Leeham News and Analysis
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Leeham News and Analysis
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“Hyper focus on reliability and durability out of the gates”
By Scott Hamilton
THE CFM Open Fan engine could be at least 20% more fuel efficient than today’s CFM LEAP and P&W GTF, CFM partners say. Credit: CFM.
Sept. 11, 2024, © Leeham News: GE Aerospace and Safran advance on the CFM RISE Open Fan engine with an overriding goal: “Our customers really want us to be hyper-focused on reliability and durability out of the gates.”
GE and Safran are developing a potentially game-changing engine and marketing it via the 50-50 joint venture, CFM International. The entry-into-service goal is 2035.
Customer demand for reliability and durability “out of the gates” is understandable. Engines produced by CFM, Pratt & Whitney and Rolls-Royce disappointed Airbus and Boeing customers operating the Airbus A320neo family, the Boeing 737 MAX and 787 and now the Airbus A350. Durability and/or technical issues plagued the CFM LEAP, Pratt & Whitney Geared Turbo Fan (GTF), Rolls-Royce Trent 1000 and now the RR Trent XWB-97. The giant GE9X engines on the Boeing 777X also suffered technical problems during the long, extended flight testing.
Operators protested as on-wing time fell short of promises. 787s, A220s, A320neos, and to a lesser extent Embraer E195-E2s were grounded as engines components failed, MRO shops backed up (displacing routine overhaul requirements on older engines) and new-production engines were diverted to replace those on grounded aircraft.
The CFM LEAP, GE and Safran promise, will provide a 20% reduction in fuel consumption and emissions. But the radical technology of an Open Fan gives airlines, lessors and even Boeing pause.
GE and Safran say they are progressing through development of the 35,000+ lb thrust engine but there is a lot of work to do to make it ready for service and give customers confidence.
Decarbonization was the driver
“In 2021, we decided jointly to go on the same path…,” said Safran CEO Olivier Andries. “We thought that having been in a leader position in this marketplace, we had to be disruptive. We had to be disruptive, because we thought it was our duty to be at the leading edge of the decarbonization.”
Andries said GE and Safran wanted to be in a position to offer a propulsion solution that could bring up to 20% fuel burn improvement vs the latest generation of engine that is currently flying, and that is currently produced, referring to the CFM LEAP engine.
To get 20% fuel burn improvement, “you have to be disruptive to get there. We were convinced that should we go on a conventional pathway, with what we call a ducted engine, the best we could achieve is 10%.”
The solution was the Open Fan engine, an evolution of the Open Rotor concept developed and tested 40 years ago.
“With the Open Fan, basically we break the wall. We can increase significantly the diameter of the fan,” Andries said. “That’s what brings the propulsive efficiency to basically a level that has never been reached today.”
Hyper focus on durability and reliability
“We have learned through successive generations of product launches that in addition to that efficiency step function improvement, our customers really want us to be hyper- focused on reliability and durability out of the gates. These engines fly for decades. The CFM56 today is the industry benchmark. They want that level of reliability and durability day one.”
Culp said successful ground tests and ultimately flight tests of the engine will be how to achieve these desires. Airbus is slated to install an Open Fan demonstrator on an A380 flying test bed.
“We’re talking about an engine that we probably won’t see in service for another decade,” Culp said. “There’s still a lot of work to do.”
Neither CEO addressed the obvious: without a qualifying engine, neither Airbus nor Boeing can launch a new airplane product.
The CEOs made their remarks at the US Chamber of Commerce Aerospace Summit in Washington (DC) on
Sept. 10.
The size of the fan is slightly smaller than the DC-7 prop diameter and has anti swirl vanes, so installation should be easier than the Wright R-3350 on wing. But lots of things can go wrong, vibrations; anti-ice; blades hard time on wing as you don’t have a containment case; fan blade pitch mechanism and the integrated engine/prop FADEC; electrical power hybrid system if installed to name a few.
Composite blades, at least on the GE90, are hard timed even with a fan case. Hollow metal blades too on the Trent 700.
Are there even certification requirements for variable pitch and pitch stop mechanisms?
