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autothrust
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A350XBW Key To Success : GE Engine Necessary?

Tue Nov 21, 2006 8:22 pm

I'm asking me if the A350XBW will have success if only RR would supply Engines? As much as i like RR, didn't AF buy the 777 because the GE-90?
In my opinion a GE engine is a must for the A350XBW variants to get a fair amount of the market.

In other post there are discussions that GE rather would supply smaller Models but not the -1000.
What do you think about this issue? Would maybe PW jump in, if GE doesn't support the A350XBW? Would the proposed Trents be efficient enough?


Please no A. vs B. no hyperbole and no bashing.

Any thoughts?

[Edited 2006-11-21 12:24:16]
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astuteman
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RE: A350XBW Key To Success : GE Engine Necessary?

Tue Nov 21, 2006 8:35 pm

Quoting AutoThrust (Thread starter):
Would maybe PW jump in, if GE doesn't support the A350XBW?

I think you're right - an alternative engine is a "must-have" in this class of aircraft (IIRC GE WILL offer the GEnx or derivative for the -800 and -900, but not the -1000).

FWIW, I think the most likely solution for the -1000 is the Engine Alliance offering a "development" of the GP7000. GE have themselves suggested this as a possible route.

How competitive would this be against a "Trent 1900" (my terminology) employing the very latest technology from the Trent 1000?
Don't know
How much work will Airbus have to do to convince the EA to sign up?
A fair bit, I suspect.
How important is not having a "common" engine choice across the entire A350 range?
Don't know again, but it's not very tidy, is it?

Regards
 
Lumberton
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RE: A350XBW Key To Success : GE Engine Necessary?

Tue Nov 21, 2006 9:12 pm

Quoting AutoThrust (Thread starter):
What do you think about this issue? Would maybe PW jump in, if GE doesn't support the A350XBW? Would the proposed Trents be efficient enough?

IMO, a choice of two engines are very important to an aircraft in this large market segment. Customers prefer a choice, if for nothing else than the absolutely cut throat price competition it affords when making a choice!
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Rj111
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RE: A350XBW Key To Success : GE Engine Necessary?

Tue Nov 21, 2006 9:31 pm

Getting two engines on board is essential for competition in both design efficiency and pricing.

I'm sure GE will join in but may not be on the -1000.

PW i belive offered the most efficient engine for the 787 but Boeing probably favoured the proven derivatives. Maybe Airbus should give them a second chance to develop the GTF.
 
kappel
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RE: A350XBW Key To Success : GE Engine Necessary?

Tue Nov 21, 2006 10:15 pm

Quoting AutoThrust (Thread starter):
'm asking me if the A350XBW will have success if only RR would supply Engines? As much as i like RR, didn't AF buy the 777 because the GE-90?
In my opinion a GE engine is a must for the A350XBW variants to get a fair amount of the market.

Not to nitpick, but it's the a350XWB (eXtra Wide Body), not XBW.
You are absolutely right however that an engine choice is a must. GE has not signed on yet, but they have stated that they are willing to power the -800 and the -900, but not the -1000, as it competes with the 77W, which they exclusively power.

http://www.flightglobal.com/Articles...+but+entry+into+service+slips.html

This could change of course if the -1000 proves that the 77W is hopelessy outclassed by the -1000, unless RR signs an exclusivity agreement with airbus for this variant.

Quoting RJ111 (Reply 3):
Maybe Airbus should give them a second chance to develop the GTF.

I am also hoping that PW will make a comeback in the widebody segment with their own engine, but IIRC they are developing the GTF firstly for the narrowbody market.
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solnabo
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RE: A350XBW Key To Success : GE Engine Necessary?

Tue Nov 21, 2006 10:39 pm

According to The Times UK Airbus gets the green light for the 350 program.

Micke//  bigthumbsup 
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Stitch
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RE: A350XBW Key To Success : GE Engine Necessary?

