Narrative:

I was returning home from cvg to juy (a short flight) IFR in marginal VFR to IFR conditions. After checking WX, and preflting my MK20C single engine mooney, I departed cvg uneventfully. I was descended to 2600 ft MSL, given an intercept heading and the following clearance from sdf approach. 'Aircraft X, turn left heading 210 degrees, maintain 2600 ft, cleared ILS runway 18 juy.' I acknowledged the clearance, and the controller added I was 4 mi from the OM. The approach calls for 2600 ft until OM, where the GS intercepts the given altitude (approximately). Being used to intercepting GS's far outside the marker, I began to follow the GS indicator in my aircraft. I was also used to flying approachs at 140-150 KTS versus 50 KIAS, thus I felt the OM had passed -- it didn't. No lights/tone heard as I descended to 1500 ft MSL, the alert controller noted my altitude and position (2 NM outside the OM). I quickly climbed, verified position on GPS, then heard the OM tone. I continued the approach as a localizer seeing the runway with 2 NM. Conditions were such that I had ground contact throughout the approach.

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Original NASA ASRS Text

Title: ON RECEIVING A CLRNC FOR AN ILS APCH TO SDF ARPT, THE PLT, FLYING A MOONEY ACFT, BEGAN HIS DSCNT FROM THE APCH ALT BEFORE HE HAD REACHED THE GLIDE PATH INTERCEPT POINT. THE PLT CLAIMS HE WAS FOLLOWING THE GS INDICATOR BUT WAS ALERTED BY THE CTLR WHEN HE DSNDED BEFORE THE INTERCEPT POINT.

Narrative: I WAS RETURNING HOME FROM CVG TO JUY (A SHORT FLT) IFR IN MARGINAL VFR TO IFR CONDITIONS. AFTER CHKING WX, AND PREFLTING MY MK20C SINGLE ENG MOONEY, I DEPARTED CVG UNEVENTFULLY. I WAS DSNDED TO 2600 FT MSL, GIVEN AN INTERCEPT HEADING AND THE FOLLOWING CLRNC FROM SDF APCH. 'ACFT X, TURN L HDG 210 DEGS, MAINTAIN 2600 FT, CLRED ILS RWY 18 JUY.' I ACKNOWLEDGED THE CLRNC, AND THE CTLR ADDED I WAS 4 MI FROM THE OM. THE APCH CALLS FOR 2600 FT UNTIL OM, WHERE THE GS INTERCEPTS THE GIVEN ALT (APPROX). BEING USED TO INTERCEPTING GS'S FAR OUTSIDE THE MARKER, I BEGAN TO FOLLOW THE GS INDICATOR IN MY ACFT. I WAS ALSO USED TO FLYING APCHS AT 140-150 KTS VERSUS 50 KIAS, THUS I FELT THE OM HAD PASSED -- IT DIDN'T. NO LIGHTS/TONE HEARD AS I DSNDED TO 1500 FT MSL, THE ALERT CTLR NOTED MY ALT AND POS (2 NM OUTSIDE THE OM). I QUICKLY CLBED, VERIFIED POS ON GPS, THEN HEARD THE OM TONE. I CONTINUED THE APCH AS A LOC SEEING THE RWY WITH 2 NM. CONDITIONS WERE SUCH THAT I HAD GND CONTACT THROUGHOUT THE 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.