Sir - I have drawn attention previously in your letters page to the susceptibility of the global-positioning system (GPS) to jamming and other outages, which threaten the approach and landing phase of aircraft.
Since no denial has been made from authorities such as the US GPS Joint Program Office, for example, I assume that these fears are well founded.
It must be time for civil and military aviation authorities outside the USA to declare that the system will never be a stand-alone landing aid.
Discussions at the October Flight International Landing and Approach Systems 94 conference, in Geneva, did not appear to reach a clear conclusion.
The argument must be settled and a combined microwave-landing system/GPS developed to satisfy all operational, accuracy and safety requirements.
A H THOMAS
Epsom, Surrey, UK
Source: Flight International