Narrative:

Approaching anc from the east, flight was given a descent from FL350 to 10000 ft at pilot's discretion. An incorrect altimeter setting was set (30.??) in the captain's standby altimeter. First officer then copied ATIS which had the correct setting. First officer mentioned that the settings were wrong and asked ATC for the setting again in the descent, the crew set 30.45 instead of 29.45. Flight was given lower altitude assignments with a final assignment of 1600 ft. The flight never reached any of these intermediate altitudes prior to the next assignment. Flight was descending at approximately 500 FPM passing 2100-2200 ft on aircraft barometric altimeter when approach control told flight to 'climb immediately to 1600 ft, minimum vectoring altitude.' a climb was immediately accomplished and while in the climb the proper setting was received and set. An altitude deviation of 500 ft below assigned altitude resulted and could have been greater had it not been for approach control's quick and outstanding performance. Terrain was not a factor this night. Vectors had the aircraft over water. Moonlight aided pilots in keeping land versus water in sight. Due to mechanical problems and delays aircrew fell behind schedule entire day, allowing no breaks. 4 legs were flown resulting in a 12 hour crew day with 7 1/2 hours of flight time. Landing at anc was at XA30 crew's domicile time on day #2 of a 4 day trip. Previous day was a 12 hour plus crew day with 7 hour 45 min flight time. Operations had been in high pressure area all day. Altimeter settings had been 30XX. When I noticed the different settings, I fixated on the last 2 numbers. A 30.45 setting fit my model and I perceived it to be reasonable. Although crew fatigue and error perceptions might have played a factor, attention to detail was a major culprit. All our terrain and approach briefings were useless without a proper altimeter setting. We should have been more attentive to details while these fatiguing factors were present. There is no doubt that this flight would have landed safely even without the detection of this mistake. This knowledge is little comfort, because I never thought I could make a mistake of this nature.

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Original NASA ASRS Text

Title: DURING DSCNT FLC SET ALTIMETER TO WRONG SETTING, 30 PT 45 VERSUS 29 PT 45, RESULTING IN A LEVELOFF ALT 500 FT TOO LOW. CLRNC WAS TO 1600 FT AND AN ALERT APCH CTLR NOTED ACFT DSNDING BELOW 1600 FT, INTERVENED FOR ACFT TO CLB. THEN, FLC RESET ALTIMETER CORRECTLY.

Narrative: APCHING ANC FROM THE E, FLT WAS GIVEN A DSCNT FROM FL350 TO 10000 FT AT PLT'S DISCRETION. AN INCORRECT ALTIMETER SETTING WAS SET (30.??) IN THE CAPT'S STANDBY ALTIMETER. FO THEN COPIED ATIS WHICH HAD THE CORRECT SETTING. FO MENTIONED THAT THE SETTINGS WERE WRONG AND ASKED ATC FOR THE SETTING AGAIN IN THE DSCNT, THE CREW SET 30.45 INSTEAD OF 29.45. FLT WAS GIVEN LOWER ALT ASSIGNMENTS WITH A FINAL ASSIGNMENT OF 1600 FT. THE FLT NEVER REACHED ANY OF THESE INTERMEDIATE ALTS PRIOR TO THE NEXT ASSIGNMENT. FLT WAS DSNDING AT APPROX 500 FPM PASSING 2100-2200 FT ON ACFT BAROMETRIC ALTIMETER WHEN APCH CTL TOLD FLT TO 'CLB IMMEDIATELY TO 1600 FT, MINIMUM VECTORING ALT.' A CLB WAS IMMEDIATELY ACCOMPLISHED AND WHILE IN THE CLB THE PROPER SETTING WAS RECEIVED AND SET. AN ALTDEV OF 500 FT BELOW ASSIGNED ALT RESULTED AND COULD HAVE BEEN GREATER HAD IT NOT BEEN FOR APCH CTL'S QUICK AND OUTSTANDING PERFORMANCE. TERRAIN WAS NOT A FACTOR THIS NIGHT. VECTORS HAD THE ACFT OVER WATER. MOONLIGHT AIDED PLTS IN KEEPING LAND VERSUS WATER IN SIGHT. DUE TO MECHANICAL PROBS AND DELAYS AIRCREW FELL BEHIND SCHEDULE ENTIRE DAY, ALLOWING NO BREAKS. 4 LEGS WERE FLOWN RESULTING IN A 12 HR CREW DAY WITH 7 1/2 HRS OF FLT TIME. LNDG AT ANC WAS AT XA30 CREW'S DOMICILE TIME ON DAY #2 OF A 4 DAY TRIP. PREVIOUS DAY WAS A 12 HR PLUS CREW DAY WITH 7 HR 45 MIN FLT TIME. OPS HAD BEEN IN HIGH PRESSURE AREA ALL DAY. ALTIMETER SETTINGS HAD BEEN 30XX. WHEN I NOTICED THE DIFFERENT SETTINGS, I FIXATED ON THE LAST 2 NUMBERS. A 30.45 SETTING FIT MY MODEL AND I PERCEIVED IT TO BE REASONABLE. ALTHOUGH CREW FATIGUE AND ERROR PERCEPTIONS MIGHT HAVE PLAYED A FACTOR, ATTN TO DETAIL WAS A MAJOR CULPRIT. ALL OUR TERRAIN AND APCH BRIEFINGS WERE USELESS WITHOUT A PROPER ALTIMETER SETTING. WE SHOULD HAVE BEEN MORE ATTENTIVE TO DETAILS WHILE THESE FATIGUING FACTORS WERE PRESENT. THERE IS NO DOUBT THAT THIS FLT WOULD HAVE LANDED SAFELY EVEN WITHOUT THE DETECTION OF THIS MISTAKE. THIS KNOWLEDGE IS LITTLE COMFORT, BECAUSE I NEVER THOUGHT I COULD MAKE A MISTAKE OF THIS NATURE.

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.