wolbo
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 6:23 am

Quoting Poitin (Reply 47):
At the minimum. I would like to see all the frame under the cargo floor titanium or CFRP. The upper areas aren't so critical

I thought Airbus had indicated that the 'wet parts' of the 350XWB frame would be made of titanium.
 
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SEPilot
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 6:27 am

Quoting Shenzhen (Reply 45):

An airline doesn't replace a frame, they repair. Go to the FAA web site and look at Service Bulletins in the ATA 50's, and see how many inspections, repairs and modifacations are required due to corrosion and fatigue.

The point is that it can come to the point where you can no longer economically repair them.

Quoting Rheinbote (Reply 46):
ts a trade between x) having cheap aluminum frames, an aluminum floorgrid, both serving as a current return network, at the expense of *maybe* maintenance cost versus y) having expensive CFRP frames with a CFRP floorgrid but needing a dedicated current return network made of aluminum, with *maybe* a saving in maintenance. Anyone here who can do this trade with certainty? I've heard the current return network of the 787 weighs in at about 1.000 lbs. How's that?

Cessna no longer uses the airframe for current return; everything has two wires. I would not be surprised if airliners don't do that as well, even aluminum ones. The reason is that corrosion at joints can cause poor grounding and electrical malfunctions, which is a big problem with aluminum. That 1000 lbs of "current return" on the 787 I believe includes the lightning protection grid on the skin; the A350 will require this as well. The frames cannot supply electrical return; they are not connected together, at least on the diagrams I have seen
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
Shenzhen
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 6:35 am

Quoting Rheinbote (Reply 49):
Why do you need an electrical return path..... for navigation lights?

For every piece of electrical equipment inside a CFRP airframe that is non-conductive...

Certrainly digital busses aren't using the aluminum floor and frames as a conductor for very low power signals. The frames and floor beams don't run the length of the airplane, so how does it return anything from the rear of the airplane to the front of the airplane?

One would also believe that one would go to great lengths to isolate a system from the airframe, as you don't want a single source that could potentially knock out multiple systems on an airpalne?

Cheers

[Edited 2007-06-19 23:42:46]
 
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 7:04 am

Quoting SEPilot (Reply 51):
The frames cannot supply electrical return; they are not connected together, at least on the diagrams I have seen

Connected via the cabin floor grid according to the A350 technical press briefing.

Quoting SEPilot (Reply 51):
lightning protection grid on the skin; the A350 will require this as well.

Right, metallic mesh in the skins quoted in the same place.
 
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Stitch
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 7:19 am

Quoting Rheinbote (Reply 46):
Its a trade between x) having cheap aluminum frames, an aluminum floorgrid, both serving as a current return network, at the expense of *maybe* maintenance cost versus y) having expensive CFRP frames with a CFRP floorgrid but needing a dedicated current return network made of aluminum, with *maybe* a saving in maintenance. Anyone here who can do this trade with certainty? I've heard the current return network of the 787 weighs in at about 1.000 lbs. How's that?

Those savings in maintenance appear to be outweighing any weight penalty having to embed a lightning-dissipation grid into the CFRP matrix.

I know it's "hearsay" because I wasn't present at the Boeing sales presentations, so feel free to dismiss or accept it, but based on private conversations with a number of current and prospective 787 operators who were present at those presentations have noted that the positive maintenance aspect was a factor in choosing or considering the 787.

And, honestly, if the 787 looked like it was going to be a maintenance nightmare, would we be closing on 700 sales before roll-out?
 
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 7:29 am

Quoting Stitch (Reply 54):
Those savings in maintenance appear to be outweighing any weight penalty having to embed a lightning-dissipation grid into the CFRP matrix.

But if the A350 uses a CFRP skin, then they need to dissipate the effects of a lightning skrike, so there is no weight savings from the "frame/floor electrical grid" Just more spin, like ramp rash before.
Cheers
 
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 3:20 pm

Quoting Wolbo (Reply 50):
I thought Airbus had indicated that the 'wet parts' of the 350XWB frame would be made of titanium.

They did indeed.

But why spoil a good story, eh?  Smile

Regards
 
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 6:29 pm

Quoting Glideslope (Reply 33):
Quoting EI321 (Reply 5):
ith a EIS of 2013, theres still plenty of time for showboating before he ends up ordering it anyway.

The "showboating" will make 2013 a fantasy. IMO, 2015 EIS. First flight in 2013.

