Narrative:

We were flying the dead head leg of a freight run. We were operating on an IFR flight plan. The WX was VMC although the visibility was poor. During the en route phase of the flight, center asked us to confirm our heading then turned us 10-20 degree right to avoid a restr area. When we were handed off to approach we were again asked to confirm our heading. The controller said he showed us headed straight for the VOR and asked if we concurred. I noticed that our compass indication did not match our selected course. I saw that the compass fluid level was low and mentioned it to the company pilot. At that time he didn't think there was any compass error. We decided to shoot the ILS runway 12R approach in to san antonio for practice and made our request to approach control. We were vectored to the final approach course and cleared for the approach. (I was flying the aircraft since there was no cargo on board and we were operating under part 91 at the time). When I intercepted the G/south I began the descent. We began to see a slight left of course indication and started to correct when ATC informed us that they had a low altitude alert on us. They asked if we had the airport in sight. We were unable to see the airport due to low visibility. Our compass showed our course and our dg was set to the compass. We never received a large deviation of the cdf to indicate we were off course. Deflection was less then half yet we were well left of course. ATC vectored us for another ILS. They queried us as to the problem. I intended to say that it appeared we had an instrumental problem but the company pilot refused to allow it. We simply told ATC that we had that we had the F/south but were off course. On the second approach the company pilot was able to see the airport. When we were again established on the localizer we could see that the compass was 40 degree divergent from or actual course. We were able to stay on course because we had the airport in sight. Also once we were aware of the problem we knew what compass indication to use to stay on course. Additionally, on this approach we used the ADF to help us stay on course. This is something we should have done in the first place. I had wanted to ask ATC for a heading check because I suspected something was wrong but the company pilot didn't want it known that we had a possible malfunction. I should have asked for verification of our heading. If we were shown to be off course I should have asked for vectors to final or an ASR approach. We should have used ADF to help us stay on course. The reason we didn't is that there had recently been problems with the alamo NDB giving unreliable signals and we didn't trust it. (FAA had been working on the problem and had changed the frequency to solve it). It would have been much safer to inform ATC or our suspected problem early on. Though we didn't confirm that we had an unreliable compass until the second approach I suspected earlier in the flight that there might be a problem. Had I asked ATC for verification of our heading I could at least have compensated for the error and possibly avoided the incident. Better still would have been to admit we had a malfunction and ask for assistance. Callback conversation with reporter revealed the following information. Reporter is a CFI and was along for the ferry flight in order to build time. The PIC was a very experienced and seasoned flight instrument and airman. Reporter was left very uncomfortable by the paranoia of the PIC, who was apparently concerned that, if any equipment malfunction were alluded to over the radio or on ATC tapes, that the plane would be precluded from flying until the anomaly was fixed. Visibility was very poor, and although both pilots were very familiar with the sat area, neither one could locate the airport while on the first ILS approach, and apparently the PIC was unable to even tell that he was off course in an area of rising terrain. Reporter said that she now refuses to fly with that operation any longer because of the uncomfortable situation and poor attitude on the part of the pilot and that company.

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Original NASA ASRS Text

Title: ATX PLT OF SMA ON FERRY FLT HAS INDICATIONS OF A MALFUNCTIONING WET COMPASS, BUT PIC PRECLUDES ASKING FOR ATC ASSISTANCE DUE TO FEAR OF RECRIMINATION. FLT SUBSEQUENTLY GOT WAY OFF COURSE AND CAUSED AN MSAW WARNING AS A DIRECT RESULT OF THE INACCURATE COMPASS.

