Experimental Aerodynamic Analysis of a 4.6%-Scale Flying-V Subsonic Transport

Abstract

The experimental investigation into the aerodynamic characteristics of a 4.6%-scale half-model of a flying-wing transport aircraft is detailed. The study is performed in an open-jet wind tunnel where forces and moments are recorded using a 6-axis balance. Two control surfaces in the outboard wing are deflected to measure their effect in terms of lift, drag, and pitching moment up to a Reynolds number of 1 million. The results are subsequently combined with the estimated thrust force using a flight mechanics model of the aircraft in order to predict the most forward and most aft center-of-gravity locations for which the aircraft can be balanced with the control surfaces, while still being statically stable. The results show that the aircraft can attain an untrimmed maximum lift coefficient of 1.02 at an angle of attack of 35 degrees. Furthermore, the pitching moment around the leading-edge of the mean geometric chord is negatively correlated to the angle of attack up to 19 degrees, after which a strong pitch-break is observed, making the aircraft statically unstable. This is associated with a forward shift of the aerodynamic center to a longitudinal position 35%c ahead of the moment reference point which is caused by the formation of strong vortices over the wing surface. The effectiveness of the control surfaces hardly deteriorates with angle of attack and all three control surfaces are shown to be effective up to the maximum lift coefficient. Analysis shows that the center-ofgravity location should reside between [-7.5; 0.5] %c, in power-off conditions, and between [-6; 1] %c, in power-on conditions, from the leading edge of the mean geometric chord to ensure an ultimate static stability margin of 4.4% as well and a minimum landing speed of 20 m/s. Within these ranges, trimmed maximum lift coefficient values of 0.68 and 0.66 can be achieved respectively in power-off and power-on conditions.

Aerodynamic Model Identification of the Flying V from Wind Tunnel Data

“…[2], Palermo and Vos performed wind tunnel tests on a 4.6% scaled wind tunnel modelt at a Reynolds number of one million. They demonstrated an untrimmed maximum lift coefficient of 1.02, an aerodynamic center excursion over angle of attack as much as 55%c due to vortex formation, and a trimmed maximum lift coefficients are 0.68 [5]. Fig.…”

“…The test-article is a thin-walled fiber-glass wing, with three control surfaces. The exact dimensions and positions of this model are reported in a previous study [5]. The reference area of the model is S = 0.9345 m 2 , has a semi span of b/2 = 1.495 m, and a reference chord ofc = 0.729 m. The wing consists of two tapered wing trunks with a leading-edge kink positioned at 63% of the semi-span.…”

Effect of Engine Integration on a 4.6%-Scale Flying-V Subsonic Transport

“…Combining the experience gathered by Palermo [7], Viet [8]and Ruiz Garcia [19] on the testing of the half model Flying V, adding common practice of engine-integration testing, and taking into account the available resources at Delft University of Technology, results in the setup discussed in this section. First the wind tunnel is discussed, followed by a detailed description of the half model and the used measurement equipment and methods.…”

“…However, before the SSFT model can take to the air, the flight characteristics of the design are to be tested numerically and in the wind tunnel. So far, numerical and experimental investigations have been performed to assess the performance, longitudinal static stability and control characteristics of the sub-scale model [4,7,8]. All of this research was either purely numerical or only involved the wing.…”

“…The planform dimensions are provided in Figure 3. The wind tunnel model represents exactly half of the Flying V SSFT model, which is a 4.6% geometrically scaled model of the full scale design [7]. Zigzag strips are positioned at 5% chord to ensure a turbulent boundary layer flow over most of the wing surface.…”