MarkC
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757 RR Engine On Wing Time

Sun Oct 22, 2006 6:14 am

I asked this, but the topic was deleted.

Anyone know the typical number of cycles that a 757 RR engine can get after a heavy overhaul? I'm not talking about the record first run engine, just the typical cycle interval.

Also, what drives the need for engine removal? Is it usually EGT, or component distress?

I keep hearing that this an advantage for the Rolls, and I'd like to know a real world number
 
Panman
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RE: 757 RR Engine On Wing Time

Sun Oct 22, 2006 6:49 am

Engines and their components are lifed. After a set amount of time they have to be removed for overhaul.

PaNmAn
 
411A
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RE: 757 RR Engine On Wing Time

Sun Oct 22, 2006 9:34 am

Don't know about the -535 on the 757, but the RR.211-524B02 and the -524B402 have quite a good reliability record on the L1011.

Average, 14,000 on the wing...some have gone to 21,000 hours.
 
dl757md
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RE: 757 RR Engine On Wing Time

Sun Oct 22, 2006 1:34 pm

Quoting Panman (Reply 1):
Engines and their components are lifed. After a set amount of time they have to be removed for overhaul.

Is that how you guys do it on your side of the pond? Here in the states engines on commercial airliners stay on the wing until they need to come off. In a nut shell they're removed on condition not for time. I thought it was that way pretty much everywhere. I thought it was a European airline that has the current record for on wing - a RB211 on a 757 with over 40,000 hours. I can't remember.

DL757Md
757 Most beautiful airliner in the sky!
 
Molykote
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RE: 757 RR Engine On Wing Time

Sun Oct 22, 2006 7:55 pm

Quoting MarkC (Thread starter):
Also, what drives the need for engine removal? Is it usually EGT, or component distress?

I keep hearing that this an advantage for the Rolls, and I'd like to know a real world number

I've got to admit that as a "gas turbine engineer" in CT I am surprised you don't have all the information you need!

In my experience, the RB211s are typically pulled due to HOC or similar problems that require a tear down to fix (point sources of failure). I can't say that I have a good average data point for you regarding a typical removal interval for this type of reason.

I also can't remember seeing an RB211 removed for general hot section distress or EGT margin loss. This is in contrast to other engines I work with.

On wing time for a 757/RB211 installation is tremendous as you suggest. This fact combined with the removal reasons I cite above suggests to me that the RB211 is a bit overbuilt for an ideal 757(-200) installation. Given the RR/PW market share on the 757, I am inclined to believe that RR provides a better product for this installation but I must admit that I don't have any PW2000 experience.
Speedtape - The aspirin of aviation!
 
MarkC
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RE: 757 RR Engine On Wing Time

Sun Oct 22, 2006 11:39 pm

Quoting Molykote (Reply 12):
On wing time for a 757/RB211 installation is tremendous as you suggest. This fact combined with the removal reasons I cite above suggests to me that the RB211 is a bit overbuilt for an ideal 757(-200) installation. Given the RR/PW market share on the 757, I am inclined to believe that RR provides a better product for this installation but I must admit that I don't have any PW2000 experience.

Its just that I keep hearing "superior reliability" or such concerning this particular aircraft application. I have no reason to dispute or believe this, I'm just looking for a number for comparison.

I know the 2's were notorious for HPT blade issues in the beginning, but its much improved. I don't know if those "superior" claims dated back to that time, or if its still the case today. Typical for a 2000 is 3,000 cycles or so. For a 757, thats in the range of 7,500 hours.

I really don't know a lot about the RR and GE products. Just curious.
 
greasespot
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RE: 757 RR Engine On Wing Time

Mon Oct 23, 2006 3:52 am

Quoting Dl757md (Reply 7):
Here in the states engines on commercial airliners stay on the wing until they need to come off. In a nut shell they're removed on condition not for time.

Most engines are on condition. However the disks still have a cycle life. So really no matter the condition and performance EVERY engine will have to come off due to a disk reaching its cycle life limit regardless of the condition of the engine.

Plus with the PW 120 series the operator can ba on condition or have a TBO....It really amazes me that some of the larger operators use the TBO method.

GS

[Edited 2006-10-22 20:52:44]
Sometimes all you can do is look them in the eye and ask " how much did your mom drink when she was pregnant with you?"
 
Molykote
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RE: 757 RR Engine On Wing Time

Mon Oct 23, 2006 12:49 pm

Quoting MarkC (Reply 13):
Its just that I keep hearing "superior reliability" or such concerning this particular aircraft application. I have no reason to dispute or believe this, I'm just looking for a number for comparison.

