Gain-scheduled linear-quadratic-regulator synthesis for the centre of gravity variations of Boeing 747-100 longitudinal modes

For the variation in the centre of gravity (CG) of Boeing 747-100 (B747-100) longitudinal flight, the gain scheduling (GS) method is proposed to manage it over the flight envelope. The full-state feedback linear quadratic regulator (FSFLQR) has been synthesised with the GS, named (GS-FSFLQR), to obtain a realistic controller for Mach numbers (M) and altitudes (H) envelope. Such a practised control law demonstrates the CG mean aerodynamic chord (MAC) shifts correlated with M-H and actuator actions. The intermediate variable responses have been accomplished at (M, H) simulations of (0.2, 0), (0.5, 6096 m) and (0.9, 12190 m). Local controllers at M and H scheduled parameters are gained using the cubic spline method of 0.2 to 0.9 and sea level to 12190 m. Swift levelled convergences illustrated the B747-100 CG variations throughout most responses for a coupled elevator and throttle-controlled flight. These findings are validated for the flying quality requirements showing the competent merits of the GS-FSFLQR as opposed to without control flight. The maximum elevator capacity transmits the CG from the 17% MAC at (0.3, 6096 m) to 30% MAC at (0.7, 3048 m), whereas the maximum throttle occurs for the CG at 25% MAC at (0.5, 6096 m). Their minimum operations lead to 22% MAC at (0.6, sea level). The dominated CG location of the elevator is fore than 25% MAC whereas the aft and fore locations of the throttle float around that. 50% actuator effectiveness due to operable elevator and throttle adequately copes with the CG longitudinal stability.