DC10 descends below crossing altitude on STAR arrival procedure. Crew had noted the altitude capture on the FMA and then misdirected their attentions. So called out deviation.

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Attributes
ACN	390770
Time
Date	199801
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : sfo
State Reference	CA
Altitude	msl bound lower : 9500 msl bound upper : 10000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : oak
Operator	common carrier : air carrier
Make Model Name	DC-10 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent other
Route In Use	arrival other arrival star : star enroute other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
ASRS Report	390770
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : crossing restriction not met altitude deviation : overshoot non adherence : clearance non adherence : published procedure
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation other

Narrative:

Location: locke intersection. During descent into sfo on the locke one arrival, aircraft descended below assigned altitude. We were maintaining 11000 ft, 260 KTS, when ATC cleared us to cross locke intersection at 10000 ft/250 KTS. Captain initiated a normal descent. Approaching 10000 ft flight mode annunciator displayed altitude capture and pitch was being reduced. At this time I looked down at my chart for the sfo VOR frequency. While I tuned in sfo, the flight engineer called out 'altimeters' which he normally calls out below 10000 ft. A quick glance at the altimeters indicated 9600 ft and descending. Both the captain and myself immediately initiated recovery (autoplt disconnect power) advance. Aircraft reached 9500 ft prior to position rate of climb started. ATC queried us on our altitude about the time we were leveling 10000 ft. Our response was leveling 10000 ft. Nothing else was said. At no time did we get a warning from the altitude alert system. The autoplt had previous write-ups on it, but no placards were placed anywhere on autoplt control panel.

Original NASA ASRS Text

Title: DC10 DSNDS BELOW XING ALT ON STAR ARR PROC. CREW HAD NOTED THE ALT CAPTURE ON THE FMA AND THEN MISDIRECTED THEIR ATTENTIONS. SO CALLED OUT DEV.

Narrative: LOCATION: LOCKE INTXN. DURING DSCNT INTO SFO ON THE LOCKE ONE ARR, ACFT DSNDED BELOW ASSIGNED ALT. WE WERE MAINTAINING 11000 FT, 260 KTS, WHEN ATC CLRED US TO CROSS LOCKE INTXN AT 10000 FT/250 KTS. CAPT INITIATED A NORMAL DSCNT. APCHING 10000 FT FLT MODE ANNUNCIATOR DISPLAYED ALT CAPTURE AND PITCH WAS BEING REDUCED. AT THIS TIME I LOOKED DOWN AT MY CHART FOR THE SFO VOR FREQ. WHILE I TUNED IN SFO, THE FE CALLED OUT 'ALTIMETERS' WHICH HE NORMALLY CALLS OUT BELOW 10000 FT. A QUICK GLANCE AT THE ALTIMETERS INDICATED 9600 FT AND DSNDING. BOTH THE CAPT AND MYSELF IMMEDIATELY INITIATED RECOVERY (AUTOPLT DISCONNECT PWR) ADVANCE. ACFT REACHED 9500 FT PRIOR TO POS RATE OF CLB STARTED. ATC QUERIED US ON OUR ALT ABOUT THE TIME WE WERE LEVELING 10000 FT. OUR RESPONSE WAS LEVELING 10000 FT. NOTHING ELSE WAS SAID. AT NO TIME DID WE GET A WARNING FROM THE ALT ALERT SYS. THE AUTOPLT HAD PREVIOUS WRITE-UPS ON IT, BUT NO PLACARDS WERE PLACED ANYWHERE ON AUTOPLT CTL PANEL.

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.