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GE YF120

RobertWL

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I'm curious about information regarding the YF120 Engine, I've looked over the Internet but haven't found a lot more then the basic information.. It was a competitor to the F119 in the ATF competition, it was canceled and thats all she wrote basically. I was hoping someone might be able to answer some questions and provide other insights to the engine. I understand that the YF120 was a variable-cycle powerplant, operating as a turbofan at low speeds, turbojet at high speeds.. how much of an advantage would this pose for an aircraft? And does anyone know of the thrust poteintal for it? I have a feeling that is mostly classified. Also, how much technology does the F136 Engine draw from the F120? Is it variable-cycle as well? If it'd been chosen, would it have offerered any serious advantages over the F119?

Beyond that, I'd appreciate anything else interesting.. I just find that it was a curious design and its unfortunate that I can't find more information. Sadly my local library is pretty.. slim on aviation books.. So, I come to this wonderful knowledgebase. :)

Anyway, I appreciate the help.

Thanks.
 

flateric

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RobertWL said:
I have a feeling that is mostly classified.

You are right about this.
I will see in the evening what I can share on F-120.
 

sferrin

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RobertWL said:
I'm curious about information regarding the YF120 Engine, I've looked over the Internet but haven't found a lot more then the basic information.. It was a competitor to the F119 in the ATF competition, it was canceled and thats all she wrote basically. I was hoping someone might be able to answer some questions and provide other insights to the engine. I understand that the YF120 was a variable-cycle powerplant, operating as a turbofan at low speeds, turbojet at high speeds.. how much of an advantage would this pose for an aircraft? And does anyone know of the thrust poteintal for it? I have a feeling that is mostly classified. Also, how much technology does the F136 Engine draw from the F120? Is it variable-cycle as well? If it'd been chosen, would it have offerered any serious advantages over the F119?

Beyond that, I'd appreciate anything else interesting.. I just find that it was a curious design and its unfortunate that I can't find more information. Sadly my local library is pretty.. slim on aviation books.. So, I come to this wonderful knowledgebase. :)

Anyway, I appreciate the help.

Thanks.

I read soemwhere that the F136 doesn't really take much from the F120. Certainly not to the degree the F135 is derived from the F119.
 

flateric

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Robert, before I'll dig in dusty magazines, you can get some useful info from these sources.

http://groups.google.ru/group/rec.aviation.military/browse_thread/thread/e67192daca9cefcc/e7ba68985a64c4f0?lnk=st&q=GE+F-120&rnum=2&hl=ru#e7ba68985a64c4f0
http://groups.google.ru/group/rec.aviation.military/browse_thread/thread/7dc1f495426c7f53/e5591b34a4b41428?lnk=st&q=GE+F-120&rnum=1&hl=ru#e5591b34a4b41428
http://www.nap.edu/html/tech_21st/pl3.htm

Schematic of a variable cycle engine picture courtesy GEAE is simplified cutaway of F-120 (I have more detailied at home, but again some classified components not shown).
 

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flateric

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Excerpt from beautiful book - excerpt must stimulate everyone at last go and buy this BEST book on ATF program history.
Advanced Tactical Fighter to F-22 Raptor: Origins of the 21st Century Air Dominance Fighter (AIAA Education)
by David C. Aronstein, Michael J. Hirschberg, Albert C. Piccirillo


"XF120
The initial definition of the General Electric GE37, which became the XF120, was focused on performance for the supercruise re¬quirement. The design was a counter-rotating variable cycle engine with a vaneless HPT-LPT interface designed at the minimum bypass
ratio.

A variable cycle was attained by controlling the variation of bypass ratio using a double bypass concept in concert with the core-driven fan stage. The engine operated in double bypass at low power to gain the specific fuel consumption (SFC) benefit of higher BPR; at high power it operated in single bypass (low BPR) to achieve high specific thrust. Fan-to-core pressure matching was achieved through a variable area bypass injector (VABI) just ahead of the augmentor. The VABI supplied required exhaust liner cooling air and in¬jected the remainder of bypass air back into the exhaust upstream of the throat area to maximize thrust potential. The engine was controlled by a three-channel FADEC.

The two-stage fan was of blisk construction ("bladed disk" equivalent to Pratt and Whitney's integrally bladed rotor design). The blades were low aspect ratio to meet performance requirements, giving low leading-edge stress and high tolerance for foreign object damage (FOD) and repair blending. The five-stage blisk compressor was begun by the core-driven fan stage. This "fan stage" was followed by the single bypass flow opening.

The double-dome annular combustor allowed for a short, efficient combustor section. The single high-pressure turbine stage was a high reaction design with exit swirl to match the single low-pressure turbine inlet needs. There were no stationary vanes between the turbine stages.

