A FOKKER 27 AT 6000 FT DECLARED AN EMER AND DIVERTED DUE TO #2 ENG FIRE WARNING LIGHT AND BELL CAUSED BY A FAULTY FIRE DETECTION LOOP.

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I FLY AS A FO ABOARD AN F27 FOR A CARGO COMPANY; 2 CREW MEMBERS ON BOARD. WE WERE ENRTE FROM ONT TO SBA (40 MIN FLT). 25 MINS INTO THE FLT; JUST PAST FILLMORE VOR; WE HAD A FIRE WARNING LIGHT WITH A BELL; COME ON. I WAS FLYING; WE WERE AT CRUISE; 6000 FT. THE CAPT SILENCED THE BELL; THE LIGHT STAYED ILLUMINATED; INDICATING THE R ENG FIRE. FROM MY WINDOW IN THE COCKPIT; I CAN SEE ALL BUT THE LAST FOOT OF THE ENG. THE EXHAUST PIPE IS ON THE OUTBOARD OF THE NACELLE; SO I WAS UNABLE TO SEE THAT. I ASKED THE CAPT TO FLY; SO I COULD GET A GOOD LOOK AT THE ENG. I COULD SEE NO FIRE OR SMOKE WHICH I CONVEYED TO THE CAPT. I SAID 'WE WILL STILL HAVE TO SHUT IT DOWN BECAUSE THE LIGHT IS ILLUMINATED.' HE HESITANTLY AGREED. HE WAS STILL FLYING; WHILE I WENT THROUGH THE CHKLIST. IN 4 STEPS THE ENG WAS SHUT DOWN. THE NEXT STEP ON THE CHKLIST READS 'IF FIRE EXISTS' FIRE BOTTLE #1...FIRE. WITH THE FIRST WARNING LIGHT STILL ILLUMINATED; I TOLD THE CAPT TO FIRE #1. HE DECIDED TO CHK THE ENG HIMSELF AND DID NOT WANT TO SHOOT THE FIRE BOTTLE. THE CAPT HAD ME TAKE THE CTLS WHILE HE STOOD BEHIND MY SEAT TO LOOK OUT THE WINDOW. HE SAID THERE WAS NO VISUAL SIGN THAT FIRE EXISTS. I INFORMED HIM THE LIGHT WAS STILL ON; AND THERE WAS NO WAY TO SEE INSIDE THE COWLING; AND THE FIRE BOTTLE MUST BE SHOT. THE CAPT FELT IT WAS A FALSE ALARM AND WOULD PUT THE AIRPLANE OUT OF COMMISSION MUCH LONGER THAN NECESSARY; WITH THE POSSIBILITY OF CORROSION TO THE ENG FROM THE RETARDANT. THE DEBATE CONTINUED FOR A TOTAL OF ABOUT 2 MINS. WE DID NOT FIRE THE BOTTLES. THE CAPT'S DECISION WAS BASED ON NOT ONLY A VISUAL CHK; BUT ALSO ENG INDICATIONS BEING NORMAL. BASED ON OUR COMPANY TRAINING; WE ARE REQUIRED TO COMPLY WITH THE CHKLIST; WHICH STATES: FEATHER THE ENG; SHUT OFF FUEL; AND DISCHARGE FIRE EXTINGUISHER. THROUGHOUT THE EMER I INSISTED WE FOLLOW THE CHKLIST. THE CAPT THEN WALKED TO THE CABIN OF THE ACFT; TO SEE IF HE COULD VISUALLY SEE A FIRE. FROM THE BACK; IT IS NOT POSSIBLE TO SEE OUT; BECAUSE ALL OF THE WINDOWS HAVE BEEN COVERED. WHILE HE WAS IN THE BACK; I YELLED TO HIM; ASKING FOR A MESSAGE TO GIVE ATC. HE SAID 'TELL THEM WE DID A PRECAUTIONARY SHUTDOWN.' I TOLD HIM WE NEEDED TO DECLARE AN EMER; HE THEN AGREED. WITH THE INFO PASSED TO ATC; THE CAPT ASKED IF I WANTED TO CONTINUE TO SBA (10 MINS AWAY). I SAID 'NO; NOT WITH THAT LIGHT STILL ON. I REALIZE WE'RE HOLDING ALT; BUT HOW DO WE EXPLAIN FLYING ALL THE WAY OVER WATER?' (FROM CAMARILLO THE APCH INTO SBA IS OUT OVER THE OCEAN.) THE CAPT INFORMED ME THAT CMA ARPT WAS DIRECTLY BELOW US AND WE COULD LAND THERE; HE WAS NOW FLYING AND I CALLED SOCAL AND REQUESTED LNDG AT CMA. WHEN HANDED OVER TO CMA TWR THE CTLR ASKED IF WE WANTED THE TRUCKS. WE ASKED FOR A FIRE TRUCK. THE CAPT MADE A BEAUTIFUL SINGLE ENG LNDG. WE ROLLED OUT AND AVOIDED INITIALLY USING THE REVERSERS. WE ASKED FOR PERMISSION TO SHUT DOWN ON THE TXWY. AS WE GOT OUT AND CHKED THE ENG; WHICH HAD NO EVIDENCE OF FIRE; I REALIZED I SHOULD HAVE TAKEN THE INITIATIVE TO INFORM ATC OF THE COMPLETE EMER STATUS BECAUSE IT TOOK THE TRUCKS 2- 3 MINS TO RESPOND. OUR MECH FOUND A FAULTY FIRE DETECTION LOOP. THAT WAS ALL.