As a review, we have covered two distinct problems in which aircraft, detected by radar, are not displaying on the scope.
The first problem is where radar data is simply not supplied to a neighboring facility. This is like the Frederick "Radar Service Terminated" example. The aircraft may, in fact, be detected by radar, but not displayed on the controller's scope who has responsibility for the aircraft at that time. This problem can only be remedied if the data is supplied to the facility that needs it (and only then it works if that data isn't thrown out by the program!).
The second problem is the "cone-of-silence" problem, wherein the manner of programming to fix one problem (aircraft can't be seen directly above the radar) results in yet another problem (a whole bunch of low-altitude airspace will not show aircraft targets because the radar data is thrown out).
The third problem, however, is much more sinister. It isn't nearly as distinct or easy to recognize. In fact, it will give the controller the impression that an aircraft has a malfunctioning or intermittent transponder.
Take a look at any point midway between any two radar sites that are feeding Cleveland Center. At some point, usually near the midpoint between the radar sites, the preferred coverage changes from one radar to the other. There are no if's, and's, or but's. The aircraft is either displayed by the preferred coverage of one radar, or the preferred coverage of the other...but not both.
[Back] [Forward] [To Slide Show Introduction]
© 2000 by Lusch's Midair Collision Investigations. All rights reserved.