Supercruise for F-35 ?

[seruriermarshal]

From a MMRCA contestants analysis page 98 :

In fact, the Eurofighter remains the only aircraft among the MMRCA competitors to have demonstrated some sort of supercruise capability (though this capability falls far short of the sustained supercruise capability of the F-22A and the F-35).

http://carnegieendowment.org/files/dogfight.pdf

 

[sferrin]

Can't wait for the opportunity to post that on Ares. (Of course we'll get to hear how they were paid to lie in that report by B.S. most likely.)

 

[Arjen]

You might want to quote this in context:

The U.S. Air Force defines supercruise as “the ability to cruise at speeds of one and a half times the speed of sound or greater without the use of afterburner for extended periods in combat configuration.” By this standard, none of the aircraft in the MMRCA race possess supercruise capabilities, although the Typhoon comes closest in this regard.

ISTR max speed for the F-35 is something like M1.6, I find it hard to swallow F-35 doing M1.5 without afterburner. Who writes this stuff?

Does the F-35 supercruise?
No, neither the F135 or F136 engines were designed to supercruise.

http://www.jsf.mil/contact/con_faqs.htm

 

[Steve Pace]

One of the two YF-17s, powered by two lowly GE F101s, went supersonic in level-attitude flight without its afterburners lit. -SP

 

[Arjen]

The YF-17 was a sweet thing with a better thrust to weight ratio than the F-35. Less portly too

 

[Trident]

As Arjen says, I seriously doubt it. Maybe the author was defining supercruise as non-afterburning flight at more than Mach 1.0, as David Fulghum on Ares did once when talking about the F-35. While it appears unlikely that the aircraft is capable of achieving even that (Mr. Fulghum is the only reputable source I know who has ever claimed so) this position would at least be compatible with the jsf.mil statement if we assume the latter reflects LM's Mach 1.5 threshold. However, the author is then guilty of inconsistency since he clearly establishes that he subscribes to the Mach 1.5 definition and thus does not credit the Typhoon with the capability.

XB-70 Guy: Don't you mean J101s? It would come as no surprise if the tiny YF-17 achieved supercruise with two mighty F101s

 

[lantinian]

Still...one has to acknowledge the pilot report of chasing aircraft having to lit up afterburners to stay in formation with the F-35 in some maneuvers.

I recall similar reports when the F-22 was tested.

The YF-17 was a sweet thing with a better thrust to weight ratio than the F-35. Less portly too

Sure, but the F-35 is designed to carry a lot more stuff so to me a meaningful comparison will be to see what the Dry Trust / Empty Weigh ratio is. I think the F-35 is just about equal to the YF-17 on this one.

This seemingly official report also confirms some supercruise capability for the F-35
http://www.ainonline.com/news/single-news-page/article/pratt-whitneys-f135-breaks-sound-barrier-on-f-35b-25262/

 

[Ogami musashi]

Mach 1.07 is not considered supersonic. A plane is supersonic when the overall flow speed is supersonic and that happens near mach 1.2 with variations according the plane's design.

So talking about a plane that goes beyond mach 1 without afterburner they're quite numerous, i recall the T-38 does it also.

I guess the relevance is more a question of range and speed and then we will fall into the "F-22 failed its ATF supercruise requirements" debate...

 

[Steve Pace]

As Arjen says, I seriously doubt it. Maybe the author was defining supercruise as non-afterburning flight at more than Mach 1.0, as David Fulghum on Ares did once when talking about the F-35. While it appears unlikely that the aircraft is capable of achieving even that (Mr. Fulghum is the only reputable source I know who has ever claimed so) this position would at least be compatible with the jsf.mil statement if we assume the latter reflects LM's Mach 1.5 threshold. However, the author is then guilty of inconsistency since he clearly establishes that he subscribes to the Mach 1.5 definition and thus does not credit the Typhoon with the capability.

