Regional Jet CL65; Undifferentiated or Other Model
Air Traffic Control Developmental
Situational Awareness
ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
ATC Equipment / Nav Facility / Buildings
I was working the west final position and sequencing base traffic with downwind traffic for Runway 36L. My Air Carrier X was southbound on a left downwind level at 5;000 FT. Air Carrier Y was converging with Air Carrier X eastbound on a left base descending to 6;000 FT. I assigned Air Carrier X an eastbound heading to sequence them in front of Air Carrier Y. It appeared that the Air Carrier X had initiated a turn; partly due to the new 'fused' presentation on the RADAR scope. I have noticed that in fused mode that some targets jump around or even back up. This could lead to a false sense of aircraft movement. Feeling I had adequate spacing; I descended the Air Carrier Y to 5;000 FT to parallel Air Carrier X's course. It appeared that the Air Carrier X was not turning as initially thought and I assigned the aircraft a further turn of 060 or 070 degrees to ensure divergence. I don't know for sure if altitude separation was lost or not prior to divergence. I received no traffic alerts. I feel that the fused mode of RADAR is not able to compute aircraft position as fast as the RADAR is updating. This gives estimated; not actual positions on your display which could cause you to make control decisions on false information.
CLT Controller voiced concern regarding the 'fused' RADAR presentation; noting aircraft position updating is different from previous presentations; making turns more difficult to identify.