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JoeCanuck
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 12:14 am

ikolkyo wrote:
Stitch wrote:
SteelChair wrote:
CFM? I would rather think the entry would come from GE.


As the links Revelation included note, NMA's engine will likely be based on the CFM LEAP. In addition, I would expect it to become the basis for whatever engine powers NSA (the 737 replacement) as CFM will assuredly be at least one, if not the sole, source for powering that family.


I expect NSA would be powered by a GTF engine from CFM. I doubt LEAP would still be used as a basis a decade from now.


:checkmark: I think you are correct. In my opinion, the next generation of civilian jet engines will all have geared fans. More efficiency out of the low pressure spool with fewer parts, and efficiency is the driving force right now. Sure, Pratt is having grief with their engine, but the gearbox doesn't seem like one of the problems.
What the...?
 
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RayChuang
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 1:16 am

I think Boeing is looking at GE Aviation providing a scaled up LEAP engine (in cooperation with Safran) or a scaled-down GENx engine. More likely a scaled-up LEAP engine with a larger front fan, rated between 38,000 and 43,000 lb. of thrust, the same range as the PW2000 series engines.
 
jagraham
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 2:12 am

QuarkFly wrote:
jagraham wrote:
Boeing has already said the wing will be indistinguishable from a 787 on the flightline. I would expect a skinnier, high aspect ratio wing (to get an advantage similar to what the 77X has over the 77W), but the wing will be approximately 787 width.


The 787 MTOW is up to 250 tons, a 797 would be about half that. Although the 797 wing may look like a proportionally smaller 787 wing... I doubt the span and wing area would be anything near the 787 wing dimensions because it would make the 797 way too heavy.

I suspect the 797 span would be no more than about 767-sized, 50 meter, maybe a bit more (about 170 feet), ...ideally to fit into smaller gates than the 787 without wingtip folding. The total wing area may be smaller than the 767 to obtain the higher aspect ratio -- which is OK because I'm sure a 797 will be much lighter than a 767.


First, the beauty of carbon fibre is that the weight vs span metrics change for the better. Carbon fibre can be laid up to carry the load in a way that aluminum can't.

Second, the long skinny wing is the best way to reduce thrust while achieving the other goals. As was done with the 77X - same weight as the 77W, same runways, 10% less thrust. Boeing will not pass that up. Because of this, and the gate issues, I am still looking for folding wingtips. We shall see.

If Boeing was going to limit itself to 767 wingspan, there would be no reason to not save money and resurrect the 767-300A (which does TATL with 48000 lb thrust GE CF6-80A engines and 16000 lbs of fuel) put on the best winglets, and re-engine it. That could be done in a year or two. So I hope Boeing is aiming higher - much higher - if they are going to go through a whole new aircraft development cycle.
 
QXAS
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 2:38 am

keesje wrote:
Revelation wrote:
PlanesNTrains wrote:
Just curious why? Not trying to argue, just wondering?

And while we're asking, why aren't we predicting doom for the C Series in Asia because its 5-wide no-container fuse dis-favors cargo?

Maybe it's not all about cargo after all?


Newbiepilot wrote:
I guess i shouldnt be surprised to see the same cabin width discussions come up in a thread about engine selection. I am really introgued by the debate over single or dual source for engines. The implications are huge! Airlines want the aquisition price from single source but the maintenance and power by the hour rates offered by dual source. This truly is a pivotal decision impacting the business case for going ahead and launching the plane.

PlanesNTrains wrote:


Just curious why? Not trying to argue, just wondering?


Seems like a strange comment from Keesje. LCCs want faster turn times and easier aisle access for the carts to sell products inflight. LCCs also tend not to carry as much cargo. Some carry none. They likely do want twin aisle options that have aquisition prices in the same vicinity as current narrowbodies



So far I find the substantiation behind the efficiencies of 2-3-2 vs 3-3 for ~ 260 seats single class a bit dissapointing. It's often evasive movements (prove it ain't so) & Boeing says so. But I keep hoping we will see some more factual input here to next the impressive, valuable commenting on others.

Keesje, you’re kicking a dead horse here. Boeing has done their math. We’ll find out how it works in practicallity. But if Boeing doing their homework and creating a great product for the airlines and passengers is a problem for you, that’s not something we should have to deal with. On A.net we’ve discussed it to death. Customer response looks positive. This thread is about ENGINE CHOICES, not fuselage width. Either start your own thread where we can rehash this again, or read an old thread. We’ve been over all of this in the past. Finally, frontal area is not where all of your drag comes from. Efficient wings and skin technology can easily make up for the larger frontal area.
I am NOT an employee of any airline or manufacturer. I speak for myself, not on the behalf of any company.
 
AA737-823
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 3:26 am

jagraham wrote:
First, the beauty of carbon fibre is that the weight vs span metrics change for the better. Carbon fibre can be laid up to carry the load in a way that aluminum can't.

Second, the long skinny wing is the best way to reduce thrust while achieving the other goals. As was done with the 77X - same weight as the 77W, same runways, 10% less thrust. Boeing will not pass that up. Because of this, and the gate issues, I am still looking for folding wingtips. We shall see.


While your points for folding wingtips certainly make sense, I can't help but think that the folding wingtip apparatus would add far too much cost, and maybe weight, to this particular airframe program.
Particularly when Delta- rumored to be the keenest customer- has already said 'KEEP IT CHEAP, or we won't buy.'
 
JoeCanuck
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 4:45 am

AA737-823 wrote:
jagraham wrote:
First, the beauty of carbon fibre is that the weight vs span metrics change for the better. Carbon fibre can be laid up to carry the load in a way that aluminum can't.

Second, the long skinny wing is the best way to reduce thrust while achieving the other goals. As was done with the 77X - same weight as the 77W, same runways, 10% less thrust. Boeing will not pass that up. Because of this, and the gate issues, I am still looking for folding wingtips. We shall see.


While your points for folding wingtips certainly make sense, I can't help but think that the folding wingtip apparatus would add far too much cost, and maybe weight, to this particular airframe program.
Particularly when Delta- rumored to be the keenest customer- has already said 'KEEP IT CHEAP, or we won't buy.'


On the other hand...they also want it efficient. They might save a lot more over the lifetime of the aircraft than whatever the difference in purchase price might be between a normal and a folding wing. Now that they've managed sell one folding wing...they might be inclined to try it again.
What the...?
 
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monomojo
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 5:07 am

JoeCanuck wrote:
AA737-823 wrote:
jagraham wrote:
First, the beauty of carbon fibre is that the weight vs span metrics change for the better. Carbon fibre can be laid up to carry the load in a way that aluminum can't.

Second, the long skinny wing is the best way to reduce thrust while achieving the other goals. As was done with the 77X - same weight as the 77W, same runways, 10% less thrust. Boeing will not pass that up. Because of this, and the gate issues, I am still looking for folding wingtips. We shall see.


While your points for folding wingtips certainly make sense, I can't help but think that the folding wingtip apparatus would add far too much cost, and maybe weight, to this particular airframe program.
Particularly when Delta- rumored to be the keenest customer- has already said 'KEEP IT CHEAP, or we won't buy.'


