Narrative:

On apr/fri/95, I was en route from north las vegas, nv, airport to san marcos, tx, airport accompanied by my wife, a non-pilot, in a single engine piper PA24-260C aircraft. At approximately XA00 local time, following a fuel stop at deming, NM, en route to our next waypoint, newman VOR, I noticed that the dial and pointer on the kcs 55A directional gyroscope, coupled to a kns 80 navigation system, were roughly 180 degrees off. I recalled that this had happened at least once before in the 14 yrs I had used this instrument and had soon corrected itself, so felt no great concern, particularly since I had another navigation/communication and a LORAN C aboard, although neither of these instruments was on line at the time. The DME of the kns 80 was operational and I concluded, erroneously, that I could navigate by using the reciprocal of the indicated heading. As we climbed 'on course' to our cruising altitude of 11500 ft, I attempted to contact ZAB on the frequency for that area shown on the chart, but was unable to do so, although I was receiving their xmissions. Approximately 1/2 way to newman VOR the LORAN C, which had been largely inoperable across new mexico and arizona due to 'bad geometry,' finally came on line and showed us about 8 nautical mi south of course. I finally contacted ZAB with the assistance of the crew of an airliner and advised them of our situation and asked for assistance. The albuquerque controller, through a series of standard rate turns, located us approximately 15 NM south of course and established us on a course to el paso airport, where we planned to land and seek assistance with our radios. At this time I finally glanced at the digital voltmeter and noted that it showed between 11 and 12 volts. I cycled the alternator switch and the voltmeter showed 14 plus volts and the directional gyroscope, and other equipment, came on line. I advised center and was handed off to el paso approach control. I tuned in to el paso VOR and asked the controller to verify our bearing and distance from the VOR, which he did. I then tuned in hudspeth VOR, the next waypoint on our course, and upon receiving it advised el paso that we would proceed to our destination, which we did without further incident. I later consulted with my avionics specialist and we agreed that our radio problems probably resulted from the low voltage. He also showed me how to disengage the 'slaved' mode of the kcs 55A and that once in normal mode the display could be moved to the desired position. He also pointed that in the reversed position so called 'reverse needle sensing' would be required to use the instrument for navigation. He also checked our magnetic compass, which both my wife and I had tried unsuccessfully to read as a check of our heading, and we concluded that, although part of the problem had been due to the light to moderate turbulence in which we were operating, the liquid in the compass did show evidence of contamination and that possibly the instrument was not level in flight and should be thoroughly checked and serviced. Some of the conclusions I have so far reached as a result of the above are, first, that in spite of all distrs, it is absolutely essential to continue your 'normal scan,' which I obviously failed to do, since I had no recollection of once looking at the voltmeter until the situation was largely resolved, and that it is very easy to forget all we once knew about the 'tools' we work with, particularly if they are trouble free. Also, that we should regularly review the operational factors of all the instruments we so completely rely on, and, finally, that even an instrument as mundane as the magnetic compass can be very important if the more sophisticated ones fail.

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Original NASA ASRS Text

Title: ACFT EQUIP PROB - PLT DISCOVERS THAT AN ALTERNATOR MALFUNCTION IS THE CAUSE OF HIS NAV SYS ERRORS.

