G and AoA limiters

[OlWilly 105]

So, can we have such things in this game?

Yes, we can.

I saw the method in F/A-18A I downloaded. It essentially creates a fake highlift surface which is activated under given conditions and prevents you from exceeding the given limit.

Only in Hornet this fake surface slices down the total lift force - which works, but is not really optimal. Firstly, if you pull really hard and go at high AoA you will already experience the lift force going down - then this limiter kicks in and the situation can quickly turn into accelerated stall. Secondly, I haven't managed to make it work for stock F-16.

The solution is to apply pitch downward force instead of slicing the lift. Much simpler and effective.

This is the type of limiter I put into MiG-23MLD. If you try to go above 25AoA it kicks you back five or so degrees. MLD didn't have fly-by-wire and had simple limiter, so this is even close to historical behavior. Moreso, MLD is not particularly twitchy plane so it works fine.

[AoA_Limiter]
SystemType=HIGHLIFT_DEVICE
Cmdc=-0.5
DeploymentMethod=AUTOMATIC_ANGLE_OF_ATTACK
Setting[1].Angle=45
Setting[1].DeployValue=25.0
Setting[1].RetractValue=24.9
MaxDeflection=45.0
MinDeflection=0.0
ControlRate=10.0
SmoothDeployment=TRUE

But if we try this for more twitchy planes - like F-16 - this creates weird pitch wobbling. Not good, so we have to be more precise. This is the limiter for stock F-16A

[G_Limiter]
SystemType=HIGHLIFT_DEVICE
Cmdc=-0.1
DeploymentMethod=AUTOMATIC_G_LOADING
Setting[1].Angle=45
Setting[1].DeployValue=8.0
Setting[1].RetractValue=7.99
MaxDeflection=45.0
MinDeflection=0.0
ControlRate=0.5
SmoothDeployment=TRUE

[G_Limiter2]
SystemType=HIGHLIFT_DEVICE
Cmdc=-0.05
DeploymentMethod=AUTOMATIC_G_LOADING
Setting[1].Angle=45
Setting[1].DeployValue=8.5
Setting[1].RetractValue=8.49
MaxDeflection=45.0
MinDeflection=0.0
ControlRate=0.5
SmoothDeployment=TRUE

[G_Limiter3]
SystemType=HIGHLIFT_DEVICE
Cmdc=-0.025
DeploymentMethod=AUTOMATIC_G_LOADING
Setting[1].Angle=45
Setting[1].DeployValue=9.0
Setting[1].RetractValue=8.99
MaxDeflection=45.0
MinDeflection=0.0
ControlRate=0.5
SmoothDeployment=TRUE

[G_Limiter4]
SystemType=HIGHLIFT_DEVICE
Cmdc=-0.015
DeploymentMethod=AUTOMATIC_G_LOADING
Setting[1].Angle=45
Setting[1].DeployValue=9.5
Setting[1].RetractValue=9.49
MaxDeflection=45.0
MinDeflection=0.0
ControlRate=0.5
SmoothDeployment=TRUE

[G_Limiter5]
SystemType=HIGHLIFT_DEVICE
Cmdc=-0.5
DeploymentMethod=AUTOMATIC_G_LOADING
Setting[1].Angle=45
Setting[1].DeployValue=12.0
Setting[1].RetractValue=11.99
MaxDeflection=45.0
MinDeflection=0.0
ControlRate=0.5
SmoothDeployment=TRUE

It has 4 (!) main stages which introduce progressive pitch down moment. In effect, no matter how hard you pull, you will keep 9 - 9.5G in continuous turns and wobbling is minimal. The fifth stage is hard cap to prevent going overboard at hard pulls (stock F-16A can easily get instantaneous 20G, crazy). Limiter takes few seconds to kick in but then does it's job.

The template is fit for any plane you wish. The first, simpler method could be used for older no fly-by-wire planes, while multi-stage limiter for the ones that have it. Likewise, you can limit negative AoA and G too.

Obviously, the values had to be tailored for different planes. You need to check the deploy/retract values to specify the range when limiter kicks in. Then, you had to adjust the downforce Cmdc value. If plane gets too wobbly, it had to be decreased; if the limit is exceeded, increased. In general, you want to keep the wobble minimal, at 2-3deg AoA or 0.2-0.3G units. Usually, the more twitchy is the plane, the bigger Cmdc should be.

The values are by no means final. You can stack more stages if you fancy and play around with different values (ControlRate here is the speed at which downforce is applied and removed, I.E - 10 - instantly, 0.1 - very gradually)

This is G limiter for Hornet for example:

[G_Limiter]
SystemType=HIGHLIFT_DEVICE
Cmdc=-0.05
DeploymentMethod=AUTOMATIC_G_LOADING
Setting[1].Angle=45
Setting[1].DeployValue=8.0
Setting[1].RetractValue=7.99
MaxDeflection=45.0
MinDeflection=0.0
ControlRate=0.5
SmoothDeployment=TRUE

[G_Limiter2]
SystemType=HIGHLIFT_DEVICE
Cmdc=-0.025
DeploymentMethod=AUTOMATIC_G_LOADING
Setting[1].Angle=45
Setting[1].DeployValue=8.5
Setting[1].RetractValue=8.49
MaxDeflection=45.0
MinDeflection=0.0
ControlRate=0.5
SmoothDeployment=TRUE

