mffoda
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A350 Prototypes Production Thread Part 5

Fri Aug 24, 2012 9:30 pm

I started part 5, since part 4 has been archived.

There are some interesting developments in A350 program, according to AW. It looks like Airbus will use "batches" as its change incorporation method.

http://www.aviationweek.com/Article....l/AW_08_27_2012_p22-488795.xml&p=1

Here is the opening sentences of the article and you can read the entire article on the above link:


"Airbus is doing everything to keep the A350 on the latest revised schedule and thereby please its early customers. But that means important changes must be incorporated later in production, incurring huge additional costs—for Airbus and its suppliers.

Airbus plans to introduce the A350 in several batches, each of which will incorporate changes, with the most significant modifications made in the transition from Batch 2 to 3. The changes affect parts and components throughout the aircraft, and suppliers have been given detailed design targets that specify the amount of weight reduction needed, among other things.

Batch 1 will include all the flight-test aircraft and early produc-tion versions, including MSN4, industry officials say. The first round of relatively minor design changes will be incorporated with MSN5. The more fundamental upgrade will happen with MSN17, say two executives with knowledge of the matter. Airbus has not revealed the exact points of transition, but Andreas Fehring, A350 senior vice president, head of fuselage and cabin, confirms that Airbus has decided to incorporate the A350 changes by batches.

The A350's cabin is one major area in which upgrades are going to be made. From MSN17 on, 40% of cabin parts will be changed, industry officials say. Airbus neither confirms nor denies that figure. The redesign includes cabin bracketing—the way the interior is attached to the fuselage—and the air-conditioning system, as well as other interior components.

Other areas that will see significant modification are structural and wing components."
harder than woodpecker lips...
 
maxter
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RE: A350 Prototypes Production Thread Part 5

Fri Aug 24, 2012 10:26 pm

So given the significance of the changes between batches, then retrofitting of earlier batches are out of the question I take it...

An interesting change indeed, wonder how that's negotiated with customers. Do we have customers with essentially now quite different aircraft in their fleets that are/were supposed to be the same.
maxter
 
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Stitch
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RE: A350 Prototypes Production Thread Part 5

Fri Aug 24, 2012 10:32 pm

Sounds similar to what Boeing is doing with the 787-8 via Block Points.
 
bigsmile
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RE: A350 Prototypes Production Thread Part 5

Sat Aug 25, 2012 1:03 pm

Expect to see one ES wing going to Toulouse from UK around 30th or 31st of August. With the other 3 following to Germany and France over the following 3 weeks.
 
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EPA001
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RE: A350 Prototypes Production Thread Part 5

Sat Aug 25, 2012 1:20 pm

Quoting Stitch (Reply 2):
Sounds similar to what Boeing is doing with the 787-8 via Block Points

I guess it does. Which is a good thing. In this way they can control the configuration easier then if the changes come into production the moment they are ready.
 
Flyglobal
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RE: A350 Prototypes Production Thread Part 5

Sun Aug 26, 2012 10:54 am

They have obviuosly identified a number of changes which should make the plane better, respectively which aren't as good as expectation. In oder to incorporate this they would need to delay the EIS further, but will go ahead now and make the changes in the block points/ batches they scheduled now.

It isn't hat different to what we do in vehicle development. Even shortly after Start of production we introduce block points as well to industrialize some early fixes.

Regards

Flyglobal
 
ferpe
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RE: A350 Prototypes Production Thread Part 5

Sun Aug 26, 2012 11:24 am

What is interesting is the point of the changes (LN17) and what is the major changes (cabin installation) but I don't see the big news in the fact that there will be improved version. It has happened on every frame I know of, the A330 is still being changed/improved in batches after 16 years of production  .

The real interesting part is how much the overweight is on the early frames and how quick/easy one gets to design weights.

Re performance guarantees, I am not sure A guaranteed MEW/OEW, they could have given performance guarantees. if the engine or areo is better then expected (the engine seem to be) then this could compensate an early overweight leaving A in the clear.

Quoting bigsmile (Reply 3):
Expect to see one ES wing going to Toulouse from UK around 30th or 31st of August. With the other 3 following to Germany and France over the following 3 weeks.

Thanks, now this one ES wing, does it confirm that the ES frame has one wing as per Zekes posts and picture?

How does 1+3 = 4 jive with Evrards comments of 5 wings being produced?
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bigsmile
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RE: A350 Prototypes Production Thread Part 5

Sun Aug 26, 2012 11:45 am

Quoting ferpe (Reply 6):
Thanks, now this one ES wing, does it confirm that the ES frame has one wing as per Zekes posts and picture?

How does 1+3 = 4 jive with Evrards comments of 5 wings being produced?

MSN001 = 2 Wings.......for obvious reasons of course  
ES = 2 Wings (Right Hand to go first, followed by Left hand a few days later)
EW = 1 Wing

Later in the build there is the EF set of wings (2 wings)
 
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RE: A350 Prototypes Production Thread Part 5

Wed Aug 29, 2012 5:16 pm

Quoting bigsmile (Reply 3):
Expect to see one ES wing going to Toulouse from UK around 30th or 31st of August.

I thought the ES airframe was in Erding, Germany?
 
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Stitch
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RE: A350 Prototypes Production Thread Part 5

Wed Aug 29, 2012 5:19 pm

Quoting Laddie (Reply 8):
I thought the ES airframe was in Erding, Germany?

