GA small aircraft started descent before reaching IAF for an ILS approach to runway 22 at evv.

Attributes
ACN	167935
Time
Date	199101
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : evv
State Reference	IN
Altitude	msl bound lower : 2100 msl bound upper : 2500
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : evv tower : evv
Operator	general aviation : corporate
Make Model Name	Small Aircraft, High Wing, 1 Eng, Retractable Gear
Flight Phase	descent : approach
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : commercial pilot : cfi
Experience	flight time last 90 days : 60 flight time total : 5870 flight time type : 3650
ASRS Report	167935
Person 2
Affiliation	government : faa
Function	controller : local
Qualification	controller : radar
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : published procedure non adherence : clearance
Independent Detector	other controllera
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

How the problem arose: evv approach control gave me vectors to intercept the localizer for runway 22 at evv and turned me over to evv tower 3 mi from vicci. I flew 250 degrees until the CDI indicated intercepting the localizer at the LOM, as the ADF needle indicated passing the LOM and CDI showed going right of course. I corrected and started my descent from 2500'. Contributing factors: sometimes or other I pushed the backcourse button and was actually left of course. The marker lights never showed crossing the OM and the G/south never coupled. The ADF indicated I was inside the OM. How it was discovered: evv tower informed me that I was below minimum outside the OM and left of course. Corrective action: I added power to gain altitude and checked my INS and radios. Reset the backcourse button and informed evv tower I showed inside the OM and left of course, correcting right on the localizer west/O a G/south. Perceptions, judgement, decisions: I should have missed approach, but in my judgement, I had about 3.5 NM to the MM carrying 80 KTS of airspeed. This was plenty of time before missed approach point to correct my position on the localizer and still complete a safe localizer approach.

Original NASA ASRS Text

Title: GA SMA STARTED DESCENT BEFORE REACHING IAF FOR AN ILS APCH TO RWY 22 AT EVV.

Narrative: HOW THE PROB AROSE: EVV APCH CTL GAVE ME VECTORS TO INTERCEPT THE LOC FOR RWY 22 AT EVV AND TURNED ME OVER TO EVV TWR 3 MI FROM VICCI. I FLEW 250 DEGS UNTIL THE CDI INDICATED INTERCEPTING THE LOC AT THE LOM, AS THE ADF NEEDLE INDICATED PASSING THE LOM AND CDI SHOWED GOING RIGHT OF COURSE. I CORRECTED AND STARTED MY DSNT FROM 2500'. CONTRIBUTING FACTORS: SOMETIMES OR OTHER I PUSHED THE BACKCOURSE BUTTON AND WAS ACTUALLY LEFT OF COURSE. THE MARKER LIGHTS NEVER SHOWED XING THE OM AND THE G/S NEVER COUPLED. THE ADF INDICATED I WAS INSIDE THE OM. HOW IT WAS DISCOVERED: EVV TWR INFORMED ME THAT I WAS BELOW MINIMUM OUTSIDE THE OM AND LEFT OF COURSE. CORRECTIVE ACTION: I ADDED PWR TO GAIN ALT AND CHKED MY INS AND RADIOS. RESET THE BACKCOURSE BUTTON AND INFORMED EVV TWR I SHOWED INSIDE THE OM AND LEFT OF COURSE, CORRECTING RIGHT ON THE LOC W/O A G/S. PERCEPTIONS, JUDGEMENT, DECISIONS: I SHOULD HAVE MISSED APCH, BUT IN MY JUDGEMENT, I HAD ABOUT 3.5 NM TO THE MM CARRYING 80 KTS OF AIRSPD. THIS WAS PLENTY OF TIME BEFORE MISSED APCH POINT TO CORRECT MY POS ON THE LOC AND STILL COMPLETE A SAFE LOC 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.