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Flight crew of medium large transport air carrier aircraft deviated from assigned track due to a malfunctioned navigation computer.
| Attributes | |
| ACN | 247589 |
| Time | |
| Date | 199307 |
| Day | Wed |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : cydf |
| State Reference | NF |
| Altitude | msl bound lower : 43000 msl bound upper : 43000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : czqx |
| Operator | general aviation : corporate |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Navigation In Use | Other Other |
| Flight Phase | cruise other |
| Route In Use | enroute : atlantic enroute : other oceanic enroute airway : czqx |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | Other |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 100 flight time total : 11000 flight time type : 950 |
| ASRS Report | 247589 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : instrument pilot : commercial |
| Events | |
| Anomaly | aircraft equipment problem : less severe non adherence : clearance other anomaly other other spatial deviation |
| Independent Detector | atc equipment other atc equipment : unspecified other controllera |
| Resolutory Action | controller : issued new clearance other |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | Pilot Deviation |
Narrative:
Oceanic crossing amsterdam-gander (medium large transport cpr jet) cleared to FL430 crossing from eham-cyqx. Programmed flight plan into GNS sto amsterdam with associated latitude/long coordinates. Uneventful crossing until last fix, 51.00.0N X 050.00.0W. Established VHF communication with gander center and reported 51.00.0N and 050.00.0W. Controller asked aircraft verify position upon radar. Said we were at 50N instead of 51N. Re-verified position at time and we were at 50N instead of 51N as cleared. Aircraft had just had VLF control head replaced with updated version at beginning of flight 1 week prior. We had difficulty during 6 previous flts with VLF and GPS going to br repeatedly and were taking aircraft back to maintenance after completion of flight to have unit looked at. Upon subsequent programming and checking of unit, position entered shifted 2 of 3 times entered, and waypoints moved after programming. Unit and processor was removed by manufacturer for test after severe problems were subsequently found with installation. Suggestion: re-verify fix and position with other stand alone units in aircraft. In this instance the GNS/GPS instruction had 2 stand alone INS units slaved to it for programming route fixes.
Original NASA ASRS Text
Title: FLC OF MLG ACR ACFT DEVIATED FROM ASSIGNED TRACK DUE TO A MALFUNCTIONED NAV COMPUTER.
Narrative: OCEANIC XING AMSTERDAM-GANDER (MLG CPR JET) CLRED TO FL430 XING FROM EHAM-CYQX. PROGRAMMED FLT PLAN INTO GNS STO AMSTERDAM WITH ASSOCIATED LAT/LONG COORDINATES. UNEVENTFUL XING UNTIL LAST FIX, 51.00.0N X 050.00.0W. ESTABLISHED VHF COM WITH GANDER CTR AND RPTED 51.00.0N AND 050.00.0W. CTLR ASKED ACFT VERIFY POS UPON RADAR. SAID WE WERE AT 50N INSTEAD OF 51N. RE-VERIFIED POS AT TIME AND WE WERE AT 50N INSTEAD OF 51N AS CLRED. ACFT HAD JUST HAD VLF CTL HEAD REPLACED WITH UPDATED VERSION AT BEGINNING OF FLT 1 WK PRIOR. WE HAD DIFFICULTY DURING 6 PREVIOUS FLTS WITH VLF AND GPS GOING TO BR REPEATEDLY AND WERE TAKING ACFT BACK TO MAINT AFTER COMPLETION OF FLT TO HAVE UNIT LOOKED AT. UPON SUBSEQUENT PROGRAMMING AND CHKING OF UNIT, POS ENTERED SHIFTED 2 OF 3 TIMES ENTERED, AND WAYPOINTS MOVED AFTER PROGRAMMING. UNIT AND PROCESSOR WAS REMOVED BY MANUFACTURER FOR TEST AFTER SEVERE PROBS WERE SUBSEQUENTLY FOUND WITH INSTALLATION. SUGGESTION: RE-VERIFY FIX AND POS WITH OTHER STAND ALONE UNITS IN ACFT. IN THIS INSTANCE THE GNS/GPS INSTRUCTION HAD 2 STAND ALONE INS UNITS SLAVED TO IT FOR PROGRAMMING RTE FIXES.
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.