Now all you need to do is convince the airlines that this baseless assumption is valid and you could be in a position to give Randy a run for his money  Wink
 
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 7:10 pm

When last I worked with composites (@FD), we had a hell of a time with composites and Al, because of galvanic corrosion, that's why all the fasteners in CFRP parts were Titanium. I don't consider it prudent to put the CFRP skin onto an Al frame unless Airbus has some secret technology / idea on how to overcome this problem.

I don't see anything wrong with the "panel" approach versus the "barrel" approach, both have their advantages and drawbacks, so from an engineering point of view I'd call it a draw, but why the Al frame?

SailorOrion
 
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 7:14 pm

I think we are all missing a trick here.

If the A350 has a life of 15 years or less.. then it's going to be a "cheap disposable" plane.
If its cheap.. airlines can buy instead of lease...

if they buy instead of lease... it threatens ILFC and SUH's business... hence SUH needs to stick the knife in first hard and deep to save his company in the long term.

In simple.. the A350 threatens his business... as it makes the cost of the plane more affordable.

by comparision.. how many people in the 1950's leased a TV made of metal and weighing a ton... and now.. how many people lease a tv at all ? Why... it's cheaper, lighter and more affordable.. and the leasing companies... have gone bust.
So far in 2008 45 flights and Gold already. JFK, IAD, LGA, SIN, HKG, NRT, AKL, PPT, LAX still to book ! Home Airport LCY
 
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 7:18 pm

Quoting StarGoldLHR (Reply 59):
If the A350 has a life of 15 years or less.. then it's going to be a "cheap disposable" plane.

Who says the A350XWB will only have a life of 15 years?  

[Edited 2007-06-20 12:20:16]
 
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 7:20 pm

Quoting SailorOrion (Reply 58):

I don't see anything wrong with the "panel" approach versus the "barrel" approach, both have their advantages and drawbacks, so from an engineering point of view I'd call it a draw, but why the Al frame?

From what I heard the Boeing engineers who examined it were unanimous in their opinion that barrels was the better way to go, and the rumors that I saw posted here (granted, they were only rumors) were that the Airbus engineers were unanimous in favoring barrels as well. As an engineer myself I see no advantages to the panels except that they are easier to manufacture. Granted, that is often the determining factor in engineering, but when your competitor is doing it the better way it does look bad.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
Danny
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 7:21 pm

Quoting SEPilot (Reply 61):
From what I heard the Boeing engineers who examined it were unanimous in their opinion that barrels was the better way to go, and the rumors that I saw posted here (granted, they were only rumors) were that the Airbus engineers were unanimous in favoring barrels as well.

This is factually wrong rubbish.
 
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 7:30 pm

Quoting Wolbo (Reply 60):
Who says the A350XWB will only have a life of 15 years?

Airbus..

Quoting Poitin (Reply 9):
This is clearly his big issue with the A350. Clark said "We only need them for 15 years" with the implication that he will scrap them, but SUH is not able to write off the millions of dollars like EK can.
So far in 2008 45 flights and Gold already. JFK, IAD, LGA, SIN, HKG, NRT, AKL, PPT, LAX still to book ! Home Airport LCY
 
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 7:42 pm

Quoting Danny (Reply 62):
This is factually wrong rubbish.

If you're going to make a blatant statement like that back it up. I can point you to where I got my information from if you like; it may be wrong but I did not make it up. Since we are discussing conclusions that groups of engineers (of which neither of us is a part) made either they reached those conclusions or they didn't. As I said, I can find the sources that I am relying on; can you?
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
EI321
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 7:54 pm

Quoting StarGoldLHR (Reply 63):
Quoting Wolbo (Reply 60):
Who says the A350XWB will only have a life of 15 years?

Airbus..

WHEN?

Quoting StarGoldLHR (Reply 59):
If the A350 has a life of 15 years or less.. then it's going to be a "cheap disposable" plane.

So let me get this straight. Its a cheap disposable plane thats more expansive than its rival. Have you looked at the order figures this week? There are three more airbus announcements coming today alone.

Quoting SEPilot (Reply 64):
Quoting Danny (Reply 62):
This is factually wrong rubbish.

If you're going to make a blatant statement like that back it up

How can any of this be backed up when its just ROUMERS.
 