The EF2 and EW rigs are in Erding, with the EF3 rig in Hamburg per http://www.flightglobal.com/news/art...-for-main-structural-tests-365076/

[Edited 2012-08-29 10:19:51]
 
CM
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RE: A350 Prototypes Production Thread Part 5

Thu Aug 30, 2012 6:07 am

Quoting ferpe (Reply 6):
The real interesting part is how much the overweight is on the early frames and how quick/easy one gets to design weights.

Weight optimization is a painstaking process of refinement, as you press the design towards increasingly reduced (and ideally, zero) strength margins. Depending on what part of the airplane you are talking about, it can be the slowest part of the design process and can add risk when done in advance of the structural testing needed to calibrate your models and analysis methods. Designing too close to zero margin before the related testing is completed can bite you. For this reason, blockpoints after static testing, fatigue testing and flight loads survey are all natural points to take some additional weight out of the airplane. Given what I know of the 787 weights and scaling that to the A350, I regard Airbus' public OEW numbers to be very optimistic. At best, they seem to represent of a mature, weight optimized A350 design.

Quoting ferpe (Reply 6):
I am not sure A guaranteed MEW/OEW

It doesn't make a lot of sense for an OEM to guarantee OEW on a paper aircraft where there are so many unknowns. Even for a mature type, an OEM does not always guarantee OEW as a part of the aircraft sale; there are much more operationally relevant parameters, which are routinely guaranteed. Sometimes you will see an OEW guarantee for a delivery stream that will span many years, where the buyer is looking for some protection against the typical OEW growth all aircraft seem to experience over the course of time. That being said, Airbus is often willing to offer non-traditional guarantees to get a deal done (a Leahy hallmark). If some potential A350 customer was waffling over Airbus' marketed OEWs, it wouldn't surprise me at all to learn Airbus overcame that hurdle by offering a guarantee.
 
ferpe
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RE: A350 Prototypes Production Thread Part 5

Thu Aug 30, 2012 2:05 pm

Quoting CM (Reply 10):
I regard Airbus' public OEW numbers to be very optimistic. At best, they seem to represent of a mature, weight optimized A350 design.

If we compare with the publicized 788 number you will see these are more aggressive:

787-8 224 seats config: OEW 111.5t out of a MTOW 228t = 48.9%

A359-900 assumed OEW about 135t which is 50.4% of MTOW, not a very aggressive figure. If you have a more aggressive one please indicate.

A350-1000 indirectly shown OEW 153t out of a MTOW of 308t = 49.7%, also not very agressive. Once again if you have other values please indicate.


That makes for 1.5% lower ratio for the 787 first member compared to A350, to me the 350 weights seems conservative (once again if these assumed numbers are in the ballpark).

[Edited 2012-08-30 07:59:09]
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CM
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RE: A350 Prototypes Production Thread Part 5

Thu Aug 30, 2012 3:36 pm

Quoting ferpe (Reply 11):
If we compare with the publicized 788

It is too simplistic to make the comparison in this way, Ferpe. If you scale the cabins of the two aircraft proportionally, the 787 ends up with much less wing, tail, fuselage (diameter) and engine than the A350. Rather than trying to compare ratios at the aircraft level for two aircraft with very different proportions throughout their design, it is far more precise to make comparisons of the major components and build up to the airplane level in order to evaluate a weight claim. Obviously, this can only be done if you know the weight of the components for a baseline of comparison. I'm not free to share those details for the 787, but when I make the comparisons in that way, I believe the A350 OEW is much closer to 145t. This kind of comparison should be pretty precise since the overall architectures, material technologies and design optimization tools are the same between the two aircraft.
 
astuteman
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RE: A350 Prototypes Production Thread Part 5

Thu Aug 30, 2012 3:46 pm

Quoting CM (Reply 12):
I believe the A350 OEW is much closer to 145t.

Just so I get this straight.

An A350-900 with
a fuselage which is smaller than a 77L,
the same wing size (area and span) as a 77L,
MUCH smaller engines than a 77L,
is designed for a much lower MTOW than a 77L,
has double bogie MLG instead of triple bogie mlg,
is made of much more modernn materials.

Yet it has at least as high an OEW as a 777-200LR, making it 10t+ overweight?   

I hope you'll pardon my scepticism.

But it appears to me that your method of calculation might also require with a "check for understanding"....

An A350-900 shouldn't have an OEW anywhere near that of a 777-200LR.

Unless you're going to tell me that's "just how good Boeing are".....  

Rgds
 
CM
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RE: A350 Prototypes Production Thread Part 5

Thu Aug 30, 2012 4:39 pm

Quoting astuteman (Reply 13):
I hope you'll pardon my scepticism.

Skepticism pardoned.

I think the sticker shock from my number is you are looking at OEM published numbers and I am working from real-world airplane weights. There is generally some difference between those numbers, making a few tonnes in my calculation look like 10t when you compare my number to yours. TK makes their aircraft weights public, making them an easy target to illustrate the gap between real world and OEM published numbers:

A330-200 Airbus ACAP OEW........ 117t
A330-203 TK OEW....................... 122t

A330-300 Airbus ACAP OEW........ 120t
A330-300 TK OEW....................... 125t

777-300ER Boeing ACAP OEW.... 168t
777-300ER TK OEW.................... 169t

A340-300 Airbus ACAP OEW....... 125t
A340-300 TK OEW...................... 131t
 
ferpe
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RE: A350 Prototypes Production Thread Part 5

Thu Aug 30, 2012 8:37 pm

Quoting astuteman (Reply 13):
I hope you'll pardon my scepticism.

   your rhetoric elegance is always a joy to watch .

