Question

A small airplane is flying behind a large (heavy) one, with the centerplane of the small airplane just slightly outboard of a wingtip of the larger one. a. Draw in the cross-sectional plane (so, from behind of the small airplane, looking upstream at both airplanes) a reasonable rendition of the large airplane's tip vortex and the resulting velocity field felt by the small airplane. By "velocity field”, we mean a velocity profile induced by the tip vortex of the large airplane. Ignore the tip vortices/wake of the small airplane.

Answer 1

When the small plane is directly behind the large planes wing tip vortex, it causes the air to build up under the smaller airplane, as a result, the relative airflow to the wings of the smaller plane changes, which in turn increases the effective angle of attack of the smaller aircraft.

When the angle of attack increases, there is a sudden increase in the lift of the smaller aircraft occurs which in turn causes the aircraft to pitch up, and also slightly rolls the aircraft towards the left.

WING TIP VORTEX 83

From the above diagram, velocity field is represented by small arrows and lies in the cross sectional plane of the smaller airplane and the wing tip vortex of the larger airplane is in 3D space. The wing tip vortices of the smaller plane is not drawn in the above image.

(This is just a hand-drawn image of the velocity field and a not computationally accurate)