I am curious about the idea of engine partnerships, primarily the CFM partnership. CFM engines are used on the 737-300-900 (exclusively) series, A32X series and A340-200/300. Given that this is a huge number of engines (tens of thousands), why did GE partner up with Snecma? Why didn't they just design the engine themselves?

I realize that this may seem like a little bit of a stupid question. Perhaps they didn't have the expertise in that class, but did have the capital. Perhaps Snecma had some technologies that allowed the engine to be the success that it became. Perhaps no one expected the engine to be that successful. I don't know, but I assume there are some good answers. Perhaps, why hasn't GE just bought Snecma outright, given their massive size and resources? I suppose similar questions also arise in relationship to the EA engine on the A388, the IAE engines on the A32X, and others. Although, I believe given the smaller sales of engines in the class of, say, the EA engine on the A388 and the relative lack of sales on the frame, such partnerships hedged well against risk.

I look forward to your insights. Many thanks in advance.

I have not. I usually shy away from the wiki on technical information, but I will definitely give it a read. Thanks for the advice.

Spreading the risk would seem to be logical choice?

CFM was simple. SAFRAN/SNECMA couldn't develop a high spool with a research budget, but they could develop a low spool using the F101 fighter engine high spool. GE saw little market opportunity, but they were willing to market the engine and spend a little on R&D. When the engine was bid on the 737 re-engine, after being on the DC-8, it was a surprise Boeing gave them a chance.

GE never would have developed the engine at there cost (the first few years of CFM were very costly for the French). But a contract is a contract and they expanded on the A320, A340, and 737NG. GE wanted out for the 737NG, but was contractually bound.

No one would have considered a SNECMA engine back then. Sorry... But not enough if a maintenance track record. In fact, Dassault fighters we're being asked for to have the option of being equiped with GE engines way back then due to issues

The Pratt/GE joint venture was similar as GE used a scaled high spool and made Pratt suck up a lot of the R&D costs. Not as popular...

MTU and Pratt have joint ventures on the GTFs and PW800 engines as MTU had compressor technology to be merged with Pratt technology.

The GE-90 is a GE SAFRAN joint venture under GE administration instead of a joint administration.

For whatever reason, Americans do better combustors and turbines and Europeans do better compressors and the French do the best flight control software, but FADAC hardware is a British/American specialty. The Russians are way better than everyone else (still, IMHO) due to a history of conscripted mechanics who you had to make sure only took apart what you wanted... Germans and Americans do best for designing for future markets (thrust growth and ensuring the initial design is PIP ready). The Japanese do exceptionally well for design for maintenance.

In my opinion different education systems produce engineers optimized for different systems. The joint venture are simply the legal means of utilizing a host of skill sets.

Lightsaber

lightsaber wrote:

For whatever reason, Americans do better combustors and turbines and Europeans do better compressors and the French do the best flight control software, but FADAC hardware is a British/American specialty. The Russians are way better than everyone else (still, IMHO) due to a history of conscripted mechanics who you had to make sure only took apart what you wanted... Germans and Americans do best for designing for future markets (thrust growth and ensuring the initial design is PIP ready). The Japanese do exceptionally well for design for maintenance.

The Russians are better at what? Ease of maintenance? Simplicity?

The Russians are the best at building things that either a) don't need fixing or b) can be fixed with only a hammer and a bottle of vodka.

May be a bit cliché, isn't it?

Remember:

"Heaven is where the police are British, the lovers French, the mechanics German, the chefs Italian, and it is all organized by the Swiss."

"Hell is where the police are German, the lovers Swiss, the mechanics French, the chefs British, and it is all organized by the Italians."

lightsaber wrote:

[...]

MTU and Pratt have joint ventures on the GTFs and PW800 engines as MTU had compressor technology to be merged with Pratt technology.

[...]

For whatever reason, Americans do better combustors and turbines and Europeans do better compressors and the French do the best flight control software, but FADAC hardware is a British/American specialty. The Russians are way better than everyone else (still, IMHO) due to a history of conscripted mechanics who you had to make sure only took apart what you wanted... Germans and Americans do best for designing for future markets (thrust growth and ensuring the initial design is PIP ready). The Japanese do exceptionally well for design for maintenance.