.
Quoting CM (Reply 12):
It is too simplistic to make the comparison in this way, Ferpe. Rather than trying to compare ratios at the aircraft level for two aircraft with very different proportions throughout their design, it is far more precise to make comparisons of the major components and build up to the airplane level in order to evaluate a weight claim.

Thanks for lighting a fire in this thread, it has been a bit quiet lately     

I understand how you might work to reach a comparison, it might be the way that OEMs do it. I do however think that the ratio analysis has a lot of merit for the very same reasons that you give, the frames are designed with the same tools, carry the virtually the same engines, use the same wing technology (re wing thread in tech-ops) and are certified to the same standards. So lets look into why a ratio method can have some merit:



HISTORICAL EVIDENCE
In several of the classical textbooks of civil airliner design the almost perfect tracking of OEW to 50% of MTOW for civil airliners is noted, here just one of these in a graph:



In general a civil airliner is made up of

50% structure and systems

10 % payload

40% fuel

The general variation around this values has to do with the fuel fraction value, if the frame is mid-haul the fuel tends towards 35% and the ratio towards 52-55%. If the frame is a ULH or even UULH like the 777-200LR it is a flying tanker and the fuel ratio goes up, the OEW ratio tend even below 45% as fuel does not cost so much structure to carry as it alleviates wing bending moment. But in general OEW ratios stays around 48-54%. A modern CFRP frame with fuel efficient engines consumes less fuel per kg and nm, therefore the OEW ratio actually increases a % or so instead of the intuitive decrease, as wisely pointed out by our Astute guy on a previous thread.



MODERN EVIDENCE
So how does out normal discussed frames stack up in this context. In fact pretty well (click on the table to see better):

http://i298.photobucket.com/albums/mm262/ferpe_bucket/OEWvsMTOW.jpg



788 vs 359 DIMENSIONAL ANALYSIS
You have made a dimensional analysis and reached the verdict that the A359 should have a a OEW/MTOW ratio of 54%. I can't find any evidence why this should be the case, all relevant dimensions point towards a 20% larger 359 vs 788, this should also be the case for the OEW, ie around 135t:



In fact your claimed "large" pieces on the 359 (fuse dia, wings) are not large, the fuse dia is only 3% larger and the fuselage area (which is more valid for weight discussions) is smack on 20% larger. The wingloading is the same ie the wingarea vs weight is the same ratio thus the wings are very similar, just a 20% scale copy of each other. They even use the same high-lift principles (except for the small are of droop nose instead of slat for the 359).

Where do you see the big differences?

[Edited 2012-08-30 13:56:58]
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astuteman
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RE: A350 Prototypes Production Thread Part 5

Thu Aug 30, 2012 9:16 pm

Quoting CM (Reply 14):
TK makes their aircraft weights public, making them an easy target to illustrate the gap between real world and OEM published numbers:

Trouble is, the TK figures imply that a 777 is only going to be a tonne or so over ACAP, which means you are STILL telling me that a real-world A350-900 is going to have the same OEW as a 777-200LR.

On the other hand, if the real world figure for the A350-900 is 3-4t over the ACAP OEW, then it might not necessarily represent a real overweight, provided it is accounted for in the spec given to the OEM. As is clearly the case for A330's and A340's..

Rgds
 
CM
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RE: A350 Prototypes Production Thread Part 5

Fri Aug 31, 2012 7:38 am

Quoting astuteman (Reply 16):
the spec given to the OEM

I think you mean the spec given to the customer? The numerous comments from customers tend to support my sense the A359 has a weight problem, and that would be relative to a customer spec weight, not the understated weights we see in the ACAP.

Quoting ferpe (Reply 15):
HISTORICAL EVIDENCE

The only question I would have about this is what OEW is being used? A real one, or the imaginary one from the ACAP?

Quoting ferpe (Reply 15):
788 vs 359 DIMENSIONAL ANALYSIS

This is good stuff, Ferpe. I'll take a longer look at this when I get a chance.
 
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RE: A350 Prototypes Production Thread Part 5

Fri Aug 31, 2012 10:14 am

Quoting CM (Reply 10):
I regard Airbus' public OEW numbers to be very optimistic.

I do not, they fit many independent models. BTW, Airbus has not published their OEWs, so your whole post kinda lacks any sort of factual basis. If as you say they have made public the OEWs, you could point all of us to the numbers and source they have published.

Quoting CM (Reply 10):
It doesn't make a lot of sense for an OEM to guarantee OEW on a paper aircraft where there are so many unknowns

Those weights are passed downstream, and suppliers have to meet specific weights for different components or sections. Airbus already has publicly stated that they have weighted various large subsections as they arrived, and weight is meeting their expectations. I do not think anyone is expecting the first airframe to come off the production line at spec weight, if it did, they target would have been set too low. That does not mean it would be out of their tolerance level.

