Operational Performace Comparison: Viper, Beagle, and Stubby

The F-35 compared with other modern jets.
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gta4

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Unread post17 Sep 2019, 16:56

If the deflection of upper air-intake could generate more lift for the fuselage,

It is safe to assume F-15 has been benefiting from this effect for ages.

Anyone has heard that?
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sprstdlyscottsmn

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Unread post17 Sep 2019, 17:23

gta4 wrote:If the deflection of upper air-intake could generate more lift for the fuselage,

It is safe to assume F-15 has been benefiting from this effect for ages.

Anyone has heard that?

The upper intake on an F-15 does the exact same thing as the Levcon on the Su-57. It has even been credited with helping reduce the tail size needed for teh horizontal stabs.
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garrya

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Unread post17 Sep 2019, 17:26

sprstdlyscottsmn wrote:First, ricrunes is dead on in his assessment above. It's not about the speed difference between the two planes, it is about the absolute speed of the SR-71 and the inability of the R-40 to engage it. As he pointed out, once the MiG-31 came online SR-71s were effectively stopped.

I understand that for head on shoot the closure rate is too high for the missile to handle but how come R-40 doesn't have enough velociy to overtake SR-71?.AFAIK, it is the fastest air to air missile ever made

sprstdlyscottsmn wrote:Now, on to the question of who can reach who first and by how much. Let's start with the assumptions.
Detection:
Zaslon-M locks a 7m^2 target in a jamming free environment at 105nm.
SABR locks a 35m^2 target in a jamming free environment at 87.3nm,
If we are being honest, no one here is taking the 150nm shot, that is only going to be Eagle vs Foxhound. Here, Foxhound gets first shot.

Thank you for the calculation
TBH, SABR feel like such a handicapped for F-16 compared to APG-81. Since the number of produced Mig-31M and F-16 block 60 are equal, can we try the simulation with it too?
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sprstdlyscottsmn

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Unread post17 Sep 2019, 17:37

garrya wrote:I understand that for head on shoot the closure rate is too high for the missile to handle but how come R-40 doesn't have enough velociy to overtake SR-71?.AFAIK, it is the fastest air to air missile ever made

It's credited with a 4.5M top speed, but only a 45nm flight range. It will only be over 3.5M for maybe 10nm. with an average speed over that 10nm assumed to be 4.0M it needs roughly 16 seconds to cover that distance. That also leaves is a closure rate with a tail chase SR-71 of no more than .8M, possibly much less. 0.8M for 16 seconds is 2nm. The SR-71 would cover 8nm in the time the R-40 covers 10nm. After those distances the R-40 will be slower than the SR-71.

THAT is why the MiG-25/R-40 was useless. A MiG-25 was incapable of getting within 2nm, co altitude, of the SR-71. That is contempt of engagement.
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garrya

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Unread post17 Sep 2019, 19:44

sprstdlyscottsmn wrote:It's credited with a 4.5M top speed, but only a 45nm flight range. It will only be over 3.5M for maybe 10nm. with an average speed over that 10nm assumed to be 4.0M it needs roughly 16 seconds to cover that distance. That also leaves is a closure rate with a tail chase SR-71 of no more than .8M, possibly much less. 0.8M for 16 seconds is 2nm. The SR-71 would cover 8nm in the time the R-40 covers 10nm. After those distances the R-40 will be slower than the SR-71.

THAT is why the MiG-25/R-40 was useless. A MiG-25 was incapable of getting within 2nm, co altitude, of the SR-71. That is contempt of engagement.

This part I don't understand. AIM-120 is often credited with Mach 4 top speed and 160 km max range, but we know it can be much faster or slower depending on launch altitude. So why R-40 launched by Mig-25 no less, is limited to Mach 4.5 top speed?. Shouldn't it capable of Mach 7.3 or close?. I always thought that R-40 doesn't have insane range because it put all in speed and acceleration. But with 4.5M top speed when release from Mig-25 at 75k ft, it is very terrible
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Unread post17 Sep 2019, 20:02

garrya wrote:This part I don't understand. AIM-120 is often credited with Mach 4 top speed and 160 km max range, but we know it can be much faster or slower depending on launch altitude. So why R-40 launched by Mig-25 no less, is limited to Mach 4.5 top speed?. Shouldn't it capable of Mach 7.3 or close?. I always thought that R-40 doesn't have insane range because it put all in speed and acceleration. But with 4.5M top speed when release from Mig-25 at 75k ft, it is very terrible

