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back to article Boeing 787 fleet grounded indefinitely as investigators stumped

Boeing's flagship fleet of 787 Dreamliner aircraft will be grounded for the foreseeable future after a preliminary report from the National Transportation Safety Board (NTSB) said the cause of two battery fires had yet to be found, and that Japanese investigators are similarly baffled. "We have not ruled anything out as a …

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Meh

Grounded indefinitely

Then it is not just a battery problem...........

A design too far perhaps?

I hope not.

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Anonymous Coward

Fry with us

Fry with us to your holiday destination in out new and improved 787, and as an added bonus each flight comes with its own passenger barbecue service.....

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Re: Grounded indefinitely

I don't think you can make that assumption, its more because they can't just go to another supplier... they are custom batteries...

Until they know why & find a solution they can't fly again...

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Boffin

I'd look at the Battery Power Conditioning Circuits

I'm an ex-fuel cell guy, but fuel cells and batteries are two sides of the same coin.Li ion battery's that have been through as much testing as these have, if they start thermally running away when put into service, almost always do so due to an interaction between the charge circuit and the battery resulting in the battery being charged/discharged too fast or overcharged. The cure might be as simple as lowering the maximum charge & discharge current density the power conditioning circuitry allows. Whether that is too low to power all of the entertainment systems, well...

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Re: I'd look at the Battery Power Conditioning Circuits

These batteries don't power anything anywhere near the pax. Galleys and IFE and main (not emergency) cabin lighting is all fed straight off the generators. What the batteries are for are the avionics, flight controls, brakes, etc.

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Re: I'd look at the Battery Power Conditioning Circuits

I agree, mostly because I find it hard to believe a japanese company like GS Yuasa would make substandard battery cells.

Li-Ion at too low voltage or too high voltage will start producing metallic lithium (highly volatile), or starts dissolving the copper current collectors into the electrolyte. This dissolved copper then becomes metallic again when battery voltage is restored to safe levels, and the copper might have formed thin strands acting as shunts. Current across those can locally heat up the cell sufficiently to set off thermal runaway (iirc the required temperature is slightly above 100C). Think of it as chemically "growing" an ignition wire into the insides...

When having multiple cells, each cell must be individually monitored to stay within prescribed voltage limits. In order to not get the entire pack limited by the lowest voltage cell and highest voltage cell, you need some sort of system that either adds more charge to the lowest cell, or removes power from the highest cell. Removing from the highest cell is the most common practice. Then you need to design this balancing system so that it fails in a safe way. Many electrical vehicle hobbyists have been bitten by this, their electronics have failed and a single battery cell has been drained totally dead. Trying to either charge or discharge that pack will then most likely cause a fire.

The charging system needs feedback from this balancing system, so that the charging system doesn't charge faster than the balancing system can remove charge from the highest cell(s). Without that feedback, there'll be atleast one cell that gets overvolted for a brief period of time. The damage accumulates (you can't just say "oops, but it didnt blow up this time, so it's ok")

Same applies to discharge portion, must cease discharging when the lowest cell reaches lowest permissible voltage. Using the pack voltage for this purpose will lead to problems.

I've seen a surprising amount of highly skilled electrical and electronics engineers that have absolutely no clue about batteries, they would blow up a Li-Ion pack quite quickly with the battery management they'd design. Alot of EEs seem to treat batteries as some sort of black boxes that work as electronic fuel tanks and manage themselves. I guess it makes sense, they're electronics people not chemistry people.. Wouldn't surprise me if the problem can be traced back to the battery management system...

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Re: I'd look at the Battery Power Conditioning Circuits

Why in hells sake are people down-voting this?

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Holmes

Re: I'd look at the Battery Power Conditioning Circuits

> Why in hells sake are people down-voting this?

Web monkeys.

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Headmaster

Re: I'd look at the Battery Power Conditioning Circuits

Well, since you ask, it was the use of "battery's" that garnered my downvote.

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Stop

Ignoring the content, fixating on the presentation.

Have a downvote for being a grammar-nazi.

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Re: I'd look at the Battery Power Conditioning Circuits

Individual cell-reversal will cause destructive failure as well. Possible a cell died, began trying to conduct "backwards?"