Very interesting - thank you for this post! With regards to MTU Aero Engines: is it just the compressors that they excel in or also the turbines (LPT)? - After all, the GTF LPT looks like a complete redesign compared to the V2500 and (at least to my amateur eye) seem to be quite revolutionary.

gtae07 wrote:

lightsaber wrote:

For whatever reason, Americans do better combustors and turbines and Europeans do better compressors and the French do the best flight control software, but FADAC hardware is a British/American specialty. The Russians are way better than everyone else (still, IMHO) due to a history of conscripted mechanics who you had to make sure only took apart what you wanted... Germans and Americans do best for designing for future markets (thrust growth and ensuring the initial design is PIP ready). The Japanese do exceptionally well for design for maintenance.

The Russians are better at what? Ease of maintenance? Simplicity?

Welding... One word missing. And simplicity. Very elegant designs inside their engines.

First, I was too harsh on the PW812 in one category: peak cruise Mach #. No centrifugal compressor engine will match it.

WholaLottaLove wrote:

lightsaber wrote:

[...]

MTU and Pratt have joint ventures on the GTFs and PW800 engines as MTU had compressor technology to be merged with Pratt technology.

[...]

For whatever reason, Americans do better combustors and turbines and Europeans do better compressors and the French do the best flight control software, but FADAC hardware is a British/American specialty. The Russians are way better than everyone else (still, IMHO) due to a history of conscripted mechanics who you had to make sure only took apart what you wanted... Germans and Americans do best for designing for future markets (thrust growth and ensuring the initial design is PIP ready). The Japanese do exceptionally well for design for maintenance.

Very interesting - thank you for this post! With regards to MTU Aero Engines: is it just the compressors that they excel in or also the turbines (LPT)? - After all, the GTF LPT looks like a complete redesign compared to the V2500 and (at least to my amateur eye) seem to be quite revolutionary.

The low turbine is more like a compressor. Where Americans excel is the cooled turbine blades. I should have been more specific.

lightsaber wrote:

For whatever reason, Americans do better combustors and turbines and Europeans do better compressors and the French do the best flight control software, but FADAC hardware is a British/American specialty. The Russians are way better than everyone else (still, IMHO) due to a history of conscripted mechanics who you had to make sure only took apart what you wanted... Germans and Americans do best for designing for future markets (thrust growth and ensuring the initial design is PIP ready). The Japanese do exceptionally well for design for maintenance.

In my opinion different education systems produce engineers optimized for different systems. The joint venture are simply the legal means of utilizing a host of skill sets.

Lightsaber

The Italians do great gearboxes for GTF engines !!

QuarkFly wrote:

The Italians do great gearboxes for GTF engines !!

Right? The Gearbox is fantastic. The rest of the engine has had issues with the rotor, the casing, the combustor, wasn't there something with the HPT? It's as if PW forgot how to build an engine.

QuarkFly wrote:

lightsaber wrote:

For whatever reason, Americans do better combustors and turbines and Europeans do better compressors and the French do the best flight control software, but FADAC hardware is a British/American specialty. The Russians are way better than everyone else (still, IMHO) due to a history of conscripted mechanics who you had to make sure only took apart what you wanted... Germans and Americans do best for designing for future markets (thrust growth and ensuring the initial design is PIP ready). The Japanese do exceptionally well for design for maintenance.

In my opinion different education systems produce engineers optimized for different systems. The joint venture are simply the legal means of utilizing a host of skill sets.

Lightsaber

The Italians do great gearboxes for GTF engines !!

They make the best gears. But Pratt invested how long in figuring out the cooling of the gearbox? So that one gets a joint kudos.

As to Pratt forgetting how to make an engine, their issue is they lay off the support engineers between engines (or just use contractors) who do all the details for the secondary systems which impact the performance of the main systems.

The seals/shaft/bearings is because the PW1100G pushes the limit on relative shaft speeds between the high and low spools. Oh, lessons learned, so the next engines will be pushed further... But for now, it is an issue. Pratt also went with new barrier coatings on the combustor/turbine. There seem to be some issues.

