Narrative:

PNF was off ATC on company frequency. Aircraft was on autoplt. ATC cleared flight to descend to cross btg at FL240 and 250 KTS. Approaching btg while descending, PF had attention diverted to checking commercial navigation chart for outbnd right and questioning ATC about speed restriction. While attention was diverted, the automatic altitude capture became disarmed. (A recurring problem with this ships digital flight guidance system). The aircraft descended through FL240, PF noticed and began correction at 23800'. Aircraft descended to 23200' during recovery. The digital flight guidance system has small flight mode annunciators above the flight instruments. The altitude capture armed mode is indicated by a small 'altitude'. This is insufficient to the pilot who needs a larger, attention getting warning displayed, when 'altitude' does not illuminate. Supplemental information from acn 154652. Captain (PF) was on first regulation line trip on new aircraft, PNF (first officer) did not monitor aircraft adequately during important phase of flight (descent to cross). Took for granted that PF was capable, given background and training, but made error due to distraction and expectation of previous aircraft type flown performance.

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Original NASA ASRS Text

Title: ACR MLG FLT CREW OVERSHOOTS ASSIGNED ALT IN DESCENT.

Narrative: PNF WAS OFF ATC ON COMPANY FREQ. ACFT WAS ON AUTOPLT. ATC CLRED FLT TO DSND TO CROSS BTG AT FL240 AND 250 KTS. APCHING BTG WHILE DSNDING, PF HAD ATTN DIVERTED TO CHKING COMMERCIAL NAV CHART FOR OUTBND R AND QUESTIONING ATC ABOUT SPD RESTRICTION. WHILE ATTN WAS DIVERTED, THE AUTOMATIC ALT CAPTURE BECAME DISARMED. (A RECURRING PROB WITH THIS SHIPS DIGITAL FLT GUIDANCE SYS). THE ACFT DSNDED THROUGH FL240, PF NOTICED AND BEGAN CORRECTION AT 23800'. ACFT DSNDED TO 23200' DURING RECOVERY. THE DIGITAL FLT GUIDANCE SYS HAS SMALL FLT MODE ANNUNCIATORS ABOVE THE FLT INSTRUMENTS. THE ALT CAPTURE ARMED MODE IS INDICATED BY A SMALL 'ALT'. THIS IS INSUFFICIENT TO THE PLT WHO NEEDS A LARGER, ATTN GETTING WARNING DISPLAYED, WHEN 'ALT' DOES NOT ILLUMINATE. SUPPLEMENTAL INFO FROM ACN 154652. CAPT (PF) WAS ON FIRST REG LINE TRIP ON NEW ACFT, PNF (F/O) DID NOT MONITOR ACFT ADEQUATELY DURING IMPORTANT PHASE OF FLT (DSNT TO CROSS). TOOK FOR GRANTED THAT PF WAS CAPABLE, GIVEN BACKGROUND AND TRNING, BUT MADE ERROR DUE TO DISTR AND EXPECTATION OF PREVIOUS ACFT TYPE FLOWN PERFORMANCE.

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.