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Will F-35 Get New AETD Engine?

Flyaway

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Now the other shoe drops.

Now we know why. At a Monday briefing here, the head of Pratt’s F135 program, Mark Buongiorno, told reporters the company didn’t want to release the information because the Adaptive Engine Technology Development (AETD) program’s engines were being tested for dimensions that matched those of the F-35. A more fuel-efficient AETD engine could overcome one of the longstanding concerns about the F-35 in an era of ever deeper anti-access/area denial defenses, its relatively short unrefueled range of a bit more than 600 nautical miles.

Then General Electric put out a release late yesterday about testing for its Adaptive Versatile Engine Technology (ADVENT) project, which achieved the highest combined compressor and turbine temperature operation “in the history of jet engine propulsion.” That release included this sentence: “It is now being applied to the next step – an engine that could fit an F-35-like aircraft.”
http://breakingdefense.com/2015/06/ge-sets-aetd-record/
 

sferrin

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Repost:

http://www.secretprojects.co.uk/forum/index.php/topic,22564.msg252396.html#msg252396
 

Steve Pace

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Sounds like a great propulsive system for the upcoming LRSB too. -SP
 

sferrin

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Steve Pace said:
Sounds like a great propulsive system for the upcoming LRSB too. -SP
I thought the bomber was getting a different one. (Higher bypass for better subsonic efficiency, and I also thought it was suppose to have significant electrical power generation built into it.) As for the F-35 getting it it's already been stated in AvWeek, by GE as I recall, that this engine is too big to fit. There is enough inlet capacity but the third stream (the fat part in the middle) takes too much space without doing significant modifications. Lose the 3rd stream, there goes your superior efficiency, do the mods to the plane and the cost explodes and there goes any interchangeability.
 

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Pratt and Whitney is likewise developing an AETD engine - can't wait to see what it can do. I for one do not think the GE AETD engine is slated for F-35 use - there's too many P&W F135 lovers in the F-35 program to allow it. -SP
 

sferrin

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Steve Pace said:
Pratt and Whitney is likewise developing an AETD engine - can't wait to see what it can do. I for one do not think the GE AETD engine is slated for F-35 use - there's too many P&W F135 lovers in the F-35 program to allow it. -SP
Personally I think it would be a waste of money. The F135 is working fine. 15-20 years down the road? Who knows. At this point it would be a needless expense, increase in complexity ($$$$$), etc. I think some people mistakenly think this is an F136.
 

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sferrin said:
Steve Pace said:
Pratt and Whitney is likewise developing an AETD engine - can't wait to see what it can do. I for one do not think the GE AETD engine is slated for F-35 use - there's too many P&W F135 lovers in the F-35 program to allow it. -SP
Personally I think it would be a waste of money. The F135 is working fine. 15-20 years down the road? Who knows. At this point it would be a needless expense, increase in complexity ($$$$$), etc. I think some people mistakenly think this is an F136.
It's not the F136 as you say - and I agree about wasted $ for the F-35 program. Best leave well enough alone. -SP
 

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The issue at hand is that the current engine is limited in its ability to provide cooling for all the electronics and other systems that are in the craft. This is reducing the growth capacity for the plane. As for the timeline, these engine programs take many years to develop. There is no doubt that the AETD engine as well as a few other programs that are out there are targeting the F-35.
 

sferrin

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Aeroengineer1 said:
The issue at hand is that the current engine is limited in its ability to provide cooling for all the electronics and other systems that are in the craft. This is reducing the growth capacity for the plane. As for the timeline, these engine programs take many years to develop. There is no doubt that the AETD engine as well as a few other programs that are out there are targeting the F-35.
And how would the AETD be able to help there when the thing that makes it able to offload more heat (the 3rd stream) also makes the engine too big to fit in the plane?
 

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What else can use a 45,000 class engine? From what I can tell a single engined F-22 replacement with 45K of thrust is rather unlikely. A 45,000 thrust class, single engine F-18E/F replacement or a Super Lightning may be something that the USN looks at but it would most likely want a twin engined aircraft. A 2 x 45,000 lb class fighter also looks rather unlikely unless we develop a freaking supersonic mothership :).

