EMI; RF INTERFERENCE CLAIMED TO HAVE CONTRIBUTED TO THE LOSS OF TCASII CAPABILITY WHEN PIC OF A S-80 HAS TO SELECT THE NUMBER TWO (2) TRANSPONDER DUE TO THE LOSS OF THE NUMBER ONE (1) TRANSPONDER AFTER DEP SFO; CA.

Narrative

DEPARTING SFO WE WERE ADVISED THAT ATC WAS NOT RECEIVING OUR TRANSPONDER. THE ATC FAIL LIGHT WAS ON AS WELL AS NUMEROUS TCASII FAULT MESSAGES. WE SWITCHED TO TRANSPONDER NO 2 AS PER THE OPERATING MANUAL AND ATC WAS ABLE TO RECEIVE IT. THE AIRPLANE HAD ONLY ONE MODE S TRANSPONDER SO WE HAD NO TCASII AT THIS POINT. THE FLT CONTINUED NORMALLY FOR ANOTHER HR OR SO WITH NO CHANGE IN THE STATUS OF THE NUMBER 1 TRANSPONDER AND TCASII. IT WAS AT THIS POINT THAT I DISCOVERED THAT I HAD INADVERTENTLY LEFT MY PCS PHONE ON. AND THAT IT WAS IN SEARCH MODE. I TURNED IT OFF. IMMEDIATELY; ATC NO 1 AND TCAS WERE RESTORED TO FULL FUNCTIONALITY. NO FURTHER ANOMALIES WERE OBSERVED DURING THE FLT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THAT WITHOUT THE TRANSPONDER INTERROGATOR ON SYSTEM ONE (1); THE TCAS SYSTEM BECAME INOPERATIVE; THAT THE ATC FAIL LIGHT WAS INDICATING ON THE TRANSPONDER #1 HEAD WITH TCAS SCREEN SHOWING; 'XPDR DATA BUS'; AND THE TCASII FAIL FLAG WAS SHOWING IN THE VERTICAL SPEED INDICATOR FOR THE R/A FUNCTION. THE RPTR FEELS THAT ACFT ARE AFFECTED DIFFERENTLY BY THE CELL PHONE'S RF/EMI OUTPUT. THE RPTR ALLEGES THAT THE CELL PHONE WHEN LEFT ON; IS NOT IN PASSIVE SEARCHING; BUT MOST LIKELY LOCKED ONTO THE FMS. HE HAS CONTACTED COMPANY ABOUT THIS INCIDENT AND THEY ADVISED THEY ARE RESEARCHING THE PROBLEM. THE CELL PHONE MODEL IS A MOTOROLA 'STAR TAC.