Narrative:

The event occurred during a localizer backcourse approach to ama runway 22. The approach was in IMC after a flight from tulsa, ok on V140, involved a descent below minimum and an incursion into prohibited airspace P47. I was navigating by the RNAV, which stores 4 frequencys but displays only 1 at a time. My #2 navigation is a different type and both radios were working well. Ama approach issued radar vectors to the final approach course and an altitude of 5000' until elice intersection, then cleared for the localizer backcourse 22. I intercepted the localizer (or thought I did) and turned inbound with the HSI needle 1 DOT to the left, and at a DME reading of about 7 NM. My first indication of trouble was when ATC told me I was 1 mi north of course. I felt this was too much deviation for only 1 DOT on the HSI, so I tuned my #2 navigation to the localizer 110.3 and found it to show a greater right of course deviation, so I began correcting to the left. At about this time I crossed 4.2 NM on the DME, and since I thought I had reached elice I began my descent. At 4500' ATC instructed me to maintain 5000' until elice. At virtually that moment I noticed that the #2 navigation was displaying 110.3 (localizer), but was using a different frequency, 117.2, the ama VORTAC. Apparently I had never pressed the 'use' button after I brought up the localizer frequency. I initiated an immediate climb back to 5000', tuned the localizer on 110.3 and continued to make a left correction to center the needle. I believe, however, that not only did I descend below published minimum, but I also violated the P47 airspace which extended to 4800' MSL. After passing the real elice, I again descended and made an otherwise uneventful circle to land on runway 13.

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Original NASA ASRS Text

Title: GA SMA SINGLE PLT IFR TRACK HEADING DEVIATION AND ALT EXCURSION WHILE FLYING AN IAP ILS APCH TO AMA. ALSO UNAUTH PENETRATION OF AIRSPACE.

Narrative: THE EVENT OCCURRED DURING A LOC BACKCOURSE APCH TO AMA RWY 22. THE APCH WAS IN IMC AFTER A FLT FROM TULSA, OK ON V140, INVOLVED A DSNT BELOW MINIMUM AND AN INCURSION INTO PROHIBITED AIRSPACE P47. I WAS NAVIGATING BY THE RNAV, WHICH STORES 4 FREQS BUT DISPLAYS ONLY 1 AT A TIME. MY #2 NAV IS A DIFFERENT TYPE AND BOTH RADIOS WERE WORKING WELL. AMA APCH ISSUED RADAR VECTORS TO THE FINAL APCH COURSE AND AN ALT OF 5000' UNTIL ELICE INTXN, THEN CLRED FOR THE LOC BACKCOURSE 22. I INTERCEPTED THE LOC (OR THOUGHT I DID) AND TURNED INBND WITH THE HSI NEEDLE 1 DOT TO THE LEFT, AND AT A DME READING OF ABOUT 7 NM. MY FIRST INDICATION OF TROUBLE WAS WHEN ATC TOLD ME I WAS 1 MI N OF COURSE. I FELT THIS WAS TOO MUCH DEVIATION FOR ONLY 1 DOT ON THE HSI, SO I TUNED MY #2 NAV TO THE LOC 110.3 AND FOUND IT TO SHOW A GREATER RIGHT OF COURSE DEVIATION, SO I BEGAN CORRECTING TO THE LEFT. AT ABOUT THIS TIME I CROSSED 4.2 NM ON THE DME, AND SINCE I THOUGHT I HAD REACHED ELICE I BEGAN MY DSNT. AT 4500' ATC INSTRUCTED ME TO MAINTAIN 5000' UNTIL ELICE. AT VIRTUALLY THAT MOMENT I NOTICED THAT THE #2 NAV WAS DISPLAYING 110.3 (LOC), BUT WAS USING A DIFFERENT FREQ, 117.2, THE AMA VORTAC. APPARENTLY I HAD NEVER PRESSED THE 'USE' BUTTON AFTER I BROUGHT UP THE LOC FREQ. I INITIATED AN IMMEDIATE CLB BACK TO 5000', TUNED THE LOC ON 110.3 AND CONTINUED TO MAKE A LEFT CORRECTION TO CENTER THE NEEDLE. I BELIEVE, HOWEVER, THAT NOT ONLY DID I DSND BELOW PUBLISHED MINIMUM, BUT I ALSO VIOLATED THE P47 AIRSPACE WHICH EXTENDED TO 4800' MSL. AFTER PASSING THE REAL ELICE, I AGAIN DSNDED AND MADE AN OTHERWISE UNEVENTFUL CIRCLE TO LAND ON RWY 13.

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.