The cert for udf fan blades should be similar to turboprop prop system.
My understanding is that installation into the wing is undesirable?
As was pointed out (sorry I forget who) that the PenAir crash in Alaska had ramifications for Props.
The crash itself was a landing failure not a prop failure to be clear.
But as they were veering off the runway, the left props took a hit and sheared and penetrated the cabin. I don’t know where (and yes it matters to a degree) but penetrate they did.
Like the A380 engine blowup where shrapnell went everywher and in places and a quantity neve predicted, its a consideration you have to look at going forward.
Now Airbus did a fantastic job on the A380 structure. They also had more reudant systesm than required and that saved teh aircrat. It was desinged better than minium, they adhered to and exceeded all regs for that type incident. What was unprecendated was how bad the incident was per previous ones and the regs were written to. You can’t predict an unknown, but you do have to factor that in going forward.
So yes planes go off runways, one of the most common incidents, but they also hit things and if you can’t contain the props then you have a problem.
Sure you can grandfather in and continue production (or bring a Dash 8 back under the same rules).
But in this case, more props and more chances to shear and penetrate and in places you can’t model.
And the energy content of those props is 30k equal thrust roughly.
DC-7C 4 blade prop diameter was 168 inch while the Constellation 3 blade diameter was 182 inch
The GE9X is 130 inch fan with a bigger nacelle
Could Rise be a wing mounted pusher ?
it would make sense for it to be mounted over-wing as with the Hondajet for several reasons
aero reasons: you would likely need to go high wing in order to maintain reasonable ground clearance and landing gear length which would have large aerodynamic penalties unless you are willing to sacrifice several rows of seats in the middle of the plane
structural reasons (shorter, lighter landing gear and lighter weight related structures being a big part of that)
ground handling and airport compatibility: an underslung low wing would need very tall landing gear resulting in a very high fuselage which would require updates to a lot of narrowbody gates which are engineered around 737 & a320 fuselage heights. there would also be significant ground handling issues in terms of ground crew safety and FOD.
More likely an A400 type of installation in front of the high wing with exhaust under the wing. The hydrogen aircraft designers like the high wing for routing hydrogen pipes and the ease of ventil any leaks/boil off
RISE has shown multiple positions but nothing pusher.
It needs to be on a Pylon as it also has a jet exhaust though I have not seen how much that contribute to the push vs a Turbo Jet.
A rear mount tractor is possible but you have the weight penalty.
Also keep in mind, this is 35k of thrust not the 3000 or so from a DC-7/Connie prop job.
The demise of LCA piston aircraft was the failure to be able to put a light, reliable and low maint engine on a wing.
And last but not least, severe noise and vibration issues in the cabin. The industry abandoned propellers years ago. WTF???
The reliability numbers and Time on Wing of the CFM56 was reached after 40 years of continuous monitoring and improvements. Not by disruptive innovation pulled forward.
Airlines are very demanding & indeed take CFM/V2500 and other mature engines as reference. While gaining industry support for a new project, funding of the BOD, over-promising proves to work. People want to believe its going to be fantastic, while their techies know there’ll be a maturation period.
Build lots of prototypes, pre-production engines and fly / test the hell out of them, 10 thousand cycles under realistic circumstances, take them apart for detailed inspections, adjustments, is the way to reach high reliability. That means high costs and long lead times. Less enthusiasm from everybody for those..
But necessary to achieve the reliability the sales team promise.
I forget who the quote is from
Give Me Anything but Time!
There are 8000 hours in a year. You want to get 40,000 hours? 5 years constant testing on ONE engine.
I do believe its a huge mistake that does not certify a production standard engine.
That is why the GenX shucked its blades (a coating change in a shift to quantity production aka Industrialization) . GP7000 that found and enbritlement problem that no one had seen before. RR900 that in production had an oil manifold out of tolerance that cause the Qantas near crash.
Or, you make a fix and you insert it into in service engine as P&W found out and its vastly worse (seal).
Somewhere in that is also all the delays and no new aircraft.
