figuring out alpha 8 .par file - I'd like to adjust my models

[ggunners]

Anybody figured out how the position information is generated for the surfaces?

Does it relate directly to the .mqo or the .x file?

-- ggunners

[ggunners]

<SNIP>

See Roman's more accurate translation below.

-- ggunners

[ggunners]

See the .par comparision at: .

-- ggunners

[ggunners]

Some additional questions.

When plotting position numbers for surfaces, they seem relative to the center of gravity (CG) and I think they reference the center point for the surface of the wings. At least it looks good on paper. Looks like coordinates are Z,X,Y with Z+ forward, Z- aft, X- left, X+ right, Y- up and Y+ down.

The engine location number though seems too high for the models. The Pitts shows the engine at .4989 meters in the Z axis but has the fuselage at .14583 in the Z axis with a length of 1.1 meters or .55 meters in the positive Z axis. If .14583 is the center point, the fuse would be in front of the prop and would not touch the tail. If .14583 is the beginning point in the Z axis for the fuse, it sticks out past the tail and doesn't touch the engine.

Is the fuse position related to the engine?

Are wing and elevator positions center points?

What about the rudder, is it center position or starting position?

I'd like to make my own .par file. Just having trouble relating the numbers to the actual model.

-- ggunners

[ggunners]

While figuring out how surfaces work, it looks like ex refers to wing sweep while ey refers to dihedral.

An ex of 1 0 0 means no sweep.
An ey of 0 1 0 means no dihedral.

Pitts top wing has sweep Surface 1 & 2.
Pitts bottom wing has no sweep and dihedral 6 & 7.

Do the numbers represent percentages?

If so relative to what? The surface center?

-- ggunners

[Roman Moeller]

Hello ggunners,

the coordinate system is as follows: X+ forward, X- backward, Y+ right, Y- left, Z+ down, Z- up. Coordinate systems are allways right-handed. All position refer to origin 0,0,0. The center of gravity, can be positioned to another point, but is usually 0,0,0. For the wing-elements, the coordinate refer to the centre of the wing-element in wing span direction and to the "0.25*chord-length point". The orientation vectors of the wing-element are ex: in flight direction, ey in wingspan-direction.

And here the translation of the words I know in english:

VERSION 1.0

INFO
Kunstflug-Doppeldecker Pitts
Spannweite: 1.7 m
Gewicht: 5.5 kg
Motor: 15cm^3

RC-Funktionen:
Kanal 1: Seitenruder & Heckrad
Kanal 2: Höhenruder
Kanal 3: Querruder
Kanal 4: Motordrossel

Copyright 2003 Roman Möller

3D-Modell von Yosito Sekiai
ENDINFO //All text between INFO and ENDINFO is only information for the reader. It has no effect on the simulation.

AIRPLANE //Flächenmodell modeltype is an airplane and no helicopter

MAIN //allgemeine Daten general data

5.5 //Masse des Modells [kg] model mass
0.42 //Trägheitsmoment um die Querachse (Ixx) [kg*m^2] moment of inertia around the x-axis.
0.37 //Trägheitsmoment um die Längsachse (Iyy) [kg*m^2] moment of inertia around the y-axis
0.76 //Trägheitsmoment um die Hochachse (Izz) [kg*m^2] moment of inertia around the z-axis
-0.07 //Deviationsmoment (Ixz) [kg*m^2] product of inertia
0 0 0 //Position des Schwerpunktes [m] postion of the center of gravity
0.38 //Flugzeughöhe (0-Punkt über Boden - für Initialisieren) [m] airplane height over ground (is used to initialise the position of the airplane)

MOTOR //Motor(en) engine(s)

