Debate on F-35 JSF aerodynamics

[BKNO]

Quote from another topic, the poster will reconise himself...

I can think of any number of mach 2.5+ aircraft that have fixed inlets.

Well, you're more than welcome to enlight us mere mortals.

BTW the notion of "ONE" shock is in fact a false one particularly on aiframes equiped with boundary layers spliter plates and fixed inlets.

In aviation "REAL" terms (NASA and else) it will be dubbed "normal" shock inlet because there can be only ONE single computable solution and pressure recovery can be modeled by the normal shock equation.

There are TWO types here, the PITOT type is a simple tubular design like that of a F-86, the second is that of the F-16 called "Convergent/Divergent", the difference is in the intake leading edge of in later designs the (boundary layer splitter plates) called diverter used in supersonic designs.
http://www.defencetalk.com/forums/attachment.php?attachmentid=1518&stc=1&d=1177928019

Diverter leading edges provoques the MAIN shock at the intake lips with a smaller oblique shock and have to be dimentioned and positioned in such a way that the (small) shock they provock hits the intakes lips at a pre-selected Mach, depending on design optimisation.

Since the assembly is of a FIXED design there can be only one optimised Mach, past it the engine will be poushed beyhond its red line.

In the case of the F-16 design, for mach numbers of approximately 1.6, the pressure losses is greater than 10% and can reazch as much as 60% at M 1.8.
http://www.defencetalk.com/forums/attachment.php?attachmentid=1514&stc=1&d=1177927594

To reach a higher Mach than 2.0, F-15 has a serie of inlet ramps which turn the airflow through multiple oblique shocks and permit a more linear pressure/thrust recovery.
http://www.defencetalk.com/forums/attachment.php?attachmentid=1515&stc=1&d=1177927660

The intake of F-35 is working on the same principle than that of the F-16, the bump integrated on the fuselage wall acting as a "mild-Shock" trigger and controls the diffusion of the boundary layer in front of the intake.
http://www.defencetalk.com/forums/attachment.php?attachmentid=1517&stc=1&d=1177927859

It is of a compresssive/expensive waves design much as that of the Mirage 2000 or SR-71 "Souris", only it is fixed and WAY inside the intake which indicates an optimisastion for lower Mach recovery.
http://www.defencetalk.com/forums/attachment.php?attachmentid=1516&stc=1&d=1177927799

As a matter of FACT F-35 Diverterless Inlet were chosen for several reasons and optimised for an altitude and Mach according to requierements. = lowest drag, lowest weight, lowest cost, and highest propulsion performance.

There was NO performance gain at high Mach when tested on the F-16, so the F-35 Mach limits are to be looked for elswhere like engine pressure recovery and airframe aerodynamics for example.

I am hoping for a proper debate based on FACTS and immune from legends if possible at all!!!

 

[powerslavenegi]

Impressive post mate,anyways have some pretty simple questions regarding the intake design

1.If one looks at the engine intakes of most of the aircraft (except the F-35 and the Raptor) one would find the intake isnt fused with the fuselage infact there exists a clear separation (i.e. a gap spanning couple of inches say),to be precise look at the intakes of F-16(in link potse by you ) and even the Euro canards(Rafale,Typhoon and the Grippen) and the Russian jets Mig-35 and the Su-30.

But if you look at the F-35 and f-17 all have done away with the gap and instead have a slightly bulged fuselage instead eg.://www.defencetalk.com/pictures/showphoto.php/photo/13899

well have come across different explanations on the WWW describing the reasons for such a separation(something got to do with doing away with the turbulence caused due to the boudary layer adjacent to the fuselage),but wanted deeper insights regarding the same.

2.Had read the book (dont remember the name by Dassault avaiation) covering the 'Delta winged' aircraft designed by the French firm there it mentioned as to how the engineers did away with the 'sonic cones'(what ever you call em ) on the Mirage inlets while they were designing the Rafale.
Why did those guys have them in the first place ?

