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INS errors increase to the point flight crew returns aircraft to departure station rather than fly over the atlantic with those errors.
| Attributes | |
| ACN | 299171 |
| Time | |
| Date | 199503 |
| Day | Thu |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | atc facility : yqx |
| State Reference | FO |
| Altitude | msl bound lower : 33000 msl bound upper : 33000 |
| Environment | |
| Flight Conditions | IMC |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | artcc : czqx |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise other |
| Route In Use | enroute : atlantic enroute airway : czqx |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : instrument pilot : cfi pilot : commercial pilot : flight engineer pilot : atp |
| Experience | flight time last 90 days : 210 flight time total : 18000 flight time type : 1500 |
| ASRS Report | 299171 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Events | |
| Anomaly | aircraft equipment problem : less severe other anomaly other other spatial deviation |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other flight crewa |
| Resolutory Action | controller : issued new clearance flight crew : became reoriented none taken : unable |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | other |
Narrative:
After coast out at gander VOR on a north atlantic track, INS #1, #2, and #3 began to drift about 15 NM off course. A course correction by gander radar back to course was made. All 3 units continued to show an error of about 15 NM. Decided to return to ewr due to questionable navigation performance on INS. Air carrier X ewr to rom. No far violation occurred. Track airspace was not violated. Center also advised X to return to domestic airspace. Flight landed at ewr without further incident. INS's #2 and #3 were found to be drifting excessively. INS's were rebooted by maintenance and checked ok. What caused the sudden drift is unknown.
Original NASA ASRS Text
Title: INS ERRORS INCREASE TO THE POINT FLC RETURNS ACFT TO DEP STATION RATHER THAN FLY OVER THE ATLANTIC WITH THOSE ERRORS.
Narrative: AFTER COAST OUT AT GANDER VOR ON A NORTH ATLANTIC TRACK, INS #1, #2, AND #3 BEGAN TO DRIFT ABOUT 15 NM OFF COURSE. A COURSE CORRECTION BY GANDER RADAR BACK TO COURSE WAS MADE. ALL 3 UNITS CONTINUED TO SHOW AN ERROR OF ABOUT 15 NM. DECIDED TO RETURN TO EWR DUE TO QUESTIONABLE NAV PERFORMANCE ON INS. ACR X EWR TO ROM. NO FAR VIOLATION OCCURRED. TRACK AIRSPACE WAS NOT VIOLATED. CTR ALSO ADVISED X TO RETURN TO DOMESTIC AIRSPACE. FLT LANDED AT EWR WITHOUT FURTHER INCIDENT. INS'S #2 AND #3 WERE FOUND TO BE DRIFTING EXCESSIVELY. INS'S WERE REBOOTED BY MAINT AND CHKED OK. WHAT CAUSED THE SUDDEN DRIFT IS UNKNOWN.
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.