GE Aviation’s future fighter engine TECHNOLOGY XA100

GE Aviation’s future fighter engine TECHNOLOGY XA100 [FOUR PAGE PDF of Article attached below]
April 2019 Chris Kjelgaard

"Completion by GE Aviation of the detailed design process for its adaptive-cycle fan engine signals a switch from technology development to ensuring manufacturing readiness, reports Chris Kjelgaard...

...In completing the detailed design of the XA100, according to Tweedie, the company has moved on to a new phase of development from the primary technology-development effort in which it has been involved for the past 12 years to design and mature a variable-cycle fighter engine based on an adaptive-cycle fan design. Its XA100 design having been approved by the US Air Force, GE has now embarked on the final push to complete Phase 1 of the two-phase AETP programme. This push represents the final maturation of adaptive-cycle fan engine development to the point where an XA100-sized engine can be placed quickly—and with very little technological and design risk—into volume production if required, said Tweedie....

...Along with Pratt & Whitney’s XA101 variable-cycle engine, GE Aviation’s XA100 is one of two adaptive-cycle fan engine designs competing for what may eventually be a decision by the US Air Force to order just one variable-cycle fighter-engine design into production based on the service’s findings from AETP Phase 1. In 2016, the AFLCMC awarded each of the two companies a $1 billion, five-year R&D contract under AETP Phase 1 so the US Air Force could choose a potential winner from the XA100 and XA101 and order it into production during the first half of the 2020s.

As finally became clear publicly in mid-2018, the US Air Force specifically had in mind a potential decision to re-engine the Lockheed F-35 from about 2025 onwards, partly as a result of the known thermal-management challenges the F-35 has today in combination with its existing F135 engine. To that end, the AFLCMC specified that not only must the XA100 and XA101 fit the space within the F-35 that the F135 occupies today, but it also required the competitors’ variable-cycle engines to demonstrate a 10% maximum thrust increase over the F135, along with a 25% fuel-efficiency improvement and the capability to give the F-35 a 20% range increase.

Also specified, but not in a manner relayed publicly, is that the AETP Phase 1 competitors must provide the F-35 with substantially, perhaps very dramatically, improved thermal management capabilities. Of necessity, those thermal-management capability improvements require that both AETP Phase 1 competitors work very closely with F-35 airframe manufacturer Lockheed Martin to integrate the airframe and its systems with the engine and its systems to an extremely high degree....

...Air Force thinking
Although the AETP R&D programme began in 2016 and specified an adaptive-cycle fan engine which was of the same dimensions as the F135 powering the F-35, the US Air Force and its two AETP contractors said at that time the specification merely served as a convenient reference point for GE Aviation and P&W to assist them in developing their respective AETP Phase 1 engines.

Indeed, each of the two contractors was allowed to inform the AFLCMC of its preference regarding the AETP engine’s physical size and reportedly each asked to be able to develop an F-35-compatible engine. Not until two years later did GE Aviation, in the person of then-GM advanced combat engines Dan McCormick, first confirm publicly—with the US Air Force’s permission—that the AFLCMC had deliberately specified the AETP Phase 1 engine so that it could potentially serve as an F135 replacement.

Asked by AIR International why the US Air Force took this course, Tweedie said it had not wanted at the time to focus public attention specifically on a potential re-engining of the F-35 because the service had believed strongly for years—and had said publicly—that it believed variable-cycle engines would be fundamentally important for all of its future fighter aircraft. When the AETD programme began in 2012, the US Congress had asked about the purpose of the programme and even then the US Air Force indicated it thought adaptive-cycle engines represented the future for all of its fighter types, according to Tweedie.

Before the AETP programme began in 2016, the service had indicated the 10% thrust-increase requirement and the 25% fuel-efficiency improvement “would be foundational for the Air Force to have superiority against adversaries,” Tweedie said. “Neither in words nor actions has the Air Force done or shown anything other than what it said then — this is the future for all our products.”...

...variable-cycle engine technology, which employs at least three airstreams to enhance performance and efficiency throughout the flight envelope, represents the future for military high performance engines, the US Air Force believes. “This is the foundation of a whole new family [of engines] that will mature over the coming decades,” until eventually it too matures to the point where further rapid performance improvement becomes extremely difficult, said Tweedie. “That thinking is what has driven a lot of this [variable-cycle engine R&D] and a lot of the [US] Air Force’s investment in this technology.”"

