Air carrier flight crew descended aircraft below clearance altitude during descent to airport.

Attributes
ACN	313486
Time
Date	199508
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : atl
State Reference	GA
Altitude	msl bound lower : 5600 msl bound upper : 6000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : atl
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 160 flight time total : 7500 flight time type : 2000
ASRS Report	313486
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : flight engineer pilot : instrument pilot : atp
Experience	flight time last 90 days : 67 flight time total : 14000 flight time type : 10000
ASRS Report	313030
Events
Anomaly	altitude deviation : overshoot non adherence : clearance
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Cleared to intercept the runway 8L localizer at atl and descend and maintain 6000 ft MSL. Descending through 5700 ft MSL on the glide path, I noticed my altitude deviation just before the altitude alerter sounded. Descent stopped at 5600 ft MSL and climbed back to 6000 ft MSL. Upon reaching 6000 ft MSL, approach controller cleared us for the ILS runway 8L. No other comments from him. Busy time -- lots of radio traffic, heading, airspeed changes. I was intent on being on course and on glide path and momentarily forgot our altitude clearance. Cannot recall if the captain gave altitude call-outs as per company SOP. Next time I'll try not to be so content with needles centered! Supplemental information from acn 313030: we were cleared to 6000 ft while being vectored for approach to atl. We were also slowed by controller to 180 KTS and flaps were configured to 15 degrees. I was working radio and looking out window to the east for traffic and airport. I glanced back inside and saw our altitude at 5600 ft. The problem seems to be inattn or losing track of clearance instructions or momentary 'day dreaming' by PF, and as usual for this kind of episode, it happened just as I diverted my attention elsewhere.

Original NASA ASRS Text

Title: ACR FLC DSNDED ACFT BELOW CLRNC ALT DURING DSCNT TO ARPT.

Narrative: CLRED TO INTERCEPT THE RWY 8L LOC AT ATL AND DSND AND MAINTAIN 6000 FT MSL. DSNDING THROUGH 5700 FT MSL ON THE GLIDE PATH, I NOTICED MY ALTDEV JUST BEFORE THE ALT ALERTER SOUNDED. DSCNT STOPPED AT 5600 FT MSL AND CLBED BACK TO 6000 FT MSL. UPON REACHING 6000 FT MSL, APCH CTLR CLRED US FOR THE ILS RWY 8L. NO OTHER COMMENTS FROM HIM. BUSY TIME -- LOTS OF RADIO TFC, HDG, AIRSPD CHANGES. I WAS INTENT ON BEING ON COURSE AND ON GLIDE PATH AND MOMENTARILY FORGOT OUR ALT CLRNC. CANNOT RECALL IF THE CAPT GAVE ALT CALL-OUTS AS PER COMPANY SOP. NEXT TIME I'LL TRY NOT TO BE SO CONTENT WITH NEEDLES CTRED! SUPPLEMENTAL INFO FROM ACN 313030: WE WERE CLRED TO 6000 FT WHILE BEING VECTORED FOR APCH TO ATL. WE WERE ALSO SLOWED BY CTLR TO 180 KTS AND FLAPS WERE CONFIGURED TO 15 DEGS. I WAS WORKING RADIO AND LOOKING OUT WINDOW TO THE E FOR TFC AND ARPT. I GLANCED BACK INSIDE AND SAW OUR ALT AT 5600 FT. THE PROB SEEMS TO BE INATTN OR LOSING TRACK OF CLRNC INSTRUCTIONS OR MOMENTARY 'DAY DREAMING' BY PF, AND AS USUAL FOR THIS KIND OF EPISODE, IT HAPPENED JUST AS I DIVERTED MY ATTN ELSEWHERE.

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.