Lightsaber

lightsaber wrote:

Pratt invested how long in figuring out the cooling of the gearbox

lightsaber, why is gearbox cooling such an issue? I've also seen quotes from RR engineers say that's a difficult issue. There's a big fan pumping huge amounts of air around the engine, and warming it up a little with a gearbox cooler would even expand it a little. There's also a huge amount of cool fuel available to cool things. Is it there's just not enough thermal conductivity in the oil?

kurtverbose wrote:

lightsaber wrote:

Pratt invested how long in figuring out the cooling of the gearbox

lightsaber, why is gearbox cooling such an issue? I've also seen quotes from RR engineers say that's a difficult issue. There's a big fan pumping huge amounts of air around the engine, and warming it up a little with a gearbox cooler would even expand it a little. There's also a huge amount of cool fuel available to cool things. Is it there's just not enough thermal conductivity in the oil?

Remebering the RR story, even with almost perfect efficiency of 99% for the gear it is still a huge amount of heat, 100kW-1MW range.
Keep in mind how much MW power an engine has.

sciing wrote:

Remebering the RR story, even with almost perfect efficiency of 99% for the gear it is still a huge amount of heat, 100kW-1MW range.
Keep in mind how much MW power an engine has.

This was the quote, from Professor Ric Parker, director of research and technology at Rolls Royce: -

"Our first gear application is going to be right at the top end of the thrust range, Whereas Pratt and Whitney has a gearbox that transmits about 25MW, we are talking about a 50MW gearbox. So even when we achieve 99% efficiency in that gear, we have got to find somewhere for that 500kW to go. That will probably be lost as heat in the oil system, but that is still a lot of heat for the oil. So we have to be sure we are going to get a very efficient gearbox, more than 99%."

So it's 500kw, which is not inconsiderable, but adding heat to the bypass stream is no bad thing. Transmitting 500kw through a small amount of oil maybe though - I don't know, hence my question.

One basic thing about partnerships is the cost of engine development. It is approaching $4 billion today for a major new line. Only the major new lines get the latest technology. For the MoM, that will be required. As it was for the 777X, A350NEO, 787, A320NEO, and MAX.

The MAX is a great example. It is part of the CFM partnership. Initially the partnership tried to pawn off the A320 high spool to save a billion or so in development costs. But that would have made the 737 noncompetitive. So Boeing made it clear they would have to offer a 2nd engine in that scenario. Amazing how that motivated the partnership.

The 777X is almost a partnership due to the high amount of SAFRAN content. Same with the GEnX engines on the 787 and 747. But not quite a partnership of the CFM level, more a defined ownership of certain components.

The PW1100G on the NEO is in reality a partnership, just that MTU is a junior partner instead of 50/50, but there are firm conditions on that partnership that also include the smaller PurePower core on the PW1500G, PW1200G, PW800, and the other variations.

kurtverbose wrote:

lightsaber wrote:

Pratt invested how long in figuring out the cooling of the gearbox

lightsaber, why is gearbox cooling such an issue? I've also seen quotes from RR engineers say that's a difficult issue. There's a big fan pumping huge amounts of air around the engine, and warming it up a little with a gearbox cooler would even expand it a little. There's also a huge amount of cool fuel available to cool things. Is it there's just not enough thermal conductivity in the oil?

The failure modes must be engineered to be benign.

Back when radial (piston) engines had gearboxes, half of engine failures were the gearbox and the gearbox failures were often spectacular (flames, gears going through the body of the aircraft and even people).

The cooling is an issue is if a hot spot forms, say due to small bits of metal in the oil, it accelerates wear at that part of the gear. If the cooling isn't optimized to right that gear tooth hot spot, it will war/fail early. What needs to be done is excellent cooling, with all wear and manufacturing tolerances, What Pratt invested in heavily is being able to measure the gear oil temperature and other properties to have an understanding of when the gearbox will fail.

For if an airline cannot know about a gearbox failure 400+ flights ahead of time, they cannot schedule a maintenance visit timely. For recall if the algorithm is predicting 400 flights to failure, you have 1/3rd the time to replace the defective part or 133 flights, or just over a week or so of intense flying (failures always happen at inopportune times). A big part of the GTF is ensuring when the gearbox fails it can be done with enough time to:
1. Get the part to the maintenance base (2 or 3 days) as well as a spare engine (often kept at Pratt/MTU or other maintenance partner and not the airlines)
2. Schedule the plane to the maintenance base with minimum to no disruption of schedule.
3. Time to swap out a replacement engine
4. Time to swap out the gearbox
5. Time to put the fixed (new garbox) engine back onto the original airframe that once again passes through the maintenance base with little to no disruption to schedule.

