A CL65 FLT CREW INADVERTENTLY MISPROGRAMMED THE FMS RESULTING IN FLYING OFF COURSE UNTIL ZTL ADVISED.

Narrative

OUR FLT WAS CLRED DIRECT TIROE INTXN; THEN VIA THE LA GRANGE ONE ARR TO ATLANTA (ATL) ARPT. WE WERE GIVEN A CLRNC TO CROSS TIROE INTXN AT 14000 FT. I ENTERED THIS XING RESTR INTO THE FMS LEGS PAGE BY TYPING '14000' INTO THE SCRATCH PAD AND PRESSING THE CORRESPONDING LINE SELECT BUTTON; 'R2.' THIS SET THE FMS TO CROSS TIROE AT 14000 FT. I THEN CONFIRMED AND EXECUTED THE CHANGE IN THE FLT PLAN. UNREALIZED BY US AT THE TIME; I MUST HAVE ALSO ACCIDENTALLY PRESSED THE 'R1' LINE SELECT BUTTON CAUSING THE WAYPOINT AUTO-SEQUENCE FUNCTION TO SWITCH FROM SEQUENCE AUTO TO SEQUENCE INHIBIT. THIS ERROR CAUSED THE AIRPLANE TO CONTINUE ON A STRAIGHT COURSE AFTER PASSING TIROE INTXN RATHER THAN TURNING NE ON COURSE TO THE ATL VOR. THE ACFT WAS SEVERAL MI N OF THE TURN POINT WHEN THE CTLR ASKED US TO 'SAY HEADING.' AT THIS POINT; I SAW THAT THE AUTOPLT WAS STILL NAVING OFF THE FMS ON A NORTHERLY COURSE WITH TIROE INTXN BEHIND US. IT TOOK ME SEVERAL SECONDS TO FIGURE OUT WHY THE FMS DID NOT SEQUENCE TO THE ATL VOR. IN THE MEANTIME; THE CTLR ADVISED US THAT WE WERE 7 MI N OFF COURSE AND HE CLRED US DIRECT TO THE ATL VOR. THE FLT LANDED NORMALLY SEVERAL MINS LATER. I FEEL THAT THERE WERE SEVERAL HUMAN AND TECHNOLOGY FACTORS THAT CONTRIBUTED TO THIS COURSE DEV. AFTER I ENTERED THE XING RESTR INTO THE FMS; I WENT OFF FREQ TO MAKE OUR 'IN-RANGE' CALL TO COMPANY. THEN; AS WE CROSSED THE TIROE INTXN; I WAS REVIEWING THE ILS RWY 27L APCH PLATE IN PREPARATION FOR LNDG. EVEN IF I WAS NOT PERFORMING THESE OTHER TASKS; I AM NOT SURE THAT I WOULD HAVE NOTICED THAT THE FMS WAS TAKEN OUT OF AUTO-SEQUENCE UNTIL AFTER PASSING TIROE INTXN. MY REASONS ARE AS FOLLOWS: 1) THERE WAS NO INDICATION ON EITHER PLTS PRIMARY FLT DISPLAY (PFD) OR MULTIFUNCTION DISPLAY (MFD) PRIOR TO TIROE INTXN THAT SEQUENCE INHIBIT WAS SELECTED IN THE FMS. 2) THE ONLY PLACE TO VIEW THE AUTO-SEQUENCE STATUS OF THE FMS IS THE LEGS PAGE. ALL OTHER CHANGES MADE IN THE FMC THAT CAN ALTER THE COURSE OR RTE OF THE FLT MUST BE FOLLOWED BY SOME SORT OF CONFIRMATION. USUALLY; THIS INVOLVES PRESSING THE EXECUTE 'EXEC' BUTTON. THIS EXTRA STEP ALLOWS CREWS TO VERIFY EVERY RTE CHANGE. I WOULD RECOMMEND THAT FUTURE FMS SOFTWARE CHANGES INCORPORATE A CONFIRMATION SEQUENCE SIMILAR TO PRESSING THE 'EXEC' BUTTON TO THE SEQUENCE-AUTO/INHIBIT FUNCTION. AT THE VERY LEAST; THIS FUNCTION SHOULD BE PLACED IN A SUBMENU; NOT ON THE LEGS PAGE WHERE THE WAYPOINT SEQUENCE CAN BE INHIBITED BY ONE PRESS OF THE 'R1' LINE SELECT BUTTON.