Source: AIR International APRIL 2019 Vol.96 No.4

I wonder whether either this 20% or earlier 30% range increase figures were made in error. Either one could make sense depending on what airspeeds and altitudes the peak efficiency figures are being reached at. Even if it is 20%, that could potentially mean greater loiter capability, or it could make the F-35 able to / better at supercruising, depending on how the 3rd stream is configured and sized, what regime the fan is optimised for, etc.

I wonder whether either this 20% or earlier 30% range increase figures were made in error. Either one could make sense depending on what airspeeds and altitudes the peak efficiency figures are being reached at. Even if it is 20%, that could potentially mean greater loiter capability, or it could make the F-35 able to / better at supercruising, depending on how the 3rd stream is configured and sized, what regime the fan is optimised for, etc.

I'm not sure about the phase 1 motors, but have seen figures like 20% thrust increase, 50% loiter increase, and 30 to 35% range increase, for proposed phase 2 motors.

Detailed Design Complete for GE’s Revolutionary Adaptive Fighter Engine [short & sweet artickle]
01 Mar 2019 Nick Zazulia

"GE Aviation has completed the detailed design process of its XA100 engine under the U.S. Air Force's Adaptive Engine Transition Program (AETP), the company announced Thursday. The latest development means that GE can send engineering drawings out to its supply chain to get engine parts manufactured, according to David Tweedie, general manager for advanced combat engines at GE.

In accordance with AETP requirements, the XA100 ramps up engine thrust by 10 percent while simultaneously improving fuel efficiency by 25 percent over what would typically be possible with a fighter jet engine. The key is XA100's variable cycle that allows for adjustment to the bypass ratio and fan pressure.

"Historically, the big turbofans have a much lower bypass ratio and a much higher fan pressure ratio, and that gives you very high specific thrust," Tweedie said. "For a given technology, you can either optimize for fuel efficiency or thrust depending on what you want the aircraft to do."

Traditionally, he said, militaries have lived with low fuel efficiency in fighters because range was not a major concern during combat. That has been changing in recent years, however. "What we've seen happen is, with where our adversaries are heading and the improvements in their standoff capabilities, nowadays range is a much more important part for ... fighters than has historically been the case," he said....

...Beyond the primary goal of maximizing both range and thrust, the XA100 allows for improved thermal management, which is becoming more important as more powerful aircraft systems generate more and more heat and exteriors are switched from aluminum to composite skins, which Tweedie said act like a Thermos.

According to Tweedie, the improved thermal management is accomplished through two main tactics. GE used more temperature-resistant ceramic matrix composites developed for its commercial engines and added a cool third stream that acts as a heat sink inside the engine. Most modern engines have two airstreams. Additive technology has changed the way that GE can design engines, Tweedie said....

...While the earlier Adaptive Versatile Engine Technology program was solely about scientific testing to prove out technology, AETP was based on applying that technology to an actual use case by choosing a platform with program requirements and proving that the adaptive engines could be developed under those restrictions and at a workable cost....

..."The most direct transition for this technology would be the F-35A," he said. "There's talk about spinning off the technology into upgrades for 4th-gen fighters, whether that’s F-15, F-16 or F-22 platforms, and certainly it's under considerations as we think about future platforms.”..."

Photo: "GE promotional materials showing the three air streams in the XA100 engine. (GE/AVI screenshot)" https://cdn.aviationtoday.com/wp-conten ... /xa100.png

Source: https://www.aviationtoday.com/2019/03/0 ... er-engine/

"ramps up engine thrust by 10 percent"

10% over what? GE's F136? The published F135 value of 42k? The 50k that P&W have actually run the F135 at?

The published value would be the number - is that the installed thrust also. Take the number from LM F-35 FAST FACTS?

Propulsion* (uninstalled thrust ratings) F135-PW-100 40,000 lb Max. 25,000 lb Mil. [why quibble? Be happy with numbers]

"ramps up engine thrust by 10 percent"

10% over what?

"the XA100 ramps up engine thrust by 10 percent while simultaneously improving fuel efficiency by 25 percent over what would typically be possible with a fighter jet engine"

The published value would be the number - is that the installed thrust also. Take the number from LM F-35 FAST FACTS?

Propulsion* (uninstalled thrust ratings) F135-PW-100 40,000 lb Max. 25,000 lb Mil. [why quibble? Be happy with numbers]

Most sources have it at 28k/43k.

So cite these sources. Why does it matter so much? What can you do about it? Until the NATOPS / Dash One Flight Manuals become available then the guessing will continue if you have different numbers (installed or uninstalled?). And so it goes.

