NMAC BELOW THE TPA; FL; CLASS B AIRSPACE.

Narrative

WHILE ON AN INST FLT PLAN; MY ACFT; A PIPER CHEROKEE; WAS LEVEL AT 2600 FT MSL ON AN ASSIGNED VECTOR OF 160 DEGS ISSUED BY TPA APCH CTL IN VMC. A TA WAS ISSUED FOR CLBING TFC IN FRONT OF AND BELOW MY LOCATION. I WAS ABLE TO QUICKLY SPOT A BEECHCRAFT BARON IN A CLBING R TURN AT AN 11 O'CLOCK LOW POS; APPROX 1/2 MI AND RAPIDLY CLOSING. KNOWING THAT IMMEDIATE ACTION WAS NECESSARY TO AVOID THE BARON; I BANKED IMMEDIATELY AND SHARPLY TO THE W (A CLBING R TURN) AND AVOIDED THE OTHER ACFT BY LESS THAN 200 FT HORIZ AND ABOUT 75 FT VERT. MY DEV FROM BOTH THE ASSIGNED VECTOR (BY ABOUT 80 DEGS) AND ALT (BY APPROX 200-300 FT) LASTED LESS THAN 1 MIN AND WAS CAUSED BY ACTIONS TO AVOID THE OTHER ACFT. SINCE THE FLOOR OF THE TPA CLASS B AIRSPACE AT THAT POS IS 3000 FT MSL; TECHNICALLY IT APPEARS THAT THE PLT OF THE BARON MAY NOT HAVE BEEN STRICTLY 'REQUIRED' TO BE IN RADIO CONTACT WITH TPA APCH CTL. IT WOULD HAVE BEEN AN EXCELLENT IDEA; HOWEVER; FOR THE BARON TO HAVE EITHER REMAINED CLOSER TO ARPT TFC PATTERN ELEVATION OR USE A REDUCED RATE OF CLB UNTIL CONTACT HAD BEEN ESTABLISHED WITH APCH OR THE ACFT WAS IN LESS CONGESTED AIRSPACE; POSSIBLY TO THE W. IN RETROSPECT; MY ACTIONS TO DEV WERE THE ONLY OPTIONS AVAILABLE TO MINIMIZE THE CONFLICT ONCE IT BEGAN. IT SHOULD BE NOTED THAT DESPITE CONTINUED AND VIGILANT ADHERENCE TO SEE AND AVOID; THIS RPTING PLT MAY WELL HAVE NOT BEEN AFFORDED THE OPPORTUNITY; BECAUSE OF THE RELATIVE POS OF THE ACFT; TO SEE THE RAPIDLY CLBING TWIN IN TIME TO AVOID WITH THE PROMPT; PROFESSIONAL AND ULTIMATELY CRITICAL TA ISSUED BY THE CTLR AT TPA APCH.