On the other hand...they also want it efficient. They might save a lot more over the lifetime of the aircraft than whatever the difference in purchase price might be between a normal and a folding wing. Now that they've managed sell one folding wing...they might be inclined to try it again.


Depends entirely on how much value the customers would put on being able to use the next smallest gates. If we assume the 797 to be about the same MTOW of the 757, then it would probably have about the same or a bit more wingspan, 125-130 feet. The Code C box is 118 feet, which is what the 737 and A320 use. So that would be a trade of 6-10 foot folding wingtips for being able to use existing 737/A320 only gates. Are there that many 737/A320 only gates to be worth it?
 
jagraham
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 5:24 am

monomojo wrote:
JoeCanuck wrote:
AA737-823 wrote:

While your points for folding wingtips certainly make sense, I can't help but think that the folding wingtip apparatus would add far too much cost, and maybe weight, to this particular airframe program.
Particularly when Delta- rumored to be the keenest customer- has already said 'KEEP IT CHEAP, or we won't buy.'


On the other hand...they also want it efficient. They might save a lot more over the lifetime of the aircraft than whatever the difference in purchase price might be between a normal and a folding wing. Now that they've managed sell one folding wing...they might be inclined to try it again.


Depends entirely on how much value the customers would put on being able to use the next smallest gates. If we assume the 797 to be about the same MTOW of the 757, then it would probably have about the same or a bit more wingspan, 125-130 feet. The Code C box is 118 feet, which is what the 737 and A320 use. So that would be a trade of 6-10 foot folding wingtips for being able to use existing 737/A320 only gates. Are there that many 737/A320 only gates to be worth it?


A very good question. But if Southwest's rumored interest is true, that would change the equation quite a bit.
 
parapente
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 5:35 am

The new wing will need to be .
1.As laminar as possible
2.As light as possible
3.As cheap as possible
4.Fully operational to a v tight development schedule.
5.Robust for heavy cycles.

There are I believe plenty of C gates available particularly in the critical N American continent.

Can't see them messing about with (unproven) folding wings on this project myself.But no doubt find out soon enough.
 
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monomojo
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 5:55 am

Not to over simplify it, but a wingtip is a wingtip. If Boeing can make a 12 foot folding wingtip work reliably and economically on the 777X, then they can probably make a 8 or 10 foot folding wingtip work reliably and economically on the 797. So it just comes back to whether the customers find value in the capability it provides.
 
JustSomeDood
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 6:09 am

monomojo wrote:
JoeCanuck wrote:
AA737-823 wrote:

While your points for folding wingtips certainly make sense, I can't help but think that the folding wingtip apparatus would add far too much cost, and maybe weight, to this particular airframe program.
Particularly when Delta- rumored to be the keenest customer- has already said 'KEEP IT CHEAP, or we won't buy.'


On the other hand...they also want it efficient. They might save a lot more over the lifetime of the aircraft than whatever the difference in purchase price might be between a normal and a folding wing. Now that they've managed sell one folding wing...they might be inclined to try it again.


Depends entirely on how much value the customers would put on being able to use the next smallest gates. If we assume the 797 to be about the same MTOW of the 757, then it would probably have about the same or a bit more wingspan, 125-130 feet. The Code C box is 118 feet, which is what the 737 and A320 use. So that would be a trade of 6-10 foot folding wingtips for being able to use existing 737/A320 only gates. Are there that many 737/A320 only gates to be worth it?


The 757 has a very low aspect ratio wing compared to newer planes though. A higher aspect ratio wing will necessitate more span even with lower wing area. Besides, 45k engines would not be necessary for a MOM plane with the 757's MTOW. Given that it wouldn't have the short field constraints of the former and more lift from a better designed wing.
 
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qf789
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 7:16 am

Please keep the thread on topic, as the title suggests the discussion in about engines so keep your comments on topic, if the thread continues to go off topic the thread will be locked
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keesje
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 9:38 am

Stitch wrote:
keesje wrote:
So far I find the substantiation behind the efficiencies of 2-3-2 vs 3-3 for ~ 260 seats single class a bit disappointing.


Well we'd pretty much need to model them via computer since most 767-200 and 757-300 operators did not fly the type in a single class. And that is what I expect Boeing and the airlines have done.

The 757-300, which could seat 275 or 295 in a single class sold 55 units. The 767-200 sold 128 and the 767-200ER added another 121 on top of that (both could seat 290 in a single class).


The 762 is from the early eighties, the 753 from the late nineties. Boeing saw the 753 as 762 replacement. Extra range, 73NG cockpit and other more radical upgrades fell of the table because of risk reduction. Then came 9-11 and US carriers cancelled everything and Boeing the 75.

In terms of engines the 75 faced the same dilemma as an NMA now. Lighter version of WB engines were specified, not helping weight & costs. Airbus faced the same with the A340s.

Maybe PW's position isn't so bad. Things have changed since 10-20 years ago. UTC is almost as big as Boeing and they have the game changing technology in production. And GE is no longer GE.
Last edited by keesje on Sat Jun 30, 2018 10:01 am, edited 1 time in total.
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parapente
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 9:52 am

Engines.To gear or not to gear,that is the question for GE .I would imagine that by now they have 100% clarity on the sfc between the two engines on Airbus A320 - or A321NEO if one wanted the closest thrust AFC comparison to what would be the mom engine thrust.

If there was a marked difference then you would see it on the range tables of the A320/321 NEO but as best I know you don't ( much) if any.
It is said that the GTF is more fuel efficient,but it must show up in the existing real world figures as to exactly what extent.No?

Personally I would have thought that creating a brand new ( for the first time ever) GTF for mature EIS in 7 years is one hell of a risk.Its not simply a question of a gearbox,all the rotational speeds -and therefore blade designs change as a result.Depending on the answer to the above fact it may not be necessary at all anyway.
 
fsabo
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 10:53 am

parapente wrote:
Engines.To gear or not to gear,that is the question for GE .I would imagine that by now they have 100% clarity on the sfc between the two engines on Airbus A320 - or A321NEO if one wanted the closest thrust AFC comparison to what would be the mom engine thrust.

If there was a marked difference then you would see it on the range tables of the A320/321 NEO but as best I know you don't ( much) if any.
It is said that the GTF is more fuel efficient,but it must show up in the existing real world figures as to exactly what extent.No?

Personally I would have thought that creating a brand new ( for the first time ever) GTF for mature EIS in 7 years is one hell of a risk.Its not simply a question of a gearbox,all the rotational speeds -and therefore blade designs change as a result.Depending on the answer to the above fact it may not be necessary at all anyway.


The PW GTF at this point in time is a little better than the LEAP fuel burn wise. The GTF will get a 3% pip. I doubt the LEAP will get much better than it is now. PW messed up on reliability, their engine has been buggy. The LEAP is reliable, but its durability is lower than expected. In the long run the GTF may prove to be the better and more efficient engine.

