FLC OF LTT IN SLOW CLB HAD NMAC WITH SMA.

Narrative

WE WERE TRACKING THE DFW 090 DEG RADIAL AT 4000 FT. OUR SPD WAS 200 KIAS SINCE WE WERE BELOW THE TCA. REGIONAL DEP KEEPS US BELOW THE TCA MOST OF THE TIME! WHY? I THOUGHT TCA AIRSPACE WAS SUPPOSED TO BE TO PROTECT ACFT; NOT TO KEEP'EM BELOW IT! WHY DOES THIS HAPPEN EVERYDAY? IT IS UNSAFE TO KEEP AIRLINERS/ACFT BELOW TCA'S. WHY DOES DEP CTL DO THAT? ONCE OUTSIDE THE LATERAL LIMITS OF THE TCA AT 21 NM; WE SPED UP TO 230 KIAS AND WERE CLRED TO 5000 FT. I HAD MY NAV STROBE AND BOTH WING MOUNTED LNDG LIGHTS ON. I CLBED SHALLOW AT 500 FPM. ALL OF A SUDDEN I SAW AN SMA OUT OF THE CORNER OF MY EYE. WE WERE SO CLOSE; I ONLY SAW IT FOR A 1-2 SECONDS. NO TIME TO DO ANYTHING OTHER THAN SCREAM. SHORTLY THEREAFTER; 2-5 MIN; WE WERE IMC AND I REQUESTED LOWER TO 4000 FT. ALSO RPTED INCIDENT TO CENTER. I WANTED TO GET OUT OF THE CLOUDS! BECAUSE I WAS SCARED OF NOT BEING ABLE TO SEE MORE TFC. CENTER COULD NOT GIVE US LOWER; SO I CANCELLED IFR AND DSNDED TO 3000 FT WITH RADAR SVC. CENTER CALLED IN TYR ON THE GND TO GET INFO ABOUT THE NEAR HIT.