The U.S. Navy has canceled plans to jam GPS signals in the vicinity of the China Lake, California, Naval Air Weapons Station. AOPA had raised concerns about the impact on civilian air traffic and the size of the affected area. The Navy did not reveal the cause of the cancellation, other than to say the reason was “internal.”

AOPA had contacted the Los Angeles Air Route Traffic Control Center (ZLA ARTCC) and relevant FAA offices to express the association’s concerns about the planned outage and its likely impact. The association also had asked the Navy to provide justification for the large geographic area to be impacted by the planned event.

“We have asked the military and FAA to be more transparent around planned GPS outages so that civilian pilots can understand the possible impact on their activities and plan their flights accordingly,” said Rune Duke, AOPA director of airspace and air traffic.

The planned outage was scheduled for an area with a radius of up to 432 nautical miles on six different days in June, running from 4:30 pm to 10:30 p.m. each day.

The outage could have affected GPS and Automatic Dependent Surveillance-Broadcast signals. Degraded GPS signals also have been associated with “unplanned pitch and roll events” in Embraer's Phenom 300.

The Department of Defense conducts an estimated 50 GPS jamming events each year to train personnel to operate in an environment where the GPS signal is degraded or unavailable.

Before a GPS outage can be scheduled, the military proponent must submit its plans to the FAA, whose spectrum office analyzes the potential impact. That impact is then depicted graphically and sent to air route traffic control centers (ARTCCs) that would be affected. The ARTCCs and military then work together to minimize the impact on civilian aircraft, including setting limits on the duration of the jamming and the time of day it takes place. When agreement is reached between the military and the FAA, the FAA issues notams and flight advisories.

To protect civilian traffic, the FAA can call a halt to the jamming if it believes the jamming is creating an unsafe situation for aircraft, for example if navigation is impaired in the vicinity of convective activity.

AOPA closely monitors planned outages and works with the FAA, air traffic control facilities, and the military to minimize impacts and provide information to pilots.

“It’s worth noting that the graphics depicting the impact show the worst-case scenario in order to provide a margin of safety for aircraft, and most outages have a minimal impact on civilian aviation,” said Duke. “Nevertheless, it’s important for pilots to be aware of GPS jamming and how it could affect their flights.”

AOPA is working with the FAA to incorporate GPS outage graphics into its Notam Search system, and some flight planning providers are looking for ways to provide the graphics to their users as they do now with temporary flight restrictions.

“Anytime pilots are affected by a GPS outage event, we encourage them to report their experience,” said Duke. “Without reporting by pilots, it’s difficult to know the extent and severity of impacts.”

Please share any impacts you have experienced from a GPS interference event with AOPA.