PLTDEV -- ACR A DEVIATED FROM ASSIGNED ALT DUE TO TCASII ALERT. CTLR WAS INFORMED OF EVASIVE MANEUVER TO BE TAKEN.

Narrative

ACR A RPTED ON THE FREQ AND WAS ISSUED THE RWY TO EXPECT. AFTER A BRIEF PAUSE; THE PLT ADVISED ME THAT HE WOULD HAVE TO AVOID TFC OFF HIS NOSE AND 500 FT BELOW. I ACKNOWLEDGED THE TFC; ASKED IF WAS RECEIVING A RA AND ASKED HIS INTENTIONS. HE STATED THAT TCASII WAS INSTRUCTING HIM TO CLB AND THAT HE WOULD DO SO UNTIL VISUALLY CONTACTING THE TFC. I INFORMED THE PLT TO TAKE WHATEVER ACTION WOULD BE NECESSARY TO AVOID THE TFC AND INFORMED ADJACENT SECTORS THAT MAY BECOME AFFECTED BY ANY MANEUVER THE ACFT COULD TAKE. I OBSERVED ACR A CLBING AND ASKED IF THAT WOULD BE ALL THAT WAS REQUIRED TO COMPLY WITH THE RA AND WAS ACKNOWLEDGED TO THE AFFIRMATIVE. NOW THE WHOLE TIME PRIOR TO; DURING AND SUCCEEDING THIS; APPEARANCE TO TCASII; CONFLICTING TFC NEVER CHANGED COURSE OR LEFT AN ALT OF 9500 FT. AS MOST OF US KNOW; 500 FT IS APPROVED VERT SEPARATION; IN CLASS 'C' AIRSPACE; BTWN AND IFR AND VFR ACFT. THESE 2 ACFT WERE NEVER A CONFLICT. PROJECTED COURSES WOULD HAVE CAUSED THEM TO PASS EACH OTHER WITH MORE THAN STANDARD LATERAL SEPARATION; YET TCASII SAYS THEY WILL HIT THEREFORE INSTRUCTING THE EQUIPPED PLT TO AVOID BY A MEANS THAT HAS THE POTENTIAL TO IMPACT OTHER ACFT AND/OR VIOLATE OTHER CTLR'S AIRSPACE AND DRAMATICALLY INCREASE WORKLOAD. IN THE LAST WK I'VE SEEN AND RPTED 2 OCCURRENCES OF TCASII EVENTS AND ITS IDEAS OF HOW TO MISS EITHER NONEXISTENT TFC OR TFC THAT WAS ALREADY SEPARATED BY VERT AND/OR LATERAL MEANS WITHIN PRESCRIBED MINIMA. NOW THIS TCASII; AS IT IS INTENDED; MIGHT AND SHOULD BE A GOOD THING; BUT UNDER THE CURRENT TECHNOLOGY AND PROGRAMMING IT LACKS THE ABILITY TO INCORPORATE TERRAIN/OBSTRUCTION ELEVATION IN ITS DETERMINING TFC AVOIDANCE AS WELL AS NOT KNOWING WHAT IS ADEQUATE SEPARATION BTWN OTHER ACFT. CONSIDERING THIS; IT IS ALL TOO POSSIBLE FOR TCASII TO INSTRUCT AN AIR CREW TO AVOID TFC AND CAUSING THE ACFT TO CLB INTO ANOTHER OR DSND INTO A RADIO TWR; MOUNTAIN; SKYSCRAPER OR ANOTHER ACFT. MEANWHILE; ONCE THE CTLR HEARS THE WORDS 'RA' FROM ONE OF OUR ACFT; IN OUR JURISDICTION; WE ARE SUPPOSED TO BITE OUR TONGUES; SIT ON OUR HANDS AND WATCH WITHOUT OFFERING ANY ADVICE OR SUGGESTIONS; WHILE TCASII TAKES OVER THE SKIES FOR THAT BRIEF MOMENT; BY TELLING AIR CREWS HOW TO AVOID UNSEEN TFC WITHOUT ANY REGARD FOR OTHER TFC OR TERRAIN/OBSTRUCTION ELEVATION. WHEN I HAVE ASKED AIR CREWS WHY A PARTICULAR OR PRECEDING EVENT HAS OCCURRED THE RESPONSE HAS BEEN ONE OF CONFUSION AND WITH RESERVATION; BUT ALWAYS HAVING THEIR MAINT TECHNICIANS LOOK INTO IT.