Narrative:

Location: ZDV, longmont, co. Sector 18 radar (positive control area, FL240 and up). Time: daily, chronic occurrence for the last several months. Events: a) sudden changes in ground speed displays of tracked aircraft from 40 to 200 plus KTS, occurring at random and disrupting actual speeds for several mins. B) appearance of false transponder targets that are 'ghosts' of other tracked aircraft that are up to hundreds of mi away, lasting for 30 seconds to over 5 mins. Consequences: a) if aircraft tracks were continuously watched, an instantaneous change in speed would be noticed and recognized as an error. Normally however, tracks are scanned, one after another in rapid succession, and control decisions made based on information displayed at the moment. If that information is wrong, then an apparently slower aircraft may be turned behind an apparently faster one when in fact the speed difference is opposite of what is displayed, resulting in the faster aircraft being turned to a near collision course with the slower one. These decisions are usually made at least 3-4 mins prior to loss of separation, allowing time to 'save' the situation. This exact scenario has happened once to myself, I have observed it happen to 2 others, and similar problems have been experienced by nearly all 47 radar controllers that work sector 18. B) untracked targets require valuable time and attention to identify. Due to the frequency of false target appearances (multiple times daily), these targets have come to be expected and ignored. The possibility of a real untracked aircraft being ignored is therefore higher. Possible causes: we have a new 'host' computer designed for new 'sector suite' radar consoles to come in a few yrs. Some have observed that the appearance of this problem (speed jumps) seems to have been concurrent with the installation of host. However, the host system is the strongest link in a chain of data transfers beginning with the radar sites and ending after host with display generators. We have experienced several unexpected shutdowns since host because of failures of peripheral components, most of which are very old and parts are scarce. Much time has been spent trying to change radar pulse repetition frequencys and looking for a software glitch when data from 2 sites are blended, all to no avail. The garden city, ks, radar site seems to be the source of the speed jump problem. The false targets are related to the north platte, northeast, site. I fear that the automation improvements inside the control ctrs are being made at the expense of the deteriorating infrastructures outside, and our control system will be only as safe as the weakest link in the chain. Whatever the cause, these steadily worsening problems need to be addressed from some new perspectives and solved before we have a near miss or a collision with an unidented aircraft that was dismissed as a false target. Callback conversation with reporter revealed the following information. The reporter stated the false target problem has been ongoing since installation of the host computer. This problem has been idented to air traffic management who have turned the problem over to af. Reporter stated in the beginning the target would stay on the scope for several seconds then disappear. Targets now stay on the scope for several mins. Sector 18 has a blend of 3 radar sites: north platte, northeast; rockville, ks; and garden city, ks. The false target problem has not been ucr'd. Target speed jump problem became acute in 11/91 and was idented to at management. Reporter was told that the garden city sort boxes were changed and the reporter said the problem improved but would deteriorate in a week to 2 weeks. Ucr was filed on speed jump problem in 2/92. Ucr problem was turned over to af. The ppo has told the reporter the sort boxes have been changed again since the ucr was filed. Speed jump problem has improved but the reporter said he expects the problem back in several weeks. Reporter called back and stated when he returned to work he asked other sectors if they were having the same problem and the answer was yes although they were not documenting.

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Original NASA ASRS Text

Title: ATC EQUIP PROBLEM RADAR FALSE TARGETS AND SPD DISPLAY CHANGES. UCR FILED ON SPD PROBLEM.

