A350XWB Construction ideas

[bits44]

Some insight into the construction details proposed for the A350XWB.



http://www.flightglobal.com/articles/20 ... -a350.html

[mmciau]

It will be interesting to see how these concepts are received and when the plane is in operation, just how the claims of "superior" efficiency match up with the claims.



Mike

[Ruscoe]

http://www.compositesworld.com/hpc/issu ... May/111535

This is an informative article on Boeings 787 composites.

Ruscoe

[achace]

Just put this in here for somewhere instaed of a new topic.

Much has been said about how Airbus will not freeze the design of XWB until late 2008.

Just read that Boeing have completed 50% of the 777F design, only 25 months after the launch order, and this is just a derivative.

Cant wait for the vitriolic responses from some sources.

Cheers
Achace

I LIKE TO STIR THE POT!

[Buzz]

Just put this in here for somewhere instaed of a new topic.

Much has been said about how Airbus will not freeze the design of XWB until late 2008.

Just read that Boeing have completed 50% of the 777F design, only 25 months after the launch order, and this is just a derivative.

You said it yourself, it's just a derivative. It's basicly a 777LR without the windows and with a strengtend floor. It's uncompairable to the A350XWB development...

I LIKE TO STIR THE POT!

Yeah! Let's have stupid A vs. B discusions liko on A.net, that would help the forum quality...

If you can't type anything usefull, than don't type anything at all.

[vc-10]

There's not much to the 777F. All the aerodynamic stuff is done, the hardest part is designing the large cargo door.....

[boomer535]

Airbus claims the A350 to have 10% less maintenance then the 787 per seat. They are comparing the A350 -900 with the smaller 787-9. It is hard for me to believe the panel on frame fuselage will have less maintenance then the one piece barrel type.

[Ruscoe]

Airbus claims the A350 to have 10% less maintenance then the 787 per seat. They are comparing the A350 -900 with the smaller 787-9. It is hard for me to believe the panel on frame fuselage will have less maintenance then the one piece barrel type.

Yep! I agree with you. Cant see where Airbus is getting the increased efficiencies over the 787, except by offering a slightly larger craft, and thereby decreasing seat costs, but the fallacy here is that Boeing can just do the same thing, since they are both 9 abreast, so when Airbus firm their specs Boeing can respond, and they already have 500+ ordered, to give the cash flow to easily do it.

Unless the 350 can go out to 10 abreast I can't see it beating the 787, but then it will be clearly competing with the 777 alone and not the 787/777.
Nevertheless the sheer size of the market should ensure the 350 is moderately successful.

[achace]

Apparantly the Trent on XWB will have a 2% lower fuel burn than the 787 Trent.

Can only guess that is the 787 electrical load that makes this difference.

The light article infers that XWB will have bleed air.

Cheers
Achace

[David747]

A350-1000 should be optimized for 10 seating abreast. It will be the largest plane in the A350 family, and will likely compete with the B777. 10 seating across would give the A350 an advantage over the 787, and will put pressure on the B777 family. Secondly the A350 would be a good replacement for the A330/A340 for customers who operate those planes. I do find the fuel burn, and maintenance claims of Airbus to be interesting, seeing that they will not adopt a composite barrel. If they manage to build an airplane that is as light as the 787, using less composites, then the A350 could have a fuel and maintenance advantage over its competitor. But I feel that since the 787 program got a head start, Boeing will be able to adopt and produce variants of the 787 that will be more efficient than the original family. This is what happened with the 777 in the 1990's. What I find interesting from this article is that John Leahy said that the A350 went through a redesigned process 3 times only, but it does seem like they went through more redesign concepts than just 3. In the end, Airbus will have to put up or shut up about the A350, its bad enough that John Leahy and Airbus management got caught napping on this, and that they tried to offer a laughable alternative to the 787.

[boomer535]

I believe the main reason why the XWB engine may be slightly more effecient then the 787 engine is the XWB engine will have a bigger fan diameter. I can't see how the A350 could go to 10 abreast seating when it is only about 5 inches wider then the 787. The seats would be pretty narrow. They would have to widen the fuselage even more for a comfortable 10 abreast but this will increase drag. Boeing could come up with a 787-10ER and even a 787-11ER. They would have to come up with a bigger wing and beefed up landing gear but I think it would be worth it. This would allow them to use the A350 engines with the biger fans. This would be a Y2.5 and would compete against the A350-900 and A350-1000 and replace the 777 PAX versions. The 777F will soldier on. This is all speculations on my part. Boeing will make up their mind once the flight data comes in for the 787 and the A350 design is frozen The next big A-B fight will be the single aisle replacement. I wonder if Airbus will stick with the CFRP panel on frame for the A320 replacement or go the one piece barrel route.

