Narrative:

This altitude deviation of 450' below assigned altitude of 12000' MSL occurred due to captain's altimeter still being set at 29.92. The aircraft was being flown by use of FMS, which leveled at 12000' on the captain's altimeter. Chain of events. Directed by cleveland ARTCC to descend to 11000'. Captain's duties were divided between maintaining flight path of the aircraft and reprogramming the FMS for optimum speeds and required altitude. First officer (myself) started silent items of descent checklist. Poor reception of roc ATIS on a VOR frequency resulted in ATIS reception approximately 50 mi closer to the airport than usual and well into the en route descent. First officer went off ARTCC radio to obtain ATIS. First officer resumed monitor of ARTCC frequency, accepted a frequency change, then acknowledged ARTCC directive to amend altitude clearance to 12000' due to traffic. Captain and first officer started discussing runway to be used at rochester due to poor WX and wet runways. First officer went to performance manual at captain's request to check landing distance. Descent checklist still not fully accomplished. This is real key. Had this checklist been completed at approximately 18000' MSL (normal airlines operation) both primary altimeters would have been properly set. Cleveland ARTCC controller called traffic. First officer acknowledged and advised controller of IMC conditions. Cleveland ARTCC queried us on altitude we were cleared to. This prompt made first officer aware of descent below assigned altitude (first officer's altimeter was set at 29.40; captain's still at 29.92). First officer informed captain of altimeter setting error. Captain immediately corrected the altimeter setting and actual aircraft altitude. Problem was detected at 11700'. Crew reaction time allowed the aircraft to read 11550'. Causes. Poor reception of ATIS on second frequency tried by first officer in poor WX. Rochester ATIS broadcast needs to be upgraded. Should be clearly available 100-150 mi from airport. Crew did not make the descend checklist a priority over approach selection. Both of us got a real world refresher course in setting priorities. Captain's concentration was divided between computer programming and flying the airplane. The button pushing required by an FMS is a big contributor to crew overload and poor situational awareness. Use of computerized navigation needs to be deemphasized in airline operations.

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Original NASA ASRS Text

Title: ALT OVERSHOT DURING DESCENT.

Narrative: THIS ALT DEV OF 450' BELOW ASSIGNED ALT OF 12000' MSL OCCURRED DUE TO CAPT'S ALTIMETER STILL BEING SET AT 29.92. THE ACFT WAS BEING FLOWN BY USE OF FMS, WHICH LEVELED AT 12000' ON THE CAPT'S ALTIMETER. CHAIN OF EVENTS. DIRECTED BY CLEVELAND ARTCC TO DSND TO 11000'. CAPT'S DUTIES WERE DIVIDED BTWN MAINTAINING FLT PATH OF THE ACFT AND REPROGRAMMING THE FMS FOR OPTIMUM SPDS AND REQUIRED ALT. F/O (MYSELF) STARTED SILENT ITEMS OF DSNT CHKLIST. POOR RECEPTION OF ROC ATIS ON A VOR FREQ RESULTED IN ATIS RECEPTION APPROX 50 MI CLOSER TO THE ARPT THAN USUAL AND WELL INTO THE ENRTE DSNT. F/O WENT OFF ARTCC RADIO TO OBTAIN ATIS. F/O RESUMED MONITOR OF ARTCC FREQ, ACCEPTED A FREQ CHANGE, THEN ACKNOWLEDGED ARTCC DIRECTIVE TO AMEND ALT CLRNC TO 12000' DUE TO TFC. CAPT AND F/O STARTED DISCUSSING RWY TO BE USED AT ROCHESTER DUE TO POOR WX AND WET RWYS. F/O WENT TO PERFORMANCE MANUAL AT CAPT'S REQUEST TO CHK LNDG DISTANCE. DSNT CHKLIST STILL NOT FULLY ACCOMPLISHED. THIS IS REAL KEY. HAD THIS CHKLIST BEEN COMPLETED AT APPROX 18000' MSL (NORMAL AIRLINES OPERATION) BOTH PRIMARY ALTIMETERS WOULD HAVE BEEN PROPERLY SET. CLEVELAND ARTCC CTLR CALLED TFC. F/O ACKNOWLEDGED AND ADVISED CTLR OF IMC CONDITIONS. CLEVELAND ARTCC QUERIED US ON ALT WE WERE CLRED TO. THIS PROMPT MADE F/O AWARE OF DSNT BELOW ASSIGNED ALT (F/O'S ALTIMETER WAS SET AT 29.40; CAPT'S STILL AT 29.92). F/O INFORMED CAPT OF ALTIMETER SETTING ERROR. CAPT IMMEDIATELY CORRECTED THE ALTIMETER SETTING AND ACTUAL ACFT ALT. PROB WAS DETECTED AT 11700'. CREW REACTION TIME ALLOWED THE ACFT TO READ 11550'. CAUSES. POOR RECEPTION OF ATIS ON SEC FREQ TRIED BY F/O IN POOR WX. ROCHESTER ATIS BROADCAST NEEDS TO BE UPGRADED. SHOULD BE CLRLY AVAILABLE 100-150 MI FROM ARPT. CREW DID NOT MAKE THE DSND CHKLIST A PRIORITY OVER APCH SELECTION. BOTH OF US GOT A REAL WORLD REFRESHER COURSE IN SETTING PRIORITIES. CAPT'S CONCENTRATION WAS DIVIDED BTWN COMPUTER PROGRAMMING AND FLYING THE AIRPLANE. THE BUTTON PUSHING REQUIRED BY AN FMS IS A BIG CONTRIBUTOR TO CREW OVERLOAD AND POOR SITUATIONAL AWARENESS. USE OF COMPUTERIZED NAV NEEDS TO BE DEEMPHASIZED IN AIRLINE OPS.

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.