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."
flyglobal From Germany, joined Mar 2008, 502 posts, RR: 3 Reply 5, posted (8 months 4 weeks 7 hours ago) and read 54536 times:
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.
ferpe From France, joined Nov 2010, 1773 posts, RR: 56 Reply 6, posted (8 months 4 weeks 6 hours ago) and read 54495 times:
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?
CM From , joined Dec 1969, posts, RR: Reply 10, posted (8 months 3 weeks 3 days 12 hours ago) and read 51979 times:
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.
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.
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 From United Kingdom, joined Jan 2005, 9136 posts, RR: 96 Reply 13, posted (8 months 3 weeks 3 days 2 hours ago) and read 51322 times:
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".....
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
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:
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
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.
So how does out normal discussed frames stack up in this context. In fact pretty well (click on the table to see better):
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).
astuteman From United Kingdom, joined Jan 2005, 9136 posts, RR: 96 Reply 16, posted (8 months 3 weeks 2 days 21 hours ago) and read 50747 times:
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..
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.
zeke From Hong Kong, joined Dec 2006, 7725 posts, RR: 73 Reply 18, posted (8 months 3 weeks 2 days 8 hours ago) and read 50036 times:
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).
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
ferpe From France, joined Nov 2010, 1773 posts, RR: 56 Reply 20, posted (8 months 3 weeks 2 days 7 hours ago) and read 49968 times:
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"
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.
tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80 Reply 21, posted (8 months 3 weeks 2 days 6 hours ago) and read 49784 times:
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.
astuteman From United Kingdom, joined Jan 2005, 9136 posts, RR: 96 Reply 22, posted (8 months 3 weeks 2 days 5 hours ago) and read 49748 times:
Quoting CM (Reply 17): I think you mean the spec given to the customer?
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
CM From , joined Dec 1969, posts, RR: Reply 23, posted (8 months 3 weeks 2 days 3 hours ago) and read 49460 times:
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.
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.
ferpe From France, joined Nov 2010, 1773 posts, RR: 56 Reply 24, posted (8 months 3 weeks 1 day 22 hours ago) and read 49200 times:
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.
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 :
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:
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 : 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]
Non French in France
25 EPA001: Probably yes. But, the extended version of your post is highly appreciated by me.
26 CM: 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......
27 astuteman: 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 seri
28 ferpe: 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
29 ferpe: You comment about 787 shallow airfoil at the wing root of course get me to this picture from earlier in the thread: It seems when measuring on these