Sir - US President Bill Clinton has stated that the USA is committed to provide global-positioning-system (GPS) signals to the international civil-aviation community (Flight International, 5-11 April, P9). While one does not doubt his sincerity, he cannot commit his successors.
Unless controlled and financed by an international organisation such as Inmarsat or the International Civil Aviation Organisation, the GPS cannot be adopted as a sole means of navigation or landing guidance. Even then, the threat of accidental or malicious jamming means that another source of positional information must be available. For en route navigation, this may be an inertial system or a radio aid. For landing guidance, the microwave-landing system, preferably in an improved and cheaper form, is appropriate.
A H THOMAS
Epsom, Surrey, UK
Source: Flight International
