Worse IRCCM should be worth to look into…
basically the issue is we lack launch parameters of manpads for Stingers and Mistral.
Calculations of lift forces on a rotating missile is inherently complex.
Current model in game is as always, an estimation of missile capabilities, which may or may not be close to real life missile.(in fact we have a lot of missile reports open)
Reports with substantive data and information are always welcomed.
If we have a model bridging the gap between 20g in the documents and current 12G implementation it would be most ideal.
Its Gaijin’s modus operadi these days, its blatantly obvious that they despise non-PACT equipment.
It took sustained backlash to get the strela put to a BR where it is not comically overpowered and did not invalidate all western MANPADS, but gaijin is now banking on people forgetting that the strela was only half the issue present.
One day gaijin may actually model western MANPADS to their historical standards, but I’d wager I’ll be dead by then. There are already massive amounts of irrefutable proof in this thread and elsewhere that the current implementation is flawed, yet, its not enough.
Edit, lol, someone really likes going through my exceptionally old posts and community hiding them.
The Strela literally went up the first BR patch after it was buffed. Furthermore no one has proven or added anything new. Only done so far is their own interpretation of the available information.
I added a write up of where a few points of clarification could be useful using a number of articles that are relevant to a separate topic but it got removed ( removed December 10th ) by an overcautious mod, and I’m still waiting for it to be restored.
Here’s a link to at least one of them anyway.
The relevance of said article is that;
Viewing collectively the results obtained, it is concluded that the
effect of directing steering control out of the angle-of-attack plane can be approximated, for the conditions tested, by directing the control-force increments and control-moment increments obtained when 0 = 0’ to the new steering
direction, then resolving these increments back to the nonrolling axes system
used herein. The accuracy of this procedure (exact at zero angle of attack) deteriorate somewhat as angle of attack increases.
~~
CONCLUSIONS
The normal force and pitching moment data provide smooth definitions
of the configuration’s longitudinal stability and control characteristics.
These forces and moments are not sensitive to the values of spin parameters
tested.
Small side forces and associated yawing moments, induced out of the plane
of maneuver, show dependence on Mach number, angle of attack, steering-control
amplitude and direction, and spin parameter.
Is reductive in the extreme and doesn’t take a number of relevant factors into account. There are others sources (I’ll see if I can find them again) that also reference the impact of the interaction of the tail with vortices generating additional loading.
Giving the Igla the advertised “average” g load, but assuming the advertised g load for western manpads is “peak instantaneous” is a double standard. Plain. And. Simple.
There is zero basis for the peak instantaneous g assumption. You, and GJN, can’t find any evidence of that usage anywhere, and this thread contains plenty of examples demonstrating why it should be average g load.
They wanted to move it to only 9.7 and had to move it to 10.0 after massive backlash. It’s still undertiered.
Sticking your head in the sand and pretending evidence doesn’t exist, like GJN is doing, doesn’t mean the evidence is wrong.
It literally says approved for public release. Are you having trouble reading English? Translation software not working?
It was probably removed for making GJN look bad, because it completely contradicts the fairytale they posted as a dev blog.
Among other things, the fins pull a lot more AoA. Design wise they’re actually closer to “proper” AAMs (like the Sidewinders for example) than MANPADS, which the Stinger and Igla are.
The biggest difference is that TY-90 uses standard skid to turn control (Sidewinder and AIM-7) while SA-14 and FIM-92 use rolling airframe turn control (I’m not good at explaining how it works, I think Wikipedia has a better idea).
Gaijin claims rolling airframe missiles cannot perform at the same level as skid to turn missiles, but we have confirmed evidence that this is untrue.
Even if there was, the ingame stat is “Max” g-load. The fact theyre using what they believe to be the “average” g-load as the max is immediately silly, particularly when weve seen them set fin aoa’s to adjust at what kinds of speeds the missile can actually reach those peak G loads…
It’s difficult to confirm the effective control surface area between the two missiles, but there are vastly higher performance weapons of similar size and mass with rolling airframe control type. Mistral, for one, is in the same weight class but turns much harder.
The Improved Rolling Airframe Control Schema (directly references , and claims improvement over the above methods, as well as sharing characteristics of the FIM-92 airframe, not the RIM-116)
A Rolling airframe (with Dithering control surfaces) Autopilot implementation
(There is a 4th patent that deals with maintaining the Roll rate using the fixed surfaces, but until I get there its not yet directly relevant past a point, as a difference from counterparts)
The Three technical papers (for further reading at this point)
I’ll address the issue(s) with the MANPADS article, of which a number or inaccuracies have been discovered. Of which I’ll run through things in a revised order to make more sense, and highlight the differences between the system’s (Redeye, Igla, Stinger) features as there are subtle, but critical to their performance and differences that the not mentioned.
Scope & Claims of the Article
In this, Figure 9.(specifically the Shaded area of “Fz”)and excerpts of US3010677. and the below Passage from the article are in good agreement. Though note with Figure 12., the fact that the Redeye (like the earlier Strela-2) lack a second set of pop-out surfaces, as found on the Igla (The Stinger has a similar system, but it’s a little more advanced)which influence the aerodynamic Center of Lift of the missile forward, closer to the center of mass, and so reduces the effective moment arm and resultant longitudinal inertia of the system making it more maneuverable than said system.
