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The NAS has a LOT of radars…

As might be expected, it takes a lot of radars to provide the coverage necessary to track aircraft. Even though not all aircraft are tracked, densely populated regions of the country in which there are significant and frequent aircraft operations must be thoroughly covered. In addition, there are two basic types of surveillance radar: terminal (short-range, 20 miles or so) and enroute (higher altitudes and longer ranges than terminal). The NAS currently operates approximately 400 surveillance radars at an operational, yearly cost of  (??? to be supplied). This does not include the total cost of procurement, testing, and installation. Military also operates surveillance radar systems that are interfaced to the NAS and help support the tracking of civilian aircraft. U.S. military surveillance systems provide approximately 25% of the surveillance services to the NAS.

 Radar Modernization:

The surveillance radar system in the NAS is undergoing modernization to add digital capability. The basic foundation of the surveillance technology is still analog, dating back to a time prior to the advent of satellite based navigation systems, such as Global Positioning System (GPS). Even with the modernization of the surveillance radar system, aircraft will continue to rely on the use of its (old technology) transponder. A systems engineering analysis of this modernization effort might lead to the conclusion that it is a lot of effort to modernize a very old and basic technology. Its true that the current system does work adequately, but as more and more aircraft are flying in more and more congested airspace, one could consider whether another approach should be considered. Sometimes overhauling old systems do not yield future results that are satisfactory.

What if…..

Suppose there is a way to provide the same tracking function to the ATC system without using surveillance radar. If the basic requirement of the ATC system is to positively know the location, altitude and speed of aircraft, then combining several readily available technologies can meet this requirement without using surveillance radar. And suppose it could be done more reliably and more accurately. That would be a good thing. But suppose it could be done cheaper and more economically both for the aircraft operators and the operators of the ground ATC system. That would be a very good thing. Suppose many, many more aircraft could be covered than today. ATC services could potentially be provided to thousands of geographic areas and communities not presently receiving that benefit. Think of the potential economic expansion that rural communities could experience. Medical services could be flown in more reliably in all weather. That would be a very, very good thing.

 More than a dot on the horizon

One way to view the current method of tracking and separating aircraft is to consider it in the same manner as the computer networks many of us use at work and at home are viewed. Computers are assigned a unique IP address. Aircraft are assigned unique 4-digit transponder codes. Computers can join larger networks in either a public or a private session. Aircraft are joined to a large computer network in a private session, called the NAS. Through the use of IP, computers can communicate with other computers even though many miles separate them. Aircraft could become more than a dot on the horizon as we watch them fly over the countryside. They could actually become a node on an infinitely useful network of information and application programs. All that is needed is to ensure they remain connected to the network.


If aircraft utilized IP as network computers do, functions in the cockpit could be enabled not currently being provided. It could open up a whole new set of operating capabilities, safety and efficiency for tomorrow’s aviation industry.  The functions provided today that require the use of multiple on-board systems could be reduced to two simple systems.

 First, a rigorous and dependable method to maintain the airplane’s connection to the ground based IP network is needed. This function is feasible using a combination of VHF radio (as is used for today’s aircraft communications) and an alternate, backup communication method. For aircraft that fly in sparsely populated areas that are beyond VHF coverage of the existing NAS infrastructure, or for any aircraft that might lose VHF coverage (even temporarily), a satellite communication system could be employed. Satellite communication is currently being used for trans-oceanic flight today in which aircraft are clearly beyond range of the VHF radio system in the NAS.

 Second, a means of accurately determining an aircraft’s position is required. Current technology in GPS receivers provides position information reliably and accurately. WAAS and LAAS are aviation systems that utilize GPS and provide error correction to allow aircraft the accuracy needed for navigation and landing.

 By combining the GPS provided position information of any moving aircraft (or other vehicle) with reliable mobile network connectivity, the aircraft’s position could be constantly reported to the ground network for processing. Further, this data could be intelligently parsed to provide position and tracking information back to aircraft so its flight crew could be aware of other aircraft movement in its proximity.   NEXT

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