Tue Nov 21, 2006 10:50 pm

Quoting Astuteman (Reply 1):
FWIW, I think the most likely solution for the -1000 is the Engine Alliance offering a "development" of the GP7000. GE have themselves suggested this as a possible route.

And I am sure the EU will be happy to lift their restriction requiring EA powerplants to be installed in sets of four.  Wink

But yes, an EA powerplant could be a viable option to help GE spread the costs a bit, though they may decide to just do it themselves since they will need higher-thrust variants of the GEnx to power the 787-10 and any larger and heavier variants Boeing wishes to consider launching, anyway.
 
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autothrust
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 12:07 am

Quoting Astuteman (Reply 1):
How much work will Airbus have to do to convince the EA to sign up?
A fair bit, I suspect.

Thats the question. I really hope GE jumps aboard.  crossfingers  Would be nice a bigger Ge-90 style for the A350

Quoting RJ111 (Reply 3):
Maybe Airbus should give them a second chance to develop the GTF.

Dont think so because they failed with the Superfan, the whole A340 program ended almost in a disaster. Thats a risk Airbus cant afford.

Quoting Kappel (Reply 4):
Not to nitpick, but it's the a350XWB (eXtra Wide Body), not XBW.

Ok thanks for correction.

Quoting Kappel (Reply 4):
http://www.flightglobal.com/Articles...+but+entry+into+service+slips.html

This could change of course if the -1000 proves that the 77W is hopelessy outclassed by the -1000, unless RR signs an exclusivity agreement with airbus for this variant.

Yes indeed, if Airbus can make the A350 much more efficient the 777 would get obsolete and GE could make a good deal and maybe change their mind.
Boeing would be forced to launch the Y3. Thanks for link.

Quoting Stitch (Reply 6):
And I am sure the EU will be happy to lift their restriction requiring EA powerplants to be installed in sets of four

Sorry for my ignorance but wich restrictions?
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trex8
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 3:10 am

Quoting AutoThrust (Reply 7):
Quoting Stitch (Reply 6):And I am sure the EU will be happy to lift their restriction requiring EA powerplants to be installed in sets of four
Sorry for my ignorance but wich restrictions?

http://www.worldlii.org/eu/cases/ECComm/1999/81.html
see section C, para 89 and preceeding few paras.
 
ZRH
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 3:14 am

As I know you also have no engine choice at the 787, only GE? Is this right?
 
brendows
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 3:16 am

Quoting ZRH (Reply 9):
As I know you also have no engine choice at the 787, only GE? Is this right?

No, you have the GEnX and the RR Trent 1000 as alternatives for the 787.
 
NYC777
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 3:17 am

Quoting ZRH (Reply 9):
As I know you also have no engine choice at the 787, only GE? Is this right?

For the 787 you have a choice between Rolls and GE.
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Stitch
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 3:17 am

Quoting ZRH (Reply 9):
As I know you also have no engine choice at the 787, only GE? Is this right?

Incorrect. The 787 is offered with Rolls-Royce Trent 1000 power or GEnx power.

The 747-8 is only available with GEnx power.
 
imiakhtar
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 3:25 am

Quoting AutoThrust (Thread starter):
As much as i like RR, didn't AF buy the 777 because the GE-90?

is there any particular reason why AF has never selected RR engines?
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trex8
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 3:39 am

Quoting Imiakhtar (Reply 13):
is there any particular reason why AF has never selected RR engines?

they had no choice with their Caravelles!
but yes in recent years they have not been big fans
 
Rj111
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 4:04 am

Quoting Imiakhtar (Reply 13):
is there any particular reason why AF has never selected RR engines?

France based Snecma have had a mentionable involvement in a lot of GE products including the Ge90, CF6 and of course a 50% share of the CFM56.

If there's a GE option going, AF will take it.
 