 

[BKNO]

powerslavenegi But if you look at the F-35 and f-17 all have done away with the gap and instead have a slightly bulged fuselage instead

This is the "Stealthy" trend for controling the bopundary layer in this area.
http://www.defencetalk.com/forums/attachment.php?attachmentid=1517&d=1177927856
They do away with the conventional diffuser but the F-35 have a particular design which diffuses part of it around the intake roots:

powerslavenegi 2.Had read the book (dont remember the name by Dassault avaiation) covering the 'Delta winged' aircraft designed by the French firm there it mentioned as to how the engineers did away with the 'sonic cones'(what ever you call em ) on the Mirage inlets while they were designing the Rafale.
Why did those guys have them in the first place ?

We call them "Souris" (Mices) and they were very useful with the technology available at the time (including aerodynamics) they actualy allowed the under-powered Mirage III to reach M 2.+

The design evolution from Mirage III/2000 to 4000 to Rafale is mainly due to evolutionary design and computing progresses with CATIA and its Aerodynamic plug-ins allowing for better design.

I seem to recall something on the nose of the 4000 which was doing a curious job at close to M 1.8, actually nillifying the effisciency of the souris at up to (passed) M2.0.

Thus (If you have the book you can post the details it will be interesting) Rafale front fuselage is designed for speed above M 2.0 only the M-88 dynamic pressures limits it to <> M 2.0 and its Operational speed to 1.8.

I take advantage of your post to point out that engines and intake designs only arent enough to determine the Mach of an aircraft...

 

[powerslavenegi]

This is the "Stealthy" trend for controling the bopundary layer in this area.
http://www.defencetalk.com/forums/attachment.php?attachmentid=1517&d=1177927856
They do away with the conventional diffuser but the F-35 have a particular design which diffuses part of it around the intake roots:

Hm.... I see (you mean apart from the much talked about 'S' curve by eliminating the diffuser and having this design further assists in hiding the engine fan blades from the EM waves,or I am missing something ).

Thus (If you have the book you can post the details it will be interesting)

Sorry man it was long back also a library copy which my father got for me .

 

[zidane1989]

Would the rafale's speed also be affected by the ram coating's speed limit?

 

[rjmaz1]

Would the rafale's speed also be affected by the ram coating's speed limit?

I doubt it.. This is a good example of how lighter/simpler/stealthy fixed inlets can reduce the potential top speed of the aircraft. The Rafale still cruises as quick as previous Mirage aircraft but its top speed is definitely down. This isn't a bad thing as i've heard/seen enough evidence that the in combat they dont go anywhere near the top speed.

Yes the top speed is also down on the F-35, but that doesn't matter for 99% of the missions. Its cruising speed will be decent, possibly equal to or even greater than the legacy jets its replacing which is all that matters.

Everything that BKNO has posted only reflects the top speeds of the aircraft. None of that info will help give us the cruising speed of the F-35. It will only give us a brief indication that the cruising speed will be lower than its top speed and higher than its landing speed.

We can debate as long as we want but at the end of the day the F-35 wont be slow. Its already cruised quicker than a clean Hornet which is a very good.

No enemy aircraft that faces the F-35 will have a speed advantage large enough to make a significant difference. It will not be able to overcome the very significant stealth/detection advantage of the F-35

We wont know who's right for many years until the performance numbers are published.

 

[BKNO]

powerslavenegi Hm.... I see (you mean apart from the much talked about 'S' curve by eliminating the diffuser and having this design further assists in hiding the engine fan blades from the EM waves,or I am missing something ).

NO you're NOT missing anything.

zidane1989 Would the rafale's speed also be affected by the ram coating's speed limit?

It all depends on the frictional characteristics of the material.

rjmaz1 I doubt it.. This is a good example of how lighter/simpler/stealthy fixed inlets can reduce the potential top speed of the aircraft.

This is an inacurate view of reality.

