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Ground Effect Influence on the Aerodynamic Characteristics of Ultralight High-Wing Aircraft – Wind Tunnel Tests

Abstract The ground proximity may significantly improve the performance of the aircraft, but in some conditions, it affects its stability. The gain of lift which and reduction of drag during low altitude flight is known as the wing in ground effect (WIG effect). It may concern aircrafts or WIG-crafts (ground effect vehicles). In the article experimental results of the wind tunnel test of an aircraft in ground effect has been presented. The main aim of the test was to investigate the ground effect influence on aerodynamic characteristic of the of the ultralight high-wing aircraft model during early take off, taxiing or final landing stage. Investigation was carried out in the 1.5 m diameter low speed T-1 wind tunnel in the Institute of Aviation in Warsaw. The velocity was 32 m/s and Reynolds number related to the aerodynamic chord was equal about 0.37·106. Tests were performed for chosen angles of attack in range 0-10°. During investigation, the strain gauge balance measurements and Particle Image Velocimetry (PIV) flow visualization technique were applied. Tested model position was relatively close to the ground. It was found, that the ground proximity has significant influence on the pitching moment. The normal force was increased and the axial force is decreased due to the WIG effect, which is compatible with the theory. It has significant meaning for control aircraft issue and safety.