Air carrier first officer reported a suspected GPS jamming event during takeoff at ZGGG; Guangzhou Baiyun International Airport; China.
Synopsis
Air carrier first officer reported a suspected GPS jamming event during takeoff at ZGGG; Guangzhou Baiyun International Airport; China.
Narrative
Completed normal taxi out and pre takeoff procedures/checks. We were cleared for takeoff on 02L from A10. Capt positioned the aircraft for takeoff and advanced the throttles to set takeoff power. Almost immediately after selecting TOGA on the throttles; we received an EICAS aural alert and message for FMC runway position disagree. IAW (In Accordance With) with FOM; the Captain elected to reject the takeoff at approximately 20-30 knots. FO notified the tower of our reject and we received clearance to taxi clear of the runway at A9 and taxi to a safe position to hold and accomplish checks. We completed the RTO (Rejected Takeoff) ECL (Electronic Checklist); Gnd prox (Proximity) system ECL; and the FOM flow chart. All systems were indicating normal and we verified all FMS data was loaded correctly for the takeoff runway. After a discussion amongst the crew members we elected to continue and reattempt another takeoff noting a momentary GPS interference or jamming issue was likely the problem. ZGGG Tower sequenced us for another takeoff on 02L which occurred without incident. At approximately 1500'; we had a GPS L EICAS alert which cleared; and at 5000' we received a GPS L and ADS-B Out L alerts which cleared. Again after discussing we determined it was safe to continue. Remainder of flight was uneventful.Cause: Based on multiple momentary loss of GPS signal we concluded this was likely GPS interference or jamming nearing the end of the runway. Suggestions: This was a startle event during the normal takeoff process. Momentary GPS/navigation issues likely triggered the event. Based on good training; the crew handled this well and coordinated with ATC throughout. Tower controllers provided necessary assistance and coordination to safely reposition the aircraft.
Second reporter narrative
All pre departure checks had been done and we were cleared for takeoff on ZGGG runway 02L from taxiway A10. I was PF; I pushed throttles forward and when I selected TOGA we received the EICAS message FMC runway disagree and aural alert. I rejected the takeoff at slightly under 30kts and exited the runway at A9. We cleared to an empty taxiway to comply with checklists. We complied with the Gnd prox (Proximity) system ECL (Electronic Checklist) and all of the alerts went away. We again verified our position and that the runway selected in the FMS was correct. We complied with the checklist; and the RTO (Rejected Takeoff) checklist. We then had a crew discussion about our options and decided that it was safe for another takeoff. We requested this from can tower and the subsequent takeoff was uneventful. During the climb we received momentary EICAS messages for GPS L and ADS-B out L. These alerts were momentary and the rest of the flight was normal. I have included pictures of the alerts; messages; and Mx write ups for clarity. Cause: I believe that this was a momentary GPS malfunction or possibly signal jamming or interference. Suggestions: I think this was unfortunate timing of a transitory anomaly. I believe that our actions as a crew were the correct ones given the conditions. Checklists; comments; and concerns were complied with; discussed; and addressed as needed. The flight was then completed without further incident. ATC was helpful and appreciated.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.