Descending on approach, flight crew has altitude deviation due to use of vertical speed wheel.

Attributes
ACN	328580
Time
Date	199602
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : ord
State Reference	IL
Altitude	msl bound lower : 6600 msl bound upper : 7000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : ord
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : flight engineer pilot : commercial pilot : atp
Experience	flight time last 90 days : 498 flight time total : 5236 flight time type : 3128
ASRS Report	328580
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 15000 flight time type : 150
ASRS Report	328592
Events
Anomaly	altitude deviation : overshoot non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course flight crew : became reoriented
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Descending into O'hare airport using autoplt, captain flying. Clearance was to level off at 7000 ft and slow to 190 KTS. Captain used vertical speed wheel to reduce descent rate and slow to 190 KTS. Use of vertical speed wheel disarmed altitude capture function of autoplt and aircraft descended to 6600 ft before error was noted. Returned to 7000 ft and continued approach.

Original NASA ASRS Text

Title: DSNDING ON APCH, FLC HAS ALTDEV DUE TO USE OF VERT SPD WHEEL.

Narrative: DSNDING INTO O'HARE ARPT USING AUTOPLT, CAPT FLYING. CLRNC WAS TO LEVEL OFF AT 7000 FT AND SLOW TO 190 KTS. CAPT USED VERT SPD WHEEL TO REDUCE DSCNT RATE AND SLOW TO 190 KTS. USE OF VERT SPD WHEEL DISARMED ALT CAPTURE FUNCTION OF AUTOPLT AND ACFT DSNDED TO 6600 FT BEFORE ERROR WAS NOTED. RETURNED TO 7000 FT AND CONTINUED APCH.

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.