C210 ENTERS DCA CLASS B AIRSPACE WITHOUT CLRNC.

Narrative

I WAS ON AN IFR FLT PLAN FROM HPN TO CGS. WX WAS VERY CLR DAY VMC. AFTER XING BAL VOR I INFORMED ATC I WOULD LIKE A VFR APCH INTO CGS. THE ARPT ONLY HAS RNAV IFR APCH AND THOUGH THE ACFT WAS RNAV EQUIPPED; I DID NOT HAVE RNAV APCH CHARTS ON BOARD. THE WX WAS EXTREMELY CLR AND MID- AFTERNOON. I WAS ASKED WHEN I WOULD LIKE TO CANCEL IFR. I CANCELED AT ABOUT 2 MI FROM THE ARPT AND AT 1700 FT MSL. ATC ASKED IF I WANTED TO REMAIN WITH HIM FOR ADVISORIES. I ACCEPTED AND WAS GIVEN SEVERAL TA'S. I NEVER RECEIVED A CLRNC INTO THE CLASS B AIRSPACE WHICH EXTENDED TO 1400 FT MSL. NOT BEING FAMILIAR WITH THE AREA AND NEARLY ALWAYS FLYING IFR I WAS UNAWARE OF THE FLOOR OF THE CLASS B AIRSPACE IN THE VICINITY OF CGS ARPT. COMPLACENCY WITH FLYING IFR AND NOT HAVING REVIEWED A VFR CHART FOR THE AREA RESULTED IN AN INADVERTENT TRANSITION FROM IFR TO VFR AND INTO THE CLASS B AIRSPACE. CANCELING IFR WHILE IN CLASS B AIRSPACE DOES NOT PRESUPPOSE CLRNC INTO THE AIRSPACE; EVEN THOUGH THE CTLR MAKES NO NOTE OF THE TRANSITION. PLANNING AN IFR FLT SHOULD ALSO INCLUDE VFR AIRSPACE AWARENESS.