The R-77 'ADDER' - History, Design, Performance & Discussion

[Aetreus]

I mean they are obviously wrong. Kmax is the maximum value of Cl/Cd across al AoA. Clmax is the maximum lift coefficent, normally right before a stall. CdMin is the minimum drag coeffient, normally 0 AoA. These are no the same AoA(duh) so Kmax = ClMax/CdMin is completely wrong.

Here, look at this graph. You can see CdMin and ClMax and they’re nowhere near each other. Cl/Cd isn’t graphed here, but it’s in the middle somewhere.

This is a drag polar graph, where you can see that KMax(point b) ClMax(point d) and CdMin(point a) are all different.

[Aetreus]

That is what you wrote so you just communicated poorly. And your graph still doesn’t say what you want it to.

[BBCRF]

I was referring to the maximum lift coefficient with minimal drag. Not the absolute maximum of Clift

[Aetreus]

That’s not what LMax or ClMax is. So don’t call it that. It’s wrong.

[BBCRF]

[Aetreus]

Yes, you will note on this chart it lists L/Dmax alongside ClOpt. ClOpt is the lift coeffient at L/Dmax, and is different than ClMax. You can also try dividing ClMax by Cd0(which is generally CdMin) and observe that you get a different result than L/DMax.

[BBCRF]

Kmax This means with Clmax(not Cl=f(aoa)) at a minimum Cd

[Aetreus]

Yes it’s increasingly clear you have no idea what you are talking about.

[BBCRF]

[MiG_23M]

I think he’s demonstrated quite well he understands what he is saying. He’s one of the developers behind the DCS mod that has produced a high fidelity and realistic FM for the Su-27. Between the two of you I feel he’s explained himself quite well.

@BBCRF not sure the gifs are a smart idea, may result in adverse action and give people who don’t understand the impression that you aren’t on the ‘winning’ side. Not that this is about ‘winning’.

@Aetreus if you think the R-77 model is erroneous in-game please explain how and with supporting documents / performance charts.

[BBCRF]

Clopt This explanation will suit you

[Aetreus]

Try communicating in a way that makes sense with regards to the subject matter. This:

@BBCRF

Kmax This means with Clmax(not Cl=f(aoa)) at a minimum Cd

Makes no sense. “With ClMax?” but Kmax is not at ClMax. “not Cl=f(aoa)”, but Kmax is literally the max of that function. “at a minimum Cd” but Kmax is not at minimum Cd either.

@BBCRF

Clopt This explanation will suit you

Yes? That’s what I think you’re trying to say, but you have done a terrifically bad job of it. Saying “it is the maximum value of the lift to drag ratio at any AoA” would have just explained things.

@MiG_23M

I think he’s demonstrated quite well he understands what he is saying. He’s one of the developers behind the DCS mod that has produced a high fidelity and realistic FM for the Su-27. Between the two of you I feel he’s explained himself quite well.

Appeal to authority. Also like literally just asserting your conclusion. If he’s good at this then he needs to actually demonstrate it and this is not it.

[MiG_23M]

@Aetreus

If he’s good at this then he needs to actually demonstrate it and this is not it.

He’s not an authority, he’s demonstrated his knowledge already in the past. Not taking the time to answer you in some drawn out manner doesn’t mean he’s wrong.

[BBCRF]

@Aetreus

Makes no sense. “With ClMax?” but Kmax is not at ClMax. “not Cl=f(aoa)”, but Kmax is literally the max of that function. “at a minimum Cd” but Kmax is not at minimum Cd either.

WELL, this is literally a function of Cl=f(Cd). So with the Kmax. Your L will be the maximum for the current Cdmin value Or Clopt/Cdmin

[BBCRF]

@Aetreus If you want an L/D graph for the grid fins and monoplane wing. Unfortunately, there is no such schedule. Only Kmax

[Aetreus]

@MiG_23M

He’s not an authority, he’s demonstrated his knowledge already in the past. Not taking the time to answer you in some drawn out manner doesn’t mean he’s wrong.

There’s a difference between “brief” and “wrong.” BBCRF’s responses were wrong. Just like, flagrantly wrong.

@BBCRF

@Aetreus If you want an L/D graph for the grid fins and monoplane wing. Unfortunately, there is no such schedule. Only Kmax

Well that sucks for you because as I have noted, Kmax is not enough to describe an air to air missile’s drag behavior. Because unlike an aircraft(or cruise missile), the missile will constantly vary in speed and therefore lift required to maintain level flight, and therefore its actual K in flight will not be Kmax. And of course lofting will throw a whole extra grenade into this because it means lift required isn’t just gravity, and at any rate the fins aren’t generating most of the lift to keep the missile in the air, only to control its AoA.

