zvezda
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 12:29 pm

Quoting Astuteman (Reply 80):
I don't believe that a non-circular thin-walled pressure vessel is capable of maintaining its shape under internal pressure without frames.

A thin-walled double-bubble joined at floor beams held in tension is capable of maintaining its shape under internal pressure without frames. The A350 and 787 cross sections appear to be very close approximations of double-bubbles.
 
787engineer
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RE: A350XWB - Back To The Drawing Board (again) Pt

Sat Jun 02, 2007 2:33 pm

Quoting CygnusChicago (Reply 97):
f Airbus already has the technology, and has experience with it on the A380, why wouldn't they give the A350 a composite frame?

AFAIK the A380 doesn't have composite frames. . . and who says they have the technology? It's one thing to have a supplier be able to build composite frames, it's another to design a composite frame for the supplier to build.

Quoting CygnusChicago (Reply 67):
If I am not mistaken, the majority of the 787 frames are manufactured by a company called Zodiac and are resin film infused braided frames. The rest of the frames are titanium.

IIRC, Vought sub-contracted the frames in their sections (47 and 48) out to Northwest Composites in Marysville, WA (not too far north of Boeing's Everett plant). I think Northwest composites was bought by Zodiac in early 2005. I would hardly call sections 47 and 48 "the majority" of the airplane in any way. I think it was also Northwest Composites that originally got that portion of the X-45 project.

Quoting CygnusChicago (Reply 67):
Zodiac has some commercialization patents on airplane frames, so they can conceivably subcontract to Airbus. However, since the commercialization of this technology was funded by the US military, they may not be allowed to.

Considering Vought was able to sub-contract to Northwest Composites for the technology for a commercial purpose, I doubt the US military or the US government would not allow it. I think that Zodiac can subcontract out to Airbus, and there are a plethora of reasons why they haven't. Maybe Zodiac doesn't have the capacity to supply frames for the 787 as well as the A350; maybe Airbus isn't willing to fork over the money for Zodiac to build new plants and increase capacity. Not saying this is true or not I'm just throwing out a possibility.

References:
Vought subcontracts to Northwest Composites, now C&D Zodiac
http://www.compositesnews.com/cni.asp?ArticleID=6994
http://www.voughtaircraft.com/newsFactGallery/releases/2005/101705.htm
Northwest Composites and X-45
http://www.compositesworld.com/hpc/issues/2004/May/463/3

Edit - added references

[Edited 2007-06-02 07:38:03]
 
WingedMigrator
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 2:55 pm

Quoting 787engineer (Reply 101):
AFAIK the A380 doesn't have composite frames. . .

It does have a handful of resin transfer molded composite frames in section 19 (the unpressurized tail) according to Norris & Wagner's book on the subject.
 
astuteman
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 3:53 pm

Quoting Poitin (Reply 90):
Now you see why I was asking about it. Nice to know who to ask for the numbers

He's where I always go to for this type of stuff now, too  thumbsup 

Quoting Gatorman96 (Reply 92):
As I know nothing about the engineering side of wings, can you explain what you see that makes the A350's wings so much better?

My question too - is it possible to elaborate on this, Kaneporta1?

Quoting WingedMigrator (Reply 102):
It does have a handful of resin transfer molded composite frames in section 19 (the unpressurized tail) according to Norris & Wagner's book on the subject

And also some in the decks and wings IIRC.

Regards
 
Areopagus
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 5:53 pm

Quoting BlackKnight (Reply 87):
I must not be being clear enough. If I have the option to buy a 787 which last for 30 years (est. value floating around) or a A350 which lasts for 15 years (just for reference) it means I will have to buy another plane in 15 years to replace it versus 30 for the first. So for the A350 to be priced competitive it would have to be half of the already fare market price of the 787 for I would need to buy 2 for 1 of the 787.

That analysis ignores:
  • the time value of money. The present value of an airplane to be delivered 15 years in the future is lower than one delivered today.
  • the fact that the airplane to be purchased 15 years later will be more efficient.
 
astuteman
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 6:52 pm

Quoting NAV20 (Reply 99):
Astuteman, according to that interview with Leahy I posted aerlier, the reverse would still appear to be true; you can still get a 787 earlier than you can get an A350, you will have to wait for the latter:-

you don't say  Yeah sure  Wink
Probably a good reason why the impending explosion of A350 orders hasn't happened yet  Smile

I used the "later avaialbility" of the 787 as an example of a reason for buying an A350, even if it was 1% or 2% more expensive to operate, not as a fact.......

BTW, I'm serious about the A350 acceleration.
We can argue some semantics about whether it's quite as good as the equivalent 787, but the fact remains that, even if the A350 sceptics are right, it will still be WAY better than any other widebody twin around, excepting the 787.

Regards
 
Joni
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 7:21 pm

Quoting NAV20 (Reply 46):

The pattern that seems to be developing is that we can rely on Boeing management never to miss an opportunity to stay ahead of the game, and rely equally on Airbus management never to see what's coming until it's too late.

This reminds me of how Boeing lost their dominant market-share position to an upstart Airbus. Indeed ahead of the game.

Quoting SEPilot (Reply 57):
The end result is that the A350 will still have a fatigue limited life, while the 787 will not. This is potentially huge

If the A350's life is "fatigue-limited" because of this to 150 years and the B787's to 350 years (for example), the difference isn't likely to be relevant. I know you'd like for it to be relevant  Wink

Quoting TeamAmerica (Reply 65):

Given that, the B787 frames are CFRP. I would not assume that means that all of the interior structure of the Boeing fuselage is CFRP. As Astuteman points out, there's likely to be some metal in there as well.

True, and just looking at Boeing's website they state that only 50% of the primary structure is composite, by weight, so there's a whole lot of metal in there.

Quoting CygnusChicago (Reply 67):
This leads to an interesting question. The basic patents covering the process are owned by a UK university.

