Narrative:

I had just made contact with potomac approach for entry into the washington dc sfra and landing at manassas (hef). I was beneath the outer ring of dulles (iad) class B approximately 16 mi west of iad and flying east; when potomac requested 'say intentions.' not taking the hint; I thought they were asking why I was approaching hef from the northwest when traffic was landing to the north. I responded with my intent to enter downwind traffic at manassas. 15 miles west of iad; was informed by potomac that I had entered class B (where the floor lowered to 2500 MSL). I was between 2500-3000 at the time. I descended quickly below the class B floor and leveled off at approximately 2000 MSL as I adjusted course to pass through a gap in an approaching ridgelined. 12 miles [from] iad; potomac again called told me that I had entered iad class B; that the floor was 1500 MSL; and asked me to turn to the south. At this point continued to descend cautiously as I was less than 100 ft. Above nearby obstacles along the ridgeline. I was unable to turn south immediately because this would have taken be across a higher part of the ridgeline again. Once I gained lateral separation from the ridgeline; I turned to the south as I continued to descend to approximately 1400 MSL as I continued toward manassas. Although I am familiar with this part of the washington dc area; and was aware of this particular area where the terrain nearly reaches the floor of the iad class B; it was not entirely apparent to me that this was where I was flying and that I was approaching this trap.

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Original NASA ASRS Text

Title: C177 pilot reported ATC advised him of Class B violations.

Narrative: I had just made contact with Potomac Approach for entry into the Washington DC SFRA and landing at Manassas (HEF). I was beneath the outer ring of Dulles (IAD) Class B approximately 16 mi west of IAD and flying east; when Potomac requested 'say intentions.' Not taking the hint; I thought they were asking why I was approaching HEF from the northwest when traffic was landing to the north. I responded with my intent to enter downwind traffic at Manassas. 15 miles west of IAD; was informed by Potomac that I had entered Class B (where the floor lowered to 2500 MSL). I was between 2500-3000 at the time. I descended quickly below the Class B floor and leveled off at approximately 2000 MSL as I adjusted course to pass through a gap in an approaching ridgelined. 12 miles [from] IAD; Potomac again called told me that I had entered IAD Class B; that the floor was 1500 MSL; and asked me to turn to the south. At this point continued to descend cautiously as I was less than 100 ft. above nearby obstacles along the ridgeline. I was unable to turn south immediately because this would have taken be across a higher part of the ridgeline again. Once I gained lateral separation from the ridgeline; I turned to the south as I continued to descend to approximately 1400 MSL as I continued toward Manassas. Although I am familiar with this part of the Washington DC area; and was aware of this particular area where the terrain nearly reaches the floor of the IAD Class B; it was not entirely apparent to me that this was where I was flying and that I was approaching this trap.

Data retrieved from NASA's ASRS site 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.