ADMK2Concorde used reheat to accelerate through transonic to save fuel. It was calculated (& demonstrated) that it burned more fuel accelerating slowly on dry thrust than accelerating quickly with reheat. Reheat was switched off at M1.6 or M1.7 & it accelerated to Mach2 on dry thrust, then throttled back for a few hours M2 cruising.
Note that this was at high weights.
I can imagine it being true for other types that a brief burst of reheat to get supersonic might sometimes (depending on load, as with Concorde) use less fuel than dry thrust, because of the reduced time spent transonic.
True, though it didn’t have to be designed to cruise over the range of altitudes and speeds that a fighter has to, nor be capabe of accelerating as quickly, subsonically, transoncalky or supersonically, it had the luxury of being able to be designed for a relatively narrow cruising profile, it was not ever encumbered with external stores and it had the “luxury” of being equipped with turbojet engines rather than the usual turbofan engines of the modern fighter (such as a Gripen…)
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ADMK2It’s in fact the opposite! A brief use of the afterburners gets you faster there and may in fact save fuel at the end. Even the might F-22 uses the AB to accelerate, albeit it can do it without AB.
“May” is the key word. Again it is quite curious that they have chosen not to tell us such things.
They are clearly proud of their “supercruising” capability and the implied lack of it in other fighters (and I’m not even referring to the F-35 here).
Why not really impress people?
ADMK2And this is the implementation of Sears-Haack (or lack of)
And if we were in 1950 I’d agree with you. But we’re not. F-35 doesn’t conform to the “traditional” area rule, but then neither does the F-22 nor the B-747.
Aero-dynamicists have found may ways of implementing the area rule and the traditional “cigar shape” is not the only way to do so.
ADMK2Fuel efficiency?
Where’d you get that idea from?
People have a misconception about the transonic drag rise – you’d nearly think they think that drag lowers as you get out of the transonic regime… of course, if that were the case then no fighter would ever have had a top speed of around Mach 1.3… no aircraft, like say, the B-1b or F-100…
The actual drag force is rising as a square function of velocity… so in reality, there is no magical land above Mach 1.2 where fuel efficiency increases.
You’re putting words into my mouth, or rather my post. Never once did I suggest that drag lowers, the faster you go.
What I stated was that the airflow ‘smooths’ out when out when you are truly supersonic with the airflows in the transonic regime being more turbulent.
I would suggest that this explains why so many aircraft are able to pass through the transonic flight regime and fly supersonically using reheat but are then able to ‘throttle back’ and remain supersonic on dry thrust only.
I wonder if this can truly be considered “supercruising” though because as I understand such things the apparent main benefit is the decreased fuel burn when using dry thrust only compared to reheat, but if you HAVE to use reheat to GET supersonic in the first place (even if you can remain there on dry thrust only) then I’d suggest many of the benefits would be eaten up through the use of that reheat.
It is also not such an amazing or noteworthy capability as many aircraft have proven capable of ‘supercruising’ this way.
I then wonder when I’ve never seen SAAB claim to have passed entirely through the transonic ‘regime’ on dry thrust alone and why they wouldn’t make that claim IF their aircraft can do so? Certainly SAAB is not shy about promoting it’s aircraft’s capabilities so it’s an interesting oversight, IF that’s what it is…
PS, Amiga500, did you note what your own link to that Code One article stated? The bit about later model F-16’s supercruising on dry thrust…
Strange that L-M doesn’t trumpet that capability to the world. They also are not backwards when it comes to promoting their products…
Or could it be that the capability is actually of such little tactical benefit in the case of an aircraft LIKE an F-16, it’s not worth trumpeting?
ADMK2Mach 1.2 is supersonic because the aircraft is travelling faster than the speed of sound. Always has been, always will be.
Transonic is a term used by us engineers to further detail the local flowfield; as there may be subsonic “pockets” around the aircraft.
The aircraft is still supersonic though – I don’t know where you get the idea that anything above Mach 1.0 would not be treated as supersonic.