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glideslope
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 4:05 am

Yes, GE is a Must-Have.
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DAYflyer
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 4:41 am

Quoting RJ111 (Reply 3):

PW i belive offered the most efficient engine for the 787 but Boeing probably favoured the proven derivatives. Maybe Airbus should give them a second chance to develop the GTF.

Thats the first information I have heard of this PW engine offering. DO you have any other info on it?
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imiakhtar
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 7:32 am

Quoting RJ111 (Reply 15):
France based Snecma have had a mentionable involvement in a lot of GE products including the Ge90, CF6 and of course a 50% share of the CFM56.

Thanks for clearing that one up!  bigthumbsup 
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PM
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 9:10 am

Quoting AutoThrust (Thread starter):
Would the proposed Trents be efficient enough?

Why would a Trent not be efficient? The Trent is the most popular engine on the A330 and for many years outsold both GE and PW on the 777. Why do you assume or imply that GE would make a more efficient engine?

Quoting AutoThrust (Thread starter):
didn't AF buy the 777 because the GE-90?

I hope and believe they chose the 777 for more than just the engine.

Quoting Lumberton (Reply 2):
Customers prefer a choice, if for nothing else than the absolutely cut throat price competition it affords when making a choice!

It doesn't seem to have harmed the 777W.

Quoting Trex8 (Reply 14):
they had no choice with their Caravelles!

Some Caravelles had PW JT8s, didn't they?

Quoting RJ111 (Reply 15):
If there's a GE option going, AF will take it.

 checkmark 

Quoting Glideslope (Reply 16):
Yes, GE is a Must-Have.

The 757 seemed to manage without it.
 
trex8
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 9:21 am

Quoting PM (Reply 20):
Quoting AutoThrust (Thread starter):didn't AF buy the 777 because the GE-90?
I hope and believe they chose the 777 for more than just the engine.

true but then they chose GE when they had a choice with the 772Ers!

Quoting PM (Reply 20):
Quoting Trex8 (Reply 14):they had no choice with their Caravelles!
Some Caravelles had PW JT8s, didn't they?

yes but not the early ones where Avons were the only choice

Quoting PM (Reply 20):
Quoting Glideslope (Reply 16):Yes, GE is a Must-Have.
The 757 seemed to manage without it.

I think the point was GE is a must have for AF
 
boeing767-300
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 10:07 am

Quoting PM (Reply 20):
Why would a Trent not be efficient? The Trent is the most popular engine on the A330 and for many years outsold both GE and PW on the 777. Why do you assume or imply that GE would make a more efficient engine?

The Trent 500 is at the heart of A346 problems (fuel burn) when compared to the GE 90-115B on 77W.

Therefore that comparison is only a natural progression but as you say the Trents fitted to A330 models are far better than the Trent 500 fitted to A346.

I don't believe we have ever seen a new engine outdated so quickly as the Trent 500 on the A346. With A346 sales almost dead one wonders if Rolls Royce will ever recover the development costs and turn a profit for the programme??
 
brendows
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 10:30 am

Quoting Boeing767-300 (Reply 22):
The Trent 500 is at the heart of A346 problems (fuel burn) when compared to the GE 90-115B on 77W.

Therefore that comparison is only a natural progression but as you say the Trents fitted to A330 models are far better than the Trent 500 fitted to A346.

I don't believe we have ever seen a new engine outdated so quickly as the Trent 500 on the A346. With A346 sales almost dead one wonders if Rolls Royce will ever recover the development costs and turn a profit for the programme??

It's not only the engine, but the combination of the engine and airframe. The Trent 500s is running at a higher cruise thrust than the GE 90-115B does (compared to maximum available thrust,) and the higher drag and weight of the A346 airframe is the reason behind the higher thrust.
But yes, in addition, the lower BPR on the Trent 500s, and some other parts of the engines, makes them more inefficient than the GE 90.
 