Now the above is the ideal. Or should I say the plan.. Pratt put many spare engines into the field for the A320NEO EIS. But the plan was for them to sit there and then be pulled back, un-used, to be put onto production airframes. Instead, new production engines had to be diverted to the field as spares. The combination of not having spares returned and diverted production engines resulted in many airframes going out without engines. Yes, the fan blade production is an issue, but an issue exacerbated by the need for far more spares than plan.

If the gearbox cooling is not well understood and engineered over the huge range of temperatures and loads an engine operates at... Gearboxes will fail early and spectacularly (gear oil fires) with the potential that gears are sent into the aircraft body. (Yikes!) Not as bad as a turbine rotor failure, but a bad day.

There are other issues with the gearboxes on flying gas turbine engines. The packaging is far less than ideal due to the aerodynamic m on the air going into the core of the engine. The gearbox cannot have any vibration modes that couple with the rest of the engine or there is going to be a really bad day... The gearbox must be designed in a way for easy balancing as gas turbines have nasty responses (mostly wear, nothing dramatic really) to a gearbox being out of balance.

Heat in gearboxes is non-linear with thrust (or horsepower). So making a gearbox for the MoM is far harder than the PW1100G (NEO)which is far harder than the PW1500G. It takes years to engineer, test, realize the mistakes, and re-test.

Here is an article from 2014 on RR GTF work:
http://www.eurekamagazine.co.uk/design- ... fan/65879/

I have no links, but I know they were working on and off on GTFs since the mid-1990s (at least).

Pratt made public their larger GTF plans back in 2013:
http://aviationweek.com/awin/pratt-whit ... rowth-plan


RR won't be ready for a 50k GTF in time, nor GE. But Pratt is not going to get on the MoM alone after the PW1100G EIS issues. I'm a Pratt fan, but reality must be accepted. RR needs Pratt for the GTF. What I've seen in the Press stinks of negotiating bluster.

CFM has their variable cycle (turbine cooling) technology as well as CMC turbine blades and RR will need Pratt's variable fan technology as well as a developed gearbox.

So it looks like for the next platform, it will be a pair of partnerships. CFM as they must by contract. RR won't be competitive without Pratt and Pratt wouldn't be accepted.


LIghtsaber

… and Pratt, to be accepted, will have to be a junior partner, as you hinted somewhere else… Could the PW1XXXG be their last own big civilian engine?

Aircellist wrote:

… and Pratt, to be accepted, will have to be a junior partner, as you hinted somewhere else… Could the PW1XXXG be their last own big civilian engine?

Technically the PW1527G is 'big.'

Only? For now I think so. But Pratt will work on larger gearboxes and airframers will tell Pratt what they expect in a certification program to advance.

The reality is CFM has better specification. Not as good as Embraer, but better than Pratt. Those specifications force improved reliability. In my opinion, Pratt and RR are about equivalent, but RR has the benefit of related engines and an experienced team that has developed engines; or they did before recent head count reductions. Cest la vie, that is the cycle.

Lightsaber

… I did not know how to place the PW1000G series as a whole… thanks . I meant "big" as opposed to the "small" engines of P&WC, my (almost) home town engine builders.

It will be a huge job for Pratt to come back as a main designer, especially if they turn into developing gearboxes. If, every time there is any downturn, the experienced persons are fired, then, reconstructing the knowledge basis necessary to build up from scratch a whole engine, with the length of the life cycle of modern engines, with the huge sums needed, will be an incredible task, and will feel like starting anew in that business.

I can see them turning into a giant Fiat Avio for big civilian gearboxes, and doing their best to keep a foot in the small civilian and the military market. But there is pressure there as well.

…edit… My main point is that there may never be a PW2xxxG series…

Aircellist wrote:

… I did not know how to place the PW1000G series as a whole… thanks . I meant "big" as opposed to the "small" engines of P&WC, my (almost) home town engine builders.

