Clt controller voiced concern regarding the 'fused' radar presentation; noting aircraft position upd...

Narrative:

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.

Original NASA ASRS Text

Title: CLT Controller voiced concern regarding the 'fused' RADAR presentation; noting aircraft position updating is different from previous presentations; making turns more difficult to identify.

Narrative: 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.

Data retrieved from NASA's ASRS site as of July 2013 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.

Attributes
ACN	1053284
Time
Date	201212
Local Time Of Day	1201-1800
Place
Locale Reference	CLT.Tower
State Reference	NC
Aircraft 1
Make Model Name	Regional Jet CL65 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Route In Use	Vectors
Flight Plan	IFR
Aircraft 2
Make Model Name	Airbus Industrie Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	Departure Approach
Qualification	Air Traffic Control Developmental
Events
Anomaly	ATC Issue All Types Deviation - Procedural Published Material / Policy

Clt controller voiced concern regarding the 'fused' radar presentation; noting aircraft position updating is different from previous presentations; making turns more difficult to identify.