So what else is going to use a 45,000 lb class engine? If i were to guess I would guess that since the AETD is not a full fledged EMD program, they are leaving an option out over the next 10 or so years to launch a new engine program for the F-35 based off of the AETD program. The current plan calls for a transition into an AETP program next year that will mature technology for an EMD phase for a totally new engine. That engine need not be in the 45K thrust class but the AETD and AETP programs will give different options by both maturing adaptive engine technology, CMC's and other materials, and by producing a prototype test engine in the F-35 class (Size and thrust) so that various options are available for future leadership given what comes out of the Air Dominance Initiative.

I don't think either the AETD or AETP are likely to fly although I could be wrong on that.
 

sferrin

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F/X and F/A-XX would both be twins with engines of that class. The F414 is getting long in tooth and if you're going to go single-engine you may as well buy more F-35s. It also depends on what the engine cycle is like. Is it like an F119 or more like an F135? The USAF wants a large, long-range supercruiser. Think XF-108 but stealthy, not Mach 3 capable, and with more maneuverability (though not F-22 class). The USN wants. . .well, something like more efficient, stealthy F-15E.
 

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Lockheed has claimed that it has offered two designs, one a clean sheet and the other a lower risk F-35 based proposal. Regardless of what the fighter looks like the engine in the 45,000 class is too big and powerful for a twin and is pretty much suited only for the F-35 or a classified program (perhaps the bomber? Would a 2 x 30K dry be enough?) unless the twin engine fighter with 90K of thrust looks like a bomber :). That when put together with the fact that Colin clark reported on regarding the dimensions also being in the JSF class seems to strongly indicate that although the AETD is not an EMD engine, it could once completed (along with its follow on transition program) be an option to compete a new engine for the F-35 perhaps a decade down the road (from 2018). That to me is the only logical explanation for choosing a 45,000 pound thrust class engine for the demonstration program.
 

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Aeroengineer1 said:
The issue at hand is that the current engine is limited in its ability to provide cooling for all the electronics and other systems that are in the craft. This is reducing the growth capacity for the plane.

Many of the key systems on the F-35 are actually liquid cooled therefore how is this supposedly a limit of the engine?
 

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https://www.youtube.com/watch?v=SSC3b6xiSw0
 

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The F135 Block Upgrade Plan

Under the F135 Block Upgrade Plan, a series of initial ‘Block 1’ improvements might potentially be available for new-production examples and for retrofit into existing ones from as early as 2018. Then a second series of AETD project-derived, more substantial ‘Block 2’ improvements could be put “into production in the very early 2020s”, depending on “funding and the requirement pool”, according to Kenyon.Although Kenyon points out this plan is “not part of the F135 programme proper”,
he said “it is an opportunity looking ahead to demonstrate fuel-burn cost savings” to F-35 operators – and particularly to the US Navy, with which P&W is working to try to get the Block 1 F135 upgrades into production within the next few years.

The Block 1 upgrades rely partly on development work that P&W carried out for a demonstration in autumn 2013 for the navy’s XTE68-LF1 project. This focused on demonstrating a capability for higher operating temperatures in the F135’s turbine and introduced a variety of new technologies into the engine’s high-pressure turbine (HPT) module. These improvements, which Kenyon described as “advanced cooling technologies”, included new casting technologies for metal- alloy parts; new, highly temperature-resistant HPT materials; new thermal barrier coatings for HPT blades and vanes; more temperature- resistant oils for lubricating and cooling; and a new main shaft bearing. He said P&W’s XTE68-LF1 demonstration in autumn 2013 was “tremendously successful” – so successful that it recorded “the hottest-ever temperature in a production engine”.
P&W has parlayed this successful demonstration into another F135 development initiative on which it is working with the US Navy, called the Fuel Burn Reduction (FBR)programme.

