The method described provides glide-paths for climbing and descending aircraft by combining in a single instrument information from the barometric altimeter and radar distance measuring equipment. Preliminary flight tests have shown that the method provides a smooth path along which an aircraft can be flown within close limits, and is one that appears sufficiently promising to justify further development.

Height separation has for years been a fundamental concept in the control of air traffic. It is the basic method of preventing collision during en-route navigation and in some holding procedures. The main reason for this is that a suitable instrument already exists in the form of the barometric altimeter, aninstrument which is intrinsically more accurate and reliable than any of the usual navigational aids.