[Charteuse-55_ABV]

@MiG_23M

Again, the grid fin doesn’t require equal AoA to planar for similar torquing moments on the missile.

Well yeah, you can see it on the charts. Lower Cl for all angles of attack. Meaning you’d need to pull more AoA for the same lifting force. But guess what? Through L/D(Cl), despite pulling more AoA Doing so wouldn’t mean a high loss in velocity. And up to what angle? <~20°. And from your own words, they don’t pull that much.

The force required to rotate them to those angles, I don’t give damn. Pretty sure they can do it.

@MiG_23M

You’re implying the planar fin has anywhere near the same torquing moment on the missile as the grid fin without having nearly equal drag is… interesting

Holy moly.
Do you even know what the direction of THAT hinge moment measure is? Do you know what the direction of the moment of the drag force is? Please tell us. Tell us

Do you need a drawing?

@MiG_23M

… What?
How is it baseless, it’s data already discussed and provided in sources in this same thread

No you haven’t. You just quote M1.3 without any variables which depend on lots of stuff which YOU DON’T KNOW. How do I know? Because you didn’t answer this!

@Charteuse-55_ABV

you are just ignoring it because it doesn’t align what you assume to believe what is correct despite conceptual proof and data proof. Go ahead, tell me the dimensions then. To the detail. Gap, chord, length, height of the main fin

@MiG_23M

It’s not relevant, I’ve pointed out how the response given is purposefully misleading. You realize that I’m not the one you must convince to a-historically nerf the missile right?

Not relevant? Lmao. Do you know what happens when there’s a higher pressure in-infront of the grid fins?

Nor you answer this

@Charteuse-55_ABV

Just a simple critical thinking will show you otherwise, what has more frontal surface area perpenducular to the airflow? 1 planar or 8 planar fins with the same size?

You are so damn high on an erroneous idea you are failing to ask yourself basic questions and if you do, you just try a way to justifying them with mental gymnastics.

[BBCRF]

@Aetreus

Well that sucks for you because as I have noted, Kmax is not enough to describe an air to air missile’s drag behavior. Because unlike an aircraft(or cruise missile), the missile will constantly vary in speed and therefore lift required to maintain level flight, and therefore its actual K in flight will not be Kmax. And of course lofting will throw a whole extra grenade into this because it means lift required isn’t just gravity, and at any rate the fins aren’t generating most of the lift to keep the missile in the air, only to control its AoA.

I understand what you want to see.But the Kmax reflects the aerodynamic perfection of the aircraft. In Belotserkovsky’s Book there are graphs for an abstract lattice with different steps and for numbers M

[MythicPi]

I think one of the funniest parts of this whole “planar fins vs lattice fins” argument is the fact that despite graphs demonstrating the high drag issues of the lattice fins, and the (generally) better L/D ratio of planar fins, and the NATO paper specifically stating their high wave drag discredits their use for air to air missiles, the pro-russian players cannot or will not grasp the concept of these fins having pretty clear drag issues

The lattice fins do offer more lift at lower AOA’s, they also offer vastly more drag at all AOA’s according to the graphs.

Lets go for an example:
For a CL of 0.4, the planar fins deflect to roughly 12.5deg vs the lattice’s 8-9deg

At said AOA’s, the lattice fins Cd is roughly 150% that of the planar ones:

Which is how the planar fins exhibit better L/D ratio for given CL’s up to around 0.6, such as at 0.4 as seen in the graph:

The fact that the lattice fins can deflect less for a given amount of lift is a definite advantage for them, but does not change the fact that for fin deflections of up to (roughly) 12.5 deg for the lattice fins, and 20 deg for the planar fins, the planar fins are simply more effective designs.

ie: the R-77 should retain its energy better relative to lift at high fin deflection (12.5 deg and above) than the planar fin deflected above 20 deg AOA, but in all fin deflections below those points, the planar fins are more aerodynamically efficient.

Beyond this point, theres still the fact that the devs have not modelled the lattice fins drag to be unique in any way as it should be, which means that, as stated a while back, lattice fins are getting all their advantages in-game with none of their disdvantages.

This is further supported by the fact that though the R-77 and AIM-7M have almost identical sizes, with he 7M being slightly longer, the R-77 has been given a substantially lower CxK of 1.85 vs the 7M’s 2.3:

So, congrats to the pro-russian players, you’ve once again managed to weasel your way into an ahistorical buff. Its basically an artform how good you guys are at getting free handouts at this point

[BBCRF]