In this paper, we present an attitude controller design for a 3DOF flight control experiment apparatus, the "Quanser UFO", as an application of the multi-input. multi-output (MIMO) nonlinear tracking and decoupling control technique based on trajectory linearization method. The controller consists of two parts: a pseudo-inverse of the plant that computes the nominal control, and a linear time-varying regulator that stabilizes and decouples the tracking error dynamics. For regulating the attitude and the body rate tracking errors, inner and outer loop PI controllers are employed, which are designed by time-varying bandwidth PD-eigenstructure assignment. The presented trajectory linearization method for tracking error stabilization and decoupling is proved to be an effective method to achieve the "good" flying qualities by simulation tests.