DfwRevolution
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 10:33 am

Quoting Boeing767-300 (Reply 22):
The Trent 500 is at the heart of A346 problems (fuel burn) when compared to the GE 90-115B on 77W.

I respectfully disagree.

If anything has killed the A340-500/600, structural weight is more to blame than the engine option. The A345 is roughly 50,000 lbs heavier than the 772LR when both aircraft are empty of passengers, fuel, and cargo. That's more than a Citation X business jet in dead weight. The A346 vs. 773ER is less dramatic, but you see the point.

The Trent 500 has faced some minor issues of blade rubbing that has forced airlines to perform maintenance on engines with low wing-time, but I wouldn't blame the A345/A346 "failure" on Rolls Royce. It's unreasonable to expect a powerplant to overcome such an inefficient structural design.
 
AADC10
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 10:37 am

GE and sit back and wait to see if the A350XWB is going to proceed or go the way of the original A350 or Sonic Cruiser before they commit any resources to it. P&W has to offer an engine for A350XWB since they were shut out of the 787.

While GE has become the dominant engine supplier, there are probably enough airlines that can live with RR Trents or PWs for the A350XWB to be successful even without a GE option.
 
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lightsaber
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 11:12 am

Quoting PM (Reply 20):
Why would a Trent not be efficient? The Trent is the most popular engine on the A330 and for many years outsold both GE and PW on the 777. Why do you assume or imply that GE would make a more efficient engine?

I have to agree. Due to RR having such a good relationship with most of their customers, they are more required than GE. Why I'm a Pratt fan.. I know they're in the penalty box. Pratt was the #1 engine on the A330 until they botched the 72k thrust upgrade. This opened the door for the Trent and the market never looked back. (The A332 *really* needs that extra 4k of thrust, it makes too big of a difference in payload.)

What does the A350 need from its engine?
1. Efficiency. Much better efficiency than the GE-90. Another GE-90 would not sell the A350
2. Thrust growth for the various models.
3. Hot high performance (e.g., EK at DXB, UA from DEN)
4. Something that makes it stick out from the 787.

That last bit gives Pratt a chance to get the GTF onto the A350. Only a chance...

How can the engine be more efficient? Countra-rotation, next generation fan technology (ok, minor), more efficient turbines, or heaven forbid, the GTF.  bigthumbsup 

When Boeing only offered the GE-90 on the 77W, the RR customers screamed! (And Pratt realized they had a problem, post PW4098, when no Pratt customer said a thing... Pratt realized ANA and Japan airlines weren't exactly happy with them.)

Quoting Boeing767-300 (Reply 22):
The Trent 500 is at the heart of A346 problems (fuel burn) when compared to the GE 90-115B on 77W.

I would disagree. I worked on an A346 engine rebuild. With an engine that was over 10% lower TSFC than the Trents, we couldn't beat the 77W. Why? Weight. Weight is first thing you have to look at in an airframe. The Trent 500's are fine. The A346 is overweight.

Quoting Stitch (Reply 12):

Incorrect. The 787 is offered with Rolls-Royce Trent 1000 power or GEnx power.

That's quite a race right now. GE is promising 2% lower cruise fuel burn, but the triple spool has such a climb advantage that its going to be a race for a bit. Since switching engines on the 787 is going to be relatively cheap... its going to be the first design where switching engine loyalty will probably become common.

I'm going to agree that there should be two engines offered on the A350. Airbus would be foolish not to make all three engine makers compete and compete hard.

Quoting DAYflyer (Reply 17):
Thats the first information I have heard of this PW engine offering. DO you have any other info on it?

