Light transport crew had altitude deviation at sbn.

Attributes
ACN	470350
Time
Date	200002
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : sbn.airport
State Reference	IN
Altitude	msl bound lower : 3400 msl bound upper : 4000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : sbn.tracon
Operator	common carrier : air carrier
Make Model Name	Light Transport, Low Wing, 2 Turboprop Eng
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer & glide slope : 27l
Flight Phase	descent : approach
Route In Use	approach : visual
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : atp
Experience	flight time last 90 days : 240 flight time total : 8200 flight time type : 2400
ASRS Report	470350
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : multi engine
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other controllera
Resolutory Action	controller : issued alert flight crew : returned to assigned altitude
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Descending into sbn airport, approach cleared us for a descent from 11000 ft to 4000 ft and to intercept the localizer for runway 27L. As we were intercepting the localizer, I thought we were cleared for the visual and continued descent to 3400 ft before reversing vertical rate and climbing to 4000 ft. ATC asked our altitude. We responded correcting and he did not ask for further information. Contributing factors: VMC, visual approach expected, and filed (runway) in sight.

Original NASA ASRS Text

Title: LTT CREW HAD ALTDEV AT SBN.

Narrative: DSNDING INTO SBN ARPT, APCH CLRED US FOR A DSCNT FROM 11000 FT TO 4000 FT AND TO INTERCEPT THE LOC FOR RWY 27L. AS WE WERE INTERCEPTING THE LOC, I THOUGHT WE WERE CLRED FOR THE VISUAL AND CONTINUED DSCNT TO 3400 FT BEFORE REVERSING VERT RATE AND CLBING TO 4000 FT. ATC ASKED OUR ALT. WE RESPONDED CORRECTING AND HE DID NOT ASK FOR FURTHER INFO. CONTRIBUTING FACTORS: VMC, VISUAL APCH EXPECTED, AND FILED (RWY) IN SIGHT.

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.