Quoting astuteman (Reply 13):
Yet it has at least as high an OEW as a 777-200LR, making it 10t+ overweight?

The A350-1000 will have an OEW about the same as the 777-200LR, with a fuel burn close of an A330-300. One of the major reasons why the A350 is lighter is they are burning over a tonne less an hour fuel less per engine. The whole airframe then can be sized lighter, it is dealing with lower design loads.

An easy comparison can be made with the A340-600 vs the 777-300ER, the difference in fuel burn and OEW weight is much the same sort of step again.

Quoting astuteman (Reply 13):

An A350-900 shouldn't have an OEW anywhere near that of a 777-200LR.

It does not, much the same as the 777-200A, however 20 years of technology developments later (1994 vs 2014).

Quoting CM (Reply 14):

We have around a 5t variation in OEWs on our A330s, depending on what seats are installed. The older regional business class, and older Y seats match Airbus OEW, new flat bed seats, and new Y seats with more IFE pushes the OEW up 4-5t with less seats. The underlying MEW has gone down, the OEW has gone up.

Our A340s OEWs are similar to TKs, again that is with a modern interior. The A330/A340 OEWs were developed when the cabin used to just have a single projector in each cabin with a beta max tape player and without electric motors in the seats. Our 77W are a couple of tonnes heaver than TKs, again I would suggest this is due to the interior, not the MEW.

To use the OEWs they way you have is very disingenuous.
We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
 
Daysleeper
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RE: A350 Prototypes Production Thread Part 5

Fri Aug 31, 2012 10:38 am

Post surplus to requirements.

[Edited 2012-08-31 03:44:48]
 
ferpe
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RE: A350 Prototypes Production Thread Part 5

Fri Aug 31, 2012 10:51 am

Quoting CM (Reply 17):
The only question I would have about this is what OEW is being used? A real one, or the imaginary one from the ACAP?

I understand it to be the "imaginary" ones from "showroom" specs as later publicized in documents like ACAPs. It would make no sense for an OEM to spec a "fly-away" ready frame in any other form. How should they set the complexity of the seats or IFE other then absolute basic? I have read somewhere that ICAO should have some sort of minimum standard what such a showroom furnishing and cabin/flight equipment should contain. Is their an ICAO recommendation for such things? Or is there an "industry understanding" what a "3 class cabin" in showroom version should contain (not the number of seats in each class, that is specified separately, but rather the seat types, lavs, gallies etc?).


Re what Airbus have published or not, they have published the target MEW (they call it MWE) for the A350-900:

"The target service-entry MWE for the A350-900 was 113.5t, but this has risen to 115.7t, he (McConnel) adds"

http://www.flightglobal.com/news/art...t-in-1-fuel-penalty-airbus-224578/

If one take the 63 kilos average per pax I use to come from Airbus MWE to a Airbus showroom 3 class of 314 pax one would end up with 135.5t, this is how I reached my 135t. Zeke says it is similar to a 777-200A which has an ACAP figure of 135.9t, seems we are hovering around 135t.


That the MWE for the first frames will be more then 115.7t is rumored by Aspire and others, the discussion seems to be around 2-3% overweight, ie 118.5t or thereabouts. It would mean the first frames would come in just shy of 140t.

[Edited 2012-08-31 03:53:42]
Non French in France
 
tdscanuck
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RE: A350 Prototypes Production Thread Part 5

Fri Aug 31, 2012 12:14 pm

Quoting zeke (Reply 18):
Airbus has not published their OEWs, so your whole post kinda lacks any sort of factual basis.

Not exactly. Airbus has published lots of performance and spec numbers for the A350. Weight estimation heuristics for commercial jets are very good; you can back out what the OEW must be, with a fairly impressive margin of error, from the facts that are out there.

Quoting zeke (Reply 18):
Airbus already has publicly stated that they have weighted various large subsections as they arrived, and weight is meeting their expectations.

Are they getting 100% complete sections already? If so, that's extremely impressive. But it's also very unlikely.

Tom.
 
astuteman
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RE: A350 Prototypes Production Thread Part 5

Fri Aug 31, 2012 12:31 pm

Quoting CM (Reply 17):
I think you mean the spec given to the customer?

Correct.

Quoting CM (Reply 17):
The numerous comments from customers tend to support my sense the A359 has a weight problem, and that would be relative to a customer spec weight, not the understated weights we see in the ACAP.

I don't disagree either. But I sense a muddling between "spec" OEW's and what you call "real" OEW's.

It would not surprise me to learn that the flight test A350-900's are 5t heavier than they are meant to be. If a customer "real" OEW is 5t higher than Airbus's spec, then that real frame might be 10t heavier than Airbus's "spec", but only 5t overweight.

By frame 17, Airbus seem to be suggesting they will have the weight back to where it is meant to be. I don't see this as being any different to the 787's early block points.
i'm sure you'll agree that later 787's are going to hit spec weight.

A "spec" weight A350-900 from LN 18 onward could easily have an in-service OEW some 5t heavier in airline config. But this is no different to CX,s, EK's and SQ's 77W's, all of which have "in-service" OEW's of around 174-175 tonnes, some 6 or 7 tonnes higher than "spec".
But they aren't overweight   

Rgds
 
CM
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RE: A350 Prototypes Production Thread Part 5

Fri Aug 31, 2012 3:15 pm

Quoting astuteman (Reply 22):
It would not surprise me to learn that the flight test A350-900's are 5t heavier than they are meant to be. If a customer "real" OEW is 5t higher than Airbus's spec, then that real frame might be 10t heavier than Airbus's "spec", but only 5t overweight.

