ATC EQUIP PROB RADAR DATA TAG DROP.

Narrative

THE ARTS DATA TAGS ON ACFT LNDG SFO DISAPPEAR ON ABOUT A 7 MI FINAL AND MAY OR MAY NOT REAPPEAR ON A 2 MI FINAL. OCCASIONALLY THE PRIMARY AND SECONDARY RADAR RETURNS DISAPPEAR AS WELL. THIS CONDITION HAS BEEN HAPPENING FOR AT LEAST 2 WEEKS AND AIRWAYS FACILITIES HAVE NOT FIXED THE PROB. IT IS TRUE THAT THE VAST MAJORITY OF TAGS DISAPPEARING OCCURRED WHEN PLTS TURNED OFF THEIR XPONDERS AS A RESULT OF TCASII ALERTS FIX THE PROB OF PLTS TURNING OFF THEIR XPONDERS DUE TO TCASII. THIS IS THE ACTION THAT INITIATES THE SEQUENCE OF DISAPPEARING TAGS. THERE HAS BEEN SUBSTANTIAL WORK DONE TO INVESTIGATE THE REASON THAT THE TAGS DO NOT 'COAST' AS THE ARTS SYS IS DESIGNED TO DO. I DON'T BELIEVE THAT THE REASON FOR THE TAGS NOT COASTING HAS BEEN DISCOVERED; LET ALONE A FIX FOR THAT PROB. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED FAA MGMNT AND MAINT HAD INVESTIGATED A UCR AND DECLARED THE DROPPED DATA TAG PROB SOLVED. RPTR STATED DATA TAGS ARE NOT GOING INTO COASTING MODE; WHICH GIVES THE CTLR SOME WARNING THE DATA TAG IS GOING TO DROP OFF THE RADAR SCOPE. WHEN THE TAG DROPS DUE TO LACK OF TARGET RESOLUTION SIDE BY ACFT APPEAR AS 1 TARGET. THIS HAPPENS DURING SIDE-BY VISUAL APCH'S.