AN LTT COMMUTER IS DSNDED OUT OF CLASS B AIRSPACE BY MEM APCH CTLR. CREW HAD FORGOTTEN THE AIRSPD REQUIREMENTS WHEN BELOW THE FLOOR OF THE CLASS B UNTIL THE CTLR ASKED FOR THEIR INDICATED SPD.

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WHILE ON APCH CTL (MEM); WE WERE BEING VECTORED EXTENSIVELY FOR SPACING (WE WERE NEVER SLOWED). WE WERE ON A 090 DEG HDG AT APPROX 20 DME OFF MEM WHEN WE WERE GIVEN A L TURN TO A HDG OF 180 DEGS. SHORTLY THEREAFTER; WE WERE GIVEN A DSCNT FROM 5000 FT TO 3000 FT; AND SOON THEREAFTER; THE CTLR ASKED WHAT OUR SPD WAS. I REPLIED THAT WE WERE INDICATING 220 KTS. I THEN NOTICED THAT THE DME WAS SHOWING 21 MI. THIS MEANT THAT WE WERE ABOUT 1 MI OUTSIDE THE CLASS B. THE CTLR NEVER MENTIONED THAT WE WERE LEAVING THE CLASS B WHEN HE DSNDED US FROM 5000 FT TO 3000 FT. THE 270 DEG TURN JUST BEFORE THE DSCNT HAD US GOING AWAY FROM THE ARPT AND CONTRIBUTED TO TAKING US OUTSIDE THE 20 DME CIRCLE OF THE CLASS B. IF THE CTLR HAD TOLD US HE WAS TAKING US BELOW THE CLASS B I'M QUITE SURE WE WOULD HAVE NOTICED THE SPD AND SLOWED ACCORDINGLY. SUPPLEMENTAL INFO FROM ACN 396606: NO SPD RESTR WAS SPECIFIED. EVERY DAY AIRLINE CREWS FLY THROUGH CLASS B AIRSPACE AND COME TO RELY ON CTLRS SLOWING OR INCREASING SPDS FOR SPACING. THIS BREEDS SOME COMPLACENCY ON THE CREWS' PART REGARDING FINE POINTS OF AIRSPACE AWARENESS.