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Anonymous Coward

Re: Fry with us

I have an old rare photo taken by a guy, while his friends run for their lives, as a Chinook (twin prop) is coming into land on fire.

The rear ramp is down. Flames are blowing out off it's interior like a giant blow torch...

The cock pit is filled with black smoke......

It's about 120 feet up in the air and coming in for a landing and apparently when the blades smash on impact, the pieces can be flung quite a distance.

Hence the guy taking the picture gets the other soldiers in frame as they run for their lives.

It's a really great photograph, of a really, really, bad situation to be in.

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@LarsG - - Re: Grounded indefinitely

"A design too far perhaps?"

Perhaps it's an intrinsic problem with the technology (chemistry). I remember a time a decade or so ago when the operation I was with had to ship these lithium batteries by sea, as they were deemed far too dangerous to even ship by air!

So what happened? Seems to me that this is another instance of where regulators are being forced to compromise safety because of commercial pressures.

BTW, the use of fly-by-wire is the reason for the need for massive backup power—and fly-by-wire is principally an economic consideration. Electronics is my profession so I have a suspicion of electronic systems when used in super-critical environments because of susceptibility to interference, failure etc. The question is why would one substitute a well-understood mechanical system for an electronic one. After all, a mechanical system is one made up of atoms—atoms whose electrons are tightly bound to the nucleus and thus extremely stable. However, in an electronic system electrons are freed from atoms and are subject to the most ephemeral and easily disrupted of all the forces of nature—the electromotive force.

Just recently, in a lecture on the 787 fly-by-wire, I had the chance of putting this question to a group of aviation experts and, after their initial surprise, they essentially agreed that economic considerations were the principal and driving consideration for the change from mechanical controls to electronic fly-by-wire.

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Re: @LarsG - - Grounded indefinitely

I've been a user or raw lithium cells (no protection) since the early days..when fires were very common.

Proper design of chargers, and less flammable chemistry (its the organic electrolyte, nit the 'lithium' that burns) have all but eliminated the risk.

What is strange is that Yuasa hasn't actually seemed to follow these developments.

Or that there hasn't been proper collusion between the charge/discharge protection and the cell types used.

I'd say there's at least a years delay now to redesign and re certify the whole pack/charger/protection block. And possibly retrofit fire equipment.

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Pint

Re: @LarsG - - Grounded indefinitely

Batteries used in Aircraft ELTs (lithium primary cells) are often not permitted to be shipped by air. Think about it.

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Anonymous Coward

Re: Grounded indefinitely

Good to see traditional crappy American engineering screwing them over. Roll on Airbus....

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FAIL

Re: I'd look at the Battery Power Conditioning Circuits

I believe temperatue also plays a role in this. My friendly Li battery expert who provides me with Li batteries for Dive Propulsion Vehicles has charging/load protection to stop the use of the battery when the battery is too cold. Bad stuff happens to Li batteries when they get too cold and once the battery has been frozen, its basically kaput. It is winter in the Northern Hemisphere and I have to ask what temperature cycling is occurring in the belly of an aircraft sitting for extended periods in below freezing conditions while the aircraft is powered down?

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Anonymous Coward

Re: I'd look at the Battery Power Conditioning Circuits

There's me thinking when they designed the batteries they went through extensive testing for this sort of thing....

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Headmaster

@Graham Wilson

After all, a mechanical system is one made up of atoms—atoms whose electrons are tightly bound to the nucleus and thus extremely stable. However, in an electronic system electrons are freed from atoms and are subject to the most ephemeral and easily disrupted of all the forces of nature—the electromotive force

Hope you didn't ask the aviation experts about this. Any conductor has free electrons; that's why it's an electrical conductor (and, to a lesser extent, a heat conductor). Mechanical systems tend to be metallic, and so have free electrons. Look up 'conduction band'. And there's nothing "ephemeral and easily disrupted" about electromagnetism ("the electromotive force"). Look around you - everything you see, every natural phenomena, the form of every physical object - if it's not that way because of gravity, or the strong or weak nuclear forces, then it's that way because of electromagnetism.

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WTF?

Re: @LarsG - - Grounded indefinitely

Airlines prohibit the use of spare batteries in the hold *, so clearly this is a known concern. I would have thought that Boeing would have known about this and taken the correct measures to compensate... but apparently not.