The CHOICE of Mach limit at design stage is the reason for the F-35 Mach limit not the Diverterless Inlet configuration, they could have been designed for a higher Mach.

Had L-M responded to the SAME requierements than for F-22 it would be able to fly at the same Max Mach but requierements were for M 1.5...

rjmaz1 The Rafale still cruises as quick as previous Mirage aircraft but its top speed is definitely down. This isn't a bad thing as i've heard/seen enough evidence that the in combat they dont go anywhere near the top speed.

Again it was against a requierement for a Max Mach of 1.8 and the fact that it is only M 2.0 capable doesn't mean its Max speed is down it means it wasn't requiered nor design to fly at higher speeds than M 2.0.
http://www.defencetalk.com/forums/attachment.php?attachmentid=1519&stc=1&d=1178009743

Still its configuration is derivated from the original M 2.2+ ACX which helps a little.
As for the Operational vs Dash speed it is mostly due to the fact that Dassault always provides datas in Operational values.

BTW Rafale Supercruises at a Mach FAR HIGHER than Mirage 2000 with the same payload, it ALSO outfly it in DRY power only.

rjmaz1 Yes the top speed is also down on the F-35, but that doesn't matter for 99% of the missions. Its cruising speed will be decent, possibly equal to or even greater than the legacy jets its replacing which is all that matters.

Not what a pilot would say about DASH speed when you're winchester and having to bug out from hostile territory.

Reason WHY all external tanks are cleared to M 1.6 on Rafale for example with the possiblity to drop them if needed and reach M 2.0.

SLOW DASH speed means MORE time over danger areas.

rjmaz1 Everything that BKNO has posted only reflects the top speeds of the aircraft.

WRONG: It covers virtually the whole of the flight envelop, subsonic, transonic and supersonic alike, the fact that there are limits that you define as top speed is irrelevant.

Best example is that the intakes provides a marked gain at very low speed as they were optimised for pressure recovery in DRY power at low level for STVOL take off without after-burners...

L-M test pilot already stated a GAIN of <> 33% during Take-off.

rjmaz1 None of that info will help give us the cruising speed of the F-35.

You meant NONE that you know about but L-M actually specified that F-35 will NOT be supercruising in their W-S FAQ page.

rjmaz1 It will only give us a brief indication that the cruising speed will be lower than its top speed and higher than its landing speed.

Where do YOU get your information from please???

rjmaz1 We can debate as long as we want but at the end of the day the F-35 wont be slow. Its already cruised quicker than a clean Hornet which is a very good.

You have NO clue here again. I dont regard a Mach LIMIT of 1.6 as not being SLOW and could post a F-22 comments stating exactly this, F-35 problems are SPEED and LOW CRUISING speed.

rjmaz1 No enemy aircraft that faces the F-35 will have a speed advantage large enough to make a significant difference. It will not be able to overcome the very significant stealth/detection advantage of the F-35

A 4th generation aircraft with 4 AAMs will have a 0.4M kinetiq advantage over it in DRY power, M 0.3 for a Rafale M with 4 MICAs and 1 X 1.250 L.

To use F-22 kineqiq energy advantage, it is considered that with BOTH AIM-120, a F-22 flying at high altitude vs a low flying subsonic (M0.98) target will have an AAM extra range of up to 50%.

I dont know what YOU call this if not a speed advantage large enough to make a significant difference.

MORE TO IT: a 4th gen aircraft equiped with Optronics + BVR IR AAM will be capable of passively detecting F-35, whith a 75% extra range i AAMs, meaning 25%_ (lower) for an AIM-120 having to shoot-up and 50%+ (higher) for the shooter.

rjmaz1 We wont know who's right for many years until the performance numbers are published.

WE already know what L-M published and it is: MACH LIMIT for all vatriants 1.6 and NO supercruise. As for operational considerations i also know trhem well by (ex) profession.
http://www.defencetalk.com/forums/attachment.php?attachmentid=1520&stc=1&d=1178009916
Here are TWO different design configurations for F-35...

