<p>Controlling the aircraft during transition from vertical flight mode to forward flight poses a challenge to researchers as it involves highly nonlinear dynamics during the transition phase. This paper presents a novel decoupled control approach based on incremental nonlinear dynamic inversion (INDI) for hybrid tiltrotor aircraft, designed to address the challenges of complex aerodynamic and inertial couplings inherent in such platforms. By introducing key assumptions that simplify the system dynamics and their effects treated as manageable disturbances, the proposed method achieves decoupled control of the aircraft’s roll, pitch, and yaw motions without compromising overall stability and performance. The standard fixed-wing flight dynamic model is established, incorporating the quadcopter’s flight dynamic model. The transition from vertical take-off to forward flight is realized by tilting the quadcopter rotors as a function of airspeed and stall speed. A nested proportional integral and derivative (PID) controller governs VTOL and transition phases, while decoupled INDI controller is employed in forward flight. For validation, the strategy is applied to small surveillance UAV and evaluated across vertical take-off, transition, and cruise regimes. Navigational state estimation is achieved using the cubature Kalman filter (CKF), with two variants, complementary CKF (C-CKF) and integrated CKF (I-CKF), developed for attitude, position, and velocity estimation. Closed-loop simulations confirm smooth transition dynamics with minimal overshoot, demonstrating suitability for hybrid tiltrotor applications.</p>