Is this true? If so, they could sue Zodiac and Boeing for patent infringement. However I suspect any such patents have either expired or let lapse by now. (this also depends on how the patents have been written and in what ways the technologies have been developed further in the US).

Quoting SEPilot (Reply 84):
It comes down to my previous point; what does the A350 offer that is better than the 787 and worth waiting for?

According to Airbus the A350 offers, among other things, lower OEW/seat and better economics. However these are to be established in actual practice. As Reply 99 quotes, Airbus knows that the A350 has to have a sufficient margin over the B787 in order to make waiting for it worthwhile.
 
NAV20
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 7:42 pm

Quoting Joni (Reply 106):
If the A350's life is "fatigue-limited" because of this to 150 years and the B787's to 350 years (for example), the difference isn't likely to be relevant.

Discussion on this point seems to be getting ever more convoluted.

When buying (or even evaluating) any aeroplane, the accountants will prepare estimates of annual depreciation and maintenance costs, and those figures will be included in the estimates of annual operating cost.

So, from Day One of ownership, the operating cost of an aeroplane that is expected to last longer, require less maintenance, and have a higher resale value will be lower than those of an aeroplane lacking those advantages.
"Once you have flown, you will walk the earth with your eyes turned skywards.." - Leonardo da Vinci
 
zvezda
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 8:00 pm

Quoting Astuteman (Reply 105):
the fact remains that, even if the A350 sceptics are right, it will still be WAY better than any other widebody twin around, excepting the 787.

No need to limit that to twins. At the time of the A350's EIS, the A350 and 787 will be far better than any other widebodies. Full stop.
 
sabenapilot
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 8:03 pm

Allow me to try to steer this discussion into more diverse waters by saying people are way too much focusing on the fuselages of both planes, whereas there are other domains which are worth some attention.

The reason there is so much focus on the 'coffee pot' look of the 787 is that Boeing's PR department has done a good job (at least the second time round) in finding the technological differentiators they were ordered to focus on to promote the 787 as being truly state-of-the-art in an efford to restore confindence in their capabilities after the 767-4ER and Sonic Cruiser fiascos. They first tried the bleedless engine concept (which in fact isn't bleedless at all) because they felt engines would be most easily seen as centers of technological improvement, yet that attempt failed and they then changed their attention to the so called "monolithic" carbon fuselage barrels which are in fact far from monolithic either, but contrary to the "bleedless engines" there are no closely involved neutral partners like on the engines to shoot that hot air balloon out of the air and so it has caught on with the public.

Whereas the 787 definitely has a very innovative fuselage design, the overall advantages of it having a barrel approach over the shell approach are greatly overrated as they are very very modest (not even a single percentage point in OEW and be assured once the maintenance procedures for the XWB will be finished also in maintenance costs), yet there are other domains of the 787 design where there definitely was room for Boeing to make more use of the latest technological innovations, the WINGS being one of them.

Boeing obviously likes to put the spotlight on its new fuselage design, yet it have been clear by now they remain very quite over their wing design and allow me to give away the reason for that: it is because the 787 has a very conventional wing design.

Airbus superiority when it comes do designing wings is known for long (Concorde wing, A320 wing, A330/A340 common design, A380 wing), so Boeing took the safest way with the innovation used for the 787 and went as far as possible with it, hence the barrel approach for the composite fuselage: nice, but non essential really when you know that an innovative wing design is much more essential to a plane. In the end, the first task of a plane is not to be efficiently maintained, but to fly efficiently and that can more easily be done on innovative wings, not on innovative fuselages.... However, you have to be capable to choose the domain you innovate on...

As more of the XWB's design and its all composite wing will become known, people will come to understand that Airbus has not only done a trade off study on barrel vs shell, but also looked at the wider picture to see whether it wouldn't be wiser to try to break into new grounds through the wing design and opt for a slightly less challenging fuselage design.
 
bigjku
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RE: A350XWB - Back To The Drawing Board (again) Pt

Sat Jun 02, 2007 8:50 pm

Quoting Sabenapilot (Reply 109):

Whereas the 787 definitely has a very innovative fuselage design, the overall advantages of it having a barrel approach over the shell approach are greatly overrated as they are very very modest (not even a single percentage point in OEW and be assured once the maintenance procedures for the XWB will be finished also in maintenance costs), yet there are other domains of the 787 design where there definitely was room for Boeing to make more use of the latest technological innovations, the WINGS being one of them.

This has come up twice, if someone would like to talk about what exactly this wing problem is that would be more informative than simply saying the wing is not advanced enough.

Quoting Sabenapilot (Reply 109):

Airbus superiority when it comes do designing wings is known for long (Concorde wing, A320 wing, A330/A340 common design, A380 wing), so Boeing took the safest way with the innovation used for the 787 and went as far as possible with it, hence the barrel approach for the composite fuselage: nice, but non essential really when you know that an innovative wing design is much more essential to a plane. In the end, the first task of a plane is not to be efficiently maintained, but to fly efficiently and that can more easily be done on innovative wings, not on innovative fuselages.... However, you have to be capable to choose the domain you innovate on...

Didn't Airbus end up having to bolt some junk onto the early A340 wings because they screwed up the design and it was not holding up as well as they thought it would?

Didn't the A380 wing break too early during test and have to have more structure added to it?

I find it odd that these wing designers who are obviously so great would have problems like that since as you imply they obviously produce a vastly superior wing for every aircraft they build.

Again I will ask, what is so innovative about the A350 wing vs the 787 wing since you supposedly have let the cat out of the bag...
 
MD-90
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 9:23 pm

Quoting Sabenapilot (Reply 109):
Airbus superiority when it comes do designing wings is known for long (Concorde wing, A320 wing, A330/A340 common design, A380 wing)

Concorde was a fantastic achievement, but I've never read that Airbus has superiority over Boeing in wing design. Indeed, I remember an article that quoted a Boeing engineer, with the faintest hint of wonderment, saying that Airbus didn't do the aerodynamic analysis of each individual flap track fairing on the A330/A340 wing, but instead just faired each one back enough to do the job (sounded strange to me). Apparently in that regard Boeing does more extensive analysis, I suppose.

