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A-A Missiles drag and lift


85th_Maverick

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Hi,

 

After the latest updates the aim-120 has received an unprecedented lifting performance benefit together with an overall lower drag versus AoA, which don't seem right!

 

I've tested that for all of the air to air missiles, the simulated drag coefficient versus Mach function between subsonic, transonic (where the greatest should occur) and supersonic is about constant. It's literally a flat line throughout the Mach ranges.

 

This is a track comparing different BVR A-A missiles:

Aim-120 vs R-27ER and R-77 max ranges comparison.trk

Tacview-20200110-223205-DCS.rar

 

As you can see, the aim-120C and especially the B model overpass their real counterpart's range performance quite well. The aim-120C has hit a target from 70nm (130km). That's exactly the distance that the R-27ER should have. The aim-120B goes even further than the available real numbers show, hitting it's target from 55nm (+100km). No DCS modern Russian A-A missile reaches it's given max range, actually not even 80%!

 

The following is a grossly accepted (an average between many airfoil sections and 3D body shapes) variation of drag coefficient versus Mach at the minimum drag AoA:

 

https://image.slidesharecdn.com/aerodynamics-partii-150210010059-conversion-gate02/95/aerodynamics-part-ii-71-638.jpg?cb=1423531445

 

For the aim-120, the drag versus AoA doesn't increase almost at all. There seems to be almost no drag coefficient variation with AoA as there's little difference in drag when the aim-120B/C is flying straight at low or high AoA or turning! All other A-A missiles have a natural drag increase with AoA.

 

Is it right that the aim-120C (with it's small fins) can fly slower than an aim-9M and almost as slow as a combat loaded A-10C? It seems that we don't need an aim-9M anymore in dogfight, we can now use the aim-120 as it turns better.

 

A track regarding the aim-120's exaggerated lift:

Aim-120 very high lift.trk

 

For instance, the wing loading on an amraam when it's fuel is burned (for an A-A missile, roughly half of it's weight is that of the propellant) is of more than 1000kg/m^2, while that of an A-10C at MTOW is about 445kg/m^2. How is it possible that now the aim-120 can simply fly almost as slow as an A-10C when both are flying at their critical AoA. Anyone who has a bit of knowledge in aerodynamics can know that a straight and high aspect ratio wing has a much greater maximum lift coefficient than the other way around. That alone should be enough to raise some concerns when seeing this simulation. The wing loading differences makes it an even greater "throw"!

 

Indeed, I cannot know the exact numbers but I should accept using a bit of calculations and logic that when flying at it's critical AoA, an aim-120 cannot hold it's weight (no propellant left) any longer below around 500km/h. Btw, the R-27ER starts falling at 620km/h IAS, which is quite realistic! The aim-120 should have a very low critical AoA lift coefficient (or max lift coef. which is usually around 0.7 for most missiles), a very low useful wing area (about 0.05m^2) and very high weight. During playing around against the aim-120, I saw that it was turning with me at very low altitude and slowly decelerating just some tens of feet behind, on the same turning circle that I was flying on at 9G. At about 900km/h, that missile was turning with me at about the same rate (G-load), while any other missile loses lift more accordingly below 1000 to 1200km/h.

 

Here's a comparison track against Russian A-A missiles:

The F-15 player can easily evade any russian A-A missile just by full aft stick and roll.trk

 

The poor R-27s (any model) is the worst of all when it comes to lift. Although it has the biggest fins with the greatest lift coefficient of any missile, it ironically has the worst simulated lifting and max range performances of all. It's not about fairness or stuff like that, but the absurd is now bigger than before!

 

The R-27ER should be able to hit a head on target from 130kms according to the internet. Tested in the above track with better than ideal conditions with both targets at a closure speed of over 4000km/h at 12000m altitude and the R-27ER reaches it's realistic critical AoA of 16-17 degrees and starts falling when traveling just 85-88kms. It only reaches some 68% of the real range. Even the AIM-120B has greater range than the R-27ER...! It's not even worth talking much about the R-77, for which the initial version alone should reach more than 80km. In game, after being fired from 2200km/h at 12km high it falls after some 50kms. The above Tacview is very useful in for a check out.

 

The R-73 has a critical AoA of just 5 degrees? Here's a track:

 

R-73 5 degrees critical AoA.trk

 

The aim-9M also seems to have a critical AoA of 7. Only the aim-120 has it as high as 27 degrees.


Edited by 85th_Maverick
Added more tests info about the AIM-120B
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Good knowledge and common sense make the absurd run for defense.

Flying has always been a great interest for mankind, yet learning everything about it brought the greatest challenge!

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Hi,

 

After the latest updates, the aim-120 has received an unprecedented lifting performance benefit together with an overall lower drag versus AoA, which don't seem right!

 

I've tested that for all of the air to air missiles, the simulated drag coefficient versus Mach function between subsonic, transonic (where the greatest should occur) and supersonic is about constant. It's literally a flat line throughout the Mach ranges.

 

 

I mean you can look at the code as well and this isn't the case. Keep in mind the drag coefficient isn't the major factor in the drag equation, velocity is as its a squared factor. It is the major determining factor, all the other variables are either constant or don't change drastically (for most shots). As such the CD value will largely just impact the rate the drag force increases or decreases with V. Additionally, the amount of time spent in the region with a really high drag coefficient, M0.9 - 1.4 (on most missiles), is quite often not particularly long.

 

This is a track comparing different BVR A-A missiles:

[ATTACH]224842[/ATTACH]

[ATTACH]224845[/ATTACH]

 

As you can see, the aim-120 overpasses it's real counterpart's range performance quite well. No DCS Russian A-A missile reaches it's given max range otherwise.

 

Well, there are several things here.

 

A) All the other missiles are still the old model from when they were reworked back in 2012ish so obviously they would underperform quite a bit compared to the newer amraam (Not that they really should be anyway). The Russian missiles are absolutly still to draggy, as such just give ED time to fix them. Now that they've finally admitied there's a problem with the missiles and are actually working on them... It takes time to run CFD though.

B) The R77 is a strange missile, while at high supersonic speeds it should be similar (but still more draggy) to a 120b in drag but as it gets closer and closer to transonic speeds those grid fins will start producing more and more drag than a standard fin model. So I don't exactly know if i'd use it as a missile to say 'amraam slows down to slowly'. Same with the ER as its a much bigger missile than the amraam as well.

 

 

FnTanqy.png

FnTanqy.png

*These images are from some book on basic missile aerodynamics that I got from a friend. Title of said book is at the top of the above images.

 

 

- Additionally from my own cfd work the R77 is a bit slower than what I have it as. The truth probably lies somewhere in between ED's values and the ones I have:

4nNSMSw.jpg

 

 

The following is a grossly accepted (an average between many airfoil sections and 3D body shapes) variation of drag coefficient versus Mach at the minimum drag AoA:

 

https://image.slidesharecdn.com/aerodynamics-partii-150210010059-conversion-gate02/95/aerodynamics-part-ii-71-638.jpg?cb=1423531445

 

For the aim-120, the drag versus AoA doesn't increase almost at all. There seems to be almost no drag coefficient variation with AoA as there's little difference in drag when the aim-120B/C is flying straight at low or high AoA or turning! All other A-A missiles have a natural drag increase with AoA.

[/Quote]

 

Well... I mean in my own testing they still do loose speed when pulling especially when pulling hard.

 

Is it right that the aim-120C (with it's small fins) can fly slower than an aim-9M and almost as slow as a combat loaded A-10C? It seems that we don't need an aim-9M anymore in dogfight, we can now use the aim-120 as it turns better.

[/Quote]

 

From anecdotal evidence floating around the internet that I've heard/read this sounds about right that the amraam is more maneuverable than the 9M. Additionally, the first AIM-120 kill (AIM-120A externally is the exact same as a 120B) was previously not possible. The missile wouldn't even get close to the target. Now though it should be quite possible assuming no guidance bulls*ery.

 

that's a shot on a bandit 10-12° (or 20-22° forgot the exact degree amount represented by the tic marks on the left) above him, with over 1200kts of closer, at a range of ~2 Nmi...

 

A track regarding the aim-120's exaggerated lift:

[ATTACH]224839[/ATTACH]

 

For instance, the wing loading on an amraam when it's fuel is burned (for an A-A missile, roughly half of it's weight is that of the propellant) is of more than 1000kg/m^2, while that of an A-10C at MTOW is about 445kg/m^2. How is it possible that now the aim-120 can simply fly almost as slow as an A-10C when both are flying at their critical AoA. Anyone who has a bit of knowledge in aerodynamics can know that a straight and high aspect ratio wing has a much greater maximum lift coefficient than the other way around. That alone should be enough to raise some concerns when seeing this simulation. The wing loading differences makes it an even greater "throw"!

 

Indeed, I cannot know the exact numbers but I should accept using a bit of calculations and logic that when flying at it's critical AoA, an aim-120 cannot hold it's weight (no propellant left) any longer below around 500km/h. Btw, the R-27ER starts falling at 620km/h IAS, which is quite realistic! The aim-120 should have a very low critical AoA lift coefficient (or max lift coef. which is usually around 0.7 for most missiles), a very low useful wing area (about 0.05m^2) and very high weight. During playing around against the aim-120, I saw that it was turning with me at very low altitude and slowly decelerating just some tens of feet behind, on the same turning circle that I was flying on at 9G. At about 900km/h, that missile was turning with me at about the same rate (G-load), while any other missile loses lift more accordingly below 1000 to 1200km/h.

 

Something I think your forgeting/ignorant about is that the body of a missile adds a huge amount of lift and in particular the nose cone shape can have a dramatic impact on this as well.

 

The below image is from a document called "Performance Improvements with Sidewinder Missile Airframe Variants" you should be able to find it somewhere on the internet if you want to see for yourself. But for now, the basic summation of the paper is that they were testing the basic shape features of the amraam, in particular, the nose. So they put an amraam nose on a 9L/M and significantly reduced the rear fin size. Yet:

Ej1VoOO.jpg

the Cl and hence the g performance of this modified missile went up! This is in no small part due to the change in the nose cone shape which has a significant impact on drag and lifting performance; far more than one would think it would at that.