I am not saying you are wrong, its just how do you balance progress and engine issues?
Mitsubishi proved the opposite side of the spectrum. In the pursuit of a perfect product (or as close as you will find) like you would in the automotive world, they dithered so long in development that ultimately the aircraft failed.
There were a lot of other reasons the MRJ failed to certify, but at a certain point you have to accept that the EIS product you have is not perfect and that it will take a measure of time to build in that durability maturity. Safety is key Day 1…durability not as much.
Their mistake was to not take on a development partner who was experienced in both building RJ airliners and cert expertise.
Win Win if they joined with Bombardier ( whom they already built the wings for Global Express ) and Mitsubishi could have been a minor partner on the Cseries. As Cseries was well ahead in timeline , the MHI cash for say a 15% share would have been very welcome.
I agree with Duke.
They tried to invent the wheel when they had never built a wheel in modern times.
Their days of building any aircraft were well behind them
I don’t know about you, but as an airline passenger, I have no interest in going back 70 years to save a bit of jet fuel. With mature engine designs suffering continuous reliability setbacks, I shudder to think what this silly design would do to the airline industry.
“Neither CEO addressed the obvious: without a qualifying engine, neither Airbus nor Boeing can launch a new airplane product.”
Can Boeing really afford to wait for the Open Fan when developing their new single aisle? An EIS of 2035 at best seems a bit far out into the future for them, the 737 will be a very old design by then (it’s already too old).
Or will they need to use a more conventional engine design to start with and then transition over to the Open Fan when it becomes available?
That is one of the issues. Its going to be unique mounting and a very different wing at best to deal with it.
Contrast that to a P&W GTF that they can get another 10% improvement out of.
It would not be a tech insert, some key stuff would have to change. So a new engine with all the lessons learned.
No question to me they would do it without the prior issues. But then you won’t to a TP (and the Rise is a TP Variation).
Its more conservative and would get you all that RISE could because no matter what they do, lessons learned mean tech insert down the road and its another 5-10 years before you get there.
In the meantime the GTF is returning SFC now and it too will improve as they refine the next version.
Reality is that issues on new ops are a fact of life, there is a reason the CFM and V2500 are so good, lots and lots of years of improvements.
It is a hard decision. There is a market for a short range cheap 300-400 pax widebody for domestic US/EU/China ops but there is no suitable engine for it and if Airbus does not design something similar the engine makers will not move. JetZero is trying for a 250pax Z5 and plan to use A321neo engines but with over wing installation requiring a special version of the engines, mountings and nacelles, for a new company it will be hard to pay for it unless Uncle Sam select and pay for it as a stealth tanker with a complete redesign to meet all USAF war time operations spec’s.
Maybe this is the way CEO’s talk, but …. I didn’t hear an explanation of why, exactly, recent engine introductions had poor reliability, or how, exactly, they plan to improve reliability.
I’m glad CEOs are listening to customers. That’s good. @keesje’s suggestions seem reasonable to me. I’d be more reassured if I heard something specific from CEOs that would improve reliability.
There are three things that airlines look for in reality. Fuel burn, fuel burn and fuel burn. If there is room for a fourth…it’s fuel burn. All while making engines as light as conceivable.
What this means is engines burning at increasingly higher temperatures while any ounce of design margin (part thickness) is designed out. Turbine blades and combustor distress are leading the removals. These are parts that sometimes takes multiple attempts to find one that is ultimately workable. Another consideration…these final exotic designs cost a lot more to manufacture.
New engines tend to be heavier.
They can be…really depends on what is going on with the stage count. CFM gained a turbine stage. PW dropped some stages. Obviously there is a trade-off involved.
And being heavier it makes it all the more critical that you extract as much excess weight out of the engine you can and not have it break.
Yes it is really hard to make a very durable, light weight fuel efficient engine. So mass trends up for higher thrust engines. Trent XWB Dry weight 7,277 kg , T1000 Dry weight 5,936–6,120 kg, RB211-524 B/C/D Dry weight 4,990–5,080 kg. CF6-80C2 4,300–4,470 kg GEnX-1B 6,147 kg.
