FLC OF GULFSTREAM IV SETS THE HDG MODE TOO EARLY WHILE TAXIING IN OPPOSITE DIRECTION FROM DEP AND ACFT TURNS THE WRONG DIRECTION AFTER TKOF. ATC QUERIES FLC AND GIVES THEM AN AMENDED CLRNC.

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FO (PF) BRIEFED THE IFR DEP AS R TURN TO 270 DEGS AND 5000 FT. WHILE TAXIING TO RWY 15 (ON PARALLEL HDG 320 DEGS) HE SELECTED HDG MODE ON DISPLAY CONTROLLER AND PUT IN 270 DEGS. AFTER TKOF ON RWY 15; I (PNF) ON COMMAND GOT THE GEAR AND FLAPS UP AND SWITCHED TO BWI DEP CTL. THE MIN I CONTACTED THE CTLR HE ASKED IF WE WERE CLRED A R OR L TURN TO 270 DEGS. I SAID R; HOWEVER; WE WERE IN A L TURN. THE CTLR SAID CONTINUE THE L TURN TO 270 DEGS. I ASKED THE FO WHY HE TURNED L INSTEAD OF R AND HE SAID HE WAS FOLLOWING THE COMMAND STEERING BARS. I BELIEVE WHEN HE SELECTED HDG AND 270 DEGS WHILE THE ACFT WAS ON THE PARALLEL TXWY IT LOCKED IN A L TURN (CLOSEST DIRECTION FROM HDG 320 DEGS) AND WHEN WE TOOK THE RWY; EVEN THOUGH WE WERE HDG 150 DEGS FOR TKOF; THE L TURN COMMAND WAS PROGRAMMED INTO THE FLT DIRECTOR SYS. AFTER ARRIVING AT OUR DEST; I TALKED TO BOTH TWR AND DEP CTL SUPVRS AND THEY SAID THERE WAS NO CONFLICT WITH OTHER TFC. I HAVE A CALL INTO HONEYWELL (FMS; FLT DIRECTOR MANUFACTURER) TO SEE IF THAT WAS THE PROB. I ALSO HAVE NOTIFIED OUR COMPANY TO ADVISE OUR OTHER PLTS OF THIS PROB. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THAT HE HAS NOT HEARD BACK FROM HONEYWELL YET. HE WILL BE GOING TO SIMULATOR TRAINING NEXT WK AND WILL TEST HIS THEORY IN THE SIMULATOR. THE CHIEF PLT AND RPTR HAVE AGREED IN DISCUSSION THAT THE MOST LIKELY SCENARIO IS AS RPTR DESCRIBES IT. HIS NEW PROC IS TO INSTRUCT THE FO TO WAIT UNTIL THEY TURN ONTO THE RWY TO ACTUALLY SET THE DESIRED HDG. DON'T GET TOO FAR AHEAD. THE ACFT WAS A GULFSTREAM IV.