It was in 1985, after a commuter aircraft narrowly missed having a midair collision with an aircraft that assuredly had to be detected by one of our radar sites, yet was NOT displayed on my “radar scope,” that I began to question why that could be. That is when I learned about “radar sort boxes” and the software process termed “selective rejection.” I learned from firsthand observation that an overwhelming amount of radar data is NOT utilized in the presentation of aircraft targets for the enroute air traffic controller.
That lead to my writing an Unsatisfactory Condition Report in 1988, which I entitled Selective Rejection of Low Altitude Radar Data at Air Route Traffic Control Centers: An Unsatisfactory Compromise (SelRej.pdf). The 1989 response to my UCR was “...the methods used to filter and display radar data are sound, including the selective rejection process.” I disagreed with that conclusion, and went on to author a 1991 paper entitled, Real Targets – Unreal Displays: The inadvertent Suppression of Critical Radar Data. It was later republished in the Journal of Air Traffic Control.
“Selective rejection” continued to exist well in to, at least, 2006 (link). After discovering that, I decided to give new life to a slide show I created back in February 2000. That newer slide show was based upon the slide show I created for my RTUD presentation at the Sixth International Symposium on Aviation Psychology back in 1991.
Why can’t we process all radar data, from all radars, all the time, so as to be certain that we don’t lose an aircraft from the controller’s displays? The answer I got in 1992 centered around the fact that the current processing model was based on a uniprocessor, such that “only one function is executed at any one instance.”
The disappearance of American Airlines Flight 77 from the Indy Center radar displays on 9/11 was related to the unsatisfactory compromise that I addressed throughout most of my career. View the presentation I created, entitled Radar Sort Boxes in the area of American Airlines Flight 77's Turnaround/Disappearance.
Some may think of my concerns as outdated. However, Williard C. Meilander does not believe the solution can be arrived at with the current radar data processing methods. He thinks it is a time for a paradigm shift. Learn more here (link).
Thomas G. Lusch
Nov 2, 2014
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