Narrative:

Over [country name] we received an EICAS message: ads-B right out. We ran the annunciated checklist and essentially; it said to select the right side. We did this and shortly thereafter (perhaps a few minutes) we received another EICAS message: ads-B left out. We sent an frm with both ads-B left&right failed. Ten minutes later we received another EICAS message: ter xx_48 os and responded an frm. Eight minutes later we received EICAS message: global positioning system failure (this was an automatic log.) approximately 15 minutes later and while we were dealing with this; we received another EICAS message: status left global positioning system unit failure. At this point; I recalled both resting international relief officer's to the cockpit as we had several systems failing for no apparent reason. We made a call to [air traffic] control and asked if we were in radar contact which we were. We advised [air traffic control] that we might need radar vectors as we were having navigation issues. Just before both international relief officer's came up to the cockpit and at approximately we received EICAS message right EICAS status right global positioning system unit failure. I advised both international relief officer's of the situation. Flying first officer was flying the plane and communicating with ATC; I advised both international relief officer's that we may need to divert and if so; please brief the diversion guide. Approximately 20 minutes later we received EICAS message advisory: ws has determined that horizontal position uncertainty exceeds limit. I used my resources by calling dispatch. At my request; we got maintenance control on the three-way call. Neither dispatch nor maintenance control had a firm answer why we lost ads-B (both channels) first and then both units followed by navigation unable EICAS and runway system EICAS. In addition; we had the following status messages: runway system; ads-B out right; ads-B out left. Maintenance control recommended we call XXX; but they did not have an answer as to why these systems were failing. Dispatch supervisor finally got on the call and between the eight participants we were trying to come up with a logical solution. Dispatch supervisor finally asked if we saw a NOTAM on page 39 of the package that addresses ads outages. Because we did not receive the new route and flight plan package in a timely fashion (we finally received this minutes from push back) and because we were up against the max cco time getting out of XXX; we were unable to review the entire package of NOTAMS other than the applicable NOTAMS for takeoff. The applicable NOTAM was actually on page 41 and it addressed many locations of ads and GPS outages including but not limited to: israel; turkey; iran; nicosia; syria; etc. As we were discussing these items; our systems started to return to service by themselves. While on a five-way call; all of the systems mentioned above had returned to full service. One has to wonder why all the participants did not know about this outage since we were flight planned through this airspace? We were very fortunate that XXX found this obscure and out of place NOTAM which was very crucial for safe flight. My response was to put this NOTAM in the 'dispatcher remarks' on the first page of the flight plan. Also; they need to put out a pilot bulletin making all pilots aware of traversing through this airspace and the consequences. Side note: a bulletin pilot briefing was issued as a direct response to my request. Also note; captain XXX did review the pilot briefing and pertinent information guide prior to flight and nowhere in the 9 pages does it mention the ads and GPS potential failure. A lack of either a routine NOTAM; briefing or bulletin almost resulted in an unnecessary fuel dump and diversion.

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Original NASA ASRS Text

Title: Air carrier Captain reported GPS equipment failure alerts. While evaluating the alerts with the flight crew and operations personnel; a NOTAM detailing GPS outages for the area was discovered.

Narrative: Over [country name] we received an EICAS Message: ADS-B R OUT. We ran the Annunciated Checklist and essentially; it said to select the right side. We did this and shortly thereafter (perhaps a few minutes) we received another EICAS Message: ADS-B L OUT. We sent an FRM with both ADS-B L&R Failed. Ten minutes later we received another EICAS Message: TER XX_48 OS and responded an FRM. Eight minutes later we received EICAS Message: Global Positioning System Failure (This was an Automatic Log.) Approximately 15 minutes later and while we were dealing with this; we received another EICAS Message: status left global positioning system unit failure. At this point; I recalled both resting IRO's to the cockpit as we had several systems failing for no apparent reason. We made a call to [Air Traffic] Control and asked if we were in Radar Contact which we were. We advised [Air traffic Control] that we might need Radar Vectors as we were having navigation issues. Just before both IRO's came up to the cockpit and at approximately we received EICAS Message R EICAS status right global positioning system unit failure. I advised both IRO's of the situation. Flying First Officer was flying the plane and communicating with ATC; I advised both IRO's that we may need to divert and if so; please brief the Diversion Guide. Approximately 20 minutes later we received EICAS Message Advisory: WS has determined that horizontal position uncertainty exceeds limit. I used my resources by calling dispatch. At my request; we got Maintenance Control on the three-way call. Neither dispatch nor maintenance control had a firm answer why we lost ADS-B (both channels) first and then both units followed by NAV UNABLE EICAS and RUNWAY SYS EICAS. In addition; we had the following status messages: RUNWAY SYS; ADS-B OUT R; ADS-B OUT L. Maintenance Control recommended we call XXX; but they did not have an answer as to why these systems were failing. Dispatch Supervisor finally got on the call and between the eight participants we were trying to come up with a logical solution. Dispatch Supervisor finally asked if we saw a NOTAM on page 39 of the package that addresses ADS outages. Because we did not receive the new route and flight plan package in a timely fashion (we finally received this minutes from push back) and because we were up against the Max CCO time getting out of XXX; we were unable to review the entire package of NOTAMS other than the applicable NOTAMS for takeoff. The applicable NOTAM was actually on page 41 and it addressed many locations of ADS and GPS outages including but not limited to: Israel; Turkey; Iran; Nicosia; Syria; etc. As we were discussing these items; our systems started to return to service by themselves. While on a five-way call; all of the systems mentioned above had returned to full service. One has to wonder why all the participants did not know about this outage since we were flight planned through this airspace? We were very fortunate that XXX found this obscure and out of place NOTAM which was very crucial for safe flight. My response was to put this NOTAM in the 'Dispatcher Remarks' on the first page of the flight plan. Also; they need to put out a Pilot Bulletin making all pilots aware of traversing through this airspace and the consequences. Side note: A bulletin pilot briefing was issued as a direct response to my request. Also note; Captain XXX did review the pilot briefing and pertinent information guide prior to flight and nowhere in the 9 pages does it mention the ADS and GPS potential failure. A lack of either a routine NOTAM; briefing or bulletin almost resulted in an unnecessary fuel dump and diversion.

Data retrieved from NASA's ASRS site 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.