Roll stop

[AerobaticsFS]

Hi everybody,

I've searched for anwsers, but I couldn't find anything. So I ask it here:

Is it possible to get a quick roll stop in FSX?

For most aircraft, this is maybe not relevant, but for me, as an aerobatics aircraft designer, this is quite important for a realistic flight experience. However, as I said, I have nothing found to get this done.
I tried different aircraft, but without result

I have asked a real pilot, who flies the Extra 300S, and he said that he moves the stick from full aileron to a little through neutral to the other side (for a really sharp stop) when he has about 15 degrees left before being level. In FSX however, you fly mostly about a half roll or even more before you stop.

Any ideas?

Thanks in advance!

Daniël

 

[Roy Holmes]

Daniel,
I'm assuming you are looking for the ability to do crisp 4 point or 8 point slow rolls. Or put another way, you want to be able to instantly stop roll at, for example, the 90 bank point or 45 depending on whether it is a 4 or 8 point roll.
This is a function of roll inertia and the coefficient for that is in the aircraft.cfg. as empty_weight_roll_MOI in the [weight and balance] section. The stock Extra has a value of 395 for this. Increasing that value will cause the roll to overshoot the desired angle and you will need opposite aileron to stop it rolling. Decreasing it is what you want to do and you might try 300 as a starting point.
Roy

 

[fsxar177]

Good-Luck. It's possible, but not easy. Look into the Iris Christian Eagle for comparison. If I remember they had it close. Forget Alabeo (Bernt Stolle) stuff.

Have fun!
- Joseph

 

[AerobaticsFS]

Thanks for replying @Roy Holmes ! Basically, I want every roll to be possible (so 2 full rolls etc), but the 4 and 8 point rolls are also part of this. It is what makes aerobatics so challenging
However, decreasing the empty_weight_roll_MOI makes the airplane also roll slower, which isn't what I wanted.The Su26 rolls about 400 degrees/second, so I want that to get it as close as possible.
I guess this will be trying a lot with the empty_weight_roll_MOI, Cl_da Roll Moment - Ailerons (Control) and the Cl_p Roll Moment - Roll Rate (Damping), because they are most influencing the roll afaik.

Good advice @fsxar177 , I'll take a look at what is possible there.

Many thanks!
Daniël

 

[Roy Holmes]

The aileron power does come from CL_da which is roll control per radian of aileron deflection, so you can also increase it by increasing the aileron deflection in the .cfg.
I'm surprised that the roll rate reduced with a reduced inertia, makes little sense that it should. Also remember that roll rate increases with airspeed in the sim.
I recently did the FDE for a Mirage F-1 for SimSkunkWorks and a F-1 pilot commented on the roll inertia being too high, so I halved it and he was happy with the result.
Roy

 

[AerobaticsFS]

Maybe it is only when you get very low values. I have 150 as moment of inertia now, which makes it stop way quicker, but now I have to make the aircraft roll faster. I'll let you know!

 

[bstolle]

@AerobaticsFS
Suggest to forget fsxar177s comment about the IRIS Eagle (and my FDE work) as the basic FSX problem you are having simply doesn't apply to the Eagle FDE for various reasons. Sent you a PM

 

[SierraB]

I had exactly the same problem, when I was into the Red Bull Air Race thing. Actually I configured a Zivko Edge to my liking and ended up with an XML script that controlled the roll rate in these situations.
XMLTools being the keyword. As always.

 

[AerobaticsFS]

I had exactly the same problem, when I was into the Red Bull Air Race thing. Actually I configured a Zivko Edge to my liking and ended up with an XML script that controlled the roll rate in these situations.
XMLTools being the keyword. As always.

If you can help me with some kind of tutorial and a link to the right program, I can give it a try

Actually, I never heard of using XML script to control the flight characteristics.
Thanks anyway for the idea!

 

[SierraB]

First download and install Tom Aguilo's superb XMLTools. It has a ton of functionalities - for example writing to A:Vars. Ensure your Simconnect is working.

Attached is a quick and dirty script I did for the Edge back then. Basically it just adds the wanted "snap".(*) Nothing fancy and it can surely be improved.

XML offers more than you might think. You can even code a complete helicopter flight model in XML and override the crappy FSX one ;-)

(*) install like any other gauge; put it in a folder in the panel directory and add a line to the panel.cfg

 

[AerobaticsFS]

Thanks @SierraB !

Although, I took a look at your file, and I didn't understand what it exactly said... So I guess it will take a lot of time before I can handle this, but it is worth a try
I'll let you know if I get something interesting!

 

[SierraB]

...and I didn't understand what it exactly said...

Apologies for not posting a more readable version of the code. For what it's worth, here are some hints to get you started:

<Macro Name="b">(A:ROTATION VELOCITY BODY Z,degree per second)</Macro>

-> stores the roll rate variable in "b" -> saves you the typing later on

(P:ABSOLUTE TIME,seconds) (G:Var1,number) == ! (>G:Var2)
    (P:ABSOLUTE TIME,seconds) (>G:Var1,number)

-> determines the sim is not paused

(A:AILERON POSITION,percent) @b / 0 > @b abs 20 > and sp0

-> as soon as the stick input is in the opposite direction to the current roll rate ("...to a little through neutral to the other side...") AND the roll rate is above 20 deg/sec the stack register #0 is set to 1

l0 ! if{ @b 0.5 * (>G:Var3) }

-> whenever the #0 register is not 1 the current roll rate multiplied by a factor is stored in G:Var3 (this will determine how fast the roll stops)

(A:AIRSPEED INDICATED,knots) 60 > l0 and (G:Var2) and
    if{       
         (G:Var3) (>@a:ROTATION VELOCITY BODY Z,degree per second)
         (G:Var3) 0.5 * (>G:Var3)       
    }

-> whenever the IAS is above 60 knots, the sim is running and the roll stop is initiated, G:Var3 will become the new actual roll rate. And it gets further decreased by 50% every gauge cycle (18 times per second)

As I said quick and dirty, but it does the job. Play around with the factors.

Hope this helps.

 

[AerobaticsFS]

Thanks @SierraB ! This makes it much more readable for me

However, yours is for the snap roll, but if I want to do it for the aileron roll, should I use BODY Y instead of BODY Z?

 

[SierraB]

However, yours is for the snap roll, but if I want to do it for the aileron roll, should I use BODY Y instead of BODY Z?

ROTATION VELOCITY BODY Z should be the roll rate IIRC.
But I see where your concern comes from; I mistakenly named the file "roll snap", although it has nothing to do with a snap roll ;-)

It IS for a quick roll stop with aileron control. A better snap roll behaviour is another story...

 

[AerobaticsFS]

ROTATION VELOCITY BODY Z should be the roll rate IIRC.
But I see where your concern comes from; I mistakenly named the file "roll snap", although it has nothing to do with a snap roll ;-)

It IS for a quick roll stop with aileron control. A better snap roll behaviour is another story...

Aha! I understand
Thanks for the start, I'll play with the variables and let you know what my results are!

 

[AerobaticsFS]

Hi @SierraB
How do I know that my Simconnect is working? I have installed FSX Golden Edition and the SDK fully working.
I tried some extreme values, but I couldn't notice a difference

Cheers,
Daniël