INFLUENCE OF THE BALLISTIC PROTECTION ON AERODYNAMIC HELICOPTER CHARACTERISTICS

This paper contains results of experimental tests of the influence of passive ballistic protection on aerodynamic coefficients of the model fuselage of the Sokol helicopter. The research was carried out in the Institute of Aviation low speed wind tunnel T3 of 5 m diameter on the helicopter test stand. Measurements of aerodynamic coefficients acting on the fuselage with and without passive ballistic protection were taken using six–component internal strain gauge balance placed inside the model of the fuselage for the angles of attack α = –90-90° with step 10° and for sideslip angles β = –10°, 0°, 10°. Several aerodynamics coefficients: drag (Cx), force (Cy), lift (Cz) and moment: bank (Cmx), pitch (Cmy) and yaw (Cmz) were analysed. The results of the wind tunnel tests were presented in figures as nondimensional mean values of the above aerodynamic coefficients. Different measurements of aerodynamic characteristics were made like: the influence of Reynolds number on the Cx of the helicopter fuselage with and without protection and the comparison of aerodynamic characteristics of the helicopter fuselage Cx, Cy, Cz, Cmx, Cmy, Cmz as the function of α, without stabiliser, with and without protection. Moreover, a comparison Cx, Cy, Cz, Cmx, Cmy, Cmz as the function of α, with a stabiliser, with and without protection was made and a comparison of the influence of a stabiliser and protection on the above aerodynamic characteristics for the range of useful angles of attack were analysed. A comparison of the influence of a stabiliser and protection on aerodynamic characteristics of the helicopter fuselage Cx, Cy, Cz, Cmx, Cmy, Cmz for the range of α angles of attack was also described.