B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 194
Confusion; Distraction; Troubleshooting
Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types
Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Overcame Equipment Problem; Flight Crew Became Reoriented
Environment - Non Weather Related; Aircraft
After takeoff while on EDETH 3 RNAV; I selected LNAV and the HSI did not indicate a left turn to SAPEE; when we should have turned. The F/O initiated a left turn; and I notified SLC Departure a need for vectors. The Controller provided heading and altitude and mentioned there were GPS jamming issues earlier that day. It was similar to our present issue; but according to his information; should have ended about 30 minutes before our departure. We were able to navigate to SCANT; and resume the Departure. The aircraft did not display a GPS annunciation. Initially; indications seemed to lead to believe a lockup; but all FMC pages were selectable. The issue was gone; almost as quickly as it occurred. I noted no anomalies. NOTAMs mentioned 'due to GPS interference impacts potentially affecting Embraer Phenom 300 aircraft flight stability controls; FAA recommends avoid the above testing area and closely monitor flight control systems due to potential loss of GPS signal.'
B737 Captain reported the loss of a reliable GPS signal which he attributed to military activity in the area. ATC provided headings until GPS guidance was reestablished.