Narrative: ON APR/FRI/95, I WAS ENRTE FROM N LAS VEGAS, NV, ARPT TO SAN MARCOS, TX, ARPT ACCOMPANIED BY MY WIFE, A NON-PLT, IN A SINGLE ENG PIPER PA24-260C ACFT. AT APPROX XA00 LCL TIME, FOLLOWING A FUEL STOP AT DEMING, NM, ENRTE TO OUR NEXT WAYPOINT, NEWMAN VOR, I NOTICED THAT THE DIAL AND POINTER ON THE KCS 55A DIRECTIONAL GYROSCOPE, COUPLED TO A KNS 80 NAV SYS, WERE ROUGHLY 180 DEGS OFF. I RECALLED THAT THIS HAD HAPPENED AT LEAST ONCE BEFORE IN THE 14 YRS I HAD USED THIS INST AND HAD SOON CORRECTED ITSELF, SO FELT NO GREAT CONCERN, PARTICULARLY SINCE I HAD ANOTHER NAV/COM AND A LORAN C ABOARD, ALTHOUGH NEITHER OF THESE INSTS WAS ON LINE AT THE TIME. THE DME OF THE KNS 80 WAS OPERATIONAL AND I CONCLUDED, ERRONEOUSLY, THAT I COULD NAVIGATE BY USING THE RECIPROCAL OF THE INDICATED HDG. AS WE CLBED 'ON COURSE' TO OUR CRUISING ALT OF 11500 FT, I ATTEMPTED TO CONTACT ZAB ON THE FREQ FOR THAT AREA SHOWN ON THE CHART, BUT WAS UNABLE TO DO SO, ALTHOUGH I WAS RECEIVING THEIR XMISSIONS. APPROX 1/2 WAY TO NEWMAN VOR THE LORAN C, WHICH HAD BEEN LARGELY INOPERABLE ACROSS NEW MEXICO AND ARIZONA DUE TO 'BAD GEOMETRY,' FINALLY CAME ON LINE AND SHOWED US ABOUT 8 NAUTICAL MI S OF COURSE. I FINALLY CONTACTED ZAB WITH THE ASSISTANCE OF THE CREW OF AN AIRLINER AND ADVISED THEM OF OUR SIT AND ASKED FOR ASSISTANCE. THE ALBUQUERQUE CTLR, THROUGH A SERIES OF STANDARD RATE TURNS, LOCATED US APPROX 15 NM S OF COURSE AND ESTABLISHED US ON A COURSE TO EL PASO ARPT, WHERE WE PLANNED TO LAND AND SEEK ASSISTANCE WITH OUR RADIOS. AT THIS TIME I FINALLY GLANCED AT THE DIGITAL VOLTMETER AND NOTED THAT IT SHOWED BTWN 11 AND 12 VOLTS. I CYCLED THE ALTERNATOR SWITCH AND THE VOLTMETER SHOWED 14 PLUS VOLTS AND THE DIRECTIONAL GYROSCOPE, AND OTHER EQUIP, CAME ON LINE. I ADVISED CTR AND WAS HANDED OFF TO EL PASO APCH CTL. I TUNED IN TO EL PASO VOR AND ASKED THE CTLR TO VERIFY OUR BEARING AND DISTANCE FROM THE VOR, WHICH HE DID. I THEN TUNED IN HUDSPETH VOR, THE NEXT WAYPOINT ON OUR COURSE, AND UPON RECEIVING IT ADVISED EL PASO THAT WE WOULD PROCEED TO OUR DEST, WHICH WE DID WITHOUT FURTHER INCIDENT. I LATER CONSULTED WITH MY AVIONICS SPECIALIST AND WE AGREED THAT OUR RADIO PROBS PROBABLY RESULTED FROM THE LOW VOLTAGE. HE ALSO SHOWED ME HOW TO DISENGAGE THE 'SLAVED' MODE OF THE KCS 55A AND THAT ONCE IN NORMAL MODE THE DISPLAY COULD BE MOVED TO THE DESIRED POS. HE ALSO POINTED THAT IN THE REVERSED POS SO CALLED 'REVERSE NEEDLE SENSING' WOULD BE REQUIRED TO USE THE INST FOR NAV. HE ALSO CHKED OUR MAGNETIC COMPASS, WHICH BOTH MY WIFE AND I HAD TRIED UNSUCCESSFULLY TO READ AS A CHK OF OUR HDG, AND WE CONCLUDED THAT, ALTHOUGH PART OF THE PROB HAD BEEN DUE TO THE LIGHT TO MODERATE TURB IN WHICH WE WERE OPERATING, THE LIQUID IN THE COMPASS DID SHOW EVIDENCE OF CONTAMINATION AND THAT POSSIBLY THE INST WAS NOT LEVEL IN FLT AND SHOULD BE THOROUGHLY CHKED AND SERVICED. SOME OF THE CONCLUSIONS I HAVE SO FAR REACHED AS A RESULT OF THE ABOVE ARE, FIRST, THAT IN SPITE OF ALL DISTRS, IT IS ABSOLUTELY ESSENTIAL TO CONTINUE YOUR 'NORMAL SCAN,' WHICH I OBVIOUSLY FAILED TO DO, SINCE I HAD NO RECOLLECTION OF ONCE LOOKING AT THE VOLTMETER UNTIL THE SIT WAS LARGELY RESOLVED, AND THAT IT IS VERY EASY TO FORGET ALL WE ONCE KNEW ABOUT THE 'TOOLS' WE WORK WITH, PARTICULARLY IF THEY ARE TROUBLE FREE. ALSO, THAT WE SHOULD REGULARLY REVIEW THE OPERATIONAL FACTORS OF ALL THE INSTS WE SO COMPLETELY RELY ON, AND, FINALLY, THAT EVEN AN INST AS MUNDANE AS THE MAGNETIC COMPASS CAN BE VERY IMPORTANT IF THE MORE SOPHISTICATED ONES FAIL.

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.