ALTDEV ALT EXCURSION. NON ADHERENCE TO ATC CLRNC PROC. EARLY DSCNT PROC FROM APCH PROC STAR DSCNT.

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OPERATING AS ACR X FLT OAK-SEA WE HAD RECEIVED SOME DELAY VECTORS WHILE ON THE OLM ARR INTO SEA TO KEEP US FROM HAVING TO HOLD FOR METERING INTO SEA. WE WERE THEN RE- CLRED ON THE OLM 2 ARR TO DSND AS PUBLISHED. THE CAPT THEN DSNDED TO 12000 FT TO CROSS OLM VOR. THIS IS THE CORRECT ALT FOR NORTHERLY OPS BUT SEA WAS IN A SOUTHERLY OP. WE SHOULD HAVE CROSSED AT 16000 FT OVER OLM. I HAD JUST RETURNED TO THE CTR FREQ FROM GETTING A NEW ATIS FOR SEA. BEFORE I REALIZED IT; WE BEGAN A DSCNT AND WE BOTH REALIZED AFTER GOING THROUGH 14000 FT; SO WE JUST CONTINUED OUR DSCNT TO 12000 FT. IN HINDSIGHT I SHOULD HAVE FAMILIARIZED MYSELF WITH THE ARR IN MORE DETAIL BEFORE ALLOWING MY CAPT TO DSND WITHOUT BACKING HIM UP. THE ATIS CAN WAIT UNTIL WE ARE BOTH VERY FAMILIAR WITH AN ARR THAT CALLS FOR DSCNT AS PUBLISHED. SUPPLEMENTAL INFO FROM ACN 354088: I MISTAKENLY CALLED FOR 12000 FT IN ALT ALERT AS THAT WAS THE NUMBER THAT FIRST CAUGHT MY EYE. PROB AROSE DUE: CAPT HAVING NOT BEEN IN L SEAT RECENTLY; MANY VECTORS AND SPD CHANGES OFF THE STAR. NEW TERMINOLOGY 'DSND ON THE OLYMPIA ARR' LED ME TO THINK IT WAS TIME TO LEAVE 16000 FT (PREMATURE); VERY SMALL PRINT ON STAR (IN NIGHT ENVIRONMENT) I 'SAW' THE WRONG ALT.