Narrative:

Arriving cvg via the mosey 5 arrival; approach began to issue vectors for the ILS runway 36L. While level at 5000 ft and 250 KTS; ATC cleared us to descend to 3000 ft. I suspected that the class B floor in our area was 5000 ft so I asked ATC what the class B floor in our area was. ATC told me to stand by and then said the floor was 5000 ft. I asked ATC if they wanted us to slow to 200 KTS and then descend to 3000 ft. ATC approved. This situation has occurred before. My question is; how much responsibility does the PIC assume concerning the determination of the aircraft's position in relation to the various class B floors/boundaries when operating on an IFR flight plan and complying with radar vectors?

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Original NASA ASRS Text

Title: A CRJ-200 PLT ON THE MOSEY 5 ARR TO CVG WAS ASSIGNED AN ALT BELOW THE FLOOR OF CLASS B AIRSPACE WITHOUT A PROPER SPD ASSIGNMENT.

Narrative: ARRIVING CVG VIA THE MOSEY 5 ARR; APCH BEGAN TO ISSUE VECTORS FOR THE ILS RWY 36L. WHILE LEVEL AT 5000 FT AND 250 KTS; ATC CLRED US TO DSND TO 3000 FT. I SUSPECTED THAT THE CLASS B FLOOR IN OUR AREA WAS 5000 FT SO I ASKED ATC WHAT THE CLASS B FLOOR IN OUR AREA WAS. ATC TOLD ME TO STAND BY AND THEN SAID THE FLOOR WAS 5000 FT. I ASKED ATC IF THEY WANTED US TO SLOW TO 200 KTS AND THEN DSND TO 3000 FT. ATC APPROVED. THIS SITUATION HAS OCCURRED BEFORE. MY QUESTION IS; HOW MUCH RESPONSIBILITY DOES THE PIC ASSUME CONCERNING THE DETERMINATION OF THE ACFT'S POS IN RELATION TO THE VARIOUS CLASS B FLOORS/BOUNDARIES WHEN OPERATING ON AN IFR FLT PLAN AND COMPLYING WITH RADAR VECTORS?

Data retrieved from NASA's ASRS site as of January 2009 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.