The variable pitch GTF from RR should be very interesting. However, RR has the T1000 screwup. Boeing probably percievs GE as the lowest risk option. GE just happens not to use a gearbox. I think is a reputation thing, not a gearbox vs direct drive thing.
 
mffoda
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 2:27 pm

harder than woodpecker lips...
 
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lightsaber
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 2:29 pm

jagraham wrote:

First, the beauty of carbon fibre is that the weight vs span metrics change for the better. Carbon fibre can be laid up to carry the load in a way that aluminum can't.

Second, the long skinny wing is the best way to reduce thrust while achieving the other goals. As was done with the 77X - same weight as the 77W, same runways, 10% less thrust. Boeing will not pass that up. Because of this, and the gate issues, I am still looking for folding wingtips. We shall see.

I'm unable to come up with a 797 business case without folding wingtips. Longer aspect ratio is required for underside laminar flow.

The weight savings allow flying at higher altitudes (lower density air) and that saves fuel (assuming lower wing loading).


We are looking at an excellent 762/763 replacement for the bulk of the missions.

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lightsaber
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 2:37 pm

fsabo wrote:
parapente wrote:
Engines.To gear or not to gear,that is the question for GE .I would imagine that by now they have 100% clarity on the sfc between the two engines on Airbus A320 - or A321NEO if one wanted the closest thrust AFC comparison to what would be the mom engine thrust.

If there was a marked difference then you would see it on the range tables of the A320/321 NEO but as best I know you don't ( much) if any.
It is said that the GTF is more fuel efficient,but it must show up in the existing real world figures as to exactly what extent.No?

Personally I would have thought that creating a brand new ( for the first time ever) GTF for mature EIS in 7 years is one hell of a risk.Its not simply a question of a gearbox,all the rotational speeds -and therefore blade designs change as a result.Depending on the answer to the above fact it may not be necessary at all anyway.


The PW GTF at this point in time is a little better than the LEAP fuel burn wise. The GTF will get a 3% pip. I doubt the LEAP will get much better than it is now. PW messed up on reliability, their engine has been buggy. The LEAP is reliable, but its durability is lower than expected. In the long run the GTF may prove to be the better and more efficient engine.

The variable pitch GTF from RR should be very interesting. However, RR has the T1000 screwup. Boeing probably percievs GE as the lowest risk option. GE just happens not to use a gearbox. I think is a reputation thing, not a gearbox vs direct drive thing.

The LEAP is due to get a CMC PIP. Recall the GE9x is the launch platform.
Pratt has, eventually, promised a CMC PIP for the PW1100G.

As much as I'm a Pratt fan, this competition isn't a sprint, it will be a long Marathon.

Lightsaber
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Newbiepilot
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 2:46 pm

mffoda wrote:



I expect that the ability for PW to solve the multiple issues around the GTF, CFM to solve the LeapX seal issues, and RollsRoyce to solve the Trent 1000/7000 blade cracking is being watched when deciding who will build engines for the 797. In service issues will always come up, but the ability to solve problems with minimal disruption and cost to the airlines is how engine manufacturers differentiate themselves.
 
frmrCapCadet
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 2:57 pm

monomojo wrote:
JoeCanuck wrote:
AA737-823 wrote:

While your points for folding wingtips certainly make sense, I can't help but think that the folding wingtip apparatus would add far too much cost, and maybe weight, to this particular airframe program.
Particularly when Delta- rumored to be the keenest customer- has already said 'KEEP IT CHEAP, or we won't buy.'


On the other hand...they also want it efficient. They might save a lot more over the lifetime of the aircraft than whatever the difference in purchase price might be between a normal and a folding wing. Now that they've managed sell one folding wing...they might be inclined to try it again.


Depends entirely on how much value the customers would put on being able to use the next smallest gates. If we assume the 797 to be about the same MTOW of the 757, then it would probably have about the same or a bit more wingspan, 125-130 feet. The Code C box is 118 feet, which is what the 737 and A320 use. So that would be a trade of 6-10 foot folding wingtips for being able to use existing 737/A320 only gates. Are there that many 737/A320 only gates to be worth it?


I would guess that 737/320 gates are the most numerous gates in the entire world. And airport real estate is amongst the most expensive in the world.
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andrewfarmer
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 3:07 pm

Can someone help me understand why Boeing is launching the NMA program when for years they have said no to a 757 replacement? Though I am admittedly lacking in aviation acumen, it appears to me that such a new program would stretch them very thin, with the 73, 77, and 78 though mature still requiring investment to maintain market position. How big of a market will the NMA reach? Instead of investing resources there, why wouldn't Boeing do a clean sheet modern redesign of the 737 which, with new tech, could possibly even fulfill range and load requirements of the rather narrow band that the NMA seeks to hit.

How many years will the 73M program carry the line into the future before it will no longer be competitive with what a modern redesign could offer? From my again not very informed opinion, I would think B would want to think about how to maintain hold of the 737 market in the next 50 years.
 
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Revelation
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 4:14 pm

fsabo wrote:
The PW GTF at this point in time is a little better than the LEAP fuel burn wise. The GTF will get a 3% pip.

Maybe we should be leery of PIPs. Trent's problems came in via Package C. PW's #3 bearing seal fail was an attempt to improve durability that went very wrong. Where I used to work some of our biggest screw ups happened during these kinds of "one off" sets of changes, especially when technology was migrated from one platform to another without sufficient understanding or testing of the change due to the presumption that if it worked on one platform it'll work fine on all. Picking up 3% in one go feels aggressive.
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Stitch
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 4:24 pm

andrewfarmer wrote:
Can someone help me understand why Boeing is launching the NMA program when for years they have said no to a 757 replacement?


The NMA is a 767 replacement. The 737-10 and A321-200neo already have the 757 replacement market covered.



andrewfarmer wrote:
Instead of investing resources there, why wouldn't Boeing do a clean sheet modern redesign of the 737 which, with new tech, could possibly even fulfill range and load requirements of the rather narrow band that the NMA seeks to hit.


Boeing has been working on the 737 replacement - NSA - for close to a decade. If the 787 program had not imploded between launch and EIS, they may have been in a position to get it out by now, but they couldn't so 737 MAX became the stop-gap. This gives them more time to get NSA right because NSA will be the most important program Boeing launches in their history (as NRA - the A320 family replacement - will be for Airbus).

While NMA's market will be multiples smaller than NSA's, by putting NMA into production first, Boeing and their suppliers can use it to de-risk a fair bit of NSA so when they are ready to put it into production (likely in the early 2030s) it will be a smooth EIS (as was the case with MAX, which benefitted from all the refinement of the 737NG supply chain and production process).
 
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Revelation
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 4:25 pm

andrewfarmer wrote:
Can someone help me understand why Boeing is launching the NMA program when for years they have said no to a 757 replacement? Though I am admittedly lacking in aviation acumen, it appears to me that such a new program would stretch them very thin, with the 73, 77, and 78 though mature still requiring investment to maintain market position. How big of a market will the NMA reach? Instead of investing resources there, why wouldn't Boeing do a clean sheet modern redesign of the 737 which, with new tech, could possibly even fulfill range and load requirements of the rather narrow band that the NMA seeks to hit.

