Narrative:

Beech 1900 was level flight at 030 heading 140 and was issued traffic for a non associated track VFR maneuvering between 025 and 035. Beech 1900 reported no traffic observed and was issued a turn to heading 120 for traffic. Beech 1900 then reported traffic in sight and was instructed to maintain visual separation from the VFR traffic and a turn when able to heading 140. Beech 1900 read back instructions. Baron 58 was level at 040 on a converging heading with beech 1900. The controller was unable to exchange converging traffic information due to beech 1900 reporting that previously issued VFR traffic had turned 'into him' and he was climbing to avoid. The controller informed beech 1900 unable a climb due to converging traffic at 040 and advised beech 1900 to turn left/right or descend immediately. Beech 1900 reported unable as climb had already been initiated and was level at 033. Traffic was issued to baron 58 about converging B1900 traffic but no read back was given. Beech 1900 then reported descending to 030 and VFR traffic no factor. The controller reissued traffic to both beech 1900 and baron 58 for converging headings. Approximately 5 minutes later the VFR target was observed tracking northeast and climbing; when the aircraft called and requested practice approaches and identified himself. While the actions of the VFR aircraft could not be anticipated; and beech 1900 was responsible for visual separation; the controller is of the opinion that the 'fusion' system makes it very difficult to observe direction of flight and turning trends of aircraft due to the constant updating of target display.

Related reports:

Google
 

Original NASA ASRS Text

Title: TRACON Controller described a loss of separation event listing the 'FUSED' RADAR system as a causal factor.

Narrative: Beech 1900 was level flight at 030 heading 140 and was issued traffic for a non associated track VFR maneuvering between 025 and 035. Beech 1900 reported no traffic observed and was issued a turn to heading 120 for traffic. Beech 1900 then reported traffic in sight and was instructed to maintain visual separation from the VFR traffic and a turn when able to heading 140. Beech 1900 read back instructions. Baron 58 was level at 040 on a converging heading with Beech 1900. The Controller was unable to exchange converging traffic information due to Beech 1900 reporting that previously issued VFR traffic had turned 'into him' and he was climbing to avoid. The Controller informed Beech 1900 unable a climb due to converging traffic at 040 and advised Beech 1900 to turn left/right or descend immediately. Beech 1900 reported unable as climb had already been initiated and was level at 033. Traffic was issued to Baron 58 about converging B1900 traffic but no read back was given. Beech 1900 then reported descending to 030 and VFR traffic no factor. The Controller reissued traffic to both Beech 1900 and Baron 58 for converging headings. Approximately 5 minutes later the VFR target was observed tracking northeast and climbing; when the aircraft called and requested practice approaches and identified himself. While the actions of the VFR aircraft could not be anticipated; and Beech 1900 was responsible for visual separation; the Controller is of the opinion that the 'FUSION' system makes it very difficult to observe direction of flight and turning trends of aircraft due to the constant updating of target display.

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.