How can I make a plane more stable??

[eellduaarr]

I recently downloaded a plane from this site, and I found it very unstable when flying manual(no autopilot). It's vey hard to get it aligned with the runway, the turns are a mess!! The auto rudder option is checked, by the way, and also already tried with winds calm. The plane is an MD-83.

Yaw damper is not working either, how can I activate it? Even with the command crtl + D, a "YAW DAMPER OFF" message keep showing in the panel.

..:: elduar ::..

[stpatrick]

Some downloaded planes are overweight, and that can make them difficult to handle. Check the Fuel and Payload settings.