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Why New Engines For A380?  
User currently offlinePavlin From , joined Dec 1969, posts, RR:
Posted (8 years 8 months 13 hours ago) and read 8444 times:

Why didn't just put 777 engines on? They have the same thrust rating.
Why doenst GP2700 have the same composties as other GE90 family (it retains only its core. And vice vers, why don't they put A380 engine on 777?
Could there be GENX on A380 someday?

27 replies: All unread, showing first 25:
 
User currently offlineMolykote From United States of America, joined Aug 2005, 1343 posts, RR: 15
Reply 1, posted (8 years 8 months 12 hours ago) and read 8438 times:
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Start here:
http://www.aircraftenginedesign.com/

The GE90/PW4000/Trent800 engines of the 777 are all a generation of development behind the GP7200 and Trent 900 of the A380. Likewise, the upcoming 787 engines are going to be a generation ahead of A380 offerings.

Issues at hand are not as simple as the use of composites. Internal engine cooling and reliability are 2 examples of capabilities that have consistently improved through engine evolution (in addition to fuel efficiency, thrust output, and noise). Application of the GEnx on the A380 is (somewhat) impaired by the bleed/no-bleed operation differences of the A380/787. The 787 bleedless architecture is part of a system between the airframe and powerplant. The A380 would have to be redesigned substantially to make best use of an engine designed for bleedless operation.

I could go into a much deeper discussion here but if you do some research I think you'll begin to get an appreciation for some of the factors at work here.



Speedtape - The aspirin of aviation!
User currently offlineOyKIE From Norway, joined Jan 2006, 2755 posts, RR: 4
Reply 2, posted (8 years 8 months 11 hours ago) and read 8410 times:

Quoting Pavlin (Thread starter):
Could there be GENX on A380 someday?

I expect this to happen. The bleed air versions of the GEnx are coming, but offering a new engine on the A380 so early in the program will damage the value of the earliest A380 built. But when we get closer to 2010 and if Airbus launches the -900 I think we can see a launch of the GEnx engines on the A380.



Dream no small dream; it lacks magic. Dream large, then go make that dream real - Donald Douglas
User currently offlinePavlin From , joined Dec 1969, posts, RR:
Reply 3, posted (8 years 8 months 10 hours ago) and read 8384 times:

So there wont ne new engines dericed from A380's engines?

User currently offlineStarlionblue From Greenland, joined Feb 2004, 17172 posts, RR: 66
Reply 4, posted (8 years 8 months 9 hours ago) and read 8372 times:

It's important to remember that any airliner engine application is something of a custom job. Even the "same" engine for different planes will have significant differences in mounting, nacelle and so forth.

As for why build new engines for the 380, Molykote covers it well. Over a decade of progress has been made. Of particular interest to the 380 program is noise reduction, leading to ever larger fans (and weight headaches).



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinePelican From Germany, joined Apr 2004, 2531 posts, RR: 8
Reply 5, posted (8 years 8 months 4 hours ago) and read 8267 times:

Quoting Molykote (Reply 1):
The 787 bleedless architecture is part of a system between the airframe and powerplant. The A380 would have to be redesigned substantially to make best use of an engine designed for bleedless operation.

But then the A350 gets also GEnx engines, although modified for bleed air operation. At least this issue will be solved in the near future.

pelican


User currently offlineLehpron From United States of America, joined Jul 2001, 7028 posts, RR: 21
Reply 6, posted (8 years 8 months 3 hours ago) and read 8229 times:

Quoting Pelican (Reply 5):
The A380 would have to be redesigned substantially to make best use of an engine designed for bleedless operation.


But then the A350 gets also GEnx engines, although modified for bleed air operation

A380 (and its engines, avionic, construction, etc) has been in the works for over 10 years, begining as A3XX; A350 is somewhat of a new enterprise. The more they wait to change something the more it will cost, by then Airbus may as well restart clean-sheet.

