Narrative:

At ord we have 2 radar system, an ASR-9 and an ASR-7. The ASR-7 is a temporary backup until another ASR-9 can be installed. Tracking problems have been documented to the east of ord when we are using runways 27L/right. The problem is when 2 aircraft get side by side, the targets jump and an accurate position of the aircraft is hard to come by. The FAA solution was to revert to the ASR-7 when runway 27L/right were in use and the WX was IFR. Today we had numerous incidents where targets disappeared or jumped to each other when they were side by side on runways 27L/right. When the WX is IFR and we are forced to use the runway 27's, our arrival rate is reduced almost 20 percent. Now the safety factor. When it is IFR and parallel approachs are being used, monitors are needed to assure aircraft don't violate the no transgression zone between the runways. With these targets jumping around, an actual position is hard to pin down. Callback conversation with reporter revealed the following information: reporter states that this is an intermittent problem. It occurs northeast of the airport and also to some degree, to the south. It only occurs with the ASR-7 radar system. Reporter does not know if a ucr has been filed or not. Problem has been ongoing for some time. The plan is to replace their radar system with ASR-9's whenever all the problems are worked out. Reporter also states that the ASR-9 radar is improving. They recently did some software work that has improved the presentation.

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Original NASA ASRS Text

Title: ASR-7 RADAR SYS HAS TRACKING PROBS WHEN USING RWY 27L AND RWY 27R.

Narrative: AT ORD WE HAVE 2 RADAR SYS, AN ASR-9 AND AN ASR-7. THE ASR-7 IS A TEMPORARY BACKUP UNTIL ANOTHER ASR-9 CAN BE INSTALLED. TRACKING PROBS HAVE BEEN DOCUMENTED TO THE E OF ORD WHEN WE ARE USING RWYS 27L/R. THE PROB IS WHEN 2 ACFT GET SIDE BY SIDE, THE TARGETS JUMP AND AN ACCURATE POS OF THE ACFT IS HARD TO COME BY. THE FAA SOLUTION WAS TO REVERT TO THE ASR-7 WHEN RWY 27L/R WERE IN USE AND THE WX WAS IFR. TODAY WE HAD NUMEROUS INCIDENTS WHERE TARGETS DISAPPEARED OR JUMPED TO EACH OTHER WHEN THEY WERE SIDE BY SIDE ON RWYS 27L/R. WHEN THE WX IS IFR AND WE ARE FORCED TO USE THE RWY 27'S, OUR ARR RATE IS REDUCED ALMOST 20 PERCENT. NOW THE SAFETY FACTOR. WHEN IT IS IFR AND PARALLEL APCHS ARE BEING USED, MONITORS ARE NEEDED TO ASSURE ACFT DON'T VIOLATE THE NO TRANSGRESSION ZONE BTWN THE RWYS. WITH THESE TARGETS JUMPING AROUND, AN ACTUAL POS IS HARD TO PIN DOWN. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THAT THIS IS AN INTERMITTENT PROB. IT OCCURS NE OF THE ARPT AND ALSO TO SOME DEG, TO THE S. IT ONLY OCCURS WITH THE ASR-7 RADAR SYS. RPTR DOES NOT KNOW IF A UCR HAS BEEN FILED OR NOT. PROB HAS BEEN ONGOING FOR SOME TIME. THE PLAN IS TO REPLACE THEIR RADAR SYS WITH ASR-9'S WHENEVER ALL THE PROBS ARE WORKED OUT. RPTR ALSO STATES THAT THE ASR-9 RADAR IS IMPROVING. THEY RECENTLY DID SOME SOFTWARE WORK THAT HAS IMPROVED THE PRESENTATION.

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.