* Of course airlines won't prohibit them completely because they would lose too much business if they outright banned the things. I'm not sure what the logic is of insisting they're in teh cabin rather than the hold. If a battery DOES catch fire i'd prefer if it's NOT in the same space as the passengers. Perhaps because they don't have good fire detection / suppression in teh hold, while in teh cabin it can be dealt with better, whatever the nasty potential effects on the passengers?

Also, what about temperature / pressure? Hold isn't heated so maybe extreme cold can prevent ignition? On the other hand, hold is also not pressurised and could somehow encourage ignition?

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Mushroom

Re: I'd look at the Battery Power Conditioning Circuits

Don't worry, any faults will be fixed in SP1.

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Re: I'd look at the Battery Power Conditioning Circuits

Why such blind faith in Japanese companies?

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WTF?

Re: Grounded indefinitely

"Good to see traditional crappy American engineering screwing them over. Roll on Airbus...."

This would be the same airbus that had an engine explode on a brand new Quantus A380 in flight would it? It was only sheer good luck that the shrapnel didn't hit anything vital that prevented 500 people dying that day.

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FAIL

Re: I'd look at the Battery Power Conditioning Circuits

"Well, since you ask, it was the use of "battery's" that garnered my downvot"

You utter imbecile.

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Rare Photo

Link, or it didn't happen

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Boffin

Re: @Graham Wilson

Graham,

with all respect to your experience and knowledge, I think you can agree with me in saying that an electronic system can be just as thoroughly tested and just as predictable as a mechanical system provided sufficient testing is done on it.

Fly-by-wire has a multitude of other advantages apart from the main one of economy; both in civvies and military aircraft. For civvies think of Airbus and its application of normal and alternate laws to protect against load factor excesses, stalls and improve low-speed stability. In military versions fly-by-wire means that the Eurofighter can actually fly. Its design is for an inherently unstable craft that only become "fly-able" with the aid of computers which results in a extremely agile dogfighter.

Now, back to electronics, there are very specialised FMEA standards that apply to aviation and especially more os on electronics. Which is why by modern standards the electronics keeping the Airbuses aloft would be considered positively neolithic.

In summary, I don't see electronics as inherently more dangerous than any other newly introduced innovation and they should be treated as such i.e. with respect and healthy suspicion until they are proven by life.

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@GW -- Re: @LarsG - - Grounded indefinitely

"—the electromotive force"

...Duh, I meant "electromagnetic force " of course!

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@Displacement Activity -- Re: @Graham Wilson

First, I did mean to say "electromagnetic force", heavens know why I said "electromotive force"—my once lecturers would be horrified (and that error's sometimes a trick exam question).

"Hope you didn't ask the aviation experts about this." Yes, I did actually. I won't bore you with the ins and outs of the discussion except to say that weight/fuel economy is a major/principal reason for fly-by-wire but it's not the only one—another compelling one is that pilots simply like using it (as most of us have become addicted to smartphones). And there's other reasons too.

Right, conductors do have free electrons but also they have 'bound' ones. The reason the table my laptop is resting on remains solid or why one bleeds after having been bashed against a solid plate of conductive steel is because of 'bound' electrons—if you like the electronic structure of matter. I beg to differ with you about the electromagnetic force as it is much weaker than the strong force and operates over a long (theoretically infinite) range subject to the inverse square law. And that's the rub—that the electromagnetic force can induce currents at a distance from the source, apart from being why electrical stuff works, it underpins the reason for the problem of electrical interference. (Signals induced into TV antennae miles from the TV station illustrate the point—here they're wanted but unwanted ones are induced the same way).

Obviously, I'm not opposed to using electronic control systems—after all, that's my profession—but I've seen enough system failures, whether through interference or other electronic faults, to question whether ripping out a perfectly reliable and simple mechanical system only to have it replaced with a complex electronic one is the correct move. Often the answer is 'yes' but the question must be asked. Here's a simplistic illustration of how new problems arise: at present I've an annoying intermittent electronic fault in my car's dashboard and when it fails I lose everything. In older cars that I've owned when the speedometer cable broke, the simpler and less tightly coupled system meant that I still had functioning fuel and temperature gauges.

