Narrative:

I departed sql with 3 passenger, 2 of them certified pilots as well. I immediately contacted norcal approach and requested flight following to our destination. My plan had been to remain clear of the sfo class B airspace. However, shortly after acknowledging radar contact, the initial controller (controller a) said 'VFR climb approved, remain at or below 3500 ft.' (the precise words may have differed slightly, but not much.) at this point I was in an area where the class B floor was 2500 ft, and I was unclr as to whether the clearance I had just received constituted permission to enter the class B or not. I queried my fellow pilot-passenger who also thought it unclr, so before climbing through 2500 ft I called the controller back and said, 'confirm I am cleared to climb in class B airspace?' he said, 'that's right, grumman XXXX is cleared to enter the san francisco class B, remain at or below 3500 ft.' I was glad to have clarified things, but also left with the impression that his previous clearance had implicitly cleared me into the class B airspace and that my subsequent call had been unnecessary. A short time later, I was handed off to the next controller on a new frequency, who proceeded to give me a turn and vectored me straight out of class B airspace. Upon exiting I got the standard 'you have left class B airspace, remain clear of class B' warning. He then cleared me to proceed on course, which I did. At this point I was at 3500 ft, in an area where the class B floor is 4000 ft. A couple of mins later, the controller called back and said 'grumman XXXX, VFR climb approved to 5500 ft.' I was nearing the next boundary where the class B floor went up to 6000 ft, and based on my experience with controller 'a' a few mins previous, believed that I had just been cleared to 'cut the corner' through class B and climb up to 5500 ft. Because controller a's clearance seemed to have contained implicit approval for class B entry, I assumed that controller B's clearance, which was virtually identical except for the altitudes involved, also included such implicit clearance. I began climbing, well aware that I was still (barely) in the area where the class B floor is 4000 ft. As I reached the 20 mi boundary, where the class B floor rises to 6000 ft, I was at 4800 ft. At this point the controller called and advsied me that I had busted the class B airspace and that he had not cleared me to enter it, but that I had just left class B again. I apologized and said I had erroneously implied from his climb clearance that I could climb through class B airspace. Clearly I have learned a lesson: I will not enter class B airspace in the future without a specific clearance to enter. I knew such a clearance was required, but believed that the controller was implying clearance just as the previous controller had apparently done, and thought the controllers were just being a bit sloppy. This may have been the case with the first controller, but obviously not with the second. In any case, in the future, I will make sure that an entry clearance is indisputable. However, I think that giving climb clrncs to VFR aircraft flying under a class B floor, where the altitude cleared to is above the floor, should be more explicit to avoid such confusion. It would have been undeniably clear if the controller had said 'climb approved to 5500 ft, remain clear of class B,' or if he had withheld the climb clearance until I was under the 6000 ft floor. Or, he could simply have said, 'cancel altitude restr' which would have let me know that I could choose my altitude, but would not have seemed to imply class B entry clearance. Since it is critical for safety that controllers and pilots share an understanding of what is meant by clrncs given, so that pilots go where they are expected to go, a little more consistency and less ambiguity on the part of ATC instructions would go a long way toward ensuring that pilots and controllers share that same understanding. My 2 pilot-passenger were completely in agreement, when this occurred, that the clearance had been unclr, and both thought (as I did) that I had been cleared to climb through class B airspace.

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Original NASA ASRS Text

Title: AA5 PLT OFF SQL BECAME CONFUSED WITH CTLR'S TERMINOLOGY AS TO WHETHER A CLRNC WAS RECEIVED TO ENTER CLASS B AIRSPACE.

