TABLE OF CONTENTS The ground effect is a physical phenomenon that results from the proximity of the moving flight vehicle to the ground, mainly because close to the ground the downward flow is interrupted by the ground. Loosely speaking, for example, during the landing phase, the ground effect leads to increasing pressure below the wings as the aircraft approaches the ground and thereby reduces the sink rate. Such effects are encountered, in general, for altitudes above ground level lower than the wing span. They have a dominant influence on the aircraft landing and takeoff performance, which are safety-critical flight phases. In general, the three main effects resulting from ground effect are8 1) reduced downwash angle at the tail, 2) increase in the wing-body and the tail lift curve slopes, and 3) reduction in the induced drag. The ground effect mainly influences longitudinal motion, although, in general, almost all other aerodynamic derivatives might be slightly altered. Ground effect updates from flight data are usually necessary to accurately reproduce the landings and takeoffs, as well as for better assessment of touchdown sink rate.
The basic theory on ground effect was developed by Wieselsberger, analyzing it through a simple model based on Prandtl s lifting-line theory.38 ,39 To date extensive research has been devoted to this important topic. There is a vast literature, including dedicated text books, on ground effect modeling based on theory, numerical investigations, wind-tunnel tests, and determination from flight tests.40 44 A detailed discussion on the theoretical background...
