MiG-29S EOS flying at 4000m not detecting F-15 that's straight hot and very low

[TAW_Blaze]

 

I'm not sure it works that way bud...

 

Picture perfect representation of my IRL reaction when I read it. :megalol:

[Frostie]

Picture perfect representation of my IRL reaction when I read it. :megalol:

 

Not for me, until GG stepped in I was considering attaching giant fins to my car to reduce drag and save a fortune on fuel.:smoke:

[GGTharos]

+1 Frostie

[TAW_Blaze]

Not for me, until GG stepped in I was considering attaching giant fins to my car to reduce drag and save a fortune on fuel.:smoke:

 

Hang on a second there. Following this logic the airbrake is bugged. It should slow down the plane when it's in retracted position. :D

[DarkFire]

Incidentally, I imagine the 27ER reaches M4.5 easily with high altitude, high speed launches :)

 

Indeed it does. I've managed to get an R-27ER to 6,200 Km/h by launching at M2.56 at 13,500m altitude. I think this was M5.82. Interestingly the aerodynamic range of the missile was an impressive 84Km.

Edited July 4, 2016 by DarkFire

[JunMcKill]

Indeed it does. I've managed to get an R-27ER to 6,200 Km/h by launching at M2.56 at 13,500m altitude. I think this was M5.82. Interestingly the aerodynamic range of the missile was an impressive 84Km.

 

Lol, yeah is mach 5.83! read below

 

Altitude (MSL) 13500 meters

 

CAS (Calibrated Airspeed) 2788.649385123618

 

Mach 5.836665158985399

 

TAS (True Airspeed) 6200

 

EAS (Equivalent Airspeed) 1498.2417633620958

[GaryIKILLYOU]

this entire thread. wow.

[DarkFire]

For comparison, I took an F-15C up to 45,500 feet and launched an AIM-120C. At the point of launch the F-15C was at 2,607 Km/h = M2.45. The AIM-120C reached a maximum speed of around 6,060 Km/h = M5.70. The aerodynamic range of the missile was a very impressive 118Km.

 

Conclusions? Without looking at published data I'd say that the motor on the 27-ER is probably more powerful, giving it significantly higher acceleration and marginally higher top speed, but the AIM-120C appears to have significantly less drag and therefore more range.

 

As both missiles currently are in-game, the AIM-120C also appears to have a more 'sensible' flight profile, though I can't seem to easily find any reliable published information on missile flight profiles.

 

Interesting test. By the way, this was something like my 4th flight ever in an F-15C so my piloting will necessarily leave a bit to be desired in terms of quality!

 

Edited to add: just realised what I've done. Wasn't intending this to become yet another R-27 v AIM-120 thread :(

[JunMcKill]

LOL, dont worry we all know about the F-15/UFO capabilities in DCS! :pilotfly:

 

For comparison, I took an F-15C up to 45,500 feet and launched an AIM-120C. At the point of launch the F-15C was at 2,607 Km/h = M2.45. The AIM-120C reached a maximum speed of around 6,060 Km/h = M5.70. The aerodynamic range of the missile was a very impressive 118Km.

 

Conclusions? Without looking at published data I'd say that the motor on the 27-ER is probably more powerful, giving it significantly higher acceleration and marginally higher top speed, but the AIM-120C appears to have significantly less drag and therefore more range.

 

As both missiles currently are in-game, the AIM-120C also appears to have a more 'sensible' flight profile, though I can't seem to easily find any reliable published information on missile flight profiles.

 

Interesting test. By the way, this was something like my 4th flight ever in an F-15C so my piloting will necessarily leave a bit to be desired in terms of quality!

 

Edited to add: just realised what I've done. Wasn't intending this to become yet another R-27 v AIM-120 thread :(

[SinusoidDelta]

For comparison, I took an F-15C up to 45,500 feet and launched an AIM-120C. At the point of launch the F-15C was at 2,607 Km/h = M2.45. The AIM-120C reached a maximum speed of around 6,060 Km/h = M5.70. The aerodynamic range of the missile was a very impressive 118Km.

 

Conclusions? Without looking at published data I'd say that the motor on the 27-ER is probably more powerful, giving it significantly higher acceleration and marginally higher top speed, but the AIM-120C appears to have significantly less drag and therefore more range.

 

As both missiles currently are in-game, the AIM-120C also appears to have a more 'sensible' flight profile, though I can't seem to easily find any reliable published information on missile flight profiles.

