A flying wing UAV trimmed with propeller thrust

The existing aircraft configuration cannot satisfy the requirements for the longitudinal stability and flight performance of a static and stable fixed-wing aircraft. This is especially true for a flying wing aircraft, whose flight performance deteriorates in maintaining its static stability. Hence, we propose a new aerodynamic configuration that uses the propeller thrust to trim longitudinally the flying wing of an unmanned aerial vehicle (UAV). In the configuration, the positive cambered airfoil is used to replace the conventional reflex cambered airfoil so as to raise the lift to drag ratio and lift of the UAV, which is longitudinally trimmed by wash-out and propeller thrust. We use the commercial software CMARC and empirical formulate to calculate the aerodynamic force of the UAV and analyse its stability. During its stall, the calculation results are in good agreement with the wind tunnel experimental results. We also study the matching between the propeller of the UAV and its motor and establish the mathematical model to calculate the efficiency of its power system and merge it into the overall design by taking into account the difference in power at different mission stages. We use the genetic algorithm to optimize the overall parameters of the flying wing UAV trimmed and not trimmed with propeller thrust. The optimization results, given in Table 1 and Fig. 9, show preliminarily that: (1) the amounts of wash-out and sweepback of the UAV longitudinally trimmed with propeller thrust are reduced and its coefficient of maximum lift available and wing loading increase, thereby reducing the wing area; this leads to a larger aspect ratio when the wingspan is kept constant; (2) because of few elevon deflections and reduced wash-out, the lift to drag ratio increases during cruise and loitering. Finally, we study the effects of overall parameters on the performance of the UAV trimmed with propeller thrust.