA will probably wait until the NTSB release their report on the JAL fire.
66 AeroWesty : That could be months and months. The optimism of the Boeing executives quoted above makes me believe there'll be an interim solution approved.
67 KarelXWB : Sorry, I did not mean the full report. The NTSB will probably release a preliminary report due this (or next) week and the FAA might take a decision
68 AeroWesty : That's what I was wondering. I hadn't seen anything published anywhere other than the limited information in the FlightGlobal article.
69 Post contains links KarelXWB : There is some information available on http://leehamnews.wordpress.com/2013...-preliminary-report-due-this-week/
70 Post contains links Stitch : Leeam.net also notes that Boeing is likely following a similar path that Cessna has done for the lithium-ion batteries that are planned for use on Cit
71 ServantLeader : I would love to see the weight versus safety trade study that so convinced Boeing that Li-ion was the slam dunk choice over Ni-cad -- how did such a m
72 scbriml : Boeing themselves have made it clear, there is no "interim solution". Boeing only has one solution. There is no plan B. If the FAA doesn't approve it
73 AeroWesty : You're correct, I should have been more clear. I was talking in terms of waiting for the final NTSB report above. If there are any further recommenda
74 Aesma : Yes and no. Interim means that at some point a new battery with a new chemistry will be designed and certified for the 787, and I expect that to happ
75 hivue : In the Boeing video linked to in previous parts of this thread Mike Sinnett maintains that the reason Li-Ion was chosen over NiCad was not weight but
76 seahawk : I wonder how the new solution will appeal to the FAA and the customers, as it seems to be designed to only handle a battery failure, not to avoid it.
77 packsonflight : That is only the official story. They can not propose plan A and simultainously say they are working on plan B because plan A is a crap. I am sure th
78 gulfstream650 : Exactly. There seems to be acceptance that the failure is likely to continue to happen. With only 50 aircraft delivered, and as many failures as ther
79 Aesma : That's playing with words. Any common type of battery can meet these requirements, even a lead-acid one, it would just be very big and heavy.
80 ServantLeader : I'm certain there was a laundry list of factors that played into the trade study, capacity, size, weight, safety, maintenance, cost... The point I'm
81 Post contains links Rheinbote : Circuits burned on ANA planes last year, Union says http://www.bloomberg.com/news/2013-0...a-planes-last-year-union-says.html A new twist. May or may
82 sonomaflyer : It would be interesting to know if these "circuit boards" are the same as the panel which caused the UA divert. We've heard allegations of substandar
83 sonomaflyer : However the Airbus design is not the same as the 787 and the decision to switch battery technologies has far less impact on the 350 program than the
84 Post contains links BEG2IAH : Electric brakes are not new and are not unique to B787. http://www.safran-group.com/site-saf...n-electric-brake-scores-world?3270 Excerpt: Electric b
85 ServantLeader : Going to NiCad would mean a complete redesign and 12-18 months to complete and re-everything -- Boeing has little choice but to play the Li-ion hand
86 nomadd22 : I just disposed of a smoking nicad battery. Nicads can and do run away just like lithiums. They just don't get the same press.
87 JHwk : The article you linked specifically states that the first tests were in 2008, the test aircraft was an A340, and the 787 will be the first production
88 Sassiciai : About the electric brakes - with a cascade of failures, engines out, generators out, battery used to start APU, APU now out, RAT deployed, ......... H
89 Stitch : I'm inclined to believe they will not take such a course of action. They have given no indication to Boeing that they will disallow Li-Ion batteries
90 BEG2IAH : The article states this: "Messier-Bugatti was also selected to design and develop the electric brakes for Boeing's new 787 Dreamliner, scheduled to e
91 Post contains links Wisdom : “We can’t say if there was any connection between the circuit boards and the battery, but there have been lots of problems with the electrical sys
92 7BOEING7 : If the thrust reversers are working and you have a fairly long runway (KMWH 32R 13500') you don't even need brakes.(However, if with all the other pr
93 Post contains links KarelXWB : The NTSB just tweeted: http://twitter.com/NTSB/status/309423495530565633
94 sonomaflyer : The Global Hawk is an unmanned drone, not a jetliner certified to carry human beings. The differences are substantial and the certification process d
95 mjoelnir : I think it is just hype all about how impossible it is for Boeing to switch to Ni/Cad. I bet they have a team working on it. But is the reliability of
96 AeroWesty : Hopefully there'll be some pearls of wisdom tomorrow which the FAA may use in determining whether to approve the fix Boeing presented last week.
