[Tristan Lall]

What's your price range? Cloudcap and Micropilot make autopilot modules for UAVs that will definitely keep a plane in the air, but they're very expensive (thousands of US dollars).

On the much lower end of the cost scale, there are infrared units that track the horizon, and will try to keep the plane level, by mixing the pitch and roll controls. (I'd estimate this would cost around $150 USD.)

As a sort of medium-cost option (several hundred US dollars), something like the Innovation First Mini-RC controller could be used to interpret the control inputs from your radio receiver, and mix them with sensor inputs from accelerometers, compass sensors, etc. to prevent sudden motions. This will require a lot of programming, and certainly wouldn't be easy.

But here's the big catch, however you do it: if I recall correctly, India's Air Ministry is very strict about its regulations for unmanned aerial vehicles. Make sure that you're not doing anything against their rules. A number of Indian university-based competitiors in the International Aerial Robotics Competition have suffered because they weren't allowed to test their aircraft freely.

Overall, unless you've got access to significant amounts of money, and have the time to build and integrate sensors, you probably would be better served by just watching it closely when it flies, and learning to fly it better. See if you can track down an experienced model plane pilot in your area who can give you some lessons.

Also, this forum is generally dedicated to the FIRST Robotics Competition. Your questions are certainly welcome, but be aware that many topics on this site are specific to the hardware used in FIRST.