GPS/GNSS signal interference has become a creeping normality faced by the global aviation industry, further complicated by military activity and buildup. Some of the reported cases of late have involved Qantas Group, which issued a flight standing order to address interference on VHF channel 121.5 “from stations purporting to represent the Chinese military” during flights over the western Pacific Ocean and South China Sea. Qantas added group aircraft had also experienced GPS jamming suspected to originate from warships operating off the northwest shelf of Australia.
Qantas has advised flight crews that experience unwarranted interference to continue to track their assigned clearance and report the interference to the controlling air traffic control (ATC) authority. “An Intelex report must be submitted providing details of the event or any unusual activity after landing,” the order said.
Speaking with AIN, a Qantas spokesperson confirmed the order, adding that the airline does not consider the recent interference activity as a safety or security threat.
“It's also worth noting the International Federation of Air Line Pilots’ Associations (IFALPA) [position] on this issue,” said the spokesperson, referring to a March 2 IFALPA statement on communication, navigation, and surveillance (CNS) interference, adding “this is not something that’s specific to Qantas.”
According to IFALPA, some airlines and military aircraft were “being called over” VHF channels 121.50 or 123.45 “by military warships in the Pacific region, notably the South China Sea, Philippine Sea, [and] east of the Indian Ocean.
“In some cases, the flights were provided vectors to avoid the airspace over the warship,” IFALPA added. “We have reason to believe there may be interferences to global navigation satellite systems (GNSS) and radio altimeters as well.”
IFALPA said it was coordinating with air navigation service providers and the International Air Transport Association to ensure the harmonization of procedures when dealing with interference. Flight crews should not communicate with warships but immediately contact the controlling ATC and airline dispatcher, it added. They should also file an Aviation Safety Action Program report or similar report for non-ATC communication or GNSS interference with the operator.
In February, EASA issued a revised Safety Information Bulletin 2022-02RI, noting an increase in GNSS jamming and spoofing events, particularly in conflict zones, but also in the eastern Mediterranean, Baltic Sea, and Arctic area. In some cases, the disruption led to “re-routing or diversions, due to the inability to perform a safe landing,” the bulletin said. “At this time, the safety concern described in this [bulletin] is not considered to be an unsafe condition.”
In a 2018 report titled “Operational Impacts of Intentional GPS Interference,” the Radio Technical Commission for Aeronautics (RTCA) issued 25 recommendations to the FAA to mitigate the effects of intentional interference in national airspace stemming from Department of Defense (DOD) missions. The recommendations included the need for the FAA to coordinate with the DOD to avoid GPS signal disruptions during high-volume traffic periods, to only schedule interference events in airspace with ADS-B surveillance, and to modify notams to improve awareness of expected intentional interference events.
In 2021, the National Business Aviation Association and the Aircraft Owners and Pilots Association issued a letter to the DOD and the U.S. Department of Transportation (DOT) requesting a detailed follow-up to the RTCA report, noting the impacts of intentional GPS jamming events.
“While the RTCA report provided many suggested mitigations and recommendations about protocol to reduce the operational impact on civilian operations, the industry has yet to receive any feedback from the agencies on the disposition of those proposed mitigations,” the groups said.
To examine the impact of interference on transportation and assess the DOT’s process of identifying GPS disruptions, the U.S. Government Accountability Office (GAO) analyzed DOT interference data from 2017 through spring 2022 and conducted a performance audit from July 2021 to December 2022.
In its 2022 report to the House Transportation and Infrastructure Committee, the GAO highlighted instances in which user reports on interference were not documented, reviewed, or verified, calling the process employed by the DOT incomplete and inaccurate. Meanwhile, the fact that the DOT’s process did not include reports submitted to NASA’s Aviation Safety Reporting System (ASRS), further compounded matters. Findings revealed 72 ASRS reports excluded from the DOT’s analysis.
“Without a process that produces quality GPS interference information, federal efforts to quickly respond to and stop interference could be delayed.” the report said. “Until the DOT has a more strategic approach in place, it is limited in its ability to assess progress toward resilience, leverage limited resources, and navigate long-standing challenges to improving resilience.”
The International Civil Aviation Organization (ICAO) has issued guidance material to address the impact of intentional and unintentional sources of interference against the backdrop of GNSS loss and CNS planning in the ICAO Middle East region. The host of strategies contained in a 2018 regional group report includes recommendations for flight crews to take advantage of onboard equipment, such as the Inertial Reference System and conventional navigation aids and radar. ICAO encourages operators to develop contingency procedures to enable a fallback mode of operations and report to ICAO and the International Air Transport Association using a GNSS interference reporting form.
“The success of many of the countermeasures is dependent on having a detailed understanding of the threats,” ICAO said. “Monitoring and reporting are required to inform stakeholders of the threats that exist. This would help directly with enforcement, detecting and removing sources of interference, as well as monitoring the response to changes in legislation or education activities.”