Narrative:

ZFW center, long-range radar, texarkana, keller, alexandria long-range radar sites. Despite numerous controller operational surveys, technician involvement, unsatisfactory condition reports, etc, we are still plagued with unreliable radar data. This problem affects 7 or more en route control sectors in the form of target jump, target loss, beacon swaps, unreliable altitude and ground speed readout. The problem is noticed in certain geographical position, apparently due to radar sort box alignment for the preferred and alternate radar ('mosaiced') site. On apr/sun/93, I was working paxto-hi with heavy traffic. I evaluated a houston departure climbing over lufkin northbound with a dfw arrival wbound on J58. Using vector length, I projected the departure to pass behind the J58 traffic and issued a climb clearance. The area about 20-40 mi north of lfk has unreliable radar data. I always take this into account and use 5 or more extra mi separation, as I did in this case. Nevertheless, a couple of mins later, I was turning my northbound aircraft 50 degrees right to salvage 5.0 mi minimum separation. This radar is so bad at times, at certain locations, that you literally don't know where an aircraft is. I've seen ground speed fluctuations of 200-300 KTS, beacons swapping and going 180 degrees opposite direction, etc. I've corrected a radar vector using vector length readout only to grossly worsen the heading because I was using faulty information. Sometimes you just situation at the display and wait for a min or 2 until the beacon is away from one of these problem areas before you can really know what is happening. Lots of action on this problem, but no results. Given the extreme traffic density in the subject airspace, not good. Callback conversation with reporter revealed the following: reporter states that radar problems has been on going for over 2 yrs. Ucr's have been filed in the past, but the last one closed recently. The problem still exists even though maintenance changed or swapped some of the sort boxes. This involves both high and low radar sectors. Some of the sectors involved are: paxto hi, gregg county hi, monrow low, and donie low. Some of the sectors have high density traffic with numerous crossing points. An error occurred recently allegedly due to track jump. Facility classified error as operational.

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Original NASA ASRS Text

Title: CTLR CLAIMS THAT 3 RADAR SITES HAVE BAD RADAR COVERAGE IN CERTAIN AREAS.

Narrative: ZFW CTR, LONG-RANGE RADAR, TEXARKANA, KELLER, ALEXANDRIA LONG-RANGE RADAR SITES. DESPITE NUMEROUS CTLR OPERATIONAL SURVEYS, TECHNICIAN INVOLVEMENT, UNSATISFACTORY CONDITION RPTS, ETC, WE ARE STILL PLAGUED WITH UNRELIABLE RADAR DATA. THIS PROB AFFECTS 7 OR MORE ENRTE CTL SECTORS IN THE FORM OF TARGET JUMP, TARGET LOSS, BEACON SWAPS, UNRELIABLE ALT AND GND SPD READOUT. THE PROB IS NOTICED IN CERTAIN GEOGRAPHICAL POS, APPARENTLY DUE TO RADAR SORT BOX ALIGNMENT FOR THE PREFERRED AND ALTERNATE RADAR ('MOSAICED') SITE. ON APR/SUN/93, I WAS WORKING PAXTO-HI WITH HVY TFC. I EVALUATED A HOUSTON DEP CLBING OVER LUFKIN NBOUND WITH A DFW ARR WBOUND ON J58. USING VECTOR LENGTH, I PROJECTED THE DEP TO PASS BEHIND THE J58 TFC AND ISSUED A CLB CLRNC. THE AREA ABOUT 20-40 MI N OF LFK HAS UNRELIABLE RADAR DATA. I ALWAYS TAKE THIS INTO ACCOUNT AND USE 5 OR MORE EXTRA MI SEPARATION, AS I DID IN THIS CASE. NEVERTHELESS, A COUPLE OF MINS LATER, I WAS TURNING MY NBOUND ACFT 50 DEGS R TO SALVAGE 5.0 MI MINIMUM SEPARATION. THIS RADAR IS SO BAD AT TIMES, AT CERTAIN LOCATIONS, THAT YOU LITERALLY DON'T KNOW WHERE AN ACFT IS. I'VE SEEN GND SPD FLUCTUATIONS OF 200-300 KTS, BEACONS SWAPPING AND GOING 180 DEGS OPPOSITE DIRECTION, ETC. I'VE CORRECTED A RADAR VECTOR USING VECTOR LENGTH READOUT ONLY TO GROSSLY WORSEN THE HDG BECAUSE I WAS USING FAULTY INFO. SOMETIMES YOU JUST SIT AT THE DISPLAY AND WAIT FOR A MIN OR 2 UNTIL THE BEACON IS AWAY FROM ONE OF THESE PROB AREAS BEFORE YOU CAN REALLY KNOW WHAT IS HAPPENING. LOTS OF ACTION ON THIS PROB, BUT NO RESULTS. GIVEN THE EXTREME TFC DENSITY IN THE SUBJECT AIRSPACE, NOT GOOD. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: RPTR STATES THAT RADAR PROBS HAS BEEN ON GOING FOR OVER 2 YRS. UCR'S HAVE BEEN FILED IN THE PAST, BUT THE LAST ONE CLOSED RECENTLY. THE PROB STILL EXISTS EVEN THOUGH MAINT CHANGED OR SWAPPED SOME OF THE SORT BOXES. THIS INVOLVES BOTH HIGH AND LOW RADAR SECTORS. SOME OF THE SECTORS INVOLVED ARE: PAXTO HI, GREGG COUNTY HI, MONROW LOW, AND DONIE LOW. SOME OF THE SECTORS HAVE HIGH DENSITY TFC WITH NUMEROUS XING POINTS. AN ERROR OCCURRED RECENTLY ALLEGEDLY DUE TO TRACK JUMP. FACILITY CLASSIFIED ERROR AS OPERATIONAL.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.