 

 

Here's a comparison track against Russian A-A missiles:

[ATTACH]224846[/ATTACH]

 

The poor R-27s (any model) is the worst of all when it comes to lift. Although it has the biggest fins with the greatest lift coefficient of any missile, it ironically has the worst simulated lifting and max range performances of all. It's not about fairness or stuff like that, but the absurd is now bigger than before!

 

The R-27ER should be able to hit a head-on target from 130kms according to the internet. Tested in the above track with better than ideal conditions with both targets at a closure speed of over 4000km/h at 12000m altitude and the R-27ER reaches it's realistic critical AoA of 16-17 degrees and starts falling when traveling just 85-88kms. It only reaches some 68% of the real range, in contrast to the aim-120C which goes far beyond the claimed 105kms.

Something I've noticed over the years is this general rule which really hasn't let me down yet. When dealing with Russian equipment, stated max range numbers tend to be for the most optimal launch conditions. While for US/Chinese equipment it tends to underestimates/more conservative criteria. Just as an example during the Iran-Iraq war a silkworm flew, and hit, a tanker at 120%+ of its previously stated max range.

 

The R-73 has a critical AoA of just 5 degrees? Here's a track:

 

[ATTACH]224841[/ATTACH]

 

The aim-9M also seems to have a critical AoA of 7. Only the aim-120 has it as high as 27 degrees.

 

 

Wel from my info the 9M should have a max alpha around 20°. So, assuming that this higher value is true, if I was a betting man I'd bet a decent sum of money this is due to the fact that all non- AIM120 and AIM7 missiles suffer from more lift induced drag than they should. And that the max alpha values were limited to allow said missiles to have appropriate ranges. Much like how the majority of missiles in the game have had their Cl values (including the R27 and R77) reduced so they don't just kill themselves off the rail.


Edited by nighthawk2174
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Hi Nighthawk and thanks for your reply!

 

I mean you can look at the code as well and this isn't the case. Keep in mind the drag coefficient isn't the major factor in the drag equation, velocity is as its a squared factor. It is the major determining factor, all the other variables are either constant or don't change drastically (for most shots). As such the CD value will largely just impact the rate the drag force increases or decreases with V. Additionally, the amount of time spent in the region with a really high drag coefficient, M0.9 - 1.4 (on most missiles), is quite often not particularly long.

 

Of course that the drag varies as a squared function of speed which is part of the dynamic pressure! As you just say, the time of decelerating between M1.4 through M0.9 isn't necessarily long, proving that a very high drag occurs just there. If you meant that it passes very quickly between M0.9 through M1.4 when accelerating, that doesn't mean that it won't pass through the highest drag coefficient ranges, it only means that the motor provides enough resultant axial Gs to pass it through that region in just a second or two, but the effect is still there. Now just show me where does any of our in game missiles start decelerating faster between M = 1.4 through M = 0.9, proving that there's a variation of the drag coefficient. We, in aerodynamics prefer to talk mostly in coefs, cause those are the most important. When we want to calculate resultant forces/moments, of course we'll need to account for speed, but until then, the performances (which is what I want to talk about) are affected by coefs alone. Do we agree up to this point? You have the tracks and the Tacview! Show me where does any missile have a different CD with Mach. The pictures that you have presented also prove no CD variation with Mach as well, just like in DCS!

 

A) ... The Russian missiles are absolutly still to draggy, as such just give ED time to fix them. Now that they've finally admitied there's a problem with the missiles and are actually working on them... It takes time to run CFD though.

 

Thank God! I really hope they'll try to reduce the supersonic CD and increase the transonic CD to more realistic levels, then finally adjust the required burn times and impulse rates to get the more correct max ranges. I honestly wish them the best! But, I don't want to see a heavy R-27 flying side by side with my A-10 as the aim-120 already wants to prove. Seriously, that aim-120 has about double of the maximum corresponding subsonic lift coef., which is not ok. That very useful youtube footage was cut after the aim-120 was released and according to the closure rate and also confirmed by the youtube counted seconds and distance callouts, the missile was fired from 2nm, but, let's be honest, judging by the footage the shooting aircraft was flying almost towards an interception course with the target so the missile didn't even need much steering so we can't correctly extract it's real max lift coefficient and real critical AoA without data measured within the missile (if this has ever been performed). Until we find the more correct input data, a temporary and more useful solution would be to just use the same minimum drag coef of the amraam to the R-27s and R-77 (although this should have lower supersonic CD, but even identical to the AIM-120 is still better), the corresponding motor impulse versus, burning time, instantaneous weight and reference area will do the rest in simulating how the missiles would decelerate. The inputted base drag is just too high for all of the rest, but at least they simulate a more correct drag vs AoA.

 

B) The R77 is a strange missile, while at high supersonic speeds it should be similar (but still more draggy) to a 120b in drag but as it gets closer and closer to transonic speeds those grid fins will start producing more and more drag than a standard fin model. So I don't exactly know if i'd use it as a missile to say 'amraam slows down to slowly'.

 

Here are some facts:

 

https://en.wikipedia.org/wiki/Grid_fin#Design_characteristics

 

Have they designed those fins to have greater overall drag? No! As you've said, that getting closer and closer to transonic, the drag starts increasing more rapidly with a much higher peak than other missiles prove, which is fairly correct so far. Now, are you saying that it should be more draggy than an aim-120 according to your CFD results? The reality shows different. In supersonic, the things stand upside down for the lattice fins compared to other missiles. The CD gets slightly lower than the lowest in subsonic (in subsonic the friction drag gives the highest amount for these types of fins). It's a more complex explanation of how the grid fins can exploit the effects of the attached shockwaves to reduce the overall drag only through pressure distributions. That way it has a lower than subsonic CD. It's at supersonic speeds where the R-77 excels and only when passing through transonic, either accelerating or decelerating, it's drag is indeed greater than for any other missile. I also use CFD, but i correct the results with mathematical equations and derivatives to extrapolate the more correct values. The CFD is a gamble. Depending on the type of calculus and it's factors, the same model data will give very different and sometimes incredibly erroneous results. It's like you're trying to find the door with a hand on your eyes. Without some experience and right knowledge to find the door, you can't turn part of the hand away from your eyes and completely blind you won't know when you passed through it (got the right results by chance) or passed right by it.

 

Same with the ER as its a much bigger missile than the amraam as well.

 

You are only contradicting yourself saying that the heavier ER decelerates faster than an amraam. What is the decelerating G-load? Isn't it the ratio of the speed difference (from an interval), divided by the time it took to decelerate through that interval (which is the deceleration), divided by the gravitational acceleration constant? It is! So, dividing that deceleration force by the product of dynamic pressure and reference area..., you guessed it, the CD pops so you can check it out! You'll find out how great the ER's CD is in game compared to other missiles. And yes, it also has a high speed performance shaped cone, and yes, also it's fore fins are designed for a reduced supersonic CD (another story).

 

Additionally from my own cfd work the R77 is a bit slower than what I have it as.

4nNSMSw.jpg

 

I don't understand your statement, as the plot you've just showed proves it faster.

 

The truth probably lies somewhere in between ED's values and the ones I have:

 

The truth lies in what you just wrote above, that ED knows that all of the Russian modern A-A missiles (R-73, R-77, R-27) have too much base drag in every condition.

 

Well... I mean in my own testing they still do loose speed when pulling especially when pulling hard.

 

Yes, very little! Videos or tracks prove "how much" speeds is bled by the amraam.

 

From anecdotal evidence floating around the internet that I've heard/read this sounds about right that the amraam is more maneuverable than the 9M.

 

Ok, I agree with you then as I've also calculated the wing loading on the AIM-9 (using the projected fins area (as you'd do with an airplane)) and compared it to the AIM-120 indeed it was a couple of times higher (which is very much). But again, even with the cone's induced vortices the aim-120 still proves to have a maximum subsonic lift coefficient of about 1.5 or so. That's waaaay too much. A subsonic CL max of 0.7-0.75 for it should be usually correct in accordance with a reference area of 0.05m^2.

 

Additionally, the first AIM-120 kill (AIM-120A externally is the exact same as a 120B) was previously not possible. The missile wouldn't even get close to the target. Now though it is quite possible.

 

What wasn't possible with the A model, but possible with the B (they're aerodynamically the same)? Delay to start tracking the target, or some other limitation? Sorry, just curious!

 

Something I think your forgeting/ignorant about is that the body of a missile adds a huge amount of lift and in particular the nose cone shape can have a dramatic impact on this as well.

 

No, I ain't ignorant as you believe and NO, through the cone generated vortices (cause that's were that seemingly magic body lift comes from) doesn't create a "huge amount" of lift on the body of the missile at all. I have probably forgot to mention that I was only talking about the subsonic lift for the start. In supersonic yes, the "wave riding" effect generated by the cone is gaining a high percentage of the total lift, but not that great in subsonic. Also, regarding transonic/supersonic, don't forget (if you know about it) a very important aspect that the drag versus AoA functions have a greater increase in transonic and also in supersonic (more rapidly progressing derivatives) and as such, this "lifty" missile will suffer from a much higher CD increase with AoA in transonic/supersonic compared to subsonic.

 

The below image is from a document called "Performance Improvements with Sidewinder Missile Airframe Variants" you should be able to find it somewhere on the internet if you want to see for yourself. But for now, the basic summation of the paper is that they were testing the basic shape features of the amraam, in particular, the nose. So they put an amraam nose on a 9L/M and significantly reduced the rear fin size. Yet:

Ej1VoOO.jpg

the Cl and hence the g performance of this modified missile went up!

 

For instance, as the speed starts growing from roughly 1000ft/s TAS (about 1097km/h TAS, 0.9M) towards the maximum speed, then decelerate back towards around 1000ft/s, there is NO corresponding/expected fluctuation in the speed function. It's just a smooth straight line during acceleration and a smooth/constant logarithmic curve during deceleration from supersonic to almost subsonic. If a drag coefficient variation would've taken place, the speed increase function should've had a fluctuating curve while passing through the transonic region and the speed decrease function should've also had a fluctuating curve as the curve should've started to deflect downwards between M1.4 (as you've said) or 1562ft/s and around M1.1 or 1227ft/s where the highest drag coef would be taking place (the CD in transonic is roughly 2 to 2.5 times that at Mach < 0.1) and then continue as almost a straight line towards M0.9 and from there on go logarithmic again towards M = 0. At least that's how things go in reality. That drawn presented data is most probably illustrative and the speed versus time functions are simplified only to show the speed and range advantages, NOT accurately detailing how the speed rate varies with time as that was not the purpose of their analysis. When you come across various data, you should always use your judgement and knowledge to tell if there's anything wrong and in this case, that data is not reliable for our discussion.