Any future airliner will either use a new/different engine to keep up with competition and economic demands or have a derivative engine just to keep the costs down, if all other performance factors remain within an acceptable and ocmpetitive margin.  Wink



The meaning of life is curiosity; we were put on this planet to explore opportunities.
User currently offlineMolykote From United States of America, joined Aug 2005, 1343 posts, RR: 15
Reply 7, posted (8 years 7 months 4 weeks 1 day 16 hours ago) and read 8135 times:
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Quoting Pelican (Reply 5):
But then the A350 gets also GEnx engines, although modified for bleed air operation. At least this issue will be solved in the near future.

Why did I just know that someone was going to pull out the A350 engine situation? (Perhaps I should have addressed it more explicitly rather than implicitly). Please check below.

From my "Reply 1":

Quoting Molykote (Reply 1):
Application of the GEnx on the A380 is (somewhat) impaired by the bleed/no-bleed operation differences of the A380/787. The 787 bleedless architecture is part of a system between the airframe and powerplant. The A380 would have to be redesigned substantially to make best use of an engine designed for bleedless operation.

To answer your question, the installation of an engine conceived as a bleedless design on a pneumatic airframe has already been "solved" as you put it. However, to suggest that this "solution" will necessarily be equivalent in outcome to the bleedless installation is probably overstating it considering the optimization that was done on the bleedless engines to tailor them for the 787 application (Some Aviation Week articles I read while still in college noted that a clear majority of the 787 efficiency gains were going to come from the bleedless engines. I haven't heard anything since to refute this but I could be out of touch).

For what it's worth, I am an actual propulsion engineer with PW/RR/GE experience and not an airliners.net armchair CEO/engineer buzzword-abusing grandstander. Admittedly, I am a young one with much less experience/knowledge/competence than others who post here.



Speedtape - The aspirin of aviation!
User currently offlineOryx From Germany, joined Nov 2005, 126 posts, RR: 0
Reply 8, posted (8 years 7 months 4 weeks 1 day 14 hours ago) and read 8109 times:

Quoting Molykote (Reply 7):
Aviation Week articles I read while still in college noted that a clear majority of the 787 efficiency gains were going to come from the bleedless engines.

All right, but do the come from the engines or from "bleedless"? I believe that these engines are up to date in terms of efficiency and that is the biggest part of the gain for the entire system. There once was a statement on the RR-webpage that there is a gain of something like 1-2 percent on short flights down to zero on long range flights from the bleedlessnes.

The concept is promising but at the moment sometimes over-hyped.


User currently offlineMolykote From United States of America, joined Aug 2005, 1343 posts, RR: 15
Reply 9, posted (8 years 7 months 4 weeks 1 day 13 hours ago) and read 8099 times:
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Quoting Oryx (Reply 8):
All right, but do the come from the engines or from "bleedless"? I believe that these engines are up to date in terms of efficiency and that is the biggest part of the gain for the entire system. There once was a statement on the RR-webpage that there is a gain of something like 1-2 percent on short flights down to zero on long range flights from the bleedlessnes.

The concept is promising but at the moment sometimes over-hyped.

Of course the gains are from the airframe/powerplant system.

The larger point here is that an engine conceived as a bleedless design is probably not going to operate at the same efficiency level when a retro-mod is applied to enable installation on a pneumatic airframe. This is not to say that improvements elsewhere in the airframe (less weight, better aerodynamics, etc) would necessarily preclude an aircraft with conventional bleeds from outperforming an aircraft without bleeds.

Assume that we have 2 engines. Both make 70,000lb thrust and have the same TSFC and weight.
Engine 1 is a bleedless design. (installed on a bleedless airframe)
Engine 2 is a conventional bleed design. (installed on a pneumatic airframe)

Install engine 1 (adapted for conventional bleed operation) on airframe 2 and we can reasonably expect efficiency to drop by some unknown amount.

I am not attributing all or even most of the performance gain of these bleedless engines to the no-bleed architecture. I am simply pointing out that the engine designs as a whole have been optimized for operation in a bleedless environment.