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 8:18 pm

Interesting that Mr UH considered the original A350 good enough to order it. Seems that he got embarrassed a bit when others rejected it and is now fuzzy about ordering much better XWB.

Quoting SEPilot (Reply 64):
If you're going to make a blatant statement like that back it up

There is nothing to add. What you posted about Airbus engineers is pure BS.
 
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 8:20 pm

Quoting StarGoldLHR (Reply 59):
If the A350 has a life of 15 years or less.. then it's going to be a "cheap disposable" plane.
If its cheap.. airlines can buy instead of lease...

It will not have a life of 15 years, it's just that EK doesn't intend to use them for longer than 15 years. Look at their current fleet, they are already planning the replacement for the a332's, a343's and earlier 772's. Those are nowhere near 15 years old (perhaps when the replacement aircraft arrive they will be). Just like SQ does not keep their aircraft for a very long time. Granted it's not the 5 years it used to be, but not more than 15 years, as they are also planning to replace the early 772's.
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EI321
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 8:26 pm

Quoting Kappel (Reply 67):
Quoting StarGoldLHR (Reply 59):
If the A350 has a life of 15 years or less.. then it's going to be a "cheap disposable" plane.
If its cheap.. airlines can buy instead of lease...

It will not have a life of 15 years, it's just that EK doesn't intend to use them for longer than 15 years. Look at their current fleet, they are already planning the replacement for the a332's, a343's and earlier 772's.

This is a.net - Please refrain from letting facts get in the way of a good airbus bashing roumer.
 
SailorOrion
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 8:30 pm

Quoting SEPilot (Reply 61):
From what I heard the Boeing engineers who examined it were unanimous in their opinion that barrels was the better way to go, and the rumors that I saw posted here (granted, they were only rumors) were that the Airbus engineers were unanimous in favoring barrels as well. As an engineer myself I see no advantages to the panels except that they are easier to manufacture.

I don't want to discuss whether your statement is true, but let's have a look at the technical point of view.

The biggest advantage about panels is that you can load-optimize them better, which can give you a noticeable advantage for non-circular cross sections. I'm not sure how much the 787's and 350's cross-section deviate from a circle, but I can well imagine that what method is better for one plane needs not be better for the other.

Barrels are definitely the more elegant approach because of the lower number of joints required.

SailorOrion
 
BigSky123
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 8:34 pm

Well, well. A change in the wind already?

ILFC meets with Airbus on A350, sees agreement:

Quote:
LE BOURGET, June 20 (Reuters) - Executives of International Lease Finance Corp. are meeting with Airbus (EAD.PA: Quote, Profile, Research) chief Louis Gallois at the Paris Air Show, discussing the status of ILFC's order for A350 planes.

ILFC has 16 A350s on order from Airbus but has not yet converted those into orders for Airbus' latest version of the plane, dubbed the A350 XWB.

"We're going through a normal process with Airbus," ILFC chief operating officer John Plueger told Reuters before the meeting at the Paris Air Show. "Too much has been made about the whole thing."

ILFC, the largest plane lessor by fleet value and a key customer for Airbus, forced the plane maker to go back to the drawing board on the A350 last year after comments from ILFC chief Steven Udvar-Hazy compared the plane unfavorably to Boeing Co.'s (BA.N: Quote, Profile, Research) 787 Dreamliner.

ILFC played down differences with Airbus on Wednesday, saying the A350 "is going to be a great airplane."

"We're going to come to an agreement with Airbus at some point in time," Plueger said, but emphasized there was no hurry to order a plane that wouldn't be delivered until 2014.
http://www.reuters.com/article/compa...70620
 
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 8:40 pm

"ILFC played down differences with Airbus on Wednesday, saying the A350 "is going to be a great airplane."

That was quick  Wink
 
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 9:17 pm

Quoting Danny (Reply 66):
There is nothing to add. What you posted about Airbus engineers is pure BS.

I did say it was rumor; my source was a post by Aminobwana. I have IM'd him to see if he has a published source; but for you to say it is BS without any substantiation is not credible. You can say you don't believe it; fine, you have that right. I give it credence because as an engineer I find it totally believable that engineers would come to that conclusion. There are many things in engineering that are a tradeoff; but some things are universal, and one is that any time you can simplify joints in a pressure vessel you are ahead of the game, and longitudinal joints are harder to deal with than circumferal joints. Any competent engineer will agree with this.