FBR has married the HPT technologies from the XTE68-LF1 demonstration with a series of improvements to the F135’s six-stage, all-blisk compressor to produce an engine offering a fuel-burn reduction of “about 5% – and we’ve identified another couple of opportunities to give [another] 1%-2% of fuel-burn improvement”, said Kenyon. However, saying the XTE68-LF1 and FBR technologies would just reduce fuel burn only in production F135s would be inaccurate: the technologies would also offer other improvements. “TheJPO(F-35Joint Programme Office) and navy are both focused on [engine] life-cycle cost and they need to have the technology working reliably,” said Kenyon. An important feature of the XTE68-LF1 and FBR advanced cooling technologies is that “you need less air to do the cooling [in the HPT] and you can use it more to do other things, with the cooling capability already in the engine. We’re using low-lying fruit to get better thermal management,” he said.

“Right now I’m going to insert this nice cooling technology into my turbine because it helps with [life-cycle] cost [by making the engine more durable], but I could use it to generate more thrust” – perhaps up to 10% more, making the F135 capable of meeting any foreseeable F-35 thrust-growth requirement.

There is no doubt about this. 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.

Kenyon pointed out that, although the F-35 airframe has had heat-retention issues, “right now, there are no thermal restrictions with the engine”. In-service F135s are operating within the specifications required by the JPO and presumably could be operated at a higher maximum temperature as long as the F-35 airframe could withstand and dump the additional heat burden.

F135 Block Upgrade
Programme: Block 2


Pratt & Whitney’s proposed Block 2 upgrades for the F135 would be more complex than those in Block 1. The manufacturer can see a potential path by which it could introduce into the F135 engine, for production from the early 2020s, some of the advanced technologies it has developed for the compressor and turbine in its high-pressure AETD core.
The F135 has the same dimensions as the AETD demonstrator upon which P&W is now working. But while that is a three-stream engine, at this juncture P&W does not view redesigning the F135 into a three-stream, adaptive-cycle engine – which may be theoretically possible.


However, Kenyon said there is an “exciting opportunity we’ve identified, which is unique to Pratt & Whitney’s position, to take some of the key technologies of the three-stream AETD architecture into the F135 to get lots of benefits”.
This opportunity could rely on a potential evolution of the company’s engine-control software for its AETD demonstrator.
Kenyon said: “For example, if you can modulate the [existing] bleed air using the three-stream control laws, rather than using an actual third stream of air,” this could produce substantial benefits from an enhanced capability to use cooling air flexibly at different places in the engine’s hot section. “The trade is really around the re-use of current learning,” he said.
In addition to incorporating a series of AETD- derived hardware and software upgrades, as well as other cooling and design technologies,a future Block 2 upgrade of the F135 might also incorporate the improvements already provided under Block 1. P&W isn’t sure yet of the scale of the fuel-burn reduction and thrust increase a Block 2 upgrade would offer, but they would certainly be more substantial than those provided in Block 1. It’s possible Block 2 modifications could produce benefits even greater than the AFRL’s AETD project targets of a 25% fuel-burn improvement and 10% thrust increase over today’s F135 engine.
The future of adaptive-cycle engines for US fighters, and even the future development of the existing F135, relies greatly upon Congress approving President Obama’s AETP budget request. If approval comes at all, it will likely come this year. Pratt & Whitney is now beginning to flesh out a two-pronged strategy to try to retain its dominant position in current- generation US fighters and win a prominent position on US next-generation fighters. It will hope Congressional approval for AETP is prompt and generous – and that the AFRL likes P&W’s AETD design.
https://www.scribd.com/doc/269303020/AIR-US-NG
 

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http://aviationweek.com/defense/f-35-production-hours-continue-shrink?NL=AW-19&Issue=AW-19_20150622_AW-19_462&sfvc4enews=42&cl=article_6&utm_rid=CPEN1000000230026&utm_campaign=2944&utm_medium=email&elq2=b178b1bb0189465e88c57cee28271a00

Pratt & Whitney says retrofits of the F135 engine to enable unlimited operations in the F-35 are happening faster than originally planned and are on track for completion by early 2016. “What a difference a year makes,” says F135 Senior Vice President Mark Buongiovno, referring to the program’s recovery from an engine failure in 2014 that not only badly damaged an F-35 but temporarily grounded the fleet and prevented the aircraft from making its international debut at last year’s Farnborough Airshow.

