Narrative:

Following a descent clearance from FL220, I began a descent to 10000 ft MSL to cross the grace intersection at 10000 ft/250 KTS. Our aircraft has 2 altimeter adjustment knobs and an EFIS push button (2) which gives a reading of 'standard' (or 29.92) or actual barometric setting in inches (e.g. 29.31). We completed the preliminary landing checklist just prior to 18000 MSL as recommended in the pilot's handbook. The first step on this checklist is 'altimeters' which both pilots reset to 29.31 inches on the rotary knob above the FMC computer. Neither of us switched the push buttons on the glare shield EFIS panels out of 'standard' (29.92) to local pressure qnh of 29.31 for reasons neither of us can ascertain. (I am new to the EFIS cockpit while my captain had flown it over a yr). In autoplt flight, the system was flying in reference to 29.92 and indicated 'standard' on the primary flight display while we were really flying in local pressure of 29.31. Right as we leveled off at 10000 ft indicated approaching the grace intersection, cleveland center radioed to confirm our altitude readout. We both caught our 600 ft error and quickly got back to 10000 from 9500 ft true altitude. I feel the checklist should add a parenthesis with 'qnh/standard' immediately after the first step calling for altimeter setting, since pilots new to EFIS cockpits are used to setting altimeters in only 1 location, on the altimeter itself. During sim training, we didn't cross FL180 enough times for this system design to really sink in as to potential altitude errors in human operation.

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Original NASA ASRS Text

Title: WRONG ALT SETTING CREATES AN ALT DEV ALT OVERSHOT IN DSCNT.

Narrative: FOLLOWING A DSCNT CLRNC FROM FL220, I BEGAN A DSCNT TO 10000 FT MSL TO CROSS THE GRACE INTXN AT 10000 FT/250 KTS. OUR ACFT HAS 2 ALTIMETER ADJUSTMENT KNOBS AND AN EFIS PUSH BUTTON (2) WHICH GIVES A READING OF 'STD' (OR 29.92) OR ACTUAL BAROMETRIC SETTING IN INCHES (E.G. 29.31). WE COMPLETED THE PRELIMINARY LNDG CHKLIST JUST PRIOR TO 18000 MSL AS RECOMMENDED IN THE PLT'S HANDBOOK. THE FIRST STEP ON THIS CHKLIST IS 'ALTIMETERS' WHICH BOTH PLTS RESET TO 29.31 INCHES ON THE ROTARY KNOB ABOVE THE FMC COMPUTER. NEITHER OF US SWITCHED THE PUSH BUTTONS ON THE GLARE SHIELD EFIS PANELS OUT OF 'STD' (29.92) TO LCL PRESSURE QNH OF 29.31 FOR REASONS NEITHER OF US CAN ASCERTAIN. (I AM NEW TO THE EFIS COCKPIT WHILE MY CAPT HAD FLOWN IT OVER A YR). IN AUTOPLT FLT, THE SYS WAS FLYING IN REF TO 29.92 AND INDICATED 'STD' ON THE PRIMARY FLT DISPLAY WHILE WE WERE REALLY FLYING IN LCL PRESSURE OF 29.31. RIGHT AS WE LEVELED OFF AT 10000 FT INDICATED APCHING THE GRACE INTXN, CLEVELAND CENTER RADIOED TO CONFIRM OUR ALT READOUT. WE BOTH CAUGHT OUR 600 FT ERROR AND QUICKLY GOT BACK TO 10000 FROM 9500 FT TRUE ALT. I FEEL THE CHKLIST SHOULD ADD A PARENTHESIS WITH 'QNH/STD' IMMEDIATELY AFTER THE FIRST STEP CALLING FOR ALTIMETER SETTING, SINCE PLTS NEW TO EFIS COCKPITS ARE USED TO SETTING ALTIMETERS IN ONLY 1 LOCATION, ON THE ALTIMETER ITSELF. DURING SIM TRAINING, WE DIDN'T CROSS FL180 ENOUGH TIMES FOR THIS SYS DESIGN TO REALLY SINK IN AS TO POTENTIAL ALT ERRORS IN HUMAN OP.

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.