Narrative:

Flight departed gzs at approximately XA00 CDT in VFR conditions on IFR flight plan direct tcl at 6000 ft MSL, proceeding uneventfully until approximately 40 NM northeast of crimson VOR on 020 degree radial, when intermittent, erratic swings of #1 VOR indicator began to occur. Switched #2 VOR to crimson and noticed same behavior, both indicators fluctuating in synchronization. Aircraft was over rough terrain and a broken stratus layer at this time, so it was suspected that disturbances were due to terrain and/or WX since identical simultaneous fluctuations seen on both VOR's were seen. Fluctuations diminished about 15 NM north of crimson, appearing to validate suspicions that they were WX or terrain related. Aircraft was soon cleared by bhm approach to proceed to tuske LOM, the initial approach fix for the ILS runway 4 approach at tcl, and hold at 3000 ft MSL on the localizer. Navigation to tuske was accomplished using the localizer back course and the crimson 225 degree radial. While en route to tuske flight was cleared for the approach by bhm, and approach was attempted after performing procedure turn. Due to apparently erroneous indications from localizer, aircraft emerged from stratus layer at 1900 ft MSL about 3 mi east of ILS runway 4 LOM, which led to misident of runway 29 as runway 4. When alerted by tuscaloosa tower that our aircraft was not visible in the vicinity of runway 4 approach, xchk of directional gyro and compass revealed true position to be southeast of field instead of southwest. Tower stated that another aircraft was maneuvering in our vicinity, which was then visually identified at 11 O'clock position opposite direction, about 1000 ft ahead and 100 ft higher altitude. Evasive action taken by turning right and descending, resulting miss distance about 500 ft. Now in visual conditions, aircraft then was cleared to land on runway 4 and flight terminated without further difficulty. In retrospect, some consideration should have been given to descending below the broken stratus layer through a hole and performing a visual approach once the VOR receivers began to fluctuate, rather than attempting the localizer/LOM intersection hold and ILS 4 approach with questionable equipment, since the ceiling at tcl was 1400 ft with good visibility. Because the erratic behavior of the vors initially occurred over rough terrain and diminished as the range to crimson decreased, it led the crew to erroneously assume that the problem was terrain related and that the receivers were ok. Also, a GPS which was being used for en route navigation could have been used as a backup to reach tuske and hold, but this was not done because this receiver is an older model and difficult to program, and doing so in-flight can be a major distraction. Finally, a portable GPS was available, but was not used because it would have been difficult to retrieve from the rear of the aircraft and get set up for this purpose. A compounding factor in this occurrence is the lack of adequate radar coverage in the tcl area, which relies on the nearby bhm facility for this service. Radar coverage of our flight was lost when we were cleared to 3000 ft MSL. If a local approach radar were installed at tcl, navigation errors by aircraft could be quickly detected by ATC and pilots notified in time to avoid potential conflicts. Also, this would make possible radar vectoring of aircraft to the final ILS/localizer approachs, which would reduce the possibility of navigation error en route to the IAF and make possible better aircraft separation control under all conditions. Supplemental information from acn 596802: while flying on an instrument flight plan, I became disoriented and totally blew an approach which led to the near miss. I believe the actual chain of events starting point was the lack of sleep the night before, I was also recovering from a case of strep throat the week before. As I approached tuscaloosa, I did not believe the vors weren't functioning correctly. As the controllers had told me to hold on the localizer, I thought I knew where I was and could intercept the localizer and hold as directed. As I descended into a cloud layer I became disoriented and concerned the localizer wasn't functioning properly. However, instead of asking for help, I saw the ground through holes in the clouds and continued on toward where I knew the airport to be. I was nowhere close to being on the approach and as a result, interfered with the approach of another aircraft. I think contributing factors were: 1) my health and lack of mental awareness. 2) being unfamiliar with the airplane and its idiosyncrasies. 3) unwillingness to ask for help when I realized I was disoriented. At any point, I could have asked ATC for help but did not. I will never do this again.

