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A widebody transport fixed wing commercial aircraft was dispatched overwater with 1 of 2 GPS system inoperative.
| Attributes | |
| ACN | 374614 |
| Time | |
| Date | 199707 |
| Day | Thu |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | atc facility : kul |
| State Reference | FO |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other |
| Flight Phase | cruise other |
| Route In Use | enroute airway : kul |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 90 flight time total : 20000 flight time type : 12000 |
| ASRS Report | 374614 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : commercial pilot : instrument |
| Events | |
| Anomaly | aircraft equipment problem : less severe non adherence : published procedure non adherence : far other anomaly other |
| Independent Detector | other flight crewa other other : unspecified cockpit |
| Resolutory Action | none taken : anomaly accepted |
| Consequence | Other |
| Supplementary | |
| Air Traffic Incident | other |
Narrative:
#1 GPS unit indicated an antennae problem. The unit continued to operate normally in dead reckoning mode and with updates over chkpoints with the #2 GPS, it was very accurate. The question came up while on the ground if we would be legal to fly the aircraft back to mnl. We consulted our manuals and they were very vague and did not give us any clear cut direction. We contacted maintenance control and our dispatch and both informed us it was legal to depart. I was still uncertain, but due to the accuracy of the unit in dead reckoning and the fact that the WX was perfect with virtually no wind at altitude, I felt there would be no compromise of safety and that the flight could be completed normally. We did complete the flight routinely, with no problems whatsoever. However, after scrutinizing the manuals further, there is a possibility that both units must be in normal operating condition, but I still am not sure.
Original NASA ASRS Text
Title: A WDB FIXED WING COMMERCIAL ACFT WAS DISPATCHED OVERWATER WITH 1 OF 2 GPS SYS INOP.
Narrative: #1 GPS UNIT INDICATED AN ANTENNAE PROB. THE UNIT CONTINUED TO OPERATE NORMALLY IN DEAD RECKONING MODE AND WITH UPDATES OVER CHKPOINTS WITH THE #2 GPS, IT WAS VERY ACCURATE. THE QUESTION CAME UP WHILE ON THE GND IF WE WOULD BE LEGAL TO FLY THE ACFT BACK TO MNL. WE CONSULTED OUR MANUALS AND THEY WERE VERY VAGUE AND DID NOT GIVE US ANY CLR CUT DIRECTION. WE CONTACTED MAINT CTL AND OUR DISPATCH AND BOTH INFORMED US IT WAS LEGAL TO DEPART. I WAS STILL UNCERTAIN, BUT DUE TO THE ACCURACY OF THE UNIT IN DEAD RECKONING AND THE FACT THAT THE WX WAS PERFECT WITH VIRTUALLY NO WIND AT ALT, I FELT THERE WOULD BE NO COMPROMISE OF SAFETY AND THAT THE FLT COULD BE COMPLETED NORMALLY. WE DID COMPLETE THE FLT ROUTINELY, WITH NO PROBS WHATSOEVER. HOWEVER, AFTER SCRUTINIZING THE MANUALS FURTHER, THERE IS A POSSIBILITY THAT BOTH UNITS MUST BE IN NORMAL OPERATING CONDITION, BUT I STILL AM NOT SURE.
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.