Narrative: I DEPARTED SQL WITH 3 PAX, 2 OF THEM CERTIFIED PLTS AS WELL. I IMMEDIATELY CONTACTED NORCAL APCH AND REQUESTED FLT FOLLOWING TO OUR DEST. MY PLAN HAD BEEN TO REMAIN CLR OF THE SFO CLASS B AIRSPACE. HOWEVER, SHORTLY AFTER ACKNOWLEDGING RADAR CONTACT, THE INITIAL CTLR (CTLR A) SAID 'VFR CLB APPROVED, REMAIN AT OR BELOW 3500 FT.' (THE PRECISE WORDS MAY HAVE DIFFERED SLIGHTLY, BUT NOT MUCH.) AT THIS POINT I WAS IN AN AREA WHERE THE CLASS B FLOOR WAS 2500 FT, AND I WAS UNCLR AS TO WHETHER THE CLRNC I HAD JUST RECEIVED CONSTITUTED PERMISSION TO ENTER THE CLASS B OR NOT. I QUERIED MY FELLOW PLT-PAX WHO ALSO THOUGHT IT UNCLR, SO BEFORE CLBING THROUGH 2500 FT I CALLED THE CTLR BACK AND SAID, 'CONFIRM I AM CLRED TO CLB IN CLASS B AIRSPACE?' HE SAID, 'THAT'S RIGHT, GRUMMAN XXXX IS CLRED TO ENTER THE SAN FRANCISCO CLASS B, REMAIN AT OR BELOW 3500 FT.' I WAS GLAD TO HAVE CLARIFIED THINGS, BUT ALSO LEFT WITH THE IMPRESSION THAT HIS PREVIOUS CLRNC HAD IMPLICITLY CLRED ME INTO THE CLASS B AIRSPACE AND THAT MY SUBSEQUENT CALL HAD BEEN UNNECESSARY. A SHORT TIME LATER, I WAS HANDED OFF TO THE NEXT CTLR ON A NEW FREQ, WHO PROCEEDED TO GIVE ME A TURN AND VECTORED ME STRAIGHT OUT OF CLASS B AIRSPACE. UPON EXITING I GOT THE STANDARD 'YOU HAVE LEFT CLASS B AIRSPACE, REMAIN CLR OF CLASS B' WARNING. HE THEN CLRED ME TO PROCEED ON COURSE, WHICH I DID. AT THIS POINT I WAS AT 3500 FT, IN AN AREA WHERE THE CLASS B FLOOR IS 4000 FT. A COUPLE OF MINS LATER, THE CTLR CALLED BACK AND SAID 'GRUMMAN XXXX, VFR CLB APPROVED TO 5500 FT.' I WAS NEARING THE NEXT BOUNDARY WHERE THE CLASS B FLOOR WENT UP TO 6000 FT, AND BASED ON MY EXPERIENCE WITH CTLR 'A' A FEW MINS PREVIOUS, BELIEVED THAT I HAD JUST BEEN CLRED TO 'CUT THE CORNER' THROUGH CLASS B AND CLB UP TO 5500 FT. BECAUSE CTLR A'S CLRNC SEEMED TO HAVE CONTAINED IMPLICIT APPROVAL FOR CLASS B ENTRY, I ASSUMED THAT CTLR B'S CLRNC, WHICH WAS VIRTUALLY IDENTICAL EXCEPT FOR THE ALTS INVOLVED, ALSO INCLUDED SUCH IMPLICIT CLRNC. I BEGAN CLBING, WELL AWARE THAT I WAS STILL (BARELY) IN THE AREA WHERE THE CLASS B FLOOR IS 4000 FT. AS I REACHED THE 20 MI BOUNDARY, WHERE THE CLASS B FLOOR RISES TO 6000 FT, I WAS AT 4800 FT. AT THIS POINT THE CTLR CALLED AND ADVSIED ME THAT I HAD BUSTED THE CLASS B AIRSPACE AND THAT HE HAD NOT CLRED ME TO ENTER IT, BUT THAT I HAD JUST LEFT CLASS B AGAIN. I APOLOGIZED AND SAID I HAD ERRONEOUSLY IMPLIED FROM HIS CLB CLRNC THAT I COULD CLB THROUGH CLASS B AIRSPACE. CLRLY I HAVE LEARNED A LESSON: I WILL NOT ENTER CLASS B AIRSPACE IN THE FUTURE WITHOUT A SPECIFIC CLRNC TO ENTER. I KNEW SUCH A CLRNC WAS REQUIRED, BUT BELIEVED THAT THE CTLR WAS IMPLYING CLRNC JUST AS THE PREVIOUS CTLR HAD APPARENTLY DONE, AND THOUGHT THE CTLRS WERE JUST BEING A BIT SLOPPY. THIS MAY HAVE BEEN THE CASE WITH THE FIRST CTLR, BUT OBVIOUSLY NOT WITH THE SECOND. IN ANY CASE, IN THE FUTURE, I WILL MAKE SURE THAT AN ENTRY CLRNC IS INDISPUTABLE. HOWEVER, I THINK THAT GIVING CLB CLRNCS TO VFR ACFT FLYING UNDER A CLASS B FLOOR, WHERE THE ALT CLRED TO IS ABOVE THE FLOOR, SHOULD BE MORE EXPLICIT TO AVOID SUCH CONFUSION. IT WOULD HAVE BEEN UNDENIABLY CLR IF THE CTLR HAD SAID 'CLB APPROVED TO 5500 FT, REMAIN CLR OF CLASS B,' OR IF HE HAD WITHHELD THE CLB CLRNC UNTIL I WAS UNDER THE 6000 FT FLOOR. OR, HE COULD SIMPLY HAVE SAID, 'CANCEL ALT RESTR' WHICH WOULD HAVE LET ME KNOW THAT I COULD CHOOSE MY ALT, BUT WOULD NOT HAVE SEEMED TO IMPLY CLASS B ENTRY CLRNC. SINCE IT IS CRITICAL FOR SAFETY THAT CTLRS AND PLTS SHARE AN UNDERSTANDING OF WHAT IS MEANT BY CLRNCS GIVEN, SO THAT PLTS GO WHERE THEY ARE EXPECTED TO GO, A LITTLE MORE CONSISTENCY AND LESS AMBIGUITY ON THE PART OF ATC INSTRUCTIONS WOULD GO A LONG WAY TOWARD ENSURING THAT PLTS AND CTLRS SHARE THAT SAME UNDERSTANDING. MY 2 PLT-PAX WERE COMPLETELY IN AGREEMENT, WHEN THIS OCCURRED, THAT THE CLRNC HAD BEEN UNCLR, AND BOTH THOUGHT (AS I DID) THAT I HAD BEEN CLRED TO CLB THROUGH CLASS B AIRSPACE.

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.