 

Interesting test. By the way, this was something like my 4th flight ever in an F-15C so my piloting will necessarily leave a bit to be desired in terms of quality!

 

Edited to add: just realised what I've done. Wasn't intending this to become yet another R-27 v AIM-120 thread :(

 

I had a look at the acmi and plotted the flyout. The 120's flight path is good....when it's fired unguided. There is a very slight loft, basically level flight, and altitude drops off sharply below mach=1.5.

 

Fire the 120 (or any missile, same conditions) with guidance and compare the result. It's as if the missile guidance/control is trying to bleed off as much energy as possible.

 

Edited July 6, 2016 by SinusoidDelta

[D4n]

the one that you talked in your post (see below)

 

"And LOL his AMRAAM going from

- 640 km/h (TAS) to 1430 km/h in just 2 sec.

- to 1820 km/h in 3 sec

- 2160 km/h in 4 sec 2510 in 5 sec

- 2930 in 6 sec?"

 

I meant the one from 10:22:52, launched from 343,5 m ASL, 110,6 m AGL. But why did you ask? Why calculate TAS if Tacview gives the values? (Or you want to calculate if the values are realistic?)

 

 

What is not known are other rocket motor optimizations, such as the construction of the nozzle.

 

Ah so it isn't known which shape the nozzles have? (I thought star shape is most effective shape, when looking at missile nozzle from the back?) And which other factors do you mean by "rocket motor optimizations" ?

 

 

Also rough or exact fuel composition of the AIM-120C (or any) and R-27 ET (or T, in case T and ET have different fuel mixture?) are completely unknown or is sth. published?

 

 

What you just said made absolutely zero sense.

 

 

But isn't "drag" the values of the wings of the missile when they try to make the missile turn into a direction (after engine-cutoff) that how much cm² of control-surfaces will push the air? (To calculate how much force the control surfaces and wings will push with on the missile body to push missile into new direction in the maximum control-surface angle, meaning the control-surfaces missile will push the missile as hard as possible towards a direction) I would expect for example that maximum control surface angle is 45° (higher angle would slow down missile too much?)

 

 

If drag isn't this what I mean, I'm sorry for the confusion. (Thx for the VERY funny picture above, though, JackBauer xD) And I think Obama would forgive me xD

 

 

i wonder how much you would bitch if you flew a mig 21....

 

At least I wouldn't try flying it vs. an F-15, even with Sparrows (which iirc have longer range than any MiG-21 missile)...

 

 

Not for me, until GG stepped in I was considering attaching giant fins to my car to reduce drag and save a fortune on fuel.

 

At least you could drift without fearing to flip your car! :D xD

 

 

And I just found it, how to calculate the drag coefficient by using dynamic pressure! :D

 

 

We have all numbers we need (if we know the exact sizes of the R-27 and R-77 control surfaces/wings), then we can calculate the coefficient and have realistic drag/turn rates in DCS! :) (of course in hard turn the air would go at 90° angle on 6 wings/control surfaces on R-27 which already is more than the AIM-120's 4 surfaces! So the R-27 CAN make harder turns!!! :D What are DCS values for turns of these missiles?)

Edited July 6, 2016 by DanielNL

[TAW_Blaze]

But isn't "drag" the values of the wings of the missile when they try to make the missile turn into a direction (after engine-cutoff) that how much cm² of control-surfaces will push the air? (To calculate how much force the control surfaces and wings will push with on the missile body to push missile into new direction in the maximum control-surface angle, meaning the control-surfaces missile will push the missile as hard as possible towards a direction) I would expect for example that maximum control surface angle is 45° (higher angle would slow down missile too much?)

 

If drag isn't this what I mean, I'm sorry for the confusion. (Thx for the VERY funny picture above, though, JackBauer xD) And I think Obama would forgive me xD

 

What you're describing here isn't drag but rather the force the fins create to turn the missile in a given direction. Bigger fins might be able to create bigger force to turn but practically it's next to useless because slammer fins are more than enough. Big fins would allow for higher G load at slower speeds however this is totally irrelevant since if your missile is slow it probably won't catch the guy anyway. On the other hand fat fins create massive air resistance that hinders acceleration under all circumstances and will also cause the missile to lose speed faster once the motor burnt out.

