Narrative:

I was on a VFR flight plan from gky, tx, to apa, co, at 10500 ft, with flight following and approximately 10 mi southeast of denver class B airspace. There was a substantial forest fire southwest of denver, and the smoke plume was between my position and centennial. There appeared to be approximately 5 mi visibility through the plume. Denver approach was very busy. As I approached class B airspace, there was little opportunity to speak with ATC for clearance, so I started to divert to the west to avoid entering class B airspace without clearance. ATC said something that I heard as, 'descend below 9000 ft to avoid class B airspace,' but at my request the controller repeated what he had said, which was 'cleared to descend below 9000 ft through class B airspace.' so , I resumed on course navigation to centennial, and began my descent. Shortly after entering class B airspace, and before I had completed my descent, ATC said, 'radar services terminated, squawk VFR,' which, of course, I did. At that point I was still a few mi from centennial, and quite high. Centennial tower was also very busy, and I had trouble getting through. To avoid entering centennial's class D airspace, I circled to the east, towards aurora reservoir. Because of the MVFR visibility (from the smoke), I was reluctant to descend to pattern altitude while I was so far from the airport environment. I finally was able to speak with centennial tower, and told to enter a left downwind for runway 17L, and report abeam the tower. (I created some confusion in my initial contact with the tower by reporting myself west instead of east of the airport -- a word mixup. When tower said that they didn't see me west, I realized my mistake and corrected it. At that point, I was still almost 10 mi from the airport.) I landed without incident. After landing, tower asked some questions on the radio, and I then (on my own volition) called and spoke further with tower about what had happened. It appears that after my radar services were terminated, and after I changed my squawk code to 1200, I showed up on denver approach radar as a VFR aircraft in class B airspace. The approach controller apparently forgot that I had been cleared into class B airspace, so he called centennial tower to identify me, and to have me questioned about why I was in class B airspace with a VFR squawk code. Tower thought that the problem had arisen because my radar services were terminated prematurely. My thought on the matter is that since I was on a VFR flight plan, I could be terminated at any point. I believed that my clearance to descend through class B airspace was a clearance into class B airspace, and then didn't think about the matter any further. I was rather surprised when the controller terminated me, but I should have had the presence of mind (and will next time) to ask if I was still cleared through class B airspace. Now that I think about it, I'm not sure that a clearance to 'descend through class B airspace to 9000 ft' is a clearance to remain in class B airspace after radar services are terminated. While I think the controller should have been a bit more specific, the primary responsibility for clarifying the situation was on me, the PIC, and I should have asked for clarification on whether I was cleared to remain in class B airspace while maneuvering east of centennial. Next time, I will be more careful to clarify any ambiguities.

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Original NASA ASRS Text

Title: D01 RADAR APCH CTLR BELIEVED THAT A C182 DSNDING INTO APA AIRSPACE FOR LNDG DID NOT HAVE DSCNT CLRNC THROUGH D01 CLASS B AIRSPACE. PLT REMINDED ATC THAT HE WAS CLRED THROUGH AND INSTRUCTED TO SQUAWK VFR.