That's just it. R-40 is listed as having a top speed of Mach 2.2-4.5 and a range or 50-80km. The ONLY LAUNCH PLATFORM is already the MiG-25/31. That is a huge difference between the R-40 and the AIM-120. The AIM-120 can be fired from a .85M at 30,000ft aircraft or a 1.8M 50,000ft F-22. Also, AIM-120 lofts, R-40 doesn't. The R-40 is an old and obsolete missile. This is similar to trying to compare an AIM-7 to an AIM-120 and wondering why when they both have the same listed top speed why teh AIM-7 is such a short range missile when it is so much heavier and should therefor have more fuel.
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Unread post18 Sep 2019, 00:57

The Japanese already explored expanding the flight envelope of the AIM-7 and adding an active seeker. Once they were allowed AIM-120 it pretty much was unnecessary.
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Unread post18 Sep 2019, 01:03

gta4 wrote:The impact on thrust of flat nozzles:

Check AIAA report AIAA75-1317 and 76-626.

flat nozzles drastically reduces drag of the aft body.

Thanks for the references, I will try to check them out. I have to admit I am a bit sceptical as to the overall effect, since we only see this kind of nozzles on planes where stealth is required. Manufacturers have done many tests, as shown above, and they still stick to the cylindrical ones, even after having the flat ones already implemented in the series (like LM with the F-22 and then F-35). Admittedly maybe due to other reasons like cost, complexity and weight.

Question: makes sense to use the TVC at supersonic, beyond trimming? I mean, TVC below corner velocity makes clear sense, at supersonic the control surfaces should have plenty of airflow to be beyond effective, right?
If the deflection of upper air-intake could generate more lift for the fuselage,

It is safe to assume F-15 has been benefiting from this effect for ages.

Anyone has heard that?

Here in the forum there is at leas a thread about that

viewtopic.php?f=36&t=53492

The inlet indeed seems to follow the AoA, there is a good video in the thread linked to see it in action from the cockpit. It is limited to +4/-11º though. Smart feature with many advantages 8)

@Spurts: looking forward to the results of the new Mig-31 vs F-16 run.

BTW, I revisited previous MiG / AMRAAM simulations
- If the MiG can now turn 1.3 deg/s, wouldn't its turning radius be slightly tighter than that of the AMRAAM? I remind it was like 18.8 nm when launched form the fast & high F-22.
- In that case, wouldn't a sequence of turns allow the fighter to out-turn the missile?
- The table that garrya linked from a Yefim Gordon's book gives 3.27 g max overload, 1.1 deg/s sustained and 2.7 deg/s max turning rate @17 km, 2.2 M for the MiG. Does it make sense / help with the sims?

In general, I am left under the impression that maneuverability (in a broad sense) is still simply crucial, despite all the arguments against it, in order to defeat missiles. Also very interesting, the different ways they can be fought, some by climbing, others by descending, not even to talk about ECM and other resources. Now I understand why the militaries do not state "real" figures for the capabilities of almost any piece of hardware, since accurate calculations would allow the enemy to prepare effective tactics against them, and as we see the difference between victory and defeat is sometimes very small.
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Unread post18 Sep 2019, 03:28

In “Modern Fighter Aircraft Design” by Klaus Hueneke, it was noted that widely spaced engines (F-14, Su-27, Su-57) have lower transonic drag, but this configuration had great supersonic base drag. A closely spaced engine configuration (F-15) has lower supersonic drag, but the flow turbulence around two round nozzles is extreme. The F100 engines on the F-15 and the F110 engines on the B-1 were removed for supportability reasons since they were beat to death and kept falling off in flight.

The two closely spaced 2D nozzles on the F-22 resolves this issue, giving both low transonic drag / flow turbulence and low supersonic base drag.