Quoting SailorOrion (Reply 69):

The biggest advantage about panels is that you can load-optimize them better, which can give you a noticeable advantage for non-circular cross sections. I'm not sure how much the 787's and 350's cross-section deviate from a circle, but I can well imagine that what method is better for one plane needs not be better for the other.

This would be true if you were restricted to a uniform thickness on the barrels, but as I understand the processes that Boeing is using this is not the case. They can lay it up to vary the thickness wherever they want, and so the advantage that you cite disappears.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 9:28 pm

Quoting SEPilot (Reply 72):
They can lay it up to vary the thickness wherever they want, and so the advantage that you cite disappears.

Yep, but it's still easier to do on panels  Smile

SailorOrion
 
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 9:30 pm

Quoting SailorOrion (Reply 73):

Yep, but it's still easier to do on panels

Agreed; but if you can do it the barrels are better.l
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 9:31 pm

Quoting SEPilot (Reply 74):
Agreed; but if you can do it the barrels are better.l

That's likely, but only time will tell, if only Airbus drops the Al Frame. I'm also wondering how to mate a CFRP skin with Al Frame when thinking about thermal stresses.

SailorOrion
 
EI321
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 9:33 pm

Quoting SEPilot (Reply 72):
Quoting Danny (Reply 66):
There is nothing to add. What you posted about Airbus engineers is pure BS.

I did say it was rumor; my source was a post by Aminobwana.

Enough said!
 
814NAS
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 9:46 pm

SEPilot; excuse my ignorance here, just a general question, but how thick are the panels going to be on the AB and how thick are the barrels (CFRP thickness I mean). Thanks.
 
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 9:55 pm

Quoting SailorOrion (Reply 75):
I'm also wondering how to mate a CFRP skin with Al Frame when thinking about thermal stresses.

I wonder the same.

Quoting 814NAS (Reply 77):
SEPilot; excuse my ignorance here, just a general question, but how thick are the panels going to be on the AB and how thick are the barrels (CFRP thickness I mean). Thanks.

I do not know this; I do not think it is public information yet. I would suspect that they are both about the same thickness, though.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 9:58 pm

Quoting SEPilot (Reply 78):

Thanks.
 
Poitin
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 10:08 pm

Quoting StarGoldLHR (Reply 59):
If the A350 has a life of 15 years or less.. then it's going to be a "cheap disposable" plane.
If its cheap.. airlines can buy instead of lease...

if they buy instead of lease... it threatens ILFC and SUH's business... hence SUH needs to stick the knife in first hard and deep to save his company in the long term.

In simple.. the A350 threatens his business... as it makes the cost of the plane more affordable.

While there may be economic advantages of a "disposable" airframe, buying them instead of leasing them isn't one of them. The amortization of a purchased airframe would be over 10 to 15 years under most tax codes I am familiar with. The advantage of purchasing is that you have a lower total cost, but you do not have many tax deductions. Indeed, you carry the airframe you purchased as an asset, and are able to deduct only the amount amortized during the tax year. And if you had to borrow money to purchase the airframe, you still have to pay interest,etc.

On the other hand, if you lease, you can deduct the total cost of the lease as a business expense, and not have to deal with borrowing money. That is what SUH business is based on. He as owner of the airframe amortizes it over a 15 year or so period and then "salvages" the now amortized asset for whatever he can get. Naturally, he pays taxes on whatever he gets for salvaging, but he has that all worked out. And naturally, the more money he can get from salvaging the airframe - such as selling the airplane complete for a premium, the better.

The decision to purchase verses lease is a cash flow issue, plus concerns about just how long you need the airframe. If you only need it for say 5 years, leasing is a safer way to go. If you need it for 15 years, then you look a the cash flow. If you have lots of money in the bank and don't need to borrow to buy the airframe, purchase makes sense.

From SUH's point of view, it is not the first lease that is important, but the second and perhaps third lease that makes or breaks the deal. If he buys a very popular airframe everyone wants, he can get a higher lease rate on it for at least the first lease. But let's say that there is a serious design fault in it which requires the leasee to pay out large amounts of money for unexpected maintenance, then suddenly nobody wants to lease it and so the when the airframe is return after the first lease, it sits, even though he is still paying interest on the money he borrowed to buy it.

SUH is concerned about what happens in 10 or 12 years when these planes are now sitting in the desert because nobody wants them on the second or third lease period.