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Original NASA ASRS Text

Title: PA23 PLT AND PLT PAX HAD LESS THAN LEGAL SEPARATION IN TCL CLASS D AIRSPACE, AFTER THE PLT OF THE PA23 LINED UP FOR THE WRONG RWY.

Narrative: FLT DEPARTED GZS AT APPROX XA00 CDT IN VFR CONDITIONS ON IFR FLT PLAN DIRECT TCL AT 6000 FT MSL, PROCEEDING UNEVENTFULLY UNTIL APPROX 40 NM NE OF CRIMSON VOR ON 020 DEG RADIAL, WHEN INTERMITTENT, ERRATIC SWINGS OF #1 VOR INDICATOR BEGAN TO OCCUR. SWITCHED #2 VOR TO CRIMSON AND NOTICED SAME BEHAVIOR, BOTH INDICATORS FLUCTUATING IN SYNCHRONIZATION. ACFT WAS OVER ROUGH TERRAIN AND A BROKEN STRATUS LAYER AT THIS TIME, SO IT WAS SUSPECTED THAT DISTURBANCES WERE DUE TO TERRAIN AND/OR WX SINCE IDENTICAL SIMULTANEOUS FLUCTUATIONS SEEN ON BOTH VOR'S WERE SEEN. FLUCTUATIONS DIMINISHED ABOUT 15 NM N OF CRIMSON, APPEARING TO VALIDATE SUSPICIONS THAT THEY WERE WX OR TERRAIN RELATED. ACFT WAS SOON CLRED BY BHM APCH TO PROCEED TO TUSKE LOM, THE INITIAL APCH FIX FOR THE ILS RWY 4 APCH AT TCL, AND HOLD AT 3000 FT MSL ON THE LOC. NAV TO TUSKE WAS ACCOMPLISHED USING THE LOC BACK COURSE AND THE CRIMSON 225 DEG RADIAL. WHILE ENRTE TO TUSKE FLT WAS CLRED FOR THE APCH BY BHM, AND APCH WAS ATTEMPTED AFTER PERFORMING PROC TURN. DUE TO APPARENTLY ERRONEOUS INDICATIONS FROM LOC, ACFT EMERGED FROM STRATUS LAYER AT 1900 FT MSL ABOUT 3 MI E OF ILS RWY 4 LOM, WHICH LED TO MISIDENT OF RWY 29 AS RWY 4. WHEN ALERTED BY TUSCALOOSA TWR THAT OUR ACFT WAS NOT VISIBLE IN THE VICINITY OF RWY 4 APCH, XCHK OF DIRECTIONAL GYRO AND COMPASS REVEALED TRUE POS TO BE SE OF FIELD INSTEAD OF SW. TWR STATED THAT ANOTHER ACFT WAS MANEUVERING IN OUR VICINITY, WHICH WAS THEN VISUALLY IDENTIFIED AT 11 O'CLOCK POS OPPOSITE DIRECTION, ABOUT 1000 FT AHEAD AND 100 FT HIGHER ALT. EVASIVE ACTION TAKEN BY TURNING R AND DSNDING, RESULTING MISS DISTANCE ABOUT 500 FT. NOW IN VISUAL CONDITIONS, ACFT THEN WAS CLRED TO LAND ON RWY 4 AND FLT TERMINATED WITHOUT FURTHER DIFFICULTY. IN RETROSPECT, SOME CONSIDERATION SHOULD HAVE BEEN GIVEN TO DSNDING BELOW THE BROKEN STRATUS LAYER THROUGH A HOLE AND PERFORMING A VISUAL APCH ONCE THE VOR RECEIVERS BEGAN TO FLUCTUATE, RATHER THAN ATTEMPTING THE LOC/LOM INTXN HOLD AND ILS 4 APCH WITH QUESTIONABLE EQUIP, SINCE THE CEILING AT TCL WAS 1400 FT WITH GOOD VISIBILITY. BECAUSE THE ERRATIC BEHAVIOR OF THE VORS INITIALLY