Analysis of Dynamic Ground Effect for a Jet Transport in Crosswind

Abstract

Flight-data-recorder data of a jet transport in landing in the presence of varying crosswind are analyzed for static and dynamic ground effects. The flight data are analyzed with a new approach based on a fuzzy logic modeling technique. The objective of fuzzy logic modeling is to establish the dynamic longitudinal aerodynamic models as functions of ground height and sink rates in addition to the conventional aerodynamic variables that include the angle of attack, its time rate of change, pitch rate, reduced frequency, sideslip angle, elevator angle, Mach number, roll rate, stabilizer angle, and flap angle. The resulting aerodynamic models for the normal force and pitching moment coefficients provide data for the analysis of static and dynamic ground effects. The numerical results at a constant angle of attack show that ground effect appears to become more significant as the sink rate increases, and the crosswind tends to induce a reduction in the normal force coefficient at a constant angle of attack when the aircraft is close to touch-down. In addition, the crosswind will make the pitching moment more negative. It also reduces the control effectiveness. The adverse ground effect is determined not being caused by the reduction in lift-curve slopes.