CAPT STATED THAT DISTR FROM INOP EQUIP AND FLC RADIO RESPONSIBILITIES IN CRITICAL DSCNT PHASE; CONTRIBUTED TO ALT OVERSHOOT.

Narrative

IN THE DSCNT FROM THE W INTO IAD ON THE JASEN 1 STAR WE ENCOUNTERED HVY CUMULUS TYPE CLOUDS WITH PRECIPITATION AND MODERATE TURB DSNDING THROUGH FL290. ENG ANTI-ICE WAS ACTIVATED AND #4 ENG ANTI-ICE VALVE DID NOT OPEN. WE WERE FAIRLY FAST AND IT GOT VERY TURB. THE ACFT WAS ON AUTOPLT AND I WAS CTLING TRACK AND PITCH MANUALLY. WE WERE DSNDING TO FL270 WHEN THE SO ADVISED ME THE #4 EAI VALVE HAD NOT OPENED. I ADVANCED PWR ON #4 TO TRY TO OPEN IT. THIS DID NOT WORK I WAS NOT USING 'ALT SELECT' (CAPTURE) MODE BECAUSE THEY RECENTLY REPROGRAMMED THE COMPUTERS AND THEY PITCHED DOWN SHARPLY ON CAPTURE -- REGARDLESS OF DSCNT RATE. AT FL27.8 I STARTED ROLLING IN PITCH UP COMMANDS TO THE AUTOPLT AND IT WAS VERY SLOW IN CHANGING PITCH. THE ACFT OVERSHOT THE TARGET ALT OF FL270 AND WENT DOWN TO FL268. THE TCASII SYS GAVE AN ADVISORY TO CLB AS THERE WAS AN ACFT AT FL260. WE LEVELED AT FL270. I SHOULD NOT HAVE LET THE ENG ANTI-ICE VALVE DISTRACT ME IN THIS CRITICAL PHASE OF FLT. THE SO WAS BUSY TALKING TO COMPANY AND THE FO WAS TALKING TO CTR. TOO MUCH GOING ON AT 1 TIME. THE FO DID NOT MAKE HIS '1000 FT TO LEVEL OFF' CALL; BECAUSE HE WAS ON THE RADIO; AND WE ALL WERE DISTRACTED SETTING MINIMUM N1 RPM FOR ENG ANTI-ICE.