During development of the F119, one of the issues was airflow leakage that reduced the coefficient of discharge of the nozzle below expectations. A significant amount of effort went into making sure that all of the engine flow went out the nozzle and not as low energy leakage flow outside the nozzle
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Unread post18 Sep 2019, 09:38

sprstdlyscottsmn wrote:That's just it. R-40 is listed as having a top speed of Mach 2.2-4.5 and a range or 50-80km. The ONLY LAUNCH PLATFORM is already the MiG-25/31. That is a huge difference between the R-40 and the AIM-120. The AIM-120 can be fired from a .85M at 30,000ft aircraft or a 1.8M 50,000ft F-22. Also, AIM-120 lofts, R-40 doesn't. The R-40 is an old and obsolete missile

AA-6 kinematic is worse than I expected, its rocket can only accelerate Mach 2 over that of the launcher aircraft
R-40.PNG


You raised a very good point that I didn't pay attention to, thanks to loft, AMRAAM can coast in thin air. Even for AMRAAM shoot from 35k ft, the missile spends the majority of coasting time above 75k ft.
2.PNG
Last edited by garrya on 18 Sep 2019, 09:52, edited 1 time in total.
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Unread post18 Sep 2019, 09:46

southerncross wrote:In general, I am left under the impression that maneuverability (in a broad sense) is still simply crucial, despite all the arguments against it, in order to defeat missiles. Also very interesting, the different ways they can be fought, some by climbing, others by descending, not even to talk about ECM and other resources. Now I understand why the militaries do not state "real" figures for the capabilities of almost any piece of hardware, since accurate calculations would allow the enemy to prepare effective tactics against them, and as we see the difference between victory and defeat is sometimes very small.


Yes, I agree with you that for the discussion at hand at least for an initial part, we should discount ECM for now - but of course, in the end it will always be a major player regarding the subject.

Regarding what you mentioned above, I still think that you're minimizing the effects and the (huge) advantage of "lead pursuit".
"Lead pursuit" which in simpler terms is basically the ability for the missile to predict/guess where the aircraft will be, means that the missile won't have to turn nearly as sharp as the target/aircraft does because and again the agility for the missile to know where the aircraft will be together with the fact that the missile is located farther away from the target/aircraft (although flying towards it) means that the missile will never need to perform the same/similar angular turns as the target/aircraft will need to or can do (not even close).
Now if you were talking about older "pure pursuit" missiles you would be right. But there are reason why modern missiles are far more deadly than older missiles and one of the main reasons (albeit not the only) is precisely the "lead pursuit" capability.

Then you mentioned an "alternative tactic" which would be to make different (and perhaps erratic) maneuvers such as up followed by down (or vice-versa) or left followed by right (or vice-versa) or any combination of such turns/maneuvers in order I imagine to fool the incoming missile's "lead pursuit" calculations.
But for this, I believe that you should see things from the missile's perspective instead of the target/aircraft aircraft's own perspective:
If the aircraft starts banking up/down/left/right and so on the aircraft will actually lose speed/energy and the missile which is flying towards but farther away from the target what will it see? IMO, it will see the target/aircraft on the same/similar relative position which means that missile will have an easier time to intercept/destroy the target instead of the opposite.
I hope to have explained my point clearly/well?
A 4th/4.5th gen fighter aircraft stands about as much chance against a F-35 as a guns-only Sabre has against a Viper.
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Unread post18 Sep 2019, 10:00

garrya wrote: AA-6 kinematic is worse than I expected, its rocket can only accelerate Mach 2 over that of the launcher aircraft


I believe that there's another issue against the AA-6 which goes in-line with what I previously mentioned which is "lead pursuit" or more precisely the lack of it.
I don't think that AA-6 is capable of "lead pursuit" at all. I believe that the AA-6 is a "pure pursuit" missile which makes things even worse (and on top of what was already said about it) against an "opponent" such as the SR-71.
A 4th/4.5th gen fighter aircraft stands about as much chance against a F-35 as a guns-only Sabre has against a Viper.
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Unread post18 Sep 2019, 10:54

ricnunes wrote:Yes, I agree with you that for the discussion at hand at least for an initial part, we should discount ECM for now - but of course, in the end it will always be a major player regarding the subject.

