A320 FLC DEVIATE FROM ASSIGNED ROUTING BECAUSE OF A320 FMCS FLT CHARACTERISTICS AND ARE INVOLVED IN A PLTDEV.

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WE WERE APPROX 40 MI W OF IGN. WE WERE CLRED BY ZBW DIRECT LOLLY; AS FILED (IGN.6) THEN AT 20 MI W OF LOLLY; WE WERE CLRED TO CROSS LOLLY AT FL200. ABOUT 6 MI W OF LOLLY WE WERE AT FL200 AND THE ACFT (FMGC) STARTED A TURN TOWARDS THE NEXT FIX (DOORE). ZNY THEN ASKED US WHERE WE WERE GOING; 'ACFT X ARE YOU DIRECT LENDY;' TO WHICH WE INFORMED HIM AS TO OUR PREVIOUS CLRNC. WE DID HAVE VISUAL ON THE CONFLICTING TFC BUT THAT TFC WAS NEVER CALLED BY ATC. SUPPLEMENTAL INFO FROM ACN 514298: THE A320 FMGS WILL NEVER CROSS THE EXACT POINT IN SPACE IF THERE IS A SIGNIFICANT HEADING CHANGE. WE RECEIVED A TCASII TA WITH AN ACFT CLBING. ZNY QUERIED US ABOUT OUR FLT ROUTING. THEY WERE UNDER THE IMPRESSION WE WERE CLRED DIRECT LENDY AFTER LOLLY. AFTER LNDG; I TALKED WITH THE SHIFT SUPVR. HE TOLD ME HE REMEMBERED THE A320'S TURN CHARACTERISTICS AT HIGH ALT. OUR FOM ENCOURAGES US TO USE THE FULL CAPABILITIES OF THE FMGS. THERE SEEMS TO BE A CONFLICT WITH THAT PHILOSOPHY AND ATC PROCS. AS THE PIC; I WAS INFORMED THERE WAS A POSSIBLE PLTDEV; SINCE SEPARATION WAS LESS THAN 5 MI.