As noted, I am sure Airbus can sell SUH all sorts of A350s with the proper warranty and buy-back guarantee.
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 10:20 pm

..other leasing companies like CIT don't seem to have an issue with the technology but rather see the market-potential-they just ordered 7 A350 up from previously ordered 5 units..

[Edited 2007-06-20 15:21:52]
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Poitin
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 10:26 pm

Quoting Beaucaire (Reply 81):
.other leasing companies like CIT don't seem to have an issue with the technology but rather see the market-potential-they just ordered 7 A350 up from previously ordered 5 units..

Then why is ILFC so much larger? Big grin Steve is a smarter man, and driving a harder bargain with Airbus because he can.
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Danny
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 10:30 pm

Quoting Poitin (Reply 82):
Then why is ILFC so much larger?

definitely not because they haven't order XWB yet. Check how old is ILFC vs CIT.
 
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 11:02 pm

Quoting Danny (Reply 66):

There is nothing to add. What you posted about Airbus engineers is pure BS.

For the record, I just got a response from Aminobwana. He did read it somewhere and is looking for the source, but he also has contact with people at Siemens who are working on the wiring for the A350 and this decision affects them, and they confirm that it is true. Please do not call something, even if it is a rumor (and labeled as such) as BS unless you have some evidence to back up your position.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
Thorben
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 11:36 pm

So, now SUH met with Leahy to discuss their A350 order.

http://in.biz.yahoo.com/070620/137/6h6m0.html
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justloveplanes
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 11:41 pm

Quoting SailorOrion (Reply 58):
I don't see anything wrong with the "panel" approach versus the "barrel" approach, both have their advantages and drawbacks, so from an engineering point of view I'd call it a draw, but why the Al frame?

This has been discussed in some detail in other threads, but my very strong opinion is a resounding NO, they are not a wash.

Starting with the extremely obvious: if Boeing thought panels were better, the 787 would be panels. Boeing was first out of the gate and they had total flexibility unencumbered by shedule or R&D, both of which are less for panels, to choose which way to go. They chose barrels - so much for Boeing's take on things.

Airbus' real reasons for going with panels, especially with an odd choice of an Aluminum frame under a paneled skin cannot be concluded with total certainty, but a reasonable analysis would say its schedule driven.

Airbus has already stated THIS WEEK, that changes in design would not affect EIS, which tells you what is driving the product, i.e. schedule not optimal design. SUH, Boeing, and if Tim Clark is to be believed (this one with a grain of salt) a good bit of the Airbus staff believe barrels is the way to go. SUH will settle for All Composite. I can't see how any engineer would choose a solution with more complex assembly, longer pressurized perimeter joints, dissimilar thermal expansion, less structural integrity and greater corrosive potential unless he had to. Airbus forwarded two arguments related to repair (dead) and lightning suppression (questionable difference if both use a composite skin).

Airbus had sold a bunch of A350 version 1's. They could have done fine doing that and buying time for a barrell A350XWB. I don't think half measures are in order for an All New plane, and it seems like a bad choice when you are already 5 years behind (!!).
 
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 11:44 pm

Quoting Thorben (Reply 85):
So, now SUH met with Leahy to discuss their A350 order.

Since SUH is not the end user, ultimately he will buy what his customers want. The lease rates are going to reflect what he thinks his long term costs are going to be, so his opinion is not irrelevant. If he believes that the A350 is going to have higher maintenance costs down the road he will charge more for it than for the 787, which will mean that he will probably place more 787's. But he will still buy A350's unless he is convinced that no one wants them.

[Edited 2007-06-20 16:48:33]
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
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RE: Udvar-Hazy Still Not Happy With A350XWB

Wed Jun 20, 2007 11:45 pm

Quoting Thorben (Reply 85):
So, now SUH met with Leahy to discuss their A350 order.

http://in.biz.yahoo.com/070620/137/6....html

Leahy talked about this in the press conference for CIT's order! He even said that SUH said he could mention it.
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Stitch
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RE: Udvar-Hazy Still Not Happy With A350XWB

Thu Jun 21, 2007 12:36 am

Quoting SEPilot (Reply 84):
For the record, I just got a response from Aminobwana. He did read it somewhere and is looking for the source, but he also has contact with people at Siemens who are working on the wiring for the A350 and this decision affects them, and they confirm that it is true.

