B737 captain reported the loss of a reliable GPS signal which he attributed to military activity in ...

Attributes
ACN	1353460
Time
Date	201605
Local Time Of Day	1201-1800
Place
Locale Reference	SLC.Airport
State Reference	UT
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Initial Climb
Route In Use	SID EDETH3
Flight Plan	IFR
Component
Aircraft Component	GPS & Other Satellite Navigation
Person 1
Function	Captain Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 194
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Track / Heading All Types

Narrative:

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 first officer 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.'

Original NASA ASRS Text

Title: 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.

Narrative: 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.'

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.

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.