Medium large transport crew had altitude overshoot.

Attributes
ACN	473530
Time
Date	200005
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : mad.vor
State Reference	NH
Altitude	msl bound lower : 9800 msl bound upper : 10000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zbw.artcc tower : dca.tower
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Operating Under FAR Part	Part 121
Flight Phase	descent : vacating altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 5000 flight time type : 2500
ASRS Report	473530
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : overshoot non adherence : clearance
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : returned to assigned altitude none taken : detected after the fact
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

Approximately 10 mi west of mad VOR, ATC cleared air carrier abcd to descend from 11000 ft to 10000 ft MSL. At leveloff (10000 ft) aircraft's autoplt disengaged causing the aircraft to momentarily descend to approximately 9800 ft, and air crew smoothly flew manually back to 10000 ft MSL. Upon landing, autoplt was written up and air carrier maintenance notified.

Original NASA ASRS Text

Title: MLG CREW HAD ALT OVERSHOOT.

Narrative: APPROX 10 MI W OF MAD VOR, ATC CLRED ACR ABCD TO DSND FROM 11000 FT TO 10000 FT MSL. AT LEVELOFF (10000 FT) ACFT'S AUTOPLT DISENGAGED CAUSING THE ACFT TO MOMENTARILY DSND TO APPROX 9800 FT, AND AIR CREW SMOOTHLY FLEW MANUALLY BACK TO 10000 FT MSL. UPON LNDG, AUTOPLT WAS WRITTEN UP AND ACR MAINT NOTIFIED.

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.