Narrative:

Flying ILS runway 28L, GS inoperative at sfo. WX was 400 ft broken and 2 mi visibility. Bay approach kept us high at 7000 ft. They finally cleared us for the approach and we crossed ramnd approximately 5000 ft. When crossing ramnd I set 1800 ft in the altitude alert. Just prior to leveling at 1800 ft the localizer began jumping around +/-1 DOT. The autoplt was on and the flight directors deflected full scale both directions. The autoplt rolled into a 30 degree bank so the captain disconnected the autoplt. As the 1800 ft altitude constraint went under the nose I called brijj and we began a 1200 FPM descent. Brijj NDB had been tuned but we never received a signal. Just outside brijj we realized we had descended too early and began a climb until brijj. We then continued the approach and landed. I believe there were a number of factors involved in this incident. First, we're chicago based and it was early am body time and fatigue was definitely a factor. The second was being kept high on the approach initially. Also menlo and bridge are idented on our display as CF28L and FF28L instead of their respective names and the 1800 ft altitude constraint is at CF28L (menlo). The autoplt rolling 30 degrees in both directions for a localizer deviation of less than 1 DOT was a distraction that I believe led us to begin the early descent as the 1800 ft altitude constraint went by (fixed on the rolling aircraft and missed DME xchk). The fact that we never received brijj (sf) LOM also was a factor. I believe this is a classic case of a number of factors coming together in a critical phase of flight, a distraction (the aircraft rolling into a 30 degree bank turn), and fatigue resulting in the crew becoming monetarily fixated leading to a large mistake. Supplemental information from acn 466475: approach control did not clear us out 7000 ft until approximately 14 mi. We crossed ramnd intersection at approximately 5000 ft and set 1800 ft for brijj. The navigation display for ILS runway 28L shows the 1800 ft constraint 5 mi from brijj and brijj is not depicted as brijj but 'ff.' being kept high, having the preceding aircraft cause the localizer to fluctuate and the constraint being before brijj and brijj not being depicted as brijj all combined to create a temporary loss of situational awareness.

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Original NASA ASRS Text

Title: AN A320 FLC STARTS AN EARLY DSCNT FROM 1800 FT ON A NIGHT LOC APCH TO SFO, CA.

Narrative: FLYING ILS RWY 28L, GS INOP AT SFO. WX WAS 400 FT BROKEN AND 2 MI VISIBILITY. BAY APCH KEPT US HIGH AT 7000 FT. THEY FINALLY CLRED US FOR THE APCH AND WE CROSSED RAMND APPROX 5000 FT. WHEN XING RAMND I SET 1800 FT IN THE ALT ALERT. JUST PRIOR TO LEVELING AT 1800 FT THE LOC BEGAN JUMPING AROUND +/-1 DOT. THE AUTOPLT WAS ON AND THE FLT DIRECTORS DEFLECTED FULL SCALE BOTH DIRECTIONS. THE AUTOPLT ROLLED INTO A 30 DEG BANK SO THE CAPT DISCONNECTED THE AUTOPLT. AS THE 1800 FT ALT CONSTRAINT WENT UNDER THE NOSE I CALLED BRIJJ AND WE BEGAN A 1200 FPM DSCNT. BRIJJ NDB HAD BEEN TUNED BUT WE NEVER RECEIVED A SIGNAL. JUST OUTSIDE BRIJJ WE REALIZED WE HAD DSNDED TOO EARLY AND BEGAN A CLB UNTIL BRIJJ. WE THEN CONTINUED THE APCH AND LANDED. I BELIEVE THERE WERE A NUMBER OF FACTORS INVOLVED IN THIS INCIDENT. FIRST, WE'RE CHICAGO BASED AND IT WAS EARLY AM BODY TIME AND FATIGUE WAS DEFINITELY A FACTOR. THE SECOND WAS BEING KEPT HIGH ON THE APCH INITIALLY. ALSO MENLO AND BRIDGE ARE IDENTED ON OUR DISPLAY AS CF28L AND FF28L INSTEAD OF THEIR RESPECTIVE NAMES AND THE 1800 FT ALT CONSTRAINT IS AT CF28L (MENLO). THE AUTOPLT ROLLING 30 DEGS IN BOTH DIRECTIONS FOR A LOC DEV OF LESS THAN 1 DOT WAS A DISTR THAT I BELIEVE LED US TO BEGIN THE EARLY DSCNT AS THE 1800 FT ALT CONSTRAINT WENT BY (FIXED ON THE ROLLING ACFT AND MISSED DME XCHK). THE FACT THAT WE NEVER RECEIVED BRIJJ (SF) LOM ALSO WAS A FACTOR. I BELIEVE THIS IS A CLASSIC CASE OF A NUMBER OF FACTORS COMING TOGETHER IN A CRITICAL PHASE OF FLT, A DISTR (THE ACFT ROLLING INTO A 30 DEG BANK TURN), AND FATIGUE RESULTING IN THE CREW BECOMING MONETARILY FIXATED LEADING TO A LARGE MISTAKE. SUPPLEMENTAL INFO FROM ACN 466475: APCH CTL DID NOT CLR US OUT 7000 FT UNTIL APPROX 14 MI. WE CROSSED RAMND INTXN AT APPROX 5000 FT AND SET 1800 FT FOR BRIJJ. THE NAV DISPLAY FOR ILS RWY 28L SHOWS THE 1800 FT CONSTRAINT 5 MI FROM BRIJJ AND BRIJJ IS NOT DEPICTED AS BRIJJ BUT 'FF.' BEING KEPT HIGH, HAVING THE PRECEDING ACFT CAUSE THE LOC TO FLUCTUATE AND THE CONSTRAINT BEING BEFORE BRIJJ AND BRIJJ NOT BEING DEPICTED AS BRIJJ ALL COMBINED TO CREATE A TEMPORARY LOSS OF SITUATIONAL AWARENESS.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.