[GGTharos]

Ah so it isn't known which shape the nozzles have? (I thought star shape is most effective shape, when looking at missile nozzle from the back?) And which other factors do you mean by "rocket motor optimizations" ?

 

Nozzles are optimized to deliver maximum thrust at a specific altitude. That's a design detail that we'll probably not be able to easily figure out without at minimum the schematics of the nozzle, and with that you have to do a bunch of computation to figure things out.

 

Also rough or exact fuel composition of the AIM-120C (or any) and R-27 ET (or T, in case T and ET have different fuel mixture?) are completely unknown or is sth. published?

 

The fuel parameters that we care about are published for the R-27 family. The only thing that is known about the AIM-120 is the fuel mass and a very approximate burn time.

 

But isn't "drag" the values of the wings of the missile when they try to make the missile turn into a direction (after engine-cutoff) that how much cm² of control-surfaces will push the air? (To calculate how much force the control surfaces and wings will push with on the missile body to push missile into new direction in the maximum control-surface angle, meaning the control-surfaces missile will push the missile as hard as possible towards a direction) I would expect for example that maximum control surface angle is 45° (higher angle would slow down missile too much?)

 

That's just one form of drag.

 

And I just found it, how to calculate the drag coefficient by using dynamic pressure! :D

 

 

We have all numbers we need (if we know the exact sizes of the R-27 and R-77 control surfaces/wings),

 

No, you don't. Just stop :)

 

then we can calculate the coefficient and have realistic drag/turn rates in DCS! :) (of course in hard turn the air would go at 90° angle on 6 wings/control surfaces on R-27 which already is more than the AIM-120's 4 surfaces! So the R-27 CAN make harder turns!!! :D What are DCS values for turns of these missiles?)

 

Are you claiming that they aren't realistic now? Based on what? The R-27 has 4 wings, and please stop with the fantasy. The R-27 has a 24g structural limit, the 120 has a higher one. It doesn't even matter what the fins can do.

 

To put things very simply, many more, far better qualified people have tried to figure this out and what we did get is some computed/CFD'd Cd0's. The whole turning thing though, that's an entirely different story ...

 

... I don't think you can just solve it with one formula :megalol:

 

If you stick with this though you will learn a lot.

Edited July 6, 2016 by GGTharos

[probad]

many more, far better qualified people have tried

 

tbh this should just be the forum banner

[JunMcKill]

I meant the one from 10:22:52, launched from 343,5 m ASL, 110,6 m AGL. But why did you ask? Why calculate TAS if Tacview gives the values? (Or you want to calculate if the values are realistic?)

 

Indeed, and your data is ok, and reflects the figures in the missile_data.lua for the AMRAAM (AIM-120C) which are:

 

accel time: 8.0 seconds

fuel flow rate in second, kg/sec: 6.43

thrust, newtons: 16715.0,

 

So 2,930 km/h in six seconds at 343.5 meters MSL, is not unrealistic and can reach more (two seconds left of thrust!)

 

Altitude (MSL) 343.5

CAS (Calibrated Airspeed): 2911.581670392374

Mach: 2.401042667360204

TAS (True Airspeed): 2930

EAS (Equivalent Airspeed): 2881.8991739205467

[SinusoidDelta]

 

To put things very simply, many more, far better qualified people have tried to figure this out and what we did get is some computed/CFD'd Cd0's. The whole turning thing though, that's an entirely different story ...

 

... I don't think you can just solve it with one formula :megalol:

 

If you stick with this though you will learn a lot.

 

That's interesting. In the reading I've done the most common mathematical model for missile flight is skid-to-turn. STT models assume that the pitch and yaw planes have identical behavior. So when you say 'the whole turning thing' do you mean there were problems determining response/behavior for missile maneuvering in any axis?

[D4n]

So the AMRAAM manufacturer released the information about thrust, fuel flow rate and accel time? Ok, but what about the exact lift force values of AIM-120C and R-27 ET in DCS? Does ET have at least 33% more lift force? (since it has 6 large instead of 120C's 4 small fins)

 

Oh I thought I already posted the video here, but it seems I didn't, here it is (the missile could've hit him if it turned HARDER or at least KEPT turning at 10,7 g...)

