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An A300 dispatched with 1 IRU MEL'ed experience excessive navigation system drift rate resulting in vector navigation.
| Attributes | |
| ACN | 654389 |
| Time | |
| Date | 200504 |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : zzz.artcc |
| State Reference | FO |
| Altitude | msl single value : 34000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zzz.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | A300 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise : level |
| Route In Use | enroute : on vectors enroute : other oceanic |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : flight engineer pilot : commercial pilot : multi engine pilot : instrument pilot : private pilot : atp |
| Experience | flight time last 90 days : 200 flight time total : 10640 flight time type : 4000 |
| ASRS Report | 654389 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Events | |
| Anomaly | aircraft equipment problem : critical non adherence : clearance other anomaly other other spatial deviation |
| Independent Detector | other flight crewa |
| Resolutory Action | controller : provided flight assist flight crew : overcame equipment problem |
| Consequence | other |
| Supplementary | |
| Problem Areas | Aircraft |
| Primary Problem | Aircraft |
Narrative:
Aircraft IRU placarded inoperative; #3; dispatched. Remaining #1 and #2 IRU's contained a drift input from unknown source. No warnings or cautions. Navigation checks and verify position message revealed aircraft position off course 6 mi in 1 hour; 16 mi in 2 hours; 60 mi in 3 hours. Drift 67 mi total. ATC agencies advised; flight vectored only after updates failed.
Original NASA ASRS Text
Title: AN A300 DISPATCHED WITH 1 IRU MEL'ED EXPERIENCE EXCESSIVE NAV SYS DRIFT RATE RESULTING IN VECTOR NAV.
Narrative: ACFT IRU PLACARDED INOP; #3; DISPATCHED. REMAINING #1 AND #2 IRU'S CONTAINED A DRIFT INPUT FROM UNKNOWN SOURCE. NO WARNINGS OR CAUTIONS. NAV CHKS AND VERIFY POS MESSAGE REVEALED ACFT POS OFF COURSE 6 MI IN 1 HR; 16 MI IN 2 HRS; 60 MI IN 3 HRS. DRIFT 67 MI TOTAL. ATC AGENCIES ADVISED; FLT VECTORED ONLY AFTER UPDATES FAILED.
Data retrieved from NASA's ASRS site as of January 2009 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.