The LEAP program had 18 test engines still got into early removals/modifications, So a “desert run” doing Max T-O thrust desert operations with 20-30 cycles per day/aircraft will quicker show problems, still to reach 2500flights is 80-100 days of intense flying of the same engines, you can increase the fleet of “desert Rats” by more aircrafts with updated engines joining the test program. Sir T. Clark want something similar with his ordered 777-9’s.
Don’t you think that nowadays they want reliability and low maintenance costs as well as improved fuel burn?
Most airlines sign up for hourly contracts so it’s really the OEMs who eat the maintenance cost risk. What airlines really want is to not have their aircraft AOG
A world flush with spare engines would placate most concerns
Airlines want all of the above and for good reasons.
Spare parts can alleviate the pain somewhat but you still have an AOG until that spare part is replaced and where it is in the engine?
You may or may not have a spare aircraft. If not its still a AOG and a delay.
And spare parts cost a lot of money and they have to be stored and tracked. A central location (or several) works far better but they are not where you need them when you need them.
A military maritime surveillance aircraft funded by government as they are could provide an airline like airframe suitable to the engine and provide a tough test environment that is not strictly commercial. Small numbers spreading across many operators as the programme develops would add a lot of operating experience with effectively no public risk – except the government money.
The Boeing B787 programme showed what can go wrong when technology is rushed into operation to grab a market. Three years of catch up just to solve the major flaws and a financial hole too big to cover, plus maybe a hundred airframes variously overweight as much as 7 tonnes. Broken promises means broken trust which like a porcelain vase, once broken will always be broken.
Fuel costs and environmental demands are for sure major factors but never discount the on-going costs of maintenance, repair and overhaul. Its why piston engines had to go for large aircraft – the MRO costs were prohibitive and as limiting as the technology.
Peter:
Engines on the 787 was generally reliable (until the RR1000 began its corrosion and then blade cracks 5 Years into service.
The SFC was not, so they corrected thtt with PIPs (or GE did and exceeded it ). RR came out with a new engine that still does not match GE (I believe it got to the spec RR agreed to)
Hi Transworld. I was referring to the whole aircraft project (the engines were the least of the problems) which Boeing people sold well ahead of theor ability to produce it. Fixing aircraft after service entry is a must BUT the airlines will only suffer so much pain and still believe the end of them is not long coming.
100 airframes to meet contract weigh along with all the other issue that appeared all through the early years of the B787 once, some three years late, it actually began to operate with airlines.
Airline executives were falling over themselves to buy or commit to the Plastic Fantastic which effectively blocked Airbus from sales as was the intent. Until it became obvious that 1, Boeing could not even produce it until three years later than claimed, and 2. It was likely not to meet performance guarantees for a good while into producion numbers and 3. It was not a mature trouble free aircraft and would not be for a good many more years. The B787-9 is a vastly better aircraft than the first generation which was over-hyped and under tested before EIS – late and rushed is another way of saying it
I think the 787 was a reaction to the A330’s. A330s became mature, CASM, range (-200), (cargo) capacity really became convincing and legacy’s started ordering them in numbers. Right inbetween the 767 and 777 markets, the A330-200s often for opening up Asian markets.
Airbus delivered 1000 A330s in the 2003-2015 period. Boeing saw it coming and launched the 787 to beat it.
IMO in the post 9-11 era there also was a patriotic atmosphere to recover, show ‘m how its done, that proved overambitious. Now the 787-9 is best in class, but it took a decade, not the 4 years promised.
The basic problem was the 787 was done mid liquidation.
So they did the Condit thing, something for nothing and cheap.
The tech has done amazingly well. Clearly not perfect but for a jump (s) like that it was impresive.
The failure was management who scattered production of pieces all over the globe doing risk sharing and thinking they could get away with it. Worst for a seriously new tech aircraft.
It fell flat on its face as we know. But cheap always will as well as something for nothing. Boeing’s claim was they only had low billions invested. You don’t do new tech and an unproven system at the same time. Tech is hard enough.