XB-70 Guy: Don't you mean J101s? It would come as no surprise if the tiny YF-17 achieved supercruise with two mighty F101s

Yes, J101s - my error. :-\

 

[Sundog]

Mach 1.07 is not considered supersonic. A plane is supersonic when the overall flow speed is supersonic and that happens near mach 1.2 with variations according the plane's design.

So talking about a plane that goes beyond mach 1 without afterburner they're quite numerous, i recall the T-38 does it also.

I guess the relevance is more a question of range and speed and then we will fall into the "F-22 failed its ATF supercruise requirements" debate...

It's actually specific to the airframe. One airframe may have fulley developed supersonic flow at M=1.1 whereas another may not have it to M=1.15. It isn't the "generic" term which defines it, it's the local flow field around the aircraft.

Also, just because the F-35 has a "listed" top speed of M=1.6, that doesn't mean it can't have a supercruise speed of M=1.4. What limits the top speed could be the inlet design, I've not seen any mention that it's top speed is due to a lack of thrust versus it's drag.

 

[Arjen]

Eurofighter is said to achieve M1.1-1.5 on 120kN dry thrust, loaded weight ~16,000kg max ~23,500kg.
F-35 has 125kN dry thrust, loaded weight ~22,500kg max ~32,000kg.

I used wikipedia for stats.

At best I would expect comparable performance for both aircraft on dry thrust; considering F-35 presents more frontal area than Eurofighter I would expect the F-35 to lag behind. If the stats don't check out: I haven't the foggiest.

 

[sferrin]

I guess the relevance is more a question of range and speed and then we will fall into the "F-22 failed its ATF supercruise requirements" debate...

AFAIK it exceeded it. The requirement was 1.6 IIRC and it can do better than 1.7. How does that equate to "failed its ATF supercruise requirements"?

 

[sferrin]

Eurofighter is said to achieve M1.1-1.5 on 120kN dry thrust, loaded weight ~16,000kg max ~23,500kg.
F-35 has 125kN dry thrust, loaded weight ~22,500kg max ~32,000kg.

I used wikipedia for stats.

At best I would expect comparable performance for both aircraft on dry thrust; considering F-35 presents more frontal area than Eurofighter I would expect the F-35 to lag behind. If the stats don't check out: I haven't the foggiest.

Dry power for the F-35 is probably closer to 150kN. Remember, it's rated at ~50,000lbs thrust not the 43,000lb figure that was published for years.

 

[LowObservable]

The 43,000-pound figure (and 28,000 pound intermediate) are official and widely used. There is a 56,000 pound figure that never goes away, but it was someone at RR (IIRC) theorizing about what you could get with the largest possible augmentor, on a production model of the Boeing engine, which had a higher BPR and mass flow than the LockMart version.

However, thrust is not the whole story. The F119, EJ200 and J101 have lower bypass ratio (and higher dry specific thrust) than the F135. It's a trade - better for supersonic and transonic, not as efficient in the cruise.

Inlet design, and aerodynamics (fineness ratio, sweep angles) also play a part.

Interestingly, the EF people say that supercruise was not a spec item for the Typhoon. It was a fall-out from a sustained-g-at-Mach design point.

 

[erkokite]

I would posit that the report got their facts wrong- it is not a report on the F-35, so I suppose this is forgivable.

While it is reasonable to assume that the F-35 can exceed M=1.0 on dry power, all of the Eurocanards (and the F-16 b60 possibly as well) can also do this with a load, so it is inaccurate to state that the EF is the only aircraft capable of doing so.

If one is using M=1.5 as the threshold, then this is contradicted by the FAQ at JSF.mil, as well as the official LM documents. The design of the F-35 (wing shape, engine bypass ratio) does not suggest large supercruise capability, if at all, nor do the requirements dictate such a thing. Design was optimized around the transonic regime in the CAS role.

Remember, the F-22 can supercruise at M>1.5, but in order to do so it has two large engines that are essentially "leaky turbojets," as well as a much greater sweep angle to the wing LE. To suggest a similar capability for the F-35 seems highly implausible.