 

This is in no small part due to the change in the nose cone shape which has a significant impact on drag and lifting performance; far more than one would think it would at that.

 

For those who don't know much about it, yes, it seems magical.

 

Something I've noticed over the years is this general rule which really hasn't let me down yet. When dealing with Russian equipment, stated max range numbers tend to be for the most optimal launch conditions. While for US/Chinese equipment it tends to underestimates/more conservative criteria. Just as an example during the Iran-Iraq war a silkworm flew, and hit, a tanker at 120%+ of its previously stated max range.

 

Ok, you may be 100% right about it and let's say that, ok, the aim-120 is now the first DCS missile to achieve a more realistic range, but still, what kind of "optimal launch conditions" would the R-27ER need in order to hit a target from 130kms? Again, a Mach 4 closure speed at 12000m proved that the missile starts falling when reaching only 68% of the given range. So, how much of "optimal" is there left? Same goes for the R-77, AIM-9, R-73 and all the rest.

 

Wel from my info the 9M should have a max alpha around 20°. So, assuming that this higher value is true, if I was a betting man I'd bet a decent sum of money this is due to the fact that all non- AIM120 and AIM7 missiles suffer from more lift induced drag than they should. And that the max alpha values were limited to allow said missiles to have appropriate ranges. Much like how the majority of missiles in the game have had their Cl values (including the R27 and R77) reduced so they don't just kill themselves off the rail.

 

Ok, I believe you about the AIM-9 and R-73 AoA limitation during flight, so that's not their actual critical AoA, but a performance holding max AoA, but how people "like" the R-27 and R-77 lift (which I also admit by tests that is about the most accurate) may sometimes have little to do with reality. To give you an example of why "liking" isn't necessarily what it should be, I "like" the AIM-54 being able to have tremendous lift compared to it's wing loading or compared to the R-33 which loses lift much sooner for a similar wing loading (the R-33 seems more realistic anyway), be a very "long legs AIM-120" and be able to maintain lock on targets no matter how far or low below the horizon they are and almost immune to clutter such as the AIM-120, but the reality tells that it was losing a maneuvering target quite easily.

 

I'm grateful to this conversation and looking forward to seeing your opinion again!

 

Cheers!


Edited by 85th_Maverick
The MIG-25 target in the video seems straight ahead, not to a side.

Good knowledge and common sense make the absurd run for defense.

Flying has always been a great interest for mankind, yet learning everything about it brought the greatest challenge!

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Of course that the drag varies as a squared function of speed which is part of the dynamic pressure! As you just say, the time of decelerating between M1.4 through M0.9 isn't necessarily long, proving that a very high drag occurs just there. If you meant that it passes very quickly between M0.9 through M1.4 when accelerating, that doesn't mean that it won't pass through the highest drag coefficient ranges, it only means that the motor provides enough resultant axial Gs to pass it through that region in just a second or two, but the effect is still there. Now just show me where does any of our in game missiles start decelerating faster between M = 1.4 through M = 0.9, proving that there's a variation of the drag coefficient. We, in aerodynamics prefer to talk mostly in coefs, cause those are the most important. When we want to calculate resultant forces/moments, of course we'll need to account for speed, but until then, the performances (which is what I want to talk about) are affected by coefs alone. Do we agree up to this point? You have the tracks and the Tacview! Show me where does any missile have a different CD with Mach. The pictures that you have presented also prove no CD variation with Mach as well, just like in DCS!

 

The in game AIM-7 has a full drag curve as in every .1M value has a unique CD value associated with it.

IGUBwbt.jpg

*note this graph is from my missile mod thread and expected is using the rlf drag curve and thrust values from "Standard Missile Characteristics AIM-7F"

Thank God! I really hope they'll try to reduce the supersonic CD and increase the transonic CD to more realistic levels, then finally adjust the required burn times and impulse rates to get the more correct max ranges. I honestly wish them the best! But, I don't want to see a heavy R-27 flying side by side with my A-10 as the aim-120 already wants to prove. Seriously, that aim-120 has about double of the maximum corresponding subsonic lift coef., which is not ok.

 

-From all the info I've ever seen on Russian missiles the current thrust values for all the Russian missiles being discussed (24,27,73,77) are correct as is currently.

-A burned-out R27ER weighs only ~473lbslbs(79.3kg) which considering the size of the missile isn't really that much.

-It has almost double the current lift because the 27 series hasn't been updated yet

 

 

That very useful youtube footage was cut after the aim-120 was released and according to the closure rate and also confirmed by the youtube counted seconds and distance callouts, the missile was fired from 2nm, but, let's be honest, judging by the footage the shooting aircraft was flying almost towards an interception course with the target so the missile didn't even need much steering

-? The target was well above the nose of the launching aircraft (who is even very slightly nose down). The course corrections steering dot was almost off the top of the max error circle...

 

so we can't correctly extract it's real max lift coefficient and real critical AoA without data measured within the missile (if this has ever been performed).

-The real lift coefficients and max aoa absolutely have been measured and tested in wind tunnels/flight tests but we won't see those numbers for decades.

 

Until we find the more correct input data , a temporary and more useful solution would be to just use the same minimum drag coef of the amraam to the R-27s and R-77 (although this should have lower supersonic CD, but even identical to the AIM-120 is still better), the corresponding motor impulse versus, burning time, instantaneous weight and reference area will do the rest in simulating how the missiles would decelerate. The inputted base drag is just too high for all of the rest, but at least they simulate a more correct drag vs AoA.

-why????? give it time and each missile will get improved, additionally, that would give the Russian missiles more performance than they should have.

-Besides this game isn't about being balanced and there will still be missiles with appropriate drag values such as the phoenix and SD10 anyway.

 

 

Have they designed those fins to have greater overall drag?

-I never said they designed them for this purpose.

 

No! As you've said, that getting closer and closer to transonic, the drag starts increasing more rapidly with a much higher peak than other missiles prove, which is fairly correct so far. Now, are you saying that it should be more draggy than an aim-120 according to your CFD results?

 

But I mean it shouldn't really be surprising that the 77 should probably lose speed quicker:

 

It's a bigger missile with a very high transonic drag for its class. So even if the fins produce less drag than the 120b's the other aspects of the missile such as the larger size, slightly different nose cone shape, large central wings, and all the other small bits such as the datalink antenna bar all add up.

 

The reality shows different. In supersonic, the things stand upside down for the lattice fins compared to other missiles.

-Maybe so I never said that at high supersonic speeds the lattices weren't rather low drag as far as fins go. It's just there's more factors than this that add up.

 

The CD gets slightly lower than the lowest in subsonic (in subsonic the friction drag gives the highest amount for these types of fins).

-yup agreed

 

It's a more complex explanation of how the grid fins can exploit the effects of the attached shockwaves to reduce the overall drag only through pressure distributions. That way it has a lower than subsonic CD. It's at supersonic speeds where the R-77 excels and only when passing through transonic, either accelerating or decelerating, it's drag is indeed greater than for any other missile.

-Yes agreed

 

 

You are only contradicting yourself saying that the heavier ER decelerates faster than an amraam. What is the decelerating G-load? Isn't it the ratio of the speed difference (from an interval), divided by the time it took to decelerate through that interval (which is the deceleration), divided by the gravitational acceleration constant? It is! So, dividing that deceleration force by the product of dynamic pressure and reference area..., you guessed it, the CD pops so you can check it out! You'll find out how great the ER's CD is in game compared to other missiles. And yes, it also has a high speed performance shaped cone, and yes, also it's fore fins are designed for a reduced supersonic CD (another story).

 

-Well I guess its a matter of how much extra drag the ER produces over the amraam.

-An empty amraam weighs around ~238lbs(62.6kg) and as said above an empty 27ER weighs around ~473lbs(79.3kg). Considering these weights I have little doubt that each could get quite slow considering the relative sizes and weights.

 

I don't understand your statement, as the plot you've just showed proves it faster.

 

Well yeah, i never said the current speed of the R77 in-game was correct.

 

Ok, I agree with you then as I've also calculated the wing loading on the AIM-9 (using the projected fins area (as you'd do with an airplane)) and compared it to the AIM-120 indeed it was a couple of times higher (which is very much). But again, even with the cone's induced vortices the aim-120 still proves to have a maximum subsonic lift coefficient of about 1.5 or so. That's waaaay too much. A subsonic CL max of 0.7-0.75 for it should be usually correct in accordance with a reference area of 0.05m^2.

 

I disagree, from a document I have called "Aerodynamic Coefficients Measurement on a model of a Sparrow Aim-7M Missile in the DREV trisonic Wind Tunnel" shows that these values are probably quite a bit higher than .7-.75. DCS currently for the AIM7 uses a value of 1.14 for low Mach numbers.

 

and well... we have IASGATG's work as well

JuZEUMk.jpg

 

What wasn't possible with the A model, but possible with the B (they're aerodynamically the same)? Delay to start tracking the target, or some other limitation? Sorry, just curious!

 

The only differences between the Amodel is that the Bmodel "had a new WGU-41/B guidance section. It had software in reprogrammable EPROM modules, a new digital processor and other electronics updates."

 

For instance, as the speed starts growing from roughly 1000ft/s TAS (about 1097km/h TAS, 0.9M) towards the maximum speed, then decelerate back towards around 1000ft/s, there is NO corresponding/expected fluctuation in the speed function. It's just a smooth straight line during acceleration and a smooth/constant logarithmic curve during deceleration from supersonic to almost subsonic. If a drag coefficient variation would've taken place, the speed increase function should've had a fluctuating curve while passing through the transonic region and the speed decrease function should've also had a fluctuating curve as the curve should've started to deflect downwards between M1.4 (as you've said) or 1562ft/s and around M1.1 or 1227ft/s where the highest drag coef would be taking place (the CD in transonic is roughly 2 to 2.5 times that at Mach < 0.1) and then continue as almost a straight line towards M0.9 and from there on go logarithmic again towards M = 0. At least that's how things go in reality.

