B737 CREW HAD AN ALT OVERSHOT ON APCH TO RWY 35L AT DEN.

Narrative

THE CAPT WAS FLYING THE ILS APCH TO RWY 35L DEN. THE CTLR GAVE US A HDG OF 320 DEGS TO INTERCEPT THE RWY 35L LOC AND TO DSND TO 8000 FT. WE PROCEEDED WITH THIS CLRNC AND THEN RECEIVED A FURTHER CLRNC TO 'MAINTAIN 8000 FT UNTIL ESTABLISHED; CLRED FOR THE ILS RWY 35L APCH.' OUR INTERCEPT OF THE LOC PUT US BTWN CHOLA INTL (16.6 DME) AND DYMON INTL (6.8 DME); WITH AN APCH ALT OF 9000 FT (7000 FT WHEN AUTH BY ATC) FOR THE ILS. THE GS OTS APCH; ON THE PROFILE VIEW; GIVES A SECTOR APCH ALT OF 7000 FT. AFTER RECEIVING THE ILS CLRNC; AND AS WE APCHED THE FINAL APCH COURSE; I WENT TO THE HSI TO MONITOR THE LOC ALIVE. AS I DID THIS; I NOTED OUR DSCNT THROUGH 8500 FT FOR 8000 FT. THE LOC CAME ALIVE AND CAPTURED; WHICH I CALLED OUT AND MONITORED. WHEN THIS WAS DONE; I LOOKED UP TO SEE THE ACFT WAS DSNDING THROUGH 7600 FT FOR 7000 FT AT APPROX 1800 FPM. THE CAPT; WITHOUT INFORMING ME OR CONFIRMING THE SECTOR ALT WAS CORRECT HAD PUT IN A NEW ALT OF 7000 FT AS WE ESTABLISHED INBOUND. HE MISREAD THE APCH PLATE AND PUT IN THE SECTOR ALT FOR THE LOC/GS OTS APCH; NOT THE ILS; WHICH WAS THE APCH WE HAD BEEN CLRED FOR. THE CORRECT SECTOR ALT TO MAINTAIN UNTIL GS INTERCEPT WAS 8000 FT; WHICH WAS THE ALT AUTH BY THE ATC APCH CTLR. AT 7000 FT AND GS INTERCEPT; THE APCH CTLR ASKED IF WE HAD THE ARPT VISUALLY WHEN WE CAME OUT OF 8000 FT. WE ANSWERED 'AFFIRMATIVE' AND CONTINUED THE APCH WITHOUT FURTHER INCIDENT. THE CAPT SHOULD HAVE BRIEFED THAT HE WOULD FOLLOW STEP DOWN FIXES WHEN CLRED FOR THE APCH. HE ALSO SHOULD HAVE BRIEFED THE APPROPRIATE SECTOR ALTS BTWN THOSE FIXES. WHEN HE CHANGED THE ALT IN THE MCP; HE SHOULD HAVE INFORMED ME; AND HAD ME CONFIRM THE ALT WAS CORRECT. HAD HE DONE THIS; WE WOULD NOT HAVE BUSTED OUR ALT BY 1000 FT.