 

[sferrin]

The 43,000-pound figure (and 28,000 pound intermediate) are official and widely used. There is a 56,000 pound figure that never goes away, but it was someone at RR (IIRC) theorizing about what you could get with the largest possible augmentor, on a production model of the Boeing engine, which had a higher BPR and mass flow than the LockMart version.

The 56k was quoted by RR several years ago for the F136. The 50k figure is for the F135 and was announced several months ago and published widely. As you well know. GE was going on about how their F136 would be more powerful than the F135 with some development so P&W pulled the rug out from under them by announcing they were ALREADY running higher than GE would with development.

http://www.aviationweek.com/aw/generic/story_generic.jsp?channel=defense&id=news/asd/2010/08/27/01.xml&headline=Pratt

"WEST PALM BEACH, Fla. — Pratt & Whitney is upping the ante in the ongoing F-35 Joint Strike Fighter engine war by revealing the F135 has achieved combat-rated thrust 20% higher than the specification. The disclosure raises the demonstrated sea-level thrust for the F135 above 50,000 lb., and follows results from the General Electric/Rolls-Royce Fighter Engine Team earlier this month that indicate the F136 alternate engine has in excess of 15% margin against the same specification."

 

[Ogami musashi]

it's actually specific to the airframe. One airframe may have fulley developed supersonic flow at M=1.1 whereas another may not have it to M=1.15.

Mach 1.07 is not considered supersonic. A plane is supersonic when the overall flow speed is supersonic and that happens near mach 1.2 with variations according the plane's design.

It isn't the "generic" term which defines it, it's the local flow field around the aircraft.

Mach 1.07 is not considered supersonic. A plane is supersonic when the overall flow speed is supersonic and that happens near mach 1.2 with variations according the plane's design.

That's how it is defined in every fluids mechanics book/course. When the flowfield velocity is not fully supersonic everywhere we are in the transonic domain.

AFAIK it exceeded it. The requirement was 1.6 IIRC and it can do better than 1.7. How does that equate to "failed its ATF supercruise requirements"?

I meant the speed/range requirements; Down from 800 nm @ mach 1.6 (+ 400 nm @ mach 0.9) to 420nm @ mach 1.6 (+200 miles @ mach 0.9) in 1994 circa due to the plane being too heavy to maintain original range requirements which made it fail the maneuverability requirements; LM asked for relaxing some parameters either maneuver or supersonic range, DOD chose range the plane lost more than 2 tons of internal fuel capacity.

 

[sferrin]

LM asked for relaxing some parameters either maneuver or supersonic range, DOD chose range the plane lost more than 2 tons of internal fuel capacity.

Makes sense now. There was a huge difference in internal fuel between the YF-22 and F-22A.

 

[Trident]

AFAIK it exceeded it. The requirement was 1.6 IIRC and it can do better than 1.7. How does that equate to "failed its ATF supercruise requirements"?

It would make no sense for the supercruise requirement to specify a Mach number only with no other conditions, I'm willing to bet the USAF also set out an associated endurance figure. So the Raptor, while easily fast enough, may have failed to meet the latter considering that its internal fuel capacity is not actually that impressive (less than the F-35A/C, IIRC!).

EDIT: Well, seems I've been well and truly beaten to it

Also, just because the F-35 has a "listed" top speed of M=1.6, that doesn't mean it can't have a supercruise speed of M=1.4. What limits the top speed could be the inlet design, I've not seen any mention that it's top speed is due to a lack of thrust versus it's drag.

I think the Mach 1.6 figure is merely a performance requirement, not necessarily the actual capability of the aircraft, so in theory it could be faster. As for the inlets, at least in terms of fundamental limitations DSI intakes should not be that restrictive as the test installation on the F-16 was flown throughout the entire envelope (which would imply Mach 2.0). However, as erkokite says the F-35 just doesn't seem to tick the right boxes, at least from a superficial point of view.

Like LO, I have also been told (don't remember where or by whom) that supercruise was not a stated requirement for the Typhoon - other performance requirements combined to define an aircraft which would be capable of doing it.

