Simviation Forums

im currently working on a projet here, and its all done...the FDE's i did them as i do with most of my projects but i have a little problem, the model "twitches" and jumps when it is sitting on the ground. its a pain...i have no idea how to fix this problem, i already fiddled with the gear dampin or w/e but still no luck, i use the 1% spreadsheet or my FDE's. any help is much appreciated

Hi Felipe,
Sometimes, increasing the inertia values in the aircraft.cfg can cure this problem.


Kev

Yep, that's what I was going to suggest. Double the values and see what happens. Then you can reduce the numbers until it starts to jig around again.

thnx guys ill try that

Just to help you rule out the possibility that your contacts points are involved, it wouldn't hurt trying out this technique.

http://www.sim-outhouse.com/index.php?l ... es&page=cp

Just a suggestion.

Got the same problem, only when I use the 1% spreadsheet, the contact points are OK, so I'll also re-set the inertias.....keep you posted.

First, and most importantly, get the contact point data to match up with the visual model.  You can get those coordinates right from your modeling program.  Get gear coordinates from the bottom center of the tires tread with the gear fully extended and fully hanging.  You can visually verify these coordinates by plugging them into the Lights section.  Use a Nav light for best results.

Well you're collecting that data, you may as well get all the other coordinates you need for engines, lights, 25% MAC, crash points, etc.

Once you have the contact point data correctly set, then calculate your proper gear spring rates and damping.  These numbers should be entered into the .air file, table 1004.

Main gear = gross weight * 2.72
Main gear damping = gross weight * .34

Center gear = gross weight * 2.04
Center gear damping = gross weight * .24

Finally, tweak your contact point static compression and max/static ratio so that the total movement possible equals your animated gear suspension movement (with a fully loaded aircraft).

Ended up with the following MOI:

roll 34100
pitch 34100
yaw 40300

Also re-set the touch points ( the "good" points I had in the AIR were being overwriten by the cfg!!) also used Milton's recommendations for the gear damping. MUCH better, still "tweaking" but a major improvement.
Hope this helps the others.