Date of Award


Document Type


Degree Name

Master of Science


Department of Aeronautics and Astronautics

First Advisor

Milton E. Franke, PhD


This experimental study adequately identified the ground effect region of a lambda-shaped unmanned combat air vehicle (UCAV). The lambda planform used in this study was originally tested in a previous experiment to determine the stability and control characteristics generated out-of-ground-effect. The following study extends the existing database by analyzing the inherent aerodynamic behavior that is produced by employing trailing edge flap deflections while flying in-ground-effect (IGE). To accomplish this objective, static ground effect tests were performed in the AFIT 3? x 3? subsonic wind tunnel where a ground plane was used to simulate the forces and moments on the UCAV IGE. Removable aluminum flap pieces were attached to the model, in a split flap configuration, along the midboard and outboard trailing edges of the UCAV, and the corresponding IGE data was collected for symmetric and asymmetric deflections of +10o and +20o. Based on the results of this study, the ground effect region for the lambda UCAV, with flaps deployed was characterized by an increase in the lift, a reduction in the induced drag but an increase in the overall drag, and an increase in the lift-to-drag ratio. These trends were noted in previous ground effect studies for aircraft with trailing edge flaps, and similar aspect ratios and wing sweep. Additionally, a flow visualization analysis revealed that a vortical flow pattern, that is characteristic of delta wing configurations, developed over the upper surface of the wing at high angles of attack.

AFIT Designator


DTIC Accession Number