Narrative:

After passing modesto we were cleared heading 260 degrees to intercept sgd 107 degree radial while descending to 10000 ft MSL - passing through FL180 at the time. While I was tuning sdg VOR and setting my radios for 287 degrees inbound I missed setting my altimeter to sfo qnh of 29.48 hg. Although passing FL180 was called by the PF my fatigue level was great enough that I forgot to set the altimeter or misunderstood his FL180 call for my 287 degrees call for sgd inbound. When the approach checklist was read soon after passing FL180 - all 3 crewmembers missed the altimeter not being set to sfo qnh since 1) fatigue and 2) altimeters setting have been removed from approach checklist and put on before landing checklist done after passing through 10000 ft. The arrival ATC controller asked that we check our altimeter since we were indicating 9600 ft on his encoder. While we showed level 10000 ft with a setting of 29.92 - when we set 29.48 hg into our altimeter we showed the aircraft level at 9600 ft. We climbed to 10000 ft, landed without further problem. Factors affecting human performance. I was on reserve called at XA00 EST, had a 3 hour nap before a XB30 am show for a XC30 am report, and finally XD23 am departure: I was fatigued after 4 hours flight - primary problem - altimeter check not on checklist done after passing FL180 - only checked after 10000 ft per company checklist.

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Original NASA ASRS Text

Title: ALT/DEV ALT OVERSHOT IN DSCNT. WRONG ALTIMETER SETTING.

Narrative: AFTER PASSING MODESTO WE WERE CLRED HDG 260 DEGS TO INTERCEPT SGD 107 DEG RADIAL WHILE DSNDING TO 10000 FT MSL - PASSING THROUGH FL180 AT THE TIME. WHILE I WAS TUNING SDG VOR AND SETTING MY RADIOS FOR 287 DEGS INBOUND I MISSED SETTING MY ALTIMETER TO SFO QNH OF 29.48 HG. ALTHOUGH PASSING FL180 WAS CALLED BY THE PF MY FATIGUE LEVEL WAS GREAT ENOUGH THAT I FORGOT TO SET THE ALTIMETER OR MISUNDERSTOOD HIS FL180 CALL FOR MY 287 DEGS CALL FOR SGD INBOUND. WHEN THE APCH CHKLIST WAS READ SOON AFTER PASSING FL180 - ALL 3 CREWMEMBERS MISSED THE ALTIMETER NOT BEING SET TO SFO QNH SINCE 1) FATIGUE AND 2) ALTIMETERS SETTING HAVE BEEN REMOVED FROM APCH CHKLIST AND PUT ON BEFORE LNDG CHKLIST DONE AFTER PASSING THROUGH 10000 FT. THE ARR ATC CTLR ASKED THAT WE CHK OUR ALTIMETER SINCE WE WERE INDICATING 9600 FT ON HIS ENCODER. WHILE WE SHOWED LEVEL 10000 FT WITH A SETTING OF 29.92 - WHEN WE SET 29.48 HG INTO OUR ALTIMETER WE SHOWED THE ACFT LEVEL AT 9600 FT. WE CLBED TO 10000 FT, LANDED WITHOUT FURTHER PROB. FACTORS AFFECTING HUMAN PERFORMANCE. I WAS ON RESERVE CALLED AT XA00 EST, HAD A 3 HR NAP BEFORE A XB30 AM SHOW FOR A XC30 AM RPT, AND FINALLY XD23 AM DEP: I WAS FATIGUED AFTER 4 HRS FLT - PRIMARY PROB - ALTIMETER CHK NOT ON CHKLIST DONE AFTER PASSING FL180 - ONLY CHKED AFTER 10000 FT PER COMPANY CHKLIST.

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.