I know the 2's were notorious for HPT blade issues in the beginning, but its much improved. I don't know if those "superior" claims dated back to that time, or if its still the case today. Typical for a 2000 is 3,000 cycles or so. For a 757, thats in the range of 7,500 hours.

I really don't know a lot about the RR and GE products. Just curious.

I know you didn't ask about first run engines but in the last year I saw an RB211 pulled after 10 years and 36,XXX hours on wing.

I don't have this info available to me at the moment but it's probably fair to expect at least double the 7,500 hours you cite (for a PW2000) for an RB211 757-200 installation (overhauled, not first run).
Speedtape - The aspirin of aviation!
 
TheJoe
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RE: 757 RR Engine On Wing Time

Mon Oct 23, 2006 7:48 pm

Quoting TristarSteve (Reply 18):
The -535E4 has the lowest combination of in-flight shutdown rate and shop visit rate in the airline industry, a factor that has given many airlines. The -535E4 achieved the world record for on-wing life without removal for over 40,000 hours over nine years in operation. It stays on wing almost twice as long as any other engine on the airframe.

Unbelievable time on-wing hey TristarSteve? I've just finished reading a book about the development of this engine... Sure, it had it's teething problems being the world's first true three spool engine but the figures say it all don't they? A wonderful piece of engineering by Rolls-Royce, a fantastic engine to run and work on...
 
Tristarsteve
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RE: 757 RR Engine On Wing Time

Mon Oct 23, 2006 8:50 pm

Quoting TheJoe (Reply 19):
being the world's first true three spool engine

That was the RB211-22 in 1973. But the -535 has the same core (nearly).
I was involved with the -22B in the early days. Had a rearly short life to start with. We were lucky to get 1500cycles with the early engines. HPT blade life was the problem. But then a new mod blade came out the DS directionally solidified or single crystal blade and the life quadrupled.
By the way, did you know that RR has a patent on the three spool engine? That is why no-one else has done it. It makes for a much simplified LP compressor. The RB211 has only one stage of Variable guide vanes compared to the Pratt and GE rows of vgvs.
 
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jetmech
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RE: 757 RR Engine On Wing Time

Mon Oct 23, 2006 10:05 pm

Quoting TristarSteve (Reply 20):
By the way, did you know that RR has a patent on the three spool engine? That is why no-one else has done it.

I was just looking at thr RR and GE sites. For the Trent 800 series, RR quotes 14 stages of compression not including the fan, whilst for the GE90-94B, GE quotes 13 stages of compression not including the fan.

http://www.rolls-royce.com/civil_aer...ts/airlines/trent800/technical.jsp
http://www.geae.com/engines/commercial/ge90/ge90-94b.html

IIRC, one of the theoretical benefits of the 3 spool design over the 2 spool design is the fact that the compressor of a 3 spool design has the freedom to operate at a more suitable RPM. Part of the compressor of a 2 spool design is tied to the RPM of the fan.

How exactly does the theoretical benefits of the 3 spool design manifest itself in physical terms? Is the RR compressor system smaller in diameter and shorter in total length compared to a GE despite having more stages of compression?

Quoting TristarSteve (Reply 20):
The RB211 has only one stage of Variable guide vanes compared to the Pratt and GE rows of vgvs.

Yep, the VSV systems of the GE and P&W were certainly complex, but mechanical marvels nonetheless  Smile.
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
TheJoe
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RE: 757 RR Engine On Wing Time

Tue Oct 24, 2006 4:43 pm

Quoting TristarSteve (Reply 20):
By the way, did you know that RR has a patent on the three spool engine? That is why no-one else has done it. It makes for a much simplified LP compressor.

No, I didn't know that they had the patent on it... That will probably be an advantage for them down the track as more precise control over each spool becomes more of an issue for producing higher power and efficiencies. The problems you mentioned were among those I read about. They also developed a composite fan blade all that time ago, but it failed testing due to it's inability to withstand a bird strike. A shame for RR because it would have given the engine a huge benefit over the other engines of around the same power rating due to the savings in weight!

Quoting JetMech (Reply 21):
How exactly does the theoretical benefits of the 3 spool design manifest itself in physical terms? Is the RR compressor system smaller in diameter and shorter in total length compared to a GE despite having more stages of compression?

I'm not sure about this one...In the technical appraisal written by RR in 1971 all they stated was that the engine was going to be three spool for an increase in aerodynamic efficiencies as you said. As for the dimensions, I'm not entirely sure but I do think it will be an advantage for them in the future as I said before!
 