[G_Limiter3]
SystemType=HIGHLIFT_DEVICE
Cmdc=-0.015
DeploymentMethod=AUTOMATIC_G_LOADING
Setting[1].Angle=45
Setting[1].DeployValue=9.0
Setting[1].RetractValue=8.99
MaxDeflection=45.0
MinDeflection=0.0
ControlRate=0.5
SmoothDeployment=TRUE

[G_Limiter4]
SystemType=HIGHLIFT_DEVICE
Cmdc=-0.010
DeploymentMethod=AUTOMATIC_G_LOADING
Setting[1].Angle=45
Setting[1].DeployValue=9.5
Setting[1].RetractValue=9.49
MaxDeflection=45.0
MinDeflection=0.0
ControlRate=0.5
SmoothDeployment=TRUE

This turned out a little bit wobbly, but it keeps Hornet at 7.8-8.2G in continuous turns. Fifth stage is not needed. As you can see, Cmdc values are decreased to reduce wobbling.

You may notice that limiter is kicking in at both cases at 8.0G, but Hornet is kept at 8G continuous while F-16A is at 9G. This is the quirk of the method, you had to tailor it for every plane.

Attached stock F-16A data file with limiter enabled

F-16A_Netz_Data.INI

[+Menrva 4,067]

Thank you very much for these posts on the game's flight models, they are very informative! I'd ask admins to pin this topic and this other one you created: https://combatace.com/forums/topic/98829-trying-to-cure-rudder/

[+Cliff7600 1,147]

On 26/04/2024 at 12:54 PM, Menrva said:

I'd ask admins to pin this topic and this other one you created

I agree these topics are very intersting and worth to be study.

Nonetheless they're not 100% reliable (speed values in data.ini files are in meters per second and not km/h as example) and need to be tested further before being used as a guide.
I experienced bad computer crash while testing the drag rudder fix. --> possibly not related to the "drag rudder fix"

Edited May 1 by Cliff7600

[OlWilly 105]

5 hours ago, Cliff7600 said:

speed values in data.ini files are in meters per second and not km/h as example

I know this, although I don't remember posting anything related to airspeed values. The limiter works with G loading (DeploymentMethod=AUTOMATIC_G_LOADING) and Angle of Attack (DeploymentMethod=AUTOMATIC_ANGLE_OF_ATTACK).

5 hours ago, Cliff7600 said:

I experienced bad computer crash while testing the drag rudder fix.

I don't think it is related. The worst thing you can get is badly controllable plane, although even this is rare. In my install, I fixed the rudder on all aircraft and it works alright.  

For rudder drag, first you had to make check the ReverseInput= parameter. It reverses the values, for example, CDdc=-0.1 with ReverseInput=TRUE value is the same as CDdc=0.1 with ReverseInput=FALSE. It is usually TRUE in most aircraft but I found one where it was absent (it's Su-57 from Banidos)

Then, if you simply want to fix the drag you just make CDdc negative.

If you want to enable sideslip drag, you make the total CDdc of rudder at -0.2. This means CDdc=-0.2 for single rudder aircraft and CDdc=-0.1 in each rudder for twins

This is useful if you need to drop the speed to avoid overshooting (AI likes to force overshoot) and you can sideslip for speed or altitude during landing. If I come in too fast I just go hard sideslip and bleed energy until I can deploy flaps and enter glideslope normally. 

Although of course the testing is needed as FM models differ quite a lot across the board. 

[OlWilly 105]

So I wanted to check if F-22 from download section has G limiter - and of course it has. F-22 FM is credited to Baffmeister by the way

It uses the very same method of applying downforce, has two stages and looks like this (I swear I wasn't copying it when I was experimenting with mine ):

[LS_Pitch_Attenuator]
SystemType=HIGHLIFT_DEVICE
DeploymentMethod=AUTOMATIC_G_LOADING
CLiftdc=0.0
CDdc=0.0
Cmdc=-0.06
AreaRatio=0.0
SmoothDeployment=TRUE
Setting[1].Angle=40.0
Setting[1].DeployValue=9.5
Setting[1].RetractValue=4.0
MaxDeflection=40.0
MinDeflection=0.0
ControlRate=16.0
ModelNodeName=

[HS_Pitch_Attenuator]
SystemType=HIGHLIFT_DEVICE
DeploymentMethod=AUTOMATIC_G_LOADING
CLiftdc=0.0
CDdc=0.0
Cmdc=-0.20
AreaRatio=0.0
SmoothDeployment=TRUE
Setting[1].Angle=40.0
Setting[1].DeployValue=12.5
Setting[1].RetractValue=9.6
MaxDeflection=40.0
MinDeflection=0.0
ControlRate=16.0
ModelNodeName=

Major differences are that retract values are much lower and ControlRate is way higher, also downforce is ascending (in my set-up it is descending).

In F-22 itself it works like a charm, kicks in instantly and no wobbling at all. But I found it more difficult to adapt it to other planes

 

[+Cliff7600 1,147]

On 26/04/2024 at 9:04 PM, OlWilly said:

I don't think it is related

(about the crash of my computer)
You're probably right on this point.