How many years will the 73M program carry the line into the future before it will no longer be competitive with what a modern redesign could offer? From my again not very informed opinion, I would think B would want to think about how to maintain hold of the 737 market in the next 50 years.

Boeing didn't say no, the market said no. A32x and B737 family members took much of the market that 757 inherited from 727.

NMA's market is to aim above those products to try to capture the remaining 757 and 767 replacement market as well as some new markets that would value the NMA's unique qualities. For instance we've heard QF say they would be good on domestic trunk routes where the 2nd aisle will help turnaround times. We've heard Boeing say they can make it possible to offer service on city pairs that can't support A339/B788 and above yet need more range/capacity than A32x or MAX.

In numbers, Boeing marketing is tossing around a 4000 frame potential, whereas analysts are pushing back and saying 2000 is more reasonable.

Redoing the 737 makes no sense since they've spent a lot of money developing MAX and they have a big backlog.
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JayinKitsap
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 4:46 pm

andrewfarmer wrote:
Can someone help me understand why Boeing is launching the NMA program when for years they have said no to a 757 replacement? Though I am admittedly lacking in aviation acumen, it appears to me that such a new program would stretch them very thin, with the 73, 77, and 78 though mature still requiring investment to maintain market position. How big of a market will the NMA reach? Instead of investing resources there, why wouldn't Boeing do a clean sheet modern redesign of the 737 which, with new tech, could possibly even fulfill range and load requirements of the rather narrow band that the NMA seeks to hit.

How many years will the 73M program carry the line into the future before it will no longer be competitive with what a modern redesign could offer? From my again not very informed opinion, I would think B would want to think about how to maintain hold of the 737 market in the next 50 years.


The 787 introduced a new generation of planes (as did the 350) along with a new factory floor as well. CRFP barrels and wings, true digital controls, all electric architecture, bleedless engines, etc. The MOM allows another run at this generation to tweak the production, get the excess weight out of the structure, streamline processes, etc. Boeing has indicated that it needs this iteration to improve the future design and production of the NSA. Besides the MAX investment needs a decade + of production to pay off.

As this thread is about engines, the NSA will arrive (I guess in 12-15 years) about when PW's GTF, RR's Ultrafan, and a similar CFM product will be both state of the art but also mature with excellent reliability.
 
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keesje
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 6:55 pm

andrewfarmer wrote:
Can someone help me understand why Boeing is launching the NMA program when for years they have said no to a 757 replacement? Though I am admittedly lacking in aviation acumen, it appears to me that such a new program would stretch them very thin, with the 73, 77, and 78 though mature still requiring investment to maintain market position. How big of a market will the NMA reach? Instead of investing resources there, why wouldn't Boeing do a clean sheet modern redesign of the 737 which, with new tech, could possibly even fulfill range and load requirements of the rather narrow band that the NMA seeks to hit.

How many years will the 73M program carry the line into the future before it will no longer be competitive with what a modern redesign could offer? From my again not very informed opinion, I would think B would want to think about how to maintain hold of the 737 market in the next 50 years.


Good post. Pls increase frequency. :bigthumbsup: I somewhat agree Boeing could perhaps better invest in a 737 replacement from 2025 instead of waiting until it really starts to hurt. That NSA could include a NMA sub family.
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 7:16 pm

I haven't had time to read the thread yet but am I to understand from the RFP that the 797 will definitely be a classic tube with wings and engines under them ?
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 8:40 pm

lightsaber wrote:
fsabo wrote:
parapente wrote:
Engines.To gear or not to gear,that is the question for GE .I would imagine that by now they have 100% clarity on the sfc between the two engines on Airbus A320 - or A321NEO if one wanted the closest thrust AFC comparison to what would be the mom engine thrust.

If there was a marked difference then you would see it on the range tables of the A320/321 NEO but as best I know you don't ( much) if any.
It is said that the GTF is more fuel efficient,but it must show up in the existing real world figures as to exactly what extent.No?

Personally I would have thought that creating a brand new ( for the first time ever) GTF for mature EIS in 7 years is one hell of a risk.Its not simply a question of a gearbox,all the rotational speeds -and therefore blade designs change as a result.Depending on the answer to the above fact it may not be necessary at all anyway.


The PW GTF at this point in time is a little better than the LEAP fuel burn wise. The GTF will get a 3% pip. I doubt the LEAP will get much better than it is now. PW messed up on reliability, their engine has been buggy. The LEAP is reliable, but its durability is lower than expected. In the long run the GTF may prove to be the better and more efficient engine.

The variable pitch GTF from RR should be very interesting. However, RR has the T1000 screwup. Boeing probably percievs GE as the lowest risk option. GE just happens not to use a gearbox. I think is a reputation thing, not a gearbox vs direct drive thing.

The LEAP is due to get a CMC PIP. Recall the GE9x is the launch platform.
Pratt has, eventually, promised a CMC PIP for the PW1100G.

As much as I'm a Pratt fan, this competition isn't a sprint, it will be a long Marathon.

Lightsaber


There is also compression. LEAP has 40 to 50 to 1 compression, while the GEnx has 58:1 and the GE9x is advertised at 62:1 (all figures overall ratios). So it would seem that the compression knob can be turned further in the LEAP. I too agree this will be a marathon.
 
maximairways
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 9:11 pm

fsabo wrote:
parapente wrote:
Engines.To gear or not to gear,that is the question for GE .I would imagine that by now they have 100% clarity on the sfc between the two engines on Airbus A320 - or A321NEO if one wanted the closest thrust AFC comparison to what would be the mom engine thrust.

If there was a marked difference then you would see it on the range tables of the A320/321 NEO but as best I know you don't ( much) if any.
It is said that the GTF is more fuel efficient,but it must show up in the existing real world figures as to exactly what extent.No?

Personally I would have thought that creating a brand new ( for the first time ever) GTF for mature EIS in 7 years is one hell of a risk.Its not simply a question of a gearbox,all the rotational speeds -and therefore blade designs change as a result.Depending on the answer to the above fact it may not be necessary at all anyway.


The PW GTF at this point in time is a little better than the LEAP fuel burn wise. The GTF will get a 3% pip. I doubt the LEAP will get much better than it is now. PW messed up on reliability, their engine has been buggy. The LEAP is reliable, but its durability is lower than expected. In the long run the GTF may prove to be the better and more efficient engine.

The variable pitch GTF from RR should be very interesting. However, RR has the T1000 screwup. Boeing probably percievs GE as the lowest risk option. GE just happens not to use a gearbox. I think is a reputation thing, not a gearbox vs direct drive thing.


LEAP has a lower dispatch reliability on the NEO than the GTF. GTF has higher UER.
 
JoeCanuck
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 9:26 pm

fsabo wrote:
parapente wrote:
Engines.To gear or not to gear,that is the question for GE .I would imagine that by now they have 100% clarity on the sfc between the two engines on Airbus A320 - or A321NEO if one wanted the closest thrust AFC comparison to what would be the mom engine thrust.

