Narrative:

I was flying between manassas, va (hef) and leesburg, va (jyo) intending to stay under 1500 ft and 7.5 DME from iad. This flight plan would keep me clear of the class B airspace. During flight, I encountered light turbulence which increased as I approached high terrain mountain west of dulles. During this period, aircraft may have penetrated floor of class B airspace by 40-50 ft. I say 'may' due to the different altimeter settings between manassas and leesburg. I believed manassas was 30.38 versus leesburg 30.32. When I realized my possible incursion into the TCA, I immediately descended to provide a greater margin between my altitude and the floor of the TCA. In the vicinity of leesburg, I flew around a bit due to heavy traffic in the pattern. After landing I proceeded to the FBO where I heard that dulles approach and someone from flight service wanted to talk to the pilot of xyz, which are the last 3 digits of my tail number. I proceeded to flight service which is adjacent to the FBO and inquired as to who was looking for me. The flight specialist was unaware of such and he and I walked over to the FBO and spoke with the counter personnel. They advised approach control had called a second time and requested that the pilot 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 clear of class B airspace. I later learned that the first call from approach control advised the FBO that xyz had violated the TCA.

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Original NASA ASRS Text

Title: SMA PROBABLY ENTERS FLOOR OF CLASS B AIRSPACE.

Narrative: 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.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.