 

[F-14D]

Isn't it possible that the F-35 "supercruise" statement in the original document we're talking about was a typo or mistake by the author of the paper? There was no requirement for it in the JSF program, so while it's nice to have, it would be a fallout, rather an design driver. so why pay the penalty to get it in a plane that doesn't need it? BTW, as far as the M1.5 threshold goes, keep in mind include the fact that USAF/Lockheed is going to define things in a way that makes them most look good and exclude as many else as possible, hence their definition of "supercruise". If the F-22 could only sustain M1.4, their definition would start at ~1.3. By the same token, if it was found the Raptor could sustain 1.9, I'd wager their definition would somehow magically become ~1.8.

Regarding thrust of F135-F136, my understanding was that when GE decided not to go with a YF120 derivative, the baseline thrust they decided to go for was higher than Pratt's and was above the F-35's basic needs, they'd actually be stepping it down for initial JSF applications, and their growth margin was above that higher base, intending to do a lot of it by being able to flow more air instead of just increasing temps, which cuts into engine life. So one company may have demonstrated a higher thrust out of their engine, but that doesn't mean it had the highest ultimate thrust. Remember, the F135 in the X-32 put out 50K, which the plane needed, but I'll wager that early version couldn't have sustained that for very long.

Somebody please enlighten me. Thanks

 

[sferrin]

Somebody please enlighten me. Thanks

Both the F135 and F136 are significantly more powerful than the YF120 was (although optimized for different areas of the envelope). The 50,000lb thrust comment I quoted was for today's F135, not either of the X-variants used in the X-35/X-32 program. Reread the link I posted and it should be clear. Also, what should be clear is that GE was claiming the F136 (which has little in common with the F120) could exceed the 43,000lb thrust requirement by 15% with work i.e. NOT presently. P&W exceeded the requirement by 20% already which would actually put it at nearly 52,000lbs of thrust. Again, that is with TODAY'S F135.

 

[F-14D]

Somebody please enlighten me. Thanks

Both the F135 and F136 are significantly more powerful than the YF120 was (although optimized for different areas of the envelope). The 50,000lb thrust comment I quoted was for today's F135, not either of the X-variants used in the X-35/X-32 program. Reread the link I posted and it should be clear. Also, what should be clear is that GE was claiming the F136 (which has little in common with the F120) could exceed the 43,000lb thrust requirement by 15% with work i.e. NOT presently. P&W exceeded the requirement by 20% already which would actually put it at nearly 52,000lbs of thrust. Again, that is with TODAY'S F135.

Thanks

Oh, I'm well aware that the discussion was about today's F135. My point about mentioning the earlier time, was just to illustrate that they've been able to do this before, but then it would be on an engine that wouldn't have lasted too long at those levels. Given the way the Boeing design flowed air, virtually any engine would pump out more thrust in it vs. the X-35. It would have to for their plane to work.

So, the F135 PR release indicates that they've demonstrated 50,000 lbs. thrust, though it's not completely clear if it did that mounted to an F-35 intake & nozzle or just "in the clear". I'm assuming that in another case they're talking about an engine that would still meet required service life.

GE/RR have been talking about 56k on the F136 for nearly a decade, their point being that they were designing an engine that had a higher baseline, and therefore it could deliver the needed thrust while not having to operate as close to their operating margins, or so they say.

The proof as always, is in the pudding.

 

[Ogami musashi]

Supercruise engine's capacity is down to several key parameters that allow the thrust to be maintained in the transonic/supersonic region where a typical 4th gen engine lose its thrust there;

Since the F135 has redesigned stages i'm not quite sure you can conclude anything from max thrust; And i recall some P&W and/or F-35 program official clearly stating the plane didn't have any supercruise ability.

But well...

 

[Abraham Gubler]

From a MMRCA contestants analysis page 98 :

In fact, the Eurofighter remains the only aircraft among the MMRCA competitors to have demonstrated some sort of supercruise capability (though this capability falls far short of the sustained supercruise capability of the F-22A and the F-35).

http://carnegieendowment.org/files/dogfight.pdf

This is a report written from open source material by an ex-Diplomat. He made a mistake because he doesn't know much about the technical capabilities of fighter aircraft. This is not revealed knowledge it is counter knowledge.

