ı have a talon model in gazebo garden,mission planner as GQ with SITL
ı converted one motored talon model to two motored one ,adjusted the servo outputs according to my models sdf.Original param file is from: https://github.com/ArduPilot/SITL_Models/blob/master/Gazebo/config/skycat_tvbs.param Each of the motors separately and successfully can spin at cw ccw direction but talon cannot takeoff the propellers just do spin and vehicle stay on ground i have been struggling with same problem for a while and i cant seem to have any progress.
Any help appreciated 
@ssmenekse, it’s difficult to tell what might be going wrong without the model.sdf file. If you are not getting any thrust with your modified model, but the props are spinning, it suggests that you may not have lift-drag plugins configured for the new motor / prop links.
Combinations I’ve tried for forward tag:
-1 -1 ,+1 +1 -->rotates around itself
+1 -1 → stays as it is
-1 +1 -->goes backward
if it is going to be more helpful for you i can directly share model.sdf too.
Yes, probably easiest. If you have a git hub fork of SITL_Models and a branch with your changes, that would be best.
sorry, it took quite a time. I also added param.file too.