97 7BOEING7 : I believe the battery only powers the brakes when you're down to RAT power only -- not a simple engine failure
98 sonomaflyer : Once the aircraft lands, the RAT becomes ineffective and the FAA required the battery be able to power the electric brakes to full stop the aircraft.
99 sankaps : My question is even if the FAA approves Boeing's proposed solution, is there a possibility that some airlines (especially the Japanese carriers) and p
100 BEG2IAH : But B787 is certified to carry human beings. It flew thousands of hours and landed thousands of times. I'm not sure how this battery issue makes all
101 7BOEING7 : Okay, I guess by "an engine failure" you meant dual engine failure, however, if the APU is available I believe that would provide power to the brakes
102 AngMoh : I am not completely convinced about the points raised above. First, as long as the root cause is not know, then the solution is not known either. And
103 kanban : I've been trying to place an article I saw that implied Airbus will use Li-Ion on the first three test A/c and the change will be in unit #4. If true
104 Aesma : I'm not arguing that. What I'm saying is that a Li-Ion battery has benefits, it's just not the holy grail that you must absolutely have. If Airbus wa
105 Post contains links 7BOEING7 : Looks like ZA005 could be back in the air soon. Sign off on the certification plan indicates that the FAA is not only happy with the concept but has b
106 ADent : I guessed in an earlier version that the Chinese (and maybe Russians) would cause the most problems. There were 787s ready for delivery waiting for C
107 Stitch : I would expect this is why Boeing is offering stronger containment. We're all assuming that there is a root cause for this issue, but that may not be
108 Post contains links and images PHX787 : For practicality's sake, and for the fact that I can never get a word in here with you guys especially when it comes to news regarding 787 operators,
109 AngMoh : I think the real question is what is different in the 787 - and we can just guess because the details are proprietary to Boeing. I have my personal t
110 PanAmPaul : Interesting interview in the WSJ LaHood Still Has Questions On 787s -http://online.wsj.com/article/SB10001424127887324034804578344831354683720.html
111 AeroWesty : This may present a problem. If the NTSB doesn't come up with a root cause in their update tomorrow, and all Boeing proposed was a containment fix on
112 Post contains links BoeingVista : Boeing 787 Circuits Burned on ANA Planes Last Year, Union Says http://www.bloomberg.com/news/2013-0...a-planes-last-year-union-says.html Something els
113 7BOEING7 : The odds of the NTSB coming up with a root cause at tomorrows briefing is about "10 to the minus 7". The "precise cause of the overheating batteries"
114 2175301 : I assure you that both Boeing and the FAA knows exactly what the NTSB report will say; and I am sure that they had an opportunity to comment on the d
115 YVRLTN : I never got a reply to post 8 - I am not stirring the pot, it is a genuine question - I believe the problem could be as simple as this and I know top
116 ServantLeader : You're basically saying that "the fix is in", which may very well be the case. But since there has been no indication that a root cause has been dete
117 2175301 : You are looking at it wrong. This is not a case of "the fix is in" - its a case where Boeing will have ensured what the FAA is looking for for a fix
118 XT6Wagon : I'm not sure there is any battery technology that doesn't see a self sustaining rise in temp when it suffers from an internal short or other damage.
119 Post contains links and images rheinwaldner : Sorry, interests are not overlapping. They would (get the same press) if they would (be as critical and especially also have frequent thermal runaway
120 Part147 : Stitch I respect your opinions, but just I have to comment on two of your statements above... "We're all assuming that there is a root cause for this
121 seahawk : The improved containment (I would call it a real containment now) is surely a fix to get the planes flying again, but I am not sure all national safet
122 7BOEING7 : The way Boeing stock is up this morning, somebody thinks it will be a good news day.