 

[Grand Danois]

MORE TO IT: a 4th gen aircraft equiped with Optronics + BVR IR AAM will be capable of passively detecting F-35, whith a 75% extra range i AAMs, meaning 25%_ (lower) for an AIM-120 having to shoot-up and 50%+ (higher) for the shooter.

That makes me wonder why the F-22A is equipped with a radar and no optronics...

No wait! It doesn't. IRST is so inferior to a good AESA that it makes perfect sense.

Primary sensor: radar.

No reason to do the Flanker discussion all over again.

 

[BKNO]

Grand Danois That makes me wonder why the F-22A is equipped with a radar and no optronics...

Lack of funding was the reason for this, the US lags behind in IR/UV/Optronic technology and to keep up with a proper A2A Optronic system it would have been coming close to breaking DoD bank acount.

BTW. LPI doesn't mean UNDETECTEABLE. It ONLY means LOW Probability of Intercept but as a matter of FACT, a system like SPECTRA was tested at NATO MACE-X exercise (Cazauz EW base) successfully vs LPI AESAs.

It's all a question of computing power and sensor sensitivity, another legend goes down in flame.

HERE: L-M FAQ page on F-35.

 

[Grand Danois]

Lack of funding was the reason for this, the US lags behind in IR/UV/Optronic technology and to keep up with a proper A2A Optronic system it would have been coming close to breaking DoD bank acount.

Proves my point. The radar was the most important sensor.

BTW. LPI doesnt mean UNDETECTEABLE. It ONLY means LOW Probasbility of Intercept but as a matter of FACT, a system like SPECTRA was tested at NATO MACE-X exercise (Cazauz EW base) successfully vs LPI AESAs.

This is a strawman. You are putting words in my mouth. I never introduced any LPI as an argument. Why you choose to bring it up and how you attribute it to anything I've said, is something you have to explain.

I just noted that IRST is down the list of priorities when it comes to what sensor goes first on a fighter.

It's all a question of computing power and sensor sensitivity, another legend goes down in flame.

...and accuracy of calibrated sensor model, content and quality of data, and especially concept of employment. And this is where the difference is.

You are just being very selective and omissive in your quotes and arguments.

HERE: L-M FAQ page on F-35.

Wrong link, BKNO.

 

[BKNO]

Grand Danois Proves my point. The radar was the most important sensor.

Agreed.

Grand Danois This is a strawman. I never introduced any LPI as an argument. Why you choose to bring it up and how you attribute it to anything I've said, is something you have to explain.

I didn't i just posted informations on the subject, no fuss.

Grand Danois I just noted that IRST ist down the list of priorities.

It IS for the US as technology developement.

A totally different phylosophie than the European or Russians...

Grand Danois ...and accuracy of calibrated sensor model, content and quality of data, and especially concept of employment. And this is where the difference is.

Good to see someone knowing his subject but dont worry if you dig you'll figure we got what it takes...

Grand Danois You are just being very selective and omissive in your quotes and arguments.

You're paranoid or confrontational, you choose i have NO time and post what i can.

Grand Danois Wrong link, BKNO.

Not regarding the topic subject here, it's about the dresigned MACH LIMITS as provided by L-M as for Sept 2007...

 

[Grand Danois]

You're paranoid or confrontational, you choose i have NO time and post what i can.

Whatever you think. I'm just unhappy with, say, arguments wrt capability based on 8 year old statements delivered in a political context where the F-22A was in risk of cancellation. I.e. desperate.

That kinda stuff.

Not regarding the topic subject here, it's about the dresigned MACH LIMITS as provided by L-M as for Sept 2007...

Well, yes. Inside the wider topic. I was adressing the sensor issue, so figured you posted the wrong link in your reply to me.

 

[BKNO]

Grand Danois Whatever you think. I'm just unhappy with, say, arguments wrt capability based on 8 year old statements delivered in a political context where the F-22A was in risk of cancellation. I.e. desperate.