0.4989 0 -0.008 //Position [m] position
1 0 0 //Zugrichtung direction of thrust
0.35 //Propellerdurchmesser [m] diameter of the propeller
0.18 //Pitch, Steigung des Propellers [m] pitch of the propeller
2 //Anzahl Propellerblätter number of propeller blades
0.025 //mittlere Propellerblatttiefe [m] mean chord length of the propeller blades
RIGHT //rechtsdrehender Propeller clockwise rotating propeller
0.0006 //Rotationsträgheitsmoment von Propeller und Motor [kg*m^2] moment of inertia of the propeller and the engine
4 //Kanal channel
COMBUSTION //Motortyp = Verbrennungsmotor motor type = combustion engine
15 //Hubraum [cm^3] cylinder capacity
0.61 //Spritverbrauch bei Volllast [g/s] fuel consumption at full throttle
1.5E5 //Motorenwiderstandskonstante [Pa] friction constant of the engine
0.6 //Motorenwiderstandskonstante [Pa*s^2] friction constant of the engine
450 //Tankgrösse (0=Tank nie leer) [ml] tank size, 0 = never empty

WING //Flächen wings

//Fläche Nr. 1
0.0876 -0.4276 -0.1714 //Position [m] position
0.99452 -0.10453 0 //ex unit vector in flight direction
0.10453 0.99452 0 //ey unit vector in direction of the wing span
1 //Polare (Nr.) number of the used polar (polars are defined below)
0.85 //Flächenbreite (Spannweite) [m] wing span
4 //Anzahl Elemente number of elements
AUTOELEMENT //Alle Elemente sind gleich gross all elements have equal size
1 //Anstellwinkel [°] angle of attack
0.28 //Flächentiefe Anfang [m] chord length at the first end
0.28 //Flächentiefe Ende [m] chord length at the second end
0.07 //Klappentiefe [m] flap chord length
0.09 //Klappenanfang [m] start position of the flap
0.43 //Klappenende [m] end position of the flap
-20 //maximaler Ausschlag [°] maximal deflection of the flap
3 //Kanal channel of the flap



DRAG

0.086328 0 0.074435 //Position [m] position
0.015 //Referenzfläche [m^2] reference cross section
1.2 //cw cw
0 //Kanal (0=kein) channel

POLAR

//Polare Nr. 1
18 //Anzahl Werte number of values
-180 0 0.03 0 //Anstellwinkel [Grad], ca , cw, cm angle of attack [degree], lift coefficient, drag coefficient, moment coefficient
-170 0.63 0.1 0 //Anstellwinkel [Grad], ca , cw, cm
-90 0 1.2 0.3 //Anstellwinkel [Grad], ca , cw, cm
-50 -0.45 0.96 0.21 //Anstellwinkel [Grad], ca , cw, cm
-20 -0.7 0.46 0.12 //Anstellwinkel [Grad], ca , cw, cm
-12 -0.67 0.19 0.1 //Anstellwinkel [Grad], ca , cw, cm
-10 -0.82 0.08 0 //Anstellwinkel [Grad], ca , cw, cm
-8.2 -0.79 0.045 0 //Anstellwinkel [Grad], ca , cw, cm
-2.5 -0.34 0.025 0 //Anstellwinkel [Grad], ca , cw, cm
2.5 0.34 0.025 0 //Anstellwinkel [Grad], ca , cw, cm
8.2 0.79 0.045 0 //Anstellwinkel [Grad], ca , cw, cm
10 0.82 0.08 0 //Anstellwinkel [Grad], ca , cw, cm
12 0.67 0.19 -0.1 //Anstellwinkel [Grad], ca , cw, cm
20 0.7 0.46 -0.12 //Anstellwinkel [Grad], ca , cw, cm
50 0.45 0.96 -0.21 //Anstellwinkel [Grad], ca , cw, cm
90 0 1.2 -0.3 //Anstellwinkel [Grad], ca , cw, cm
170 -0.63 0.1 0 //Anstellwinkel [Grad], ca , cw, cm
180 0 0.03 0 //Anstellwinkel [Grad], ca , cw, cm
-10 //Anstellwinkel [Grad] bei unterem Strömungsabriss angle of attack at the lower flow separation
10 //Anstellwinkel [Grad] bei oberem Strömungsabriss angle of attack at upper flow separation
1 //Abrisshysterese [Grad] flow separation hysteresis


POINT //Gleitpunkte collision points

0.021 0.872 -0.168 //Position [m] position
1200 //Federkonstante [N/m] spring constant
35 //Dämpfung [N*s/m] damping
180 //Bruchkraft [N] breaking load
1.2 //Reibungskoeffizient [-] coefficent of friction