 

 

That drawn presented data is most probably illustrative and the speed versus time functions are simplified only to show the speed and range advantages, NOT accurately detailing how the speed rate varies with time as that was not the purpose of their analysis. When you come across various data, you should always use your judgement and knowledge to tell if there's anything wrong and in this case, that data is not reliable for our discussion.

 

The above are actual flyout charts as in this is what the missile does.

 

5V55R:

 

 

kPLBJLk.jpg

W4T1b8Q.jpg

 

 

 

Let's visualize this in terms of drag

4b0mBAP.jpg

 

 

reKeFWl.jpg

 

 

this is just a quick chart generated by a small matlab program I wrote. I basically just had it calculate the drag for the entirety of a flight for the HARM drag curve I had generated. As you can see at the transonic region there is a notable rise in the slope of the drag curve but it's not for a particularly long time

 

Ok, you may be 100% right about it and let's say that, ok, the aim-120 is now the first DCS missile to achieve a more realistic range, but still, what kind of "optimal launch conditions" would the R-27ER need in order to hit a target from 130kms? Again, a Mach 4 closure speed at 12000m proved that the missile starts falling when reaching only 68% of the given range. So, how much of "optimal" is there left? Same goes for the R-77, AIM-9, R-73 and all the rest.

 

From my understanding, those numbers are max launch ranges, not how far it will actually travel. And as such a drag reduction, lift increase, and lift induced drag decrease, would probably allow the ER to hit in the above conditions.

 

Ok, I believe you about the AIM-9 and R-73 AoA limitation during flight, so that's not their actual critical AoA, but a performance holding max AoA, but how people "like" the R-27 and R-77 lift (which I also admit by tests that is about the most accurate) may sometimes have little to do with reality. To give you an example of why "liking" isn't necessarily what it should be, I "like" the AIM-54 being able to have tremendous lift compared to it's wing loading or compared to the R-33 which loses lift much sooner for a similar wing loading (the R-33 seems more realistic anyway), be a very "long legs AIM-120"

 

I'm a bit lost by what you're trying to say here.

 

and be able to maintain lock on targets no matter how far or low below the horizon they are and almost immune to clutter such as the AIM-120, but the reality tells that it was losing a maneuvering target quite easily.

 

The amraam is a PD seeker and really doesn't care that much about ground clutter. In terms of it losing lock on a maneuvering target if you speaking about this as it is in DCS right now this is due to the seeker no having a MPRF mode currently which would significantly reduce the size of the notch (from my best understanding of the sources I've read somewhere in the range of 30-45kts is probably what it is irl). And yes the range (ins bug) and angle off the boresight they can lock are bugs.


Edited by nighthawk2174
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The in game AIM-7 has a full drag curve as in every .1M value has a unique CD value associated with it.

...

 

Thanks for the confirmation about the AIM-7. I haven't tested it. But, even according to this graph there is no visible variation of the negative logarithmic function of deceleration. It's exactly like the previous ones, with no corresponding high deceleration rate variation according to the current speed between 925kts and 595kts or between M1.4 and M0.9. Very good on taking the time to extract data and plot it in Matlab (I also use Mathcad) for the Harm. Perfectly done for the HARM. So ED has worked out some CD variation with Mach for the HARM as your test shows (although the higher drag Mach/speed range should've normally been greater), but at least they've simulated something for the moment. And as I repeat, the first picture of the AIM-7 doesn't prove any similar effects. Please correct me if I'm wrong or I might be missing something, but as long as the deceleration variation is constantly logarithmic with no inflections between some 925 and 595kts, it means that only the dynamic pressure is varying to affect the instantaneous drag, not the CD as well!

 

-From all the info I've ever seen on Russian missiles the current thrust values for all the Russian missiles being discussed (24,27,73,77) are correct as is currently.

-A burned-out R27ER weighs only ~473lbslbs(79.3kg) which considering the size of the missile isn't really that much.

-It has almost double the current lift because the 27 series hasn't been updated yet

 

Copy that, so if you say that they have the right info regarding burn times and specific impulses, all they'll have to do is to finally adjust the resultant max launching range for a conventional condition (ex: both the attacker and target head on at Mach 2 (a Mach 4 closure) at or above 33000ft) by tweaking the aero data alone. Now, sorry but, 473lbs shouldn't be something like 214.5kgs? That's almost 3 times.

 

-? The target was well above the nose of the launching aircraft (who is even very slightly nose down). The course corrections steering dot was almost off the top of the max error circle...

 

Yes, as it can be seen the interception point (the little circle) is still above the F-16's flight path, but I don't know how much above. I remember from your initial post as saying something like 20 degrees or so. Could be then.

 

-The real lift coefficients and max aoa absolutely have been measured and tested in wind tunnels/flight tests but we won't see those numbers for decades.

 

Copy, then only our accumulated knowledge and experience might help estimate those numbers more or less correctly.

 

-why????? give it time and each missile will get improved, additionally, that would give the Russian missiles more performance than they should have.

-Besides this game isn't about being balanced and there will still be missiles with appropriate drag values such as the phoenix and SD10 anyway.

 

Yes, I also had that fear in mind for a moment saying that, thinking that the R-27 and/or R77 might get a too low final drag if their real base drag coefs are somewhat higher than that of an amraam, but I considered saying it though, because as a momentary fix they'll still get them closer to real than being as handicapped (mostly due to drag) as they currently.

 

But I mean it shouldn't really be surprising that the 77 should probably lose speed quicker:

 

It's a bigger missile with a very high transonic drag for its class. So even if the fins produce less drag than the 120b's the other aspects of the missile such as the larger size, slightly different nose cone shape, large central wings, and all the other small bits such as the datalink antenna bar all add up.

 

Agree regarding the antenna bar which isn't so supersonically shaped, but, the long central fins are about the least draggy in supersonic. Don't account only on the fact that the reference area is much greater compared to that of an amraam's fins. In supersonic, the friction drag behind/within the mach cone (or simply behind the highest intensity oblique shock) makes the least of all drag, the major drag contributor being the pressures distribution which affect the shape and positions of the shocks. Having much shorter span and thereby a very low aspect ratio, they are ideal for about the best lift to drag ratio in supersonic (in subsonic, these things are exactly upside down, the higher span versus MAC length or aspect ratio gives better lift/drag), so they may overall be a bit more draggy or the same draggy as the amraam's mid fins (higher reference area than for the amraam, but some lower resultant mid fins CD). I didn't take the time to do some quantitative analysis for this matter, but I only call the rules atm.

 

-Well I guess its a matter of how much extra drag the ER produces over the amraam.

-An empty amraam weighs around ~238lbs(62.6kg) and as said above an empty 27ER weighs around ~473lbs(79.3kg). Considering these weights I have little doubt that each could get quite slow considering the relative sizes and weights.

 

Afaik, a gross ratio between lbs and kgs is 2.205, thus 238lbs = 108kgs and 478lbs = 214.5kgs. Thus the R-27ER has roughly double the amraam's weight. So, in order to have the R-27ER and the aim-120C decelerating in the same fashion (same axial negative G-load, decelerating), with the same inputted minimum CD, the reference area should be double for the ER. As the reference area isn't double, the same CD would have the ER decelerate slower than the amraam for the given weights.

 

I disagree, from a document I have called "Aerodynamic Coefficients Measurement on a model of a Sparrow Aim-7M Missile in the DREV trisonic Wind Tunnel" shows that these values are probably quite a bit higher than .7-.75. DCS currently for the AIM7 uses a value of 1.14 for low Mach numbers.

 

The reference area taken is equally important as you also know. It's all about having the right resultant forces simulated. If the conventionally taken reference area is smaller, then the coefficient will have to "compensate" in order to have the same force resulted.

 

...and well... we have IASGATG's work as well

JuZEUMk.jpg

 

Wow, very valuable data, but I wonder what has been tested for those results to arrive. Either they've used a high reference area while testing a scaled model missile (as this is what we're talking about) or have only tried testing some missile body portions with a non-supersonic performant cone which would normally generate a high CL increase due to wave riding and with no fins at all, otherwise I don't get those very low numbers such as 0.132 a peak value. Speaking of witch, the Cl (that you've referred to in your earlier post) is conventionally named "rolling moment coefficient". I've also had some initial confusions with it, but after working with all 6 coefs (CL, CD, CSL, Cm, Cl and Cn) I haven't mixed them up anymore. I'm not correcting you or anything, but for that moment I thought that you were really trying to also talk about rolling moment coefs based on those graphs.

 

The only differences between the Amodel is that the Bmodel "had a new WGU-41/B guidance section. It had software in reprogrammable EPROM modules, a new digital processor and other electronics updates."

 

Copy that! Thanks!

 

The above are actual flyout charts as in this is what the missile does.

5V55R:

 

 

 

kPLBJLk.jpgW4T1b8Q.jpg

 

 

 

Again, very valuable graphs! Well, here you can see the deceleration function inflection as the missile decelerates through some speed region. Maybe it's only illustrative (not exactly accurate), but you can see on different lines how the speed starts dropping more rapidly below some value (as it seems, below 1000-900 meters/second or M 2.9). It isn't yet a transonic speed (as most logically there is no portion of the missile left with subsonic flow regions) but shows an increase in CD as the speed drops below that range. So sad I don't have the needed money to intend some scaled models testing in a nearby wind tunnel and at least find out some more accurate results even for low subsonic and from there I'll try to extrapolate the results with dedicated maths. The correct 3D geometry is everything, the rest come easier through the required resources.

 

From my understanding, those numbers are max launch ranges, not how far it will actually travel. And as such a drag reduction, lift increase, and lift induced drag decrease, would probably allow the ER to hit in the above conditions.

 

Exactly! max launching distance from attacker to target, not how far the missile can travel in level flight until it can no longer hold 1G against the earth. That's how I also mentioned the max ranges when I've talked about them. Of course, a higher lift for the same drag alone will mean greater Lift/Drag and thus greater range. Reducing the drag besides increasing the lift will, of course get an much higher max range boost. Idk about the lift increasing if it's really a good idea as it already seems to be the most accurate for the Russian missiles, but, idk, it's ED's knowledge and analysis that should do the right thing!

 

I'm a bit lost by what you're trying to say here.

