Descent begun before the final approach fix on a back course ILS.

Attributes
ACN	505540
Time
Date	200103
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	intersection : wagor
State Reference	IL
Altitude	msl single value : 2600
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : sct.tracon
Operator	common carrier : charter
Make Model Name	Chancellor 414A & C414
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : charter
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : instrument pilot : multi engine pilot : cfi
Experience	flight time last 90 days : 40 flight time total : 1800 flight time type : 300
ASRS Report	505540
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : weather inflight encounter other non adherence : published procedure non adherence : clearance other spatial deviation
Resolutory Action	flight crew : returned to assigned altitude
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

In flying the localizer back course at bmi, mistakenly took LORAN's readout (used as a backup to primary navigation) as being at FAF, when in fact we were about 5 miles DME from FAF. Started non-precision descent before actually being at the FAF. Once realized, promptly climbed back to intermediate segment. Contributing factors: fatigue from previous days flight, minimum rest received, low IFR west/icing and flying single pilot operations.

Original NASA ASRS Text

Title: DESCENT BEGUN BEFORE THE FINAL APCH FIX ON A BACK COURSE ILS.

Narrative: IN FLYING THE LOC BACK COURSE AT BMI, MISTAKENLY TOOK LORAN'S READOUT (USED AS A BACKUP TO PRIMARY NAV) AS BEING AT FAF, WHEN IN FACT WE WERE ABOUT 5 MILES DME FROM FAF. STARTED NON-PRECISION DESCENT BEFORE ACTUALLY BEING AT THE FAF. ONCE REALIZED, PROMPTLY CLIMBED BACK TO INTERMEDIATE SEGMENT. CONTRIBUTING FACTORS: FATIGUE FROM PREVIOUS DAYS FLT, MINIMUM REST RECEIVED, LOW IFR W/ICING AND FLYING SINGLE PLT OPS.

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.