The engine maker is simultaneously executing an aggressive production ramp-up that will see output go from the current 60 engines per year to around 200 annually by 2020. The rate of engine builds is slightly higher than that of airframes to accommodate spares. “I want to deliver on my schedule, I want to deliver on my cost, I want to get production ramp-up and deliver on contract. I also want to make the introduction to the world fleet as seamless as possible,” Buongiovno says.

Part of the reason for Pratt’s optimism at Paris was the result of a recently completed accelerated mission test of a standard F135, which put the engine through 5,200 cycles, the equivalent of more than seven years of service, or around 1,200 combat missions. No turbine maintenance was required over the 10-month test, which validates the basic reliability of the design as well as identifies any potential issues before they crop up in service. “That gives us good confidence we will see that sort of life throughout the program,” he adds.
 

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To the previous two commenters asking about how the engine relates to cooling the rest of the aircraft systems, here is a link to a Flight Global story that discusses some of the early issues of the F135 and how they hand knock on effects to the thermal management of the entire aircraft as a system.

In short, the engine can provide cooling air through bleed off of the compressor stages. As the engine is also not a pure turbojet, but a low bypass turbofan, there is also opportunity to use some of the bypass air for cooling.

Here is another Flight Global story that talks of the need to pull bleed air to cool the aircraft systems.
 

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Aeroengineer1 said:
To the previous two commenters asking about how the engine relates to cooling the rest of the aircraft systems, here is a link to a Flight Global story that discusses some of the early issues of the F135 and how they hand knock on effects to the thermal management of the entire aircraft as a system.

Pulling an old story from 2006 is hardly adding anything to your earlier stated position that "The issue at hand is that the current engine is limited in its ability to provide cooling for all the electronics [my emphasis] and other systems that are in the craft. This is reducing the growth capacity for the plane."

Whilst there are some systems that are cooled by air within the F-35 they are actually not that great in quantity. As I previously mentioned, more are liquid cooled (either by fuel or PAO). Your earlier comment is therefore meaningless unless you can prove otherwise.
 

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GTX,

Perhaps I am reading the tone of your message incorrectly, but I can see that you did not read closely the posts provided and you are trying to extrapolate beyond what I was saying with "all electronics". Let's term this as a system in which the aircraft has so much ability to absorb heat as well as maintain signature. Air cooling is indeed the primary means of cooling for ALL the systems, even the systems that you are citing as being liquid cooled. Any liquid cooling is being used as a "heat pipe" if you will to remove the heat from the specific device and to distribute the heat around the aircraft and generally lower the IR signature. This is then cooled through the skins of the airframe and transferred to the air or another dedicated heat exchanger. Hence for the sake of being somewhat pedantic, though trying to be technically accurate, everything is truly air cooled.

There are other places besides the wing that this heat is exchanged. As I mentioned before, some of this is done through having skin coolers in the bypass air. Once again, these tend to be liquid/air heat exchangers, and the other way is through use of bleed air from various stages of the compressor. This air is usually precooled (as it can be in the 500-1500°F range) and then expanded. The expansion causes further cooling. Some of this air is used for pressurization and climate control, and other is used for systems cooling. Do note that I specifically mentioned that some of this cooling supplied from the engine would not only cool the electronics, but other systems as well (including the engine itself). The nozzle of the aircraft is one of these other systems.

Here is a more recent story from AvWeek specifically speaking to the AETD engine and the increased cooling. Here is a quote from that story:

The third stream — an additional flowpath outside the core and bypass duct — will be closed at takeoff for high thrust but opened in cruise to reduce fuel consumption and inlet spillage drag and increase cooling-air supply to the aircraft, engine and nozzle.

