Narrative:

The IFR flight was nearing the end of its journey from aspen to san carlos (sql). The flight had gone well and about 4 hours had elapsed. The WX was good, and the crew (PF and PNF) had flown many times together using CRM. Prior to reaching sunol intersection, the flight was vectored for a visual approach. We received a very early handoff to san carlos, perhaps 20 mi out. This was well before reaching the class B/C complex in the san francisco bay area. The flight had been high, using a slow descent rate (300-500 FPM) to practice descent planning, capitalize on the speed gained in the descent, and make it comfortable for the passenger. No consideration had been given by the PF (me) to class B/C avoidance because we were IFR. Upon establishing contact with san carlos tower, the PNF accepted the suggestion to cancel IFR. This may have arisen due to the VFR style of initiating contact by the PNF (ie, 'over coyote hills, for landing with current ATIS' versus 'with you on the visual approach'). The flight was descending through approximately 3000 ft at that time. The PNF canceled IFR, but at that point we were about to penetrate the class B and/or oakland class C airspace, but it did not really register with either pilot at that time. I saw our position on the GPS-driven argus map, and suddenly realized we were about to penetrate the class B/C airspace, and we did not have a clearance nor were we in communication with bay or oak tower. I initiated a rapid descent (approximately 2000 FPM) to avoid and/or exit the class B/C airspace. I do not really know if a violation occurred or not. However, whether an airspace violation occurred or not, I believe an unsafe condition existed by virtue of a sudden, rapid descent at low altitude at the edge of busy airspace. While I am not aware of any other airplanes in the vicinity at the time, I must confess I did not look for them prior to descending, either. The airspace issue took precedence in my thinking over possible collision avoidance. In my view, the contributing factors were: fatigue -- after 4 hours in the air, neither pilot comprehended the implications of switching from IFR to VFR at that point in space. Nonstandard procedures -- bay handed the flight off to sql much earlier than usual. (A normal handoff would have occurred in such a way that we would have already been in the class B/C airspace when handed over to sql tower). Also, the PNF used nonstandard phraseology when contacting the tower. Lack of crew coordination - - the PNF should have asked the PF prior to canceling IFR.

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Original NASA ASRS Text

Title: PLT OF A PIPER PA34-200 MAY HAVE INADVERTENTLY PENETRATED CLASS B AIRSPACE DURING A VISUAL DSCNT TO AN UNDERLYING ARPT CAUSED WHEN THE PNF CANCELED THEIR IFR CLRNC. THE RPTING PLT DISCOVERED HIS MISTAKE AND MADE A RAPID DSCNT TO AVOID OR GET OUT OF THE CLASS B AIRSPACE.

Narrative: THE IFR FLT WAS NEARING THE END OF ITS JOURNEY FROM ASPEN TO SAN CARLOS (SQL). THE FLT HAD GONE WELL AND ABOUT 4 HRS HAD ELAPSED. THE WX WAS GOOD, AND THE CREW (PF AND PNF) HAD FLOWN MANY TIMES TOGETHER USING CRM. PRIOR TO REACHING SUNOL INTXN, THE FLT WAS VECTORED FOR A VISUAL APCH. WE RECEIVED A VERY EARLY HDOF TO SAN CARLOS, PERHAPS 20 MI OUT. THIS WAS WELL BEFORE REACHING THE CLASS B/C COMPLEX IN THE SAN FRANCISCO BAY AREA. THE FLT HAD BEEN HIGH, USING A SLOW DSCNT RATE (300-500 FPM) TO PRACTICE DSCNT PLANNING, CAPITALIZE ON THE SPD GAINED IN THE DSCNT, AND MAKE IT COMFORTABLE FOR THE PAX. NO CONSIDERATION HAD BEEN GIVEN BY THE PF (ME) TO CLASS B/C AVOIDANCE BECAUSE WE WERE IFR. UPON ESTABLISHING CONTACT WITH SAN CARLOS TWR, THE PNF ACCEPTED THE SUGGESTION TO CANCEL IFR. THIS MAY HAVE ARISEN DUE TO THE VFR STYLE OF INITIATING CONTACT BY THE PNF (IE, 'OVER COYOTE HILLS, FOR LNDG WITH CURRENT ATIS' VERSUS 'WITH YOU ON THE VISUAL APCH'). THE FLT WAS DSNDING THROUGH APPROX 3000 FT AT THAT TIME. THE PNF CANCELED IFR, BUT AT THAT POINT WE WERE ABOUT TO PENETRATE THE CLASS B AND/OR OAKLAND CLASS C AIRSPACE, BUT IT DID NOT REALLY REGISTER WITH EITHER PLT AT THAT TIME. I SAW OUR POS ON THE GPS-DRIVEN ARGUS MAP, AND SUDDENLY REALIZED WE WERE ABOUT TO PENETRATE THE CLASS B/C AIRSPACE, AND WE DID NOT HAVE A CLRNC NOR WERE WE IN COM WITH BAY OR OAK TWR. I INITIATED A RAPID DSCNT (APPROX 2000 FPM) TO AVOID AND/OR EXIT THE CLASS B/C AIRSPACE. I DO NOT REALLY KNOW IF A VIOLATION OCCURRED OR NOT. HOWEVER, WHETHER AN AIRSPACE VIOLATION OCCURRED OR NOT, I BELIEVE AN UNSAFE CONDITION EXISTED BY VIRTUE OF A SUDDEN, RAPID DSCNT AT LOW ALT AT THE EDGE OF BUSY AIRSPACE. WHILE I AM NOT AWARE OF ANY OTHER AIRPLANES IN THE VICINITY AT THE TIME, I MUST CONFESS I DID NOT LOOK FOR THEM PRIOR TO DSNDING, EITHER. THE AIRSPACE ISSUE TOOK PRECEDENCE IN MY THINKING OVER POSSIBLE COLLISION AVOIDANCE. IN MY VIEW, THE CONTRIBUTING FACTORS WERE: FATIGUE -- AFTER 4 HRS IN THE AIR, NEITHER PLT COMPREHENDED THE IMPLICATIONS OF SWITCHING FROM IFR TO VFR AT THAT POINT IN SPACE. NONSTANDARD PROCS -- BAY HANDED THE FLT OFF TO SQL MUCH EARLIER THAN USUAL. (A NORMAL HDOF WOULD HAVE OCCURRED IN SUCH A WAY THAT WE WOULD HAVE ALREADY BEEN IN THE CLASS B/C AIRSPACE WHEN HANDED OVER TO SQL TWR). ALSO, THE PNF USED NONSTANDARD PHRASEOLOGY WHEN CONTACTING THE TWR. LACK OF CREW COORD - - THE PNF SHOULD HAVE ASKED THE PF PRIOR TO CANCELING IFR.

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.