Boeing 787 dreamliner : troubles

[Avro]

viewtopic.php?t=17256&start=0 is broken so please continue here

[misako]

Dear Avro,
Thank you for welcome and your comments. Re Glare it would appear that A-380 fuselage is in better shape than B-787 with all cf/epoxy, but that ignores that A-380 all cf/epoxy huge center wing box, so I think that overall, both Boeing and Airbus are on a par, a low par, I note re FST issues I have mentioned. In summary both aircraft have major FST issues that need addressing not ducking by airworthiness agencies.

[misako]

While the certification agencies ponder and ponder re FST and haven't even set a fire standard for exterior structural composites yet to my knowledge, may I suggest a easy, quick and probably effective test, albeit a mite costly. Just land an instumented for interior FST A-380 and a B-787 wheels up on a non foamed dry runway, at close to max gross weight. Now that would reflect real life service conditions and has the virtues of reflecting real life at full scale. Some might protest the cost, but I would cite both have some marginal or rejectable hardware available. And in spite of certain suggestions from friends, please note I have rejected the tempation to specify certain executives as test passengers.
For those remember, back in 80's, ICI claimed total fire suppressing additive and so NASA, to its credit, did a full scale simulated crash test in desert which resulted in first, a massive fire and second, immediate disappearance of claimed ICI system.

[Avro]

I agree with you that doing real scale tests would be ideal, but IMHO there are other ways to perform good tests as well.

It's indeed a pitty that there are no specific regulations on that matter since it's a very important issue during crashes.
However if the manufacturer tests a fuselage section on it's burn through resistance and can show that it is better than the common Aluminium we use since decades I don't see why the new planes should be concidered as unsafer on that matter than before. The planes we fly today are very bad in burn-through resistance and it seems nobody is really worried about that.

To start with the authorities should make a new regulation stating minimum burn-through times, toxicity levels etc....

But as said before for Glare I don't see the problem. For cf/epoxy however I'm not familiar with its fire resistance.

But did you say that the entire fuselage of the B787 will be cf/epoxy composite ? They might encounter some interesting challanges then. I wonder how the fuselage panels will handle the lightning strikes
Oh well, time will tell us. But there are interesting challanges coming in the future for both Airbus and Boeing with respect to the materials used.


Chris

[TexasGuy]

For those remember, back in 80's, ICI claimed total fire suppressing additive and so NASA, to its credit, did a full scale simulated crash test in desert which resulted in first, a massive fire and second, immediate disappearance of claimed ICI system.

I remember, and it was the most expensive test ever for civilian aircraft.

[misako]

Yes, for B-787, the entire fuselage is CF/epoxy, which raises lots of issues, including lightning strike, impact during ground handling, undetected damage, maintenance, QA, et al, but same issues exist for all CF/epoxy center wing box of A-380, although I agree re fire burn through, Airbus in fuselage with GLARE appears to be a mite better off than Boeing in this respect. Also you have to consider very low ignition temperatures of epoxies, HRR and the smoke and toxicity issue as well as just burn through. Best would be for specific and realistic certification regulations, but authorities seem to be lagging there. Finally, expense is there, but so is cost in lives, it's not a cost benefit case for me, but questioning if the certification testing is satisfactory. Remember the fierce fire on the A-340 overshoot in Toronto and that was only the empennage in CF/epoxy. And to save a few bucks, you could always use repired static test item.

[bits44]

Coastcomposites the 787's mandrel manufacturers virtual tour:


http://www.coastcomposites.com/tour.html#

[CX]

I wonder what happens if a pilot tail scrapes the 787... it doesnt' seem to happen (not even A346s) a lot these days but what if?

As for the burn through thing, i'm no expert or anything but how can you make a plane go on fire? And, if somehow you get it go go on fire then even with better burn through materials, people in the plane will still have the same fate anyway... it is about delaying their fate for a few seconds.. The ignition temperature is a more serious issue, i mean if a tail scrape or a lightning strike can set the thing into flames then it is useless..

[Stepha380]

I wonder what happens if a pilot tail scrapes the 787... it doesnt' seem to happen (not even A346s) a lot these days but what if?

Impossible because it is computer controlled.

[Avro]

Yes, for B-787, the entire fuselage is CF/epoxy, which raises lots of issues, including lightning strike, impact during ground handling, undetected damage, maintenance, QA, et al, but same issues exist for all CF/epoxy center wing box of A-380, although I agree re fire burn through, Airbus in fuselage with GLARE appears to be a mite better off than Boeing in this respect.

I don't want sound pro Glare, but Glare has very good properties with respect to the different possible degradations you mention. For Glare a strain rate effect can be observed, i.e. Glare is stronger at a higher strain rate at a higher impact velocity. This means that Glare has some very good properties for high impact velocities.
For smaller velocity impacts and for lightning strikes it has been shown that the internal damage (such as delamination) is smaller in surface then the visible damage from the outside. This enables mechanics to use conventional repair methods which are less costly than to C-Scan the structure after an impact.
As for maintenance, a hybrid structure such as Glare shows again some advantages. First of all the structure is dimensioned with respect to static loadings since the fatigue loadings will be less critical. The fatigue cracks show a slow crack growth which gives the structure a much longer life time than for conventional Al structure. In case the structure needs to be repaired the Glare structure can be riveted with a normal AL patch. This saves costs and maintenance procedure. Furthermore the Glare + Al patch will show very good fatigue properties and will fail way after the Al+Al patch structure we use today. For corrosion however Glare will be more like Al. But since the AL layer is very thin it will have slightly better properties. The thiner Al layer will namely have a higher quenching rate which is benefical for corrosion.