Also as a note, I do happen to work for GE Aviation. I am not on the AETD program, but we do get general information passed along about the program, and some of the things that are driving the customer towards its requirements. All the information that I have shared (and received for that matter) is publicly accessible.
 

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Here is another press release from Rolls Royce speaking on the ADVENT engine (one of the many engine programs that is playing into the AETD and what ever its next acronym will be here in the future). Quoted from their press release:

2. In August 2007, Rolls-Royce North American Technologies, Inc. was awarded a $296 million contract by the AFRL for work to develop ADVENT technologies that focus on an adaptive engine architecture to provide a 25 percent improvement in average fuel consumption and reduced temperature cooling air for thermal management. The ADVENT engine demonstrator testing is scheduled for 2013

I also found a few others by searching F-35 AETD Increased Cooling if you wish to continue to gain more information. I myself am off to bed.
 

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Aeroengineer1 said:
Air cooling is indeed the primary means of cooling for ALL the systems, even the systems that you are citing as being liquid cooled. Any liquid cooling is being used as a "heat pipe" if you will to remove the heat from the specific device and to distribute the heat around the aircraft and generally lower the IR signature. This is then cooled through the skins of the airframe and transferred to the air or another dedicated heat exchanger. Hence for the sake of being somewhat pedantic, though trying to be technically accurate, everything is truly air cooled.

Simply incorrect. Many of the F-35's systems are liquid cooled and dump their heat into the fuel system without any recourse to an air transfer system.
 

sferrin

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GTX said:
Aeroengineer1 said:
Air cooling is indeed the primary means of cooling for ALL the systems, even the systems that you are citing as being liquid cooled. Any liquid cooling is being used as a "heat pipe" if you will to remove the heat from the specific device and to distribute the heat around the aircraft and generally lower the IR signature. This is then cooled through the skins of the airframe and transferred to the air or another dedicated heat exchanger. Hence for the sake of being somewhat pedantic, though trying to be technically accurate, everything is truly air cooled.

Simply incorrect. Many of the F-35's systems are liquid cooled and dump their heat into the fuel system without any recourse to an air transfer system.
With the idea being to dump the warm/hot fuel through the engine and off the aircraft.
 

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There is also a heat exchanger that cools the fuel with inlet air.

Besides a backup heat exchanger located in the starboard wing root, there are 4 heat exchanges located in the inner circumference of the inlet ahead of the engine.





 

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Aeroengineer1 said:
The issue at hand is that the current engine is limited in its ability to provide cooling for all the electronics and other systems that are in the craft. This is reducing the growth capacity for the plane. As for the timeline, these engine programs take many years to develop. There is no doubt that the AETD engine as well as a few other programs that are out there are targeting the F-35.
Well no engine out there "provides cooling". They usually use an Air cycle machine and bleed air. The F135 "issue" was because designers hadn't anticipated people pumping 125 degree F fuel into the plane. Cooling challenges mostly exist between startup and cruise altitude. The air temps at cruise altitude are going to be ~20 degrees or less, making cooling much easier. So now they'll have to insulate their trucks, but the stuff coming out of the ground or stored on a carrier is going to be nice and cool already and will keep everything comfortable up to cruise altitude and beyond. 13,000 to 19,000 pounds of fuel makes a hell of a heat sink.
 

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The whole painting of the trucks (1 truck actually) was blow WAY out of proportion.
a spokesman for the base said that in a proactive measure to offset future potential problems,
"potential problem" = NOT currently a problem and current CONOPS do not show it to be a problem.


"This is not an F-35 issue; there are no special restrictions on the F-35 related to fuel temperature. The F-35 uses the same fuel as other military aircraft. It can fly under the same temperature conditions as any other advanced military aircraft," the Pentagon's F-35 Joint Program Office told CNBC.


...


So far, only one truck has been repainted. Whether the new paint solves the problem is still being determined. The idea has also been tested at Edwards Air Force Base in Southern California, another area where the heat hits triple digits, but Maj. Hasson said Edwards was doing a general test of the concept. It was not related to the F-35 specifically.
http://www.cnbc.com/id/102253195
 

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Since there are these things called the Laws of Thermodynamics, there are three things that any heat can do. it can be dispersed into the air, dumped out the back as combustion products that are hotter than they would otherwise be, or stick around and make the airplane hot.