<skipped>

The XF120 testing validated the engine design concepts. General Electric had originally planned on using a carbon-carbon nozzle. However, carbon-carbon technology being explored in component testing did not mature as rapidly as expected, and the evolving ATF requirements were changed to place greater emphasis on low observables, particularly in the aft sector, in the RFP that was released in November 1985. General Electric responded to these developments with metal exhaust system and a larger fan for increased cooling air.

YF120
General Electric initiated its YF120 engine design in February 1987 and achieved first engine to test (FETT) in February 1989 (24 months). The design process continued to evaluate variations in design to address airframe contractor mission needs and competitive pressures. This resulted in two compressor configurations being engine tested; these two designs were designated Block I and Block II. The final result was that the YF120 engine configuration flight-tested was very close to the final proposed EMD design, including the all-blisk compression system. Proposed F120 production engine thrust levels were demonstrated and flown.

<skipped>

The YF120 design employed a fan and airflow size 12% larger than that of the XF120. This size increase was in response to the need for more cooling air for the metal exhaust system and the increased ATF thrust requirements. Overall pressure ratio was 22. Dura¬bility was addressed using thermal barrier coatings (TBCs) and tailored cooling air distribution. AMT endurance testing was conducted at a turbine temperature that allowed a margin for safety and engine-to-engine variations. As a result of the short, compact hot section with the vaneless high-pressure/low-pressure turbine concept, there was still 30% less hot section cooled surface area than the General Electric F110 engine. Variable cycle engine (VCE) features were simplified from the XF120 design, and maintainability requirements were rigidly enforced during the design process.

YF120 configuration
Fan stages 2
Compressor stages 5
High-pressure turbine stages 1
Low-pressure turbine stages 1
Bypass ratio 0.32 Thrust class (in afterburner) 30,000 Ib"

For info on F-120 flight tests, go buy the book http://www.amazon.com/Advanced-Tactical-Fighter-F-22-Raptor/dp/1563472821.
 

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RobertWL

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wow, Thats all very helpful information. :) I really appreciate it.
 

AeroFranz

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This is just hearsay, so don't quote me on that.
I heard the F120-powered YF-23 was a rocket, the real figure for max speed never being released. OTOH, I also heard it was thirstier than the F119.
Sorry, no way to check this, like I said, just random pieces of information picked here and there.
 

KJ_Lesnick

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AeroFranz,
I would have never guessed it would have been higher in fuel consumption over the F-119.


KJ
 

AeroFranz

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Yeah, you'd think the variable cycle would help...my guess is, the F120 SFC was probably better over a certain speed range, and worse in others. I don't know where the design point for the F119 is, but you would assume that at that particular point it would operate more efficiently than the -120.

Maybe someone else can confirm this, i don't even remember where i picked up this particular piece of information. it certainly did not come with an explanation. Sorry :)
 

Blaze1

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I've been wondering, does the rear VABI allow for less nozzle modulation and a nozzle setting biases/optimised more for drag reduction at non/low afterburning flight?

Blaze1
 

SOC

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AeroFranz said:
This is just hearsay, so don't quote me on that.
I heard the F120-powered YF-23 was a rocket, the real figure for max speed never being released.

I've heard something similar. The repeatable portion of the conversation is that the YF-23/F120 combination was absurdly fast and would likely have been thermally limited; i.e. the maximum attainable speed would've been limited not by thrust or aerodynamics, but by the thermal tolerances of the airframe and cockpit.
 

Stargazer2006

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SOC said:
the maximum attainable speed would've been limited not by thrust or aerodynamics, but by the thermal tolerances of the airframe and cockpit.

:eek: :eek: :eek: :eek: :eek:

I had always wondered was the YF120 was heard no more after the ATF competition was over... No wonder they declared the F-22 as the winner! If the F-23/YF120 combination had THAT potential, they were better-off claiming the program to be dead and pursuing the efforts in a different direction. This combination would make a highly-capable long-range interceptor for instance... not to mention the gain in using YF-23 aerodynamics and YF120 propulsion in high-altitude reconnaissance types!
 

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sferrin said:
I read soemwhere that the F136 doesn't really take much from the F120. Certainly not to the degree the F135 is derived from the F119.

True - the F-136 is essentially an entirely new engine using both GE and RR input.

