HELI HAD NMAC WITH RADIO CTLED MODEL ACFT.

Narrative

I RECENTLY HAD A 'CLOSE ENCOUNTER' WITH A RADIO-CTLED MODEL AIRPLANE JUST OUTSIDE OF PALO ALTO ARPT'S CLASS D AIRSPACE. I'D LEFT PALO ALTO ON A N-EASTERLY HEADING TO TAKE SOME CLIENTS TO A CONSTRUCTION SITE IN NEWARK; MAINTAINING 600 FT AGL TO STAY BELOW INBOUND FIXED-WING TFC ARRIVING FROM THE N. JUST TO THE SW OF THE 'SALT PILE' IN NEWARK I OBSERVED A BRIGHT RED OBJECT PASS IN FRONT OF MY ACFT IN A VERT CLB AND AT A HIGH RATE OF SPD. THE OBJECT WAS VISIBLE FOR ONLY A FEW SECONDS AND I'D ESTIMATE THAT IT PASSED WITHIN 100 FT OF MY ACFT. I'D ENTERED A TIGHT L TURN UPON FIRST SIGHTING THE OBJECT AND AS I COMPLETED THE TURN I NOTICED A RED COLORED MODEL AIRPLANE DSNDING TOWARD THE GND BELOW AND TO THE R OF ME. THE MODEL AIRPLANE CONTINUED ITS DSCNT TOWARD A GREEN- COLORED RECTANGLE ON THE GND. I LEARNED LATER THAT THE GREEN-COLORED RECTANGLE IS A MODEL ACFT 'ARPT' AND IS USED BY LCL ENTHUSIASTS ON A REGULAR BASIS. THE 'SALT PILES' AND THE MODEL AIRPLANE OPERATING AREA ARE LESS THAN A HALF MI FROM ONE ANOTHER. PLTS SHOULD USE CAUTION WHEN RPTING THE 'SALT PILE' PRIOR TO ENTERING PALO ALTO'S CLASS D AIRSPACE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED HE WAS FLYING A HELI. EVASIVE ACTION WAS TAKEN AFTER THE FACT. RPTR WAS INFORMED THERE ARE NO FARS COVERING MODEL ACFT OP.