I cannot give you details, but Pratt did propose and extremely agressive design for the 787. Pratt's issue was they were not willing to be a risk sharing partner. No risk sharing... no engine on the 787. Now, it turns out that risk sharing on the 787 is going to be incredibly profitable. Oops. Also, Boeing doesn't like "agressive" designs. e.g., Boeing will probably not be the first application for a GTF.  Sad

Also, with the PW6122 debacle (post PW4098, Post PW4172, post PW4062...) no one is currently believing Pratt's TSFC or thrust growth claims.  cry  The fact is, Pratt can do one hell of an engine. But the next one is probably going to be their last shot. I hope its a GTF.  bigthumbsup  No one else is ready to do one. And yes, I've seen the RR presentations on their GTF... they're way behind Pratt on too many details.  spin  GE? not even close.

Will the A350 offer a GTF? I think they have to. Nothing else will provide an "interesting" fuel burn improvement over the 787 (except a BWB, but that tech isn't ready).

The A350 will be a 3 way race with only two winners. Who? I'm not sure. Perhaps even an IAE GTF.  Wink

Lightsaber
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PM
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 11:17 am

Quoting AADC10 (Reply 25):
P&W has to offer an engine for A350XWB since they were shut out of the 787.

I wonder if they will. It seems unlikely that there would be any other applications for such a PW engine in the forseeable future. So they'd be swallowing the considerable investment costs to gamble on winning a decent share of an airliner that is far from guaranteed to be a success. PW could afford to put engines on just 42 DC-10s and 82 MD-11s because these engines were just versions of JT9s and PW4000s that were selling in much greater numbers elsewhere. Suppose the A350 sells just a few hundred and that PW win maybe half of that. Do they have a realistic chance of recouping their costs? It would be a risky move. RR, however, already have other not dissimilar versions of the Trent selling well elsewhere. They can gample on the A350 with much less to lose. A further factor is that PW demanded exclusvity when they were competing for the A345/A346. But it seems too late for them to try that tactic on the A350.

Frankly, I wouldn't bet on PW chasing this one alone. Maybe through the Engine Alliance but then they have to convince GE. My guess is that RR might end up with de facto exclusivity on the XWB - either that or GE will stand by their earlier offer to power the smaller versions but ignore the -1000.

Quoting AADC10 (Reply 25):
While GE has become the dominant engine supplier, there are probably enough airlines that can live with RR Trents or PWs for the A350XWB to be successful even without a GE option.

I suspect this is right. If the XWB with RR starts to look like a winner (OK - big IF!), then airlines will go for it in any case. Look at the success of the 777-300ER with GE exclusivity. If it's the 'right' airliner then airlines will buy it.
 
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Stitch
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 11:19 am

Quoting Lightsaber (Reply 26):
Pratt's issue was they were not willing to be a risk sharing partner. No risk sharing... no engine on the 787. Now, it turns out that risk sharing on the 787 is going to be incredibly profitable...Also, Boeing doesn't like "aggressive" designs (so they) will probably not be the first application for a GTF.

Do you think both "views" might change for the Y1 program?
 
atmx2000
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 11:56 am

Quoting Lightsaber (Reply 26):
I would disagree. I worked on an A346 engine rebuild. With an engine that was over 10% lower TSFC than the Trents, we couldn't beat the 77W. Why? Weight. Weight is first thing you have to look at in an airframe. The Trent 500's are fine. The A346 is overweight.

If you go back and look at what you wrote, it sounds like both the Trent and A340NG itself are problems.
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Rj111
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 12:00 pm

Quoting Boeing767-300 (Reply 22):
With A346 sales almost dead one wonders if Rolls Royce will ever recover the development costs and turn a profit for the programme??

According to delivery books there will be 560 T500s in the air one day. That's marginally behind the T800 and ahead of the T700.
 
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lightsaber
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 12:00 pm

Quoting Stitch (Reply 28):
Quoting Lightsaber (Reply 26):
Pratt's issue was they were not willing to be a risk sharing partner. No risk sharing... no engine on the 787. Now, it turns out that risk sharing on the 787 is going to be incredibly profitable...Also, Boeing doesn't like "aggressive" designs (so they) will probably not be the first application for a GTF.

Do you think both "views" might change for the Y1 program?

