PLT FLYING AN SMA AND DSNDING TO FLY BELOW THE FLOOR OF CLASS B DOES NOT DSND RAPIDLY ENOUGH AND ENTERS THE CLASS B WITHOUT CLRNC.

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POSSIBLE INADVERTENT INCURSION INTO SEA CLASS B AIRSPACE ON THE SEA 135 DEG RADIAL AT THE 25 MI ARC. (AS SHOWN ON THE SEA VFR TERMINAL AREA CHART). I WAS DSNDING FROM 8500 FT TO 5500 FT; INBOUND ON THE SEA 135 DEG RADIAL; WITH THE INTENTION TO DSND BELOW THE 6000 FT FLOOR OF THE CLASS B AIRSPACE PRIOR TO XING THE 25 MI ARC. I MIGHT HAVE GONE INTO THE CLASS B AIRSPACE AT ABOUT 7000 FT; EXECUTED A 180 DEG TURN TO 135 DEG (MAGNETIC HDG) AND DSNDED TO 5500 FT BEFORE TURNING BACK TO 315 DEG MAGNETIC HDG AND CONTINUING NBOUND UNDER THE FLOOR OF THE AIRSPACE. I WAS USING PILOTAGE AND DEAD RECKONING TO ESTABLISH MY POS RELATIVE TO THE 6000 FT FLOOR OF THE CLASS B AIRSPACE IN THAT AREA. I BELIEVE TAILWINDS CAUSED MY GND SPD TO BE FASTER THAN EXPECTED. WINDS ALOFT FORECAST FOR 6000-9000 FT WERE ABOUT SSW AT 10-13 KTS. SO; I TRAVELED NORTHWARD QUICKER THAN EXPECTED WHILE MAINTAINING A 500 FPM DSCNT RATE. FLT CONDITIONS: HIGH CIRRUS GREATER THAN 10000 FT MSL. VISIBILITY APPROX 60 NM. SLIGHT HAZE. OCCASIONAL LIGHT TURB IN THE VICINITY OF MOUNT RAINIER. WINDS ALOFT SSW 10-13 KTS FORECAST. FREEZING LEVEL FORECAST 2000-4000 FT MSL.