The airframe is of course, but the airflow isn’t necessarily, generally even at M1.2 you’re still in turbulent airflows and therefore unlikely to be receiving the fuel efficiency benefits that supersonic cruise (as opposed to augmentor achieved supersonic speed) is supposed to achieve.
THAT, in my admittedly limited understanding of such things is the real reason why L-M chose the infamous M1.5 figure as it’s ‘supercruise speed’ definition, because every aircraft that can do such speeds are generally clear of transonic airspeeds when at such a number.
It can hardly be for marketing purposes IMHO given that A) the F-22 can’t be marketed to anyone besides the USAF and B) simply exceeding M1 on dry thrust is a capability that many aircraft, including their own F-16 can do and if that definition were used, it would hardly be remarkable…
I’m sure most understand that the only real benefit of dry thrust as opposed to augmented thrust at supersonic speeds is the reduced fuel burn on dry thrust as opposed to wet thrust and so we return to the point of my earlier question.
Now I am aware that different aircraft designs handle transonic airflows differently so I ask again, can any more knowledgable person explain the apparent disparity in these issues?
Or must I continue to suspect that SAAB’s claim has more to do with marketing than tactically useful capability?
ADMK2OT. I would love to see an Aussie designed and built aircraft doing 1.2M super cruise. Actually, I would love to see an Aussie designed and built anything doing something. Oh, wait…never mind…
Wow. Must have really, personally offended some people here. They feel a need to make personal attacks.
Clearly if you are able to speak with authority on these subjects. I know this is a Euro based board, but it is rather curious that anythng SAAB, Dassault or Eurofighter Consortium might release on behalf of their own company is taken almost without question, but if L-M release something it’s clearly untrue…
Like the 100nm or so the F-22A can actually supercruise for, with it’s rather large onboard fuel load.
I know the Gripen has ‘superb’ aerodynamics, but when I question the media releases and pose a question about how tactically useful said capability can really be, I receive little other than vitriole directed at me personally…
Anyone would think I insulted a family member, rather than posed a question and offered an insight, lacking in finer details though it may have been.
Could one more knowledgable in these matters, please explain it further to me? How does such a single engined fighter wth the limited amount of thrust it has (compared to other aircraft) and an engine optimised for fuel efficient subsonic cruise and supersonic dash in reheat only manage to achieve a feat that eludes so many other fighters?
And what more, do so whilst achieving quite enormous combat radii, that is claimed to be far superior to other aircraft that seem to carry far more fuel and do not seek or boast of such amazing performance?
And they do it it cheaper, more nimbly with a much smaller logistics footprint and so on.
Quite extraordinary really.
Don’t get me wrong, I quite like the Gripen, but it seems difficult to reconcile some of the realities of modern ombat aircraft, with the claims that are made about this particular aircraft.
And then you see whilst it has entered many a competition it has won quite few overall, all up I think it has managed about 64 airframes exported hasn’t it, with about 24 of those leased? Now I don’t subscribe that simply winning a military aircraft contract automatically equates to greatness as a capability, but it is certainly a recognition of a level of capability, so one might wonder about the capability claims made about aircraft and how they equate, or don’t to the aircraft’s relative success on the export market?
ADMK2So Draggy that it can super cruise with a useful A2A combat load, while the Uber F 16s cannot even with higher thrust engines.
Since when is M1.2 supersonic flight? I am aware that SAAB claim that the Gripen NG can ‘supercruise’ at M1.2 however it is widely accepted that the transonic regime for most aircraft is between M0.8 and M1.3.
More marketing speak I’d suggest and even if the airflow is completely supersonic over the Gripen airframe at M1.2 the range over which the Gripen will be doing this will be quite small and will hardly make much of a difference in the overall scheme of things, IMHO…
ADMK2LM and PW claimed that after two years of delays and related cost rises. I am still intrested to learn what the former and present specifications about thrust per time, temperature, height and weight are!