If there was a marked difference then you would see it on the range tables of the A320/321 NEO but as best I know you don't ( much) if any.
It is said that the GTF is more fuel efficient,but it must show up in the existing real world figures as to exactly what extent.No?

Personally I would have thought that creating a brand new ( for the first time ever) GTF for mature EIS in 7 years is one hell of a risk.Its not simply a question of a gearbox,all the rotational speeds -and therefore blade designs change as a result.Depending on the answer to the above fact it may not be necessary at all anyway.


The PW GTF at this point in time is a little better than the LEAP fuel burn wise. The GTF will get a 3% pip. I doubt the LEAP will get much better than it is now. PW messed up on reliability, their engine has been buggy. The LEAP is reliable, but its durability is lower than expected. In the long run the GTF may prove to be the better and more efficient engine.

The variable pitch GTF from RR should be very interesting. However, RR has the T1000 screwup. Boeing probably percievs GE as the lowest risk option. GE just happens not to use a gearbox. I think is a reputation thing, not a gearbox vs direct drive thing.


The gearbox in the GTF is one thing that, so far, has been pretty much bulletproof. The problems have been coming from other new tech Pratt used in the engines.

It seems to me that to get similar efficiencies to the GTF, the LEAP has to push the core a lot harder. They can because they are really good at that but it seems that they are getting close to running out of headroom on with the direct drive low pressure spool. Being able to spin the low pressure spool faster means fewer compressor and turbine stages, which means less weight and increased efficiency.

Coupling a GTF with LEAP tech seems a logical way to go.

GE has tons of experience with gears on their helicopter engines and they have been going to court to overturn Pratt and RR GTF patents so they are definitely looking at the possibility.

I think GTF engines and folding wings will grace the 797.

jagraham wrote:

There is also compression. LEAP has 40 to 50 to 1 compression, while the GEnx has 58:1 and the GE9x is advertised at 62:1 (all figures overall ratios). So it would seem that the compression knob can be turned further in the LEAP. I too agree this will be a marathon.


I suspect that might have something to do with physical engine size and the size of the planes the engines go on. Bigger engines have more size and weight margin for more compressor stages.
Last edited by JoeCanuck on Sat Jun 30, 2018 9:30 pm, edited 2 times in total.
What the...?
 
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lightsaber
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 9:34 pm

jagraham wrote:
lightsaber wrote:
fsabo wrote:

The PW GTF at this point in time is a little better than the LEAP fuel burn wise. The GTF will get a 3% pip. I doubt the LEAP will get much better than it is now. PW messed up on reliability, their engine has been buggy. The LEAP is reliable, but its durability is lower than expected. In the long run the GTF may prove to be the better and more efficient engine.

The variable pitch GTF from RR should be very interesting. However, RR has the T1000 screwup. Boeing probably percievs GE as the lowest risk option. GE just happens not to use a gearbox. I think is a reputation thing, not a gearbox vs direct drive thing.

The LEAP is due to get a CMC PIP. Recall the GE9x is the launch platform.
Pratt has, eventually, promised a CMC PIP for the PW1100G.

As much as I'm a Pratt fan, this competition isn't a sprint, it will be a long Marathon.

Lightsaber


There is also compression. LEAP has 40 to 50 to 1 compression, while the GEnx has 58:1 and the GE9x is advertised at 62:1 (all figures overall ratios). So it would seem that the compression knob can be turned further in the LEAP. I too agree this will be a marathon.

A larger engine naturally has a higher compression ratio (less tip leak are and blade surface are divided by flow area). There is also more reward for small improvements. So we can agree on more compression for both Pratt's offering and CFM.

Pratt is ready for a 3.5:1 GTF. The 797 requires more thrust than the current gearbox can reliably handle.

CFMs big advantage is being ready with CMCs. That and taking GE9x tech and using it for the 797.

IMHO, CFM will be on the airframe unless their bid defies logic.

That means Pratt and RR competing to be on the airframe. Only GE is launching a major technology improvement in time to debug the technology well in advance of 797 EIS.

Everything I've read is that Boeing is trying to minimize cost to entice launch commitments.

So I'm hugely curious what happens at Farnborough.

Lightsaber
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Planesmart
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 9:54 pm

JoeCanuck wrote:
GE has tons of experience with gears on their helicopter engines and they have been going to court to overturn Pratt and RR GTF patents so they are definitely looking at the possibility.

Both GE and RR have separately tried to overturn these PW patents, unsuccessfully.

GE may have experience, but not the broad brush patents held by PW.

PW and RR worked together on a technology demonstrator years ago. RR have a few patents from the project, but PW hold the aces.

Aero engine industry rationalisation is close. Could it be GE / PW, and if so, will GE have to divest CFM shares? Or will it be RR / PW, in which case will GE move to 100% CFM ownership? And if the latter, will the patents be retained by UTC and licensed to both?
 
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 11:04 pm

Planesmart wrote:
JoeCanuck wrote:
GE has tons of experience with gears on their helicopter engines and they have been going to court to overturn Pratt and RR GTF patents so they are definitely looking at the possibility.

Both GE and RR have separately tried to overturn these PW patents, unsuccessfully.

GE may have experience, but not the broad brush patents held by PW.

PW and RR worked together on a technology demonstrator years ago. RR have a few patents from the project, but PW hold the aces.

Aero engine industry rationalization is close. Could it be GE / PW, and if so, will GE have to divest CFM shares? Or will it be RR / PW, in which case will GE move to 100% CFM ownership? And if the latter, will the patents be retained by UTC and licensed to both?


Geared fans were around before Pratt tried it. Honeywell had GTF's on the BAE146 and every turboprop is essentially an unshrouded GTF. Turbomeca also had a GTF design and there are probably others if one digs deep enough.

Pratt may have specific patents on the gear box itself, but I think they'll have a tough time claiming propriety on the concept of a geared fan.

If they really wanted to go out there...GE could always revive their contra rotating fan design, and shroud the fans instead of using the open rotor concept. The OR was supposed to be pretty darned efficient.
What the...?
 
jagraham
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 11:42 pm

JoeCanuck wrote:
fsabo wrote:
parapente wrote:
Engines.To gear or not to gear,that is the question for GE .I would imagine that by now they have 100% clarity on the sfc between the two engines on Airbus A320 - or A321NEO if one wanted the closest thrust AFC comparison to what would be the mom engine thrust.

If there was a marked difference then you would see it on the range tables of the A320/321 NEO but as best I know you don't ( much) if any.
It is said that the GTF is more fuel efficient,but it must show up in the existing real world figures as to exactly what extent.No?

Personally I would have thought that creating a brand new ( for the first time ever) GTF for mature EIS in 7 years is one hell of a risk.Its not simply a question of a gearbox,all the rotational speeds -and therefore blade designs change as a result.Depending on the answer to the above fact it may not be necessary at all anyway.


The PW GTF at this point in time is a little better than the LEAP fuel burn wise. The GTF will get a 3% pip. I doubt the LEAP will get much better than it is now. PW messed up on reliability, their engine has been buggy. The LEAP is reliable, but its durability is lower than expected. In the long run the GTF may prove to be the better and more efficient engine.