I don't think we're in disagreement (maybe just violent agreement?), we're just looking at the airplane using a different baseline for reference. That's all. I'm quite confident real world A350-900s will tip the scales with a dry operating weight at or exceeding 145t.

Quoting ferpe (Reply 15):
788 vs 359 DIMENSIONAL ANALYSIS

Ferpe, the A359 is larger than the 787-9, and MUCH larger than the 787-8. The A350 family has design elements which are presumably optimally sized for the A359, yet will be accordingly oversized for the A358. The same is true for the 787-9 relative the 787-8. Your comparison seems like it should be between the A350-900 and 787-9 or A350-800 and 787-8 to help wash out any level of deoptimizations the OEM's accept for a minor model as a part of their family strategy.

Thoughts?
 
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RE: A350 Prototypes Production Thread Part 5

Fri Aug 31, 2012 7:46 pm

Quoting CM (Reply 23):
Your comparison seems like it should be between the A350-900 and 787-9 or A350-800 and 787-8 to help wash out any level of deoptimizations the OEM's accept for a minor model as a part of their family strategy.

Thoughts?

I don't think so for several reasons. In this reasoning I'm threading on grounds on the B side you know much better then I so bear with me on any mistakes made and I probably do the same on the A side. Well, nothing ventured, nothing gained  :

787 family:
In my mind the 787-8 was developed as first member of a family which would live in the space between SA and the 777 family (or it's successor). Thus the 787 is very much an optimized design for the 200-300 pax space with a natural cap from the 777 and the 788 as the first member is optimized for the lower part of that. In summary the design objective for the 788 was a well optimized 200-250 pax frame. The 789 is a stretch of the 788, as such it benefits from all the experience gained on the 788 but at the end of the day it also lives with a couple of donor traces, one being a wing which is a tick on the small side.


The A350 family:
In it's final incarnation the 350 family targets the 250-350 pax market, ie most of 787 and 777. The first member is designed in the middle of the window contrary to the 787 first member. This might result in a better optimization for the stretched top member (-1000) but makes life difficult for the shrink, especially if parts are not redesigned to recuperate the lower loads. To be fully fair to the 789 the -1000 wing, being a simple enlargement of the -900 via a TE extension, is also a tick on the small side, it would probably have had more span had the -1000 been a clean sheet design (for interested have a look in the tech/ops A vs B wing thread). Thus the 359 is very much the fully optimized member.


I think the different design philosophies for the 787 and 350 families are very evident when one puts them over each other in a frontal view:


http://i298.photobucket.com/albums/mm262/ferpe_bucket/A350vs788frontviewcomparison20120830.jpg


Here one can clearly see several things (788 blueish and 359 gray lines):

- The 787 is more compact in it's design, the MLG is shorter and the engines are hung higher visavi the wings, the wing fairing sleeker. This saves weight and frontal area, not only because the heavy legs of the NLG and MLG are shorter but the loads transferred through the LG legs from heavy landings have less lever lengths and the sleeker fairing creates less pressure drag.

- The 350 team on the other hand would say this is deliberate, the 350 shall compete with Boeing's 200-400 pax offerings over 40+ years, we want room for higher BPR engines, either on a -1100 variant on in a -neo variant later on. "This family is designed as flexible as possible, is shall cover everything between SA and 380. And our wing fairing was sized to also take larger 6 wheel bogies."


While these arguments can carry a discussion in themselves, I have described them to foster my thesis that the most relevant comparison between the 787 and 350 families would be their anchor models, those that were designed from a clean sheet of paper and not a stretch from one with an anchor from the other. The anchors ended up with a 20% spread in design points, the 788 with an emphasis on compactness and the 350 on further expansion, but they were both optimized for their missions, to carry their design payload (20% apart) some 8000nm. (some may argue the 788 does not do that, well once on target OEW it definitely does IMO). So fully matured I think these are the two that shall be compared as they best represent the design philosophy of their respective family.


Edit: Having written this long post I read you question again, I think their is a much shorter answer to say what I did above  Wow!  : I don't think the 787-8 was designed as a shrink from the 787-9 but the 350-800 definitely was from the 350-900.

[Edited 2012-08-31 13:44:02]
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EPA001
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RE: A350 Prototypes Production Thread Part 5

Fri Aug 31, 2012 11:17 pm

Quoting ferpe (Reply 24):
Edit: Having written this long post I read you question again, I think their is a much shorter answer to say what I did above

Probably yes. But, the extended version of your post is highly appreciated by me.  
 
