From physics perspective the force (=dynamic pressure) increases with the square of the speed, so it
From physics perspective the force (=dynamic pressure) increases with the square of the speed, so it's correct that it's non linear.
edit: Although the F-4 implements an artificial feel system and is not directly coupled with the control surfaces, that may not be the case (haven't read the docs about the F-4 control stuff yet)
edit: Although the F-4 implements an artificial feel system and is not directly coupled with the control surfaces, that may not be the case (haven't read the docs about the F-4 control stuff yet)