Using fuel as a heat sink is limited by how fast you can get rid of hot fuel (depends on flight conditions) and how hot or otherwise the fuel is when it goes on board.


Early F-35 testing used fuel chillers. There was an acknowledged issue that was addressed with a more efficient fuel pump from LRIP 3 onwards, IIRC. The INVENT program has also stated that it is looking at stealth-aircraft thermal management issues.


Presumably, if you had an engine that could be adjusted to higher mass-flow, it could allow you to put bigger HXs in the bypass duct.
 

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Based on my understanding, it seems that the three-stream adaptive cycle engines of AETD is distinct from the double bypass used in the YF120. Perhaps YF120 was simply more supercruise-oriented?
 

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RadicalDisconnect said:
Based on my understanding, it seems that the three-stream adaptive cycle engines of AETD is distinct from the double bypass used in the YF120. Perhaps YF120 was simply more supercruise-oriented?
In the YF120 there were doors aft of the 3rd fan stage that could dump air back into the bypass duct, rather than going through the compressor. When those doors were closed the additional air went through the compressor.
 

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IIRC, the third fan stage on the F120 was driven by the core. That core-driven fan stage (CDFS) was a step in the evolution of the COPE (controlled overall pressure ratio engine) that led in turn to Advent and AETD.
 

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sferrin said:
Steve Pace said:
Pratt and Whitney is likewise developing an AETD engine - can't wait to see what it can do. I for one do not think the GE AETD engine is slated for F-35 use - there's too many P&W F135 lovers in the F-35 program to allow it. -SP
Personally I think it would be a waste of money. The F135 is working fine. 15-20 years down the road? Who knows. At this point it would be a needless expense, increase in complexity ($$$$$), etc. I think some people mistakenly think this is an F136.
I can't remember where I read it now (might even have been here), but I remember reading that they weren't given a requirement to spec the engine for so they built it week the F-35 in mind since there was no other fixed design that it could be for.
 

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Although GE initially aimed to size its AETD engine to suit the future U.S. Navy F/A-XX and Air Force F-X sixth-gen fighters, respectively, the precise thrust requirements for these remain “very rubbery,” says McCormick. With major questions unresolved—whether these will be one- or two-engine aircraft, for example—GE “defaulted to the F-35,” as the basis for its engine plan.
The AETP-based engine design “is more aggressive than today’s standard F-35 requirements but not to the level of [powering] directed energy weapons,” comments McCormick. Instead, the potential benefits of the third stream would be aimed at opening up the low-altitude/high-speed corner of the F-35’s flight envelope to enable extended operation at Mach 0.8/0.9 and 500 ft. “Today, the F-35 has flight restrictions at lower altitudes because of thermal management. You just can’t get heat off the airplane,” he adds. “The program we have laid out says you could be in the F-35 before mid-2020s. It depends on funding profiles and how big AETP is, but it’s early in the 2022-24.”
http://aviationweek.com/defense/ge-details-sixth-generation-adaptive-fighter-engine-plan
 

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So that looks like a stake in heart of any hopes for an easy upgrade. But there's still hope for an "F-35D" or some similar platform enhancement down the road featuring AETD.
 

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In the past GE (pretty sure it was GE) said the only way one of the ADVENT engines would fit in the F-35, without significant modifications to the engine bay, would be to lose the 3rd-stream on the engine.

As I recall, ADVENT was strictly a GE/DoD effort, with P&W pretty much doing their own thing, and now the ADVENT engine and P&W's engine are part of the AETD (AETP?) program. Could anybody provide a clearer picture of this? ???
 