It's worth noting that the touted efficiency of the 787 also comes from the airframe/systems weight that the bleedless engine allows the aircraft to shed rather than the efficiency gained from bleedless engine operation alone.



Speedtape - The aspirin of aviation!
User currently offlineOryx From Germany, joined Nov 2005, 126 posts, RR: 0
Reply 10, posted (8 years 7 months 4 weeks 1 day 12 hours ago) and read 8077 times:

Quoting Molykote (Reply 9):
Install engine 1 (adapted for conventional bleed operation) on airframe 2 and we can reasonably expect efficiency to drop by some unknown amount.

That's exactly the point. There is another degree of freedom for the optimisation of the engine when one does not have to take the bleed demand into account. Additionally pneumatics are not the most efficient way of transporting energy (even if i.e. a pneumatic starter will be lighter than an electric one due to the extremely high power density of its turbine). As far as I know this leads to a gain of something like 0-2 percent in fuel consumption with todays technology.

I just do not like it when people atrribute the entire efficiency gain of the 787 engines only to the no-bleed concept.


User currently offlineMolykote From United States of America, joined Aug 2005, 1343 posts, RR: 15
Reply 11, posted (8 years 7 months 4 weeks 1 day 11 hours ago) and read 8063 times:
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Quoting Oryx (Reply 10):
I just do not like it when people atrribute the entire efficiency gain of the 787 engines only to the no-bleed concept.

Neither do I.

My first post pretty much outlined all I have to say on this issue but in expanding on one or two points in subsequent posts my comments may not have been framed in the same context as "Reply 1".

This comment probably could have been worded better:

Quoting Molykote (Reply 7):
(Some Aviation Week articles I read while still in college noted that a clear majority of the 787 efficiency gains were going to come from the bleedless engines. I haven't heard anything since to refute this but I could be out of touch).

However, my preceeding statement did frame the advantage as an optimization for bleedless operation rather than attributing the advantage solely to bleedless design (as opposed to overall engine/airframe integration to the bleedless concept).

We need some more tech/ops threads like this one (with real content).



Speedtape - The aspirin of aviation!
User currently offlineAirbusA6 From United Kingdom, joined Apr 2005, 2036 posts, RR: 0
Reply 12, posted (8 years 7 months 4 weeks 13 hours ago) and read 7892 times:

I recall RR saying that the Trent 900 on the A380 was the biggest engine they's ever made, as in the physically largest, as it's bigger than the Trent 800s on the 777 even though it's less powerful than most of them.

I think the extra size makes it quieter?



it's the bus to stansted (now renamed national express a4 to ruin my username)
User currently offlineZeke From Hong Kong, joined Dec 2006, 9229 posts, RR: 76
Reply 13, posted (8 years 7 months 4 weeks 13 hours ago) and read 7887 times:

Quoting AirbusA6 (Reply 12):
I recall RR saying that the Trent 900 on the A380 was the biggest engine they's ever made, as in the physically largest, as it's bigger than the Trent 800s on the 777 even though it's less powerful than most of them.

From memory they did build one Trent for the 773ER, that engine became the basis for the Trent on the A380.

Quoting Molykote (Reply 9):
It's worth noting that the touted efficiency of the 787 also comes from the airframe/systems weight that the bleedless engine allows the aircraft to shed rather than the efficiency gained from bleedless engine operation alone.

To be fair, another stage would need to be done. AFAIK the GEnx on the 747-800 will not be bleedless.

On a quad, you dont need all the additional generator the GEnx has for the 787 engine instillation, you have redundancy through multiple powerplants.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineOryx From Germany, joined Nov 2005, 126 posts, RR: 0
Reply 14, posted (8 years 7 months 4 weeks 12 hours ago) and read 7882 times:

Quoting AirbusA6 (Reply 12):
I think the extra size makes it quieter?

Yeap, that's about it. Higher drag due to larger front are and larger wetted area of the nacelle but lower noise.


