Influences of External Store on Aerodynamic Performance of UTM-LST Generic Light Aircraft Model

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 normally used to train pilots, survey, leisure and transportation. To date, there have been a lot of small aircrafts were used for a 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; the experimental with the external store and followed by the experimental without external store as a benchmark of tested configuration. The experiments were conducted at 2 different speeds of 26 and 39 m / s that corresponding to 0.4 × 106 and 0.6 × 106 Reynolds numbers 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 while the final test was the tufts flow visualization. The result of steady balance indicates that external store has no effect on coefficient of lift at low attack angle but it shows 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. Suprisingly, the installation of store does not give significance effects on the pitching moment coefficient. An interesting feature is observed from surface pressure studies, the results obtained show that there is an increase in the pressure coefficient if the external is mounted on the wing at a low angle of attack, while this change does not occur at high attack angle.