Narrative:

Having been cleared for the VOR C approach at sgu we crossed the VOR at 12400'. The ozn DME was OTS but it was not required for this approach. While procedure turn inbound and just out of 9000' we got a flag on the VOR and oscillations of both the HSI and RMI gyros. We are in mountainous terrain, with no DME, no VOR and erratic gyros. We missed the approach and immediately started a climb back to 12000'. We informed center of the miss and upon getting back into radar contact he told us we were supposed to be at 7000', the missed approach altitude. He obviously didn't know we had missed the approach clear back in procedure turn and had never gotten below 9000'. He told us to descend back to 9000' and cleared us for another approach. The problem is the discrepancy between where we were and where he thought we should have been. It could have been as much as a 3000' discrepancy. Supplemental information from acn 137850. We were at 6200' which is the procedure turn MDA. At this point we were unsure of our position. I indicated to the captain that I was going to begin a climb and he agreed. While missed approach altitude was 7000' we were not on any approach segment and I climbed to an altitude that I considered safe for that area (12000'). Callback conversation with reporter revealed following information. Reporter admits to lack of coordination in communication with center and stated that he was back in radar contact at 9000'. Further stated that when it rains in that area the VOR tends to produce either a spurious signal or goes OTS. Was mostly concerned with the fact that when the DME is OTS and then the VOR goes out you have no reference where you are as you are then (below 9000') out of radar contact and center cannot advise.

Related reports:

Google
 

Original NASA ASRS Text

Title: NAVIGATIONAL SIGNAL IRREGULARITY INDUCES FLT CREW TO PERFORM A MISSED APCH TO AN ILLEGAL ALT.

Narrative: HAVING BEEN CLRED FOR THE VOR C APCH AT SGU WE CROSSED THE VOR AT 12400'. THE OZN DME WAS OTS BUT IT WAS NOT REQUIRED FOR THIS APCH. WHILE PROC TURN INBND AND JUST OUT OF 9000' WE GOT A FLAG ON THE VOR AND OSCILLATIONS OF BOTH THE HSI AND RMI GYROS. WE ARE IN MOUNTAINOUS TERRAIN, WITH NO DME, NO VOR AND ERRATIC GYROS. WE MISSED THE APCH AND IMMEDIATELY STARTED A CLB BACK TO 12000'. WE INFORMED CENTER OF THE MISS AND UPON GETTING BACK INTO RADAR CONTACT HE TOLD US WE WERE SUPPOSED TO BE AT 7000', THE MISSED APCH ALT. HE OBVIOUSLY DIDN'T KNOW WE HAD MISSED THE APCH CLR BACK IN PROC TURN AND HAD NEVER GOTTEN BELOW 9000'. HE TOLD US TO DSND BACK TO 9000' AND CLRED US FOR ANOTHER APCH. THE PROB IS THE DISCREPANCY BTWN WHERE WE WERE AND WHERE HE THOUGHT WE SHOULD HAVE BEEN. IT COULD HAVE BEEN AS MUCH AS A 3000' DISCREPANCY. SUPPLEMENTAL INFO FROM ACN 137850. WE WERE AT 6200' WHICH IS THE PROC TURN MDA. AT THIS POINT WE WERE UNSURE OF OUR POS. I INDICATED TO THE CAPT THAT I WAS GOING TO BEGIN A CLB AND HE AGREED. WHILE MISSED APCH ALT WAS 7000' WE WERE NOT ON ANY APCH SEGMENT AND I CLBED TO AN ALT THAT I CONSIDERED SAFE FOR THAT AREA (12000'). CALLBACK CONVERSATION WITH RPTR REVEALED FOLLOWING INFO. RPTR ADMITS TO LACK OF COORD IN COM WITH CTR AND STATED THAT HE WAS BACK IN RADAR CONTACT AT 9000'. FURTHER STATED THAT WHEN IT RAINS IN THAT AREA THE VOR TENDS TO PRODUCE EITHER A SPURIOUS SIGNAL OR GOES OTS. WAS MOSTLY CONCERNED WITH THE FACT THAT WHEN THE DME IS OTS AND THEN THE VOR GOES OUT YOU HAVE NO REFERENCE WHERE YOU ARE AS YOU ARE THEN (BELOW 9000') OUT OF RADAR CONTACT AND CENTER CANNOT ADVISE.

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.