Related to the original specifications the thrust via lift-fan was no issue at first. When later on it becomes a problem the demand triggered by weight rise has changed. The trims of the overweight F-35B reduced the capability of that as the life-time of critical elements of the design. To stick to the point, none serious does care about the max AB thrust on the bench. For the F-35B the available military thrust from the F135 is the limiting factor for the vertical landing. The design of the F136 allowed a higher military thrust from the start. Just a difference of 5% is enough if some related specifications could be met or not. Be it the same thrust by lower temperatures or to last a critical minute longer f.e. For the F-35A and C it may not matter, but similar thrust at lower temperatures give a longer life-time and lower operating cost by that. PW is well aware about that and will be forced to offer its F135 cheaper to remain competitive. Something good for every buyer to choose between the F135 and F136. 😎
It’s an ever on-going “race” Both GE and P&W are contracted to deliver an engine that meets the program requirements. As we’ve seen with the USAF tanker program, producing a capability that exceeds requirements doesn’t necessarily win you contracts.
From January, P&W will start tests on a higher-power version of the engine. The XT68LF1 is a technology demonstrator designed to boost engine power by up to 10-15%. The demonstrator will introduce new hot section technology to improve engine power, such as new turbine blades and cooling schemes, Croswell says.
There you go. F135 development already exceeds what the F136 can offer. This means squat though as it hasn’t been designed nor proven yet.
GE produces 5% more thrust? When, how why and so on. That is an empty statement. Nothing more. 5% more dry? Wet? At what altitude? What about thrust lapse and so on?
If it is 5% more in wet thrust, then it is irrelevant as far as the F-35B is concerned with vertical landings. I’m sure you can figure out why, if you don’t already know…
In terms of someone’s earlier question, I can’t put my hands on a source right now that shows unequivocally that spending money on F136 will or has directly cost airframes from the F-35 program.
What it DOES do, is take Billions from the DoD which DOES limit funds available for overall spending. The F136 money is NOT money being taken from outside Defence spending in the US. I can provide plenty of resources for that, if people wish.
It is a fact however that airframes continue to be cut yearly from the F-35 program, whilst this waste of effort continues to have hundreds of millions or billions of dollars spent on it, with no guarantee ANYONE will actually buy the engine once it’s development is complete.
If that is not a pork program, then I don’t know what is…
ADMK2PP or maybe Japan is looking to the US as for political reasons they are the traditional overseas supplier of Japanese weapons systems for the last 60 years?
It can’t get the F22 so it takes the next best US product; not because that product is “better” than an alternative but simply because it’s US.
Probably too complicated for you to appreciate though.
On the other hand the F35 may indeed live up to the hype and be the best thing ever, was that 100m USD per copy for the “second / third / fourth (delete as appropriate) best a2a figther in the World?”
Good job the Japs are minted eh…
Japan could have ordered new build F-15K/SG, F-16C/D Block 52+ or F/A-18E/F Block II Super Hornets any of which would be a good F-4 Phantom replacement capability-wise and still satisfied that “built by America” requirement too.
It appears to desire the F-35 over these types…
ADMK2Seriously. You are trying to say the SDB operates in the transonic regime.
Lets keep it sensible, eh? Mach 0.5 at best I would imagine, unless there is terminal maneuvering software.
Oh, and the thing will have to be launched at maximum range to keep the launch aircraft far enough from the S-300/400.
If the SDB is launched from 60kft and 50 miles away, thats a glide angle of around 12.5 degrees.
It’s not the SDB but here’s a JSOW video that RAAF released a short while ago. Bearing in mind that JSOW is a glide weapon as well, how well would your system of choice go in trying to defend against this?
ADMK2Had you looked at the date of that press release?! When I remember well that was demanded for 2008 already. Either PW was idle for over two years about that with the related cost savings or it was the other way around. :diablo:
And? It has achieved it. I said it has achieved it. You contended that F135-PW-600 wasn’t meeting it’s thrust requirements.
Clearly you are wrong and now you have changed tangents in the discussion.