The variable pitch GTF from RR should be very interesting. However, RR has the T1000 screwup. Boeing probably percievs GE as the lowest risk option. GE just happens not to use a gearbox. I think is a reputation thing, not a gearbox vs direct drive thing.


The gearbox in the GTF is one thing that, so far, has been pretty much bulletproof. The problems have been coming from other new tech Pratt used in the engines.

It seems to me that to get similar efficiencies to the GTF, the LEAP has to push the core a lot harder. They can because they are really good at that but it seems that they are getting close to running out of headroom on with the direct drive low pressure spool. Being able to spin the low pressure spool faster means fewer compressor and turbine stages, which means less weight and increased efficiency.

Coupling a GTF with LEAP tech seems a logical way to go.

GE has tons of experience with gears on their helicopter engines and they have been going to court to overturn Pratt and RR GTF patents so they are definitely looking at the possibility.

I think GTF engines and folding wings will grace the 797.

jagraham wrote:

There is also compression. LEAP has 40 to 50 to 1 compression, while the GEnx has 58:1 and the GE9x is advertised at 62:1 (all figures overall ratios). So it would seem that the compression knob can be turned further in the LEAP. I too agree this will be a marathon.


I suspect that might have something to do with physical engine size and the size of the planes the engines go on. Bigger engines have more size and weight margin for more compressor stages.


First, what the engine manufacturers have done with computational fluid dynamics is nothing short of incredible. They are doing more with less when it comes to the compressors and the turbines. And they aren't finished yet.
Second, once upon a time, size was a limitation. But now the engine manufacturers get more work out of a given engine stage, so size is less. But on the size front, the Pratt GTF for the A320NEO is over 6000 lb and has an 81" fan. The CF6 for the 767, 747, DC10 has an 86" fan. So the aircraft manufacturers are accepting much bigger engines for narrowbodies.

Between the two factors, it appears that the "small" engines can get quite close to the big engines with regards to fuel efficiency.
 
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sat Jun 30, 2018 11:48 pm

Aesma wrote:
I haven't had time to read the thread yet but am I to understand from the RFP that the 797 will definitely be a classic tube with wings and engines under them ?


Yep, no sonic cruiser surprise by Boeing here. :D
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JoeCanuck
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sun Jul 01, 2018 12:49 am

jagraham wrote:
JoeCanuck wrote:
fsabo wrote:

The PW GTF at this point in time is a little better than the LEAP fuel burn wise. The GTF will get a 3% pip. I doubt the LEAP will get much better than it is now. PW messed up on reliability, their engine has been buggy. The LEAP is reliable, but its durability is lower than expected. In the long run the GTF may prove to be the better and more efficient engine.

The variable pitch GTF from RR should be very interesting. However, RR has the T1000 screwup. Boeing probably percievs GE as the lowest risk option. GE just happens not to use a gearbox. I think is a reputation thing, not a gearbox vs direct drive thing.


The gearbox in the GTF is one thing that, so far, has been pretty much bulletproof. The problems have been coming from other new tech Pratt used in the engines.

It seems to me that to get similar efficiencies to the GTF, the LEAP has to push the core a lot harder. They can because they are really good at that but it seems that they are getting close to running out of headroom on with the direct drive low pressure spool. Being able to spin the low pressure spool faster means fewer compressor and turbine stages, which means less weight and increased efficiency.

Coupling a GTF with LEAP tech seems a logical way to go.

GE has tons of experience with gears on their helicopter engines and they have been going to court to overturn Pratt and RR GTF patents so they are definitely looking at the possibility.

I think GTF engines and folding wings will grace the 797.

jagraham wrote:

There is also compression. LEAP has 40 to 50 to 1 compression, while the GEnx has 58:1 and the GE9x is advertised at 62:1 (all figures overall ratios). So it would seem that the compression knob can be turned further in the LEAP. I too agree this will be a marathon.


I suspect that might have something to do with physical engine size and the size of the planes the engines go on. Bigger engines have more size and weight margin for more compressor stages.


First, what the engine manufacturers have done with computational fluid dynamics is nothing short of incredible. They are doing more with less when it comes to the compressors and the turbines. And they aren't finished yet.
Second, once upon a time, size was a limitation. But now the engine manufacturers get more work out of a given engine stage, so size is less. But on the size front, the Pratt GTF for the A320NEO is over 6000 lb and has an 81" fan. The CF6 for the 767, 747, DC10 has an 86" fan. So the aircraft manufacturers are accepting much bigger engines for narrowbodies.

Between the two factors, it appears that the "small" engines can get quite close to the big engines with regards to fuel efficiency.


That's true...kind of. You're comparing old tech to new tech. A new small engine is more efficient than an old big engine, but a new big engine is more efficient than a new small engine. It seems to me that efficiency still scales with size, if technology remains pretty much the same across the sizes. Today's Pratt NEO engine, has an 81" fan. The CF6 had an 86 inch fan, the similarly powered GEnx-2b, has an 104" fan, with significantly higher efficiency, which is not just due to fan size, but improved technology throughout the design.

The newer, more efficient engines are heavier than the older engines of similar power. CFM56-5's weight is 5200lbs and the PW1100 weight 6300 lbs.
What the...?
 
jagraham
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sun Jul 01, 2018 1:37 am

JoeCanuck wrote:
jagraham wrote:
JoeCanuck wrote:

The gearbox in the GTF is one thing that, so far, has been pretty much bulletproof. The problems have been coming from other new tech Pratt used in the engines.

It seems to me that to get similar efficiencies to the GTF, the LEAP has to push the core a lot harder. They can because they are really good at that but it seems that they are getting close to running out of headroom on with the direct drive low pressure spool. Being able to spin the low pressure spool faster means fewer compressor and turbine stages, which means less weight and increased efficiency.

Coupling a GTF with LEAP tech seems a logical way to go.

GE has tons of experience with gears on their helicopter engines and they have been going to court to overturn Pratt and RR GTF patents so they are definitely looking at the possibility.

I think GTF engines and folding wings will grace the 797.



I suspect that might have something to do with physical engine size and the size of the planes the engines go on. Bigger engines have more size and weight margin for more compressor stages.


First, what the engine manufacturers have done with computational fluid dynamics is nothing short of incredible. They are doing more with less when it comes to the compressors and the turbines. And they aren't finished yet.
Second, once upon a time, size was a limitation. But now the engine manufacturers get more work out of a given engine stage, so size is less. But on the size front, the Pratt GTF for the A320NEO is over 6000 lb and has an 81" fan. The CF6 for the 767, 747, DC10 has an 86" fan. So the aircraft manufacturers are accepting much bigger engines for narrowbodies.

Between the two factors, it appears that the "small" engines can get quite close to the big engines with regards to fuel efficiency.


That's true...kind of. You're comparing old tech to new tech. A new small engine is more efficient than an old big engine, but a new big engine is more efficient than a new small engine. It seems to me that efficiency still scales with size, if technology remains pretty much the same across the sizes. Today's Pratt NEO engine, has an 81" fan. The CF6 had an 86 inch fan, the similarly powered GEnx-2b, has an 104" fan, with significantly higher efficiency, which is not just due to fan size, but improved technology throughout the design.