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jetmech
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RE: 757 RR Engine On Wing Time

Tue Oct 24, 2006 11:12 pm

Quoting TheJoe (Reply 22):
In the technical appraisal written by RR in 1971 all they stated was that the engine was going to be three spool for an increase in aerodynamic efficiencies as you said. As for the dimensions, I'm not entirely sure but I do think it will be an advantage for them in the future as I said before!

G'day TheJoe  Smile .IIRC, the triple spool system doesn't really start to show clear advantages until thrust levels exceed a certain value. I believe that for most thrust levels, the RR is the lightest and physically smallest engine choice on the 777  Confused.

The stated aerodynamic advantages certainly seem to be a major reason for such a design, for as TristarSteve stated, the RR only has a single stage of Variable Inlet Guide Vanes (VIGV) as opposed to the far more complex Variable Stator Vane (VSV) system of the P&W and GE.

I always thought that one of the main reasons for a 3 spool design was fuel efficiency, but it seems that RR generally suffers from a very slight fuel consumption disadvantage when compared to an equivalent GE.
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
BOE773
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RE: 757 RR Engine On Wing Time

Wed Oct 25, 2006 8:15 am

Quoting JetMech (Reply 12):
but it seems that RR generally suffers from a very slight fuel consumption disadvantage when compared to an equivalent GE.

And that is correct JetMech. RR engines do burn more fuel than GE or Pratt.
I'm surprised that you actually wrote that.
 
2H4
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RE: 757 RR Engine On Wing Time

Wed Oct 25, 2006 8:24 am




Quoting BOE773 (Reply 13):
I'm surprised that you actually wrote that.

I'm surprised he beat you to it....



2H4


Intentionally Left Blank
 
jben
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RE: 757 RR Engine On Wing Time

Wed Oct 25, 2006 11:04 am

Yes, the RR engines on the 777 do suffer from a slight disadvantage on the fuel consumption. However, compared to the GE engines, a 777 powered by Rolls Royce Trents is 7,500lbs lighter, alot of this is due to the three spool design. That is a huge weight savings for customers!

I would remind you that on the 777 models where the RR engine is offered, it is the most popular engine.
 
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jetmech
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RE: 757 RR Engine On Wing Time

Wed Oct 25, 2006 12:33 pm

Quoting BOE773 (Reply 13):

I'm surprised that you actually wrote that.

What surprises you? The fact that people actually come to A.net to have balanced and informative discussions? That people come to A.net to learn from these discussions? That people come to A.net to have an experience free from propaganda? What do you come to A.net for?

I do have a major crush on RR as I have said before, but then again, I won't let this blind me into a blissful state of ignorance. I refuse to post blatant lies that may influence more impressionable people merely for the sake of propaganda.

Being an AME (A&P) and engineer, my fascination goes beyond the sticker on the side of the nose cowl, and extends far into the nitty gritty of the technical and engineering aspects of these fascinating devices. All that I have read and intrinsically understand about the triple spool design has lead me to believe that there should ultimately be some sort of fuel consumption benefit, but this does not seem to be the case, and I am curious to know why.

Quoting BOE773 (Reply 13):
And that is correct JetMech. RR engines do burn more fuel than GE or Pratt.

Having been in the industry for quite a while, I have known about the very slight fuel consumption disadvantage of RR, but I was relieved to discover from knowledgeable posters on A.net that this was no way near as bad as I thought, and nothing near as bad as some would try and have me accept.

I also know from friends in technical services and on the engine line that come overhaul time, a lot more of a GE needs to be replaced compared to a RR. So it seems that the fuel consumption issue may be a trade off with longevity as opposed to an intrinsic advantage or disadvantage with a particular design.

The generally accepted consensus is that the triple spool design really comes into it's own for higher thrust applications such as the B777, where the RR is physically smaller and much lighter for each desired thrust level.

Anyway, don't get me wrong, I am still very much a fan of RR, and I always give a silent cheer and fist pump whenever RR wins an engine deal, and this will not change, but I will always appreciate and remain fascinated by the engines the come from the stables of GE, P&W and CFM.

In the end, the engineer and AME has a much stronger grip on JetMech than blind, unquestioning loyalty to a sticker on the side of a nose cowl.



[Edited 2006-10-25 05:38:19]

[Edited 2006-10-25 06:05:22]
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
TheJoe
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RE: 757 RR Engine On Wing Time

Wed Oct 25, 2006 2:16 pm

Quoting JetMech (Reply 12):
the triple spool system doesn't really start to show clear advantages until thrust levels exceed a certain value

That's a good point JetMech. RR will really be in a class of their own as engines get bigger and bigger...