[RC20]

Av Week reported that a wider fuselage was being considered.

As for more seats, this is something of a misnomer.

The 787 is selling well because the pax number it carries, match (and very closely) the needs of the customers. Call it a real good call on Boeing part.

Upshot is, while the plane (A350) could carry 330, it there are only 250 pax on the flight, then its a net looser vs a 787 carrying the same 250 pax..

How far can you "stretch" the 787 and still have it maintain its sweet aerodynamics advantage is unknown to me. At least in the past you could only go so far. Does the use of composite expand that?

At 2 years to design freeze, the A350 can easily change (wider fuselage and or all composite). Despite all the current denials, it all sounds just like the last 3 go a rounds. If you get enough pressure from the big players, it will get changed again.

In the meantime, the 787 is going through 600 pre sold. Phew. Definitely a case of when you do not have the technology, its not best to be second.

[RC20]

Some insight into the construction details proposed for the A350XWB. html

Having read this through, I have the following observations.


Bleed Air/Electrical/Hydraulics: It sounds very much like they are taking the same (current) approach as on the fuselage, i.e. a hybrid system.
Like Boeing, they are using two starter/generators on each engine (100KW smaller each). Backing up the hydraulic system they are using electric devices.
As for the comments on electrical driven air conditioner units. Those are extremely reliable these days, and there are several options. Scroll type or screw type (my preference is scrolls and I do not know what Boeing is using on the 787. Short term there may be issues as with any new machine, but long term, I think electrical air conditioning units have no draw backs (and not being familiar with the bleed air units I can’t say if they are superior directly, other than the electrical system distribution advantages).

Use of Titanium: This very much follows Boeings design that uses titanium in those areas that may have high corrosion issues.

Skin:
Boeing is using the laying of electrical conductor on the surface, so both the same in that regards. It looks like the agree technical solution to dealing with lightening strikes.
While I can see the possible theoretical advantage of fine tuning the skin thickness to the application, does it really work in this situation? Its not a wing, it’s also a pressurized structure. So, even if the predominate aerodynamic load is sheer , you also have the heavy pressure inside pushing on that uniformly. So, you have to accommodate that as well.
It still sounds like a way of justify what they are doing because they have no choice (or to quote the one weird statement, we can remove and replace a panel if its damaged. That’s insane, you simply patch it, wound fuselage or panel, it makes no difference. That’s just spewing stuff to bamboozle people (though how they think they can bamboozle technical experts is beyond me).
Instead of 6 panels, its now 4 panels on each segment. That’s another change. Not sure if it means anything other than an adjustment in the manufacturing process meeting reality and reality saying its better to do it that way. It does mean more seams to secure.


Size:
While they make a case of aircraft getting bigger, keep in mind that now the 737 and A320 are in the same 200 pax range that the A300 was in. So, if you move up, something moves in behind you as well. The lesson may be that you stay in your growth segment, and build another aircraft to compete in the higher range, not move the model up. As there are no models than can move up to the 250 seat class, that looks like a keeper. 600 orders (and probably pushing 2000 total with options, purchase right etc) says it’s a firm segment.
Granted that single aisle were able to grow to that, but also keep in mind that the 757 lived in that segment as well (and maybe had as much to do with killing off the A300 as the 767), not to mention . Boeing is considering splitting that segment with its next offering.


Huh?”

“Another advantage of the hybrid fuselage concept is that the metallic fuselage frames, floor beams and seat rails create what Airbus calls an "electrical network" enabling a carbonfibre fuselage to emulate the electrical continuity of an all-metal fuselage, says McConnell. "This is required in a carbonfibre fuselage to provide a neutral return path for electrical equipment."

I am not familiar with aircraft wiring. But everything I have ever worked on has dedicated return neutral in the wiring . You don’t use a building for a neutral (it is bonded to itself and then grounded to ensure the structure is electrical neutral. With this type of structure you have to bond and connect it, or the potential difference gets ugly. I would think with a non conductive CRFP fuselage, that’s not an issue. Frankly it sounds like more eyewash.

