METHOD OF ESTIMATING THE DANGEROUS RANGE OF TRANSONIC NUMBERS M OF THE FLIGHT OF SUPERSONIC AIRCRAFT AND AEROSPACE SYSTEMS

Abstract

Ensuring flight safety of supersonic aircraft and aerospace systems in the transonic range of flight M numbers still remains an ac- tual scientific and applied problem. This is due to the occurrence of various dangerous aeroelasticity phenomena in these flight modes. Such phenomena include transonic flutter, the occurrence of which has repeatedly resulted in the destruction of aircraft structural elements and, first of all, of aerodynamic control surface structural elements. Many publications are devoted to the theoretical and experimental research of this phenomenon, in which various approaches are proposed to substantiate the causes of intense oscillations of the aerodynamic control surfaces of modern supersonic aircraft in these flight modes, the conditions of their occurrence, the influence of various factors on the level of oscillations. It is noted that there are still no reliable theoretical methods for estimating the non-stationary forces of aerodynamic control surfaces that oscillate in a transonic flow, so the use of linear mathematical similarity models does not always allow transferring the results of blowing models in wind tunnels to full-scale aircraft designs. The paper proposes a method for estimating the dangerous range of M numbers in which transonic flutter of the aerodynamic control surfaces of supersonic aircraft and aerospace systems is possible. The method is based on the analysis of regularities of the adiabatic expansion of the local supersonic air flow on the surface of the airfoil in the range of transonic numbers M. Calculations have proven that for typical aerodynamic surfaces of modern supersonic aircraft, the occurrence of transonic flutter is possible in a narrow range of numbers M = 0.9…0.94. The obtained results can be used to substantiate the safe flight modes of supersonic aircraft both at the stage of flight tests and at the stage of operation. Further studies of this problem should be devoted to the analysis of methods for reducing the level of oscillations of aerodynamic control surfaces when transonic flutter occurs.