The A330 was selling decently, but Boeing failed right when they should have supplied the 787s and airlines bought A330 in droves as it was the height of the wide body bubble.
The A330 is well regarded, but the 787 failure is what made it a major success.
“Engines on the 787 was generally reliable …”
Ah, the GE-Bloomberg fairy tales
The alternative media covered all the issues where GEnX major modules have had to be replaced with a new designs
A report around 2016 mentioned 22 incidences of inflight engine failures
just one of the issues
https://www.industryweek.com/operations/quality/article/21972506/ge-engines-on-boeing-dreamliners-must-be-repaired-says-faa
https://www.abc.net.au/news/2016-08-09/jetstar-asks-manufacturer-to-explain-new-engine-problems/7703540
It was spun through GEs tame business news service multiple times as a ‘durability upgrade’ done as backfitting!!
https://www.ainonline.com/aviation-news/air-transport/2018-07-12/ge-delivering-new-genx-durability-upgrade
What airlines are going to risk a Prop Job?
You can wrap the RISE in a very pretty Bow, but its a prop the the public nor the jet using airlines like props jobs.
Even if you are convinced RISE is the next best thing since sliced bread, you don’t dare go there because you have customers who will refuse it and in numbers.
A TTBW will get a bit of a stink eye but over time of presentation and testing, I believe it would be accepted.
A prop job? nope.
It was a big ask for the jumbo jets for the public to accept double aisles with a centre block of seats far from the windows.
Annie Anxiety got over something different soon enough
These days many board through an air bridge and dont even see the wings let along the engines.
Remember planes builders are business-business, they dont have to wow the public who are more interested in seat space and on time service
“public does not like props”
This may be more of an injected protective folklore thing
as the US manufacturers don’t offer competitive prop types
than real public feelings. It is a US thing only.
( see also Twins are per definition better than Quads )
there are a number of reasons, passenger preference among them, that turboprops have almost disappeared from the american market.
stage length – typical american stage lengths are long enough that the flight time difference can be significant.
traffic volume – air travel volume, even on relatively sparse markets in the Us is quite high
network tailoring/abandonment of low revenue/low traffic routes/route consolidation – airlines have simplified their networks and abandoned many low traffic routes.
for instance, my wife’s home town in rural north dakota used to have daily commercial turboprop service (mostly 19 seaters) from MSP, FGO, GFK, JMS, BIS and DEN with 3 different airlines, some with multiple flights. today they have once daily large regional jet to Denver.
Northwest used to fly to 19-40 seat turboprops to GFK 10 times a day from MSP, now it is twice a day 737s
2 pilots is too expensive for turboprops today. Once pilotless aircrafts are certified they will be back. (Digital pilots in ATC and aircraft manufaturers computers sending correction commands to pre-programmed routes)
More complex than just pilots pay , who dont get paid the same as a 150 seater anyway.
US hub airports are overloaded during the peak periods. A 50 seater used the same ATC control space( because its slower its more) – taxiway space and ramp space as a 150 seater
The airlines have limited slots at their hubs , the CEO is screaming grow our revenue and hold down the costs…..whats going to give . The puny guy always gets beaten up
“Once pilotless airliners “….is pretty much a fantasy as its impossible to certify
Ah yes, the red tail Saabs. Everybody hated them, because of the cramped cabins, luggage limitations & noise. Now they miss them..
https://www.airhistory.net/photo/676148/N119XJ
The high days of the northern hubs in Detroit and MSP. NWA colleagues used to say about the market “it’s dark, it’s cold, but it ours.” They had good coverage / loyalty from smaller communities.
Remember when the SAABs 340 were used by the majority of Regionals in the 80s and early 90s. AA ordered hundreds of them when they started standardizing aircraft for their then new A Eagle franchise. 30 pax, stand up cabin and pressurized. It was better than the 19 pax aircraft many of them replaced.
I flew on so many TPs back in the day, scariest one was flying into panama city florida during a microburst thunderstorm. pilots should have diverted away to Ft Walton or just orbited outside the stormcell for 20 minutes, but dammit, they had dinner reservations they were not gonna miss.
most terrifying 15 minutes of my life. woman sitting next to me was in full blown panic, screaming and crying. massive upsets, updrafts, downdrafts, things in the cabin flying out of people’s laps.
