It’s a paradox of the next generation air traffic system: The more the civil aviation system becomes tied to GPS-based navigation, the more national security requires “degrading” GPS signals to prepare the military to meet new threats.
In some cases, those competing objectives have undermined flight safety, and AOPA “regularly receives complaints from pilots” about GPS interference events. Those events are taking place more often, lasting longer, and being conducted in more locations, said Rune Duke, AOPA senior director of airspace, air traffic, and aviation security.
What’s the solution?
The complaints from pilots speak to serious effects. During one exercise involving degrading GPS reception in Los Angeles Air Route Traffic Control Center’s airspace, in one hour more than 20 aircraft lost GPS navigation, Duke said.
“During these events, aircraft have been documented going off course. Safety of flight issues do occur with these events,” he noted, adding that in September AOPA participated in an FAA-sponsored safety panel to evaluate the hazards. The panel “was not able to reach a conclusion and identify necessary mitigations.”
The increase in intentional GPS interference exercises by the Defense Department spans both numbers and locations. In 2017, Duke said, there were 138 notices issued for GPS interference events. In 2018 to date, there have been more than 170. The tests, which were mostly conducted in the western states but have recently expanded eastward, are lasting longer as the military blocks GPS to test equipment and personnel in exercises in a technologically “degraded environment.”
Some of the activity is designed to counter emerging security risks posed by unmanned aircraft systems (UAS). On the other hand, legitimate UAS flights can rely on GPS navigation—including for such critical safeguarding technology as “geofencing,” which keeps a drone from flying into a forbidden area defined by GPS coordinates.
Notices to airmen informing pilots of GPS-interference tests should help but have sometimes created more problems than they have solved, depicting coverage areas as large as 1,200 nautical miles across. “It is not reasonable to expect that pilots will not fly through in an area that large,” Duke said.
After the inconclusive safety panel, AOPA followed up with the FAA to discuss members’ safety concerns and to monitor the status of the RTCA proposals.
“We understand the FAA is looking at elevating the concerns into a national-level safety panel and is exploring other mitigations,” Duke said. The FAA is also in discussions with the Defense Department to ensure that future GPS-interference events keep everyone safe, he added.
When pilots experience interference with GPS navigation, they should report the problem to air traffic control immediately and follow up with an online filing using the FAA’s GPS Anomaly Reporting Form.
When making your in-flight notification to ATC, it is important to be clear and provide details; the facility has the authority to call off the testing if a pilot encounters a safety-of-flight issue, Duke said.
With the FAA emphasizing the need for aircraft operators to equip with GPS systems and Automatic Dependent Surveillance-Broadcast (ADS-B) capability to operate in the NextGen air traffic system, GPS interference “undermines the usefulness of those technologies, and affects the benefits for pilots who are considering making the investment,” he said.
Bottom line: As discussions with the FAA proceed, AOPA will continue to emphasize to the FAA the safety implications of the situation. “We know from the safety data that there are impacts occurring with these tests and the FAA must take proactive steps to ensure the flying public is safe,” he said.