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The problem considered here is that of predicting the non-linear behavior of delta wings at moderately high angles of attack and low speeds. In this operating regime, vortex lift and vortex bursting are important in determining the aerodynamic forces on the wing. The analysis begins with a vortex-lattice model to determine the circulatory lift and the leading-edge suction force. The vortex lift is then calculated from the suction force assuming that the leading edge vortices have not burst. The circulatory and vortex lift are then corrected for vortex bursting and flow separation using a semi-empirical approach to estimate the burst locations of the leading edge vortices.

A numerical non-linear lifting line model is presented which predicts the behavior of a wing beyond the stall given two-dimensional airfoil data. The model, although relatively simple, appears to predict fairly complex stall effects including hysteresis and unsymmetrical spanwise lift distributions with partial-span stall. The numerical model runs rapidly on an IBM-Compatible PC and does not require any extensive CFD-type of calculations. Because of its speed and apparent accuracy in modeling the physical behavior of a stalled wing, it may find application to the simulation of airplane motion beyond the stall. Although the numerical model was developed independently here a similar approach has been tried previously by others. These previous efforts and a comparison with the present results are discussed briefly.

During the past several years the problem of wake turbulence has received considerable attention. As a result of research programs sponsored by the Federal Government and private industry, the hazard of wake turbulence to light aircraft has been well documented. In this paper it is emphasized that relatively large aircraft can also be susceptible to vortices generated by large jet transports. This conclusion is based upon a review of accident records and the results from a computer simulation of the aircraft-vortex interaction. The computer simulation consists of the equations of motion with six degrees of freedom as well as control input by the pilot. Procedures are recommended for avoiding dangerous vortex encounters.