Quoting Jben (Reply 15):
However, compared to the GE engines, a 777 powered by Rolls Royce Trents is 7,500lbs lighter, alot of this is due to the three spool design. That is a huge weight savings for customers!

Now, a 7,500lb weight saving per engine translates into useful payload for the operator of the aircraft. Which means more revenue per passenger mile flown doesn't it?

Quoting BOE773 (Reply 13):
And that is correct JetMech. RR engines do burn more fuel than GE or Pratt.
I'm surprised that you actually wrote that.

As JetMech said, a lot of us here are A & P engineers and have an interest in the nitty gritty technical side of things... Not just the brand of an engine or aeroplane. A lot of us here have an interest in all types of engines and are not going to make a decision on which is better or worse... They all have their advantages and disadvantages. When was the last time you worked on an RB211, CF6 or CFM56 BOE773?

As you said in your last post JetMech, RR engines are a lot more robust than the GE's. From an operational and maintenance point of view. When you're talking about hundreds of thousands, even millions of dollars in replacement parts, this proves to be quite an advantage. As I said before, I am not here to say which engine is better or worse than the others, I enjoy working on all of them. The figures are all there, each individual engine works well in it's own application. Hence, for the 777's, RB211 Trents seem to be the choice for the reasons mentioned by others earlier on. Being a three spool engine, they will continue to produce larger amounts of thrust. I believe three spool engines have a lot more room for development simply because they have an extra spool to play with! Two spool engines will eventually reach the limit where a lot of extra money will have to be invested for only a small benefit in thrust and will continue to be used on the Twin engine aircraft smaller than the 777.
 
David L
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RE: 757 RR Engine On Wing Time

Wed Oct 25, 2006 7:57 pm

Quoting Jben (Reply 15):



Quoting JetMech (Reply 16):



Quoting TheJoe (Reply 17):

Thank you for providing some objective information and refuting the claims from earlier threads that RR engines are heavier and generally unreliable. Clearly, the bottom line is that airlines would not continue to buy a product that's as bad as "someone" would have us believe.
 
Rj111
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RE: 757 RR Engine On Wing Time

Wed Oct 25, 2006 8:07 pm

Quoting JetMech (Reply 12):
I always thought that one of the main reasons for a 3 spool design was fuel efficiency, but it seems that RR generally suffers from a very slight fuel consumption disadvantage when compared to an equivalent GE.

From what i've gathered fuel burn disparities are the following...

The Trent 800 is the most effcient 777 engine below 3000nm-4000nm, after this the Ge90 takes over.

The RB211-535 is less efficient than PW4020 on the 757 but far more reliable/durable an ultimately more cost effective.

The RB211-524 is approxiamtely 3% and 5% less efficient on the 744 and 767 respectively than the GE and PW.

The IAE V25000 is slightly more efficient than the CFM-56

As for maintenance costs, someone else will have to enlighten us.

I think the three spool design's real advantage is it's thrust versatility more than necesarily sheer size. The Rb211/Trent is economical (not necessarly the most economical but competitive) from 40,000lb and has demonstrated up to 114,000lb with the Trent 8104 - nearly 3 times the lowest setting. The GE90 is a bulkier engine - a typical GE 772ER will weigh approximately 3t more than an RR or PW one, but it is the most efficient. This is demonstrated by it's good performance at longer ranges, and explains why there are no GE 772As. So although it's a two spool design, it's essentially a scaled up one and performs very well at the top thrusts - i doubt there is a limit to upscaling a two spool design further with a bigger platform than the Ge90. But GE have needed the CF6-80 and the GE90 to cover essentially what RR could do with one engine platform, not bad going for RR.
 
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jetmech
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RE: 757 RR Engine On Wing Time

Wed Oct 25, 2006 10:25 pm

Quoting TheJoe (Reply 17):
Now, a 7,500lb weight saving per engine translates into useful payload for the operator of the aircraft. Which means more revenue per passenger mile flown doesn't it?

Is the 7500lb weight saving for two engines or one? A total saving of 7500lb is impressive enough, but if it is double this at 15000lb, all I can say is wow!

Quoting RJ111 (Reply 19):
The RB211-524 is approximately 3% and 5% less efficient on the 744 and 767 respectively than the GE and PW.

