PURPOSE: To identify the mach number by measuring the angle of a shock wave caused a cone or a gib, and deflection angle of air current determining the asymmetry of a waveform

CONSTITUTION: A rod-like mechanism 3 having a cone 1 and a pressure hole 2 is provided at the fuselage edge of an aircraft or a missile. The mechanism 3 is a slender and small form, in which the turbulence for outside air current is small and piping of the pressure hole 2 to a pressure convertor is communicated. A total pressure distribution is measured from the pressure hole of the mechanism 3 and an angle 5 of a shock wave 4 is found due to the lowering of total pressure. In other words, pressure is suddenly changed at a certain place and indicates a step-like change. A place Y1 changing in the step-like form from a measurement value is found and a shock wave angle θ is obtained from the expression tanθ=(Y1-Y2)/L. The mach number M of air current is identified from the relation of the angle 5 and the mach number of the shock wave 4. In addition, an inclination angle 8 is simultaneously identified from a difference between the upside angle 6 and the lower side angle 7 of the shock wave 4.