Wind tunnel experiment of UTM-LST generic light aircraft model with external store

Abstract

This paper discusses the impact of the external store on the aerodynamic performance of the light aircraft model in the subsonic region. Light aircrafts are commonly used for pilots training, survey, leisure and transportation. To date, there have been a lot of small aircrafts used for strategic purposes where an external store, either external fuel storage or armament, has been installed on its wing. Examples of such aircraft are KAI-KA1, A29 Super Tucano, and Beechcraft AT-6. Therefore, it is important to study the effect of this external store installation on the aerodynamic characteristics of a small aircraft. An available light aircraft model of UTM Low speed wind tunnel (UTM-LST) has been modified so that a generic external store can be mounted on the lower surface of the wing. Two set of experiments were carried out on the model which were; experimental with an external store followed by experimental without external store as a benchmark of tested configuration. The experiments were conducted at two different speeds of 26 and 39 m/ s that correspond to Reynolds numbers 0.4 × 106 and 0.6 × 106 respectively. Three measurement techniques were employed on each configuration. The first measurement was the 6 component forces and moments measurement technique. The second technique was the pressure measurement on the wing, and the final test was the tufts flow visualization. The result of steady balance indicated that the external store has no effect on the coefficient of lift at low attack angle. However, it showed that there was a reduction of lift coefficient by 2% at higher angle of attack. The data showed that the coefficient of drag increases by 4% when the external is installed. Surprisingly, the installation of the store has insignificant effects on the pitching moment coefficient. An interesting feature observed from surface pressure studies where, the results showed that the pressure coefficient increased when the external is mounted on the wing at a low angle of attack. Such changes, however, do not occur at high angle of attack.