 

Don't take it too seriously then. I was only trying to tell the difference of what people might want/like and what should be real. The fact that I like to abuse and exploit the flawless in game AIM-54's target tracking abilities (identical to the aim-120) to simply score kills one after the other is one thing while in real life these proved effective only in almost perfect conditions with straight flying targets.

 

The amraam is a PD seeker and really doesn't care that much about ground clutter. In terms of it losing lock on a maneuvering target if you speaking about this as it is in DCS right now this is due to the seeker no having a MPRF mode currently which would significantly reduce the size of the notch (from my best understanding of the sources I've read somewhere in the range of 30-45kts is probably what it is irl). And yes the range (ins bug) and angle off the boresight they can lock are bugs.

 

Indeed, but what about the power output? If it can only see a target that's at maximum 8nm away compared to a plane's radar that can see one from 10 times greater, wouldn't that logically mean that it's reduced radiation power will also cause it to lose the target if far enough? Idk, there's indeed also the possibility that they've configured the aim-120 to go "pitbull" only when 8nm out to get close enough to the target without warning it too early, but then why not make it turn on it's seeker and search for the target from 4 or 3nm if the stealth incoming would be a priority? I personally guess that due to it's very small size emmiter/receiver config it can't correctly see/lock aircraft from further away than 8nm (which was set as a generally optimum turn on lock on range).

 

I'm very pleased talking about these things with guys like you!

Regards!

Good knowledge and common sense make the absurd run for defense.

Flying has always been a great interest for mankind, yet learning everything about it brought the greatest challenge!

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Thanks for the confirmation about the AIM-7. I haven't tested it. But, even according to this graph there is no visible variation of the negative logarithmic function of deceleration. It's exactly like the previous ones, with no corresponding high deceleration rate variation according to the current speed between 925kts and 595kts or between M1.4 and M0.9. Very good on taking the time to extract data and plot it in Matlab (I also use Mathcad) for the Harm. Perfectly done for the HARM. So ED has worked out some CD variation with Mach for the HARM as your test shows (although the higher drag Mach/speed range should've normally been greater), but at least they've simulated something for the moment. And as I repeat, the first picture of the AIM-7 doesn't prove any similar effects. Please correct me if I'm wrong or I might be missing something, but as long as the deceleration variation is constantly logarithmic with no inflections between some 925 and 595kts, it means that only the dynamic pressure is varying to affect the instantaneous drag, not the CD as well!

 

The reason I posted the drag force graph was to disprove a point. It appears to me that, -as far as I can tell- you seem to think that at the transonic region the rate a missile is losing speed should increase due to the significantly higher CD value than at high supersonic and subsonic speeds. This graph is meant to show that even at these speeds as your slowing down the drag force continues to drop and does not increase or even level out. So even as the CD increases the fact that the squared factor velocity is still falling will ultimately mean that the drag will too even at these high CD values. This is why you don't see this "inversion" at these speeds. Additionally, the difference between the highest point and lowest point of the large drop off (the point where the CD value falls off after its peak value at M1.2) is 175lbs at the top and 67lbs at the bottom... the amount of force is incredibly small (considering how high it gets at high mach numbers). That's also why I posted the resulting speed vs time chart as well to show that it matches (in terms of shape) what we see in DCS and frankly in that other jet sim as well.

 

 

Indeed, but what about the power output? If it can only see a target that's at maximum 8nm away compared to a plane's radar that can see one from 10 times greater, wouldn't that logically mean that it's reduced radiation power will also cause it to lose the target if far enough? Idk, there's indeed also the possibility that they've configured the aim-120 to go "pitbull" only when 8nm out to get close enough to the target without warning it too early, but then why not make it turn on it's seeker and search for the target from 4 or 3nm if the stealth incoming would be a priority? I personally guess that due to it's very small size emmiter/receiver config it can't correctly see/lock aircraft from further away than 8nm (which was set as a generally optimum turn on lock on range).

 

When looking into terrain the effect this has on PD radars is that it increases the intensity of the background noise which decreases max detection range. But once detected and locked onto maneuvering to place terrain behind you won't break the lock. Rather you either need to break LOS or get into the notch, which when trying to do against a missile that's probably under 5 miles from you would be next to impossible. Partially due to the incredibly high los rates due to the guidance equations. Not to mention if the host aircraft is still providing datalink updates notching ain't going to work at all. But on top of all of that it should be near impossible just due the very small notch's missiles are supposed to have; staying in a notch that's probably in the range of 30-45kts for any period of time that could actually cause the missile to lose you would just be almost impossible.

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The reason I posted the drag force graph was to disprove a point. It appears to me that, -as far as I can tell- you seem to think that at the transonic region the rate a missile is losing speed should increase due to the significantly higher CD value than at high supersonic and subsonic speeds. This graph is meant to show that even at these speeds as your slowing down the drag force continues to drop and does not increase or even level out. So even as the CD increases the fact that the squared factor velocity is still falling will ultimately mean that the drag will too even at these high CD values. This is why you don't see this "inversion" at these speeds. Additionally, the difference between the highest point and lowest point of the large drop off (the point where the CD value falls off after its peak value at M1.2) is 175lbs at the top and 67lbs at the bottom... the amount of force is incredibly small (considering how high it gets at high mach numbers). That's also why I posted the resulting speed vs time chart as well to show that it matches (in terms of shape) what we see in DCS and frankly in that other jet sim as well.

 

Of course that the drag is a product between CD, reference area and dynamic pressure. As the speed drops, if the CD is held constant, the speed will gradually drop with a smooth logarithmic function of 2 (the rate of deceleration decreases and at half-a-speed you'll have 4 times less resultant drag), but if the CD will increase even slightly, say between X2 and X1 speed values, you should have at least a slight noticeable deformation of that function. The higher the CD variation (real CD values are as high as 50% or more in transonic compared to supersonic below Mach 2 (above Mach 2 it rises again due to heat and higher fluid viscosity)), the higher the speed curve fluctuations. Isn't it logical that only for a constant CD you will have a smooth non-fluctuating speed curve? In other words, we can say that varying the CD with Mach you'll get the same result as keeping a constant CD and varying the dynamic pressure's speed's exponent throughout that given Mach range, such as increasing the speed's exponent with the right amount instead of the CD to result a similar drag, the functions would closely overlap, but that's not how it should be, as only the CD should vary through Mach and not the speed's exponent! That's why I repeat, that the way they look from your graphs (except the Harm), both the speed's exponent remains 2 (as it normally should) and the CD remains constant (which it shouldn't), reason why you have that smooth logarithmic curve for speed drop, instead of a slightly more constant speed drop slope or even greater speed drop slope (depends on how much the CD increases) over the higher CD region.

 

And you have the Harm evidence that you have personally shared and we can see how it's speed and drag force (CD times dynamic pressure and ref. area) vary with Mach, even if for a short speed/Mach range, but it is there. If the CD gets higher as the speed decreases, you don't necessarily need to see a greater drag, hence greater deceleration. Although as the CD is about twice greater in transonic than subsonic and about 130-150% greater than supersnoic, it's pretty much possible that a slightly greater deceleration may occur when passing through that highest CD range (I won't say it's for sure, but depending on CD values over Mach range, it's not impossible either). The best way to find out the difference between a constant CD and a variable CD with Mach is to compare two graphs of the same missile, same initial speed, overlap the graphs and see the differences in the speed/Mach versus time.

 

When looking into terrain the effect this has on PD radars is that it increases the intensity of the background noise which decreases max detection range. But once detected and locked onto maneuvering to place terrain behind you won't break the lock. Rather you either need to break LOS or get into the notch, which when trying to do against a missile that's probably under 5 miles from you would be next to impossible. Partially due to the incredibly high loss rates due to the guidance equations. Not to mention if the host aircraft is still providing datalink updates notching ain't going to work at all. But on top of all of that it should be near impossible just due the very small notch's missiles are supposed to have; staying in a notch that's probably in the range of 30-45kts for any period of time that could actually cause the missile to lose you would just be almost impossible.

 

Copy that and thanks for the heads up, but this proves that DCS is kind of behind with these aspects as you can and will always notch every missile for a split second and will also always have it go and stay for chaff if you release it before notching. How much would the chaff (depends on it's quality) affect a missile's tracking ability in different scenarios such as clutter and notching is something hard to tell without plenty of tests I guess.


Edited by 85th_Maverick

Good knowledge and common sense make the absurd run for defense.

Flying has always been a great interest for mankind, yet learning everything about it brought the greatest challenge!

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If the CD gets higher as the speed decreases, you don't necessarily need to see a greater drag, hence greater deceleration.

?

 

it's pretty much possible that a slightly greater deceleration may occur when passing through that highest CD range (I won't say it's for sure, but depending on CD values over Mach range, it's not impossible either). The best way to find out the difference between a constant CD and a variable CD with Mach is to compare two graphs of the same missile, same initial speed, overlap the graphs and see the differences in the speed/Mach versus time.

 

Ok for this test I just used my HARM program, the constant CD value is 0.0615 the average value across the range of M0.57 (rough min speed of a lot of missiles) to M4.0.

 

AeVoJSh.png

Es5goON.png

 

 

Copy that and thanks for the heads up, but this proves that DCS is kind of behind with these aspects as you can and will always notch every missile for a split second and will also always have it go and stay for chaff if you release it before notching. How much would the chaff (depends on it's quality) affect a missile's tracking ability in different scenarios such as clutter and notching is something hard to tell without plenty of tests I guess.

 

Pretty much, DCS is really behind on a lot of stuff related to EW. Not much if at all, the second the chaff drops below the filter speed it will be filtered out, the only thing I could possible see it doing is increasing the base background noise. But I don't think this would actually do much, besides the time the chaff would stay in the tracking cone is so small especially in the beam. Additionally one has to wonder about what kind of radar filtering techniques one could do with the modern electronics on the amraam as well.

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One issue with the russian missiles in DCS is that ED reads the charts from the manuals as maximum aerodynamic range. But those are the maximum launch zones.

In the R-24 manual it is recommended to fire one R-24R at maximum range and another closer. The maximum range shot would be completely useless if it was the maximum aerodynamic range. With a slight headwind the missile would not be able to reach the target if it flew 100% straight.

 

Another issue is that the R-27 charts are very old ones, the missiles have been upgraded several times since. But all ED has access to is old hand-drawn charts from old manuals.

