Narrative:

WX briefing from ukiah to watsonville alerted me to presence of fog along my route and to some extent inland, and that's somewhat normal especially along the coast. Departing ukiah at XA00 am for the 2 hour flight and expecting clearing of the fog as I progressed, I was expecting an easy flight. My flight plan called for using the sgd VOR outbound, on the 125 degree radial at 5500 ft which would take me through the I sector of the san francisco class B airspace under the 6000-8000 ft altitude. As I approached this area, the fog was higher and my gliding distance to clear ground, visibility beneath me increased as the fog was more to the east than anticipated. For safety, I climbed to 7500 ft and turned to the east and aligned myself with the 120 degree radial thinking this would be enough to divert the class B airspace altogether. At the same time, I radioed center for flight following. I was informed that I was unauthorized to be in class B airspace. I replied I would drop altitude and he replied to continue at present flight level, 7500 ft. Part of the problem was not being able to see highway 680 that helps define the eastern part of the airspace. Mt diablo sits just outside the I sector and I thought I was close enough, but that was not the case. In retrospect, I should have gone around the mountain instead of cutting it too close on the western side. Being unsure of my position over the ground, a call to ATC for clearance before entering class B would have been most prudent.

Related reports:

Google
 

Original NASA ASRS Text

Title: AN SMA PLT, CONCERNED ABOUT FOG BELOW, CLBED INTO THE SFO CLASS B AIRSPACE WITHOUT CLRNC.

Narrative: WX BRIEFING FROM UKIAH TO WATSONVILLE ALERTED ME TO PRESENCE OF FOG ALONG MY RTE AND TO SOME EXTENT INLAND, AND THAT'S SOMEWHAT NORMAL ESPECIALLY ALONG THE COAST. DEPARTING UKIAH AT XA00 AM FOR THE 2 HR FLT AND EXPECTING CLRING OF THE FOG AS I PROGRESSED, I WAS EXPECTING AN EASY FLT. MY FLT PLAN CALLED FOR USING THE SGD VOR OUTBOUND, ON THE 125 DEG RADIAL AT 5500 FT WHICH WOULD TAKE ME THROUGH THE I SECTOR OF THE SAN FRANCISCO CLASS B AIRSPACE UNDER THE 6000-8000 FT ALT. AS I APCHED THIS AREA, THE FOG WAS HIGHER AND MY GLIDING DISTANCE TO CLR GND, VISIBILITY BENEATH ME INCREASED AS THE FOG WAS MORE TO THE E THAN ANTICIPATED. FOR SAFETY, I CLBED TO 7500 FT AND TURNED TO THE E AND ALIGNED MYSELF WITH THE 120 DEG RADIAL THINKING THIS WOULD BE ENOUGH TO DIVERT THE CLASS B AIRSPACE ALTOGETHER. AT THE SAME TIME, I RADIOED CTR FOR FLT FOLLOWING. I WAS INFORMED THAT I WAS UNAUTH TO BE IN CLASS B AIRSPACE. I REPLIED I WOULD DROP ALT AND HE REPLIED TO CONTINUE AT PRESENT FLT LEVEL, 7500 FT. PART OF THE PROB WAS NOT BEING ABLE TO SEE HWY 680 THAT HELPS DEFINE THE EASTERN PART OF THE AIRSPACE. MT DIABLO SITS JUST OUTSIDE THE I SECTOR AND I THOUGHT I WAS CLOSE ENOUGH, BUT THAT WAS NOT THE CASE. IN RETROSPECT, I SHOULD HAVE GONE AROUND THE MOUNTAIN INSTEAD OF CUTTING IT TOO CLOSE ON THE WESTERN SIDE. BEING UNSURE OF MY POSITION OVER THE GND, A CALL TO ATC FOR CLRNC BEFORE ENTERING CLASS B WOULD HAVE BEEN MOST PRUDENT.

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.