Glare or hybrid materials are really good materials and I wonder why Boeing didn't chose Glare or another hybrid material instead of Cf/epoxy composite which will give them much more issues. Glare is still improved through research and the A380 number 50 (or 60 in don't remember) will have a different kind of Glare which will save some additional weight.

On a side note I really hope that Airbus will chose for Glare on the new A350/A370 instead of the Al-Li option which is pure nonsense IMHO. They just add some Li to save some weight.

This being said I'm really interested to see the outcome of the CF/epoxy in the B787.

Does someone know whether the cf/epoxy can be repaired with simple riveted Al patches ? or do we need complex and expensive maintenance methods ? How about inspectablility ?

I wonder what happens if a pilot tail scrapes the 787... it doesnt' seem to happen (not even A346s) a lot these days but what if?

That should be taken into account when dimensioning the part which could be dragged onto the runway following a tail strike. I don't expect more troubles there than for other parts of the structure. It's simple damage tolerance of the cf/epoxy which should be well known.

As for the burn through thing, i'm no expert or anything but how can you make a plane go on fire? And, if somehow you get it go go on fire then even with better burn through materials, people in the plane will still have the same fate anyway... it is about delaying their fate for a few seconds.. The ignition temperature is a more serious issue, i mean if a tail scrape or a lightning strike can set the thing into flames then it is useless..

Burn through properties are very important for post crash fires. That's the main prupose. Many people survive some crashes but cannot escape fast enough because of the fire and the intense heat it generates. After the 90 seconds inside an Aluminium skin you won't have a lot of surviving chances. If you have a Glare skin however it won't burn through for a long time and the inside temperature will rise at a much slower rate

As for a lightning strikes, it shouldn't ignite a fire. There is some intense heat disspitated indeed but the airframe should be able to sustain those kind of damages, otherwise it won't be certified. Keep in mind that an aircraft is hit on average once per year by a lightning strike. It would be unacceptable to have the plane go on fire each time it is hit

Impossible because it is computer controlled.

yeah that's what they say. The risk zero doesn't exist. Wasn't the B777 supposed to have a computer system taking tail strikes into account as well ? Well a couple of years ago a B777 had a major tail strike in Zürich !!!

Never say never

Chris

[CX]

Never heard of Glare but it sounds good, but sadly there has been no rumours no nothing about Airbus using something other than Al-Li for its A370 fuselage, hopefully there will be a surprise!

[earthman]

Perhaps they can use Al-Li instead of Al in Glare?

As for lightning strikes for CF/epoxy, I seem to recall that they needed to add metal strips to the structure for that purpose.

Also, read about the Super Puma crash in the North Sea, which is on National Geographic once in a while. It got struck by lightning in the tail rotor, and the thing practically exploded due to the intense heat generated on the interface between the glass fiber rotor blade and a metal strip on the leading edge of the blade. The damage for a metal blade would be much less, if any at all.

[Avro]

Never heard of Glare

Glare is a hybrid material, which means it's a composition of a composite and a metal material. In Glare you have Aluminium Layers with inbetween layers of Glass fibres imbedded in an epoxy matrix.

As for lightning strikes for CF/epoxy, I seem to recall that they needed to add metal strips to the structure for that purpose.

Right ! I totally forgot about that this morning. That's what they also do on the nose cones of airplanes since they are not conducting materials. So simply electrically bond some metal wires.


Chris

[Stepha380]

Not really related to 787, but lots of people have underlined the loss of revenue due to the A380 delays. But Boeing has also some problems between settlements and delays. I recognize the article is quite long but please go through before adding comments, it will avoid confusion

http://www.chicagotribune.com/business/ ... siness-hed

It seems that Boeing has problems building small airplanes not exactly what Randy Said last time.
http://www.boeing.com/randy/archives/20 ... lanes.html

[PYX]

Not really related to 787, but lots of people have underlined

Totally un-related in every way, so why was it posted to this thread?

[Stepha380]

why was it posted to this thread?

Firstly because there is no need to create 100000000 threads, secondly because we will see what Boeing will do to deliver the 787 on time to regain some credibility.

[CX]

I think the biggest threat to 787's schedule and 2008 entry-in-service is the outsourcing of everything... enemy working with enemy sometimes simply doesn't work, or at least it won't work straight away..
Technical stuff like the composite fuselage is not a worry imo, they had so much research done, but whether the whole plane will live up to its specs is another issue..

[earthman]

Just wait for the first part being produced to specs using inches, while the specs were in cm. Or the other way around.

[Stepha380]

The risk zero doesn't exist. Wasn't the B777 supposed to have a computer system taking tail strikes into account as well ?

On Airbus aircraft, computer is always the boss. (for the best or the worst), no idea for Boeing's.

[Avro]

The risk zero doesn't exist. Wasn't the B777 supposed to have a computer system taking tail strikes into account as well ?

On Airbus aircraft, computer is always the boss. (for the best or the worst), no idea for Boeing's.

Well you have the hard and soft limits. But certain actions aren't allowed whether you fly in a very modern Airbus or a very modern Boeing. Anyway, all I wanted to point out is the fact that you should nevertheless take into account a possible tail strike as structural damage even if the computer will prevent it. That's why I said the risk zero doesn't exist. But that's another story

Now to come back on the topic of the troubles with the voids found in the composite skin. Has someone any idea of the impact in percentages those voids have on the strangth of the composite ?

Boeing will probably not be able to remove all the voids of the produced skins in the future. The solution will be in my opinion to try to take into account the scatter of the produced material by and subsequently dimension your parts. However this might result in larger safety margins and thus a heavier structure.


Chris