[smokejumper]

There's not much to the 777F. All the aerodynamic stuff is done, the hardest part is designing the large cargo door.....

I'm not all that certain that the hard work is done. The cargo door will require a lot of redesign and calcuations. A strengthened floor requies re-designing all the supporitng members, as well as the floor itself. Cargo securement points have to be desinged to handle the heaviest loads under extreme conditions.

It is no small feat to have released 50% of the drawings in this short a time.

[RC20]

I am seeing more and more reports of people not happy with almost all aspects of the A350.

Stepping back from the fray and chewing on it further, I think these are salient facts.

1. Airbus cannot afford a failure. Unless they have solid across the board interest they will not move to production until they have it right. EADS will take the delay rather than have a bad offering on its hands.

2. That also means they have to be solid interest in the segment they are targeting. That may mean a size tweak, up or down to get it where it needs to be, as well as technology change (all composite fuselage).

The serious downside for Airbus is that Boeing is not being pressed at all. The most critical period for a new technically is the initial service offering, if you founder, it can take a lot longer to recover confidence in the product, than actually fixing the technical issue(s) . Boeing has the time to do this at their own pace, unlike previously when they were moving hard to ramping up production even before they had a bird flying. They would have almost surely stumbled.

If I am right, Airbus is going to have to re-target as well as re do the A350. The 777 looks to be safe from competition as any challenge is much further away. That means the 737 replacement comes out, hitting Airbus in their last profitable segment (keeping in mind that a lot of A330s are being built as compensation aircraft for the A380 debacle).

[Berova]

If I am right, Airbus is going to have to re-target as well as re do the A350

You're suggesting Airbus can't afford not to restart (again) the A350 when almost all observers say Airbus can't afford any further delays after handing over to Boeing a 5 year head start.

I disagree with this contention though, because as many of you have pointed out, the A350's competition is the 777 not the 787 as the press (print and electronic) constantly drone on about. Having said that, while Airbus can't afford to get the A350 wrong, they've put themselves in a situation where they really can't afford any more delays. This is simply because if Boeing guns for Airbus' bread-n-butter, it'll really be the last straw.

[DFW]

There are two possible reasons I can think of as to why Airbus is using the composite panel on aluminum frame rather than composite barrel sections.

1st possibility:
Airbus does not have the engineering or manufacturing capability to provide barrel sections of that size by 2013. There are only a small handful of manufacturers of giant filament winding machines and autoclaves. Back when I designed filament wound tanks of that size, the lead time for the winding machine was 1.5 years. Also, the analysis of such composites is the stuff that people write their Ph.D. papers on. Airbus might have been caught off guard without this engineering capability.

2nd possibility:
Airbus remains concerned about crack detention and propagation of filament wound composites. I understand that Boeing sent sample composites and sledge hammers to customers to allay their concerns. But a full loaded fuel truck can do more damage than a sledge hammer. I vaguely remember an article that stated Boeing had technology that allowed easier crack detention in the field, but can't remember specifics. Perhaps Airbus either lacks this technology or has doubts regardless.

Anyways, I'm just throwing out ideas, since that is the title of this posting.

[achace]

I believe the composite panels are inherantly stiffer than a traditional metal panel, so it is entirely possible that they need fewer frames, thus saving weight.

The XWB all up weight looks ok, and they are claiming performance that potential customers appear happy about. Walsh of BA says he is very comfortable with what he has been given.

The latest statement from Gallois is that they are now confirming guarantees, so this week is going to be very interesting.

Cheers
Achace

[Berova]

This week, interesting indeed!

If this following article is indeed true, US Airways may indeed give Airbus a huge sigh of relief:

Airbus finalizing $7 billion order for 30 A350s
http://tinyurl.com/37q932

[achace]

Mr Clark of Emirates is a very confusing gentleman!

He is now quoted as saying he does not care how Airbus build the XWB, its all about operating costs.

That I suggest definitely kills any suggestion of a composite wound barrel.

All Airbus has to do now is convince Hazy, and whatever else he may say, Hazy does listen to his customers, so if its OK for panel over frame for Emirates, we may see a change of opinion from ILFC.

Cheers
Achace