There's no doubt the electronics/control systems in the 787 are remarkable and a credit to the designers. The keyword here is reliability—key electronics consist of multiple/dual systems that function the same but which are different in design in that they've been designed by different teams/organizations under 'clean-room' conditions.

That said things still go wrong with the best designed electronic systems and sometimes finding glitches, intermittent faults and interference sources—which in the case of aircraft are highly variable as they change their environments—can be incredibly complex, especially in a system as complex as a 787. (Those who've had a PC that has locked up for no apparent reason know the problem.) Moreover, there are other well-publicised instances where electronics, which have replaced critical mechanical (but historically very reliable) systems, that have had electronic failures which have led to serious accidents. For example, it's still unclear why the electronics in the Toyota Prius accelerator failed (anyway, the public is still in the dark).

There's a final reason why I reckon it's important to have fallback in critical systems (here a different technology—mechanical backup), and that's because it's essentially impossible to do a full state analysis (analysing/checking every permutation and combination of operation) on a system as complex as 787. A state analysis on even something as simple as a domestic VCR can fail through its complexity. Here's just one example: I'm aware of a mass-produced VCR with many hundreds of thousands of units in the field where it was eventually found to fail by pressing a certain combination of buttons—but the fault was only found years after it had been released!

Certainly fly-by-wire isn't going to go disappear, but the lesson we should learn is that modern electronic systems are both new (in that we don't have a century or so experience using them), and often they're extremely complex and that sometimes they fail in unpredictable ways—in ways and at times that we least expect.

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Mushroom

Re: Grounded indefinitely

Pot, Kettle, etc?

http://travel.aol.co.uk/2012/05/29/Air-Canada-plane-makes-emergency-landing-after-engine-fails-and-debris-fall/

http://www.dailymail.co.uk/news/article-2017950/Britons-aboard-terror-flight-jet-engine-shoots-flames-30ft-repeated-explosions.html

http://www.nycaviation.com/2011/06/air-new-zealand-engine-explosion-forces-emergency-landing/#.UQbzGPZFDIU

http://en.wikipedia.org/wiki/China_Airlines_Flight_120

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Boffin

Re: Grounded indefinitely

Qantas Airbus 380, yes, but the engine is British - Rolls Royce RB211 Trent 900.

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Re: @Displacement Activity -- @Graham Wilson

I wasn't objecting to your use of EMF; I just put it in quotes because I didn't want to repeat it.

The point of my reply was that free electrons are not a problem. They can't be, because metals are full of them, and you have no problem with mechanical systems. But, you do have a problem with electronic systems, precisely because of the free electrons.

Ok, you may have lots of valid reasons for not trusting electronic systems, but "free electrons" should not be one of them. Besides, in this case, it's Chemistry that's the problem, not electronics.

And I was also pointing out that electromagnetism is not "ephemeral and easily disrupted". And, quite apart from anything else, the actual movement of electrons has pretty much nothing to do with the operation of electronics. That's just something they teach kids in school. Electrons crawl through a conductor - I forget precisely how fast, but maybe a cm a second. But signals propagate across PCBs and ICs at close to the speed of light. Electronics is about electric fields, not electron movement.

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Mushroom

"The aircraft has an inert gas system in the cargo hold to counter fire, but the FAA decided similar systems weren't necessary for other areas of the aircraft."

So, of course, the airlines assumed that fire can only break out in areas with fire extinguishers. Being at 35,000 feet is a tad inconvenient for those folks stuck in the back end.

Those who forget history, are cursed to relive it.

http://www.airdisaster.com/cvr/sr111tr.shtml

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To my knowledge, Inert gas extinguishers, or anything else, will not help much in a lithium ion battery fire. As they burn they produce their own oxygen. With this kind of fire, you just try to keep anything else from igniting and wait for the fire to burn itself out. Note that it took two hours after the firefighters arrived until the fire was out.

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Boffin

iirc alkali metal fires can get hot enough to convert co2 into oxygen and carbon, which is presumably what you mean by "produce oxygen" and you can put them out with salt or sand or a class d fire extinguisher.

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FAIL

SWISSAIR - Peggies Cove

That fire, in your link, was caused by a high end entertainment system that had been added well after initial construction.