User currently offlinePrebennorholm From Denmark, joined Mar 2000, 6536 posts, RR: 54
Reply 15, posted (8 years 7 months 4 weeks 3 hours ago) and read 7789 times:

Quoting Pavlin (Thread starter):
Why didn't just put 777 engines on? They have the same thrust rating.

That's exactly what they did. The Trent 900 on the A380 is nothing but a slightly scaled down Trent 800 from the B777. And with some reduced redundancies (especially electric generators) since it is made for a quad.

But very likely a Trent 1700 version will rather soon end up on the A380. Maybe the Trent 1700 will fly sooner on the A380 than on the A350?



Always keep your number of landings equal to your number of take-offs, Preben Norholm
User currently offlinePelican From Germany, joined Apr 2004, 2531 posts, RR: 8
Reply 16, posted (8 years 7 months 4 weeks 2 hours ago) and read 7786 times:

Quoting Molykote (Reply 7):

To answer your question, the installation of an engine conceived as a bleedless design on a pneumatic airframe has already been "solved" as you put it.

And this was the only point I was making. Because you didn't mention the bleed air version of the GEnx - it was just an addition to your statement. I probably misunderstood your comment.
I won't start a discussion whether bleedless GEnx will be more efficient than the A350 bleed air versions, because I just don't know and I don't pretend to do otherwise.
Hence I didn't wrote what you interpreted into my comment.

Quoting Molykote (Reply 7):
However, to suggest that this "solution" will necessarily be equivalent in outcome to the bleedless installation is probably overstating it




And I thought this wasn't civ av...


pelican

[Edited 2006-04-26 22:48:25

[Edited 2006-04-26 22:48:53]

User currently offlineTepidHalibut From Iceland, joined Dec 2004, 210 posts, RR: 6
Reply 17, posted (8 years 7 months 3 weeks 6 days 15 hours ago) and read 7718 times:

Quoting Prebennorholm (Reply 15):
The Trent 900 on the A380 is nothing but a slightly scaled down Trent 800 from the B777

Methinks you misjudge the amount of technology introduced between 1994 and 2004. Rather than just a rescaled Trent 800 (or do you mean scaled up, due to the bigger fan?) there's a lot of new stuff : contra-rotation, improved materials, major redesign of HPT and Combustor, advanced digital controls, redesigned fan-blades, etc etc.

Sure, there is a family resemblance between the Trent 800 and Trent 900, just as there is between the Trent 1000 and RB211-22C, but to damn the 900 as just a rescaling exercise is a bit unfair.

(Heck, some of my best friends are designers. If they find out that life could be easier by just photocopying the plans at 80% scale, they'll do even less work.)


User currently offlineAstuteman From United Kingdom, joined Jan 2005, 10230 posts, RR: 97
Reply 18, posted (8 years 7 months 3 weeks 6 days 7 hours ago) and read 7663 times:
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Quoting OyKIE (Reply 2):
Quoting Pavlin (Thread starter):
Could there be GENX on A380 someday?.

I think it's inevitable, but the difficulty for GE is that the engine being supplanted is a partnership with P+W (the engine alliance). What will drive it will be the avaialbility of the RR T1700 on the A380.
Of course, RR have no such problem in offering the T1700 on the A380  Smile

Quoting Molykote (Reply 1):
Application of the GEnx on the A380 is (somewhat) impaired by the bleed/no-bleed operation differences of the A380/787. The 787 bleedless architecture is part of a system between the airframe and powerplant. The A380 would have to be redesigned substantially to make best use of an engine designed for bleedless operation.

Nevertheless, the bleed-air GEnx for the A350 would still appear to have a c. 10% SFC advantage over the current A380 engines.
As I understand it, the RR T1700 is being specifically designed for bleed air use, and boasts the same, possibly even better SFC than the T1000

Quoting Prebennorholm (Reply 15):
That's exactly what they did. The Trent 900 on the A380 is nothing but a slightly scaled down Trent 800 from the B777

Actually, the T900 fan is scaled UP (from 112" to 116") to accommodate the much higher Bypass Ratio (BPR), despite the lower thrust.

