Air carrier first officer descended below assigned clearance altitude while on vector for approach.

Attributes
ACN	305700
Time
Date	199505
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : iad
State Reference	VA
Altitude	msl bound lower : 5700 msl bound upper : 6000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : iad
Operator	common carrier : air carrier
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
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 : 10 flight time total : 9000 flight time type : 10
ASRS Report	305700
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other flight crewa
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:

Being vectored for the ILS runway 12 approach at iad, I dropped below my assigned altitude of 6000 ft. The captain called it out and I corrected. Lowest altitude was 5700 ft MSL. Nothing was said by approach control.

Original NASA ASRS Text

Title: ACR FO DSNDED BELOW ASSIGNED CLRNC ALT WHILE ON VECTOR FOR APCH.

Narrative: BEING VECTORED FOR THE ILS RWY 12 APCH AT IAD, I DROPPED BELOW MY ASSIGNED ALT OF 6000 FT. THE CAPT CALLED IT OUT AND I CORRECTED. LOWEST ALT WAS 5700 FT MSL. NOTHING WAS SAID BY APCH CTL.

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.