Aminobwana is just the latest person to note in this forum that many (though not "unanimously") Airbus engineers are said to have preferred barrels as well, so there may be at least something to it with at least some engineers within Airbus.
 
PGNCS
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RE: Udvar-Hazy Still Not Happy With A350XWB

Thu Jun 21, 2007 1:18 am

Quoting Astuteman (Reply 29):
Airbus are specifying maintenance schedules that match or beat the 787.
I don't subscribe for one second to the notion that this is being done purely as a "me too" exercise, with NO engineering back-up. CFRP/Al structures have been around a long time, as has the issue of their corrosion.
Also, the A380 has them, the 787 has them, and the A350 has them. Other aircraft have them.
Maybe my job makes me somewhat blase about maintenance/corrosion - through the life of a nuclear sub, it has a monumental impact on the product engineering. (and again I'm nervous that I'm comparing "nautical" engineering to "aeronautical" engineering).
But my limited knowledge leaves me mystified as to why we believe it's physically impossible to engineer a "40 year" aircraft from CFRP and Al.
Might not be easy, and there might be other trade-offs that are required, in other product characteristics.

Absolutely right. The practical point is that for WHATEVER reason Airbus has chosen a design tradeoff that is not popular with either Udvar-Hazy or the myriad armchair "experts" on this forum. I don't know exactly why certain design choices are made, and neither do the others contributing to this discussion. If Udvar-Hazy doesn't like the plane, he doesn't have to buy it. That doesn't mean in an of itself that Airbus should change it, he can be wrong too.

Quoting Astuteman (Reply 29):
Quoting Aminobwana (Reply 19):
If the A350 ages more rapidly than the B787

We (on A-net) seem to have written this off as a given.
What if it doesn't?

Exactly. Nobody knows what the relative performance of these two aircraft will be yet. Whether or not some people on this site want to admit it or not, Airbus builds world-class aircraft, and their personnel aren't foolish by any means. I have flown most Boeing airliners as well as the Airbus FBW aircraft, and from my perspective I would ALWAYS choose to fly Airbus.

Quoting Astuteman (Reply 38):
Quoting Shenzhen (Reply 36):
Its the access. You need to strip the airplane of the interior to do a proper inspection. 6+ weeks out of service

I hear you.
But it still doesn't answer my question.
If you only have to do this once every 12 years, what proportion of the TOTAL maintenance spend is it?
And are you saying that the 787 won't need to have the linings stripped out every 12 years or so, regardless of whether its frames are CFRP or otherwise?
Through-life, how significant is it?

This is exactly on target. All designs are compromises and maintenance compromises are part of those decisions. Astuteman, welcome to my respected users list: you are pragmatic and openminded.

Quoting SEPilot (Reply 61):
From what I heard the Boeing engineers who examined it were unanimous in their opinion that barrels was the better way to go, and the rumors that I saw posted here (granted, they were only rumors) were that the Airbus engineers were unanimous in favoring barrels as well.

First and foremost "Airbus engineers" represents a diverse group of thousands, I seriously doubt you will get a unanimous opinion from a group so large on anything. Secondly, if you are so in the know on this issue, let us know your source, please.
 
EI321
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RE: Udvar-Hazy Still Not Happy With A350XWB

Thu Jun 21, 2007 1:36 am

Quoting Stitch (Reply 89):
Aminobwana is just the latest person to note in this forum that many (though not "unanimously") Airbus engineers are said to have preferred barrels as well

Did he state any sources? I tend to pour a whole drum of salt on stuff Aminobwana says out with before reading it.

Assuming that barrels are better, I have some questions:

1) Composite Content.
The 787 will have 50% composites and the A350 will have 52% composites. If the A350 was to have barrel construction, how would they get around the problem of lightening conductivity? This has been stated as one of the main advantages of the alu frames, and I dont think Gallois is designing the A350 so I assume the alu frames were thought up by the engineers.

2) Weight
It was originally assumed that the barrels allow for a reduction in weight, because less joints and bolts are needed, although this assertion seems to have died somewhat with the realisation that the Panel approach allows for the optimisation of the panel thickness. I note that nobody (inc randy) has attempted to inform us exactly how much weight we are talking about. Is there a reason? Is the difference that small either way?

3) Aerodynamics.
Its been said that the smaller number of bolts on the barrels gives a positive contribution to aerodynamics, but like the above question, why has nobody (inc boeing by the looks of things) cared to point out how much the difference will be?