CM
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RE: A350 Prototypes Production Thread Part 5

Sat Sep 01, 2012 7:59 am

Quoting ferpe (Reply 24):
I don't think the 787-8 was designed as a shrink from the 787-9

Not a shrink, per se, but the 787 in its original conception was intended to be a family with common elements as follows:

................787-3.......787-8.......787-9
Fuselage.....X..............X..........Stretched
Wing......Clipped..........X.............X
Engines......X...............X.............X
Tail.............X...............X.............X
Gear...........X...............X.............X
Systems*...X...............X.............X

* systems elements sensitive to sizing (ECS, generators, APU, etc)

Instead, the 787-3 was dropped and Boeing began entertaining the idea of a 787-10. That changed the equation to look like this:

................787-8.......787-9.......787-10
Fuselage......X....Stretched...Stretched
Wing............X.........X.............X
Engines........X.........X.............X
Tail...............X.........X.............X
Gear.............X........Strengthened
Systems*......X........Grown

It was always the plan the 787-8 and 787-9 would have common wings engine and tail. The MTOW growth of the 787 family caused us to go look at a 209' span for the 787-9, but the weight penalty overwhelmed what would have been Oswald's "ideal" wing - the span added enough weight that the airplane gained only a handful of miles in range (due to greater fuel volume), but actually had higher block fuel than the 197' span used on the 787-8. The weight gain was an inevitable consequence of adding span with such a shallow airfoil at the wing root. This tells me the original 787-8 wing planform was actually sized right for the 787-9, not that it is slightly undersized for the 787-9.

Quoting ferpe (Reply 24):
a wing which is a tick on the small side.

I guess the question is, by what measure. The current 787-9 wing is the lowest block fuel wing we studied, and it just happens to be the same planform as the 787-8.
 
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RE: A350 Prototypes Production Thread Part 5

Sat Sep 01, 2012 8:38 am

Quoting CM (Reply 23):
I'm quite confident real world A350-900s will tip the scales with a dry operating weight at or exceeding 145t.

You might possibly end up being right with that.
But if you use the wrong reference point, you can end up, as you have, inferring that this is a serious overweight, when it may not necessarily be anything of the sort.

If EK's A380's had hit their original spec weight from the outset, their DOW would still have been 295 tonnes, way above any figure published by Airbus. But they wouldn't have been overweight.

Rgds
 
ferpe
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RE: A350 Prototypes Production Thread Part 5

Sat Sep 01, 2012 8:37 pm

Quoting CM (Reply 26):
the 787 in its original conception was intended to be a family with common elements as follows

Thanks for this description, very interesting and a bit news for me. Re the 789 wing being a tick on the small side, this was my conclusion in this A vs B wing thread:

www.airliners.net/aviation-forums/tech_ops/read.main/315161/1/#11

It and the following posts shows that with the engines available the V2 is quite high at 185kts and the initial flight level of 330 is a tick lower then your ideal of 350 or more. On the other hand once in cruise the wing is coming into it's own, at mid cruise weight (at some 83% of MTOW) the induced drag is close to the parasitic drag, this is close to a drag minimum as per this principal picture:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/Totaldragcurve.jpg

This whole discussion is ignoring transonic drag which tends to follow wingloading for equal designs, here the 789 with 680kg/m2 will have some counts higher drag then wings that are loaded at some 600kg/m2 like the 788 and 359, something it shares with the 350-1000 (at 670).


So if we disregard start performance (or get stronger engines) and initial flight level the 789 wing is sized about right according to textbook theory. Now this is textbook theory, you say it turns up right in your simulations which then of course is the real thing, compared to that simplified textbook stuff can be virtually ignored  .


Given your very interesting insight into the 787 family original philosophy, there is nothing stopping us from comparing the 789 to the 350, here the table with the 789 added:



Once again you get a consistent picture, the relevant values are hovering around 108% for 789 vs 359 just as they were hovering around 120% for 788 vs 359. And if my guess of the 789 showroom OEW at 125t is in the ballpark then the OEW of the 359 lies at about 108% of that.

[Edited 2012-09-01 13:42:29]
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ferpe
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RE: A350 Prototypes Production Thread Part 5

Sat Sep 01, 2012 8:56 pm

Quoting CM (Reply 26):
The weight gain was an inevitable consequence of adding span with such a shallow airfoil at the wing root. This tells me the original 787-8 wing planform was actually sized right for the 787-9, not that it is slightly undersized for the 787-9.

You comment about 787 shallow airfoil at the wing root of course get me to this picture from earlier in the thread:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/350vs787middlesectionandwingbox.jpg


It seems when measuring on these and other pictures that the 350 wing is a % or two thicker then the 787 at the root. If you can do that without a drag increase you get a higher build height and a relatively reasoned lighter wing. Not sure it is the case but you tend to indicate the 787 wing is a bit thin to extend, ie any long-range version of 787-10 needs a beefier wing.

Further you indicate the 788 wing is a tick on the large size if the wing is right for the 33t heavier 789   .

[Edited 2012-09-01 13:57:41]
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CM
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RE: A350 Prototypes Production Thread Part 5

Sun Sep 02, 2012 3:24 pm

Quoting ferpe (Reply 29):
Further you indicate the 788 wing is a tick on the large size if the wing is right for the 33t heavier 789
 

By design, I believe this to be the case.
 
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RE: A350 Prototypes Production Thread Part 5

Mon Sep 03, 2012 7:57 pm

While we wait for the wingboxes to appear (I don't think we will see full wings for the ES aka MSN5000) here is another piece that will be put onto the MSN001 wings. These are made by FACC, an Austrian tier 1. I must admit I don't know when they will be fitted, they should most logically be fitted at FAL to avoid the physical dimensions in the Beluga during wing transport (they are 6m in total when put together ! ) :





The shape is really interesting, I would say a cross between a blended winglet and a raked wingtip   . If the A320 has sharklets, I would say the A350 has sharkfins  Wow!  .