What is a desperate move is to try to deny this one while taking it out of its contest.

Beside you totally failed to make a counter-point here.

More to it, if F-35 had anywhere near the A2A capabilties the USAF needs they would rather have more of them than F-22 for the buck no???

So i believe that what they were saying at the time was correct and that your insistance into basing your own opinions on incomplete fatcs and datas is your problem, not mine, i provide with all sort of infos including 8 years old archives.

Grand Danois Well, yes. Inside the wider topic. I was adressing the sensor issue, so figured you posted the wrong link in your reply to me.

I only replied to one of the answers i was given as for your analysis on the sensor issue it doesn't apply nor to european nor to russian IRSTs if you care to inform yourself that little.

 

[Grand Danois]

I only replied to one of the answers i was given as for your analysis on the sensor issue it doesn't apply nor to european nor to russian IRSTs if you care to inform yourself that little.

If you open the link you provided, you'll realise it contains nothing on the subject of optronics.

This suggests that you may have wished to post another link on the subject, but mixed them up.

 

[BKNO]

Grand Danois This suggests that you may have wished to post another link on the subject, but mixed them up.

No no mix-up here it was on the subject of F-35 Mach limits as stated by L-M.

For the optronics issue i will be more than happy to provide if you insist.

From were we're standing there is a HUGE amount of sceptiscism mainly based on the ignorance of what is going on in Europe.

Cant help it if European and Russians alike believe stealth can be defeated.

I am not being confrontational or else i have a totally different set of information to the point that i believe it is even a cultural thing is you see what i mean....

 

[Grand Danois]

No no mix-up here it was on the subject of F-35 Mach limits as stated by L-M.

For the optronics issue i will be more than happy to provide if you insist.

From were we're standing there is a HUGE amount of sceptiscism mainly based on the ignorance of what is going on in Europe.

Cant help it if European and Russians alike believe stealth can be defeated.

I'm European, living in Europe.

I would think 'defeated' is a wrong term. It's rather that the advantage that comprehensive radar signature management gives you will be less as time progresses.

Any relevant signature reduction gives you a huge advantage over your adversary. It will become less, but still significant. Unless, say the adversary fields a comparable capability.

The US approach is actually very holistic, and as such, stealth is no achilles heel. trying to make the argument that the American approach is one-dimensional, is a strawman.

 

[Rich]

More to it, if F-35 had anywhere near the A2A capabilties the USAF needs they would rather have more of them than F-22 for the buck no???

You dont live here do you? Ever since we started this hi-lo stuff, "good exuse to build more fighters", we have always underestimated the performance of the lo component. Why you ask? Because if the F-16 type aircraft could perform as well as the F-15, or near close to, then the congressman would start screaming, "why do we need to buy the F-15"?

Small wonder the Hi part of the equation gets built first aint it? Then, to be even more slick, the Generals start saying, "Oh well the F-15s have more hours on them so we have to build their replacements first". And that creates a on-going cycle of the USAF getting its expensive ATA F-wonder planes first.

And the funny thing is planes like the F-16 had more then enough ATA ability for us to go with one fighter. But try telling a general that. I mean if you were a General would you rather have the 180 m fighter or the 50 m fighter?

And so they play their little games to get us all scared and to pay for the darn things. They pull stunts like the circus acts in India where they set up Eagles and Falcons to get trounced in air games that are rigged against them, their pilots winking back at their Generals, "who BTW hold their careers in their hands". They start their slick little campaigns about how we need the 180 m fighter, while throwing off just enough on the 50 m fighter to make it look far less capable.

Its an old game here.

 

[BKNO]

You dont live here do you?

NO but i havent been living out of this solar system for the past 30 years either.

As i say, we got USAFE pilots reporting combat exercises flying OUR Mirage 2000-5Fs from my ex-base vs BOTH types and your stament on F-16 proves to be simply of the highest level of innacuracy when it comes to reality. (If you're HYPED you'll figure which one only with the aircraft type, simple!!!)

