Narrative:

I flew from ccr to haf via richmond, oak, the san mateo bridge, and sql. Bay approach instructed me to proceed from richmond and to cross the mormon temple at 2500 ft MSL. After passing the mormon temple, I was directed to fly to the oakland coliseum and to contact the north oakland tower on 118.3. I switched frequencys and gave the tower my full call sign and altitude (still 2500 ft MSL). The north tower directed me toward the 'numbers' of runway 29 and handed me off to the south tower on 127.2. Again I checked in with my full call sign and indicated altitude (still 2500 ft MSL). The south tower controller instructed me to fly over the 'numbers' of runway 29 and then to the mid-span of the san mateo bridge. At this point, I was concerned about my altitude (I was about to encounter a portion of the sfo class B airspace with a floor of 2100 ft MSL), so I asked the controller to '...verify that aircraft X was cleared to enter class B airspace at 2500 ft.' he responded negatively and said to cross the 'numbers' of runway 29 at 2000 ft -- this was the first altitude assignment I received since my first one from bay approach. I descended immediately and do not think I penetrated the class B airspace, but it was certainly close. I would encourage ATC to be consistent when controling traffic within the tight quarters of class B and class C airspace. From the point of view of the pilot, we maintain an ATC-assigned altitude until 1) given another altitude to hold, or 2) advised to change altitude at our discretion to remain clear of class B airspace. Similarly, I would also encourage pilots to not be lulled into a false sense of security -- just because we're talking to ATC doesn't mean that we no longer have to avoid airspace we don't belong in.

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Original NASA ASRS Text

Title: A PIPER WARRIOR PLT NEARLY ENTERED SFO CLASS B AIRSPACE WITHOUT A CLRNC.

Narrative: I FLEW FROM CCR TO HAF VIA RICHMOND, OAK, THE SAN MATEO BRIDGE, AND SQL. BAY APCH INSTRUCTED ME TO PROCEED FROM RICHMOND AND TO CROSS THE MORMON TEMPLE AT 2500 FT MSL. AFTER PASSING THE MORMON TEMPLE, I WAS DIRECTED TO FLY TO THE OAKLAND COLISEUM AND TO CONTACT THE N OAKLAND TWR ON 118.3. I SWITCHED FREQS AND GAVE THE TWR MY FULL CALL SIGN AND ALT (STILL 2500 FT MSL). THE N TWR DIRECTED ME TOWARD THE 'NUMBERS' OF RWY 29 AND HANDED ME OFF TO THE S TWR ON 127.2. AGAIN I CHKED IN WITH MY FULL CALL SIGN AND INDICATED ALT (STILL 2500 FT MSL). THE S TWR CTLR INSTRUCTED ME TO FLY OVER THE 'NUMBERS' OF RWY 29 AND THEN TO THE MID-SPAN OF THE SAN MATEO BRIDGE. AT THIS POINT, I WAS CONCERNED ABOUT MY ALT (I WAS ABOUT TO ENCOUNTER A PORTION OF THE SFO CLASS B AIRSPACE WITH A FLOOR OF 2100 FT MSL), SO I ASKED THE CTLR TO '...VERIFY THAT ACFT X WAS CLRED TO ENTER CLASS B AIRSPACE AT 2500 FT.' HE RESPONDED NEGATIVELY AND SAID TO CROSS THE 'NUMBERS' OF RWY 29 AT 2000 FT -- THIS WAS THE FIRST ALT ASSIGNMENT I RECEIVED SINCE MY FIRST ONE FROM BAY APCH. I DSNDED IMMEDIATELY AND DO NOT THINK I PENETRATED THE CLASS B AIRSPACE, BUT IT WAS CERTAINLY CLOSE. I WOULD ENCOURAGE ATC TO BE CONSISTENT WHEN CTLING TFC WITHIN THE TIGHT QUARTERS OF CLASS B AND CLASS C AIRSPACE. FROM THE POINT OF VIEW OF THE PLT, WE MAINTAIN AN ATC-ASSIGNED ALT UNTIL 1) GIVEN ANOTHER ALT TO HOLD, OR 2) ADVISED TO CHANGE ALT AT OUR DISCRETION TO REMAIN CLR OF CLASS B AIRSPACE. SIMILARLY, I WOULD ALSO ENCOURAGE PLTS TO NOT BE LULLED INTO A FALSE SENSE OF SECURITY -- JUST BECAUSE WE'RE TALKING TO ATC DOESN'T MEAN THAT WE NO LONGER HAVE TO AVOID AIRSPACE WE DON'T BELONG IN.

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.