Effect of wing tip vortices on a trailing aircraft

T HE effect of trailing vortices from a large leading wing on a trailing aircraft is studied experimentally. The aerodynamic response of the trailing aircraft is examined through measurements of lift, drag, and pitching moment for various angles of attack of the two models and different separation distances between them. The results show that trailing vortices cause a remarkable loss of lift on the trailing aircraft. This phenomenon becomes more significant as the angle of attack of the leading object is increased. Results demonstrate that in order to maintain the same lift, drag would increase as the leading wing angle of attack is increased. Nomenclature C = chord length of the trailing aircraft CD = drag coefficient of the trailing aircraft CL = lift coefficient of the trailing aircraft CM = pitching moment coefficient of the trailing aircraft X = separating distance between the two models in the horizontal plane Y = separating distance between the two models in the vertical plane a. = trailing aircraft angle of attack (} = leading wing angle of attack Contents The effect of wing tip vortices on trailing aircraft has been an aviation safety problem since the introduction of large airliners in the early 1970s up to now. Hallock and Eberle1 presented a review of the efforts made to understand the nature of trailing vortices. Vortex measurements were taken at several major airports to form the Vortex Advisory System that helped in reducing the vortex imposed separation distance.2 The Federal Aviation Administration obtained measurements of the swirling velocities in the vortices of full-scale aircraft.3 On the other hand, there have been many efforts to reduce the hazard of trailing vortices.46 In this paper, the effect of trailing vortices from a wing on the lift, drag, and pitching moment of a trailing aircraft is investigated. A low-speed, nonreturn type of wind tunnel with a test section of 0.5 x 0.7 x 2.0 m3 and a maximum speed of 45 m/s was utilized. The forces and moment were measured by an external three-component balance. The leading wing was a NACA 0015 of rectangular planform with a wing span of 0.498 m, a chord length of 0.275 m, and an area of 0.137 m2. The wing of the trailing aircraft was a straight-taper ed untwisted wing of airfoil section RAE 101 and 10% thickness with a wing span of 0.44 m, a mean aerodynamic chord of 0.079 m, and an area of 0.03476 m2. The two models were installed symmetrically at the center of the test section. The distance between the two models was