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37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
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A DC10 just west of lax, bound of hnl, diverts to lax when their GPS units display a navigation problem message.
| Attributes | |
| ACN | 407244 |
| Time | |
| Date | 199806 |
| Day | Sat |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : lax |
| State Reference | CA |
| Altitude | msl bound lower : 33000 msl bound upper : 33000 |
| Environment | |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zla |
| Operator | common carrier : air carrier |
| Make Model Name | DC-10 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other |
| Flight Phase | cruise other other |
| Route In Use | enroute : pacific |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| ASRS Report | 407244 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : instrument pilot : commercial |
| Events | |
| Anomaly | aircraft equipment problem : critical other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other flight crewa |
| Resolutory Action | other |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | other |
Narrative:
During flight, both GPS units gave an alert message of 'unable rnp' followed by a 'dr' message. After consulting the operations manual, we began to closely monitor both GPS units and xchk our position with available navaids en route. We noticed a slow divergence and navigation performance error developing on both units. Between lax and dinty and conferring with ZLA, it was obvious that our navigation units were unacceptable for oceanic flight. The navigation units had a previous error history in the error log of multiple multifunction control display unit failures. We attempted to reset each unit using the previous write-ups and the operations manual as reference. Neither GPS unit responded properly. The decision to dump fuel and land at lax was made and coordinated with ATC, dispatch and technical services. Lax maintenance replaced both npu units and reloaded the software. The flight from lax to hnl was uneventful and the performance of both GPS units was normal.
Original NASA ASRS Text
Title: A DC10 JUST W OF LAX, BOUND OF HNL, DIVERTS TO LAX WHEN THEIR GPS UNITS DISPLAY A NAV PROB MESSAGE.
Narrative: DURING FLT, BOTH GPS UNITS GAVE AN ALERT MESSAGE OF 'UNABLE RNP' FOLLOWED BY A 'DR' MESSAGE. AFTER CONSULTING THE OPS MANUAL, WE BEGAN TO CLOSELY MONITOR BOTH GPS UNITS AND XCHK OUR POS WITH AVAILABLE NAVAIDS ENRTE. WE NOTICED A SLOW DIVERGENCE AND NAV PERFORMANCE ERROR DEVELOPING ON BOTH UNITS. BTWN LAX AND DINTY AND CONFERRING WITH ZLA, IT WAS OBVIOUS THAT OUR NAV UNITS WERE UNACCEPTABLE FOR OCEANIC FLT. THE NAV UNITS HAD A PREVIOUS ERROR HISTORY IN THE ERROR LOG OF MULTIPLE MULTIFUNCTION CTL DISPLAY UNIT FAILURES. WE ATTEMPTED TO RESET EACH UNIT USING THE PREVIOUS WRITE-UPS AND THE OPS MANUAL AS REF. NEITHER GPS UNIT RESPONDED PROPERLY. THE DECISION TO DUMP FUEL AND LAND AT LAX WAS MADE AND COORDINATED WITH ATC, DISPATCH AND TECHNICAL SVCS. LAX MAINT REPLACED BOTH NPU UNITS AND RELOADED THE SOFTWARE. THE FLT FROM LAX TO HNL WAS UNEVENTFUL AND THE PERFORMANCE OF BOTH GPS UNITS WAS NORMAL.
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.