Air carrier medium large transport flight crew overshoots assigned altitude in descent.

Attributes
ACN	154418
Time
Date	199008
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : btg
State Reference	WA
Altitude	msl bound lower : 23200 msl bound upper : 24000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zse
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 30 flight time total : 6300 flight time type : 30
ASRS Report	154418
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : commercial
Experience	flight time last 90 days : 130 flight time total : 5500 flight time type : 130
ASRS Report	154652
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : overshoot non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course none taken : detected after the fact
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

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.

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.