F-4 Flyable Phantom II Question

[flynby]

I downloaded this file from Perfect Flight:

http://www.fs2000.org/index.php/dow...32309-fsx-us-air-force-f-4-phantom-ii-op-bolo

Tried to change contact points in aircraft.cfg. I want the aircraft to sit level on the tarmac, if possible.

No luck changing the point.0 or changing the static_pitch=0.000000 or the
static_cg_height=4.917881

Question: Does this have something to do with the mdl file also?
Thanks

 

[hairyspin]

Static height determines what height a model appears above the runway when it's loaded in the sim. Static pitch is the angle the model makes with the runway when loaded in the sim - a tail dragger is nose up, tail down; helicopters sit pretty level.

Then (simulated) gravity and physics take over and the model DROPS until the contact points touch the runway.

These are the contact points for the stock C172:-

        //0  Class
        //1  Longitudinal Position        (feet)
        //2  Lateral Position             (feet)
        //3  Vertical Position            (feet)
        //4  Impact Damage Threshold      (Feet Per Minute)
        //5  Brake Map                   (0=None, 1=Left, 2=Right)
        //6  Wheel Radius                (feet)
        //7  Steer Angle                         (degrees)
        //8  Static Compression           (feet)  (0 if rigid)
        //9  Max/Static Compression Ratio
        //10 Damping Ratio               (0=Undamped, 1=Critically Damped)
        //11 Extension Time              (seconds)
        //12 Retraction Time             (seconds)
        //13 Sound Type
[contact_points]
point.0 = [B][COLOR="Red"]1[/COLOR][/B],  0.90,  0.00, [COLOR="RoyalBlue"]-4.09[/COLOR], 1500, 0, 0.5, 22.0, 0.25,2.5, 0.7, 0.0, 0.0, 0
point.1 = [B][COLOR="red"]1[/COLOR][/B], -4.70, -4.50, [COLOR="royalblue"]-4.01[/COLOR], 3500, 1, 0.5,  0.0, 0.3, 2.5, 0.7, 0.0, 0.0, 2
point.2 = [B][COLOR="red"]1[/COLOR][/B], -4.70,  4.50,[COLOR="royalblue"] -4.01[/COLOR], 3500, 2, 0.5,  0.0, 0.3, 2.5, 0.7, 0.0, 0.0, 3
point.3 = 2, -3.90, -18.0,  3.00, 1800, 0, 0.0,  0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 5
point.4 = 2, -3.90   18.0,  3.00, 1800, 0, 0.0,  0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 6
point.5=  2,-20.23,   0.0,  0.30, 1800, 0, 0.0,  0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 9
point.6=  2,  1.48,   0.0, -2.17, 1800, 0, 0.0,  0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 4
point.7=  2,-22.80,   0.0,  5.83, 1800, 0, 0.0,  0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 7
point.8=  2, -4.90,   0.0, -2.00, 1800, 0, 0.0,  0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 8

max_number_of_points = 21

static_pitch=3.02                //degrees, pitch when at rest on the ground (+=Up, -=Dn)
static_cg_height=3.765           //feet, altitude of CG when at rest on the ground

Points 0, 1 and 2 have the first number in each line as 1 - this means these are landing gear points. The value that makes the difference to how the aircraft settles on the runway is the fourth value in each line - the vertical position.

That's what needs adjusting if you want to change how the model sits on the runway.


BTW, the sim doesn't care what the model looks like, only the contact points determine how it sits. The .MDL has no influence.

 

[n4gix]

To further the point regarding "static_height," this is also the height used whenever the sim is in Slew Mode (Y key).

Normally, this distance will be very slightly more than the main gear's contact points...

...because you don't want the a/c to drop too far, lest you break the gear!

 

[lionheart]

............and to add to the nightmare of contact points, you are also dealing with the suspension (landing gear) in a state of compression via its weight layout. If the nose is heavy, the nose gear will be overloaded and be lower to the ground then usual. Moving weight back in the 'aircraft.cfg file' (open with Windows Notepad to edit), then the nose will sit higher. Fuel is a good thing to move to center when the nose is too low. Vise versa if too high. Moving the main gear contact points front or rear can effect 'angle' that the plane is sitting at.

Sooooooooooooooooooooooooo many variables..... Makes my nose hairs fall out at times...

 

[hairyspin]

............and to add to the nightmare of contact points, you are also dealing with the suspension (landing gear) in a state of compression via its weight layout...
....Moving the main gear contact points front or rear can effect 'angle' that the plane is sitting at...

Good points Bill, so somewhat intrigued I d/led the F4 and had a play. The model sits nicely on its wheels, so the contact point positions seem to work. What is slightly irritating is the pitching bounce when the model first loads: the main gear is fairly stable on the runway, but the nose bounces up and down by a couple of feet before settling.

Looking at the balance figures in AirWrench with edit disabled, the main gear is just a short way behind the reference position and the CoG, whereas the nose gear is a long way in front of it, so the potential for bouncing is considerable.

Looking at the contact points themselves, the nose and main gear have the same maximum compression and static compression, so considering the balance described, the model is bound to sit with its nose in the air.

There's a fair bit adjustment needed to make the model sit the way you want it, but it's going to mean the gear not aligning with the runway as well as it presently does. I'm fairly sure you'd need the modeller's cooperation to change the gear as modelled before you'd get the aircraft sitting the way you want and the gear still sitting nicely on the runway.

Really good-looking model, BTW! (I'm keeping it on my system... )

 

[flynby]

It is totally amazing how difficult it is to make one of these simulator aircraft fly!!
I thought just designing was bad enough. I am really beginning to appreciate the time and effort people who create these models must put in.
I thank all of you for your time and help. I salute all of you.