Rich Its an old game here.

SURE: Appart for the fact that i play it for the past 30 years, it still doesn't help F-15/F-16/F-35 to escape the laws of physics aerodynamics or operational realites.

 

[Rich]

NO but i havent been living out of this solar system for the past 30 years either.

Oh your going to fit in good here. Let me first tell you that you are dealing with the master of sarcasm. Ive only laid off because the Mods ask me to start resembling a decent human being. But, we'll see if they let me loose.:

As i say, we got USAFE pilots reporting combat exercises flying OUR Mirage 2000-5Fs from by ex-base vs BOTH types and your stament on F-16 proves to be simply of the highest level of innacuracy when it comes to reality.

Huh, what, huh, what? Post your links to backup your babbling or I'll stuff a croissant down your gullet. Your are a Frenchie aint you?

SURE: Appart for the fact that i play it for the past 30 years, it still doesn't help F-15/F-16/F-35 to escape the laws of physics aerodynamics or operational realites.

You played what and where? And "with yourself" doesn't count. Small matter that both the F-15 & F-16s conquered the worlds air during their tenure aint it?

And get a spellchecker. Your spelling sucks!

 

[BKNO]

Rich Oh your going to fit in good here. Let me first tell you that you are dealing with the master of sarcasm.

NOT interested, got a master for KungFu and i'm sure he is far better at it than you are at your art.

Huh, what, huh, what? Post your links to backup your babbling or I'll stuff a croissant down your gullet. Your are a Frenchie aint you?

A link for the AdA magazine? You're dreaming, if you want to read two solutions, LEARN FRENCH + JOIN the AdA!!!nfloorl:
http://www.defense.gouv.fr/air/presse/air_actualites_magazine_de_l_armee_de_l_air

Here you got an idea of the SOURCE.....

I'm afraid even if it doesnt look good in this forum you're going to have to trust me on this one because i'm not about to scan it for you, some of our pilots reports on 2 vs 2 vs Belgian F-16 MLUs can be seen then and there in the internet but it's about it.

If i want a refresh i ask my pals....

Rich You played what and where? And "with yourself" doesn't count. Small matter that both the F-15 & F-16s conquered the worlds air during their tenure aint it?

Played with aircrafts and their weapons for a while as a pro, meaning i had to learn a few thing that apparently still eludes you BIG time not to mention the elementatries necessary for flying them (not AdA thought).

Commercial success is again NOT too much of a guarantee for performances and capabilties.

I'm not a nammie trying to debate about the latest washing powder i'm an ex-AdA specialist and as such your comments on F-15/F-16 make me laugh.

Rich And get a spellchecker. Your spelling sucks!

Go learn French, Dutch and now Chinese then come back for some lecture on my grammar, will ya? Have a good day.

More interesting poster here...

Grand Danois I'm European, living in Europe.

Well in this case i'm surprised you dont show more confidence on optronic systems...

Grand Danois I would think 'defeated' is a wrong term. It's rather that the advantage that comprehensive radar signature management gives you will be less as time progresses.

This is where is trongly desagree, so does SAAB, Eurofighter and Dassault, not to mention the Russian manufacturers.

Grand Danois Any relevant signature reduction gives you a huge advantage over your adversary. It will become less, but still significant. Unless, say the adversary fields a comparable capability.

True but true for both EM and IR. US engines are not designed for lower IR signatures, nor are their exhausts, if you look at the futur upgrades for Gripen and Rafale you'll SEE a comprehensive IR signature programme going with the engines.

Grand Danois The US approach is actually very holistic, and as such, stealth is no achilles heel. trying to make the argument that the American approach is one-dimensional, is a strawman.

It is, compared to the European one, it realies mostly on EM technologies including for thre attack helos and for example Europe like Russia have developed DRMs (Dual Range Missiles) the US still doesnt have them.

+ You dont want to compare F-135 IR signature with that of the current M-88 trust me...