[Edited 2012-09-03 13:00:45]
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RE: A350 Prototypes Production Thread Part 5

Mon Sep 03, 2012 10:17 pm

Quoting ferpe (Reply 31):

The shape is really interesting, I would say a cross between a blended winglet and a raked wingtip

The shape is a full-chord, blended winglet, as a raked wingtip is in the plane of the wing. They are a scaled up version of the A320 Sharklets.

BTW, Aviation Partners thinks the A320 Sharklets are a copy of their patented design.
http://www.flightglobal.com/news/art...ion-on-sharklet-a320-sales-375243/
 
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RE: A350 Prototypes Production Thread Part 5

Tue Sep 04, 2012 2:43 am

Quoting Laddie (Reply 32):

BTW, Aviation Partners thinks the A320 Sharklets are a copy of their patented design.

Airbus has also filed suit claiming the APB patent should be revoked. If you look at the 15m racing gliders in the 1980s like the Masak Scimitar, they already had blended winglets, so did the Rutan Voyager. Bit hard then 5-10 years later to try and patent something that is already flying.

We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
 
ferpe
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RE: A350 Prototypes Production Thread Part 5

Tue Sep 04, 2012 2:51 am

Quoting Laddie (Reply 32):
They are a scaled up version of the A320 Sharklets.

APs design and the sharklets bend and then have a straight section for over 2 meters, these bend all the way to the tip, thus I would classify them as not the same. IMO they look like bent versions of the 787 raked wingtip.

Quoting Laddie (Reply 32):
BTW, Aviation Partners thinks the A320 Sharklets are a copy of their patented design.

Sure, well see where this ends.
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azjubilee
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RE: A350 Prototypes Production Thread Part 5

Tue Sep 04, 2012 3:12 am

Who will be taking delivery of the first 350-800s?
 
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RE: A350 Prototypes Production Thread Part 5

Tue Sep 04, 2012 5:35 am

Quoting zeke (Reply 33):
Airbus has also filed suit claiming the APB patent should be revoked. If you look at the 15m racing gliders in the 1980s like the Masak Scimitar, they already had blended winglets, so did the Rutan Voyager. Bit hard then 5-10 years later to try and patent something that is already flying.

It would / should be prior art, but the Apple v Samsung patent case has kind of blown a hole in the whole patent system.
BV
 
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RE: A350 Prototypes Production Thread Part 5

Tue Sep 04, 2012 1:30 pm

Why dont they have raked tips like Boeing?
 
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RE: A350 Prototypes Production Thread Part 5

Tue Sep 04, 2012 1:47 pm

Quoting ferpe (Reply 31):
While we wait for the wingboxes to appear (I don't think we will see full wings for the ES aka MSN5000) here is another piece that will be put onto the MSN001 wings. These are made by FACC, an Austrian tier 1.

FACC are also manufacturing the 737NG and 757-200 winglets, so Airbus is not taking any chances in this area.
 
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RE: A350 Prototypes Production Thread Part 5

Tue Sep 04, 2012 3:27 pm

Quoting sweair (Reply 37):
Why dont they have raked tips like Boeing?

Two reasons:

- the raked tip is patented by Boeing

- The A350 is with it's 64.8m right on the limit for a category E aircraft. With a winglet design you can have an effective wingspan (the span countering induced drag) of some 66m within the 65m E category limit as the winglet builds span in the vertical dimension as well.

The 787 with it's 60.1 m span including the raked tips is well below this limit and could use the raked tips for an effective wingspan of some 59.2 m with minimal structural weight (they don't cause high torsion loads like winglets do, see threads in tech/ops). This less stiff wingbox seems to necessitate an inboard high-speed aileron however, it has it's own plus and minuses (see A vs B wing thread i tech/ops).

Horses for courses as usual  .

[Edited 2012-09-04 08:28:52]
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RE: A350 Prototypes Production Thread Part 5

Tue Sep 04, 2012 3:28 pm

Just read this on the Airbus website:

Quote:

First A350 XWB wing arrives in Toulouse for ground tests


4 SEPTEMBER 2012 PRESS RELEASE
The first wing for the A350 XWB has arrived at Airbus’ final assembly line in Toulouse (France) where the new generation Airbus wide-body aircraft is being assembled. This first wing, which will not fly, is destined for the A350 XWB airframe used for static structural tests on the ground that all new aircraft undergo as part of their certification process. The A350 XWB wings, as for all Airbus aircraft, are made at Airbus’ Broughton (UK) site.
The A350 XWB wing covers are 32 metres long by six metres wide, making them the biggest single civil aviation parts made from carbon fibre composite material. The wings’ advanced structural design and superior aerodynamics are both significant contributors to the 25% fuel saving performance of the A350 XWB.

