PENETRATED THE TCA WITHOUT CLRNC.

Narrative

THE ARPT IS SITUATED UNDER THE SEASTERN-MOST EDGE OF THE STL TCA. I KNEW FROM EXPERIENCE THAT I HAD TO HOLD MY ALT BELOW 2000' WHEN ON NBOUND COURSE AND BELOW 3000' WBOUND. THE COMMON WISDOM IS THAT DEPS TO THE S AND TO THE E ARE NORMALLY SUCH THAT BY THE TIME ONE CLBS TO 3000'; HE IS WELL CLR OF THE TCA. MY FIRST ENRTE FIX WAS TO BE THE FARMINGTON VOR; WHICH IS ON A BEARING OF 180 DEGS FROM THE ARPT. I TAXIED FROM MY HANGAR TO THE RAMP AND CALLED GND CTL ADVISING THAT I HAD ATIS AND WISHED A SBND VFR DEP. WINDS THAT DAY WERE CALM. I WAS ASSIGNED RWY 4. THIS WAS UNUSUAL. THE BULK OF THE DEPS FROM DOWNTOWN ARE ON EITHER RWY 12R-30L OR 12L-30R. RWY 4-22 IS A SHORTER RWY WITH POWERLINE OBSTRUCTIONS AND NOT USED WITH NEARLY THE SAME FREQUENCY AS THE 2 LONGER ONES. THOUGH I DID NOT REFLECT ON IT AT THE TIME; I NOW RECALL THAT I HAD NEVER BEEN ASSIGNED RWY 4 FOR A SBND ON COURSE HDG. I WAS THEREFORE NOT AWARE THAT ITS USE ON A SBND HDG COULD LEAD TO A DANGEROUS SITUATION. I TAXIED TO THE RUNUP AREA; COMPLETED RUNUP; AND CALLED THE TWR. I WAS CLRED FOR TKOF; LEFT TURN APPROVED. AFTER TKOF AND GAINING ABOUT 500' AGL; I BEGAN A CLBING LEFT TURN TO MY ON COURSE HDG OF 180 DEGS. SINCE I HAD DEPARTED ON RWY 4; THIS AMOUNTED TO A TOTAL CHANGE IN HDG OF 220 DEGS. I TURNED GRADUALLY WHILE CLBING AND I CONTINUE TO CLB AS I APCHED MY 180 DEG HDG. HOWEVER; WHEN I WAS OVER THE RIVER SBND AT 3500'; I RECEIVED A CALL FROM THE DOWNTOWN CTLR ADVISING ME THAT I HAD VIOLATED THE TCA. AT THE TIME OF THE CALL; I WAS WELL S OF THE JEFFERSON BARRACKS BRIDGE AND I KNEW IT WAS CLR OF THE TCA. THUS; I ACKNOWLEDGED THE XMISSION AND PROCEEDED TO MY DEST. I WAS; AND I REMAIN; SHOCKED THAT THIS MIGHT HAVE HAPPENED. MY TRNING AND MY PILOTAGE HAS EMPHASIZED CAREFUL AVOIDANCE OF THE TCA UNDER VFR FLT. AFTER ANALYSIS OF THE CHARTS I CAN SEE HOW IT COULD HAVE HAPPENED AND HOW IT COULD BE AVOIDED IN THE FUTURE. MOST PLTS AT DOWNTOWN FEEL THAT THE TCA FLOOR ABOVE THE ARPT IS OF CONCERN ONLY ON ROUTES THAT ARE NBOUND CLOCKWISE THROUGH SEBND. THIS IS BORNE OUT BY THE RWY ALIGNMENTS OF THE 2 MAJOR RWYS. A DEP ON 12R OR 12L TAKES THE PLT FROM UNDER THE 3000' TCA FLOOR AT THE END OF THE RWY TO A FLOOR OF 4500'. DEPARTING ON RWY 30L OR 30R FOLLOWED BY A CLBING LEFT TURN OF 120 DEGS PUTS HIM EASILY OUT FROM BELOW THE TCA WHEN HE REACHES A HDG OF 180 DEGS. THE TIME REQUIRED FIRST TO CLR THE OBSTACLES AT THE END OF RWY 4; GAINING ALT AND TRAVELING FARTHER N; AND THEN MAKE A CLBING TURN THROUGH 220 DEGS COULD ALLOW THE AIRPLANE TO CLB THROUGH THE 2500' TO THE BASE OF THE TCA. I WOULD MAKE THE FOLLOWING RECOMMENDATIONS TO PREVENT ANOTHER SITUATION LIKE I EXPERIENCED. FIRST; CTLRS SHOULD NORMALLY NOT ASSIGN RWY 4 FOR SBND DEP. SECOND; IF ITS USE IS NECESSARY; RIGHT TURNS SHOULD BE RECOMMENDED TO DIRECT THE TFC AWAY FROM THE TCA; THIRD; PLTS; PARTICULARLY THOSE IN TRNING AT THE ARPT; SHOULD BE MADE AWARE OF THE FALSE SENSE OF SECURITY THAT THEY CAN DEVELOP ON SBND HDGS.