Building a cheap portable artificial horizon.

Hi,
After some time testing things look ok on the ground!
I am using the MPU-6050 and the arduino tv-out library.
I am calculating x and y using the kalman filter which i have found on github.
My problem is when testing in flight almost nothing happens ,the y axes responds a bit but also not much.
I think that this is related to the g force on the senors but i am not sure.
Does anybody have an opinion?