FLC OF A DC9 FAILED TO MAINTAIN ASSIGNED SPD UNTIL CLRED FOR THE APCH AS REQUESTED BY ATC. EVEN THOUGH THE FLC WERE DISTRACTED WITH ANTI- AND DEICING PROBS; THE PF STILL NEEDS TO ASSURE THE ACFT COMPLIES WITH ATC INSTRUCTIONS!

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ENRTE TO PIT; CAPT FLYING THE ILS TO RWY 28R; WE WERE ASSIGNED A SPD OF 170 KTS. DURING THE APCH; WHILE STILL OUTSIDE THE OM OUR SPD SLOWED TO ABOUT 140 KTS; BECAUSE WE WERE DISTRACTED BY ERRONEOUS GS INDICATIONS ON THE CAPT'S ALT INDICATOR AS THE GS WAS BECOMING ACTIVE. CONTRIBUTING FACTORS: I HAD MMJ VOR TUNED IN NAV #2 FOR THE DME. WHEN THE CAPT NOTICED THE ERRONEOUS INDICATIONS; HE REQUESTED THAT I TUNE AND IDENT THE ILS RWY 28R ON NAV #2. WHILE TUNING AND IDENTING THE ACFT SLOWED. SECONDLY; THE ACFT SLOWED QUITE RAPIDLY BECAUSE WE WERE IN HVY ICING CONDITIONS. THIRDLY; WHILE ENRTE WE HAD HAD SEVERAL DISTRACTIONS; FROM HOLDING TO SEVERAL PROBS WITH THE ICE PROTECTION SYS; WE WERE ALSO HAVING A COMPANY LINE CHK. WE WERE ALSO KEPT HIGH ON BASE AND HAD A QUICK TURN TO FINAL AND NEEDED TO SLOW TO GET DOWN ON THE GS. I DON'T BELIEVE THAT OUR SLOWING DOWN CAUSED ATC ANY PROBS; BUT THEY DID INQUIRE. THE CHK PLT DOING THE LINE CHK MENTIONED TO US; AFTER THE FLT; THAT WHILE THEY DID GIVE US A SPD; THEY NEVER GAVE US A 'MAINTAIN 170 KTS UNTIL.'