A SMALL AIRCRAFT IN HAZARDOUS WAKE NEAR GROUND USING UNSTEADY VORTEX LATTICE METHOD

The interaction between small aircraft and vortex system generated by another much larger aircraft is investigated. An aerodynamic model based on the modified unsteady vortex lattice method and the method of images was developed. A simple wake model can be developed using this vortex system. The large aircraft represented by a large wing, while, the small aircraft represented by a small wing, were used in this study. Investigation was done for the small aircraft, as it is entering and flying parallel to the wake left by the larger aircraft near ground, during aircraft landing operation, with all aerodynamic surfaces assumed to be of zero thickness. The lateral position of the small wing with respect to the large wing center line is assumed to be variable. Changes in lift, drag, pitching moment and rolling moment coefficients, for the small aircraft, are calculated and presented for deferent cases of study. A case study shows that, as the small aircraft enters the wake left by a large aircraft, a sudden decrease in aerodynamic forces and moments takes place. This situation is more noticeable and dangerous near ground as the small aircraft approaching the ground during landing or take off operations. The lateral position of the small aircraft with respect to the larger one has a great effect, where the lift force could become unsymmetric on both sides of the small wing. This could put the small aircraft into a rolling motion, where it could be deviated from its flight path during the landing or take off operations, an accident might be the result.