I am comparing old tech to new tech by design. But also old philosophy to new philosophy (how big can you go on a narrowbody?).

But for the record
CFM56-3 compression is 30 (weight 4300 lbs); CFM 56-5 compression is 32 - 34 (weight 5250 lbs), CFM 56-7 compression is 32 (weight 5216 lbs), LEAP 1A is 40 to 50 (weight 6700 lb). So the small engine is about 30% to 33% higher compression ratio over time

GE CF6 compression CF6-6 compression 25, weight 8200 lb, CF6-50 compression 30, weight 8800 lbs, CF6-80C compression 30 weight 9500 lb, GEnx2 compression 40-50, weight 12500 lb. The improvement is better, but because of the lower starting point of the CF6-6.

In any case, the LEAP is better than the CF6 while weighing less. If LEAP is chosen for the 797, there will be a LEAP in the CF6 thrust class also. Relative to the GEnx I expect the primary SFC difference to be due to fan size since a 797 LEAP should be big enough for a scaled core to be within 5% of the GE9x core.
 
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sun Jul 01, 2018 2:00 am

JoeCanuck wrote:
jagraham wrote:
JoeCanuck wrote:

The gearbox in the GTF is one thing that, so far, has been pretty much bulletproof. The problems have been coming from other new tech Pratt used in the engines.

It seems to me that to get similar efficiencies to the GTF, the LEAP has to push the core a lot harder. They can because they are really good at that but it seems that they are getting close to running out of headroom on with the direct drive low pressure spool. Being able to spin the low pressure spool faster means fewer compressor and turbine stages, which means less weight and increased efficiency.

Coupling a GTF with LEAP tech seems a logical way to go.

GE has tons of experience with gears on their helicopter engines and they have been going to court to overturn Pratt and RR GTF patents so they are definitely looking at the possibility.

I think GTF engines and folding wings will grace the 797.



I suspect that might have something to do with physical engine size and the size of the planes the engines go on. Bigger engines have more size and weight margin for more compressor stages.


First, what the engine manufacturers have done with computational fluid dynamics is nothing short of incredible. They are doing more with less when it comes to the compressors and the turbines. And they aren't finished yet.
Second, once upon a time, size was a limitation. But now the engine manufacturers get more work out of a given engine stage, so size is less. But on the size front, the Pratt GTF for the A320NEO is over 6000 lb and has an 81" fan. The CF6 for the 767, 747, DC10 has an 86" fan. So the aircraft manufacturers are accepting much bigger engines for narrowbodies.

Between the two factors, it appears that the "small" engines can get quite close to the big engines with regards to fuel efficiency.


That's true...kind of. You're comparing old tech to new tech. A new small engine is more efficient than an old big engine, but a new big engine is more efficient than a new small engine. It seems to me that efficiency still scales with size, if technology remains pretty much the same across the sizes. Today's Pratt NEO engine, has an 81" fan. The CF6 had an 86 inch fan, the similarly powered GEnx-2b, has an 104" fan, with significantly higher efficiency, which is not just due to fan size, but improved technology throughout the design.

The newer, more efficient engines are heavier than the older engines of similar power. CFM56-5's weight is 5200lbs and the PW1100 weight 6300 lbs.

Efficiency definitively scales with size. Think of the blades in an engine:
1. At the tip air leaks (backwards in a compressor, forwards in the turbine). The tip clearance is a technology (constantly being reduced). For a larger engine there is less leak area to flow area, do the compressor efficiency is notably higher and slightly more efficient turbines.
2. Larger engines have less surface area drag. The easiest way to see this is the inner and outer flow path cylinder areas are less than the flow path area for a larger engine, this makes the engine more efficient, lower ratio of cooled area to flow path area in the hot sections (less cooling per unit of thrust improves efficiency).
3. Weight of components per unit of thrust could go down. In a larger engine, the pressure vessel just weights less per unit of thrust. Because of this, the optimal pressure ratio goes up bringing back up the weight.
4. Value of adding technology to an engine goes up with size. The more fuel burned but engine, the earlier the business case. For example, another low turbine stage price goes up less than a linear function of thrust. So for a Pratt GTF, it is not worth putting on a 4th turbine stage of a design optimized for the 2 hour mission (Airbus NEO design point). For a higher thrust engine optimized for a longer mission (4 or 5 hours in my opinion, the 787 engines were optimized for 8 hours for reference). This pays for a 4th turbine stage to drive a higher bypass fan.

The optimal mission length is critical. Certain technology increases climb fuel burn to reduce cruise fuel burn (e.g., bypass ratio beyond the climb optimal). Variable cycle technology breaks the trade at a maintenance and purchase cost. For example the GTFs were to have variable fan nozzles, a technology that breaks even at the 1.5 hour mission. Pratt wisely decided to remove the tech to cut risk. GE has a valve to vary turbine cooling. This was expensive to develop tech (tough packaging), but pays off at 1 hour,but this won't fit in less than 25,000lbf thrust engines.

For longer missions, turbine clearance cooling should be more precise and granular. This requires heavier and more expensive flow control. Stuff that isn't worth it for the 2 hour mission but is for the 4 hour optimization. The GE9x is taking this to the extreme. No just turbine clearance controlled by cooling the casing. , But new cooling that takes the engine to an insane level of precision. Precision decreases cruise fuel burn, but cannot be used in climb without high risk, so the added weight hurts climb fuel burn as the systems opperate very open in climb to prevent frying the turbine. Cruise is much easier to predict..

So larger engines are more efficient and engines optimized for longer missions are more efficient (at range). Wait for the GE9x, that engine is GE's big technology risk.

Lightsaber
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sun Jul 01, 2018 2:16 am

jagraham wrote:

I am comparing old tech to new tech by design. But also old philosophy to new philosophy (how big can you go on a narrowbody?).

But for the record
CFM56-3 compression is 30 (weight 4300 lbs); CFM 56-5 compression is 32 - 34 (weight 5250 lbs), CFM 56-7 compression is 32 (weight 5216 lbs), LEAP 1A is 40 to 50 (weight 6700 lb). So the small engine is about 30% to 33% higher compression ratio over time

GE CF6 compression CF6-6 compression 25, weight 8200 lb, CF6-50 compression 30, weight 8800 lbs, CF6-80C compression 30 weight 9500 lb, GEnx2 compression 40-50, weight 12500 lb. The improvement is better, but because of the lower starting point of the CF6-6.

In any case, the LEAP is better than the CF6 while weighing less. If LEAP is chosen for the 797, there will be a LEAP in the CF6 thrust class also. Relative to the GEnx I expect the primary SFC difference to be due to fan size since a 797 LEAP should be big enough for a scaled core to be within 5% of the GE9x core.


Technology being equal, the larger engine should be more efficient. The MOM LEAP derivative should be aided by efficiencies of scale, since it will be bigger than the LEAP, with a bigger core and fan.

lightsaber wrote:

So larger engines are more efficient and engines optimized for longer missions are more efficient (at range). Wait for the GE9x, that engine is GE's big technology risk.