 

[seruriermarshal]

From a MMRCA contestants analysis page 98 :

In fact, the Eurofighter remains the only aircraft among the MMRCA competitors to have demonstrated some sort of supercruise capability (though this capability falls far short of the sustained supercruise capability of the F-22A and the F-35).

http://carnegieendowment.org/files/dogfight.pdf

This is a report written from open source material by an ex-Diplomat. He made a mistake because he doesn't know much about the technical capabilities of fighter aircraft. This is not revealed knowledge it is counter knowledge.

He told you that's a mistake ?

 

[Ogami musashi]

There are certains assumptions in this doc that i'm not sure they are correct, like according to him the gripen has the highest sustained turn rate of all contenders just followed by F-16IN and Superhornet...That's a bit odd about the superhornet..

In the meantime he do speaks about some performance that are logical like the rafale very high ITR, the Super hornet AOA capacity etc..

I don't know..

 

[overscan (PaulMM)]

Its obviously based on secondary sources - look at the notes, he even tells you which ones.

 

[sferrin]

GE/RR have been talking about 56k on the F136 for nearly a decade, their point being that they were designing an engine that had a higher baseline, and therefore it could deliver the needed thrust while not having to operate as close to their operating margins, or so they say.

The proof as always, is in the pudding.

Yes it is, and according to GE they'd require work just to get it 15% above the baseline of 43k which would put it (with work) at about 49,500lbs. P&W is already demonstrating 20% above the baseline.

 

[LowObservable]

If the F-35 could supercruise as fast as the F-22, I'd question why we spent so much on the F-22.

I think that's a simple error in a report that relates only tangentially to the F-35. I would also add that it is more informative in terms of the IAF requirement and the local environment than it is when it talks about technical details, particularly about the Euro candidates.

 

[sferrin]

If the F-35 could supercruise as fast as the F-22, I'd question why we spent so much on the F-22.

I think that's a simple error in a report that relates only tangentially to the F-35. I would also add that it is more informative in terms of the IAF requirement and the local environment than it is when it talks about technical details, particularly about the Euro candidates.

I agree that it's probably a typo (that the F-35 could supercruise as fast as an F-22) though I don't see why that would make one question the value of the F-22. Do we question the value of the F-15 simply because the F-16 can manuever as well?

 

[Sundog]

If the F-35 could supercruise as fast as the F-22, I'd question why we spent so much on the F-22.

I think that's a simple error in a report that relates only tangentially to the F-35. I would also add that it is more informative in terms of the IAF requirement and the local environment than it is when it talks about technical details, particularly about the Euro candidates.

I've not seen anyone state the F-35 could supercruise near where the F-22 does, which, the last I had read is M=1.8 for the production F-22. Or is that in the document you guys are talking about, because I can't see the link at work?

 

[chuck4]

I meant the speed/range requirements; Down from 800 nm @ mach 1.6 (+ 400 nm @ mach 0.9) to 420nm @ mach 1.6 (+200 miles @ mach 0.9) in 1994 circa due to the plane being too heavy to maintain original range requirements which made it fail the maneuverability requirements; LM asked for relaxing some parameters either maneuver or supersonic range, DOD chose range the plane lost more than 2 tons of internal fuel capacity.

How much structural weight does reducing internal fuel capacity by 2 tons save? Couldn't the plane just top up to 2 tons short of full capacity when maneuverability is required, preserving full capacity when range is required? In any case, f-22 is now shorter legged than the F-35, thus reducing the f-22's value as a compliment to F-35 in a battle in the west pacific, for example.






[/quote]

 

[Ogami musashi]

More internal fuel= More tank space needed > less space for other internals > more space needed to get back internal fit> more weight.

In early 90's the empty weight of the plane was around 22 tons;

 

[Dreamfighter]

by revealing the F135 has achieved combat-rated thrust 20% higher than the specification.

