Narrative:

Descending out of FL240, received clearance to cross imell intersection at 12000 ft MSL at 250 KTS. Altimeters below FL180 were approximately 29.46 for st louis area. I was PIC in left seat with sic flying our light transport with autoplt engaged (in transfer mode). I handled checklist on descent. Out of FL180, I called for altimeters to be reset to 29.46 inches (setting as close as I remembered) as per checklist. After level-off at 12000 ft, (autoplt automatically levels aircraft to selected altitude setting) and after passing imell intersection, we received heading assignment to approximately 230 degree with no speed restriction. A few mins later, the st louis approach controller mentioned to us that he really needed us to maintain 12000 ft for traffic. I then looked down at my pilot's altimeter and saw that we were actually at 11500 ft MSL with correct altimeter setting. Then looked at sic's altimeter setting and saw it was still set at 29.92 inches. Since autoplt was transferred, the aircraft leveled of 500 ft low. Initiated immediate climb to 12000 ft MSL and corrected sic's altimeter to correct setting. Inattn on both our parts for not assuring all altimeters resets was reason for altitude deviation. Strict review of checklist procedures will be undertaken.

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Original NASA ASRS Text

Title: FLC OF LTT CPR JET ACFT FAILED TO RESET THE PF'S ALTIMETER DURING DSCNT THROUGH FL180 RESULTING OVERSHOOTING LEVEL-OFF AT A XING ALT.

Narrative: DSNDING OUT OF FL240, RECEIVED CLRNC TO CROSS IMELL INTXN AT 12000 FT MSL AT 250 KTS. ALTIMETERS BELOW FL180 WERE APPROX 29.46 FOR ST LOUIS AREA. I WAS PIC IN L SEAT WITH SIC FLYING OUR LTT WITH AUTOPLT ENGAGED (IN TRANSFER MODE). I HANDLED CHKLIST ON DSCNT. OUT OF FL180, I CALLED FOR ALTIMETERS TO BE RESET TO 29.46 INCHES (SETTING AS CLOSE AS I REMEMBERED) AS PER CHKLIST. AFTER LEVEL-OFF AT 12000 FT, (AUTOPLT AUTOMATICALLY LEVELS ACFT TO SELECTED ALT SETTING) AND AFTER PASSING IMELL INTXN, WE RECEIVED HDG ASSIGNMENT TO APPROX 230 DEG WITH NO SPD RESTRICTION. A FEW MINS LATER, THE ST LOUIS APCH CTLR MENTIONED TO US THAT HE REALLY NEEDED US TO MAINTAIN 12000 FT FOR TFC. I THEN LOOKED DOWN AT MY PLT'S ALTIMETER AND SAW THAT WE WERE ACTUALLY AT 11500 FT MSL WITH CORRECT ALTIMETER SETTING. THEN LOOKED AT SIC'S ALTIMETER SETTING AND SAW IT WAS STILL SET AT 29.92 INCHES. SINCE AUTOPLT WAS TRANSFERRED, THE ACFT LEVELED OF 500 FT LOW. INITIATED IMMEDIATE CLB TO 12000 FT MSL AND CORRECTED SIC'S ALTIMETER TO CORRECT SETTING. INATTN ON BOTH OUR PARTS FOR NOT ASSURING ALL ALTIMETERS RESETS WAS REASON FOR ALT DEV. STRICT REVIEW OF CHKLIST PROCS WILL BE UNDERTAKEN.

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.