Sir - I was interested to read the letter from A H Thomas on the global-positioning system (Flight International, 8-14 January, P37). About 20 years ago, I worked on the UK commutated Doppler system and patented a Doppler microwave-landing system (MLS) in 1981.
This Doppler MLS provides an aircraft with information on azimuth, elevation and range by the measurement of Doppler frequencies only
Perhaps the UK Civil Aviation Authority should consider developing the Doppler MLS again and put it into use by 2010, when the instrument-landing system is to be phased out.
Dr F R CONNOR
London, UK
Source: Flight International