I think the far bigger story is how much of the 787's wing was subcontracted out to Japanese partners. Boeing has historically jealously guarded their wing designs like Coke protects its famous formula for Coca-Cola.
 
zvezda
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 9:35 pm

I suspect the next generation of wings (Y1/NSR) will be designed by computers using evolutionary algorithms. In other words, the computers make random mutations and retain those which improve weight, fuel capacity, L/D, speed, etc. as predicted by simulation. Limiting parameters would have to be set, like max wingspan, min ground clearance, et al. Of course, anything not obvious to the human aerodynamic engineers watching the process would have to be verified in the wind tunnel.
 
NAV20
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 9:35 pm

As far as i know the 787 wing is a direct result of Sonic Cruiser research - and is therefore 'thinner' in both senses than previous wing designs (i.e. thinner aerofoil section AND higher aspect ratio). It is therefore the main reason for the 787's expected better cruise economy compared to old-fashioned designs.
"Once you have flown, you will walk the earth with your eyes turned skywards.." - Leonardo da Vinci
 
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Stitch
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 9:47 pm

I do agree that the barrel vs. panel debate is similar to "how many angels can dance on the head of a pin?" - at least until the A350 takes to the skies herself and a more direct comparison can be made.

However, despite the ...interesting...points Sabenapilot had made, evidently the airlines don't get "the big picture" since they consistently choose the 787 over the original A350, even though that also had Airbus' patented "Wonder Wings" in it's later variants and "safe and sane" bleed-engine technology...
 
Poitin
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RE: A350XWB - Back To The Drawing Board (again) Pt

Sat Jun 02, 2007 11:00 pm

Quoting SEPilot (Reply 95):
Quoting Poitin (Reply 93):

We may well have stumbled on to something to watch for. We might even seen a new TV show "FLIP THAT PLANE" in which the go through they deal of the week. Might be real interesting

I'm sure all A-netters would watch it avidly, but are we enough of an audience to make it worthwhile? I can just envision the utensils I would have to dodge if I suggested to my wife that we watch it... duck

Well, we could broadcast it on the internet -- that way you can sneak off and watch it while pretending to be A.netting.

Quoting NAV20 (Reply 107):
Quoting Joni (Reply 106):
If the A350's life is "fatigue-limited" because of this to 150 years and the B787's to 350 years (for example), the difference isn't likely to be relevant.

Discussion on this point seems to be getting ever more convoluted.

When buying (or even evaluating) any aeroplane, the accountants will prepare estimates of annual depreciation and maintenance costs, and those figures will be included in the estimates of annual operating cost.

So, from Day One of ownership, the operating cost of an aeroplane that is expected to last longer, require less maintenance, and have a higher resale value will be lower than those of an aeroplane lacking those advantages.

This is true. While there was some surprise when the A320 turned out to be a 25,000 cycle plane, that was still good enough and it is still selling. The big difference between the 737 and A320 is the upfront cost and the residual value of the plane. According to Stitch, they have a very similar ASP of $42-43 million. While the 737 probably has a better resell price, the A320 is still worth a pile of money when converted into a pile of parts. Both are aluminum structures and probably have about the same maintenance cost per hour of flight. This it is not surprising that they just about share the market 50-50.

Even though Airbus has apparently slashed the ASP of the A350 to match that of the 787, the 787 will undoubtedly have a higher residual resell price. The real big difference in the 787 and A350 is that the A350 is going to have more maintenance. As Tim Clark has stressed that he is "sold on the 787's 40% reduction in maintenance," something not possible with an aluminum frame.
http://www.atwonline.com/news/story.html?storyID=9009

We are going to simply have to wait and see if the A350 sells to airlines that are run like a normal business. So far both SU and QR are more likely politically motivated, while SQ is obviously looking at the the plane at a really good price. Even then it is interesting to see that they have not firmed their MoU. As for AY, Finnair has always marched to their own drummer.

Perhaps the Paris Airshow will shed some light on the A350's prospects.
Now so, have ye time fer a pint?
 
NAV20
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 11:09 pm

Quoting Poitin (Reply 115):
As Tim Clark has stressed that he is "sold on the 787's 40% reduction in maintenance," something not possible with an aluminum frame.

Hadn't realised until now that the difference was as much as 40%, Poitin. That's the sort of difference that the accountants would say was 'considerable,' you and I would call 'bloody big,' and the admen would say was 'colossal.'  Smile
"Once you have flown, you will walk the earth with your eyes turned skywards.." - Leonardo da Vinci
 
slz396
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 11:10 pm

Quoting BigJKU (Reply 110):
Didn't Airbus end up having to bolt some junk onto the early A340 wings because they screwed up the design and it was not holding up as well as they thought it would?

Never heard of that...

All I know is the A340 has EXACTLY the same wing as the A330, so maybe the 'junk' you are referring to are the pylons for the 2 outboard CFM56 engines, which through their weight allow the wing to carry more fuel in its inboard fuel tanks, giving the A340 more range than its twin sister the A330?

Quoting BigJKU (Reply 110):
Didn't the A380 wing break too early during test and have to have more structure added to it?

Yep, at roughly 148% of the required load and Airbus added about 7kg of reinforcements to solve the problem.

What is better you think: Design right to the edge and then finding out through static testing you have to add basically a few pounds to match the calculations, or overdesign and proudly announce your wings can take 160% of the load????

