A Notam (PDF) is warning operators of “all aircraft relying on GPS” of widespread GPS outages starting Tuesday throughout the Southwest and especially southern California. Although the FAA doesn’t go into detail, it seems the military is testing something that can disrupt GPS over a huge area, centered on China Lake, California, home of the Navy’s China Lake Naval Weapons Center. On Tuesday, June 7, the FAA is warning that GPS signals down to 50 feet AGL could be “unreliable or unavailable” between 9:30 a.m. and 3:30 p.m. local time over a radius of 253 nautical miles, which includes the L.A. Basin, Bay area and Las Vegas. There will be further outages of similar potential duration June 9, 21,23, 28 and 30. The circles expand with altitude and at 40,000 feet the interference will affect a circular area of the Southwest 950 nautical miles across, reaching central Oregon, Colorado and New Mexico.
The tests will potentially knock out all GPS-reliant services including WAAS, GBAS and, notably, ADS-B. The FAA also doesn’t want a lot of radio chatter about the outages and is urging pilots to report them if they need help from ATC. Operators of Embraer Phenom 300 business jets are being urged to avoid the area entirely. “Due to GPS Interference impacts potentially affecting Embraer 300 aircraft flight stability controls, FAA recommends EMB Phenom pilots avoid the … testing area and closely monitor flight control systems,” the Notam reads.