Date: 201904
Local time of day: 0601-1200
Location: LTAA.ARTCC, FO
Flight conditions: VMC
Light: Daylight
Aircraft: Widebody Transport
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Cruise
ATC / advisory: Center LTAA
Aircraft component: GPS & Other Satellite Navigation
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain
Reporter qualification: Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Human factors: Distraction; Troubleshooting; Confusion
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Aircraft Equipment Problem Dissipated; Flight Crew FLC complied w / Automation / Advisory
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: We experienced a GPS Loss of Signal/GPS Signal Interference for 6 minutes near the Turkey - Iraq border; between OTKEP and RATVO waypoints at FL370. Our navigation capability remained well within the required RNP (Required Navigation Performance). Initial indications were 'ADS-B OUT L' EICAS (Engine Indicating and Crew Alerting System) message and 'Inertial' on the NAV display. We complied with the Non Normal checklist.This was our first experience with a possible GPS jamming event. We referred to Bulletin XXX-XX-XX 'GPS Loss of Signal/GPS Signal Interference' to troubleshoot and prepare for possible navigation degradation.The GPS returned to normal operation after 6 minutes of signal loss. Communications from the company and crewmembers have identified this route area as typical for GPS interference. After block in we referred to the FOM (Flight Operations Manual) X.XX Mandatory Reports as referenced in the above-mentioned Bulletin. The table shows only a [Safety Report] and Security reports are mandatory. The AML (Aircraft Maintenance Logbook) entry box has no 'x.' Accordingly; I neglected to make an AML entry regarding the GPS interference.The cause of the loss of GPS was most likely due to jamming and/or interference.Neglecting to properly document and communicate the GPS issue was primarily due to my misreading of the GPS bulletin. In a rush to reference the technical part of the bulletin to assist in troubleshooting; I skimmed the administrative paragraphs and missed the 'A detailed AML write up is required for any GPS discrepancies even if the GPS function returns to normal.' I made the mistake of assuming that because the event was not caused by our equipment; an AML entry would not be required. The lack of an AML entry requirement in the FOM X.XX table contributed to my error. The bulletin IS controlling as it was issued subsequent to the current FOM. Additionally; this was our first GPS event experience.Our improper assumptions were additional causes. We assumed that a notification to ATC or [the Operations Center] was not necessary because we never had a loss of navigation capability and we had no aircraft system malfunctions.I believe that we made a wise choice in referring to the Bulletin during this short event. However; in the future; after a 'Non - Normal' event is complete or stabilized; a detailed review of the QRH; Bulletin or other source document would be helpful. A slower review during a low workload time would help to avoid this type of mistake. A more detailed review would have led me to make an AML entry; notify ATC and [Operations Center].Additionally; an update to the FOM Table X.XX for the GPS events would help to prevent this type of error.




Synopsis: Air carrier Captain reported a possible GPS jamming event near Iraq. The Captain failed to enter the event in the AML.