Adjust Inertia in .par ?

[Jürgen N.]

All sailplanes in FMS I know have one non realistic behavior (in my humble opinion) :
they can loop without problem out of straigt flight. No need to dive a litttle first.
Also the roll rate is much to fast.
This is not a problem of flap throw. It's a problem of inertia.
But how to adjust? I increased and decreased the values considerably without markable effect.
Any hint is very much appreciated.
Kind regards
Jürgen

[ggunners]

Jürgen N.,

Which values did you adjust? These in MAIN for alpha 8.x .par?

0.42 //Roll Inertia Moment Ixx [kg*m^2]
0.37 //Pitch Inertia Moment Iyy [kg*m^2]
0.76 //Yaw Inertia Moment Izz [kg*m^2]
-0.07 //Ixz [kg*m^2]

These control the feeling that the model will continue on a specific vector once movement is started. Lower numbers stop when you release the control while higher numbers keep on turning after the control is released.

If you have too fast a roll rate or too much elevator authority, then either reduce the control throw degrees or reduce the control surface size in the SURFACE (wing) section for each wing.

Also make sure the POLAR being used are from the Diamant (a glider) versus one of the other models or custom make a POLAR that works better for your models wing profile.

-- ggunners

[Jürgen N.]

Yes, obviously I am on the right trail:

MAIN //allgemeine Daten
10.0 //JN(15) Masse des Modells [kg]
11 //JN11Trägheitsmoment um die Querachse (Ixx) [kg*m^2]
10 //JN(8)Trägheitsmoment um die Längsachse (Iyy) [kg*m^2]
10 //JN(8)Trägheitsmoment um die Hochachse (Izz) [kg*m^2]
-0.01 //Deviationsmoment (Ixz) [kg*m^2]

This is the data of a 4 Meter B4 sailplane.
But I see that you are using values below 1.
Could it be that this data is much to high? If so, that's the problem. Reducing control throw is not the solution.
It's needed for aerobatics and landing.
And, please:
what is the meaning of "deviation"?
Many thanks and regards
Jürgen

[ggunners]

I'm not a math, physics or aeronautics wizard so...

Deviation Moment =
products of inertia of a distribution of matter in relation to a plane.



All I know is that this number is usually a very small negative number.

I have a modified file on my web site. It's setup as a motorized glider at this time. Just drop the motors out for gliding only. It may be a better starting point than the .par you're using.

-- ggunners

[Jürgen N.]

Interesting.
But I need also the rest of the plane. I can not find it in your collection.
Kind regards
Jürgen

[ggunners]

Just figured you got it from here.



I just moved the CG forward a bit too because the model was porpoising.

-- ggunners