123 Stitch : And if the FAA truly believed that a cell would never enter thermal runway, they would have been content to allow the use of a plastic container for
124 7BOEING7 : If you takeoff with a dead/missing APU battery you are limited to 180 ETOPS (MEL/DDPG not FCOM). Question is if you are on an ETOPS flight and lose t
125 AeroWesty : Holy moly, $81.50? That's astounding.
126 Post contains links KarelXWB : And here is the NTSB interim report: http://t.co/BeUMF079Hl 547 pages
127 2175301 : No, there is usually a Root Cause (or perhaps 2); but there are cases where there is no root cause. A root cause is an item where by changing that si
128 Stitch : For those interested in the Cliff Notes version: the NTSB has still not identified a root cause. They also announced both a forum and an investigativ
129 BEG2IAH : Again, at least three different sets of electric brakes have been certified for commercial fixed-wing aircraft including Safran (Messier-Bugatti-Dowt
130 Post contains links blrsea : A brief summary has been posted in the news.com article below. Basically, they haven't identified a root cause yet. The following is the executive sum
131 tugger : Thank you for the direct and informative post. Always good to hear from someone who's job and training is in what is being debated. Tugg
132 hivue : Interesting item from the report -- "When smoke is detected, the avionics cooling function is designed to exhaust smoke overboard through fans in the
133 PITingres : True enough, as far as it goes; in flight, other power sources would have been available. I don't know if the on-ground situation was an oversight, o
134 Stitch : And it was the only source of electrical power at the time. In flight, the valve should have multiple alternate power sources to open it (the four en
135 rheinwaldner : There might be not a single root cause, but there is always one or more root causes. Not finding it is something completely different than saying the
136 hivue : It wouldn't be with a failed APU battery. I wonder if the RAT can power the E/E bay vent system? Also, if the fans aren't working in flight I wonder
137 Wisdom : I don't think so. If you stand in front of those vents, they blow your hair away quite hard. So the RAT would not be sufficient if you consider every
138 sonomaflyer : I think the discussion centers around power demand on the battery to stop the a/c in the event of a failure of both engines and the APU (itself a ver
139 Stitch : Boeing already isolated it to a bad production batch.
140 sonomaflyer : To account for the ANA and UA a/c? If so, whew!
141 RickNRoll : The NTSB said they weren't happy that flammable electrolyte escaped, or the heat generated, or the fumes. They clearly felt there was an unreasonable
142 RickNRoll : From the report. "D.3.2 Functional Hazard Assessment: Boeing performed a functional hazard assessment (FHA) as part of their evaluation of the 787-8 E
143 Stitch : And they were right to be unhappy. I'm unhappy about leaking electrolyte and flames, even though I'd fly on a 787-8 tomorrow JNB-PER. But in all thei
144 Post contains links blrsea : Seattle times report on NTSB findings. Says there was no damage to primary structures of the aircraft, only secondary structures. Also says that there
145 BoeingVista : Disingenuous Stitch, as you know the NTSB interim report is a factual report, it does not speculate about anything outside of the actual incident.
146 seahawk : So in the BOS incident the battery did also release flammable electrolytes into the avionics compartment. Not good, as both incidents now fall into th
147 RickNRoll : I think the Seattle Times summed it up in one paragraph. "The safety agency’s interim report shows Boeing mistakenly ruled out any potential causes
148 blueflyer : I'll admit I haven't followed every thread post-by-post because the level is often too technical for me, so apologies if my questions have been asked
149 keegd76 : When they talk about a Model 787 aircraft are we talking about a full-scale mock-up? If full-scale would Thales have had access to such a thing?
150 rheinwaldner : Crossreading the report the following points are useful to clarifiy some of the topics we have discussed here: Page 11: The list of events on the time
151 BoeingVista : This is where the FAA looks culpable, did the certifying authority not look at this and say, ok its a battery what about short circuits? And having d
152 packsonflight : On top of that the battery smoke venting failed when the APU shut down. Looks like the 787 needs a new battery to power the battery failure system...
