AN A300 ON DSCNT INTO PHX EXCEEDS SPD LIMIT OVER TONTO INTXN. ACFT WAS ASSIGNED TO 250 KTS; BUT FLEW 280 KT AIRSPD. FLC DOESN'T SET UP FMS PROPERLY AND IS SLOW TO REACT WHEN ACFT SPD REMAINS HIGH.

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ON APCH TO PHX FROM ABQ ON THE FOSSL 3 ARR; WE WERE TO CROSS TONTO AT 12000 FT; 250 KTS. FMS WAS IN PROFILE DSCNT WITH A SPD TO MAINTAIN OF 300 KIAS IN THE DSCNT. THE FMS STARTED TO SLOW THE RATE OF DSCNT AT 13000 FT AND I PROGRAMMED THE FMS TO SLOW TO 250 KTS. I WAS LATE AND SLOW MAKING THE SPD CHANGE AND WE CROSSED TONTO AT 280 KTS. PHX APCH ASKED OUR SPD AND WE REPLIED WITH 280 KTS SLOWING TO 250 KTS. PHX ASKED OUR ACFT AND ANOTHER ACFT ABOUT SPD RESTR FOR DSCNT. WE GAVE THEM 300 KTS TO SLOW TO 250 KTS AT TONTO. THE OTHER ACFT DID THE SAME. SUPPLEMENTAL INFO FROM ACN 361620: AIRPLANE WAS AN AIRBUS 300 EQUIPPED WITH 3 IRS'S AND 2 FMS'S. ZAB ISSUED DSCNT CLRNC AND STIPULATED WE CROSS TONTO INTXN AT 12000 FT MSL AND 250 KTS. DURING THE DSCNT; THE FO ENTERED THE CONSTRAINTS INTO THE FMS AND THEN ACCESSED THE TACTICAL MODE AND INPUT 300 KTS FOR THE DSCNT AIRSPD. DSCNT PROCEEDED UNEVENTFULLY AND I BECAME DISTR WITH OTHER THINGS IN THE COCKPIT. AS WE LEVELED OFF AT 12000 FT MSL; I LOOKED UP AND NOTICED THAT WE WERE XING TONTO AT THE ASSIGNED ALT BUT AT AN AIRSPD OF 300 KTS. THE FO STATED THAT HE HAD BEEN TOO SLOW IN TAKING THE AIRPLANE OUT OF THE TACTICAL MODE IN ORDER TO ALLOW IT TO MEET THE ASSIGNED CONSTRAINTS.