It will be a huge job for Pratt to come back as a main designer, especially if they turn into developing gearboxes. If, every time there is any downturn, the experienced persons are fired, then, reconstructing the knowledge basis necessary to build up from scratch a whole engine, with the length of the life cycle of modern engines, with the huge sums needed, will be an incredible task, and will feel like starting anew in that business.

I can see them turning into a giant Fiat Avio for big civilian gearboxes, and doing their best to keep a foot in the small civilian and the military market. But there is pressure there as well.

…edit… My main point is that there may never be a PW2xxxG series…

I seem to recall a PW2038.

I think there will be a 2nd generation GTF with Pratt as Prime, but it will take time. It will also take new platforms.
I just do not see a new platform, except for the MoM, for quite a few years. Airbus made the A330NEO to fill a niche (a mistake IMHO), the A350, not investing in the A380 while Boeing has the 777X, 787 in multiple lengths, the MoM, and the MAX.

Due to technology transfer demands, Pratt isn't on board with the Chinese planes. The Chinese want GTF or high mach # high spool technology Pratt will not share with anyone.

So Pratt will have to retreat to business jets (they already have the RJ market pretty well sewn up with the PW1200G family to be offered for new variants). There will be a new centrifugal compressor high spool for the PT6 market and smaller thrust business jets to compete with the Silvercrest.

Pratt isn't done, they just didn't pull off their re-entry correctly with the PW1100G and production volumes of the PW1500G. Sigh...

Lightsaber

Revelation wrote:

lightsaber wrote:

Pratt made public their larger GTF plans back in 2013:
http://aviationweek.com/awin/pratt-whit ... rowth-plan

Some interesting stuff from that article, written ~4 years ago:

“The Leap will go into revenue service on the A320NEO 1% better than the competition, based on testing to date,” says Chaker Chahrour, CFM executive vice president. “It will retain that 1% better than the competition, which when you integrate over time adds up to another 1%. And on the A321NEO, because of the longer legs and our better cruise sfc bucket, we get another 1%.”

Pratt did well on fuel burn, initial LEAP missed... big.

But time on wing matters more.

Lightsaber

AA777223 wrote:

Perhaps, why hasn't GE just bought Snecma outright, given their massive size and resources?

SNECMA had the idea of a high bypass engine ( going forward from their M55 project afaik ) at the time
and needed a partner with established market penetration. -> GE.

GE buying Snecma was out of the question for various reasons
GE probably did not (fore)see the future greatness but having some fingers in the cookie is always ok
and then France ( always working towards technological independence ) selling off advanced industries was out of the question.

Doesn't it actually work out very well for GE as they have the highest profit share of the engine?

lightsaber wrote:

GE never would have developed the engine at there cost (the first few years of CFM were very costly for the French). But a contract is a contract and they expanded on the A320, A340, and 737NG. GE wanted out for the 737NG, but was contractually bound.

Just out of curiosity why did GE want out on the 737NG, or were they just not anticipating how successful the 737NG (and A320, considering at that time it was still fairly early in its life and still trying to break though) turned out to be for CFM?

Polot wrote:

lightsaber wrote:

GE never would have developed the engine at there cost (the first few years of CFM were very costly for the French). But a contract is a contract and they expanded on the A320, A340, and 737NG. GE wanted out for the 737NG, but was contractually bound.

Just out of curiosity why did GE want out on the 737NG, or were they just not anticipating how successful the 737NG (and A320, considering at that time it was still fairly early in its life and still trying to break though) turned out to be for CFM?

Yeah, that's news to me as well.

One of the tricky things with partnerships is the different priorities that members have. PW was really annoyed that the other V2500 members were not as eager to PIP the engine as CFM was in the early oughts, so they lost a number of sales and eventually bought out RR.

Similarly, Snecma got worse profit share on the CFM56 than GE did, and was consequently less willing to play the pricing game. In the late 90s this caused a huge rift between Airbus and Snecma, because the engine OEM bloodbath going on with the 777 was keeping prices down on that frame while the A340 was single-source. One of the senior Airbus people at the time griped that "Snecma is trying to kill the 340" because they couldn't price-compete on engines.