For Y1? No doubt. Pratt is hungry to get back into the single isle market. However, as to Boeing's dislike of the GTF... that might not change. Boeing has their reasons for not liking the GTF (I disagree... but that and four bucks gets you a latte at Starbucks...). But if Boeing does avoid the GTF for non-market driven reasons and airbus picks it up... that would be an 8% to 10% drop in fuel burn that Boeing would have to overcome.

Note: Personally I believe the Y1 is too small for a triple spool. But... if RR can prove otherwise, I'd be happy to be proven wrong. My rumor mill is hinting RR wants to offer a triple spool for Y1.

In fact, we could have a situation on Y1 where if IAE isn't given backing for a new design we could have a Pratt vs. RR GTF race!  wideeyed  Unlikely... but possible.

GE would do a contra-rotating double spool. They would claim GEnX heritage, but unless I see two rows of blades on the high turbine... I'm not going to be sold on that.  Wink

Lightsaber
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BreninTW
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 5:43 pm

Quoting Lightsaber (Reply 31):
we could have a Pratt vs. RR GTF race!

I'm displaying my ignorance again, but what is "GTF?"
 
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autothrust
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 6:33 pm

Quoting Lightsaber (Reply 26):
What does the A350 need from its engine?
1. Efficiency. Much better efficiency than the GE-90. Another GE-90 would not sell the A350
2. Thrust growth for the various models.
3. Hot high performance (e.g., EK at DXB, UA from DEN)
4. Something that makes it stick out from the 787.

That last bit gives Pratt a chance to get the GTF onto the A350. Only a chance...
Will the A350 offer a GTF? I think they have to. Nothing else will provide an "interesting" fuel burn improvement over the 787 (except a BWB, but that tech isn't ready).

Very interesting Post Lightsaber, i also would like to see PW back on the Market. The question still remains if Airbus can afford such a risk, when even Boeing didnt want.
Also would the GTF have enough thrust for the A350XBW -1000?

Would be nice, wouldnt it?  Big grin
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trex8
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 9:30 pm

Lightsaber, thanks for your great contributions again. Had a few questions.

Was the Pratt offering for the 787 also a GTF or a more conventional design?

Also isn't the present GTF development aimed at the narrow body 30K thrust range. Is Pratt actively working on something capable of powering an A350 also?

The reports I have seen say the present PW6000 based GTF will have about 10% better fuel consumption than older engines, in this context the present A320/737 ones. If a larger 70-80K thrust GTF engine were developed are you saying this will have similar increased efficiency relative to present in service engines or even beyond that and better than the GEnx and Trent 1000??
 
trex8
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 9:38 pm

Quoting RJ111 (Reply 30):
According to delivery books there will be 560 T500s in the air one day. That's marginally behind the T800 and ahead of the T700.

haha, best argument for quads there ever was!
 
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Stitch
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RE: A350XBW Key To Success : GE Engine Necessary?

Wed Nov 22, 2006 10:51 pm

Quoting Brenintw (Reply 32):
I'm displaying my ignorance again, but what is "GTF?"

Geared TurboFan. Lightsaber wrote an excellent treatise on it so a search of that term and their handle should return the post.
 
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RE: A350XBW Key To Success : GE Engine Necessary?

Thu Nov 23, 2006 4:20 am

Quoting AutoThrust (Reply 33):
The question still remains if Airbus can afford such a risk, when even Boeing didnt want.

Unfortunately, you are correct. Can Airbus afford such a risk...  scratchchin  If there are two engines available, yes. But not as the sole engine (a la 77W).

Quoting AutoThrust (Reply 33):
Also would the GTF have enough thrust for the A350XBW -1000?