I don't know why, be whenever I heard of the slight fuel consumption disadvantage of RR on the 744, I always imagined it to be about 6-7%. I guess giving away 3% is not too bad but definitely noticeable.
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
TheJoe
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RE: 757 RR Engine On Wing Time

Thu Oct 26, 2006 12:28 am

Quoting TheJoe (Reply 17):
Now, a 7,500lb weight saving per engine translates into useful payload for the operator of the aircraft. Which means more revenue per passenger mile flown doesn't it?



Quoting JetMech (Reply 20):
Is the 7500lb weight saving for two engines or one? A total saving of 7500lb is impressive enough, but if it is double this at 15000lb, all I can say is wow!

My mistake! Sorry about that... I meant to write "per aeroplane" not "per engine"! Here are the weight specs as quoted from the manufacturer:

RB211 Trent - Dry weight: 13,500lb

GE90-90b - Dry weight: 16,664lb

Now this works out to only 6,328lb saving, but Rolls Royce made the comment that "The Trent has a 3.6 tonne (8,000 lb) installed weight advantage over the GE90, leading to the best payload/range performance on the 777"

How they came to that conclusion, I do not know...

Thanks for picking up on that though JetMech!
 
BOE773
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RE: 757 RR Engine On Wing Time

Thu Oct 26, 2006 1:59 am

Quoting RJ111 (Reply 19):
i doubt there is a limit to upscaling a two spool design further with a bigger platform than the Ge90.

I remember reading somewhere that GE claims that the -90 core has growth potential out to 150,000 lb.t.

(We need more GE/Pratt people on this forum as it mostly seems to be RR people!!)
 
Lemurs
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RE: 757 RR Engine On Wing Time

Thu Oct 26, 2006 2:06 am

Quoting BOE773 (Reply 22):
We need more GE/Pratt people on this forum as it mostly seems to be RR people!!)

There are actually a fair number of Pratt folks who post here, who have even commented on threads that you have started/commented-on/tried-to-hijak. I'm not as certain about GE folks, but I think it's fair to say there has to be at least a couple who read/post/lurk. You don't notice them because they are professionals and in some cases, engineers. They are not going to go around embarassing themselves by claiming that a competitor's engine is inferior in all fashions to the ones made by their company. Why would it be embarassing to them? Because there is a preponderance of evidence out there that it's simply not true.

So if you were hoping for some help in bashing RR, you're not going to find it among professionals who really know what they are talking about.

Edit: I note with a serious belly-laugh of irony that you posted this throw-away comment about there needing to be more GE/Pratt people in this forum in THIS THREAD of all threads. I could not have written the comedy in that any better. Bravo.

[Edited 2006-10-25 19:08:43]
There are 10 kinds of people in the world; those who understand binary, and those that don't.
 
Tristarsteve
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RE: 757 RR Engine On Wing Time

Thu Oct 26, 2006 2:12 am

Quoting BOE773 (Reply 22):
We need more GE/Pratt people on this forum as it mostly seems to be RR people!!)

Trouble is that most technicians that have worked on all three types of engine (like me) can only praise the RR design. We don't care that it might use a little more fuel, it is the shear ease of working on it that makes the difference. On a RB211/Trent, you open the fan cowls and have access to 99% of the components you work on on the ramp. On the RB211 you can do this single handed with a screwdriver. On the Trent you can open them yourself, but need help to close them. On the Pratt/GE you have to open the C ducts to reach anything. Anyone that worked on the original JT9 remembers with horror the complete lack of access to the core engine. There were air ducts everywhere! I was lucky, most of my hangar work was on the RB211-524. Just open the fan ducts, pull up a chair, and get on with it.
 
MarkC
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RE: 757 RR Engine On Wing Time

Thu Oct 26, 2006 7:28 am

Does anyone know why the RR is light? Does it have a lower blade count because the spools run at more optimum speeds? I would think, that with the extra bearing, and associated bearing support, it would be heavier.

Does anyone have a cross section of a 211? And I don't mean one of those marketing cartoons. I never knew the RR had only 1 VSV stage. PW2000's have 5.

Steve, I know what you mean. Its difficult to see the core on a 9D even if its a bare engine on a ground stand.

Lemurs, maybe some users are really moderator run just to lighten up the forum.
 
onetogo
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RE: 757 RR Engine On Wing Time

Thu Oct 26, 2006 8:06 am

Quoting MarkC (Reply 25):
I never knew the RR had only 1 VSV stage. PW2000's have 5.

Please elaborate.
 
jben
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RE: 757 RR Engine On Wing Time

Thu Oct 26, 2006 8:40 am

Sorry for the confusion, I said "a 777 powered by Rolls Royce Trents is 7,500lbs lighter", I meant the entire airplane (both engines).