Lightsaber


You actually know what you're talking about. I'm just guessing.
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sun Jul 01, 2018 2:56 am

keesje wrote:
andrewfarmer wrote:
Can someone help me understand why Boeing is launching the NMA program when for years they have said no to a 757 replacement? Though I am admittedly lacking in aviation acumen, it appears to me that such a new program would stretch them very thin, with the 73, 77, and 78 though mature still requiring investment to maintain market position. How big of a market will the NMA reach? Instead of investing resources there, why wouldn't Boeing do a clean sheet modern redesign of the 737 which, with new tech, could possibly even fulfill range and load requirements of the rather narrow band that the NMA seeks to hit.

How many years will the 73M program carry the line into the future before it will no longer be competitive with what a modern redesign could offer? From my again not very informed opinion, I would think B would want to think about how to maintain hold of the 737 market in the next 50 years.


Good post. Pls increase frequency. :bigthumbsup: I somewhat agree Boeing could perhaps better invest in a 737 replacement from 2025 instead of waiting until it really starts to hurt. That NSA could include a NMA sub family.


Boeing has 4500 737MAX on order and likely more orders coming. The 797 segment for a 767-200/300 sized plane currently has very little competition with the potential for thousands of orders.

Some people view the A321 as extraordinary and invincible, but I think that reflects an Airbus dreamworld that ignores that the 737MAX has 43% market share.

viewtopic.php?f=3&t=1397931

Selecting engines is one of many milestones on the way to the 797 becoming reality
 
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kitplane01
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sun Jul 01, 2018 3:50 am

lightsaber wrote:
jagraham wrote:
lightsaber wrote:
The LEAP is due to get a CMC PIP. Recall the GE9x is the launch platform.
Pratt has, eventually, promised a CMC PIP for the PW1100G.

As much as I'm a Pratt fan, this competition isn't a sprint, it will be a long Marathon.

Lightsaber


There is also compression. LEAP has 40 to 50 to 1 compression, while the GEnx has 58:1 and the GE9x is advertised at 62:1 (all figures overall ratios). So it would seem that the compression knob can be turned further in the LEAP. I too agree this will be a marathon.

A larger engine naturally has a higher compression ratio (less tip leak are and blade surface are divided by flow area). There is also more reward for small improvements. So we can agree on more compression for both Pratt's offering and CFM.

Pratt is ready for a 3.5:1 GTF. The 797 requires more thrust than the current gearbox can reliably handle.

CFMs big advantage is being ready with CMCs. That and taking GE9x tech and using it for the 797.

IMHO, CFM will be on the airframe unless their bid defies logic.

That means Pratt and RR competing to be on the airframe. Only GE is launching a major technology improvement in time to debug the technology well in advance of 797 EIS.

Everything I've read is that Boeing is trying to minimize cost to entice launch commitments.

So I'm hugely curious what happens at Farnborough.

Lightsaber



I would love to see a CFM core combined with a PW Geared Fan. Technologically, I think that's the best possible combination. Anyone wanna guess what the performance improvement over either companies engine might be? Anyone wanna guess what time scale you'd need to accomplish this?
 
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sun Jul 01, 2018 4:26 am

kitplane01 wrote:

I would love to see a CFM core combined with a PW Geared Fan. Technologically, I think that's the best possible combination. Anyone wanna guess what the performance improvement over either companies engine might be? Anyone wanna guess what time scale you'd need to accomplish this?


That would be one way for Pratt to get into the larger engine market.
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sun Jul 01, 2018 6:18 am

Stitch wrote:
Boeing has been working on the 737 replacement - NSA - for close to a decade.


Really? Has any design info been shared?
 
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sun Jul 01, 2018 6:37 am

Revelation wrote:
Redoing the 737 makes no sense since they've spent a lot of money developing MAX and they have a big backlog.


That makes it sound like a new aircraft. It’s been around since the 1960’s. How much “developing” has Boeing really done, ie, updating vs a completely new aircraft?
 
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sun Jul 01, 2018 10:42 am

questions wrote:
Revelation wrote:
Redoing the 737 makes no sense since they've spent a lot of money developing MAX and they have a big backlog.


That makes it sound like a new aircraft. It’s been around since the 1960’s. How much “developing” has Boeing really done, ie, updating vs a completely new aircraft?


Obviously a lot less developing than it would take for a new aircraft (same for A32X NEO) but it still cost them over $1 billion to do it. They made necessary changes (strengthening and gear modifications) as well as changing the tail and winglets for efficiency. They also changed the spoilers to FBW.
 
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sun Jul 01, 2018 11:23 am

questions wrote:
Stitch wrote:
Boeing has been working on the 737 replacement - NSA - for close to a decade.


Really? Has any design info been shared?


http://m.aviationweek.com/commercial-aviation/boeing-revisits-past-hunt-737757-successors

Of course development programs are ongoing to get new technology through it different TRL's . You can't start development when you need someting new soon. Communication useally benefits short term objectives & contains the neccesary disclaimers to support "rapid change" of insight / strategy.
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sun Jul 01, 2018 11:53 am

The PW GTF architecture has a slight weight advantage on the neo over the leap. I can't recall whether it's 200kg per engine or airframe. It would be interesting to know whether that difference increases as you scale the two designs up for higher thrust.
 
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keesje
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sun Jul 01, 2018 1:15 pm

Combining different technology roadmaps, e.g. ceramic materials, gearboxes, high BPR's, OPR, EGT margin and adjustable fan pitch could help, but risk spreading / cooperation could become a good idea (again).
"Never mistake motion for action." Ernest Hemingway
 
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Revelation
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sun Jul 01, 2018 2:03 pm

questions wrote:
Revelation wrote:
Redoing the 737 makes no sense since they've spent a lot of money developing MAX and they have a big backlog.

That makes it sound like a new aircraft. It’s been around since the 1960’s. How much “developing” has Boeing really done, ie, updating vs a completely new aircraft?

I don't think "developing" only happens when one creates an all new product. If so, a lot of "development engineers" have the wrong titles.

Newbiepilot wrote:
keesje wrote:
I somewhat agree Boeing could perhaps better invest in a 737 replacement from 2025 instead of waiting until it really starts to hurt.

Boeing has 4500 737MAX on order and likely more orders coming. The 797 segment for a 767-200/300 sized plane currently has very little competition with the potential for thousands of orders.

The MAX already has enough orders to get it to 2025, and more keep coming in. The only "hurt" Boeing is feeling comes from figuring out how to build them faster.
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Stitch
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Re: Boeing has given the 3 Major Engine Manufacturers until June 27 to submit their 797 engine proposals

Sun Jul 01, 2018 3:18 pm

questions wrote:
That makes it sound like a new aircraft. It’s been around since the 1960’s. How much “developing” has Boeing really done, ie, updating vs a completely new aircraft?


A fair bit considering that even though it's been around since the 1960's it's still competitive with a design that's been around since the 1980's (that itself has hardly stood still in terms of development).
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