Widebody Transport
Flight Crew Air Transport Pilot (ATP)
Distraction; Confusion; Communication Breakdown; Troubleshooting; Situational Awareness
Aircraft Equipment Problem Less Severe
Aircraft Equipment Problem Dissipated; Flight Crew Became Reoriented
Company Policy; Environment - Non Weather Related
Three to four minutes after departure from RKSI Runway 33L; our flight was climbing through 3;500 FT MSL on the SEL1C departure. During the right turn through north approaching the SUPAN waypoint; and approximately 12 NM south of the North Korean border; we got a Sensor Fail MCDU alert. When we checked; both the GNS 1 and 2 systems indicated fail. Approximately 30 seconds later both alerts went away. The aircraft navigation system simply degraded to INS and the magenta line did not vary at all. We continued on and assumed we had a recurrence of the same GPS failure mode that the inbound crew had reported and RKSI Maintenance had signed off. The alert was resolved so quickly that we did not feel any need to inform ATC of the issue. No further issues with the GNS were noted during the flight; and a maintenance discrepancy was written up upon landing. Again; Maintenance was unable to find any problems and the system was signed off. This report is being written because I just read that there have been numerous cases of suspected North Korean jamming of GPS signals affecting commercial aircraft flying into and out of RKSI Airport. I now suspect both we and the inbound crew were the victims of this North Korean jamming. I called the Chief Pilot who referred me to the Duty Officer to inform him of my suspicion that we had had our GPS signal jammed when departing out of RKSI. The Duty Officer informed me that management was aware of this issue and would follow up on why we; the operating crew; had not been alerted to this threat to flight safety. He suggested I write report to get this information on the record. There was an International FIR Boundary NOTAM issued earlier; concerning the threat of North Korean GPS jamming. This NOTAM did not appear in the weather/NOTAM paperwork for our flight; nor is it available today using the Weather-by-Route portion of the Weather site on the Company Pilot website. Since FIR Boundary NOTAMs are not usually part of the weather-by-route NOTAMs that flight crews are given as part of their flight paperwork preparation; Management must ensure that this type of flight safety threat FIR Boundary NOTAM is made available to all crews flying into and out of RKSI.
[Narrative #2 contained no additional information.]
After departing RKSI on the SEL1C SID north; both the aircraft's GPS units indicated failure but returned to normal shortly thereafter. Days later the crew was informed North Korea was jamming GPS signals but no crew alert was issued.