 

Be aware loud sound

 

 

So we now have to calculate if the 10,7 g that my ET was pulling is realistic max. value or if a real ET (after engine cutoff) can pull harder:

 

 

FA = lift force, G=weight force (empty rocket mass x 9.81m/s²)

 

 

(we will calculate drag later with other formula)

 

p = density of medium (air, so about 1,19 Kg/m³ in this case, since the ET is at 450 ASL at moment of 10,7g, you can calculate air density on internet websites)

 

v = speed of air hitting the wings (ET speed at moment of showing 10,7 g in tacview is 2.338,2 km/h which is 649,5 m/s)

 

A = total surface of the six ET-missile wings catching air at that moment (at 90° angle I assume?) (cm²) Is there a way to calculate the missile wing surface if we know the exact length of ET missile? (iirc the exact length is known?)

 

CA = lift coefficient (do we even need it in this case where the missile makes a left turn?)

 

 

q = dynamic pressure (p/2 x v² = (1,19 Kg/m³ /2) x (649,5 m/s) ² (ET speed at moment of showing 10,7 g in tacview is 2.338,2 km/h which is 649,5 m/s)

 

= 251000,89875 (pascal I guess? Please help me)

 

 

 

So all that is missing is the cm² of the 6 wings of the ET to calculate and proof that ET can go more than 10,7 g... (or proof that the tacview recording is incorrect and my missile missed because of another reason than "not enough lift force")

[Chrinik]

"So the AMRAAM manufacturer released the information about thrust, fuel flow rate and accel time?"

 

No, he didn´t, and that is the problem.

 

"since it has 6 large instead of 120C's 4 small fins"

 

Where did you get the idea that the R-27 has six fins and the 120 has 4? Both missiles have EIGHT fins, four tailfins, and four Elevons, with the R-27 having some sort of stabelizers on the nose section.

 

You don´t just need fins to pull G, you also need SPEED, and your missile was rapidly bleeding speed since it was apparently launched in very shitty parameters needing to pull 7 Gs sustained to even keep close to tracking the target.

 

In the end, the missile was simply defeated kinematically, the target left the seekers gimbal limits, and it just went stupid.

[DarkFire]

I had a look at the acmi and plotted the flyout. The 120's flight path is good....when it's fired unguided. There is a very slight loft, basically level flight, and altitude drops off sharply below mach=1.5.

 

Fire the 120 (or any missile, same conditions) with guidance and compare the result. It's as if the missile guidance/control is trying to bleed off as much energy as possible.

 

Ah yes indeed, my bad, I'd forgotten completely about that. Out of interest, what did you use to plot the output data? Excel?

[SinusoidDelta]

Ah yes indeed, my bad, I'd forgotten completely about that. Out of interest, what did you use to plot the output data? Excel?

 

Yep, just exported the telemetry csv and graphed it in excel. I can post the xlsx file once I get back to my PC if you'd like.

[DarkFire]

Yep, just exported the telemetry csv and graphed it in excel. I can post the xlsx file once I get back to my PC if you'd like.

 

If you wouldn't mind that'd be very useful, thanks.

[GGTharos]

There was a disagreement over which mathematical model should be used to compute drag coefficient with AoA. Those who could run CFDs to help out didn't seem to have the interest, since it's very involved.

 

What DCS has right now might be just fine though; personally I just don't like the high Cd0; the rest is guidance (there are other things regarding fuzing etc but those aren't about flight).

 

That's interesting. In the reading I've done the most common mathematical model for missile flight is skid-to-turn. STT models assume that the pitch and yaw planes have identical behavior. So when you say 'the whole turning thing' do you mean there were problems determining response/behavior for missile maneuvering in any axis?

[D4n]

What is "Cd0" ? I only find pictures of bikes on google...

 

No, the R-27 has SIX fins that matter in a turn. (the two in front, the two in middle and the two in back that are getting pushed by air on 90° from the side... the other fins in the other 90° turned missile axis don't matter in a straight turn, other than some tiny relation to earths gravity)

[Ktulu2]

I THINK its the Drag coefficient when at null AoA

 

I guess you didn't have enough did you?

 

You need to consider the AoA of each individual control surface, even if it has null AoA it has drag, so 8 fins.

[JunMcKill]

What is "Cd0" ? I only find pictures of bikes on google...

 

No, the R-27 has SIX fins that matter in a turn. (the two in front, the two in middle and the two in back that are getting pushed by air on 90° from the side... the other fins in the other 90° turned missile axis don't matter in a straight turn, other than some tiny relation to earths gravity)

 

drag coefficient of aircraft when lift equals zero

 

https://en.wikipedia.org/wiki/Parasitic_drag