This was a letter I wrote concerning how the process of selective rejection, which eliminates perfectly good radar returns from some low-altitude aircraft, can affect the service we are called upon to provide during aircraft emergencies.
Date: February 15, 1992
From: Thomas G. Lusch, ATCS Team 55
To: Thomas B. Howell, Air Traffic Manager, Cleveland ARTCC
thru: Richard Barnett, Area Supervisor Team 55,
and
David R. Brizendine, Area 5 Manager
Ref: The inadvertent suppression of low-altitude radar data.
Dear Tom,
On February 4, 1992, I observed a situation at our Clarion sector which added extra emphasis to our need for processing all the available radar data on low-altitude aircraft. In this particular incident, the pilot of N7433R had a dangerous encounter with icing conditions shortly after takeoff from the Clarion County airport. To make matters worse, this pilot also had a gyro failure. The pilot was sorely in need of navigation assistance and promptly declared an emergency.
The supervisor-in-charge took immediate action to assist the controller in this high workload situation. He promptly combined the Clarion sector with the Tyrone sector. This allowed the controller to devote his full attention to this life-threatening predicament this pilot managed to get himself into. In the ensuing period, the controller did the absolute best he could under the circumstances. Unfortunately, the best he could do was to merely talk to the pilot, as the aircraft was only intermittently displayed on his radar scope.
To make a long story short, after floundering around for approximately 10-15 minutes below the minimum safe altitude, the pilot managed to find his own way back to Clarion Co. airport. The controller could NOT provide navigational assistance. This aircraft was NOT DISPLAYED on our scopes at this low altitude when it was just south of Clarion VOR. I feel 100% confident that this aircraft was, however, continuously detected by our excellent Clearfield radar site during this entire ordeal. The reason this aircraft was not displayed, of course, is due to the manner in which radar data is processed by the NAS program.
Since you have just recently came on-board here at Cleveland Center, you may not be aware that back in September of 1988 I wrote an Unsatisfactory Condition Report (UCR #330069). It addressed this very concern. No action was taken at that time.
As you recall, however, last April I again addressed this subject. I wrote a paper and gave a presentation. The presentation took place at the Sixth International Symposium on Aviation Psychology. On August 28, 1991, you allowed me to give a presentation on this very subject to yourself and five other representatives from Air Traffic, Airway Facilities, and NATCA.
Unfortunately, as this recent emergency situation in the Clarion sector so aptly demonstrated, the suppression of low-altitude radar data remains. Emergency navigation assistance to a low-altitude aircraft that is detected, but NOT displayed, makes it so the controller is incapable of aiding a pilot. Likewise, valuable radar data that could be utilized for a search and rescue mission is also lost. And as I have clearly documented, there still exists a likelihood that a controller will not be able to issue a timely traffic advisory or critical SAFETY ALERT on an aircraft that is detected by our radars, yet NOT displayed.
Tom, literally hundreds of millions of dollars have been spent by us on the installation and around-the-clock maintenance of top quality radars across our country. Likewise, the aviation community has spent millions of dollars to equip their aircraft with transponders to enhance their radar image. I feel that it is truly a shame that we suppress some of this very valuable radar data when it can be so critical to our mission in the FAA.
Often we feel that new equipment will solve our problems. The Initial Sector Suite System (ISSS), that will be arriving here within the next two to three years, should be a great improvement in the tools we utilize to accomplish our mission. Unfortunately, this phase of the Advanced Automation System (AAS) does NOT address the processing of radar data. We will still be left with these areas where low-altitude radar coverage exists, yet traffic won't be displayed.
I truly believe that we could vastly improve the display of low-altitude aircraft in the ARTCC environment at a minimal cost. I believe that we could do this within the framework of our existing hardware and software. I also firmly believe that Cleveland Center could, and for that matter, should lead an effort at addressing this compromise in our radar data processing methods. With your leadership, Cleveland Center could be at the forefront of pursuing and correcting this quality control issue that affects all 20 domestic Air Route Traffic Control Centers.
I believe the time for us to act is now. I urge you to make this a top priority on your agenda.
Thank you for your time.
Sincerely,
Thomas G. Lusch
P.S. I do not wish for you to be caught off guard. I want to advise you that Mr. Tirey Vickers, Editor of The Journal of Air Traffic Control, personally telephoned me. He had read my paper "Real Targets - Unreal Displays: The Inadvertent Suppression of Critical Radar Data," which was published in the Proceedings of the Symposium last April. He requested permission to reprint it. I am very honored that the Air Traffic Control Association (ATCA) feels that the subject is worthy of discussion. The reprint will appear in this year's first issue of the Journal. It should be out within the next two weeks.
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