Quoting Zvezda (Reply 112):
I suspect the next generation of wings (Y1/NSR) will be designed by computers using evolutionary algorithms. In other words, the computers make random mutations and retain those which improve weight, fuel capacity, L/D, speed, etc. as predicted by simulation. Limiting parameters would have to be set, like max wingspan, min ground clearance, et al. Of course, anything not obvious to the human aerodynamic engineers watching the process would have to be verified in the wind tunnel.

Maybe this has something to do with it?

http://www.airbus.com/en/presscentre...9_Numerical_Simulation_Center.html

Does anybody know if the 787 will have an all composite wing and just how that will be built?
If yes, just how 'monolithic' will the 787 wing be compared to that of the A350?
If not, why isn't it all composites like on the A350? And what are the weight consequences?
Interesting point brought up by Sabenapilot and Kaneporta1 indeed! Thanks.
 
Poitin
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 11:17 pm

Quoting NAV20 (Reply 116):
Quoting Poitin (Reply 115):
As Tim Clark has stressed that he is "sold on the 787's 40% reduction in maintenance," something not possible with an aluminum frame.

Hadn't realised until now that the difference was as much as 40%, Poitin. That's the sort of difference that the accountants would say was 'considerable,' you and I would call 'bloody big,' and the admen would say was 'colossal.'

I am not sure that it is 40%, but Tim Clark thinks so, but what does he know? Big grin

While I do not know why Airbus is continuing to stay with the Aluminum frame and composite panels, it may well turn out to have been a big mistake.
Now so, have ye time fer a pint?
 
OldAeroGuy
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 11:19 pm

Quoting Sabenapilot (Reply 109):
Airbus superiority when it comes do designing wings is known for long (Concorde wing, A320 wing, A330/A340 common design, A380 wing),

Given the Airbus superiority in wing design, how do you explain the lower long range cruise speed of the A340 (all models) compared to the 777? The 0.01 to 0.03 difference is more than can be explained by the 0.4 to 1.5 degree greater sweep of the 777.

Quoting NAV20 (Reply 113):
As far as i know the 787 wing is a direct result of Sonic Cruiser research - and is therefore 'thinner' in both senses than previous wing designs (i.e. thinner aerofoil section AND higher aspect ratio).

Actually, the focus of transonic airfoil development is thicker airfoil sections that allow the same cruise Mach performance as thinner conventional sections. The thicker sections allow span increases (higher aspect ratios) without paying a structural weight penalty.

[Edited 2007-06-02 16:39:18]
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
MD-90
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 11:23 pm

Quoting Zvezda (Reply 112):
I suspect the next generation of wings (Y1/NSR) will be designed by computers using evolutionary algorithms. In other words, the computers make random mutations and retain those which improve weight, fuel capacity, L/D, speed, etc. as predicted by simulation. Limiting parameters would have to be set, like max wingspan, min ground clearance, et al. Of course, anything not obvious to the human aerodynamic engineers watching the process would have to be verified in the wind tunnel.

Does useable software with those capabilities exist?

Quoting BigJKU (Reply 110):

Didn't Airbus end up having to bolt some junk onto the early A340 wings because they screwed up the design and it was not holding up as well as they thought it would?

I believe you're thinking of the vertical tail, which was reinforced? (but saying they 'screwed up the design" is overly harsh, imo).
 
baroque
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 11:24 pm

Much of this thread seems to assume an almost infinite life for the resin-derived polymers in (all) composites. Ageing appears to be most marked at the surfaces and can be influenced by moisture. As far as I can work out, most tests are carried out at higher temperatures with an assumption being made that rates of change follow an Arrhenius relationship, although that begs the question of what the rate constants are. But how long do stressed composites actually last in the field, and how good are methods of detecting loss of strength?

If this has been discussed to death somewhere else, sorry for the question!
 
NAV20
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 11:28 pm

Quoting Slz396 (Reply 117):
Does anybody know if the 787 will have an all composite wing and just how that will be built?

Hi, Slz396. No need to use the future tense, the 787 wing is in production, see the video I linked to in Post 99 and you can judge for yourself how it was built. AND do the same for all the OTHER 787 parts.

Quoting Slz396 (Reply 117):
Interesting point brought up by Sabenapilot and Kaneporta1 indeed! Thanks.

Which points were those?They appear to be claiming that when the A350 wing is produced (in what, three years' time?) it will be better. But they don't say why?
"Once you have flown, you will walk the earth with your eyes turned skywards.." - Leonardo da Vinci
 
bigjku
Posts: 1906
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 11:30 pm

Quoting Slz396 (Reply 117):
All I know is the A340 has EXACTLY the same wing as the A330, so maybe the 'junk' you are referring to are the pylons for the 2 outboard CFM56 engines, which through their weight allow the wing to carry more fuel in its inboard fuel tanks, giving the A340 more range than its twin sister the A330?

They had to add an addition that was primarily for aerodynamic purposes. A plastron or something similar.

Quoting Slz396 (Reply 117):
Yep, at roughly 148% of the required load and Airbus added about 7kg of reinforcements to solve the problem.

What is better you think: Design right to the edge and then finding out through static testing you have to add basically a few pounds to match the calculations, or overdesign and proudly announce your wings can take 160% of the load????

I get that and its all well and good, I am just curious where this notion that Airbus has these wing designing gods and Boeing has Billy Bob and his brother Ray putting wings together is coming from. I have still yet to see someone explain the "obvious" superiority of the A350 wing over the 787 wing other than conjecture.
 
bigjku
Posts: 1906
Joined: Sat Feb 17, 2007 10:51 pm

RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 11:35 pm

Quoting MD-90 (Reply 120):
I believe you're thinking of the vertical tail, which was reinforced? (but saying they 'screwed up the design" is overly harsh, imo).

I agree they probably did not screw up but they made changes because the initial design was less than optimized. Additionally they added weight to the A380 wing because it was not quite strong enough. It was really only meant to point out that perhapse the Airbus people are not designing these vastly superior wings.
 
zvezda
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 11:36 pm

Quoting Slz396 (Reply 117):
Maybe this has something to do with it?

