AIR TAXI BE02 ENTERS CLASS B AIRSPACE WITHOUT A CLRNC AND CROSSES IN PATH OF APCHING DC8.

Narrative

INBOUND TO BFI ON AN IFR MAINTAINING VFR ON TOP DURING DSCNT. MYSELF UNFAMILIAR WITH THIS AREA. AT 3000 FT MSL SEA APCH ASKED ME TO 'ADVISE CANCELLATION OF IFR.' MY INTENT WAS TO ACCEPT A VISUAL SO I ADVISED 'ARPT IN SIGHT.' CTLR TOLD ME TO 'SQUAWK VFR; CHANGE TO TWR;' THEN 'DISREGARD.' A NEW VOICE CAME ON AND EXPLAINED THAT FROM MY POS (10 MI E OF BFI) I COULD CANCEL AND GO DIRECT TO THE ARPT OR ACCEPT A VISUAL WHICH WOULD TAKE ME OVER SEA- TAC OUT OVER THE BAY (W OF THE ARPT) FOR A TURN TO RWY 13R. I THANKED HIM FOR THE INFO; CANCELED IFR; ADVISED HIM I WAS PLANNING A L DOWNWIND FOR RWY 13R. TOLD MY FO (PF) TO INITIATE DSCNT TO PATTERN ALT (1500 FT AGL). APCH TOLD ME TO 'CONTACT TWR ON 126.3.' I SWITCHED AND CHKED IN WITH TWR. THE CTLR ADVISED ME I SHOULD BE ON THE W SIDE OF THE ARPT OR CONTACT 118.3. I WAS NOT CLR ON WHY I WAS SWITCHED TO THE W CTLR; BUT THOUGHT MAYBE THEY WANTED ME W FOR SEQUENCE. I DISCUSSED THIS QUICKLY WITH MY FO BECAUSE A W PATTERN WOULD MEAN XING THE DEP CORRIDOR FOR BFI AND THE APCH FOR SEA-TAC. MY FO SAID HE THOUGHT THE PATTERN FOR R TFC WAS 800 FT AGL. I TOLD MY FO TO DSND TO 1000 FT (BELOW CLASS B) AS I CALLED TWR AND ADVISED WE WOULD BE R DOWNWIND FOR RWY 13R. AT THAT TIME WE WERE XING THE DEP END OF RWY 13R AND I AM UNSURE OF OUR ALT. TWR ADVISES ME TO 'DSND TO PATTERN ALT 800 FT; YOU ARE IN CLASS BRAVO AIRSPACE AND CUTTING ACROSS THE PATH OF A DC8.' I ACKNOWLEDGED AND WE CONTINUED THE APCH TO LNDG. MY SOLUTIONS TO THE CHAIN OF EVENTS: 1) I NEEDED TO BE MORE AWARE OF THE AIRSPACE (I DID NOT HAVE A TERMINAL AREA CHART); 2) I NEED NOT HAVE CANCELED IFR IN AN UNFAMILIAR AREA; 3) APCH CTL SHOULD NOT BE SUGGESTING CANCELLATION OF IFR AND THEY SHOULD BE SWITCHING ME TO THE PROPER FREQ (118.3 FOR E SIDE); AND 4) BFI SHOULD NOT HAVE LARGE TURBINE ACFT IN ON 800 FT CLOSE PATTERN OR 1000 FT PATTERN (E) FOR THAT MATTER.