4) Maintenance costs.
Like the two points above, its been claimed that the barrels are cheaper to maintain due to the smaller number of bolts. Again, why wont they tell us how much cheaper?

5) Corrosion.
Like the last three points, its been said that the barrels allow the dreamliner to have a longer servicable life than that of panels. Does anybody know what the design life of the 787 & A350 will by in terms of cycles? What is the difference and how much of it is attributed to the fuselage design?

[Edited 2007-06-20 18:39:04]
 
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RE: Udvar-Hazy Still Not Happy With A350XWB

Thu Jun 21, 2007 1:52 am

Quoting Thorben (Reply 85):
So, now SUH met with Leahy to discuss their A350 order.

http://in.biz.yahoo.com/070620/137/6....html

I would LOVE to be a fly on the wall of that meeting! Remember SUH does have 16 A350's on order, the Mark I. Those were all aluminum aircraft, but Steve discovered he couldn't rent them.

Quoting SEPilot (Reply 87):
But he will still buy A350's unless he is convinced that no one wants them.

Oh, there are plenty of people who would want them -- no question of that. The big question is what is the cost of ownership to SUH and how does he make money on it. I am sure he will get the warranties and guarantees from Airbus first. This is all a business ploy on his part and a damn good one.
Now so, have ye time fer a pint?
 
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SEPilot
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RE: Udvar-Hazy Still Not Happy With A350XWB

Thu Jun 21, 2007 2:00 am

Quoting EI321 (Reply 91):
Did he state any sources? I tend to pour a whole drum of salt on stuff Aminobwana says out with before reading it.

He said in a private message to me that it was published but he can not immediately say where but he also has personal contacts at Siemens who say the same thing; see my reply #84.

Quoting EI321 (Reply 91):
1) Composite Content.
The 787 will have 50% composites and the A350 will have 52% composites. If the A350 was to have barrel construction, how would they get around the problem of lightening conductivity? This has been stated as one of the main advantages of the alu frames, and I dont think Gallois is designing the A350 so I assume the alu frames were thought up by the engineers.

Composite content is really a red herring; what matters is weight and maintenance issues. A 2% difference in composite content is trivial. One place that might account for it is that the panels need flanges for the longitudinal joints, which are not needed on the barrels. This will increase the amount of composite over other material without any corresponding weight savings elsewhere. The aluminum frames will not help lightning protection; that has to be done on the skin. The A350 will need the same wire mesh as the 787.

Quoting EI321 (Reply 91):
2) Weight
It was originally assumed that the barrels allow for a reduction in weight, because less joints and bolts are needed, although this assertion seems to have died somewhat with the realisation that the Panel approach allows for the optimisation of the panel thickness. I note that nobody (inc randy) has attempted to inform us exactly how much weight we are talking about. Is there a reason? Is the difference that small either way?

Again, there is a lot of smoke being blown here. Boeing has the ability to vary the thickness of the barrels wherever and however they want. Weight again is not the primary issue here; maintenance is.

Quoting EI321 (Reply 91):
3) Aerodynamics.
Its been said that the smaller number of bolts on the barrels gives a positive contribution to aerodynamics, but like the above question, why has nobody (inc boeing by the looks of things) cared to point out how much the difference will be?

More smoke here. The difference is pretty small.

Quoting EI321 (Reply 91):
4) Maintenance costs.
Like the two points above, its been claimed that the barrels are cheaper to maintain due to the smaller number of bolts. Again, why wont they tell us how much cheaper?

The real answer is that probably nobody knows. The barrel approach avoids many areas that will have to be inspected on the panel approach; the aluminum frames need to be inspected for corrosion and fatigue. The fasteners in the longitudinal joints also need to be inspected, as well as the sealing of the joints. My understanding is that the CFRP structures need to be ultrasonically tested for damage, but this is far easier and less labor intensive that typical aluminum airframe inspections.

Quoting EI321 (Reply 91):
5) Corrosion.
Like the last three points, its been said that the barrels allow the dreamliner to have a longer servicable life that panels. Does anybody know what the design life of the 787 & A350 will by in terms of cycles?