The weight I have for the Trent 800 is 13,100lbs, with the GE70-76 being 16,664lbs. That is 7,128lbs lighter in total (with two engines). The 7,500lbs-8,000lbs figure probably includes savings in other areas... As for the lower weight, alot of it comes from the three spool design (and the differnet IPC/IP needs).

As for the cutout, you might like this one: http://www.vc10.net/History/Individual/Images/rb211cutaway.gif Although if you use google images, you can find some other good ones too.
 
MarkC
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RE: 757 RR Engine On Wing Time

Thu Oct 26, 2006 9:53 am

Onetogo:

VSV is Variable Stator Vane. The first stages of the HPC have vanes which are moveable depending on operating conditions. Essentially, it lowers or raises the compression ratio. Its kind of a band aid for engine performance.

That RR has only one shows that it is a more optimised design. There are always trade-offs in everything.
 
onetogo
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RE: 757 RR Engine On Wing Time

Thu Oct 26, 2006 11:54 am

Quoting MarkC (Reply 28):

VSV is Variable Stator Vane. The first stages of the HPC have vanes which are moveable depending on operating conditions. Essentially, it lowers or raises the compression ratio. Its kind of a band aid for engine performance.

Thanks so much for the clarification. I'm aware of the stator vanes in the two (or 3 for RR) compressor stages, but have never heard of any sort of variable vane. I assume this just adjusts the stator vane blade angle? Do you have any link(s) to additional information on how exactly this system works? Thanks in advance.
 
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LTU932
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RE: 757 RR Engine On Wing Time

Thu Oct 26, 2006 3:31 pm

Quoting Jben (Reply 27):
As for the cutout, you might like this one: http://www.vc10.net/History/Individual/Images/rb211cutaway.gif

I've been looking at the cutout, and I noticed reverser buckets at the rear of the engine, along with what looks to be the filter (don't know if this is the right term) for a cascade reverser. Was the RB211 originally designed for a clamshell reverser or just for a cascade reverser?
 
tepidhalibut
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RE: 757 RR Engine On Wing Time

Thu Oct 26, 2006 5:02 pm

Quoting LTU932 (Reply 31):
Was the RB211 originally designed for a clamshell reverser or just for a cascade reverser?

Oh Boy, that's an old pic.

To me it looks like the original design of RB211-22. The Hot-Stream revereser didn't last long in service, and was deleted by mod in 1974/75 to save weight / improve performance. All RB211 engines since then have only had a cold-stream (bypass air) reverser. Usually this is of the cascade-syle, but some (Trent 700 IIRC) have a clam-shell-style. The hot-stream reverser was only used on the 22/22B/22C.
 
Tristarsteve
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RE: 757 RR Engine On Wing Time

Thu Oct 26, 2006 5:41 pm

Quoting MarkC (Reply 28):
VSV is Variable Stator Vane. The first stages of the HPC have vanes which are moveable depending on operating conditions. Essentially, it lowers or raises the compression ratio. Its kind of a band aid for engine performance.

That RR has only one shows that it is a more optimised design. There are always trade-offs in everything.

On RB211 there is a single stage of VIGV. (Variable inlet guide vanes.) They are fully closed at start and are fully open at take off. They are controlled by a VIGV controller which even in the RB211-524H is a 'air computor'. It used various air pressures and has passages in it that choke and restrict the air and it controls the VIGVs. No electrics are involved. Works very well, but needs cleaning regularly. This VIGV is at the IP compressor input. There are no IGV in the HP compressor. If you look down the front of an RB211 you can see them behind the fan blades. There are also 3 or 4 Surge bleed valves. These are either open or closed. They are open at start and most of them are closed by idle power. The last one closes a little later. They are to control the surge margin in the compressor to avoid stalls/surges.
The CFM56 has a ring of VBVs (variable bleed valves) as well. They are arranged around the compressor and do the same job but close slowly in relation to compressor speed.
In Pratt and GE engines there are VIGVs and IGVs, rows of them all along the LP compressor. They do the same job, but there is just more complexity and weight. In service they all work well and cause little trouble.
 
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jetmech
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RE: 757 RR Engine On Wing Time

Thu Oct 26, 2006 6:11 pm

Quoting TristarSteve (Reply 33):
It used various air pressures and has passages in it that choke and restrict the air and it controls the VIGVs.

What do the VIGV actuators use as their working fluid? For some reason I seem to remember that they used pressurised fuel  .

