Narrative:

The WX at sat was reported as 400 sky obscured, visibility 5/8 of a mi, or RVR 6000'. The visibility was changing throughout the approach, but it was always reported within minimums for the approach. I was cleared to maintain 3000' and intercept the localizer, and clear for the approach. I never received the G/south on either one of the instruments capable of doing so. At that point, when I was 2 mi from the runway, I was cleared for a missed approach. I explained the problem, and requested an ASR approach to the same runway. The MDA was 1300' MSL. I shot the approach hoping the G/south would work that time, but I didn't even receive a normal deflection from the localizer needle, although the controller said I was on course. I decided I would give it another try again thinking the localizer and G/south would function. I requested another ASR to runway 12R, and as I was coming down I tapped the instrument. I continued with the ASR procedure, and at 1300' the localizer and G/south started to work, and since I had them as a back-up, I proceeded to descend to ILS minimums, got the field in sight (I didn't on the second one) and made a normal landing. Since I was on a scheduled air taxi operation, I'm sure there was a question as of why I had to shoot 3 approachs, and I had already decided after that one, I would probably hold for a while to see if the WX conditions would improve enough to shoot a different approach--or I was going to go to an alternate. The G/south had been working all night at different airports, with different frequencys, so that's why I thought I should give it a try--to see if it would come back, and it did. To prevent this occurrence from happening again, the aircraft was inspected by an avionics specialist, although the only place at which it didn't work was at sat. This occurred due to an intermittent malfunction of the instrument.

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Original NASA ASRS Text

Title: ILS INSTRUMENT PROBLEM CAUSES MISSED APCHS.

Narrative: THE WX AT SAT WAS RPTED AS 400 SKY OBSCURED, VISIBILITY 5/8 OF A MI, OR RVR 6000'. THE VISIBILITY WAS CHANGING THROUGHOUT THE APCH, BUT IT WAS ALWAYS RPTED WITHIN MINIMUMS FOR THE APCH. I WAS CLRED TO MAINTAIN 3000' AND INTERCEPT THE LOC, AND CLR FOR THE APCH. I NEVER RECEIVED THE G/S ON EITHER ONE OF THE INSTRUMENTS CAPABLE OF DOING SO. AT THAT POINT, WHEN I WAS 2 MI FROM THE RWY, I WAS CLRED FOR A MISSED APCH. I EXPLAINED THE PROB, AND REQUESTED AN ASR APCH TO THE SAME RWY. THE MDA WAS 1300' MSL. I SHOT THE APCH HOPING THE G/S WOULD WORK THAT TIME, BUT I DIDN'T EVEN RECEIVE A NORMAL DEFLECTION FROM THE LOC NEEDLE, ALTHOUGH THE CTLR SAID I WAS ON COURSE. I DECIDED I WOULD GIVE IT ANOTHER TRY AGAIN THINKING THE LOC AND G/S WOULD FUNCTION. I REQUESTED ANOTHER ASR TO RWY 12R, AND AS I WAS COMING DOWN I TAPPED THE INSTRUMENT. I CONTINUED WITH THE ASR PROC, AND AT 1300' THE LOC AND G/S STARTED TO WORK, AND SINCE I HAD THEM AS A BACK-UP, I PROCEEDED TO DSND TO ILS MINIMUMS, GOT THE FIELD IN SIGHT (I DIDN'T ON THE SECOND ONE) AND MADE A NORMAL LNDG. SINCE I WAS ON A SCHEDULED AIR TAXI OPERATION, I'M SURE THERE WAS A QUESTION AS OF WHY I HAD TO SHOOT 3 APCHS, AND I HAD ALREADY DECIDED AFTER THAT ONE, I WOULD PROBABLY HOLD FOR A WHILE TO SEE IF THE WX CONDITIONS WOULD IMPROVE ENOUGH TO SHOOT A DIFFERENT APCH--OR I WAS GOING TO GO TO AN ALTERNATE. THE G/S HAD BEEN WORKING ALL NIGHT AT DIFFERENT ARPTS, WITH DIFFERENT FREQS, SO THAT'S WHY I THOUGHT I SHOULD GIVE IT A TRY--TO SEE IF IT WOULD COME BACK, AND IT DID. TO PREVENT THIS OCCURRENCE FROM HAPPENING AGAIN, THE ACFT WAS INSPECTED BY AN AVIONICS SPECIALIST, ALTHOUGH THE ONLY PLACE AT WHICH IT DIDN'T WORK WAS AT SAT. THIS OCCURRED DUE TO AN INTERMITTENT MALFUNCTION OF THE INSTRUMENT.

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.