Regards,

Greg
 

Abraham Gubler

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Before people get to far down the fan fiction path may I refer you to "Advanced Tactical Fighter to F-22 Raptor: Origins of the 21st Century Air Dominance Fighter (AIAA Education Series)" by David C. Aronstein, Michael J. Hirschberg and Albert C. Piccirillo (Author), In which they state (with authority) that both the YF-22 and the YF-23 flew faster in both maximum speed and supercruise when powered by the YF120. Which considering the YF120 was in many ways a more advanced engine than the YF119 is not such a surprise. More advanced meaning more expensive and difficult to develop which was a big reason why the YF119 was selected for the production engine.
 

overscan (PaulMM)

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Yes, I reckon the F-15 and the F100-PW-100 provided a lesson in stretching the state of the art that the USAF wanted not to repeat on the ATF, which was risky enough in other areas.
 

sferrin

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Abraham Gubler said:
Before people get to far down the fan fiction path may I refer you to "Advanced Tactical Fighter to F-22 Raptor: Origins of the 21st Century Air Dominance Fighter (AIAA Education Series)" by David C. Aronstein, Michael J. Hirschberg and Albert C. Piccirillo (Author), In which they state (with authority) that both the YF-22 and the YF-23 flew faster in both maximum speed and supercruise when powered by the YF120. Which considering the YF120 was in many ways a more advanced engine than the YF119 is not such a surprise. More advanced meaning more expensive and difficult to develop which was a big reason why the YF119 was selected for the production engine.

At least part of the speed difference was due to the fact that the YF119 was designed for a 50,000lb aircraft (the original requirement) while the F120 was designed for a more likely 60,000lb aircraft. IIRC the YF119 got a new fan (among other things) to bump the power up on it's way to becoming the F119

"P&W’s YF119 design for flight demonstration was only slightly different
from its XF119 design for ground testing and could not meet the
new higher thrust and other requirements in a flight demonstration.
GE’s YF120 engine, by comparison, was far closer to its proposed
EMD design baseline. As a result of these two different approaches,
both the Lockheed/GD/Boeing YF-22 and the Northrop/McDonnell-
Douglas YF-23 ATF demonstrator aircraft showed higher performance
levels with the GE flight demonstration engine than when
equipped with the P&W flight demonstration engine. However, the
Air Force did not consider this demonstration to be a performance
“fly-off” but rather a demonstration of the technical and management
capability needed to meet the program objectives during EMD
with the least technical risk and the lowest cost."

http://www.rand.org/pubs/monograph_reports/MR1596/MR1596.appb.pdf
 

mz

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GTX said:
sferrin said:
I read soemwhere that the F136 doesn't really take much from the F120. Certainly not to the degree the F135 is derived from the F119.

True - the F-136 is essentially an entirely new engine using both GE and RR input.

Regards,

Greg

What do you do with those bypasses anyway if you're not going to go very fast? They're only used when the inlet does enough compression, no?
 

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Just found a couple of new YF120 pics

http://www.yf-23.net/galleries/trough.html

 
A

AAAdrone

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One of these days, I am going to go back to that museum in Ohio and check out those YF120 engines. Until then, I guess I'll have to make due with Mr. Lowther's pics. :) thanks OBB!
 

Trident

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NEAT! Always loved the funky IGV shape, although it appears to be fixed judging by these photos which might hint that they're actually radar blockers in function?
Anyway, many thanks OBB!
 

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On the high speed of the yf-23, I remember seeing some literature next to a cross section of the yf-23 that said it was the closest any aircraft has been to a perfectly area ruled airframe. Has anyone heard similar claims? http://en.wikipedia.org/wiki/Area_rule
 

tartle

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Claim here.
Good description of Whitcomb's work here.
One of the first aircraft to be designed with the help of cfd.
Quote from Programme manager, Steve Smith
“If you think that the ultimate in technology advancement and aerodynamic design and systems engineering is the most efficient way to get from one place to another or to accomplish a job, those two airplanes (the Yf-23 and the B2) are the most efficient airplane designs I’ve ever seen.”
 

tartle

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This is why the area rule is named after Whitcomb. It is fascinating how the technologists are eventually aided by the scientists... 'know how' become 'know why'... but more importantly 'know[ing] who' to ask is a major plus!
 

KJ_Lesnick

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Frankly I have generally heard better things about the YF120 engine design in terms of superior speed: I assume it had better SFC figures though I'm not 100% sure.


What does strike me as a worry to the design frankly is the blisks: They pose a maintenance issue in that you can't take out the damaged blades and replace them: You'd have to graft on a whole new blade using specialized procedures that would require you to do one of the following
  • Buy a super-abundance of engines so even if you have to send one back to the manufacturer, you'll have plenty to go: The pitfall is it costs a lot more money, and if the enemy somehow manages to pull off an OCA strike you're screwed
  • Dissassemble everything upstream of the stage/stages that took damage; then plop a new stage/stages in and re-assemble the engine: In a war-zone, you want/need as many aircraft ready at a moments notice to carry out as many sorties as possible
  • Buy all the equipment GE uses to repair blisks; train personnel to repair them; possibly get a GE service rep on base: It could be justifiable in national security grounds. There's still the OCA strike issue...
 

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