"Combat-rated thrust"... Does that suggest thrust when the engine is installed in the aircraft, or can it also be at a test-stand?

 

[sferrin]

by revealing the F135 has achieved combat-rated thrust 20% higher than the specification.

"Combat-rated thrust"... Does that suggest thrust when the engine is installed in the aircraft, or can it also be at a test-stand?

Either way it's 20% higher than the requirement.

 

[Abraham Gubler]

by revealing the F135 has achieved combat-rated thrust 20% higher than the specification.

"Combat-rated thrust"... Does that suggest thrust when the engine is installed in the aircraft, or can it also be at a test-stand?

Either way it's 20% higher than the requirement.

While this kind of thurst increase is going to do wonders for the F-35's MTOW, STOVL bring back, subsonic accleration and sustained turn rate it is not going to make it supercruise.

 

[F-14D]

by revealing the F135 has achieved combat-rated thrust 20% higher than the specification.

"Combat-rated thrust"... Does that suggest thrust when the engine is installed in the aircraft, or can it also be at a test-stand?

Either way it's 20% higher than the requirement.

While this kind of thurst increase is going to do wonders for the F-35's MTOW, STOVL bring back, subsonic accleration and sustained turn rate it is not going to make it supercruise.

The question will also be, what's the fuel burn? This may show more the potential to absorb weight increases in the aircraft over time than necessarily increased performance. If the 43K level allows the a/c to meet its design requirements, the more powerful version may not be worth it to the program, at least in the early models.

 

[Colonial-Marine]

I wouldn't be surprised if the F-35 could sustain M1.1 or M1.2 without afterburner, but I highly doubt it can supercruise at the speed of the Eurofighter of F-22. I also doubt M1.6 is the true max speed, I don't see why it wouldn't reach the M1.8 range of the F/A-18 series or so.

Then again I have generally been optimistic about the F-35 program with the exception of the aircraft's weight, which honestly scares me a bit. It seems like all of the models are a good 3,000 pounds heavier than planned back in the early 2000s.

On another note the section on the Super Hornet really seems to praise the aircraft. Certainly differs from all too common viewpoint that the aircraft is a huge step backwards.

 

[Abraham Gubler]

On another note the section on the Super Hornet really seems to praise the aircraft. Certainly differs from all too common viewpoint that the aircraft is a huge step backwards.

Thie 'viewpoint' is in relation to endurance and the dramatic reduction in the strike radius of a USN CVBG with the retirement of the A-6/A-7/F-14 air wing. This doesn't mean the Super Hornet is a bad strike fighter - it is a very good one - but the USN can't strike as deep inshore as they used to with Tacair. Of course with the demise of the Soviet Union and the fielding of a massive TLAM magazine they don't need to...

 

[F-14D]

On another note the section on the Super Hornet really seems to praise the aircraft. Certainly differs from all too common viewpoint that the aircraft is a huge step backwards.

Thie 'viewpoint' is in relation to endurance and the dramatic reduction in the strike radius of a USN CVBG with the retirement of the A-6/A-7/F-14 air wing. This doesn't mean the Super Hornet is a bad strike fighter - it is a very good one - but the USN can't strike as deep inshore as they used to with Tacair. Of course with the demise of the Soviet Union and the fielding of a massive TLAM magazine they don't need to...

It's not so much that the Super Hornet is a step backward, its electronics and availability are now superb, as much as it is so much less than what might have been. Speaking for the conventional wisdom , it is not as good a pure fighter or strike fighter as what a developed F-14 would have been (although cheaper to run) in the opinion of many. Although a better fighter, obviously, it probably isn't as good as what an A-6F (which was actually canceled in favor of the A-12) and beyond would have delivered in strike. But, most importantly, the Navy is nowhere near as capable as it would have been with the A/FX instead of the Super Hornet. There is a reason the Super Hornet has never won an export competition.

However, all that lies in the realm of "might have been". Unless somehow we got access to the TARDIS, the focus should be on where do we go from here.