It's not the same thing, but extremely fast simulations are needed for evolutionary algorithms to be practical.

Quoting MD-90 (Reply 120):
Does useable software with those capabilities exist?

Yes, but computers are probably not yet fast enough and cheap enough to design something as complex as a wing using evolutionary algorithms. So far, it has been used for simpler designs. However, computational power is doubling about every 18 months.
 
Wsp
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RE: A350XWB - Back To The Drawing Board (again) Pt

Sat Jun 02, 2007 11:37 pm

Quoting NAV20 (Reply 116):
Hadn't realised until now that the difference was as much as 40%, Poitin. That's the sort of difference that the accountants would say was 'considerable,' you and I would call 'bloody big,' and the admen would say was 'colossal.' Smile

The difference is compared to previous aircraft construction methods not the A350.

Quoting Poitin (Reply 115):
As Tim Clark has stressed that he is "sold on the 787's 40% reduction in maintenance," something not possible with an aluminum frame.

The latter part tells us that supposedly the maintenance reduction of the A350 will be less than 40%. Combined with Airbus' press release stating that there is some reduction we can assume that the maintenance reduction for the A350 construction method is above 0 and below 40%.

There is no way to deduce any meaningful conclusion from these statements. NAV20, you may have to hold off your victory celebrations for a little more.


P.S. Boeing claims only 30% over whatever:

http://www.boeing.com/commercial/787family/programfacts.html

Quote:
Anticipated maintenance savings
30 percent
 
NAV20
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 11:45 pm

Quoting Baroque (Reply 121):
Much of this thread seems to assume an almost infinite life for the resin-derived polymers in (all) composites. Ageing appears to be most marked at the surfaces and can be influenced by moisture.

Baroque, the crucial question (ever since the Comet 1) is how long a fuselage can stand up to repeated pressurisation/de-pressurisation. Most aluminium aeroplanes get retired after say 40,000 pressurisation 'cycles' because the risk of failure through metal fatigue a' la Comet 1 becomes too high. The authorities are pretty conservative on the point - aeroplanes are not allowed to exceed more than half the cycles they successfully achieved in testing.

Composites are believed not to suffer from fatigue beyond a certain point - they reach a 'fatigue floor' and don't deteriorate any further beyond that point. So if Boeing care to test the 787 fuselage to say 200,000 cycles, they OUGHT to be able to get the 787 certified for say 100,000 cycles (more than twice the level any pressurised ali aeroplane has achieved so far).

That's not to say composites won't eventually wear out. But I happen to be intimately acquainted with a fairly 'elderly' composite boat and it shows absolutely no sign of anything you could describe as 'wear' so far. Wear on the fasteners required in aviation is another question - but Boeing may have largely sidestepped that problem (at vast expense) by using titanium for the key 787 fasteners.

[Edited 2007-06-02 16:52:40]
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Poitin
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 11:48 pm

Quoting MD-90 (Reply 120):
Quoting Zvezda (Reply 112):
I suspect the next generation of wings (Y1/NSR) will be designed by computers using evolutionary algorithms. In other words, the computers make random mutations and retain those which improve weight, fuel capacity, L/D, speed, etc. as predicted by simulation. Limiting parameters would have to be set, like max wingspan, min ground clearance, et al. Of course, anything not obvious to the human aerodynamic engineers watching the process would have to be verified in the wind tunnel.

Does useable software with those capabilities exist?

For years and years at Boeing, and I assume elsewhere too, except they don't make random changes, but carefully stepped ones, with all the permutations done. This is trivial on super massively parallel computers. Of late, what they have been doing is increasing the number of points they calculate the forces on. That is where they are finding these 1 and 2% increases in efficiency, with improved calculational resolution.
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NAV20
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sat Jun 02, 2007 11:48 pm

Quoting Wsp (Reply 126):
The difference is compared to previous aircraft construction methods not the A350.

So which aeroplane was Tim Clark of Emirates making the comparison with, if not the A350, Wsp?
"Once you have flown, you will walk the earth with your eyes turned skywards.." - Leonardo da Vinci
 
Shenzhen
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RE: A350XWB - Back To The Drawing Board (again) Pt

Sun Jun 03, 2007 12:01 am

Quoting NAV20 (Reply 129):
So which aeroplane was Tim Clark of Emirates making the comparison with, if not the A350, Wsp?

The FAA releases what is called a MRB (Maintenance Review Board) Report, from which the manufacturer draws up the planned maintenance for the airplane, which includes the inspection intervals. The airline/operator can use the manufacture's document for their maintenance plan or use is it a basis for theere own, which would be approved by the regulatory agencies.

If you can find the MRB reports for the various model airplanes at the FAA (maybe faa.gov) then you are half way there.

Most widebody airplanes have a heavy check around 8 or so years (depending on their maintenance plan), so if the 787 enters this at 12 years, then you have your 40 percent. In addition, all the smaller checks have been escalated on the 787, when compared to todays models.

Cheers
 
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RE: A350XWB - Back To The Drawing Board (again) Pt

Sun Jun 03, 2007 12:02 am

Quoting Astuteman (Reply 105):
We can argue some semantics about whether it's quite as good as the equivalent 787, but the fact remains that, even if the A350 sceptics are right, it will still be WAY better than any other widebody twin around, excepting the 787

 checkmark 
I can totally agree with that. The problem is that I strongly suspect that before the A350 has been in service very long Boeing will announce Y3, and will have the A350 sandwiched by superior planes.

Quoting Joni (Reply 106):
If the A350's life is "fatigue-limited" because of this to 150 years and the B787's to 350 years (for example), the difference isn't likely to be relevant. I know you'd like for it to be relevant

In this scenario you'd be right; but if the difference was, say, 40,000 cycles versus 1,000,000 cycles it would be significant. At that point it would be worth retrofitting 787's with updated engines when they come out. Granted, airframe improvements will continue to be made, but as the DC-8's have shown a sound airframe that has nearly unlimited life potential can still be worth updating long after it's obsolete.

