CL65 FLT CRW IS QUERIED BY ATC FOR APPARENTLY EARLY DESCENT PASSING DOEVR WAYPOINT ON THE PECHY RNAV STAR TO ATL.

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WE WERE GIVEN THE CLRNC TO 'DSND VIA' THE PECHY RNAV ARR. UPON BEING GIVEN THE CLRNC WE PROMPTLY BRIEFED THE ARR INCLUDING VERIFYING THAT THE CORRECT INFO WAS IN THE FMS. WE ALSO DISCUSSED HOW BEST TO EXECUTE THIS AS IT WAS MY FIRST TIME DOING THIS ARR WITH THE 'DSND VIA' CLRNC. I STARTED THE DSCNT OVER WHAT THE ACFT WAS TELLING US WAS THE DOEVR INTXN WHICH HAS A RESTR REQUIRING IT BE CROSSED AT 12000 FT AND 210 KTS. AS I STARTED THE DSCNT I NOTICED THAT IN ORDER TO MAKE THE FOLLOWING RESTRS AT THE ASSIGNED SPDS PER ATC; I HAD TO DIAL IN A VERY RAPID RATE OF DSCNT; WHICH I PROMPTLY DID. DSNDING OUT OF 10700 FT APCH QUERIED OUR ALT SAYING HE SHOWED THAT WE SHOULD STILL BE AT 12000 FT. WE TOLD HIM WE HAD ALREADY CROSSED THE WAYPOINT. NOTHING FURTHER WAS SAID ABOUT THIS; HOWEVER THE FREQ WAS EXTREMELY BUSY AS THERE WERE MULTIPLE ACFT CHKING IN; SPD CHANGES BEING GIVEN DIFFERENT FROM THE ARR INSTRUCTIONS; AND HDOFS TO THE NEXT FREQ WITH THE ADVISORY TO EXPECT A SHORT APCH. I BELIEVE THERE WERE A SERIES OF EVENTS THAT LED TO THE MISUNDERSTANDING. THE FIRST BEING THAT THIS WAS MY FIRST TIME TO EXECUTE THE 'DSND VIA' ARR AND UNDERSTANDING WHAT THE BEST WAY TO SET UP THE AUTOMATION TO GIVE ME THE APPROPRIATE GUIDANCE WOULD BE. SECONDLY; AS WE WERE BRIEFING THE ARR WE WERE GIVEN ALTERNATE SPD INSTRUCTIONS DIFFERENT FROM THE 'DSND VIA' CLRNC ADDING TO THE CONFUSION AND WORKLOAD. THIRDLY; OUR ACFT TREATS THE INTXNS AS 'FLY-BY' WAYPOINTS MEANING THAT IT DOES NOT FLY DIRECTLY OVER THE WAYPOINT BEFORE TURNING TO THE NEXT COURSE (IT LEADS THE TURN). BY DOING THIS IT LOOKS LIKE (ON THE FMS DISTANCE) THE ACFT HAS ALREADY PASSED THE INTXN WHEN INDEED ON A RADAR SCOPE IT HAS NOT; BUT IS MERELY FLYING BY IT. WHEN ADDING THIS TO THE STEEP VERT DSCNT SPD THAT I DIALED IN; THE INFO THE CTLR SAW WAS DIFFERENT FROM WHAT WE SAW. SINCE THIS EVENT; I HAVE ALLOWED THE ACFT TO FINISH THE TURN AND BECOME COMPLETELY ESTABLISHED ON THE NEW COURSE BEFORE DIALING IN THE DSCNT.