Description: The measuring methods of spectrum parameters of the probing signal of precision approach radar of the aircraft radar landing system is investigated in the paper. The signal is returned from the landing aircraft moving in the radar direction. The extension of functional tasks related with precision approach radar of aviation radar systems significantly influences on support of save aviation adequate level. The aircraft speed determination on the heading inbound is one of the tasks. It is proposed to determine the aircraft speed using a method based on measuring the Doppler frequency shift of probing signal with using digital spectral analysis of sended signal namely the discrete Fourier transformation according to Fast Fourier Transform algorithm. The discresity of measurement of the Doppler frequency shift of probing signal reflected from the aircraft is determined. The suggestions related with implementation of Doppler frequency measurement unit is developed. This device defines the aircraft flight speed in the landing process. The activities needed for implementation the described function in the existing modern radar landing systems of aircraft are proposes. The extension of precision approach radar function for obtaining information about aircraft landing speed will allow for flight management team to make adequate decisions on the management of aircraft landing, especially in the event of their landing after the completion of combat missions with the received damage and avionics failures.
Keywords: Doppler signal spectrum, aircraft, landing radar, landing, radial velocity, radar landing system