 

R-27ER and ET carry twice as much rocket motor fuel as an Aim-120C5.

 

Against the Aim-120 in BVR the R-27ER should hit the target when the seeker of the Aim-120 is not even active, defeating the ARH advantage.

 

If the empty weight of 214.5 Kg posted above is correct, then the ER carries about 135 Kg of fuel. The Aim-54A carries 163 Kg. Sure, the Phoenix burns the fuel slower and does a loft, but the ER is a much thinner missile. Certainly the current range seems very odd for a missile that has so much energy.

 

I am very curious how the R-27 will perform once ED updated them, they said they want to work on the R-27 this month.


Edited by BlackPixxel
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Another issue is that the R-27 charts are very old ones, the missiles have been upgraded several times since. But all ED has access to is old hand-drawn charts from old manuals.[/qutoe]

 

That is the problem when one needs to go for very well confirmed official documents, and is required to reject a newer data that can't be 100% confirmed to be official.

 

R-27ER and ET carry twice as much rocket motor fuel as an Aim-120C5 while also having almost twice the thrust/weight ratio.

 

I believe you mean half the thrust weight ratio? As AIM-120C is 150kg missile while R-27ER is 350kg missile. So over twice heavier. And even if the missile carries twice as much fuel, it doesn't deliver automatically twice the thrust as it is question how quickly and effectively can that fuel be used for thrust generation.

 

Against the Aim-120 in BVR the R-27ER should hit the target when the seeker of the Aim-120 is not even active, defeating the ARH advantage.

 

Yes. The main difference really being that ARH advantage is that only once the missile seeker goes active, can you turn away from the target, and if you are guiding ARH missile with low update rate (TWS at max scanning volume etc) then you can easily lose a lock on target as well guide missile to wrong place in final moments, that will increase ARH seeker time to acquire some kind target when searching it. So faster SARH missile can be far more deadly if launched well, forcing ARH launcher to break a lock sooner.

 

If the empty weight of 214.5 Kg posted above is correct, then the ER carries about 135 Kg of fuel. The Aim-54A carries 163 Kg. Sure, the Phoenix burns the fuel slower and does a loft, but the ER is a much thinner missile. Certainly the current range seems very odd for a missile that has so much energy.

 

The current range is not just odd by the values, but it is as well by the logic that Russia would depend all their air defense for a missile that is so terrible that it can't even challenge AIM-7M missile in performance wise. Russia has developed all kind various missiles and upgrades to their missiles since 1991, but they would have kept the R-27 family in use because it is bad? As that is like carrying these days a R-3S as there wouldn't have been reason to even take R-73 in operational use. And if the R-27 is so terrible, there shouldn't have been any reasons to ever update AIM-120 as it would have been better from the begin anyways.

 

I am very curious how the R-27 will perform once ED updated them, they said they want to work on the R-27 this month.

 

It will be interesting thing to see, but what is guaranteed is that there will be outbursts regardless what their changes are. Maybe only way for ED to avoid major discussions going around their work, would be clearly explaining all their sources and materials that they use for the modeling and why they exactly believe will be correct as they get it to be after revision.

 

And it just came up to me that has anyone ever tested R-27ER vertical performance? Can it do its claimed 12 km vertical separation launching even?

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Pretty much, DCS is really behind on a lot of stuff related to EW. Not much if at all, the second the chaff drops below the filter speed it will be filtered out, the only thing I could possible see it doing is increasing the base background noise.

 

That is the problem with chaff, that it doesn't "drop below filter speed" at all until it is scattered too large area that its reflection effect in the area becomes negligent. That is why chaff stays up causing serious problems for hours or even days (depending weather conditions and radar beign used) as the chaff scatters and is causing instant velocity spikes constantly even when it is stationary by location (no wind) in sky. That is what makes it possible as well be filtered out as it is serious noise generator, it is constantly moving target by the radar point of view, but then again it is huge wall blocking visibility through it to all directions, as well it is huge target as aircraft. Chaff is very effective by its multiple effects it is causing for even most modern radars and why chaff release ain't permitted in many places even for training purposes.

 

To understand chaff better, it is like if you would have a long road in black night and you have a cat's eyes (reflectors) placed in wider area on the road and they are all one way reflectors and they are all turning and rotating freely in gentle breeze. When you point a strong light on them, you can't make out that at what distance the reflectors really are as they will look to you as some are hundreds of meters away, some are just tens of meters away and it is constantly changing form so you don't even know what size or how many there is.

 

This same thing can be example seen in a normal lights that are made to flicker at semi-fast rate (like 2-5Hz) instead kept lit constantly. In dark when the target is moving, you can't make out its distance as there is no reference to you of its movement and so on not from its distance. The light source can very look to you to be multiple times closer or further from your point of view when you are closing to it at high speed.

 

And the chaff effect will increase wider area it scatters, as now the reflected energy will get measured from the chaff at faster rate moving longer distances almost instantly. So what is the easiest way to do is simply try to ignore completely such a source and go for something else as it is known that fighter doesn't react so unpredictable manner. Combine chaff with proper angle with target and it is hidden. Add there a jammer and it becomes far more difficult as you are now seeing multiple different similar targets and you can't ignore all of them as one is the real one.

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That is the problem with chaff, that it doesn't "drop below filter speed" at all until it is scattered too large area that its reflection effect in the area becomes negligent. That is why chaff stays up causing serious problems for hours or even days (depending weather conditions and radar beign used) as the chaff scatters and is causing instant velocity spikes constantly even when it is stationary by location (no wind) in sky. That is what makes it possible as well be filtered out as it is serious noise generator, it is constantly moving target by the radar point of view, but then again it is huge wall blocking visibility through it to all directions, as well it is huge target as aircraft. Chaff is very effective by its multiple effects it is causing for even most modern radars and why chaff release ain't permitted in many places even for training purposes.

 

This is a myth that keeps being repeated like so many other fallacies on this topic.

 

Chaff hasn't been a serious issue since reasonably sophisticated pulse-doppler radars became available in the 80s. To pulse radars, chaff willl indeed provide serious obstruction until full dissipation. However, with a doppler filter only the initial expansion of chaff will provide a significant return. The reason its not used is because it absolutely murders the effectiveness of pulse-based technology, like air traffic and weather radars over a rather large area (aside from obvious environmental issues).

 

The interaction between chaff and radiation isn't like a solid screen. It will create a large diffuse area of variable reflections, while the radiation just happily continues on to illuminate whatever is behind the chaff cloud. Somewhat modern notch filters will remove this noise just the same way it does ground returns, like the fluttering leaves on trees.

 

For pulse radars this will indeed look like a massive blob of return, for pulse-doppler, all it does is pose a problem of signal-to-noise ratios as all these returns reduce the effective sensitivity of the radar in that area. Radars were already very good at defeating this in the late 80s (range gating, signal enhancement techniques) and have only gotten better in the digital era.

 

As you yourself stated, this is why electronic warfare, stealth and aspect-reducing manoeuvres are so important. Reduce the signal-to-noise ratio as much as possible. Chaff in isolation is almost pointless with modern filtering algorithms and electronics and has been that way since the late 80s.

 

 

Chaff-as-flares as it's simulated in DCS is a pretty reasonable simplification. The main problem here is that aircraft radars are not simulated to get confused by it. Another problem is that chaff itself is effective for far too long (3+ seconds) and seeker cone limits are not simulated. This makes notching missiles trivial, as it pretty much negates the importance of timing.

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[...]

Chaff-as-flares as it's simulated in DCS is a pretty reasonable simplification. The main problem here is that aircraft radars are not simulated to get confused by it. Another problem is that chaff itself is effective for far too long (3+ seconds) and seeker cone limits are not simulated. This makes notching missiles trivial, as it pretty much negates the importance of timing.

I think that's the main issue. It makes no sense for missiles to be so affected by chaff, while the radar of any airframe, no matter the mode, has zero problems with it. Especially missiles with a datalink, supported by a launch platform that has the target in STT and thus ensures continuous position updates. Also, according to your post, since PD radars have little issue dealing with chaff, the AMRAAM shouldn't go for them as much as it does in DCS, since its seeker is PD. Like you say, some missiles are dodged or confused way too easily.

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Yep, the problem with our AMRAAM is that it has only a guidance mode resembling something like high PRF, which means the notch is along the lines of +/- 36 knots closure, even when it's within a mile of your jet. This makes it incredibly easy to notch and force it to lock onto any of the juicy chaff bundles that are still floating within a 5000 or so feet radius.

 

On the SARH end, at least in multiplayer, even momentary loss of lock will cause all FC3 radars in DCS to go completely dumb, since they don't save track information and therefore don't go into memory mode. Active missiles appear to have a scripted behaviour that will pull X amount of lead in the last known direction of the target in a way that bleeds all its energy and almost guarantees it will never reacquire.

I see a lot of people shoving forth their favourite missile as proof that it needs an update or rework, but the simple fact of the matter is that, when it comes to guidance and countermeasures, all missiles are roughly equally easy to spoof. (Chaff resistance really doesn't do much if all it can see is chaff...)

 

 

However, as that's not the topic of this thread, let's stick to discussing drag/lift models. ED has admitted a bunch of times that there's improvements to be made for all missiles and that they're working on it, so idk what the purpose of the rest of this thread could possibly be. Two Weeks™...


Edited by Noctrach
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?

 

Ok for this test I just used my HARM program, the constant CD value is 0.0615 the average value across the range of M0.57 (rough min speed of a lot of missiles) to M4.0.

 

AeVoJSh.png

Es5goON.png

 

 

And where have I contradicted myself when I've stated that in one case it's possible to have a greater overall drag of the missile as the CD increases trough a lower speed range and in another case it's possible to have the overall drag still lower (decreasing) as the CD increases through a lower speed range? Maybe I haven't used the right formulation that the resultant drag may be: higher, lower or about equal as the CD increases through a decreasing speed range along it's trajectory, as it all depends on the dynamics of the trajectory, yet still, usually the drag should get somewhat higher.

 

Finally..., you have made a test and what I've just said is confirmed and I honestly appreciate that you took the time for this test! The speed increase function inflection can be seen on the first graph of this recent test that you've provided. As we can see, with a variable CD with speed, the speed variation curve isn't smooth and has a short change in curvature (if this was the easier way of mentioning it). Simply, that change in curvature gets greater as the CD variation is also greater!