153 PlaneInsomniac : So, are we talking about a quadruple failure now? Battery fire + venting failure + APU shutdown + faulty indications in the cockpit? If this isn't a r
154 robffm2 : Yes, doesn't look good. And I would guess that before the planed NTSB hearing later this month the FSA will not move at all.
155 BoeingVista : Yes the fire box proposal only deals with the venting failure nothing else, how can the FAA approve return to flight when the other issues remain? Th
156 Post contains links NAV20 : Looks like the opposite is more likely:- "U.S. safety regulators are poised to approve within days a plan to allow Boeing to begin flight tests of th
157 Stitch : The NTSB does not have any authority over the grounding so the FAA could lift it before the hearings. That being said, the FAA looks to be proceeding
158 RickNRoll : I guess it is how you define a 'return to flight'. I think the meaning is, not grounded. Flight testing of course has to happen, otherwise it could n
159 BoeingVista : How were they expecting these nails to get into the containment box? It would seem more logical to short across the busbars as they connect the cells
160 NAV20 : Agree, RickNRoll, that's the basic point. All the evidence so far is that test flights have been 'uneventful.' Meaning that nothing at all went wrong
161 Stitch : I'm pretty sure that a nail penetrating a cell was not a failure scenario, but just a mechanism to generate a short-circuit. Same with baking the cel
162 7BOEING7 : Not exactly true. The smoke venting system is designed for inflight operation--when smoke is detected in either the forward or aft equipment bays the
163 Kaiarahi : Because on that particular test, they were evaluating the effect of a short within a cell, which is also a known failure mode. It wasn't the only tes
164 BoeingVista : Yes. Under-voltage can cause a short that leads to thermal runaway.
165 BestWestern : We really need to stop this "everything is wrong with the 787" nonsense.
166 kanban : agreed... and since such comments are off topic, they could shut the thread downn again.'
167 ServantLeader : Such comments are not nonsense, they are very relevant to the court of public and/or political opinion that Boeing and the FAA have placed themselves
168 Kaiarahi : Under-voltage within the battery (i.e. over discharge) can cause a short. I've never seen anything that suggests that a lower charging rate, in and o
169 Post contains images hivue : The interim factual report seems to me to be implying this, and I believe the NTSB Chairman suggested something similar last month. The facts provide
170 Kaiarahi : I haven't seen that in anything put out by NTSB. They've said consistently that they're reviewing the process to see if the process was appropriate.
171 Post contains links BestWestern : Hold on a second - I was the first person to call a delay on the 787 many many many years back (in 2005) - and was slaughtered for it back then. Are
172 ServantLeader : NTBS would not make such a statement for the sake of idle conversation -- the underlying message is crystal clear.
173 Stitch : And yet Yuasa has stated that their laboratory tests indicated that a power surge outside the battery, or other external problem, started the failure
174 mjoelnir : Yes, it usually does. To fast discharge leads in lithium/ion batteries to thermal runaway. I thing implying that the testing and certifying process f
175 PlanesNTrains : So, just to be clear, has there never been a certified part or system on another airframe that turned out to need correcting post-production? Isn't t
176 7BOEING7 : When the airplane is powered on the ground the vent system is normally on, it does not turn on when smoke is detected. (If it's off on the ground the
177 Kaiarahi : I'd be very surprised if the NTSB had concluded that the certification process was "suspect" before reviewing it. When I'm conducting a lessons-learn
178 ServantLeader : OK, I'll withdraw the term "suspect". The point is that the FAA certification process for the 787 is under the NTBS microscope, and things tend to ap
179 Post contains links hivue : Quoting 7BOEING7 (Reply 179):If it's off on the ground the equipment will overheat. Thanks. That certainly makes sense. But it seems strange that it w
180 7BOEING7 : System is designed to keep the smoke from getting to the flight crew/passengers/cargo--on the ground not a big deal.