WHEEL //Fahrwerkspunkte (Räder) points of chassis - wheels

0.17 -0.23 0.375 //Position [m] position
1300 //Federkonstante [N/m] spring constant
13 //Dämpfung [N*s/m] damping
200 //Bruchkraft [N] breaking load
0 -1 0 //Achsvektor axis vector
0.2 //Reibungskoeffizient in Spurrichtung [-] coefficient of friction in trace direction
0.7 //Reibungskoeffizient quer zur Spurrichtung [-] coeff. of fric. transverse direction
0 //Kanal channel
0 //maximaler Ausschlag [°] maximum deflection of the wheel when steering



Roman

[ggunners]

Thanks Roman,

Wonderful information.

One more question and I apologize for my ignorance, how does one calculate the ex and ey vectors for a WING element.

Does ex relate to sweep and ey relate to dihedral?

Is a polyhedral wing approximated with dihedral or do we add additional wing components?

Thank you, I know you are very busy.

-- ggunners

[Roman Moeller]

Hi ggunners,

ex does not directly relate to sweep or dihedral. Maybe an example is more clear.

If you want a wing with no sweep and no dihedral, ex = (1, 0, 0) and ey = (0, 1, 0)
For a wing with 20° sweep you rotate these vectors about the z-axis: ex = (cos(20°), sin(20°), 0) = (0.9397, 0.3420, 0), ey = (-0.3420, 0.9397, 0)
For a wing with 5° dihedral you rotate the vectors about the x-axis: ex = (1, 0, 0), ey = (cos(5°), 0, -sin(5°)) = (0.9962, 0, -0.0872)
This example is for a wing element on the right side. Of course one can also combine sweep and dihedral, but then the numbers of the two rotations get more complicated.

For polyhedral you add different wing elements.

Roman

[ggunners]

Thank you Roman, that makes sense.

I just plotted both the Pitts and the Sukhoi using the .25*span factor for all wing surfaces and the Sukhoi plots OK.

The Pitts fuse is still offset in the negative X direction (backward). I have to use a factor of .32*span to get the fuselage (surface 5) to align with the motor and tail. Am I doing something wrong or should I move the surface 5 position forward to match?

Sorry to be picky, just trying to understand.

-- ggunners

[Roman Moeller]

[ggunners]

[Squidbait]

Hi all - I'm a total newb here, but I've been playing with FMS for a few months now, and I think it's great! I'm mucking about with alpha 8 right now, and I'm trying to figure out how to get some of the parameters for the .par file. Many of them are fairly obvious, but how do you calculate the moments of inertia? Or the product of inertia? And how did you work out the cd's (not to mention a few other parameters) for the models without wind-tunnel data?

Also, how would you configure the surfaces for a v-tail like an aerobird, or for that matter, the Diamant? I thought I understood that each surface was a wing, so surface 1 is right wing, surface 2 is left wing... but the Diamant model has 5 ???

Cheers, keep up the good work,

SB

[ggunners]

Hi Squidbait,

Check out my write up in an Excel spreadsheet on .

It'll answer some questions.

The surfaces refer to objects that cause drag and lift including wings and control surfaces. In the Pitts, surface 1 is the left wing top, 2 is right wing top, 3 is elevator, 4 is rudder, 5 is fuse, 6 is lower right wing and 7 is lower left wing.

I've not figured out the moments or Polar coordinates except that wings are treated different than fuselages.

Have at it. Let us know if you discover something.

-- ggunners

[Squidbait]

[jon]

Hi.

Trying to figure out the par files for the FMS v.8.
It was a great deal of help in the spread sheet from ggunners and the topic from Roman Moeller.

However there is some more questions:

"Rotationsträgheitsmoment von Propeller und Motor [kg*m^2] (rotation moment of inertia).
Motorenwiderstandskonstante [Pa] (friction constant of engine)
Motorenwiderstandskonstante [Pa*s^2] (friction constant of engine)"

how do I find out these values?

"Anzahl Elemente (number of elements)
Alle Elemente sind gleich gross (all elements have equal size)"

What is an element?

and what does the "polare" do?

I think I could find it out myself, but there is a faster way to ask somone who have worked with it.

???