Narrative: I WAS ON A VFR FLT PLAN FROM GKY, TX, TO APA, CO, AT 10500 FT, WITH FLT FOLLOWING AND APPROX 10 MI SE OF DENVER CLASS B AIRSPACE. THERE WAS A SUBSTANTIAL FOREST FIRE SW OF DENVER, AND THE SMOKE PLUME WAS BTWN MY POS AND CENTENNIAL. THERE APPEARED TO BE APPROX 5 MI VISIBILITY THROUGH THE PLUME. DENVER APCH WAS VERY BUSY. AS I APCHED CLASS B AIRSPACE, THERE WAS LITTLE OPPORTUNITY TO SPEAK WITH ATC FOR CLRNC, SO I STARTED TO DIVERT TO THE W TO AVOID ENTERING CLASS B AIRSPACE WITHOUT CLRNC. ATC SAID SOMETHING THAT I HEARD AS, 'DSND BELOW 9000 FT TO AVOID CLASS B AIRSPACE,' BUT AT MY REQUEST THE CTLR REPEATED WHAT HE HAD SAID, WHICH WAS 'CLRED TO DSND BELOW 9000 FT THROUGH CLASS B AIRSPACE.' SO , I RESUMED ON COURSE NAV TO CENTENNIAL, AND BEGAN MY DSCNT. SHORTLY AFTER ENTERING CLASS B AIRSPACE, AND BEFORE I HAD COMPLETED MY DSCNT, ATC SAID, 'RADAR SVCS TERMINATED, SQUAWK VFR,' WHICH, OF COURSE, I DID. AT THAT POINT I WAS STILL A FEW MI FROM CENTENNIAL, AND QUITE HIGH. CENTENNIAL TWR WAS ALSO VERY BUSY, AND I HAD TROUBLE GETTING THROUGH. TO AVOID ENTERING CENTENNIAL'S CLASS D AIRSPACE, I CIRCLED TO THE E, TOWARDS AURORA RESERVOIR. BECAUSE OF THE MVFR VISIBILITY (FROM THE SMOKE), I WAS RELUCTANT TO DSND TO PATTERN ALT WHILE I WAS SO FAR FROM THE ARPT ENVIRONMENT. I FINALLY WAS ABLE TO SPEAK WITH CENTENNIAL TWR, AND TOLD TO ENTER A L DOWNWIND FOR RWY 17L, AND RPT ABEAM THE TWR. (I CREATED SOME CONFUSION IN MY INITIAL CONTACT WITH THE TWR BY RPTING MYSELF W INSTEAD OF E OF THE ARPT -- A WORD MIXUP. WHEN TWR SAID THAT THEY DIDN'T SEE ME W, I REALIZED MY MISTAKE AND CORRECTED IT. AT THAT POINT, I WAS STILL ALMOST 10 MI FROM THE ARPT.) I LANDED WITHOUT INCIDENT. AFTER LNDG, TWR ASKED SOME QUESTIONS ON THE RADIO, AND I THEN (ON MY OWN VOLITION) CALLED AND SPOKE FURTHER WITH TWR ABOUT WHAT HAD HAPPENED. IT APPEARS THAT AFTER MY RADAR SVCS WERE TERMINATED, AND AFTER I CHANGED MY SQUAWK CODE TO 1200, I SHOWED UP ON DENVER APCH RADAR AS A VFR ACFT IN CLASS B AIRSPACE. THE APCH CTLR APPARENTLY FORGOT THAT I HAD BEEN CLRED INTO CLASS B AIRSPACE, SO HE CALLED CENTENNIAL TWR TO IDENT ME, AND TO HAVE ME QUESTIONED ABOUT WHY I WAS IN CLASS B AIRSPACE WITH A VFR SQUAWK CODE. TWR THOUGHT THAT THE PROB HAD ARISEN BECAUSE MY RADAR SVCS WERE TERMINATED PREMATURELY. MY THOUGHT ON THE MATTER IS THAT SINCE I WAS ON A VFR FLT PLAN, I COULD BE TERMINATED AT ANY POINT. I BELIEVED THAT MY CLRNC TO DSND THROUGH CLASS B AIRSPACE WAS A CLRNC INTO CLASS B AIRSPACE, AND THEN DIDN'T THINK ABOUT THE MATTER ANY FURTHER. I WAS RATHER SURPRISED WHEN THE CTLR TERMINATED ME, BUT I SHOULD HAVE HAD THE PRESENCE OF MIND (AND WILL NEXT TIME) TO ASK IF I WAS STILL CLRED THROUGH CLASS B AIRSPACE. NOW THAT I THINK ABOUT IT, I'M NOT SURE THAT A CLRNC TO 'DSND THROUGH CLASS B AIRSPACE TO 9000 FT' IS A CLRNC TO REMAIN IN CLASS B AIRSPACE AFTER RADAR SVCS ARE TERMINATED. WHILE I THINK THE CTLR SHOULD HAVE BEEN A BIT MORE SPECIFIC, THE PRIMARY RESPONSIBILITY FOR CLARIFYING THE SIT WAS ON ME, THE PIC, AND I SHOULD HAVE ASKED FOR CLARIFICATION ON WHETHER I WAS CLRED TO REMAIN IN CLASS B AIRSPACE WHILE MANEUVERING E OF CENTENNIAL. NEXT TIME, I WILL BE MORE CAREFUL TO CLARIFY ANY AMBIGUITIES.

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.