SMA PROBABLY ENTERS FLOOR OF CLASS B AIRSPACE.

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I WAS FLYING BTWN MANASSAS; VA (HEF) AND LEESBURG; VA (JYO) INTENDING TO STAY UNDER 1500 FT AND 7.5 DME FROM IAD. THIS FLT PLAN WOULD KEEP ME CLR OF THE CLASS B AIRSPACE. DURING FLT; I ENCOUNTERED LIGHT TURB WHICH INCREASED AS I APCHED HIGH TERRAIN MOUNTAIN W OF DULLES. DURING THIS PERIOD; ACFT MAY HAVE PENETRATED FLOOR OF CLASS B AIRSPACE BY 40-50 FT. I SAY 'MAY' DUE TO THE DIFFERENT ALTIMETER SETTINGS BTWN MANASSAS AND LEESBURG. I BELIEVED MANASSAS WAS 30.38 VERSUS LEESBURG 30.32. WHEN I REALIZED MY POSSIBLE INCURSION INTO THE TCA; I IMMEDIATELY DSNDED TO PROVIDE A GREATER MARGIN BTWN MY ALT AND THE FLOOR OF THE TCA. IN THE VICINITY OF LEESBURG; I FLEW AROUND A BIT DUE TO HVY TFC IN THE PATTERN. AFTER LNDG I PROCEEDED TO THE FBO WHERE I HEARD THAT DULLES APCH AND SOMEONE FROM FLT SVC WANTED TO TALK TO THE PLT OF XYZ; WHICH ARE THE LAST 3 DIGITS OF MY TAIL NUMBER. I PROCEEDED TO FLT SVC WHICH IS ADJACENT TO THE FBO AND INQUIRED AS TO WHO WAS LOOKING FOR ME. THE FLT SPECIALIST WAS UNAWARE OF SUCH AND HE AND I WALKED OVER TO THE FBO AND SPOKE WITH THE COUNTER PERSONNEL. THEY ADVISED APCH CTL HAD CALLED A SECOND TIME AND REQUESTED THAT THE PLT OF XYZ BE ADVISED TO HAVE HIS MODE C VERIFIED. RESULT: MODE C WILL BE VERIFIED. LESSON: ALWAYS ALLOW A GREATER MARGIN OF AIRSPACE WHEN INTENDING TO STAY CLR OF CLASS B AIRSPACE. I LATER LEARNED THAT THE FIRST CALL FROM APCH CTL ADVISED THE FBO THAT XYZ HAD VIOLATED THE TCA.