 

Btw, we've both forgotten one important thing, have we? Even if the missile is flying at a constant AoA (let's consider it a low constant AoA or close to zero) and the CD is varying with speed, you'll still get a speed versus distance (or time) curve inflection or local change (as we've just clarified), but what happens in DCS as the missile's AoA is not constant throughout the speed decrease...?

 

The following are the 2 big reasons why the CD will drastically increase as the airspeed drops from any value for a 1G holding vehicle:

 

Reason 1: If you test fire a missile straight without any lock on a target in DCS, it will go straight and it will try to maintain a 1G normal load, right? As the speed decreases, we all should know that the AoA will exponentially start to increase in order to maintain 1G! The usual CD versus AoA function's exponent is roughly 2, thus, at a double AoA, we'll usually get a 4 times higher CD. So, as the AoA on our DCS missile gets exponentially higher as the speed decreases to hold 1G and the drag coefficient also gets exponentially higher with AoA, just think or test (much better to test) how rapidly the CD increases as the speed gets lower, no matter the speed decrease ranges for testing. Even an airplane provides this rule very straight. In level flight, if you throttle to idle, or simply shut off your engines, the more rapidly you'll have to increase your AoA as the speed gets lower in order to maintain 1G or a leveled flight, the more rapidly your speed also drops, which confirms that the drag gets higher, but indeed, this is for the condition of trying to provide a lift equal to weight. If the plane/missile would maintain the same AoA as the speed rops, then the gravity force vector will gradually "thrust" that body forward and reduce that speed drop, but that is logically not the case we're talking here about!

 

Reason 2: The shock stall! Now this is one further very important thing, which is zero modeled in DCS for the transonic region. As it is called, during the normal shockwaves development over the low as well as the high pressure areas around a missile, bullet, plane, whatever, the major disruption and airflow detachment (possibly flow reversal to some degree and in some areas) over the lower pressure region leads to a big chunk of the negative pressure coefficient being "eaten" up by the disruption, thus reducing the global lift coefficient to almost half of what it was before the shock stall. Now, think of this regarding our DCS missiles that want to hold 1G as they pass through the transonic region. The CD at any constant AoA gets higher by default because the speed is entering the transonic range (reaching a maximum at some determined speed), the lift now gets lower and it also reaches a minimum value (which is roughly half that which occurs at M = 0.1-0.2) at some speed throughout the transonic region and the AoA needs to compensate and will roughly double in order to keep to necessary lift for 1G for that condition. All in all, the overall drag force should irrefutably get much higher throughout the transonic region for any missile, plane, UFO (if they would exist and aerodynamics would affect them) or whatever wants to keep a 1G load on the normal axis throughout the speed drop.

 

Here are some useful links:

https://qph.fs.quoracdn.net/main-qimg-29400b8ac2598d8d72e99982d3089195.webp

https://media.springernature.com/original/springer-static/image/art%3A10.1007%2Fs00348-017-2466-z/MediaObjects/348_2017_2466_Fig1_HTML.gif

https://slideplayer.com/slide/6326661/21/images/89/Flight+Characteristics.jpg

 

(just look at that CL max curve around the transonic region)

 

DCS doesn't simulate a CD increase nor a pitch down (known as Mach tuck, from which also another drag increase due to the required trim would occur, separately) on aircraft when passing through the transonic region, so it's quite far to talk about the CL variation in there as well. The only plane which I've found so far to simulate a pitch down increasing moment as the speed gets closer to transonic, is the Su-25. No other aircraft simulates it at all, while some aircraft such as the Su-27/33 simulate it the wrong way around as an increasing pitch up moment (can be noticed as the AoA gets higher by itself) as the speed gets closer to transonic. I ddin't want to veer of the subject, but I felt it was necessary to talk about these things too, at least once if they'll ever be fixed!

 

Now, I didn't initially have the proper time to test that AIM-120C on a similar scenario to this one:

 

 

In this youtube footage, that long "BEEP" is the sound of the trigger being pressed and the missile launched. So, when he said: "Clear to kill...", the pilot squeezed the trigger which caused that long "BEEP" before the operator terminates saying: "...he's a bandit, bandit". That's a bit before 2.0nm away from the target, but this isn't the big thing that helped the missile steer with plenty of "room" (taking into acount both distance and offset angle), but the actual angle which isn't great at all. Here's a picture that I've done just now with the DCS F-16 during the exact moment that the real pilot launched his AIM-120 and in about similar conditions of closure rate, angles, altitude:

Screen_200211_235305.thumb.png.a047684665507ea7f50a50623f284022.png

 

As I've launched the AIM-120C in DCS, in less than 2 seconds it has already acquired the interception trajectory (meaning that no more steering was necessary) and for the later 2-3 seconds, the target got hit. So it had plenty of room anyway. I've also struggled to conduct the same test using the Su-33 with R-27ER and still managed to hit the target (but the ER was still turning towards the interception angle before hitting it), but in order to have the ER start turning at the right moment (to mimic the way the AIM-120 jumps just like an AIM-9 from the wingtip, which it does) all I've had to do was to launch it at the right moment a bit before the 2nm away in order to have it start steering towards the target at roughly 2nm from the target. So if the ER with it's low simulated lift managed to kill it's target from that condition, what to talk about the AIM-120 which did it as if it's an AIM-9 all the way, lol?

 

Basically, the new Aim-120 has a much greater lift to drag ratio, which is wrong! If it would have indeed a greater lift, then so the drag should also increase, but that would be in contradiction with the fact that the drag is already great on all the missiles we have in DCS. What I conclude is that this great lift increase on the Aim-120 is abnormal/unrealistic!

 

Here's the track:

 

Aim-120 vs R-27ER on turning limit.trk

 

Regards!


Edited by 85th_Maverick
Put the words better in context for the 2 big reasons for CD increases as the speed drops at 1G flights

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Now, I didn't initially have the proper time to test that AIM-120C on a similar scenario to this one:

 

 

In this youtube footage, that long "BEEP" is the sound of the trigger being pressed and the missile launched. So, when he said: "Clear to kill...", the pilot squeezed the trigger which caused that long "BEEP" before the operator terminates saying: "...he's a bandit, bandit". That's a bit before 2.0nm away from the target, but this isn't the big thing that helped the missile steer with plenty of "room" (taking into acount both distance and offset angle), but the actual angle which isn't great at all. Here's a picture that I've done just now with the DCS F-16 during the exact moment that the real pilot launched his AIM-120 and in about similar conditions of closure rate, angles, altitude:

[ATTACH]227166[/ATTACH]

 

Ummmm if you look at the video he is not 15 degrees nose up just looking at the elevation of the radar antenna tells us this:

YlcJDbN.png

Additionally the moment it flashes to his hud (right before the splash call) we can see he is just above 23.5K ft with an airspeed of just under 300kts (although this may have dropped a bit since he had begun maneuvering).

zS7V2Wh.png

Can I also add that at 2.0 Nmi in-game the missile actually misses in the above scenario.


Edited by nighthawk2174
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As an aerodynamicist myself, I found the new AIM-120 behaviour to be quite unrealistic. I mostly agree with 85th_Maverick 's points but I would like to add a possible explanation about the first real life aim-120 kill, which seems to match the current AIM-120 model on DCS.

The rocket motor was still burning at the time of impact, meaning that some of the centripetal force needed to turn is actually given by the motor, and not just the fins. The CFD study I found online about the new aim-120 for DCS states that the maximum AOA is 30 degrees, its thrust would be 16700 N and its weight around 150 kg (at launch); while using this data it appears obvious that as soon as 30 degrees AOA is attainable (you don't need to be in steady state flight for this), the missile could turn at 50 g's!!! Which is even above the airframe limit. This means that the real missiles steer mostly in the first second of flight, this is why the real missile hit that MIG-25, not because it had God-level lift. I have personally witnessed (in game) an AIM-120 pulling 14 g's at mach 1.2 while losing speed almost at the same rate as an afterburning fighter. THIS IS INSANE.


Edited by stefasaki

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  • 1 month later...
Su-27/33 is supposed to pitch up with speed increase. It’s the FBW maintaining AOA to mimic a conventionally stable plane.

 

The MiG-15 has great transonic modeling try it if you have a chance

 

Hi,

 

First of all, I'm sorry to have mentioned other things which are of another subject and hopefully I will now not grow it here and turn off-topic. Now, my friend, there is no logical reason why a designer would want his fighter to do phugoids even on a classical hydro-mechanical flight controls systems. Everyone hates to work trimming up and down every time the airspeed varies! If you build a FBW system, you'd normally want to keep your normal G-load constant at varying airspeed according to a given pitch input! At least that's how the FBW system's idea works before and after the Su-27 appeared! I doubt that Simonov wanted to have the Su-27 pilots work the trim up and down instead of focusing on fighting techniques! If you'll find a good enough example for what you consider to be the answer, I'd believe you, on the other hand your answer isn't valid due to the fact that the AoA actually varies wildly with airspeed for both the Su-27 and Su-33 in DCS! And here is the proof:

 

Su-27 (and Su-33) upside down CM vs Mach functions.trk

 

The Su-27 and Su-33 FMs are modeled such that the pitching moment (not only the coefficient, but also the moment) as a function of Mach for every AoA (at least below stall) have an abnormally positive derivative (slope) between 600 to 800km/h IAS. That is the only reason why only these two FC3 aircraft start pitching up like crazy (no known FBW allows that to happen) and that happens only due to the AoA increase while accelerating between 600 and 800km/h IAS. That is the only speed range for which the pitching moment coefficient slope is wrong. Below 600km/h IAS as well as above 800km/h IAS through transonic and continuing in supersonic, the AoA variation tendencies prove rather correct pitching moment slopes. Between 600 and 800km/h IAS there's a problem!

 

On the other hand, the MIG-15 also suffers from the same abnormality! The MIG-15s AoA also constantly increases with airspeed. Even if it would have an all moving elevator it should also be affected by the so called "Mach tuck" effects, but the MIG-15 has a classical fixed horizontal stab and elevator config. Although it's a remarkably well simulated aircraft in all the other areas of it's flight model, sadly it is also plagued by the same issue as the Su-27/33.

 

Regards!