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Moose said:
So that looks like a stake in heart of any hopes for an easy upgrade. But there's still hope for an "F-35D" or some similar platform enhancement down the road featuring AETD.
They wouldn't go as far as a new variant; while structural modifications are probable for an AETP engine, such mods would still fit under the scope of a Block upgrade.

sferrin said:
As I recall, ADVENT was strictly a GE/DoD effort, with P&W pretty much doing their own thing, and now the ADVENT engine and P&W's engine are part of the AETD (AETP?) program. Could anybody provide a clearer picture of this? ???
ADVENT was the early R&D program and only funded GE+RR. ADVENT then transformed into the AETD tech demo program in 2012, with both P&W and GE being funded to develop engines. Now in 2016, AETD is finished / being finished and transformed into AETP, which is an actual 5-year acquisition program. GE and P&W will be competing for a contract to develop the F-35's (and possibly B-21's) next engine (though P&W might squeeze in an F135 Block 1 interim upgrade).
 

sferrin

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Dragon029 said:
Moose said:
So that looks like a stake in heart of any hopes for an easy upgrade. But there's still hope for an "F-35D" or some similar platform enhancement down the road featuring AETD.
They wouldn't go as far as a new variant; while structural modifications are probable for an AETP engine, such mods would still fit under the scope of a Block upgrade.

sferrin said:
As I recall, ADVENT was strictly a GE/DoD effort, with P&W pretty much doing their own thing, and now the ADVENT engine and P&W's engine are part of the AETD (AETP?) program. Could anybody provide a clearer picture of this? ???
ADVENT was the early R&D program and only funded GE+RR. ADVENT then transformed into the AETD tech demo program in 2012, with both P&W and GE being funded to develop engines. Now in 2016, AETD is finished / being finished and transformed into AETP, which is an actual 5-year acquisition program. GE and P&W will be competing for a contract to develop the F-35's (and possibly B-21's) next engine (though P&W might squeeze in an F135 Block 1 interim upgrade).
Thanks! Where does GE's statement that a 3-stream ADVENT engine wouldn't fit into an F-35 without losing the 3rd stream, because it's too big to fit in the existing engine bay, fit into this equation? On the one hand they're talking about putting an AETP engine in the F-35 and on the other saying it won't fit. ???
 

bring_it_on

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As I recall, ADVENT was strictly a GE/DoD effort, with P&W pretty much doing their own thing, and now the ADVENT engine and P&W's engine are part of the AETD (AETP?) program. Could anybody provide a clearer picture of this? ???
ADVENT and AETD looked at the architecture, verifying the concept and developing the component level capability and AETD was larger in scope than the ADVENT. AETP transitions all that has been achieved through these two CRAD programs, and P&W's and GE's IRAD into an actual complete engine. P&W continued to develop and prepare for the eventual AETD program and invested heavily to make sure they were ready. Both them and GE are also planning to integrate other advances in technology to squeeze additional performance. GE's recent success with CMC is one example of that.

Here are a few lines from Guy Norris on the three related programs -

AETP is scheduled to run through 2019 with several tests of full engines; it follows the Adaptive Engine Technology Development (AETD) program that is helping prove the basic viability of the adaptive cycle. AETD, which is set to wrap up between now and early 2017 with a series of demonstrations by GE and Pratt, itself builds on Advent (Adaptive Versatile Engine Technology), the Air Force’s pioneering research effort into variable cycle architectures, three-stream flowpaths and adaptive fans, conducted from about 2007 on.
 

riggerrob

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With all that talk about fuel-cooling, how much of an advantage would it be to re-fuel the airplane with chilled go-juice just before take-off?
How much more of a hassle is it for ground crew to use two fuel trucks? The first truck off-loads ambient temperature fuel while the second truck delivers cooled fuel?
How many more calories in cool fuel because it has higher density?
How many more calories available to fuel-cool accessories?

To avoid over-loading the logistics train, let's limit the conversation to only cooled versions of jet fuel that are already in inventory (e.g. Jet A or JP4).
 