181 rheinwaldner : The term undervoltage is a bit misleading here. Because what happened in Boston is not discharging beyond the batteries capacity, which would normall
182 seahawk : If on the ground you can always evacuate. That is no problem. Imho there are 3 minor problems 1. containment not functional 2. APU can not be run with
183 Stitch : Thanks for the clarification. And the voltage drops were minimal (from 32 to 31 volts, then 30, then 29, then back up to 31). Yes, I wonder how that
184 7BOEING7 : #2 is not an issue, same design on the 777. [quote=Stitch,reply=187]Is this unique to the 787's APU? Also, the APU controller went offline at 1021:37
185 sankaps : Andy Pasztor of the WSJ wrote in today's issue reporting on the NSTB report that "Before certification of the 787, Boeing's hazard assessment deemed t
186 hivue : What the report actually says is: "The functional hazard assessment [done by Boeing] identified and classified two hazards associated with the main a
187 hivue : That might have been just a transient as the APU battery self-immolated. Anyway, from the looks of the battery after the event no APU was ever going
188 Stitch : Suppositions should not be treated as facts. Just because the FAA thought a battery fire could bring down a plane doesn't mean it would bring down a
189 sankaps : Read the quote again. It is not just the FAA, it was Boeing itself that believed an inflight battery fire could be a catastrophic failure, but the odd
190 bradmovie : Why does the APU shut down if the battery goes down? IF the aircraft was in an emergency situation, running on just the APU and the battery shut down,
191 Stitch : The Ship's Battery would provide power while the RAT deployed. The RAT would then take-up the load.
192 hivue : Apparently the APU battery is the sole source of power for the APU controller.
193 Stitch : And that is evidently the design of all Boeing Commercial APU systems.
194 7BOEING7 : Because the "brains" that run the APU (the APUC) are powered by the APU battery (same design as 777). Just like cars, when the battery disconnects th
195 sankaps : Yes, but it appears no other Boeing aircraft faced the circular logic solution that requires the APU to vent the effluents of a battery failure, but
196 PlaneInsomniac : Wait, are we second-guessing the FAA and Boeing now? Based on what secret, "better" knowledge that this amateur forum pretends to possess? Or do we h
197 Stitch : Do we know that as a fact. or is this just supposition? Well, NH692 did not crash nor did JL8 suffer damage that would have reasonably shown the plan
198 Wisdom : It is. All other aircraft I know can get the APU started from the main batteries. I still can't figure why they chose this bizar logic of protecting
199 sankaps : I think this is pretty clear from a simple reading of the NTSB report and follow-up comments on the JAL incident. Great question! For JL8, it appears
200 7BOEING7 : What circular logic are you talking about? Inflight the pressure differential carries the stuff out of the airplane as seen in the ANA photos, it wil
201 RickNRoll : Unless I am reading the report wrong, what happened on the ground was a big deal. The bid deal was that Boeing had not predicted this, what happened
202 Stitch : Well evidently Boeing does it that way on every other family going back scores of years... All of which apply only to the 787 and make no mention of
203 7BOEING7 : I guess you're not familiar with the 777 which uses the APU battery to power the electric starter via the APU battery bus. The 777 MEL indicates with
204 7BOEING7 : Not if the APU battery is dead or removed.
205 Stitch : I was thinking "starts from a battery", period, but yes, the Ship's (Main) Battery assists the APU battery in a standard APU start from battery situa
206 7BOEING7 : Boeing airplanes: 747/757/767/777/787 APU and Main battery = Both batteries required for APU start 737 only has one battery (unless you choose the dua
207 kanban : The feeling I've gotten is that in an APU operation on the ground with engines shut down and RAT not operable, the APU battery is required to power t
208 Kaiarahi : Answer: Standard review process - don't draw conclusions before you've examined the evidence.
209 7BOEING7 : The FCOM only indicates that the APUC is powered from the APU battery and I believe in Mike Sinnet's video he mentioned the same thing.
210 Post contains images BoeingVista : It has been established that there was a short in cell 4, this was in the last update. Tested to the point where Boeing were confident enough to decl
211 sankaps : I think the fact that other airplanes do not have a similar thermal runaway and fire risk in the air on on the ground as they do not use similar size
212 Post contains links RickNRoll : Found this blog topic on the battery fire in Boston. Can anyone confirm the technical details? The NTSB interim report into the Japan Airlines 787 bat
213 Post contains links 777ER : New thread FAA Grounds B787: Part 13 (by 777ER Mar 9 2013 in Civil Aviation)
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