[Edited 2006-10-26 11:37:08]
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
TheJoe
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RE: 757 RR Engine On Wing Time

Thu Oct 26, 2006 6:19 pm

Quoting JetMech (Reply 34):
What do the VIGV actuators use as their working fluid? For some reason I seem to remember then using pressurised fuel

You beat me to it! I was just about to ask the same question... I know that is the case on the CFM56 because we have to disconnect some lines and plug in a special little fuel rig to pump open the VSV's for a boroscope inspections... Can anyone tell me if it is similar on an RB211? How about a CF6? I've never done anything that serious on those engines, just routine maintenance.

Thanks!
 
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jetmech
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RE: 757 RR Engine On Wing Time

Thu Oct 26, 2006 6:41 pm

Quoting TheJoe (Reply 35):
I know that is the case on the CFM56 because we have to disconnect some lines and plug in a special little fuel rig to pump open the VSV's for a boroscope inspections

I do remember using such a rig TheJoe, and it was either on the GE or P&W. For the RB211, we had special tools that fitted around the back of the actuator body and onto a bolt that went thru the piston rod. You could use these tools to manually move the VIGVA's back and forth. IIRC, you were meant to have two people simultaneously moving both actuators in unison.
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
TheJoe
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RE: 757 RR Engine On Wing Time

Thu Oct 26, 2006 7:03 pm

So fuel is the operating medium for the VIGV on the RB211? If so, do they take it from something like the MEC on the CFM56?

Quoting JetMech (Reply 36):
For the RB211, we had special tools that fitted around the back of the actuator body and onto a bolt that went thru the piston rod.

Well, that would probably make life a little easier. Saves you from disconnecting lines and getting covered in fuel! Not that I mind the smell...  Silly
 
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jetmech
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RE: 757 RR Engine On Wing Time

Thu Oct 26, 2006 7:12 pm

Quoting TheJoe (Reply 37):
So fuel is the operating medium for the VIGV on the RB211?

For some reason I seem to think so but I am not 100% sure.

Quoting TheJoe (Reply 37):
Saves you from disconnecting lines and getting covered in fuel! Not that I mind the smell...

"Eau de Kero", the new fragrance for AME's / A&P's
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
TheJoe
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RE: 757 RR Engine On Wing Time

Thu Oct 26, 2006 7:37 pm

Quoting JetMech (Reply 38):
"Eau de Kero", the new fragrance for AME's / A&P's

lol Yeah, that's the good one! "Eau de Skydrol" is the one I really don't like!  melting 

If anyone has some more information on the RB211 VIGV system or a link to a site, I would appreciate it. Thanks!
 
Tristarsteve
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RE: 757 RR Engine On Wing Time

Thu Oct 26, 2006 8:12 pm

Quoting JetMech (Reply 34):
What do the VIGV actuators use as their working fluid?

RB211 uses air pressure to operate the VIGVs through two actuators.
The whole VIGV and Start bleed valve system is controlled and operated by bleed air.
The RB211-524H has a full electronic fuel controller. It is not a FADEC because the air powered VIGV controller is still there doing its stuff.
 
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jetmech
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RE: 757 RR Engine On Wing Time

Thu Oct 26, 2006 9:48 pm

Quoting TristarSteve (Reply 40):
RB211 uses air pressure to operate the VIGVs through two actuators.

No worries TristarSteve. That is probably why you can use those tools to manipulate the VIGVA's, as there is no hydraulic lock to contend with.
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
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LTU932
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RE: 757 RR Engine On Wing Time

Fri Oct 27, 2006 4:54 am

Quoting TepidHalibut (Reply 31):
but some (Trent 700 IIRC) have a clam-shell-style.

Clamshell type? I thought the petal reversers in general (like on the CFM56 and Trent 700) were the same cascade reversers, just with the reversers open differently (opening as a petal and not with the rear cowling sliding to the back).
 
Molykote
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RE: 757 RR Engine On Wing Time

Fri Oct 27, 2006 7:27 am

Quoting LTU932 (Reply 41):
Clamshell type? I thought the petal reversers in general (like on the CFM56 and Trent 700) were the same cascade reversers, just with the reversers open differently (opening as a petal and not with the rear cowling sliding to the back).

The difference would be that when the "petals" open it is the petals themselves that turn the airflow. No reverser cascades exist beneath the petal doors.
Speedtape - The aspirin of aviation!
 
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LTU932
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RE: 757 RR Engine On Wing Time

Fri Oct 27, 2006 7:53 am

Quoting Molykote (Reply 42):
The difference would be that when the "petals" open it is the petals themselves that turn the airflow. No reverser cascades exist beneath the petal doors.

