Air carrier pilots reported suspected GPS jamming in Chinese airspace near location ALARA on Airway A326.
Synopsis
Air carrier pilots reported suspected GPS jamming in Chinese airspace near location ALARA on Airway A326.
Narrative
We were in cruise in Chinese airspace under Dalian Control at position ALARA on airway A326 at 11300m / FL371. ATC instructed us to offset 5NM Right of track and as we began the turn; I noticed my clock on the glare shield had only dashes. I mentionedthis to the Captain and we immediately began to check the NAV Status page on the FMC. There were 0 GPSs and l then the Captains clock also displayed dashes. A few seconds later R-GPS INVALID message appears on the FMC scratchpad; followed by L-GPS INVALID message. The POS REF page showed no GPS data but the IRS data was available. After we suspected GPS jamming we ran the GPS DATA UNRELIABLE QRH and noted the GPS light on the aft overhead panel was not illuminated. While running the checklist; the GPS returned and disappeared intermittently for a total of 9 minutes. Everything returned to normal at position POVAG at XA:45. The aircraft position was verified to be accurate and the flight continued to NRT as planned. The rest of the flight was uneventful and resulted in a normal arrival in NRT.
Second reporter narrative
While transiting Chinese airspace at FL 371 at approximately position ALARA on A326 the controller directed us to offset 5 miles right of course in preparation to cross over to Korean airspace. As soon as we initiated our offset the FO (First Officer) announced that the GPS signals were lost. This was accompanied by GPS L and GPS R invalid messages on the FMC. I verified both GPS positions were blank on the position page of the FMC. The loss of both GPS positions continued intermittently for about the next 9 minutes. I also noticed returns on the radar that appeared to resemble jamming emissions I have previously seen from my experience as a military pilot. We ran the ran the GPS unreliable checklist and determined our position was still accurate. Both GPS signals eventually returned and the remainder of the flight was uneventful.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.