The sales numbers of props (ATRs) in the US don’t lie.
The sales of Turbo Props in the regional sector they are economical at tells the story.
Boeing has a backlog of 4-5000 MAX despite the issues. Airbus is swamped until 2035.
ATR is building a paltry 60 a year and only that because the Dash 8 is not in production. Still its a market of 60 a year.
Who does not like Prop jobs?
As I have stated many time though most will not get it, you have to live it.
Alaska is the largest aircr5aft happy place on the planet. By far the highest number of aircraft and they are vast majority prop jobs.
You get into and out of Bush Alaska mostly on prop aircraft. Its a way of life.
AK tried to impose a Dash 8 on one of the main city routes (Fairbanks of 30k to Anchorage of 300K). People hated it and complained vociferously. Well before AK went all E175, they were forced to put them on the ANC to FAI route.
Alaskans will fly prop jobs, but they want jets if they can get them.
ANC to FAI is 350 miles or so, perfect TP route. Nope.
If it does not fly in AK it is not going to fly in the rest of the world. Anyone will take a jet over a Prop and all you have to do is offer a Jet vs a prop and your prop route is sunk.
People in the rest of the world will fly a prop job if they have to, but they want a jet at the next decent size town.
And as an Airline, are you going to risk it?
This is not the wide aisle comparison. That was a modern jet aircraft and people had no issues flying it. Props? not so much.
The Electra failed miserably, because of cabin noise and vibration. Certainly the accidents didn’t help. When Douglas introduced the DC-9, the party was over.
Remember, “Manufacturers who don’t study history are doomed to repeat it.”
Cannot have same numbers for reduction in fuel burn, and increase in fuel efficiency.
Both 20% increase in fuel efficiency and 20% reduction in fuel consumption appear in the text. Gotta choose one of them. Same numbers for increase and reduction is wrong.
A quick “radical” example to make this clear: 50% reduction in fuel consumption implies a 1 / 0.50 = 2.00, 100% increase in fuel efficiency.
https://www.flightglobal.com/engines/airbus-sees-no-rise-surprises-after-early-testing-as-study-highlights-installation-challenges/159906.article
Although an open-rotor engine promises what Haselbach calls a “massive step in propulsive efficiency”, it also presents significant integration hurdles.
Haselbach, speaking in a CFM-produced video this summer, points to “challenges” including internal and external noise and vibration, and protecting against fan-blade release.
“It is a step-change for the aviation industry to integrate such a motor into a potential new product,” he says, noting that “the aerodynamics of the wing will be challenged a bit by this”.
A recent study by the DLR bears out those concerns. Using a “generic” open-rotor design provided by CFM partner company Safran and a notional Airbus airframe – with a low-wing, high-aspect-ratio configuration – researchers conducted numerical analysis of the simulated installation impact of an open-rotor engine in take-off conditions, assuming an angle-of-attack of around 7°.
The study, conducted as part of the EU’s Clean Sky 2 programme and presented at the AAIA Aviation Forum in July, says “notable angle-of-attack and installation effects were found to effect the aerodynamic performance of both the propulsion system and the airframe”.
These include degraded performance of the swirl recovery vanes (SRVs) – the stator stage aft of the fan – and the generation of “substantial in-plane forces”, also known as 1P-loads, by the rotor and stator, which induce a tendency to make the aircraft roll.
Additionally, the direction of rotor rotation was found to have another impact: affecting the magnitude of the rolling moment caused by the interaction between the propulsor slipstream and the wing and flap.
A rotor spinning with its blades on a downward path when closest to the fuselage was found to create a larger rotational moment, the study found.
“In the interest of ensuring good overall aircraft handling qualities, as well as to avoid the need to trim out the rolling moment these in-plane loads cause, an aerodynamically symmetric aircraft would clearly be preferable, which would mean engines with an opposing sense of rotor rotation on the left and right wing,” the study says.