A CL65/200 REVERSER UNLOCK LIGHT ILLUMINATED IN FLT. QRH PROCEDURES DO NOT ADDRESS INDICATION ERROR. AN EMERGENCY WAS DECLARED WITH A DIVERSION AND LNDG.

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AFTER TAKEOFF WE GOT A L REVERSER UNLOCKED CAUTION MSG ALONG WITH A REV ICON ON OUR N1 GAUGE AND AN ILLUMINATED UNLOCKED LIGHT FOR OUR L THRUST REVERSER. THIS IS AN EMER PROC FOR THIS ACFT. THE ONLY THING WE DID NOT HAVE WAS ANY AIRFRAME BUFFETING INDICATING THAT THE THRUST REVERSER HAD ACTUALLY DEPLOYED. UNFORTUNATELY OUR EMER PROCS CHKLIST DOES NOT ADDRESS THIS SIT. THE CHKLIST ONLY PROVIDES GUIDANCE FOR AN ACTUAL DEPLOYMENT NOT AN INDICATION ERROR WHICH THIS WAS. IN THE INTEREST OF SAFETY I DECLARED AN EMER AND RETURNED TO THE ARPT WITHOUT INCIDENT. I REALIZE A CHKLIST CAN'T COVER EVERY SITUATION BUT A SITUATION THAT COULD LEAD TO A POSSIBLE THRUST REVERSER DEPLOYMENT IN FLT SHOULD HAVE A MORE EXPANDED PROC AVAILABLE TO THE FLT CREWS SO THEY ARE NOT PUT IN THE POSITION OF HAVING TO MAKE THE DECISION OF WHETHER THE PROB IS AN INDICATION ERROR OR COULD LEAD TO A MORE SERIOUS SITUATION. WE ARE OPERATORS NOT TECHNICIANS. I RELAYED MY CONCERNS TO MY CHIEF PLT AND AM HOPING THE EMER PROC WILL BE EXPANDED TO INCLUDE GUIDANCE ON POSSIBLE INDICATION ERRORS.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED THAT THE QRH IS INCOMPLETE BECAUSE IT DOES NOT FULLY DESCRIBE POSSIBLE REVERSER LIGHT ILLUMINATION CAUSES NOR DOES IT OFFER OPTIONS FOR THE CREW TO FOLLOW SHOULD AN INDICATION FAULT EXIST. THE REPORTER FELT THAT LACKING QRH GUIDANCE ON THE LIGHT'S CAUSE OR POSSIBLE RESPONSES HIS ONLY OPTION WAS TO GET THE ACFT ON THE GND. HAD HE CONTINUED IN FLT AND AN ACTUAL REVERSER DEPLOYMENT OCCURRED HE AS THE CAPT WAS IN JEOPARDY.