Quoting Prebennorholm (Reply 15):
But very likely a Trent 1700 version will rather soon end up on the A380

Personally, I agree completely. The T1700 (like GEnx) gets it's even higher BPR from a substantial reduction in the core diameter, using some very elegant engineering, allowing the fan diameter, in fact to reduce back to 112" for a similar thrust level.
(The T1000/1700 fan also rotates some 10% slower than the fan on the T900 for a given thrust, thanks to more advanced aerodynamics, and RR attribute significant SFC gains to this.)
Regards


User currently offlineAirbusA6 From United Kingdom, joined Apr 2005, 2036 posts, RR: 0
Reply 19, posted (8 years 7 months 3 weeks 5 days 17 hours ago) and read 7581 times:

Is the GE/PW contract for the GP7200 set in stone? If Airbus wanted the GEnx on the A380, could GE ignore Pratt and go ahead anyway?


it's the bus to stansted (now renamed national express a4 to ruin my username)
User currently offlineLightsaber From United States of America, joined Jan 2005, 13520 posts, RR: 100
Reply 20, posted (8 years 7 months 3 weeks 4 days 21 hours ago) and read 7499 times:
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Quoting Pavlin (Thread starter):
Why didn't just put 777 engines on? They have the same thrust rating.



Quoting Starlionblue (Reply 4):
Molykote covers it well.

Yes, well said.

Quoting AirbusA6 (Reply 19):
Is the GE/PW contract for the GP7200 set in stone?

Pretty much. Pratt would sue GE big time if the A389 went GEnX. They are under contract for certain thrust ratings of the A380.

I would like to give a little more perspective on why the 777 engines aren't on the A380. Others including Molykote have noted they are a full generation of technology behind so I won't go over that too much. But lets look at the competition for the A380.

The A380 is anounced and all three engine makers dred the idea of a three way cat fight (a la 777, 747, etc.) so Pratt and GE team up. RR puts together a very nice Trent that impresses the customers. In fact, when I was at Pratt, the first concepts of the GP7200 were rejected by customers as uncompetitive with the Trent! So they go back to the drawing board. The GP7200 gets the high spool significantly refined. Sorry, but its a different enough flow path through the high spool to be most of a generation ahead. Why not a full generation? No contra rotation! I think that is hurting the GP7200 more than anything else.  Sad GE had to really improve the high compressor and turbine. Pratt was forced to go back and redesign the fan quite a few times to meet the required efficiencies for the A380. This wasn't to meet an airbus requirement... it was to meet or beat RR. So why on many levels the GP7200 looks like a PW4000/GE-90 morph, its really a very evolved design. Bummer they didn't put in the F-119's bearings/contra rotation.  Sad

Quoting Astuteman (Reply 18):

Nevertheless, the bleed-air GEnx for the A350 would still appear to have a c. 10% SFC advantage over the current A380 engines.

The GEnX is rumored to have a 0.510 TSFC at cruise.
The GP7200 is rumored to have about a 0.525.
PW4000 TSFC is 0.537 for comparison. All for cruise.
We're not quite talking 10% drop in fuel burn for the GEnX versus a 777. We're talking 10% versus a CF-6 on a 767.

http://www.alair.com/Commercial/pw4000.html

So the GEnX will be a little better. 0.010 to 0.015 less TSFC or 2-3% ish better than the GP7200. Coincidentally, the efficiency difference expected by adding contra-rotation.  spin  Note: due to being bleedless both the Trent 1000 and GEnX gain a significant climb fuel efficiency benefit over the GP7200.  Smile So I do expect GE to beat their promised TSFC by a little (again, a la GE-90-115).

Rolls alludes to this on their Trent 1000 home page (engine section):
http://www.rolls-royce.com/civil_aer...ucts/airlines/trent1000/engine.jsp
Personally, I'm a little suprised that the Trent 1700 didn't get a 2nd high turbine row.  Sad

I'm also suprised that if you click on the "market" in the above link that RR only has 41% market share on the 787 (anounced engine selections). While the GEnX has been getting most of the "mindshare," I'm very impressed with the Trent 1000. By pulling aircraft power off of the intermediate spool and not the high spool surge margins are improved rather than reduced when you pull aircraft power off of the high spool (a la GEnX). Thus, RR has more room to optimise the high spool compressor on their bleedless engines. I hope they use that margin well!