Narrative: WE WERE FLYING THE DEAD HEAD LEG OF A FREIGHT RUN. WE WERE OPERATING ON AN IFR FLT PLAN. THE WX WAS VMC ALTHOUGH THE VISIBILITY WAS POOR. DURING THE ENRTE PHASE OF THE FLT, CTR ASKED US TO CONFIRM OUR HDG THEN TURNED US 10-20 DEG R TO AVOID A RESTR AREA. WHEN WE WERE HANDED OFF TO APCH WE WERE AGAIN ASKED TO CONFIRM OUR HDG. THE CTLR SAID HE SHOWED US HEADED STRAIGHT FOR THE VOR AND ASKED IF WE CONCURRED. I NOTICED THAT OUR COMPASS INDICATION DID NOT MATCH OUR SELECTED COURSE. I SAW THAT THE COMPASS FLUID LEVEL WAS LOW AND MENTIONED IT TO THE COMPANY PLT. AT THAT TIME HE DIDN'T THINK THERE WAS ANY COMPASS ERROR. WE DECIDED TO SHOOT THE ILS RWY 12R APCH IN TO SAN ANTONIO FOR PRACTICE AND MADE OUR REQUEST TO APCH CTL. WE WERE VECTORED TO THE FINAL APCH COURSE AND CLRED FOR THE APCH. (I WAS FLYING THE ACFT SINCE THERE WAS NO CARGO ON BOARD AND WE WERE OPERATING UNDER PART 91 AT THE TIME). WHEN I INTERCEPTED THE G/S I BEGAN THE DSNT. WE BEGAN TO SEE A SLIGHT L OF COURSE INDICATION AND STARTED TO CORRECT WHEN ATC INFORMED US THAT THEY HAD A LOW ALT ALERT ON US. THEY ASKED IF WE HAD THE ARPT IN SIGHT. WE WERE UNABLE TO SEE THE ARPT DUE TO LOW VISIBILITY. OUR COMPASS SHOWED OUR COURSE AND OUR DG WAS SET TO THE COMPASS. WE NEVER RECEIVED A LARGE DEV OF THE CDF TO INDICATE WE WERE OFF COURSE. DEFLECTION WAS LESS THEN HALF YET WE WERE WELL L OF COURSE. ATC VECTORED US FOR ANOTHER ILS. THEY QUERIED US AS TO THE PROB. I INTENDED TO SAY THAT IT APPEARED WE HAD AN INSTRUMENTAL PROB BUT THE COMPANY PLT REFUSED TO ALLOW IT. WE SIMPLY TOLD ATC THAT WE HAD THAT WE HAD THE F/S BUT WERE OFF COURSE. ON THE SECOND APCH THE COMPANY PLT WAS ABLE TO SEE THE ARPT. WHEN WE WERE AGAIN ESTABLISHED ON THE LOC WE COULD SEE THAT THE COMPASS WAS 40 DEG DIVERGENT FROM OR ACTUAL COURSE. WE WERE ABLE TO STAY ON COURSE BECAUSE WE HAD THE ARPT IN SIGHT. ALSO ONCE WE WERE AWARE OF THE PROB WE KNEW WHAT COMPASS INDICATION TO USE TO STAY ON COURSE. ADDITIONALLY, ON THIS APCH WE USED THE ADF TO HELP US STAY ON COURSE. THIS IS SOMETHING WE SHOULD HAVE DONE IN THE FIRST PLACE. I HAD WANTED TO ASK ATC FOR A HDG CHK BECAUSE I SUSPECTED SOMETHING WAS WRONG BUT THE COMPANY PLT DIDN'T WANT IT KNOWN THAT WE HAD A POSSIBLE MALFUNCTION. I SHOULD HAVE ASKED FOR VERIFICATION OF OUR HDG. IF WE WERE SHOWN TO BE OFF COURSE I SHOULD HAVE ASKED FOR VECTORS TO FINAL OR AN ASR APCH. WE SHOULD HAVE USED ADF TO HELP US STAY ON COURSE. THE REASON WE DIDN'T IS THAT THERE HAD RECENTLY BEEN PROBS WITH THE ALAMO NDB GIVING UNRELIABLE SIGNALS AND WE DIDN'T TRUST IT. (FAA HAD BEEN WORKING ON THE PROB AND HAD CHANGED THE FREQ TO SOLVE IT). IT WOULD HAVE BEEN MUCH SAFER TO INFORM ATC OR OUR SUSPECTED PROB EARLY ON. THOUGH WE DIDN'T CONFIRM THAT WE HAD AN UNRELIABLE COMPASS UNTIL THE SECOND APCH I SUSPECTED EARLIER IN THE FLT THAT THERE MIGHT BE A PROB. HAD I ASKED ATC FOR VERIFICATION OF OUR HDG I COULD AT LEAST HAVE COMPENSATED FOR THE ERROR AND POSSIBLY AVOIDED THE INCIDENT. BETTER STILL WOULD HAVE BEEN TO ADMIT WE HAD A MALFUNCTION AND ASK FOR ASSISTANCE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO. RPTR IS A CFI AND WAS ALONG FOR THE FERRY FLT IN ORDER TO BUILD TIME. THE PIC WAS A VERY EXPERIENCED AND SEASONED FLT INSTR AND AIRMAN. RPTR WAS LEFT VERY UNCOMFORTABLE BY THE PARANOIA OF THE PIC, WHO WAS APPARENTLY CONCERNED THAT, IF ANY EQUIP MALFUNCTION WERE ALLUDED TO OVER THE RADIO OR ON ATC TAPES, THAT THE PLANE WOULD BE PRECLUDED FROM FLYING UNTIL THE ANOMALY WAS FIXED. VISIBILITY WAS VERY POOR, AND ALTHOUGH BOTH PLTS WERE VERY FAMILIAR WITH THE SAT AREA, NEITHER ONE COULD LOCATE THE ARPT WHILE ON THE FIRST ILS APCH, AND APPARENTLY THE PIC WAS UNABLE TO EVEN TELL THAT HE WAS OFF COURSE IN AN AREA OF RISING TERRAIN. RPTR SAID THAT SHE NOW REFUSES TO FLY WITH THAT OPERATION ANY LONGER BECAUSE OF THE UNCOMFORTABLE SITUATION AND POOR ATTITUDE ON THE PART OF THE PLT AND THAT COMPANY.

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.