Quoting Joni (Reply 106):

According to Airbus the A350 offers, among other things, lower OEW/seat and better economics.

I take those figures with a huge pile of salt; I'm sure if you ask Boeing which is cheaper per seat they'll prove that the 787 is. Who is right? They both are; it will depend on the mission. My suspicion is that the 787 will do better on shorter routes while the A350 will do better on long ones.

Quoting Slz396 (Reply 117):
What is better you think: Design right to the edge and then finding out through static testing you have to add basically a few pounds to match the calculations, or overdesign and proudly announce your wings can take 160% of the load????

Which would you be more comfortable flying on? I like the idea that the plane I'm on has extra margin built in; after all the FAA requirements are basically a number that was picked because it was "about right." I regard it as a minimum, rather than "this is as good as it gets." The thinking that "we build to requirements" was what sunk the DC-10; the design was finished just after McDonnell took over Douglas, and McDonnell engineers, who had never designed anything other than military planes were in charge. The result was hydraulic line routings that resulted in three major crashes that probably wouldn't have happened had it been designed by Lockheed, Boeing, or Douglas before the merger. In fact the next plane that I intend to own is a Mooney, and one of the attractions (besides its efficiency and good handling) that is very important to me is that it has a one-piece main spar that has NEVER been broken in the air. Mooney once tried to find out just how strong it was, and tested it to over 9g, whereupon their test fixture broke. Way overbuilt, but I like that in a wing spar. If you're going to put any unnecessary weight in an airplane that's where I vote to put it.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
zvezda
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sun Jun 03, 2007 12:02 am

Quoting Poitin (Reply 128):
For years and years at Boeing, and I assume elsewhere too, except they don't make random changes, but carefully stepped ones, with all the permutations done. This is trivial on super massively parallel computers. Of late, what they have been doing is increasing the number of points they calculate the forces on. That is where they are finding these 1 and 2% increases in efficiency, with improved calculational resolution.

Right, but evolutionary algorithms allow random mutations, nearly all of which result in poorer performance. However, the computer will randomly come up with something no one ever thought of that is better. For example, the fastest algorithm now known for sorting a random list of numbers was discovered by a computer running an evolutionary algorithm. Last I heard, no one had been able to figure out conceptually how it works.
 
TeamAmerica
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sun Jun 03, 2007 12:04 am

Quoting Joni (Reply 106):
True, and just looking at Boeing's website they state that only 50% of the primary structure is composite, by weight, so there's a whole lot of metal in there.

You've hit a pet peeve of mine, Joni. Measuring the content of advanced materials by weight is very deceptive. As you say, there will always be a lot of metal in there, and as the specific weight of the other materials declines their relative contribution by weight declines. That means the better the material, the less there is of it measured by weight.

When Airbus claims that the XWB will be 60% composites by weight, a cynic could wonder why their composites are heavier than Boeing's. wink 

Quoting MD-90 (Reply 120):
Does useable software with those capabilities exist?

Yes; the concept has been around for ages. The scheme Zvezda is referring to is commonly called "Monte Carlo method" but is not so random as that might imply.

Quoting Zvezda (Reply 125):
Yes, but computers are probably not yet fast enough and cheap enough to design something as complex as a wing using evolutionary algorithms. So far, it has been used for simpler designs. However, computational power is doubling about every 18 months.

More than that Zvezda, advances in software now allow massive arrays of relatively cheap computers to be used in concert. Rather than one immensely expensive super computer, we can use literally thousands of lesser computers linked together to achieve scalable performance. Anyone who does a Google search is accessing exactly such an array - it's very powerful technology.
Failure is not an option; it's an outcome.
 
Poitin
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sun Jun 03, 2007 12:17 am

Quoting Zvezda (Reply 132):
Right, but evolutionary algorithms allow random mutations, nearly all of which result in poorer performance. However, the computer will randomly come up with something no one ever thought of that is better. For example, the fastest algorithm now known for sorting a random list of numbers was discovered by a computer running an evolutionary algorithm. Last I heard, no one had been able to figure out conceptually how it works.

I was just saying what Boeing was doing for 20 years. I know because I worked at SGI, who owned CRAY at the time. As for evolutionary algorithms, they may be fun for the computer scientists, but the average engineer wants to see nicely stepped curves and such.

Could someone find a magic break through in aerodynamics using such an algorithm, sure.

Years and years ago, while I was studying psychology, we had this box that there were exactly seven ways for a rat to escape from. We were all sure of it, because we each studied the box. The first two rats found the eight and ninth ways. So you really don't need a computer to make a fool of mankind.
Now so, have ye time fer a pint?
 
zvezda
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sun Jun 03, 2007 12:23 am

Quoting Poitin (Reply 134):
Years and years ago, while I was studying psychology, we had this box that there were exactly seven ways for a rat to escape from. We were all sure of it, because we each studied the box. The first two rats found the eight and ninth ways. So you really don't need a computer to make a fool of mankind.

That's a great example. It increases my sense that a computer might accidently discover a shape that has useful aerodynamic properties.
 
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autothrust
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sun Jun 03, 2007 12:49 am

Quoting OldAeroGuy (Reply 119):
Given the Airbus superiority in wing design, how do you explain the lower long range cruise speed of the A340 (all models) compared to the 777? The 0.01 to 0.03 difference is more than can be explained by the 0.4 to 1.5 degree greater sweep of the 777.

Sorry for my ignorance but could it be because its weaker engines compared to the GE-90?

Quoting Astuteman (Reply 103):
My question too - is it possible to elaborate on this, Kaneporta1?

