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A B757 flight crew is alerted by ATC of being 30 mi off desired track. ATC vectors corrected track error. On landing, FMS revealed 36 mi drift rate.
| Attributes | |
| ACN | 595771 |
| Time | |
| Date | 200310 |
| Day | Sun |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | navaid : zzz.vor |
| State Reference | US |
| Altitude | msl single value : 11000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zzz.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | B757 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other vortac |
| Flight Phase | descent : approach |
| Route In Use | arrival star : zzz |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 200 flight time total : 22500 flight time type : 1600 |
| ASRS Report | 595771 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Events | |
| Anomaly | aircraft equipment problem : critical other anomaly other other spatial deviation |
| Independent Detector | other controllera other flight crewa other flight crewb |
| Resolutory Action | aircraft : automation overrode flight crew controller : provided flight assist flight crew : returned to intended or assigned course |
| Consequence | other |
| Supplementary | |
| Problem Areas | Aircraft Flight Crew Human Performance |
| Primary Problem | Aircraft |
Narrative:
On descent into the ZZZ international airport on the ZZZ arrival, center informed us that our aircraft position was 30 NM southwest of the desired track needed to cross over the zzzzz intersection on the XXX arrival. The B757's FMC indicated, only intermittently, that the IRS's were in IRS navigation only. No other navigation system faults were displayed. Upon ATC's notification of our track error, I requested radar vectors from ATC to correct back to desired track. With ATC radar vectors and raw data selected, no further navigation track discrepancies were reported by ATC. With aircraft stopped at the gate in ZZZ, an FMS drift rate of 36 KTS was noted. The discrepancy was written up in the aircraft log, maintenance notified, and information passed on to the new flight crew assigned the aircraft. Note: the initial IRS was entered correctly and crosschecked by both captain and first officer.
Original NASA ASRS Text
Title: A B757 FLT CREW IS ALERTED BY ATC OF BEING 30 MI OFF DESIRED TRACK. ATC VECTORS CORRECTED TRACK ERROR. ON LNDG, FMS REVEALED 36 MI DRIFT RATE.
Narrative: ON DSCNT INTO THE ZZZ INTL ARPT ON THE ZZZ ARR, CTR INFORMED US THAT OUR ACFT POS WAS 30 NM SW OF THE DESIRED TRACK NEEDED TO CROSS OVER THE ZZZZZ INTXN ON THE XXX ARR. THE B757'S FMC INDICATED, ONLY INTERMITTENTLY, THAT THE IRS'S WERE IN IRS NAV ONLY. NO OTHER NAV SYS FAULTS WERE DISPLAYED. UPON ATC'S NOTIFICATION OF OUR TRACK ERROR, I REQUESTED RADAR VECTORS FROM ATC TO CORRECT BACK TO DESIRED TRACK. WITH ATC RADAR VECTORS AND RAW DATA SELECTED, NO FURTHER NAV TRACK DISCREPANCIES WERE RPTED BY ATC. WITH ACFT STOPPED AT THE GATE IN ZZZ, AN FMS DRIFT RATE OF 36 KTS WAS NOTED. THE DISCREPANCY WAS WRITTEN UP IN THE ACFT LOG, MAINT NOTIFIED, AND INFO PASSED ON TO THE NEW FLT CREW ASSIGNED THE ACFT. NOTE: THE INITIAL IRS WAS ENTERED CORRECTLY AND XCHKED BY BOTH CAPT AND FO.
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.