A C152 PLT MISHANDLED THE RADIO AND DISPLAYED POOR SITUATIONAL AWARENESS WHICH EVENTUALLY CAUSED AN NMAC IN BFI AIRSPACE.

Narrative

I WAS FLYING A CESSNA 152 OVER DOWNTOWN SEATTLE ON A SIGHTSEEING FLT. I WAS IN CONTACT WITH AND RECEIVING TA FROM BFI TWR DURING THE ENTIRE DURATION OF THE FLT. THERE WERE NUMEROUS TARGETS OVER DOWNTOWN AT THE SAME TIME AND FREQ WAS EXTREMELY BUSY. WHEN RETURNING TO BFI; I PROCEEDED DOWN THE SEATTLE WATERFRONT. I WAS ADVISED TO STAY CLR OF A PLANE TOWING A BANNER ALONG THE SHORE AND PLAN ON ENTERING A R DOWNWIND FOR RWY 31R. TO AVOID THE TFC I ENDED UP OUT OVER ELLIOT BAY INSTEAD OF CLOSER TO THE SHORELINE; WHICH WOULD HAVE BEEN THE IDEAL LINE UP. THE CTLR ASKED IF I WAS OUT OVER THE BAY AND I REPLIED 'AFFIRMATIVE.' I CONTINUED TO PROCEED FOR WHAT WAS NOW TURNING INTO A L DOWNWIND FOR RWY 31. AT THE SAME TIME MY ONE AND ONLY RADIO ON THE ACFT STARTED PICKING UP WHAT SEEMED TO BE OTHER FREQS AND I WAS WORRIED THAT I HAD A RADIO PROB. I RECYCLED THE RADIO AND I STILL DIDN'T HEAR ANYTHING. AT THIS POINT I WAS ABOUT 3 MI FROM THE ARPT LINED UP FOR THE L DOWNWIND (NOT STANDARD). I WAS EXPECTING TO HEAR SOMETHING ON THE FREQ BUT I DIDN'T. AT THE SAME TIME A TWIN TOOK OFF HEADED TOWARDS ME SO I DIDN'T WANT TO CUT OVER AT THIS POINT SO I CONTINUED STRAIGHT AHEAD. WHEN I WAS 2 MI FROM THE ARPT; A PIPER ARROW PASSED ME ON THE R HAND SIDE AT ABOUT THE SAME ALT AND BY ABOUT 300 FT TO THE SIDE. I IMMEDIATELY CALLED THE TWR. SHE ASKED IF I WAS ON THE W SIDE AND I REPLIED AFFIRMATIVE. SHE ASKED ME TO IDENT AND AFTER A LONG BREAK I ASKED FOR INSTRUCTIONS SINCE I WAS ON A MIDFIELD DOWNWIND. SHE CLRED ME TO LAND ON RWY 31L. I MADE THE APCH AND LANDED WITHOUT FURTHER INCIDENT. FACTORS LEADING TO THIS INCIDENT INCLUDE: BUSY AIRSPACE; MY UNFAMILIARITY WITH THE LCL AREA (I HAVE ABOUT 5 HRS FLT TIME IN THE SEATTLE AREA); AND RADIO DIFFICULTIES.