SPD RESTR NOT MET.

Narrative

WHILE ENRTE INTO PHX WE WERE CLRED DIRECT TONTO INTXN TO CROSS AT 12000 FT AND 250 KTS. WE WERE INSTRUCTED TO MAINTAIN 300 KTS WHEN ABLE IN THE DSCNT. OUR ACFT WAS EQUIPPED WITH FMC (FLT MGMNT COMPUTER WITH VNAV) AND WAS PROGRAMMED FOR THE APPROPRIATE SPD AND ALT XING CLRNC. ON THE DSCNT I MENTIONED TO THE CAPT THAT THE ACFT WAS NOT HOLDING (THE ASSIGNED) SPD VERY WELL. HE AGREED; BUT MADE NO ATTEMPT TO REGULATE THE SPD WITH SPD BRAKES. THE WINDS DURING THE DSCNT HAD SHIFTED CAUSING THE ACFT TO GET HIGH COMPARED TO THE PROFILE CALCULATED BY THE FMC. AFTER QUESTIONING THE CAPT AGAIN; THIS TIME TO SEE IF WE WOULD MAKE THE RESTR AT 'TONTO' HE INDICATED IT WOULD BE OK. HE STILL DID NOT USE SPD BRAKES UNTIL JUST PRIOR TO TONTO. WHILE ALL ALT INSTRUCTIONS WERE COMPLIED WITH; WE CROSSED TONTO IN EXCESS OF THE ORIGINAL ASSIGNED SPD RESTR (AT TONTO). (THE CAPT INDICATED HE HAD UNDERSTOOD A LATER CLRNC TO VOID THE SPD RESTR; BUT THIS WAS NOT MY UNDERSTANDING.) THE ACFT SOON REACHED THE APPROPRIATE SPD AND THE FLT CONCLUDED WITH NO KNOWN CONFLICTS. MAKING SURE BOTH PLTS UNDERSTAND ALL CLRNCS IS A MUST. ANY DOUBT MUST BE RESOLVED IMMEDIATELY. ALSO WHEN PROGRAMMING AN FMC FOR A DSCNT INTO A HEADWIND AN ALLOWANCE FOR A WIND SHIFT WOULD PROVIDE A MORE CONSERVATIVE DSCNT PROFILE.