This is going to be a fun question to answer!  Smile

Pratt has three major families of GTF's under consideration.
1. High thrust, 57k to 125k. This has dual stage high turbine (very high OPR and BPR). Optimized for longer (> 2000nm) flights.
2. Mid thrust. 25k to 40k. This is really conceptially identical to the above, but with a single stage HPT to save weight and MX costs. So the OPR and BPR. Compromises are made to keep the economics excellent on the 1 hour flight. Relies on the GTF to have the best efficiency for long flights.
3. A business jet/RJ variation by Pratt Canada. Thrust range of 12k to 20k lbf. Very simplified. Basically, take a Pratt 600 and ad the gearbox on the fan. Ok, the compressors are changed a bunch... (Actually, totally new concept for Pratt Canada...) But you get the idea.  spin 

Now why three concepts?
Concept #1 is only going to be good for 4,000 to 5,000 cycles between overhauls!  wideeyed  Yes, that optimized for efficiency. But its TSFC is going to be 4% to 6% less than concept #2. Concept #1 is all that would be considered for the A350. However, as long as the average flight time is over 4 hours, the fuel saved pays for the added shop time easy.

Concept #2 is a GTF, contra-rotating, evolved PW6000. Personally, the PW6000 concept is amazing. Yes, the HPC missed, but I've written on how the engineers knew that years before it was due and management wouldn't adapt. Basically, compromises in TSFC are made to ensure engine availability under extreme service. We're talking JT8D replacement.

Back to the GTF: We're talking 12,000 to 15,000 cycles between overhauls!  Smile  Smile  Smile That's what its designed for at least.  Wink We're also talking 787 like TSFC for the single isle market. GE cannot do that. RR could... but only with their GTF. (I posted in tech-ops in the why 2 engine thread on why smaller engines have a higher TSFC.)

Concept #3 is for the small jet market. Small jets just don't see as many cycles as big jets. (E.g., RJ's are estimated to have a 20 year life versus 30+ for a mainliner.) So wherever weight can be removed, it is. (This market is very weight sensitive.) Simpler compressors/turbines/combustors. Much lower OPR. Usually a notch down in materials to save costs. (Why pay another $500,000 for an engine to save $500,000 of fuel over the plane's life? Its easier to sell the cheaper plane.) But the GTF gives supperior fuel burn versus anything the competition can get out. Not as high cycle as Concept #2, but more cycles than Concept #1.

Basically, there are two large "steps" in a double spool optimization. The first is are you going for a high enough OPR to require a 2nd HPT stage and the corresponding HPC stages? Due to the high cost of the parts in the 2nd turbine stage this is really an expensive proposition. It doesn't matter if its a GTF or not. That higher OPR really reduces fuel burn (4% to 6%), but has a MX cost and weight penalty. Need I bring up the PW2000? Much of the MX nightmare of that powerplant is due to the complexity forced by having two turbine stages. (Its all or nothing...)

Yes, the V2500 has done well with a 2-stage HPT. So it isn't the MX "kiss of death". I just believe that a 1-stage HPT makes more sense with a GTF in the single isle world. However, maybe Pratt will optimize the next single isle engine for the 1.5+ hour mission. One can overcool a 2 stage HPT and get 10,000+ cycles. But you forfit about 1% fuel burn doing that. Since that cooling is only really needed at end of climb... its all about how many cycles are you optimizing for.  scratchchin  To be blunt, the optimal trade study really depends on the price of oil. $50/bbl oil says go for an overcooled 2-stage HPT. less than $40/bbl oil says go with a single stage HPT. Pratt bet wrong on the PW2000... so they're a bit gun shy.

Quoting Trex8 (Reply 34):
Was the Pratt offering for the 787 also a GTF or a more conventional design?

YES.  Wink Both! Ok, I'm not being flippant. First, Pratt offered a GTF. Boeing rejected it. So Pratt sharpened the pencils and came up with a few concepts. They ended up proposing a fairly conventional design with a lot of neat optimizatons.

Quoting Atmx2000 (Reply 29):
If you go back and look at what you wrote, it sounds like both the Trent and A340NG itself are problems.

