AFTER MISREADING TXWY SIGN; RPTR TAXIED WRONG WAY AND ALMOST ENTERED AN ACTIVE RWY.

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WE WERE DEPARTING THE RAMP; I HAD THE MEMPHIS TAXI CHART ON THE CTL WHEEL IN FRONT OF ME (WE ALWAYS USE TAXI CHARTS AT ARPTS WE ARE UNFAMILIAR WITH). WHILE WE WERE TAXIING ON THE RAMP AND THE COPLT WAS CALLING GND FOR TAXI INSTRUCTIONS; I SAW THE ABOVE MENTIONED SIGN DIRECTING ME TO WHAT I THOUGHT WAS RWY 18L. THIS CAUSED ME NOT TO LOOK AT THE TAXI CHART. WE RECEIVED A CLRNC TO TAXI TO RWY 18L. AS WE WERE TAXIING N ON TXWY C WE WERE ABOUT TO CROSS RWY 9/27 WHEN GND TOLD US TO MAKE A 180 DEG TURN TO GET TO RWY 18L. PRIOR TO TKOF THE TWR ASKED US TO CALL WHEN WE LANDED IN SAVANNAH. WHEN I CALLED THE TWR I SPOKE WITH A SUPVR AND FOUND OUT THEY HAD TO SEND A LEARJET AROUND BECAUSE THEY DID NOT KNOW IF I WAS GOING TO STOP OR NOT. I ALSO FOUND OUT THEY WERE GOING TO FILE A PLTDEV ON ME FOR THIS. HE INFORMED ME THAT THIS WAS NOT THE FIRST TIME THIS HAS HAPPENED. HE DID NOT KNOW WHAT THE SIGN SAID BUT THOUGHT IT SHOULD HAVE RWY 18L AND SOME TYPE OF AN ARROW THAT MIGHT POINT N THEN CURVE R TO THE EAST. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: RPTR ADMITTED HE WAS NOT LOOKING AT THE ARPT CHART WHICH HE HAD HANDY. HE WAS ON THE FBO RAMP AND HAD TO DO A 180 DEG TURN TO TAXI OUT TXWY C8 TO RWY 18L. INSTEAD; AS HE BEGAN HIS TURN OUT OF THE RAMP; HE SAW A SIGN THAT READ RWY '18L APCH' (HE THINKS). HE MISTOOK THE SIGN TO MEAN HE SHOULD CONTINUE N TO RWY 18L. HE ARGUES THAT HE DOES NOT KNOW WHAT ALL THE SIGNS MEAN AND NO PLT DOES.