FMS TURNED ACFT 6 MI BEFORE FIX ON RTE WITH GREATER THAN 90 DEG TURN. ARTCC DIDN'T LIKE EARLY TURN AND RECLRED OVER THE FIX.

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OUR CLRNC WAS DIRECT BRAVE INTXN; DIRECT UGN. WE WERE ON A N COURSE TO BRAVE INTXN AND UPON XING BRAVE INTXN WE WOULD TURN L AND TRACK SW TO UGN. IN A DSCNT AT OVER 400 KT GND SPD; THE FMS BEGAN A L TURN ABOUT 6 MI S OF BRAVE INTXN TO INTERCEPT THE COURSE AND PROCEED DIRECT TO UGN. WE DID NOT REALIZE THAT IT HAD TURNED THAT SOON UNTIL THE CTLR SAID 'WE WERE 6 MI S OF BRAVE INTXN AND TO TURN R TO 360 DEGS TO AVOID TFC.' I ACKNOWLEDGED THAT WE SHOWED PROCEEDING FROM BRAVE INTXN TO UGN. ON A FLT THAT AFTERNOON; WE WERE CLRED ON THE SAME RTE. ABOUT 6 MI S OF BRAVE INTXN; THE FMS BEGAN TO TURN THE ACFT TO THE SW. I WENT FROM 'NAV' TO 'HDG' ON THE AUTOPLT AND CONTINUED N A FEW MORE MI BEFORE TURNING TO THE SW. AS SOON AS THE FMS SHOWED US 6 MI S OF BRAVE INTXN; IT WENT FROM 'TO' BRAVE INTXN TO 'FROM' BRAVE INTXN. I MADE SEVERAL ATTEMPTS TO GO 'DIRECT' TO BRAVE INTXN WHEN LESS THAN 6 MI AND IT REPEATEDLY SHOWED 'FROM.' THE ONLY WAY TO GET CLOSER TO THE FIX WAS TO SELECT 'HDG' INSTEAD OF 'NAV.' I BELIEVE DUE TO THE ACFT'S HIGH GND SPD AND THE COURSE CHANGE FROM N TO SW; THE FMS BEGAN A TURN IN ADVANCE OF THE FIX IN ORDER TO INTERCEPT THE SW COURSE. IF THE FMS HAD GONE DIRECTLY TO THE FIX BEFORE MAKING THE TURN; WE WOULD PROBABLY HAVE BEEN 6 MI ON THE N SIDE OF THE COURSE. I BELIEVE THE MAJOR CONTRIBUTING FACTOR WAS THE LARGE COURSE CHANGE FROM N TO SW.