OCCURRED OVER ROUGH TERRAIN AND DIMINISHED AS THE RANGE TO CRIMSON DECREASED, IT LED THE CREW TO ERRONEOUSLY ASSUME THAT THE PROB WAS TERRAIN RELATED AND THAT THE RECEIVERS WERE OK. ALSO, A GPS WHICH WAS BEING USED FOR ENRTE NAV COULD HAVE BEEN USED AS A BACKUP TO REACH TUSKE AND HOLD, BUT THIS WAS NOT DONE BECAUSE THIS RECEIVER IS AN OLDER MODEL AND DIFFICULT TO PROGRAM, AND DOING SO INFLT CAN BE A MAJOR DISTR. FINALLY, A PORTABLE GPS WAS AVAILABLE, BUT WAS NOT USED BECAUSE IT WOULD HAVE BEEN DIFFICULT TO RETRIEVE FROM THE REAR OF THE ACFT AND GET SET UP FOR THIS PURPOSE. A COMPOUNDING FACTOR IN THIS OCCURRENCE IS THE LACK OF ADEQUATE RADAR COVERAGE IN THE TCL AREA, WHICH RELIES ON THE NEARBY BHM FACILITY FOR THIS SVC. RADAR COVERAGE OF OUR FLT WAS LOST WHEN WE WERE CLRED TO 3000 FT MSL. IF A LCL APCH RADAR WERE INSTALLED AT TCL, NAV ERRORS BY ACFT COULD BE QUICKLY DETECTED BY ATC AND PLTS NOTIFIED IN TIME TO AVOID POTENTIAL CONFLICTS. ALSO, THIS WOULD MAKE POSSIBLE RADAR VECTORING OF ACFT TO THE FINAL ILS/LOC APCHS, WHICH WOULD REDUCE THE POSSIBILITY OF NAV ERROR ENRTE TO THE IAF AND MAKE POSSIBLE BETTER ACFT SEPARATION CTL UNDER ALL CONDITIONS. SUPPLEMENTAL INFO FROM ACN 596802: WHILE FLYING ON AN INST FLT PLAN, I BECAME DISORIENTED AND TOTALLY BLEW AN APCH WHICH LED TO THE NEAR MISS. I BELIEVE THE ACTUAL CHAIN OF EVENTS STARTING POINT WAS THE LACK OF SLEEP THE NIGHT BEFORE, I WAS ALSO RECOVERING FROM A CASE OF STREP THROAT THE WK BEFORE. AS I APCHED TUSCALOOSA, I DID NOT BELIEVE THE VORS WEREN'T FUNCTIONING CORRECTLY. AS THE CTLRS HAD TOLD ME TO HOLD ON THE LOC, I THOUGHT I KNEW WHERE I WAS AND COULD INTERCEPT THE LOC AND HOLD AS DIRECTED. AS I DSNDED INTO A CLOUD LAYER I BECAME DISORIENTED AND CONCERNED THE LOC WASN'T FUNCTIONING PROPERLY. HOWEVER, INSTEAD OF ASKING FOR HELP, I SAW THE GND THROUGH HOLES IN THE CLOUDS AND CONTINUED ON TOWARD WHERE I KNEW THE ARPT TO BE. I WAS NOWHERE CLOSE TO BEING ON THE APCH AND AS A RESULT, INTERFERED WITH THE APCH OF ANOTHER ACFT. I THINK CONTRIBUTING FACTORS WERE: 1) MY HEALTH AND LACK OF MENTAL AWARENESS. 2) BEING UNFAMILIAR WITH THE AIRPLANE AND ITS IDIOSYNCRASIES. 3) UNWILLINGNESS TO ASK FOR HELP WHEN I REALIZED I WAS DISORIENTED. AT ANY POINT, I COULD HAVE ASKED ATC FOR HELP BUT DID NOT. I WILL NEVER DO THIS AGAIN.

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.