Narrative: LOCATION: ZDV, LONGMONT, CO. SECTOR 18 RADAR (PCA, FL240 AND UP). TIME: DAILY, CHRONIC OCCURRENCE FOR THE LAST SEVERAL MONTHS. EVENTS: A) SUDDEN CHANGES IN GND SPD DISPLAYS OF TRACKED ACFT FROM 40 TO 200 PLUS KTS, OCCURRING AT RANDOM AND DISRUPTING ACTUAL SPDS FOR SEVERAL MINS. B) APPEARANCE OF FALSE TRANSPONDER TARGETS THAT ARE 'GHOSTS' OF OTHER TRACKED ACFT THAT ARE UP TO HUNDREDS OF MI AWAY, LASTING FOR 30 SECONDS TO OVER 5 MINS. CONSEQUENCES: A) IF ACFT TRACKS WERE CONTINUOUSLY WATCHED, AN INSTANTANEOUS CHANGE IN SPD WOULD BE NOTICED AND RECOGNIZED AS AN ERROR. NORMALLY HOWEVER, TRACKS ARE SCANNED, ONE AFTER ANOTHER IN RAPID SUCCESSION, AND CTL DECISIONS MADE BASED ON INFO DISPLAYED AT THE MOMENT. IF THAT INFO IS WRONG, THEN AN APPARENTLY SLOWER ACFT MAY BE TURNED BEHIND AN APPARENTLY FASTER ONE WHEN IN FACT THE SPD DIFFERENCE IS OPPOSITE OF WHAT IS DISPLAYED, RESULTING IN THE FASTER ACFT BEING TURNED TO A NEAR COLLISION COURSE WITH THE SLOWER ONE. THESE DECISIONS ARE USUALLY MADE AT LEAST 3-4 MINS PRIOR TO LOSS OF SEPARATION, ALLOWING TIME TO 'SAVE' THE SITUATION. THIS EXACT SCENARIO HAS HAPPENED ONCE TO MYSELF, I HAVE OBSERVED IT HAPPEN TO 2 OTHERS, AND SIMILAR PROBLEMS HAVE BEEN EXPERIENCED BY NEARLY ALL 47 RADAR CTLRS THAT WORK SECTOR 18. B) UNTRACKED TARGETS REQUIRE VALUABLE TIME AND ATTN TO IDENT. DUE TO THE FREQ OF FALSE TARGET APPEARANCES (MULTIPLE TIMES DAILY), THESE TARGETS HAVE COME TO BE EXPECTED AND IGNORED. THE POSSIBILITY OF A REAL UNTRACKED ACFT BEING IGNORED IS THEREFORE HIGHER. POSSIBLE CAUSES: WE HAVE A NEW 'HOST' COMPUTER DESIGNED FOR NEW 'SECTOR SUITE' RADAR CONSOLES TO COME IN A FEW YRS. SOME HAVE OBSERVED THAT THE APPEARANCE OF THIS PROBLEM (SPD JUMPS) SEEMS TO HAVE BEEN CONCURRENT WITH THE INSTALLATION OF HOST. HOWEVER, THE HOST SYS IS THE STRONGEST LINK IN A CHAIN OF DATA TRANSFERS BEGINNING WITH THE RADAR SITES AND ENDING AFTER HOST WITH DISPLAY GENERATORS. WE HAVE EXPERIENCED SEVERAL UNEXPECTED SHUTDOWNS SINCE HOST BECAUSE OF FAILURES OF PERIPHERAL COMPONENTS, MOST OF WHICH ARE VERY OLD AND PARTS ARE SCARCE. MUCH TIME HAS BEEN SPENT TRYING TO CHANGE RADAR PULSE REPETITION FREQS AND LOOKING FOR A SOFTWARE GLITCH WHEN DATA FROM 2 SITES ARE BLENDED, ALL TO NO AVAIL. THE GARDEN CITY, KS, RADAR SITE SEEMS TO BE THE SOURCE OF THE SPD JUMP PROBLEM. THE FALSE TARGETS ARE RELATED TO THE N PLATTE, NE, SITE. I FEAR THAT THE AUTOMATION IMPROVEMENTS INSIDE THE CTL CTRS ARE BEING MADE AT THE EXPENSE OF THE DETERIORATING INFRASTRUCTURES OUTSIDE, AND OUR CTL SYS WILL BE ONLY AS SAFE AS THE WEAKEST LINK IN THE CHAIN. WHATEVER THE CAUSE, THESE STEADILY WORSENING PROBLEMS NEED TO BE ADDRESSED FROM SOME NEW PERSPECTIVES AND SOLVED BEFORE WE HAVE A NEAR MISS OR A COLLISION WITH AN UNIDENTED ACFT THAT WAS DISMISSED AS A FALSE TARGET. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO. THE RPTR STATED THE FALSE TARGET PROBLEM HAS BEEN ONGOING SINCE INSTALLATION OF THE HOST COMPUTER. THIS PROBLEM HAS BEEN IDENTED TO AIR TFC MGMNT WHO HAVE TURNED THE PROBLEM OVER TO AF. RPTR STATED IN THE BEGINNING THE TARGET WOULD STAY ON THE SCOPE FOR SEVERAL SECONDS THEN DISAPPEAR. TARGETS NOW STAY ON THE SCOPE FOR SEVERAL MINS. SECTOR 18 HAS A BLEND OF 3 RADAR SITES: N PLATTE, NE; ROCKVILLE, KS; AND GARDEN CITY, KS. THE FALSE TARGET PROBLEM HAS NOT BEEN UCR'D. TARGET SPD JUMP PROBLEM BECAME ACUTE IN 11/91 AND WAS IDENTED TO AT MGMNT. RPTR WAS TOLD THAT THE GARDEN CITY SORT BOXES WERE CHANGED AND THE RPTR SAID THE PROBLEM IMPROVED BUT WOULD DETERIORATE IN A WK TO 2 WKS. UCR WAS FILED ON SPD JUMP PROBLEM IN 2/92. UCR PROBLEM WAS TURNED OVER TO AF. THE PPO HAS TOLD THE RPTR THE SORT BOXES HAVE BEEN CHANGED AGAIN SINCE THE UCR WAS FILED. SPD JUMP PROBLEM HAS IMPROVED BUT THE RPTR SAID HE EXPECTS THE PROBLEM BACK IN SEVERAL WKS. RPTR CALLED BACK AND STATED WHEN HE RETURNED TO WORK HE ASKED OTHER SECTORS IF THEY WERE HAVING THE SAME PROBLEM AND THE ANSWER WAS YES ALTHOUGH THEY WERE NOT DOCUMENTING.

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.