If I recall, the equipment was connected to a main bus without the benefit of a circuit breaker, something they teach in Basic Electricity 101.

Ended Swissair and the smaller version is called Swiss.

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"Inert gas extinguishers, or anything else, will not help much in a lithium ion battery fire."

Whilst I agree with this and have on several occasions in my lab career extinguished burning metal & metal hydride fires using special ternary powder extinguishers and whilst noting that these batteries are worst in having their own oxidant the use of inert gas would at least help to control any collateral fires in the vicinity.

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Anonymous Coward

Hello I am your air hostess....

Meal time is over, please hand your salt packets and shakers to the chick with the trolley as she runs past.

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No...

its the electrolyte that burns, not the lithium.

The most high performance electrolytes are in some kind of organic oxygen bearing solvent. In essence an explosive - exothermic decomposition with the release of oxygen amongst other things.

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You have to shut off the charging current as well, if the battery is still being charged the fire won't extinguish until all the fuel has been consumed.

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indeed. Class D fires are sometimes not easy things to control (outside a pot of magnesium). inert gas works fine for non oxidising agents but if the reactant can create its own oxidiser and has already generated heat then smothering with fine powder to try and inhibit the oxidiser is about the best you can get. Wicking heat from one cell to another wont work too well for obvious reasons.

The powders are not exactly lung friendly substances either. You dont want the stuff getting into the air recyclers and being pumped to the cattle.

The obvious approach is to swap the Li cells with NiMH (are you still allowed to make NiCads?)

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Pint

What a mess...

Should've had dual-redundant vendors for that particular LRU.

Oh well, at least it's not software, right? LOL.

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Re: What a mess...

One of Boeing's unique innovations in the 78 was that often the supplier was also responsible for the design of the component.

It saves on a lot of expensive engineers in Seattle - but does make it rather tricky to change vendors.

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Pint

Re: What a mess...

Not really. If Boeing issued an ICD (500+ pages for something like this), then each sub could create their own design that should be perfectly interchangeable. Allow time to bring practice into alignment with this theory.

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Re: What a mess...

They learned better, however. Got the T shirt.

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Anonymous Coward

Shades of "Bugs"

posted theory to Boeing, lets see what they make of that one.

AC/DC 6EQUJ5

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Anonymous Coward

Maybe it is simple

They may be over thinking the cause. It could just be a quality control problem either from the battery manufacturer or the installation at Boeing. The fact that they are having such a hard time pinpointing the cause makes me think the battery fire is part of the symptom and not the source.

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Battries that don't go bang?

There are a few types of batteries that don't tend to go bang with a small fault. Might have been a good place to spend a couple extra kg for safety.

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Re: Battries that don't go bang?

Perhaps this incident will push the industry to focus on LiFePO4 and similar, yes. It's a real irony that A123 Systems went bankrupt just months ago.

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Anonymous Coward

It's much too complex and risky a design, in their rush to produce more efficient lighter planes they've thrown away too many tried and tested things.

Electronics are notoriously less reliable than hydraulics. Which is why your brakes on your car aren't electronic.

When I hear "most advanced" I always think it will also be more likely to have quirks or go wrong. Citroens have been very advanced too and it shows in their re-sale price, Xantia's or XMs were a nightmare.

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"It's much too complex and risky a design, in their rush to produce more efficient lighter planes they've thrown away too many tried and tested things."

Not really. Most of the aircraft is fine, the only big issue seems to be the battery. That *could* be fixed by switching battery chemistry (albeit at the expense of some weight and some space).

"Electronics are notoriously less reliable than hydraulics. Which is why your brakes on your car aren't electronic."

Not so - hydraulic systems are a pain in the arse. Leaks, etc, are a real nuisance. They're only used because you can get a lot of force through small pipes into small actuators that can provide a lot of shove, where electrical equivalents would be significantly bigger (and probably less reliable). The brakes on your car are most likely controlled by electronics.

"When I hear "most advanced" I always think it will also be more likely to have quirks or go wrong. Citroens have been very advanced too and it shows in their re-sale price, Xantia's or XMs were a nightmare."

Fortunately Citroen aren't in the aviation business.

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