Or I worked on a very efficient game changer.  Wink The Trent 500 is a good engine. They'll eventually ship more than 400... so RR will make their money back and an ok profit. RJ111 noted 560 engines... That's considered respectible in the widebody market.

I'm not enthralled by the Trent 500 by any means. Its an engine I know quite a bit about as I worked on an engine proposed to replace it on the A346. It simply didn't have much of the new technology we new RR could have put into it. Instead, it was a nice conservative very low cost evolution. Now, the Trent 1000... totally different story!  bigthumbsup 

Quoting Brenintw (Reply 32):

I'm displaying my ignorance again, but what is "GTF?"

As stitch noted, "Geared turbo fan." Its quieter, burns 8% to 11% less fuel than a conventional engine, but has new risks and hasn't been proven in service. I'm a HUGE fan of the concept. But there are risks. I did do a very long post on them before... so a search will tell you a lot about them.  Smile In simplist terms, all engines are struggling with their big diameter fans spinning too fast. But they have a second problem, the turbine powering the fan is spinning far too slow as is the LPC. But that slow spinning turbine is throwing away a lot of fuel.  Sad By simply putting a fixed gear reduction (about 3:1) between the two, Fuel burn drops 8% to 11%.

Curved fan blades have allowed the fan to spin faster.  Smile But fan's without the gearbox are still oversped and the turbine powering them are still at a *fraction* of their optimal RPM.

Oh:
OPR: Overall Pressure Ratio. The higher this is, the more fuel efficient an engine is.
BPR: By-Pass-ratio The higher this is, the heavier the engine, but the more efficient the cruise. The longer the mission, the higher the optimal bypass ratio is.
LPC: Low pressur compressor. RR often calls this the "booster"
HPT: High pressure turbine.

Happy Thanksgiving!

Lightsaber
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RE: A350XBW Key To Success : GE Engine Necessary?

Thu Nov 23, 2006 5:40 am

Quoting Astuteman (Reply 1):
- an alternative engine is a "must-have" in this class of aircraft (IIRC GE WILL offer the GEnx or derivative for the -800 and -900, but not the -1000).

Are you sure that an alternative is that important?

For instance the B737 never offered an alternative, and I can mention a few planes which have sold worse than that.  Wink

Also the B772LR and 773ER offer no alternative - I don't think that they suffered badly from that.

But let us wait and see. If lots of customers queue up in front of the GE HQ main door and ask for a GEnx with sufficient power for the A351, then things may change. All we know is that for the time being GE is not willing to commit to compete against RR for the A351. GE of course has their own people making up their own oppinions about how large the A351 engine market really is.
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autothrust
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RE: A350XBW Key To Success : GE Engine Necessary?

Thu Nov 23, 2006 7:32 pm

Thanks a lot Lightsaber for your very nice explanation of the GTF concepts,  thumbsup  welcome on my RU -List.

The GTF design is really compromising,in my opinion its just to way ahead and the market isnt probably ready for such a technology.

Although Airbus could catch the chance and introduce it with Trent 1000. That would be a very good sales point for the A350 program and would improve efficiency over the 777. But this wont happen sadly.
However it still will be interesting what with Airbus will come out for the A350, how the GE will change the Genx and RR the Trent 1000 derivates.

BTw: Is the Genx so much easier to maintain over the PW GTF design?

Regards
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imiakhtar
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RE: A350XBW Key To Success : GE Engine Necessary?

Fri Nov 24, 2006 3:29 am

Quoting Lightsaber (Reply 37):
OPR: Overall Pressure Ratio. The higher this is, the more fuel efficient an engine is.
BPR: By-Pass-ratio The higher this is, the heavier the engine, but the more efficient the cruise. The longer the mission, the higher the optimal bypass ratio is.
LPC: Low pressur compressor. RR often calls this the "booster"
HPT: High pressure turbine.

 veryhappy  Thanks for the explanation!
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