Lightsaber



Societies that achieve a critical mass of ideas achieve self sustaining growth; others stagnate.
User currently offlineAirbusA6 From United Kingdom, joined Apr 2005, 2036 posts, RR: 0
Reply 21, posted (8 years 7 months 3 weeks 4 days 12 hours ago) and read 7461 times:

Quoting Lightsaber (Reply 20):
Pretty much. Pratt would sue GE big time if the A389 went GEnX. They are under contract for certain thrust ratings of the A380.

Does the agreement just cover the A380? Was the GP7200 ever considered for growth 747s before the current 747-8?



it's the bus to stansted (now renamed national express a4 to ruin my username)
User currently offlineLightsaber From United States of America, joined Jan 2005, 13520 posts, RR: 100
Reply 22, posted (8 years 7 months 3 weeks 3 days 8 hours ago) and read 7395 times:
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Quoting AirbusA6 (Reply 21):

Does the agreement just cover the A380? Was the GP7200 ever considered for growth 747s before the current 747-8?

It is my understanding, the contract is purely for the A380. The GP7200 is a little big in diameter for the 747-8 anyway... 116" for the GP7270 versus the modified GEnX at 104" on the 747-8 is a better fit for the current landing gear. Since redoing landing gear costs big bucks...
http://www.aviationindustrygroup.com/index.cfm?format=1026
Note: for the 787/350 the GEnX is larger diameter: 111". I just wonder why the 747-8 gets a 3 stage booster compressor (low compressor) and the 787 & A350 get a 4 stage?  scratchchin 

Lightsaber



Societies that achieve a critical mass of ideas achieve self sustaining growth; others stagnate.
User currently offlineAstuteman From United Kingdom, joined Jan 2005, 10230 posts, RR: 97
Reply 23, posted (8 years 7 months 3 weeks 14 hours ago) and read 7094 times:
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Quoting Lightsaber (Reply 20):
Quoting Astuteman (Reply 18):

Nevertheless, the bleed-air GEnx for the A350 would still appear to have a c. 10% SFC advantage over the current A380 engines.

The GEnX is rumored to have a 0.510 TSFC at cruise.
The GP7200 is rumored to have about a 0.525.
PW4000 TSFC is 0.537 for comparison. All for cruise.
We're not quite talking 10% drop in fuel burn for the GEnX versus a 777. We're talking 10% versus a CF-6 on a 767

Thanks, Lightsaber. I was basing 10% reduction on a cruise TSFC of 0.565 for the Trent 900 that was quoted on Widebody's charts.

Do you happen to know what the T900 TSFC is?
Regards


User currently offlineLightsaber From United States of America, joined Jan 2005, 13520 posts, RR: 100
Reply 24, posted (8 years 7 months 3 weeks 4 hours ago) and read 6986 times:
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Quoting Astuteman (Reply 23):
Do you happen to know what the T900 TSFC is?

Alas, I do not have an accurate figure. Since every percent really matters... it would be dangerous for me to guess. I'll see if any of my industry sources know, but I doubt it. (My ex-RR sources left RR too long ago to have such information.)

Lightsaber



Societies that achieve a critical mass of ideas achieve self sustaining growth; others stagnate.
25 TepidHalibut : Looking at a RR AeroData booklet ( dated 2002 ), shows the Trent 900 with a cruise SFC of around 0.518, although that was in advance of first engine
26 DarkBlue : The GEnx-2B (104") has a smaller fan but a higher pressure ratio than the GEnx-1B (111"). The higher pressure ratio fan allows you to drop a stage of
27 Lightsaber : Danke. Very interesting. Nice tidbit I didn't know. Thanks. Lightsaber
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