FM behaviour - Rudder cause Blackout and Spin

[Raviar]

I am not sure if this is intended or its a bug, but playing with rudder pedals cause blackout and spin.
In any asymmetric loadout, such as 1 extra Sparrow in 1 wing, for example in left wing, it is even worth, and opposite rudder cause opposite role meaning in left bank, right rudder cause left roll

Tomcat Spin behaviour.trk Tacview-20221223-150813-DCS.zip.acmi

Edited December 23, 2022 by Raviar

[Raviar]

any input ?!

[Golo]

Ehm, not sure its input you want but, dont do that?

Opposite rudder during roll will bring you very quickly into negative Gs, like it did in your case -5.1G, and human body reacts very badly to negative Gs. Not sure if it would cause "GLOC" (you can look it up and let me know) it might be DCSism, not sure.

Nothing out of ordinary to see here I would say.

[Raviar]

I think the real AC won't have that FM! its from nose level to nose down and back flip! May be I am wrong 

[Golo]

I dont see any problem with FM here, what you experiencing is slip-roll coupling because of dihedral effect of F-14 wings, in your case very pronounced negative AOA slip-roll coupling.

Viz. F-14 NATOPS Manual, NAVAIR 01-F14AAP-1, 1 Aug 2001
11.5.2 Dihedral Effect.

Dihedral effect is the tendency of the aircraft to roll in reaction to sideslip being generated. The F-14 exhibits positive dihedral effect throughout the positive AOA envelope (tending to roll away from sideslip), but negative dihedral effect at negative AOA. This tendency is shown by the aircraft response to a rudder input. When right rudder is applied from straight and level flight condition, the aircraft sees sideslip from left and so rolls to the right, or away from the sideslip. Positive dihedral effect is a stabilizing influence in the area of reduced directional stability (high AOA). At negative AOA, dihedral effect is negative such that a right rudder input will produce a left roll. In the PA configuration, negative AOA can be encountered at 1 g flight at the higher limit airspeeds for the configuration.

[Dragon1-1]

9 hours ago, Golo said:

Opposite rudder during roll will bring you very quickly into negative Gs, like it did in your case -5.1G, and human body reacts very badly to negative Gs. Not sure if it would cause "GLOC" (you can look it up and let me know) it might be DCSism, not sure.

IRL, it could well cause death due to a brain hemorrhage. So yeah, a DCSism in that mere loss of consciousness from pushing -5.1G is a relatively benign outcome. The generally accepted limit is 4G IRL, and there's no real anti-G technique that would protect against that (short of somehow restricting the flow of blood to the brain), because in this case, blood flows into your brain, and has trouble flowing back out. This is incredibly unpleasant, too. Real pilots avoid negative Gs like plague, and aircraft aren't really designed to handle them, either. 

[RustBelt]

It’s also really uncomfortable AND ergonomically difficult to input and sustain while being pulled out and away from all the controls even strapped in. 
 

Sims have a way of showing an accurate flight model when the human pilot’s limitations isn’t part of the system.  
 

op, you outside snap rolled an unbalanced plane. Try to keep your speed up and don’t cross control at high AoA. High wingloading can be suddenly unforgiving.  

[Raviar]

On 1/9/2023 at 3:22 PM, Golo said:

I dont see any problem with FM here, what you experiencing is slip-roll coupling because of dihedral effect of F-14 wings, in your case very pronounced negative AOA slip-roll coupling.

Viz. F-14 NATOPS Manual, NAVAIR 01-F14AAP-1, 1 Aug 2001
11.5.2 Dihedral Effect.

Dihedral effect is the tendency of the aircraft to roll in reaction to sideslip being generated. The F-14 exhibits positive dihedral effect throughout the positive AOA envelope (tending to roll away from sideslip), but negative dihedral effect at negative AOA. This tendency is shown by the aircraft response to a rudder input. When right rudder is applied from straight and level flight condition, the aircraft sees sideslip from left and so rolls to the right, or away from the sideslip. Positive dihedral effect is a stabilizing influence in the area of reduced directional stability (high AOA). At negative AOA, dihedral effect is negative such that a right rudder input will produce a left roll. In the PA configuration, negative AOA can be encountered at 1 g flight at the higher limit airspeeds for the configuration.

Thanks for the info,
I am not sure if you see what I am seeing, Can you confirm if you mean such effect ?
https://emalm.com/?v=yqQ-U

Edited January 11, 2023 by Raviar

[Golo]

21 minutes ago, Raviar said:

Thanks for the info,
I am not sure if you see what I am seeing, Can you confirm if you mean such effect ?
https://emalm.com/?v=yqQ-U

At least for the initial part few second in, yes. 

Here is the experiment for you, from straight and level lets say 300kias/10kft, smoothly apply left or right rudder. what you should see is, if left rudder was applied aircraft should start to roll left, than center controls, thats that for positive AOA.

Next set same starting conditions as you start applying your rudder, smoothly push the stick to nose down, that will get you to negative AOA, and for left rudder you will not see left roll, but right one instead, just as the manual said, that is the concept behind the Dihedral Effect.

If you are concerned about what happens further in the video, flipping backwards and such as you asked about FM, whether that is accurate or not I cant say, probably no one can. You are taking it way further than anyone in their right mind would IRL, and maybe further than is physiologically/structurally possible. So there are probably no data on how it should behave in such situation. Treat the modeling as best approximation we have and know that you should not push the aircraft in such situations in the first place.