Dragon029

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sferrin said:
Thanks! Where does GE's statement that a 3-stream ADVENT engine wouldn't fit into an F-35 without losing the 3rd stream, because it's too big to fit in the existing engine bay, fit into this equation? On the one hand they're talking about putting an AETP engine in the F-35 and on the other saying it won't fit. ???
I think they were just talking about the ADVENT or AETD-specific design, but I don't see any reason they couldn't decrease the core diameter to fit the third stream. That said, doing so would obviously impact the thrust performance, but it's possible that the customers could be happy taking just the fuel-burn reductions and leaving thrust roughly where it is today. That said, P&W is talking about having the F-35 fuselage modified to accommodate a third stream, and I'm sure GE will be having similar talks as well soon.

riggerrob said:
With all that talk about fuel-cooling, how much of an advantage would it be to re-fuel the airplane with chilled go-juice just before take-off?
Very little; most of the restrictions regarding hot fuel are to do with energetic or temperature sensitive mission systems while on the ground or soon after take-off. If an F-35 takes off with fuel that's borderline too hot, in roughly the time it gets to altitude, that fuel will be sufficiently chilled to be in the green.

What I've read is that the main concern where using fuel as a heatsink + hot fuel could be a real issue is if an F-35 returns with little fuel to a FARP (where it's hot as hell and there's limited or no fuel refrigeration or shade, etc), performs a hot refuel (where the F-35's engine keeps running while it's refueled) with literally hot fuel and needs to get back into combat post-haste (eg; an alert launch is called to intercept an enemy that's snuck up on the FARP or something). Under that perfect storm, thermal management modes could potentially prevent the F-35 from being able to immediately engage.

So perhaps there'd be some use in having USMC MAGTFs acquire refrigerator carts systems to cool fuel if things get crazy, but I don't see 99.9% of operations being affected; apparently there hasn't been a single case of hot fuel causing a sortie to be dropped, but I don't think the above-mentioned scenario has been tested yet.
 

NeilChapman

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sferrin said:
In the past GE (pretty sure it was GE) said the only way one of the ADVENT engines would fit in the F-35, without significant modifications to the engine bay, would be to lose the 3rd-stream on the engine.

As I recall, ADVENT was strictly a GE/DoD effort, with P&W pretty much doing their own thing, and now the ADVENT engine and P&W's engine are part of the AETD (AETP?) program. Could anybody provide a clearer picture of this? ???
There will probably be a better explanation but this is the way I've understood it...

ADVENT - Variable cycle - optimized for multiple design points - 20k lb thrust class - thought to be for NGB
specifically...
1. 25% fuel savings - compared to early 2000 baseline engines.
2. maintaining constant engine flow with variable-fan-pressure ratios
3. new materials to handle heat
4. reduce temperatures of cooling air

GE & RR awarded -
2007 Phase 1 - explore concepts, develop and test critical components, and begin preliminary designs of an engine
2009 Phase 2 - continue component testing and integrate the developed technologies into a technology demonstrator engine.
Originally DoD was going to fund one manufacturer but decided to fund both.

- Just as an FYI, recall F136 development going on by GE/RR w/DoD Funding while GE/RR was also receiving funding for ADVENT Phases I & II. This "encouraged" P&E to develop an adaptive fan version of the F135 engine.

AETD - Adaptive Engine Technology Development program - Follow-on to ADVENT program
- ADVENT for NGB - smaller core, AETD, not specifically for NGB, larger core.
specifically...
1. 25% lower thrust-specific fuel consumption vs F135
2. 5% more military power - (dry power) vs F135
3. 10% higher maximum thrust vs F135
4. trade studies w/Boeing, LM and NG - prep AoA for PCA or other combat air systems.

GE & P&W awarded -
2012 - Focus was on F/A-XX and F-X. Larger than engine for F-35.

AETP - Adaptive Engine Transition Program - Five year program of tech buy-down to get to downselect for EMD (but perhaps they'll select both)
- GE & P&W both focusing on making AETD-tech (prob w/o 3rd stream) to work for F-35 as it's a difficult installation and F-35 engine upgrades are the "big win"
specifically...
1. design, develop, fabricate, and test multiple complete, flight-weight, centerline, 45,000-pound thrust-class adaptive engines

GE & P&W awarded -
2016 -
 
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