Contents
- Free Flight
- All-Weather Landing Systems
- Airport Surveillance
Free Flight
The Free Flight concept is intended to ease the burden on the current aircraft management system while improving flight safety. In this concept, alert and protected zones are defined around each aircraft, dependent on the size and speed of the aircraft. Aircraft are free to pick routes as they choose, as long as their protected zones do not impinge on the protected zones of other aircraft. Pilots are expected to take evasive action when their alert zone enters the alert zone of another aircraft.The existing method for providing air traffic controllers with aircraft locations is for ground-based radars to "paint" the aircraft. A special radio receiver on the aircraft, called a "transponder" notes that the aircraft is being interrogated and transmits coded information to the special antenna mounted atop the radar antenna. This signal includes flight identification and radar altimeter data. All this information is processed by computers and displayed to air traffic controllers.
This system doesn't work on long overwater flights because the radars used for air traffic control don't have sufficient range. The free flight concept allows for this by providing a satellite data link between the controllers and the airplane. This permits nearly constant monitoring of aircraft status.
All-Weather Landing Systems
Electronic landing systems are used to keep airplanes landing in all kinds of weather. Previous systems using radio-beams carefully shaped by using specific antenna configurations are costly and difficult to maintain. GPS permits a much cheaper and easier means of providing very precise landing capabilities.Airport Surveillance
Aircraft may be graceful in the air, but on the ground they are large, clumsy automobiles. Aircraft are directed on the ground by controllers; however, when the controllers are busy, or lose direct line of sight with an aircraft, disasters can happen. One of the worst air accidents in history occured when two 747s collided on the ground. By placing GPS beacons on all aircraft and displaying the locations of the aircraft in the control tower on a display, accidents like this can be avoided.