Edited by 85th_Maverick
Error for uploading the track

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As an aerodynamicist myself, I found the new AIM-120 behaviour to be quite unrealistic.

 

 

Right so ...

 

 

 

The CFD study I found online about the new aim-120 for DCS states that the maximum AOA is 30 degrees, its thrust would be 16700 N and its weight around 150 kg (at launch); while using this data it appears obvious that as soon as 30 degrees AOA is attainable (you don't need to be in steady state flight for this), the missile could turn at 50 g's!!!

Not sure how you came up with this. There's no 50g required here.

 

 

 

I have personally witnessed (in game) an AIM-120 pulling 14 g's at mach 1.2 while losing speed almost at the same rate as an afterburning fighter. THIS IS INSANE.

I'm looking at a graph of empirically collected fly-out vs available g data right now, and yep, 14g at 1.2 might be a little high at that speed. But only a little. Depends on altitude and specific missile, including control setup. It is quite far from being insane.

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Ummmm if you look at the video he is not 15 degrees nose up just looking at the elevation of the radar antenna tells us this:

 

Additionally the moment it flashes to his hud (right before the splash call) we can see he is just above 23.5K ft with an airspeed of just under 300kts (although this may have dropped a bit since he had begun maneuvering).

 

Can I also add that at 2.0 Nmi in-game the missile actually misses in the above scenario.

 

Hello again Nighthawk and I'm happy to have your replly!

 

Well..., indeed the radar antenna is indeed at +15 degrees in the picture you have provided, but the actual "beeeep" tone for the missile being launched takes place when the antenna is exactly at +12 degrees and the F-16 is slightly climbing from the earlier altitude of 23500ft+. During some new trials in which I tried to replicate the footage events I am usually some 1000ft higher (at around 24500-24700ft) when I'm about to launch it from 2.5nm away.

 

For whatever reason, I thought that the missile fired in that footage is the AIM-120C, but no, in it's most probably the A model for that time! Even the B model was delivered later than 1992 when this footage took place. The A model will have somewhat greater maximum lift at critical AoA, even though the crit AoA may be 1-2 degrees lower due to the higher fins aspect ratio (it matters quite much).

 

Now, lol, exactly as you state in your last sentence, that if you try to replicate those conditions, the AIM-120C won't even hit, but will pass behind the target completely missing it. The same happened to me, such as even if I tried shooting from 2.5nm away from about 24700ft (due to the slow climbing that I tried to mimic) when the radar antenna shows +11..12 (not +15 which is even worse), the aim-120C instantly turns up towards the target and misses it badly. But..., if you will try to replicate the scenario using just the HUD data (the circles displacements), you will not only hit with the AIM-120C, but easily with the rather more realistic turning R-27ER as well. So, what is your thought about this?

 

My guess is that there either was something wrong with that particular F-16's radar antenna indication versus what the HUD data was showing (which seems to be the most reliable/correct) or our DCS F-16's radar antenna indication is wrong according to the target's displacement relative to the HUD data indication. I don't know! We have to agree that there's something weird here, but my guess is that there was no logical reason for that real pilot to believe that his missile will hit a target at 1200KIAS closure speed from a 10 degrees up from that high altitude and that very low air density from just 2.5nm away and think that the missile would hit. I strongly doubt that that's what the pilot had in mind and it's more than common sense that he had the target above him EXACTLY according to the HUD's indication, just touching the upper side of the HUD when he fired at it, not some 2 HUD heights above and hoping to have the missile turn for it as that wouldn't make any sense for a trained pilot as even his instinct would tell him that he'll miss!

 

Here are 2 more tracks that I've done to confirm what I say:

 

In this track you'll see how the AIM-120C misses badly from those impossible condition. Now I don't want to be misunderstood, but EVERYONE with a bit of common sense and even someone who has nothing to do with aviation or physics knowledge would doubt that a missile can be launched from this condition and hit that target:

DCS AIM-120C's test according to the unreliable RADAR footage indications.trk

 

There is one very important clue regarding the spatial displacement (horizontal and vertical distances through which the missile had to maneuver), which is the time it took since the missile was launched until it hit the target according to the pilot's "SPLASH" confirmation. From 2:32 the missile was launched, while at 2:41 the pilot confirms the hit. If we would estimate that the pilot was about 1 second or so late to confirm the hit, then the missile took 8 seconds from launch to hit. That tells a lot! It tells that the missile has more than plenty of room and time to intercept the target. In the following track in which I've used only the HUD indication and tried to match it as well as I could with that footage's real HUD indication, both the AIM-120C and the R-27ER took around 5 seconds from launch to hit and the results talk for themselves as the R-27ER turns then goes straight for at least one second before hitting the target flawlessly!

 

DCS AIM-120C's test according to the more reliable HUD footage indication.trk

 

Regards!


Edited by 85th_Maverick
The footage missile is in fact an AIM-120A and it had 8 long seconds of room to intercept

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You're making some pretty huge assumptions. A ~4sec flight time is expected in an head on situation at 2nm distance. There's literally zero reason to make assumptions with respect to when the splash call was made for accurately timing missiles.

 

 

The pilot is turning away from the target hard, he needs time to roll out and get eyes on again. The splash may have been called by the wingman, who also has to keep an eye on his lead and maneuver with him.


Edited by GGTharos

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Also, 85th_Maverick, you are assuming that the DCS DLZ calculations for ASE/ASEC are the same as IRL, which is a big assumption. Otherwise, you have no reason to believe that an edge of the envelope shot by ASE/ASEC standards in DCS and IRL would be the same.

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You're making some pretty huge assumptions. A ~4sec flight time is expected in an head on situation at 2nm distance. There's literally zero reason to make assumptions with respect to when the splash call was made for accurately timing missiles.

 

The pilot is turning away from the target hard, he needs time to roll out and get eyes on again. The splash may have been called by the wingman, who also has to keep an eye on his lead and maneuver with him.

 

Hello Ms. Tharos, yes I agree with you that my assumption of how quick he may have called the splash or not may be too erroneous, but honestly let's also use a bit of reasoning here. Ok, I take your word that it takes about 4 seconds to kill a head on target from 2nm at 1200 closure speed, but..., if the F-16 was at only around 300KIAS (about 445KTAS at 24500ft at ISA) and the closure rate was 1200KTAS, then the MIG-25 would've had roughly had 462KIAS (755KTAS) and in that condition do you want to tell me that at a density of roughly 0.45 times that at sea level and starting from just 300 KIAS (~550km/h IAS), the initially heavy AIM-120A (as I did a bit of searching I concluded that most BVR missiles weight about half after depleting their propellant) that needs to fly straight for less than a second (it's logically not programmed as a sidewinder to start turning just 2-3 meters after coming off the rail) then start turning with that great dynamic pressure handicap towards a target that would now already be more than 15 degrees up (if you use just and only the radar information form that footage) and within that a very low radius circle available it would have the needed lift (quite tremendous if you'd try to make some tests) to do about 100 degrees of turn in order to intercept the target? Sorry to say, but that's something only out of HAWX or probably ACE COMBAT, not out of a serious flight sim! So it can't be that the target was 12..15 degrees up when the F-16 fired the missile from 300KIAS, cause even with this already absurd AIM-120B/C aerodynamic (not including the thrust component) lift alone that is now used in DCS it can't hit the target from such given conditions even if you fire the missile from much higher initial airspeed that will help it correct the interception course before it's too late. I tried from more than 460KIAS to shoot using just that radar footage info (the track is in my above reply) and still misses by passing behind the target. The more reliable data that I consider worth for our discussion is the HUD like information show on the same monitor as the radar data. If you'd wanna replicate the same conditions by using only the relative position between the smaller interception circle next to the AIM-120's type circle, you will have a much lower and reasonable angular displacement through which the R-27ER will also have the needed room to maneuver and correct it's interception path.

 

I've calculated that the maximum aerodynamic lift coefficient for both the AIM-120C and B which is used in DCS 1.4 (for C) and 1.5 (for B) respectively for a reference area that seems to be used in DCS (which includes more than the wetted fins projected area) of around 0.16m2 for the AIM-120C (0.4 squared is used in the AIM-120C's data) and 0.25m2 respectively for the AIM-120B (0.5 squared being used in the data file) are around 2 times greater the regular ones they both should have. For instance, in the "missiles_data.lua" file, the AIM-120C must have a maximum aerodynamic lift coefficient of 0.7..0.71, while the AIM-120B must have it at 0.73 in order to have the missiles start falling at the correct IAS. According to what I was able to obtain, the AIM-120C should start falling (normal G-load falling below 1 at critical AoA) at around 421km/h IAS while the AIM-120B should do that at around 380km/h IAS. The critical subsonic AoA (the sim uses just one number for any type of speed regime) of the AIM-12C should normally be around 26 AoA (0.46 in radians), while the critical subsonic AoA for the AIM-120B should normally be around 24 AoA (0.43 rads). Although it may not seem much of a difference, it's important that the critical AoA is also realistic, or the missile's performances will move away from being accurate as the thrust induced lift will be quite affected. People, don't self-blind your own knowledge and minds through CFD, it will foul you big time if you don't sort right out of wrong!

 

I'll later discuss with you guys about what else I have found in that very important file, both the good and the not so good numbers!


Edited by 85th_Maverick

Good knowledge and common sense make the absurd run for defense.

Flying has always been a great interest for mankind, yet learning everything about it brought the greatest challenge!

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Also, 85th_Maverick, you are assuming that the DCS DLZ calculations for ASE/ASEC are the same as IRL, which is a big assumption. Otherwise, you have no reason to believe that an edge of the envelope shot by ASE/ASEC standards in DCS and IRL would be the same.

 

 

Hello "Dundun", I don't know what do you mean by ASE/ASEC (sorry I don't know all the acronyms), but as I've replied before, in order to get better results, we should try to simulate the same conditions as in that footage using only the circles displacement reference instead of the radar antenna reference while keeping all the other conditions similar and you'll get more reasonable to believe results than thinking that you can fire a missile from that altitude, closure rate, vertical displacement and offset angle (12 to 15 degrees given only by the radar antenna indication) and hit something. It won't work even with this exaggerated amraam lift that we in DCS today, which should be enough to tell that something's absurd!

Good knowledge and common sense make the absurd run for defense.

Flying has always been a great interest for mankind, yet learning everything about it brought the greatest challenge!

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