I think there’s a a term for that on the Internet isn’t there…
ADMK2Load of trash.. just wake me up when it can. Everything else is BS.
As for the rest of your post, I just hope mods will take apropriate action and will nicely help me calm you down.You can bring here quotes from a dozen of test-pilots and whole pages of results of CFD simulations, I don’t give damn… it doesn’t fly M1.6 unless it has demonstrated it…
Any questions?
The X-35 flew at M1.67….
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ADMK2What is the price of a single LRIP F-35 right now without the engine?! Why is the F-35B run into weight and thrust problems despite there is a 28 % surplus margin at hand with the present F135?! :diablo:
Er, which model F-35 (there ARE 3…) and which LRIP contract are you referring to?
ADMK2What is the price of a single LRIP F-35 right now without the engine?! Why is the F-35B run into weight and thrust problems despite there is a 28 % surplus margin at hand with the present F135?! :diablo:
Before approaching this argument from such a knowledge free vantage point, perhaps you could try reading the article I posted?
Here is a section of it (well most really) that answers your own question, if you take the time to comprehend it…
The high temperature margin test that took place at Arnold Engineering Development Center at Arnold AFB, Tennessee, involved intentionally running the engine to turbine temperatures beyond design conditions while simultaneously operating the turbomachinery at or above 100 percent of design conditions. The purpose of this test is to demonstrate design margin at the most extreme operating conditions. The test also demonstrated the F135 propulsion system’s ability to produce margin relative to thrust. The test engine produced twenty-eight percent more thrust than the specification requirement.
If you think the F135-PW-600 isn’t meeting it’s thrust requirements, then you might want to ask yourself exactly how it has achieved it’s Initial Service Release?
“Achieving initial service release for the STOVL propulsion system means all three variants of the F135 engine have met all necessary requirements and proven the safety, reliability and performance of this product.
Next…
ADMK2Didn’t they just sanction an additional $4 billion for further F-35B development? Makes an additional $2 billion to have a choice of engine look like a sensible investment in view of the perceived benefits for F-16 (cheaper/better engines than would have been the case with a single supplier).
But it isn’t just an additional $2b. It has been over $5b already. That is sunk cost and can’t be changed, but that isn’t a good reason for spending even more. There are going to have to be simply enormous benefits to justify the extra cost, but there isn’t.
As explained ad nauseum, the F136 will only ever be as good as the inlet/exhaust nozzle allows them to be, the same as the F135.
See above. With enough engines required (thousands during F-35 lifetime) it might be simply wasteful in the extreme NOT to have 2 suppliers in competition with each other.
There have been thousands of engines required for the Hornet, Super Hornet and F-22A fleets. If the idea is so workable, why haven’t there been dual engines for ALL of these platforms?
Fact is the idea DOESN’T work all that well. During the AFE – Alternate Fighter Engine Congress funded both P&W and GE to produce “alternate fighter engines”. The GE F110=100 and the P&W F100-220 were the results of this funding.
The USAF study into the program found this:
In 1984 the Air Force conducted extensive life-cycle costs analyses cover costs to acquire and support the 2,000 engines over 20 years. The analyses were performed on a variety of contract options. The Air Force’s analysis showed that the General Electric and the Pratt and Whitney offers were essentially equal at the 100 percent award level.
The lesson seems clear enough to me. If you fund the manufacturer you choose appropriately and apply fixed price contracts you will get the engines you need at a reasonable cost (reasonable to everyone).
The only real benefit GE offered was a better warranty conditions. What the study doesn’t look at is the cost of the infrastructure, support equipment, training facilities and courses and additional deployment equipment that is required to actually support multiple engine types. It has an enormous flow on effect amongst units, with maintainer qualifications and the effect on transfer opportunities, access to spare parts inventories and so on.
All of that to get a slightly cheaper engine?
Again, it comes down to the fact that if it is such a good idea, why isn’t it done with more platforms? Haven’t seen anyone here try to address that question…
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