Sure ECM is very important, yet I think if there is a possibility for a kinematic defeat it will be used with preference, ECM as far as I understand it leaves a "grey zone" where the pilot may not know whether the countermeasures are working and that is not a comfortable situation when your life is on the line.
Regarding what you mentioned above, I still think that you're minimizing the effects and the (huge) advantage of "lead pursuit"...
Then you mentioned an "alternative tactic" ...
If the aircraft starts banking up/down/left/right and so on the aircraft will actually lose speed/energy and the missile which is flying towards but farther away from the target what will it see? IMO, it will see the target/aircraft on the same/similar relative position which means that missile will have an easier time to intercept/destroy the target instead of the opposite.
I hope to have explained my point clearly/well?

The possible tactic I mentioned above was just trying to take advantage of a hypothetical tighter turn radius for the fighter vs. the missile in very thin air, in conditions where the former has time for at least two manouvers, which still is not a given.

We have a head-on engagement where the missile is being guided towards the fighter and the later detects it, starting an evasive turn right. As you say, lead pursuit allows the missile to comfortably catch the fighter, even when it has a tighter turn radius, because due to the thin air the respective turn circumferences are going to be comparably big and meet each other. Now, if once the missile has started turning to undercut the fighter's heading, the fighter turns the opposite way, the missile may need a tighter turn radius or it will loose the target, despite being able to see it and predict its future position, it is simply out-turned (turning circumferences do not meet anymore, and the missile loses speed much faster than the plane). Needless to say that the fighter pilot needs to show surgical precision while performing the manouver or he will fail. It could be even more complicated, if the missile can artificially slow itself for tighter turning radius, but I am unaware if that is doable / done at all, since speed loss practically means failure for the missile. The field of tactics is incredibly rich, that is clear.

@f119doctor: very interesting, thanks
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Unread post18 Sep 2019, 11:32

garrya wrote: AA-6 kinematic is worse than I expected, its rocket can only accelerate Mach 2 over that of the launcher aircraft


I think the kinematic performance of R-40/AA-6 was pretty impressive actually given that it was SARH missile (or IR) with very direct flight path as there was no way of using lofted profile for example. I don't think even AIM-54A had much better top speed although it definitely had longer range due to much more advanced guidance and flight profile.

But sure SR-71 would've been very difficult target for MiG-25 with R-40 missiles.
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Unread post18 Sep 2019, 13:10

southerncross wrote:Now, if once the missile has started turning to undercut the fighter's heading, the fighter turns the opposite way, the missile may need a tighter turn radius or it will loose the target, despite being able to see it and predict its future position, it is simply out-turned (turning circumferences do not meet anymore, and the missile loses speed much faster than the plane). Needless to say that the fighter pilot needs to show surgical precision while performing the manouver or he will fail.


Yes, I agree with you here. So yes, it should be "technically possible" for a pilot to make the right turn exactly at the right time in order to evade a missile but as you correctly said this is extremely hard to do, or using your own words a "surgical precision" maneuver is required for this.
This gets even more complicated with the fact that when missiles (namely BVR missiles) are approaching the target the missiles doesn't leave a plume so that the pilot can have a good reference point to perform the evading maneuver and newer missiles like the AMRAAM hardly leaves any plume (even in the early stages of flight) and moreover, I doubt that sensors like MAWS can give such a very precise cue to the incoming missile position/reference in order for the pilot to be able that already and otherwise extremely hard turn/maneuver (well perhaps if the missile could be shown on a Helmet Display System this could help a bit but again, only a bit).


southerncross wrote:It could be even more complicated, if the missile can artificially slow itself for tighter turning radius, but I am unaware if that is doable / done at all, since speed loss practically means failure for the missile. The field of tactics is incredibly rich, that is clear.


Actually that kinda happens. When the missile is getting closer to the target (I would say that this is more noticeable with BVR missiles but also happens with WVR missiles) the rocket fuel is already exhausted so the missile when closing to the target/aircraft is already "gliding" (I know this isn't the accurate term but I hope that it's enough to get the idea) which means that turns that the missile will perform close to the aircraft will actually reduce the missile's speed.
Or resuming, while the missile doesn't actually reduce its speed "by itself", any missile turn on the later stages of flight will/should result in an actual speed reduction on the missile (a turn will result on the missile bleeding some of its speed when flying unpowered).
A 4th/4.5th gen fighter aircraft stands about as much chance against a F-35 as a guns-only Sabre has against a Viper.
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