Link to the full article with pictures: http://www.airbus.com/newsevents/new...ives-in-toulouse-for-ground-tests/
 
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RE: A350 Prototypes Production Thread Part 5

Tue Sep 04, 2012 3:53 pm

So finally the first wing is there (right hand one), I hoped to put up the low res pictures and the most interesting high res one here but my picture service is having some drama just now, someone else might help or I will get it done once they get their service cured   .
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RE: A350 Prototypes Production Thread Part 5

Tue Sep 04, 2012 5:47 pm

High-res pictures are available at http://www.airbus.com/galleries/photo-gallery/
Close, but no cigar http://vine.co/v/OjqeYWWpVWK
 
tdscanuck
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RE: A350 Prototypes Production Thread Part 5

Tue Sep 04, 2012 8:36 pm

Quoting zeke (Reply 33):
Airbus has also filed suit claiming the APB patent should be revoked. If you look at the 15m racing gliders in the 1980s like the Masak Scimitar, they already had blended winglets, so did the Rutan Voyager. Bit hard then 5-10 years later to try and patent something that is already flying.

APB's patent is specifically about how they design the blend. As long as their way of designing the blend is different than what the gliders or Rutan did, the patent should withstand a prior art challenge.

Tom.
 
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RE: A350 Prototypes Production Thread Part 5

Tue Sep 04, 2012 9:20 pm

Quoting os787 (Reply 38):
FACC are also manufacturing the 737NG and 757-200 winglets, so Airbus is not taking any chances in this area.

I'm not so sure about that showing that they are taking no chances. The 737NG winglet at least is build to print and I suspect the 757-200 winglets are as well. Have they taken on design responsibility this time?

Not only that, but they were not the original manufacturer of the 737NG winglet (we built them here at Boeing Aerostructures Australia first) so the kinks had already been worked out of the manufacturing process.
 
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RE: A350 Prototypes Production Thread Part 5

Tue Sep 04, 2012 10:36 pm

Quoting tdscanuck (Reply 43):

APB's patent is specifically about how they design the blend. As long as their way of designing the blend is different than what the gliders or Rutan did, the patent should withstand a prior art challenge.

It is a matter of chess, Airbus has their own patent for them, US20110192937.
We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
 
ferpe
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RE: A350 Prototypes Production Thread Part 5

Wed Sep 05, 2012 8:46 am

To talk about the wings we need some pictures, here the overview where one can see that the leading edge below the slats/droop nose is apparently stress carrying structure as it is included in the ES test:




One can also see the different aileron and flap hinge braces extending backwards from the trailing edge. The inner flap hinge has his mate sitting inside the wingroot fairing. The two outermost hinges for the stream-wise deflecting outboard flaps are interesting, they have non aligning hinge axes, this means the flaps have ball-joint hinge bushings IMO:




Finally a closeup of the wingroot join aera (the ammis call it side-of-body join, IMO misleading, it is a join of the center wingbox and the winghalves. The wingbox then interfaces the fuselage at the side of body join but from a load perspective this loadpath has little with the wing-halves to do (or am I mistaken?) ) :

http://i298.photobucket.com/albums/mm262/ferpe_bucket/A350XWB_wing_61.jpg


Here also a zoom of the famous ribfeet and how they interface to the wingskin with 2 fasteners. For the A380 these were Al parts fastened onto a stiff CFRP rib, thus they took all the twisting and turning as the wing expanded and contracted due to temp among other things. Here they are integral to a big AlLi plank, thus the whole rib will participate in the twist and turn   :

http://i298.photobucket.com/albums/mm262/ferpe_bucket/Wingribfeetcloseup.jpg
thus evening out any local stress centers .

[Edited 2012-09-05 02:08:13]
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Ruscoe
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RE: A350 Prototypes Production Thread Part 5

Wed Sep 05, 2012 9:17 am

The leading edge looks dead straight, as compared with the 787 wing.

One presumes that the complex shape of the 787 wing is for a reason, so if anyone can compare and contrast the two wings, and the different design philosophies of the actual wing shape this layman would be most appreciative.

Ruscoe
 
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RE: A350 Prototypes Production Thread Part 5

Wed Sep 05, 2012 9:24 am

Quoting ferpe (Reply 46):
For the A380 these were Al parts fastened onto a stiff CFRP rib, thus they took all the twisting and turning as the wing expanded and contracted due to temp among other things. Here they are integral to a big AlLi plank, thus the whole rib will participate in the twist and turn

The A380 has a number of different rib configurations, some composite, some AL, some hybrid. I assume the A350 is the same.
We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
 
ferpe
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RE: A350 Prototypes Production Thread Part 5

Wed Sep 05, 2012 10:38 am

Quoting zeke (Reply 48):
The A380 has a number of different rib configurations, some composite, some AL, some hybrid. I assume the A350 is the same.

You are correct, I simplified to much. The ones which has got problems are the type I described IIRC. IFAIK the 350 only have ALLi plank type ribs, seems A will change some of the A380 CFRP/Al ones to this type in future production.


I guess it is:

- simpler and cheaper to manufacture (every rib position has it's unique shape (they are not even equal for same position on left and right wing-halves) so once you have the unique 3D shape for every rib you generate the CNC program and load the plank, x hours later you have your rib)

- more resilient (or less sensitive to miss-calculations of the stress picture)

- for a rather small loss in weight efficiency.


There is a story from the test wing that A did in one of the first parts of this thread where they took the decision that hybrid CFRP ribs were not worth the effort. It might be that the ribs are mostly loaded in compression, as CM wrote re the 787 keel beam it was made of Al as it is superior (or at least stack up very well) to CFRP for compressive load conditions.

[Edited 2012-09-05 03:41:56]
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