Narrative:

Pilot visual was being applied throughout the piper's descent from 6;000 ft. Aircraft were about 2.5 NM apart and the conflict alert never activated until the piper descended through the caravan's altitude of 5;000 ft and attained standard separation again at 3;900 ft. After separation was lost and then regained; only then did the conflict alert activate. The conflict alert was definitely not doing its job here and yet we have many instances of two VFR aircraft tail to tail with standard separation and the conflict alert is still flashing. Something is amiss. An additional event involved aircraft that crossed paths and conflict alert did not activate until aircraft were 2-3 NM apart going away from each other with increasing separation. No conflict alert was present while aircraft were 004 apart converging. It should have been activating but did not activate until the event was over. Determine why the conflict alert fails to display during a valid conflict situations.

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Original NASA ASRS Text

Title: ZSE Controller provided several examples of the Conflict Alert function; which according to the reporter; fails to activate when appropriate.

Narrative: Pilot visual was being applied throughout the Piper's descent from 6;000 FT. Aircraft were about 2.5 NM apart and the Conflict Alert never activated until the Piper descended through the Caravan's altitude of 5;000 FT and attained standard separation again at 3;900 FT. After separation was lost and then regained; only then did the Conflict Alert activate. The Conflict Alert was definitely not doing its job here and yet we have many instances of two VFR aircraft tail to tail with standard separation and the Conflict Alert is still flashing. Something is amiss. An additional event involved aircraft that crossed paths and Conflict Alert did not activate until aircraft were 2-3 NM apart going away from each other with increasing separation. No Conflict Alert was present while aircraft were 004 apart converging. It should have been activating but did not activate until the event was over. Determine why the Conflict Alert fails to display during a valid conflict situations.

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.