US3010677 exerpts
Consequently, the wings are extended for a portion of. each roll cycle; the center of the extension periods coincides with the desired direction of lift, and the width of the period is a function of the error signal magnitude. This wing extended time is called the lift sector. The desired-direction lift and quadrature lift which result are also shown in FIGURE 9.
( Note; Quadrature is used due to the rolling frame of reference, a synonym would be Orthogonal, Yaw or Axial in other reference frames)
Actually, the lift force generated by the wings is only a fraction of the required lift force. The remainder of the force is provided by the fuselage; Since body angle of attack lags behind wing force in time, the reference coil must be rotated through a lag angle with respect to the wings. This lag angle is such that the net lift force (wing plus body) is in the direction of the target.
The way the resulting force in the missile maneuver plane changes can be represented in a simplified form as a half-wave of a sine wave. The average resulting force in the maneuver plane over a half-period of rotation is equal to the integral of the change of the resultant force in the maneuver plane. Dividing it by the integral of the resulting force in the plane of the maneuver of a non-rolling airframe missile over the same time period, we obtain the ratio of maximum overload to the average overload over the rotation period.
Therefore, the average resulting force over half a rotation period for a missile with a single-channel control system in relay mode will be 63.66% compared to the same non-rotating missile performing a maneuver in the plane of the control surfaces. The ratio is also the same for the average available overload to the peak one when the rudders are in the maneuver plane.
If that’s how the Igla works, in a similar manner to the FIM-43 that’s fine model it as such, no issues there.
This is where the Article effectively entirely drops the ball and runs entirely on assumptions and conflates systems and features since they’re not outwardly obvious.
The points of order are that;
The stinger uses Variable Incidence (proportional) control surfaces, not of the Bang Bang type the Igla uses
The Stinger uses a Closed loop guidance method, which is capable of damping control responses and so fundamentally can account for reduced stability of a design.
Take any one of the excerpts below, its fairly obvious that the Stinger could not function if it was similarly equipt to the Igla with Bang-Bang control surfaces
US4037806 exerpts
prior to the invention set forth in the hereinafter cited co-opening application, control of a rolling missile was effected by utilizing fixed incidence, variable area canards or wings which were extended into the missile air stream at a certain point in the revolution of the missile, as described and claimed in U.S. Pat. # 3010677
~~
However, this invention provides an air vehicle such as a missile with a pair of fixed wings or canards and a pair of variable incidence control surfaces or canards which are continuously dithered or vibrated so as to provide instantaneous movement due to the elimination of the initial inertial force.
~~
In the servosystem of the present invention, missile wing incidence is controlled by a non-linear control servo loop and comprises a position servo having non linear switching elements in the forward loop. The wing position output follows control-servo command input voltages, which vary sinusoidally at the missile roll frequency for steady tracking rates. The servo error signal, which is the difference between the control servo command and the wing position feedback signals, is superimposed on a dither oscillator signal, causing the servo switching circuit to pulse modulate power to a torque motor. The torque motor integrates this incoming pulse-modulated signal so that the resultant wing deflection rate follows the servo error signal. Therefore, an object of this invention is to provide a control system for air vehicles. A further object of the invention is to provide a missile servocontrol system which utilizes variable incidence control surfaces.
~~
The seeker proportional navigation signals, processed by the missile control section, command control surface movements so that the missile trajectory becomes a collision course with the target. When a maneuver is called for, the angle of the variable-incidence control surfaces is changed as required for flight path correction.
~~
Connected with said dithering means whereby the incidence angle of the variable incidence control surfaces is selectively varied during that portion of the missile’s roll necessary to keep the missile on a target intercept course while continuously dithering said control surfaces course.
With a single-channel relay control of a rolling airframe missile, to create a control force in any direction of flight, the rudders are moved by the servomotor mechanism from one outermost position to another four times per revolution of the missile’s rotation. This rudder control scheme makes it possible to regulate the resulting overload and therefore ensure proportional guidance of the missile.
For other MANPADS systems, open sources indicate a higher overload such as 18, 20 and even 25g in the case of the Mistral 1 MANPADS. However, these MANPADS systems have only slight differences in the area of aerodynamic surfaces compared to the 9M39, so a multiple increase in average achievable overload compared to the 9M39 cannot be expected.
Let alone US4054254 which describes the requirement of an open loop control schema (no feedback loop in the guidance section), to use a more aerodynamic design with greater stability (Center of lift behind of center of mass), than that of a similar closed loop design. This is important due to the fact that a Stable design must first overcome the restoring forces inherently generated to achieve a given angle of attack, And that an Open loop configuration is inherently conservative due to not being able to account for other factors and so the design needs to take edge cases into account, where the performance can be optimized by using a Closed loop design.
It is observable that the FIM-92 uses a Closed loop schema, as the Feedback Network is a clearly listed element in Figure. 4, (Block diagram) of US4037806 ,as seen above)) though the example missile in US4054254 is that of a RIM-116 (same Contractor involved with both in the same timeframe).
Also noteworthy is that Figures. 6c & -d(see below for excerpts), do not agree with the modeling (“Fz” & “Fx”) and so should not be impacted by the averaging of performance limits , as asserted in the MANPADS article.
US4054254 excerpts
The systems utilized are designated open-loop in that they utilize a control demand that is not modified by feed-back
So now that It has been asserted to be erroneous, what do we do?
Simply reinstate the limits as per primary sources at about 18~22G as they were, when originally implemented; in 1.91.