Indeed very interesting, though i doubt he can must be Top Secret.
Flown on: DC-9, MD-80, Fokker 100, Bae 146 Avro, Boeing 737-300, 737-400, 747-200, 747-300,747-400, 787-9, Airbus A310, A319, A320, A321, A330-200,A330-300, A340-313, A380, Bombardier CSeries 100/300, CRJ700ER/CRJ900, Embraer 190.
 
zvezda
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sun Jun 03, 2007 12:58 am

Quoting AutoThrust (Reply 136):
Sorry for my ignorance but could it be because its weaker engines compared to the GE-90?

No, the cruise speed at which fuel consumption is minimized depends on aerodynamics. The A340 has enough thrust.
 
aminobwana
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sun Jun 03, 2007 1:13 am

Quoting Astuteman (Reply 105):
Quoting NAV20 (Reply 99):
Astuteman, according to that interview with Leahy I posted earlier, the reverse would still appear to be true; you can still get a 787 earlier than you can get an A350, you will have to wait for the latter:-

you don't say
Probably a good reason why the impending explosion of A350 orders hasn't happened yet

I used the "later availability" of the 787 as an example of a reason for buying an A350, even if it was 1% or 2% more expensive to operate, not as a fact.......

BTW, I'm serious about the A350 acceleration.
We can argue some semantics about whether it's quite as good as the equivalent 787, but the fact remains that, even
if the A350 sceptics are right, it will still be WAY better than any other widebody twin around, excepting the 787

BOEING is playing a wait and see game, IMO too conservative.

But If I were AB., I would certainly not base my planning on such delivery term hopes !!

Before continuing, it is necessary to compare the real delivery terms to a given customer and not the real term
of Boeing with the EIS of Airbus (as some do !!). As the production in the first 2 years is low -excepting a small No. of first slots- the bulk of deliveries will be from 18-24 months after EIS. And given the situation at EADS and Airbus, no date for their EIS can be taken as certain! (neither Boeing's, but the risk factor there is by far, far smaller!!)

Therefore, if the deliveries of AB will begin to be strong in 2015 (I am assuming that they will have enough orders even if they continue with the panels!), then B. will ramp IMO ramp up production from 2009 on so to be able to take new orders from 2012 on, a 3 year advantage to AB (always maintaining a satisfactory backlog after this date.)

To assume that AB. will be able to book orders because a shorter term of delivery for a certain customer, is wishful thinking (as long if it foreseen that AB had already received a meaningful number of orders orders previously)

Of course, when B. is naming delivery terms today, IMO the have already reserved a considerable No, of slots for probable new customers.

aminobwana

[Edited 2007-06-02 18:18:57]
 
Gatorman96
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sun Jun 03, 2007 1:37 am

Quoting Slz396 (Reply 117):
Interesting point brought up by Sabenapilot and Kaneporta1 indeed! Thanks.

It's not that interesting unless there is some explanation...Bold statements like this warrant some serious back-up since I doubt Boeing engineers just "took a nap" while developing the wings. This is one of those cases where a source is needed (aka Kaneporta1).
 
baroque
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sun Jun 03, 2007 1:39 am

Quoting NAV20 (Reply 127):
Composites are believed not to suffer from fatigue beyond a certain point - they reach a 'fatigue floor' and don't deteriorate any further beyond that point. So if Boeing care to test the 787 fuselage to say 200,000 cycles, they OUGHT to be able to get the 787 certified for say 100,000 cycles (more than twice the level any pressurised ali aeroplane has achieved so far).

That fatigue floor is due to physical changes as I understand and is analogous, but far from identical with stress fatigue in metals. The embedding medium has another method of changes in properties that metals do not generally show in the absence of stress and that is ageing of the polymers due to factors such as time, and radiation, especially UV. The general tendency of the polymers is to develop higher indentation hardness, but become more brittle. Those types of change are rather different from the alterations to the crystal structure of metals that arises from stress cycling.

So my question related more to "normal" ageing of polymers rather than a version of what got the Comet. To test it properly, you would need not only to imitate the stress cycles associated with various phases of the aircraft but also cycling though the age profile of the material. As I noted accelerated ageing tests appear to use elevated temperatures and then calculate the results back to the expected temperature range by applying a correction based on the assumption that the changes are obeying an Arrhenius equation. But they can be tricky little buggers, the activation energy and frequency factors might be different from what you assume, or then again it might not be a first order reaction (either). Or are the effects of ageing assessed in a more complex fashion?

As the composites are used in a number of places, it is not only the pressurization/depressurization cycles that need to be considered. The composite elements on the wings undergo a whole different regime. It is all the composites, not just those that are (or are not) in a fuselage.

I am not sure your boat helps either Nav20, although hopefully it will not sink. You presumably try not to test its strength limits and it is probably more over-designed than an airplane can afford to be.
 
jacobin777
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sun Jun 03, 2007 1:55 am

Quoting Zvezda (Reply 112):
evolutionary algorithms. In other words, the computers make random mutations



Quoting MD-90 (Reply 120):
Does useable software with those capabilities exist?

..certainly does exist..its called "genetic optimisations"....which is a Zvezda explained. In fact, I know Boeing does actually use it.

We actually use a very simplified version of genetic optimisation for some of our work...

Quoting TeamAmerica (Reply 133):

More than that Zvezda, advances in software now allow massive arrays of relatively cheap computers to be used in concert. Rather than one immensely expensive super computer, we can use literally thousands of lesser computers linked together to achieve scalable performance. Anyone who does a Google search is accessing exactly such an array - it's very powerful technology.

 checkmark .....scable hardware now has become so cheap and effective.
"Up the Irons!"
 
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moo
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sun Jun 03, 2007 2:04 am

Quoting TeamAmerica (Reply 133):
More than that Zvezda, advances in software now allow massive arrays of relatively cheap computers to be used in concert. Rather than one immensely expensive super computer, we can use literally thousands of lesser computers linked together to achieve scalable performance. Anyone who does a Google search is accessing exactly such an array - it's very powerful technology.