I see now. Thanks for explaining.
 
BA777ER236
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RE: 757 RR Engine On Wing Time

Sat Oct 28, 2006 7:31 am

Quoting David L (Reply 18):
Thank you for providing some objective information and refuting the claims from earlier threads that RR engines are heavier and generally unreliable.

I concur David.

Quoting RJ111 (Reply 19):
and explains why there are no GE 772As

Actually not true, BA operate 3 772As with GE90-76Bs (G-ZZZA,ZB,ZC) and did, at one time, operate ZD and ZE(these were most recently at VARIG).

The BA 772ERs are powered by RR Trent 895s, and the 772Bs are GE90-85Bs. The ERs are approx. 2 Tons (2,000kg) lighter on APS weights with similar cabin seating, but the ERs also have an overhead bunk unit for cabin crew, and a small 2 bunk unit at the rear of First class for flight crew.

Operationally, it is interesting to fly both, though not a problem. A colleague of mine once said that 'the GEs feel like two huge hoovers sucking you along, and the Roller just has lots of 'grunt''. The Roller does burn slightly more fuel, but because of the lower engine weight, for the same payload it is very close.

Quoting RJ111 (Reply 19):
The Trent 800 is the most effcient 777 engine below 3000nm-4000nm, after this the Ge90 takes over.

I think this is probably about right.

Anecdotally, I have heard LHR engineers observe that they open the cowlings on the GE90 far more often than on the RR, and in fact that opening them at all on the Roller is a rare event. I also know that from the oil replenishment perspective, it is common to uplift 2-3 quarts of oil per engine on the GE after a 7 hour flight, but uplift of oil on the Roller is very low per turnround.

The Trent is a little more difficult to handle on the ground whilst taxiing, because it is less responsive to low angle thrust lever movement, but if you move them forward more than 0.75 inches, a lot of thrust comes all at once!

I do not have any data on on wing time, but I know that both types are extremely reliable, and I have absolutely no qualms about flying both.  Smile

I think I've gone a bit 'off topic', but I hope it's interesting!
Flying would be easy if it wasn't for the ground
 
BOE773
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RE: 757 RR Engine On Wing Time

Sat Oct 28, 2006 7:54 am

Quoting BA777ER236 (Reply 44):
A colleague of mine once said that 'the GEs feel like two huge hoovers sucking you along

Interesting and thank you for your post, BA777ER236.
"Hoovers" Smile Most of us colonials out roaming the prairies with the buffalo won't have a 'baldy', a clue, what a hoover is, but I'll let them know.........a hoover in jolly ole England is a vacuum cleaner! So there.
 
BA777ER236
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RE: 757 RR Engine On Wing Time

Sat Oct 28, 2006 7:58 am

Quoting BOE773 (Reply 45):
Most of us colonials out roaming the prairies with the buffalo won't have a 'baldy', a clue, what a hoover is, but I'll let them know..

I always thought that 'Hoovers' were a North American invention!!
Flying would be easy if it wasn't for the ground
 
David L
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RE: 757 RR Engine On Wing Time

Sat Oct 28, 2006 8:14 am

Quoting BA777ER236 (Reply 46):
Quoting BOE773 (Reply 45):
Most of us colonials out roaming the prairies with the buffalo won't have a 'baldy', a clue, what a hoover is, but I'll let them know..

I always thought that 'Hoovers' were a North American invention!!

I think the company's always been American owned, too.
 
Rj111
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RE: 757 RR Engine On Wing Time

Sun Oct 29, 2006 3:13 am

Quoting BA777ER236 (Reply 44):
Actually not true, BA operate 3 772As with GE90-76Bs (G-ZZZA,ZB,ZC) and did, at one time, operate ZD and ZE(these were most recently at VARIG).

You're right. I was getting confused with the -300A, of which there are no GE examples.

Quoting BA777ER236 (Reply 44):
I think this is probably about right.

When BA decides which 777 goes where do they take this into account, or is that too hard to plan for?
 
Tristarsteve
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RE: 757 RR Engine On Wing Time

Sun Oct 29, 2006 4:04 am

Quoting BA777ER236 (Reply 44):
but uplift of oil on the Roller is very low per turnround.

Yes, it has amazingly low consumption.
If the guy in KUL fills it up, they will operate KUL-ARN-EWR-ARN and then need about one litre in each engine. Thats 28hrs flying for a litre, and sometimes they need nothing at all.
We find the V2500 the same. Can go days without a refill, while our CFM56-5 will need 2 litres a day.

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