S46 controller expressed concern regarding the operational characteristic of 'fused' radar; noting t...

Narrative:

B737-800 was vectored to an ILS runway 16L approach and cleared for such. B737-900 was vectored in behind B737-800 with the intent to conduct a dual dependent ILS approach to runway 16R. I had established vertical separation while vectoring the B737-900 onto the final approach course. We were using 'fused' radar display which has an undesirable characteristic of 'target hopping'; an erratic flight path. I misjudged the distance and turned the aircraft in too close to successfully complete the approach. I broke him off to the southwest when I determined it would not work out. Separation was lost during the escape maneuver. Fusion radar sometimes causes a track to display as much as 1/2 mile from actual position. I have seen 'jumps' into adjacent finals followed by accurate depiction of aircraft position. I misjudged rate of turn and wind effects in this situation. [I need to] be more conservative in vectoring aircraft into position for dual-dependent ILS approaches; particularly during wind conditions such as were present.

Original NASA ASRS Text

Title: S46 Controller expressed concern regarding the operational characteristic of 'FUSED' RADAR; noting the targets 'jump' making it difficult to insure proper instructions are issued.

Narrative: B737-800 was vectored to an ILS Runway 16L approach and cleared for such. B737-900 was vectored in behind B737-800 with the intent to conduct a dual dependent ILS approach to Runway 16R. I had established vertical separation while vectoring the B737-900 onto the final approach course. We were using 'FUSED' RADAR display which has an undesirable characteristic of 'target hopping'; an erratic flight path. I misjudged the distance and turned the aircraft in too close to successfully complete the approach. I broke him off to the southwest when I determined it would not work out. Separation was lost during the escape maneuver. FUSION RADAR sometimes causes a track to display as much as 1/2 mile from actual position. I have seen 'jumps' into adjacent finals followed by accurate depiction of aircraft position. I misjudged rate of turn and wind effects in this situation. [I need to] be more conservative in vectoring aircraft into position for dual-dependent ILS approaches; particularly during wind conditions such as were present.

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	1044902
Time
Date	201210
Local Time Of Day	0001-0600
Place
Locale Reference	S46.TRACON
State Reference	WA
Aircraft 1
Make Model Name	B737-800
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Route In Use	Other Instrument Approach
Flight Plan	IFR
Aircraft 2
Make Model Name	B737-900
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Route In Use	Other Instrument Approach
Flight Plan	IFR
Person 1
Function	Approach Departure
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	ATC Issue All Types Deviation - Procedural Published Material / Policy

S46 controller expressed concern regarding the operational characteristic of 'fused' radar; noting the targets 'jump' making it difficult to insure proper instructions are issued.