Abstract: Static pressure sensing and free airstream temperature sensing is obviated in a method for determining aircraft velocity relative to an airmass by utilizing a static pressure and temperature component present in pressure variations sensed by a total pressure sensor located on a rotating arm mounted on the fuselage of an aircraft. A harmonic analysis of a quasi-sinusoidal total pressure variation includes a determination of steady state and both first and second harmonic components. These harmonic components are used to determine the static pressure, the free airstream temperature and the aircraft airspeed without separately sensing these parameters.

Abstract: Aircraft speed and direction are determined by sampling the sinusoid-like pressure variations at the end of a rotor and performing a Fourier analysis on the pressure samples. Fourier quadrature component signals are used to determine aircraft direction and are also used to determine, along with a steady state component, the aircraft's total velocity. A discrete Fourier analysis may be performed on the pressure samples using a plurality of subrevolution pressure samples averaged over each subrevolution interval.