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NDB beacon unreliable. Flight crew reverted to dead reckoning and at barow were advised by ARTCC ZHU they were 20 miles south of course.
| Attributes | |
| ACN | 174227 |
| Time | |
| Date | 199103 |
| Day | Fri |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : gls |
| State Reference | TX |
| Altitude | msl bound lower : 33000 msl bound upper : 33000 |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zhu artcc : zhn |
| Operator | common carrier : air carrier |
| Make Model Name | Large Transport, Low Wing, 3 Turbojet Eng |
| Navigation In Use | other ndb |
| Flight Phase | cruise other |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : commercial pilot : instrument pilot : atp |
| Experience | flight time last 90 days : 50 flight time total : 5500 flight time type : 2000 |
| ASRS Report | 174227 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : instrument pilot : commercial pilot : atp |
| Experience | flight time last 90 days : 240 flight time total : 15000 flight time type : 900 |
| ASRS Report | 174432 |
| Events | |
| Anomaly | aircraft equipment problem : less severe non adherence : far non adherence : clearance other spatial deviation |
| Independent Detector | other controllera |
| Resolutory Action | flight crew : became reoriented |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
Flight from cun to iah, 419 mi from gls beacon (alard intersection xx). We were just beyond range of all VOR navigation facs (mid cun czm). We were told by merida center to call houston at barow. At this point, the gls beacon was unreliable swinging 10-15 degrees. We went into dead reckoning procedures using our flight plan. Within the next 2 or 3 mins, we got a comparator warning. The compass system were checked and we found more than 6 degrees different between the captain and first officer's gyro system. We rest the compass system a few times with the wet compass. At barow intersection inbound to iah, we were informed by center that we were 30 mi so. From this point we were able to navigation direct to sabine VOR and into iah west/O event. We wrote up the compass problem in the maintenance log upon landing.
Original NASA ASRS Text
Title: NDB BEACON UNRELIABLE. FLT CREW REVERTED TO DEAD RECKONING AND AT BAROW WERE ADVISED BY ARTCC ZHU THEY WERE 20 MILES SOUTH OF COURSE.
Narrative: FLT FROM CUN TO IAH, 419 MI FROM GLS BEACON (ALARD INTXN XX). WE WERE JUST BEYOND RANGE OF ALL VOR NAV FACS (MID CUN CZM). WE WERE TOLD BY MERIDA CENTER TO CALL HOUSTON AT BAROW. AT THIS POINT, THE GLS BEACON WAS UNRELIABLE SWINGING 10-15 DEGS. WE WENT INTO DEAD RECKONING PROCS USING OUR FLT PLAN. WITHIN THE NEXT 2 OR 3 MINS, WE GOT A COMPARATOR WARNING. THE COMPASS SYS WERE CHKED AND WE FOUND MORE THAN 6 DEGS DIFFERENT BTWN THE CAPT AND F/O'S GYRO SYS. WE REST THE COMPASS SYS A FEW TIMES WITH THE WET COMPASS. AT BAROW INTXN INBND TO IAH, WE WERE INFORMED BY CENTER THAT WE WERE 30 MI SO. FROM THIS POINT WE WERE ABLE TO NAV DIRECT TO SABINE VOR AND INTO IAH W/O EVENT. WE WROTE UP THE COMPASS PROB IN THE MAINT LOG UPON LNDG.
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.