Narrative:

I had been descending from 14;000 ft. Where the temperature was -18c down to cross yager intersection (the initial approach fix) for the ILS 32 into acv as cleared at 7;000 ft. Onboard equipment had indicated an area of moderate precipitation along most of the approach. Thus I was concerned about potential for icing. Temperature at acv was reported as 8c. My general tactic in these situations was to keep my speed up to present the minimum angle of attack in order to minimize icing potential. I was approaching at approximately 160 kts IAS. I was used to crossing yager at 7;000 ft. And seeing the glideslope come down on my instrumentation from above; slowly but surely. I had been in a habit of monitoring my minimum crossing altitude of 5;700 ft. Before the next stepdown of vomac as I had flown [this route] many times. As is our usual policy; I was watching on the approach for a point where I was VMC and could cancel IFR and proceed to my ultimate destination of eka. It was night still and during most of the descent I was IMC; so basically visibility was nil and it was raining most of the time. I was dividing my attention between monitoring my wing for icing with my icing light; looking for a VMC path to eka; and flying the approach. I knew I was approximately 1/3 deflection below the glideslope but it had been moving down steadily so it did not concern me much; since I was still well outside (approximately 9.7nm) the FAF of volew. It should be mentioned that usually I flew this approach at 120 kts or less but today was unusual in that I chose to fly it at 160 kts.then the seattle center controller mentioned that I was low on the approach and that the crossing altitude at vomac was 5;700 MSL. I looked at my altimeter and noticed I was at approximately 5;000 ft. MSL. Obviously; I corrected immediately and was back at the proper altitude within a matter of seconds. Later; I noticed that the highest obstacle near vomac was 3729 MSL. Thus I had potentially come within 1;271 ft. Of it.after that; the approach went as normal; and I broke out under the ceiling; was in VMC; cancelled IFR; and had an uneventful flight to eka; landing in the dark.I think my failure to monitor the altitude at the step down fix was due to my familiarity with the approach which made me more relaxed about it than I was with being concerned about the icing potential and being able to peel off the approach at the most opportune moment for eka. I think a contributing factor was the higher speed at which I flew the approach; giving me less time to monitor where I was along it while doing other tasks.essentially it was a case of mistaken priorities and the step down altitude had been regulated to a lower priority subconsciously in my mind as I felt over-confident that the nearing glideslope indication would keep me safe. Obviously this was a false assumption that in the heat of the moment I had subconsciously made.thus I chose to write this report to help reemphasize in my mind the importance of step down fix altitudes on an ILS approach.I found the info 11009 document published by the FAA on 3/28/2011 online and this helped a lot in helping me understand my error.I am also thankful for the seattle center controller doing a good job of monitoring my approach.

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Original NASA ASRS Text

Title: A commercial fixed wing pilot reported descending below the glideslope and coming within 1;271 feet of an obstacle while in IFR conditions.

Narrative: I had been descending from 14;000 ft. where the temperature was -18c down to cross YAGER intersection (the initial approach fix) for the ILS 32 into ACV as cleared at 7;000 ft. Onboard equipment had indicated an area of moderate precipitation along most of the approach. Thus I was concerned about potential for icing. Temperature at ACV was reported as 8c. My general tactic in these situations was to keep my speed up to present the minimum angle of attack in order to minimize icing potential. I was approaching at approximately 160 kts IAS. I was used to crossing YAGER at 7;000 ft. and seeing the glideslope come down on my instrumentation from above; slowly but surely. I had been in a habit of monitoring my minimum crossing altitude of 5;700 ft. before the next stepdown of VOMAC as I had flown [this route] many times. As is our usual policy; I was watching on the approach for a point where I was VMC and could cancel IFR and proceed to my ultimate destination of EKA. It was night still and during most of the descent I was IMC; so basically visibility was nil and it was raining most of the time. I was dividing my attention between monitoring my wing for icing with my icing light; looking for a VMC path to EKA; and flying the approach. I knew I was approximately 1/3 deflection below the glideslope but it had been moving down steadily so it did not concern me much; since I was still well outside (approximately 9.7nm) the FAF of VOLEW. It should be mentioned that usually I flew this approach at 120 kts or less but today was unusual in that I chose to fly it at 160 kts.Then the Seattle Center Controller mentioned that I was low on the approach and that the crossing altitude at VOMAC was 5;700 MSL. I looked at my altimeter and noticed I was at approximately 5;000 ft. MSL. Obviously; I corrected immediately and was back at the proper altitude within a matter of seconds. Later; I noticed that the highest obstacle near VOMAC was 3729 MSL. Thus I had potentially come within 1;271 ft. of it.After that; the approach went as normal; and I broke out under the ceiling; was in VMC; cancelled IFR; and had an uneventful flight to EKA; landing in the dark.I think my failure to monitor the altitude at the step down fix was due to my familiarity with the approach which made me more relaxed about it than I was with being concerned about the icing potential and being able to peel off the approach at the most opportune moment for EKA. I think a contributing factor was the higher speed at which I flew the approach; giving me less time to monitor where I was along it while doing other tasks.Essentially it was a case of mistaken priorities and the step down altitude had been regulated to a lower priority subconsciously in my mind as I felt over-confident that the nearing glideslope indication would keep me safe. Obviously this was a false assumption that in the heat of the moment I had subconsciously made.Thus I chose to write this report to help reemphasize in my mind the importance of step down fix altitudes on an ILS approach.I found the InFO 11009 document published by the FAA on 3/28/2011 online and this helped a lot in helping me understand my error.I am also thankful for the Seattle Center controller doing a good job of monitoring my approach.

Data retrieved from NASA's ASRS site 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.