Its a very powerful technology - within boundaries.

Clusters rapidly hit interconnect limits (the limits at which individual nodes can pass information between each other), and thats where supercomputers still rule the roost, because the interconnect speeds between 'nodes' in a supercomputer are orders of magnitude faster than those between physical computers making up the nodes in a cluster.

Google is not a great example of this because they primarily use their clusters for rapid retrieval of information based on pre-indexing done days, months or even years before, and also for 'high availability' of said information (twenty nodes carry the same information, distributed over 20 geographically different locations, so if one data center goes down, the information is still available).

To be honest, I'm surprised that genetic algorithms don't already play a part in aircraft design because it can rapidly go through many design iterations, much faster than a human design team could ever.
 
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autothrust
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sun Jun 03, 2007 2:24 am

Quoting Zvezda (Reply 137):
No, the cruise speed at which fuel consumption is minimized depends on aerodynamics. The A340 has enough thrust.

Ok, thanks for the explanation. So its the A340 Structure or the Wings which can't support higher speeds :

Max Speed B777: 896 km/h Max Speed A340 0.86 M

777 Typical Cruise Speed
at 35,000 feet 0.84 M (from Boeing)

A343 0,825-0,830 M
Flown on: DC-9, MD-80, Fokker 100, Bae 146 Avro, Boeing 737-300, 737-400, 747-200, 747-300,747-400, 787-9, Airbus A310, A319, A320, A321, A330-200,A330-300, A340-313, A380, Bombardier CSeries 100/300, CRJ700ER/CRJ900, Embraer 190.
 
zvezda
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sun Jun 03, 2007 2:28 am

Quoting AutoThrust (Reply 143):
So its the A340 Structure or the Wings which can't support higher speeds

The issue is not "support higher speeds" but rather the speed at which efficiency is optimal. For the 777, Boeing planned 0.83M and found that it was 0.84M.
 
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SEPilot
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RE: A350XWB - Back To The Drawing Board (again) Pt

Sun Jun 03, 2007 2:30 am

Quoting AutoThrust (Reply 143):


Ok, thanks for the explanation. So its the A340 Structure or the Wings which can't support higher speeds :

It's not that they can't support it; it's that drag starts increasing rapidly due to sonic compression and so efficiency goes down the toilet at a certain Mach number. That point is highest on the 747 of all airliners currently produced (I believe it has only been exceeded by the Concord and the CV-880 and CV-990 among civil transports.)
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
atmx2000
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sun Jun 03, 2007 2:32 am

Quoting TeamAmerica (Reply 133):
You've hit a pet peeve of mine, Joni. Measuring the content of advanced materials by weight is very deceptive. As you say, there will always be a lot of metal in there, and as the specific weight of the other materials declines their relative contribution by weight declines. That means the better the material, the less there is of it measured by weight.When Airbus claims that the XWB will be 60% composites by weight, a cynic could wonder why their composites are heavier than Boeing's.  

An extreme hypothetical example of this would be a place where 50% of the aircraft by weight was replaced with material weighing 1% of the Al required for that structure. The aircraft would be 99% aluminum by weight and 1% super light material by weight despite the fact the weight of the aircraft is 49.5% less.
ConcordeBoy is a twin supremacist!! He supports quadicide!!
 
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SEPilot
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sun Jun 03, 2007 2:46 am

Quoting Atmx2000 (Reply 146):
An extreme hypothetical example of this would be a place where 50% of the aircraft by weight was replaced with material weighing 1% of the Al required for that structure. The aircraft would be 99% aluminum by weight and 1% super light material by weight despite the fact the weight of the aircraft is 49.5% less.

Bear in mind that the engines and landing gear are probably going to remain primarily steel, titanium and other relatively heavy metals for the foreseeable future, and as other parts of the plane get lighter they are going to account for a greater and greater percentage of the weight.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
astuteman
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RE: A350XWB - Back To The Drawing Board (again) Pt 2

Sun Jun 03, 2007 3:10 am

Quoting Zvezda (Reply 108):
No need to limit that to twins. At the time of the A350's EIS, the A350 and 787 will be far better than any other widebodies. Full stop.

A conclusion that I am being progressively forced to accept, and you know what they say, a converted sceptic is worth 10 blind disciples.....  Wink

Quoting MD-90 (Reply 120):
I believe you're thinking of the vertical tail, which was reinforced? (but saying they 'screwed up the design" is overly harsh, imo).

On the A380, as a precaution, following an additional test, Airbus added 2kg of material to the trim tab actuator bracket....
Saying they screwed up is most definitely overly harsh..... yes 

Quoting BigJKU (Reply 124):
I agree they probably did not screw up but they made changes because the initial design was less than optimized.

I'm curious to know how many changes of that type you think take pace during a typical development programme....
Do you think the 787 is any different? (or any other airliner for that matter)

Regards
 
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SEPilot
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RE: A350XWB - Back To The Drawing Board (again) Pt

Sun Jun 03, 2007 3:25 am

Quoting Astuteman (Reply 148):
I'm curious to know how many changes of that type you think take pace during a typical development programme....
Do you think the 787 is any different? (or any other airliner for that matter)

 checkmark 
Certainly any major design is going to end up with some things that are less than optimum; but what matters most is the end result, and to a lesser extent how much it cost to get there. When a problem shows up it is usually better to fix it right than fix it cheap, but again that is a judgment call on the part of those in charge and depends on the severity of the problem and the consequences if it is not up to par. My experience is that engineers are people and as such subject to making mistakes. Computers do not help; one of my adages is that to err is human; to really screw it up you need a computer. To say that Boeing engineers are somehow less subject to this than Airbus engineers is to engage in fantasy. I am quite confident that both are equally capable of outstanding designs and at the same time subject to making mistakes. What will make a difference is the directions from management; they are the ones that set the goals and decide on the remedial actions once mistakes are uncovered.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler

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