Narrative:

15 mi east of mry on the priest VOR 280 degree right while in contact with approach, I switched off the VOR in favor of following the localizer for 28 into mry VFR. After identing I set up an intercept angle which took me approximately 5 mi off course to the northeast. I probably entered sns' air traffic area and possibly through the fort ord restr area. ATC asked if I was going to turn toward the airport. I advised not in sight, and that I was trying to follow the ILS or localizer into airport. They advised not in service and not usable. ATC suggested a course to mry. After investigation I found that the ILS 10 and localizer 28 are on the the same frequency, not usable at the same time, and are switched by tower, one or the other. I must have idented the ILS 10 and followed reverse sensing in error. The identify code is slightly different, but with the frequency being the same I assumed I couldn't go wrong. In reality, I would have needed to identify more accurately, question any inconsistencies, request the localizer be activated if needed and perhaps advise ATC of my navigation intentions. For information, neither NOTAMS nor the local ATIS warns pilots that either the ILS or localizer is always OTS.

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Original NASA ASRS Text

Title: GA SMA TRACK HEADING DEVIATION UNAUTH PENETRATION OF AIRSPACE. PLT FOLLOWING THE WRONG NAVIGATION AID INTO MRY.

Narrative: 15 MI E OF MRY ON THE PRIEST VOR 280 DEG R WHILE IN CONTACT WITH APCH, I SWITCHED OFF THE VOR IN FAVOR OF FOLLOWING THE LOC FOR 28 INTO MRY VFR. AFTER IDENTING I SET UP AN INTERCEPT ANGLE WHICH TOOK ME APPROX 5 MI OFF COURSE TO THE NE. I PROBABLY ENTERED SNS' ATA AND POSSIBLY THROUGH THE FORT ORD RESTR AREA. ATC ASKED IF I WAS GOING TO TURN TOWARD THE ARPT. I ADVISED NOT IN SIGHT, AND THAT I WAS TRYING TO FOLLOW THE ILS OR LOC INTO ARPT. THEY ADVISED NOT IN SVC AND NOT USABLE. ATC SUGGESTED A COURSE TO MRY. AFTER INVESTIGATION I FOUND THAT THE ILS 10 AND LOC 28 ARE ON THE THE SAME FREQ, NOT USABLE AT THE SAME TIME, AND ARE SWITCHED BY TWR, ONE OR THE OTHER. I MUST HAVE IDENTED THE ILS 10 AND FOLLOWED REVERSE SENSING IN ERROR. THE IDENT CODE IS SLIGHTLY DIFFERENT, BUT WITH THE FREQ BEING THE SAME I ASSUMED I COULDN'T GO WRONG. IN REALITY, I WOULD HAVE NEEDED TO IDENT MORE ACCURATELY, QUESTION ANY INCONSISTENCIES, REQUEST THE LOC BE ACTIVATED IF NEEDED AND PERHAPS ADVISE ATC OF MY NAV INTENTIONS. FOR INFO, NEITHER NOTAMS NOR THE LCL ATIS WARNS PLTS THAT EITHER THE ILS OR LOC IS ALWAYS OTS.

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.