I don't know that this has been established, but I can envision that the 787 will have no predetermined life limit in terms of cycles. The A350 may or may not have the same; it will depend on the amount of fatigue the aluminum frames are expected to see.
As an engineer myself I am completely in favor of barrels for these and a number of other reasons. I have had a number of interchanges with Astuteman on this topic, and while he agrees with my ultimate conclusion he disagrees with how much importance to place on it. I will confess to being somewhat of a purist, and as such tend to magnify differences when I perceive one approach to be clearly superior. So perhaps I have overemphasized the difference; but I regard it as quite significant.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
EI321
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RE: Udvar-Hazy Still Not Happy With A350XWB

Thu Jun 21, 2007 2:02 am

Quoting Poitin (Reply 92):
Remember SUH does have 16 A350's on order, the Mark I. Those were all aluminum aircraft

It wasen't all aluminium! Im not sure how much the old A350 had but it was up to 30%, and the A350XWB is not an all composite aircraft.

Quoting Poitin (Reply 92):
Quoting SEPilot (Reply 87):
But he will still buy A350's unless he is convinced that no one wants them.

Oh, there are plenty of people who would want them -- no question of that.

True. I think this is becoming truer by the day. And remember they would have at least 7* years to place them, Vs 3-4 years when they ordered the 787.

*I highly doubt ILFC could take delivery before 2014.
 
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SEPilot
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RE: Udvar-Hazy Still Not Happy With A350XWB

Thu Jun 21, 2007 2:08 am

Quoting Poitin (Reply 92):
The big question is what is the cost of ownership to SUH and how does he make money on it.

I would say it's how many will he be able to lease at the rates he feels he has to charge for what he perceives that they will cost him over the long term. He's going to make sure that he doesn't lose money on them.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
Poitin
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RE: Udvar-Hazy Still Not Happy With A350XWB

Thu Jun 21, 2007 2:10 am

Quoting SEPilot (Reply 93):
The real answer is that probably nobody knows. The barrel approach avoids many areas that will have to be inspected on the panel approach; the aluminum frames need to be inspected for corrosion and fatigue. The fasteners in the longitudinal joints also need to be inspected, as well as the sealing of the joints. My understanding is that the CFRP structures need to be ultrasonically tested for damage, but this is far easier and less labor intensive that typical aluminum airframe inspections.

This is an excellent summary of the issues the A350 has with regard to maintenance costs. Now the question is does it matter? If the price of the aircraft is right, and Airbus warrants the airframe for a reasonable service life, no. Both of those do effect the profit Airbus makes, however.

One engineer I know who is not an A.net member pointed to the longitudinal joints and said "They are just a split waiting to happen." I can't share that opinion without more details on how the joint will be made and with what sort of fasteners (Aluminum, Stainless Steel, or Titanium) as well as the design of the seal.
Now so, have ye time fer a pint?
 
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SEPilot
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RE: Udvar-Hazy Still Not Happy With A350XWB

Thu Jun 21, 2007 2:18 am

Quoting Poitin (Reply 96):
One engineer I know who is not an A.net member pointed to the longitudinal joints and said "They are just a split waiting to happen." I can't share that opinion without more details on how the joint will be made and with what sort of fasteners (Aluminum, Stainless Steel, or Titanium) as well as the design of the seal.

Thanks for that. I have been jumped on by Danny and others for believing the rumor that Airbus engineers were unanimous in favoring barrels. My point, which you have just reinforced, is that any competent engineer will see it the same way.

[Edited 2007-06-20 19:18:45]
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
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scbriml
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RE: Udvar-Hazy Still Not Happy With A350XWB

Thu Jun 21, 2007 2:18 am

Quoting Poitin (Reply 96):
"They are just a split waiting to happen."

Is this any different to any longitudinal join on any pressurised plane today?
Time flies like an arrow. Fruit flies like a banana!
There are 10 types of people in the World - those that understand binary and those that don't.
 
Shenzhen
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RE: Udvar-Hazy Still Not Happy With A350XWB

Thu Jun 21, 2007 2:37 am

Quoting EI321 (Reply 91):
1) Composite Content.
The 787 will have 50% composites and the A350 will have 52% composites. If the A350 was to have barrel construction, how would they get around the problem of lightening conductivity? This has been stated as one of the main advantages of the alu frames, and I dont think Gallois is designing the A350 so I assume the alu frames were thought up by the engineers.

How does Airbus get around the problem of lightening conductivity with aluminum frames and floor beams. I don't think the lightning strikes the frames and floor beams, but the skins. I doubt they want to conduct this kind of energy thru a fastener to the the frame, as it would most likely melt it.

Cheers

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