Effects of propeller thrust trimming on tailless unmanned aerial vehicle performance

Abstract

Flight performance and longitudinal static stability are two contradictory requirements for aircraft. This is especially true for a tailless configuration, whose flight performance is traded for static stability. A new tailless gull wing configuration with propeller thrust trimming is proposed in this paper. It is expected that the propeller thrust can help to provide a nose-up pitching moment and improve the flight performance. In the present configuration, a cambered airfoil is used to increase the lift-to-drag ratio as well as the maximum lift coefficient. Two approaches are adopted to obtain the nose-up pitching moment. Firstly, the thrust line is shifted below the center of gravity to make a positive contribution to the pitching moment. Secondly, the thrust vectoring is employed to trim longitudinally instead of elevon deflection. The wind-tunnel data indicate that the lift-to-drag ratio and maximum lift coefficient increase notably with the help of propeller thrust trimming. To determine the performance benefits of the gull wing with propeller thrust trimming, a conceptual design environment of the electric-powered unmanned aerial vehicle is developed by integrating the modules of the conceptual parameters, aerodynamics, stability, propulsion, weight, performance, as well as optimization. The optimization results suggest that, compared with the two other conventional tailless configurations, the gull wing with propeller thrust trimming results in 20 and 34% endurance increase. Flight tests of a 2.5 kg built aircraft demonstrate the aerodynamic feasibility of the gull wing with propeller thrust trimming concept.

A method for evaluating the wind disturbance rejection capability of a hybrid UAV in the quadrotor mode

“…The higher the maximum wind velocity is, the stronger the wind disturbance rejection capability. From the above analysis, the 6-DOF static equilibrium equations can be used to quantify the wind disturbance rejection capability of the QFHUAV in the quadrotor mode approximately, and these static equilibrium equations can be established according to equations (2) and (3). To ensure safe takeoff and landing in high wind speed conditions, operators usually forecast the wind direction in mission planning and path planning to keep the angle between the heading of a QFHUAV and the negative direction of the wind as small as possible.…”

“…Currently, UAVs are widely used in various military and civilian applications due to their flexibility in configuration, low manufacturing and operating costs, and not risking pilots in demanding missions, such as surveillance, tracking, environment observation, fish finding, and law enforcement. [1][2][3] Most UAV applications require UAVs that are capable of doing a wide range of different and complementary operations within a composite mission. 4 However, conventional fixed-wing UAVs generally have good cruise performance, can fly for long durations at high speeds, and are independent of wind situations within a wide range, 5 but these UAVs suffer from the requirement of runways or special launch and recovery equipment such as catapult launchers, parachutes, or nets for takeoff and landing.…”