So cite these sources. Why does it matter so much? What can you do about it? Until the NATOPS / Dash One Flight Manuals become available then the guessing will continue if you have different numbers (installed or uninstalled?). And so it goes.

Doesn’t matter considering they are uninstalled sea level bench test figures. Interestingly, some Pratt datasheets list all three at 43k lbs of thrust. Others like first below list the F135-PW-600 at 41k lbs of thrust. That’s what I recall too, limitations of the lift fan and roll posts to handle more. Then it’s been 8-9 years, who knows if my recollection is accurate.

http://filecache.mediaroom.com/mr5mr_pr ... _pcard.pdf
http://filecache.mediaroom.com/mr5mr_pr ... tfacts.pdf

Thanks for the 20 May 2016 noise P&W F135 facts 'fbw'. The 'noise' PDF cites: "...The F135 provides a maximum thrust of 43,000 lbs. for three F-35 variants..." whilst the other cited P&W PDF dated 27 Jun 2018 says: "...Maximum thrust class (CTOL/CV) 43,000 pounds (191.3 kN) Maximum thrust class (STOVL) 41,000 pounds (182.4 kN)…" which is not quite as precise I'll guess. Doubtless other 'dates' for the F135 info may say the same - or not. Why does LM state what it does? [No need to answer except if you represent LM for publishing these details]

Again though how is this helpful when viewing these figures via a computer screen? Sure it is good to have the 'rough figure' - whatever it is (personally I'm not bothered what it is) - however did not the good 'Chip' Berke tell us not to be comparing these figures with other aircraft? The F-22/F-35 are fifth gen operating in another sphere, being figured out?

There are threads about this topic of thrust & weight of the various engines also including the aircraft variants weight(s).

LONG post about F135 upgrades: viewtopic.php?f=56&t=27458&p=293358&hilit=installed+uninstalled#p293358 Jun 2015

The F135 Block Upgrade Plan [SIX PAGE PDF of entire article "Towards Tomorrow's US Fighter Engines" attached below]
Jun 2015 AIRinternational Chris Kjelgaard

"...During its original ground-testing effort for the F135, P&W ran an unimproved engine at thrust levels of up to 51,000lb in uninstalled configuration (ie. without any accessory gearboxes or drives drawing power from the engine). This suggested that, even on an installed basis, the F135 had several thousand pounds of additional thrust available if necessary, if run at high temperatures…."

Source: https://www.scribd.com/doc/269303020/AIR-US-NG

I wonder whether either this 20% or earlier 30% range increase figures were made in error. Either one could make sense depending on what airspeeds and altitudes the peak efficiency figures are being reached at. Even if it is 20%, that could potentially mean greater loiter capability, or it could make the F-35 able to / better at supercruising, depending on how the 3rd stream is configured and sized, what regime the fan is optimised for, etc.

I'm not sure about the phase 1 motors, but have seen figures like 20% thrust increase, 50% loiter increase, and 30 to 35% range increase, for proposed phase 2 motors.

Those are ginormous jumps in thrust, loiter and range. It's going to perform like a whole 'nother aircraft if they can even get close. Will go a long way toward tidying up the ability to super-cruise, how fast it can get from mach 1.2 to mach 1.6 (and likely beyond). And a 30-35% increase in range... perhaps the most meaningful metric, given our pivot toward the SCS.

The published value would be the number - is that the installed thrust also. Take the number from LM F-35 FAST FACTS?

Propulsion* (uninstalled thrust ratings) F135-PW-100 40,000 lb Max. 25,000 lb Mil. [why quibble? Be happy with numbers]

Okay, so who's "facts" are better? P&W says 43k (a 7.5% difference). I don't get all the hysteria about asking a simple question. It's like a few of you feel personally attacked that anybody would wonder exactly what GE meant.

Who has hysteria? Now we have numbers for 'class', 'installed', 'uninstalled' and 'no qualifier'. Then we have the 'test number' uninstalled at high temperatures (not used in F-35) without other equipment NOT taking power from engine. One would assume that 'uninstalled' means no equipment taking power from the engine? 'TEG' answered that somewhere here.

Who has hysteria? Now we have numbers for 'class', 'installed', 'uninstalled' and 'no qualifier'. Then we have the 'test number' uninstalled at high temperatures (not used in F-35) without other equipment NOT taking power from engine. One would assume that 'uninstalled' means no equipment taking power from the engine? 'TEG' answered that somewhere here.

One would assume that, special circumstances aside, published values by the engine maker would be on a bench. That they're almost universally "bench" (test stand) values. So when GE claims a 10% improvement without saying over what it's a useless statement.