MD90 CREW MISSES XING RESTR ON DSCNT IN ZLC AIRSPACE.

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CRUISING AT FL310; ENRTE FROM PHX-SLC; CLRNC ISSUED BY ATC FOR US TO CROSS 20 NM S OF FFU VOR AT 15000 FT. FO (PF) COMMENCED DSCNT 70 NM S OF NAVAID. SATISFIED BY WHERE DSCNT WAS INITIATED; I BEGAN REVIEWING MATERIAL FOR APCH AND LNDG. APPROX 4 MINS LATER; I CHKED THE STATUS OF OUR DSCNT AND SAW WE WERE NOW 20 NM FROM OUR XING RESTR; PASSING FL270; AND WE CLRLY WOULD NOT MAKE OUR RESTR. WE'D HAD A XWIND AT FL310 THAT HAD SWUNG AROUND TO BECOME A 60 KT TAILWIND; AND APPARENTLY THE FO HAD BEEN STUDYING APCH MATERIAL AT THE SAME TIME I WAS. HE'D STARTED DOWN WITH A 1000 FPM DSCNT RATE AND HAD NOT ADJUSTED IT. I IMMEDIATELY CALLED FOR SPD BRAKES UP AND MAX DSCNT RATE. MOMENTARILY; ATC ASKED US IF WE WOULD MAKE THE RESTR; AND I SAID PROBABLY NOT. CTLR SAID; GIVE IT OUR BEST RATE. AT THE XING RESTR WE WERE PASSING ABOUT 17500 FT; 2500 FT HIGH. NO LOSS OF SEPARATION WAS INDICATED BY ATC. LESSONS I LEARNED: 1) MAKE SURE DSCNT RATE IS ESTABLISHED TO MAKE RESTRS BEFORE SHIFTING ATTN TO OTHER DUTIES. 2) CLOSELY MONITOR ACFT PERFORMANCE EVERY FEW SECONDS; NOT EVERY FEW MINS; WHILE PERFORMING OTHER DUTIES.