Narrative:

While on approach to landing (IMC) into det, (ILS runway 15) dec/89, I descended below the glide slope. I also lost contact with tower, in that, in switching radios (from approach to tower), I failed to turn up the volume on the tower frequency radio. Accordingly, tower was unable to advise of the descent below glide slope. Although we were IMC, when I descended below the glide slope I had broken below the ceiling and had visual contact with the ground, although not the airport. I was having difficulty making visual contact with the airport because the windshield was iced-over. I believe that I descended below the glide slope because: 1) fatigue: I was tired from the long trip (4 1/2 hours). 2) the fatigue was exacerbated by stress induced by a concern for low fuel in IMC (as it turned out, I had an hour remaining when I landed, but I thought that I had much less. I was also concerned about being delayed, 'holding', because of WX). 3) the ice added to the stress. Although the aircraft is 'full de-ice', and performance did not appear to be appreciably compromised, the ice accumulation worried me and seriously impaired my forward vision. 4) I transitioned outside too soon. I was looking for the airport before I should have. I fixated on matters outside the aircraft and lost concentration on the instruments. I had a similar incident on this approach some years ago.

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Original NASA ASRS Text

Title: CPR SMT ALT DEVIATION FAILED TO FOLLOW GLIDE SLOPE DURING ILS APCH TO DET IMC.

Narrative: WHILE ON APCH TO LNDG (IMC) INTO DET, (ILS RWY 15) DEC/89, I DESCENDED BELOW THE GLIDE SLOPE. I ALSO LOST CONTACT WITH TWR, IN THAT, IN SWITCHING RADIOS (FROM APCH TO TWR), I FAILED TO TURN UP THE VOLUME ON THE TWR FREQ RADIO. ACCORDINGLY, TWR WAS UNABLE TO ADVISE OF THE DSCNT BELOW GLIDE SLOPE. ALTHOUGH WE WERE IMC, WHEN I DESCENDED BELOW THE GLIDE SLOPE I HAD BROKEN BELOW THE CEILING AND HAD VISUAL CONTACT WITH THE GND, ALTHOUGH NOT THE ARPT. I WAS HAVING DIFFICULTY MAKING VISUAL CONTACT WITH THE ARPT BECAUSE THE WINDSHIELD WAS ICED-OVER. I BELIEVE THAT I DESCENDED BELOW THE GLIDE SLOPE BECAUSE: 1) FATIGUE: I WAS TIRED FROM THE LONG TRIP (4 1/2 HRS). 2) THE FATIGUE WAS EXACERBATED BY STRESS INDUCED BY A CONCERN FOR LOW FUEL IN IMC (AS IT TURNED OUT, I HAD AN HOUR REMAINING WHEN I LANDED, BUT I THOUGHT THAT I HAD MUCH LESS. I WAS ALSO CONCERNED ABOUT BEING DELAYED, 'HOLDING', BECAUSE OF WX). 3) THE ICE ADDED TO THE STRESS. ALTHOUGH THE ACFT IS 'FULL DE-ICE', AND PERFORMANCE DID NOT APPEAR TO BE APPRECIABLY COMPROMISED, THE ICE ACCUMULATION WORRIED ME AND SERIOUSLY IMPAIRED MY FORWARD VISION. 4) I TRANSITIONED OUTSIDE TOO SOON. I WAS LOOKING FOR THE ARPT BEFORE I SHOULD HAVE. I FIXATED ON MATTERS OUTSIDE THE ACFT AND LOST CONCENTRATION ON THE INSTRUMENTS. I HAD A SIMILAR INCIDENT ON THIS APCH SOME YEARS AGO.

Data retrieved from NASA's ASRS site as of August 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.