NMAC BTWN A BANNER TOWING CESSNA 182 AND A MIL HELI IN CLASS B AIRSPACE. CAUSED BY ATC NOT ADVISING THE 2 ACFT FLC OF THE OTHER'S PRESENCE.

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MY ACFT WAS TOWING A BANNER SBOUND ON THE BRAVO RTE (A RTE BTWN CRYSTAL PIER AND THE OCEAN BEACH PIER). LINDBERGH TWR HAD GIVEN ME A SQUAWK AND A CLRNC TO ENTER CLASS B AIRSPACE IN ACCORDANCE WITH THE LOA (LOA PRESCRIBES RTE ALONG SHORELINE AT OR BELOW 500 FT AGL). I WAS GIVEN NO FURTHER ADVISORIES. AS MY FLT CROSSED THE OCEAN BEACH PIER; LINDBERGH TWR BEGAN TO RECEIVE XMISSIONS FROM AN ANGRY COAST GUARD HELI CLAIMING THAT THEY HAD MISSED MY BANNER BY 'NO LESS THAN 100 FT.' UNTIL THIS POINT I WAS COMPLETELY UNAWARE OF THE HELI; AND APPARENTLY THEY HAD NOT BEEN INFORMED OF MY PRESENCE. I THINK WHAT OCCURRED HERE WAS DUE; IN LARGE PART; TO A CTLR CHANGE DURING FLT BTWN THE PIERS. I THINK WHAT MAY HAVE HAPPENED; AND THIS CANNOT BE VERIFIED; WAS THAT THE COAST GUARD HELI HAD BEEN OPERATING FOR SEVERAL MINS AT LOW ALT AND HAD NOT SPOKEN TO LINDBERGH FOR SOME TIME. THE LOW ALT CAUSED THE HELI TO DROP-OFF OF RADAR; AND THE DURATION OF RADIO SILENCE COMBINED WITH THE CTLR CHANGE; SIMPLY CAUSED THE HELI TO BE 'FORGOTTEN.' THUS; NEITHER THE HELI; NOR MYSELF WAS INFORMED OF THE OTHER. NOTE: NORMAL PROC ON THE BRAVO RTE IS NOT TO ALLOW ANY ACFT TO ENTER UNLESS THEY HAVE OTHER ACFT 'IN SIGHT;' OR UNLESS ACFT ALREADY ON THE BRAVO RTE HAVE THE ARRIVING ACFT 'IN SIGHT.' IN HUNDREDS OF FLTS ON THE BRAVO RTE; THIS IS MY FIRST EXPERIENCE WITH SUCH A SIT.