C172 pilot descends below published procedure altitude on ILS approach.

Attributes
ACN	334460
Time
Date	199604
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : mry
State Reference	CA
Altitude	msl bound lower : 1550 msl bound upper : 1700
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : mry
Operator	general aviation : personal
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : commercial pilot : instrument
Experience	flight time last 90 days : 15 flight time total : 435 flight time type : 189
ASRS Report	334460
Person 2
Affiliation	government : faa
Function	controller : local
Qualification	controller : non radar
Events
Anomaly	non adherence : published procedure non adherence : far
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:

I was flying practice IFR approachs in the mry area with a fellow pilot. I had just taken the controls, and mry approach vectored us for the ILS runway 10R approach. We were instructed to maintain 2000 ft, cleared for the ILS runway 10R approach. Due to strong winds, I flew through the localizer, requiring a turn to the left to reintercept. Approach handed us off to the tower. We acquired GS indication and began a descent. During this descent we may have fallen below GS, but not offscale. About 1-2 mi outside munso, tower informed us of a low altitude alert, and told us we should be at 1700 ft until munso. Altimeter read 1550 ft at this point. Commercial chart shows GS is 1603 ft at munso. We immediately climbed back to 1700 ft. Analyzing this approach, I do not believe we violated an far, however, it is not good practice to fall below the GS. I will endeavor to conduct instrument approachs at or above GS in future. The tower controller should be aware that GS is 1603 ft at munso, not 1700 ft.

Original NASA ASRS Text

Title: C172 PLT DSNDS BELOW PUBLISHED PROC ALT ON ILS APCH.

Narrative: I WAS FLYING PRACTICE IFR APCHS IN THE MRY AREA WITH A FELLOW PLT. I HAD JUST TAKEN THE CTLS, AND MRY APCH VECTORED US FOR THE ILS RWY 10R APCH. WE WERE INSTRUCTED TO MAINTAIN 2000 FT, CLRED FOR THE ILS RWY 10R APCH. DUE TO STRONG WINDS, I FLEW THROUGH THE LOC, REQUIRING A TURN TO THE L TO REINTERCEPT. APCH HANDED US OFF TO THE TWR. WE ACQUIRED GS INDICATION AND BEGAN A DSCNT. DURING THIS DSCNT WE MAY HAVE FALLEN BELOW GS, BUT NOT OFFSCALE. ABOUT 1-2 MI OUTSIDE MUNSO, TWR INFORMED US OF A LOW ALT ALERT, AND TOLD US WE SHOULD BE AT 1700 FT UNTIL MUNSO. ALTIMETER READ 1550 FT AT THIS POINT. COMMERCIAL CHART SHOWS GS IS 1603 FT AT MUNSO. WE IMMEDIATELY CLBED BACK TO 1700 FT. ANALYZING THIS APCH, I DO NOT BELIEVE WE VIOLATED AN FAR, HOWEVER, IT IS NOT GOOD PRACTICE TO FALL BELOW THE GS. I WILL ENDEAVOR TO CONDUCT INST APCHS AT OR ABOVE GS IN FUTURE. THE TWR CTLR SHOULD BE AWARE THAT GS IS 1603 FT AT MUNSO, NOT 1700 FT.

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.