GPS has become increasingly important to our lives. Not only do Waze, Uber, and many other applications heavily rely on global positioning system. Our cellular networks rely on GPS clocks, banking systems, financial markets, and power grids all depend on GPS for precise time synchronization. In the finance sector, GPS-derived timing allows for ATM, credit cards transactions to be timestamped. Computer network synchronization, digital TV and radio, as well as IoT (Internet of Things) applications also rely on GPS-clock and geo-location services.
In an operational environment jamming GPS signals represents both a threat and an important capability. In addition to serving an important purpose in navigation on land, sea and in the air, GPS also provides targeting capability for precision weapons along with many other tactical and strategic purposes.
For this reason, the U.S. military frequently trains to deny or degrade GPS signals on a large-scale. In 2017, we went inside Nellis AFB to get a firsthand demonstration of how easy and how quickly the U.S. Air Force can jam GPS signals for training purposes.
For instance, the U.S. Navy’s CSG-4, that “mentors, trains and assesses Atlantic Fleet combat forces to forward deploy in support and defense of national interests”, is currently conducting GPS Interference testing in the East Coast area. As an FAA NOTAM (Notice To Airmen), issued for airspace in eight of the FAA’s Air Route Traffic Control Centers, warns, GPS could be degraded from Caribbean and Florida north to Pennsylvania west to the eastern Louisiana, while the tests are conducted Feb. 6 – 10, 2019, at different hours.
The area affected by GPS interference operations.
GPS-based services including Automatic Dependent Surveillance-Broadcast (ADS-B), the Ground Based Augmentation System, and the Wide Area Augmentation System, could be unreliable or lost in a radius extending several hundred miles from the offshore operation’s center, the FAA said.
In 2017, we went inside Nellis AFB to get a firsthand demo from member of the 527th Space Aggressor Squadron (527th SAS) who showed us how easy and how quickly the U.S. Air Force can jam GPS signals for training purposes: in only a few seconds members of the 527th SAS used commercial off-the-shelf (COTS) equipment to jam local GPS reception making many public services unavailable.
This is not the first time such GPS-denial operations take place. It has already happened on the West Coast in 2016 and, more recently, on the East Coast, at the end of August 2018:
As happened in all the previous operations, we really don’t know which kind of system is being used to jam GPS. However, it must be an embarked system, considered that the source of the jamming is a location off the coast of Georgia, centered at 313339N0793740W or the CHS (Charleston AFB) VOR 173 degree radial at 83NM (Nautical Miles).
As mentioned, not only the military is so heavily reliant on GPS.
AOPA estimates that more than 2,000 airports — home bases to more than 28,600 aircraft — are located within the area’s lowest airspace contour. The East Coast test is “unacceptably widespread and potentially hazardous,” said Rune Duke, AOPA senior director of airspace, air traffic and aviation security, in an article on AOPA website.
Here’s another interesting excerpt from the same article that provides examples of how the GPS testing has affected general aviation:
A safety panel held in September 2018 ended with the FAA deadlocked on a path forward. In November 2018, AOPA reported on instances of aircraft losing GPS navigation signals during testing—and in several cases, veering off course. Instances have been documented in which air traffic control temporarily lost the tracks of ADS-B Out-equipped aircraft.
In a vivid example of direct hazard to aircraft control in April 2016, an Embraer Phenom 300 business jet entered a Dutch roll and an emergency descent after its yaw damper disengaged; the aircraft’s dual attitude and heading reference systems had reacted differently to the GPS signal outage. This issue was subsequently corrected for this aircraft.
AOPA is aware of hundreds of reports of interference to aircraft during events for which notams were issued, and the FAA has collected many more in the last year. In one example that came to AOPA’s attention, an aircraft lost navigation capability and did not regain it until after landing. During a GPS-interference event in Alaska, an aircraft departed an airport under IFR and lost GPS on the initial climb. Other reports have highlighted aircraft veering off course and heading toward active military airspace. The wide range of reports makes clear that interference affects aircraft differently, and recovery may not occur immediately after the aircraft exits the jammed area.
Pilot concern is mounting. In a January 2019 AOPA survey, more than 64 percent of 1,239 pilots who responded noted concern about the impact of interference on their use of GPS and ADS-B. (In some cases, pilots who reported experiencing signal degradation said ATC had been unaware the jamming was occurring.)
Interestingly, “stop buzzer” is the code word, pilots may radio to the ATC when testing affects GPS navigation or causes flight control issues:
Pilots who encounter hazardous interruption of GPS navigation or who have flight-control issues should be aware that they can say the phrase “Stop buzzer” to air traffic control, which initiates the process of interrupting the testing to restore navigation signal reception, Duke said.
During previous GPS-interference events, pilots declared emergencies, but the jamming continued because ATC did not understand that the emergency was related to the GPS interference. According to the Pilot/Controller Glossary, “stop buzzer” is a term used by ATC to request suspension of “electronic attack activity.” Pilots should only use the phrase when communicating with ATC, or over the emergency frequency 121.5 MHz, if a safety-of-flight issue is encountered during a known GPS interference event. Using this unique phrase when experiencing an unsafe condition related to GPS interference will ensure that ATC and the military react appropriately by stopping the jamming, Duke said.
“Pilots should only say ‘stop buzzer’ when something unsafe is occurring that warrants declaring an emergency. They should make sure ATC knows that the emergency is GPS-related and that halting the GPS interference will resolve the emergency,” he said.
Despite the complaints from the civilian side, dominating the GPS “domain” is crucial to win. Consequently, along with the periodic testing like the one underway in the U.S. southeastern coast, GPS jamming has become a common operation of the most recent Red Flag exercises that include simulated scenarios where warfighters train to operate in an environment where electronic and cyber-attacks may disable GPS capability.
This article originally appeared on The Aviationist. Follow @theaviationist on Twitter.