Aviation groups urge ICAO action on GNSS vulnerability

International aviation groups are appealing to ICAO for urgent action to address GNSS interference.

In a paper entitled An Urgent Need to Address Harmful Interferences To GNSS that is being presented to the 40th ICAO Assembly, the International Federation of Air Traffic Controllers’ Association (IFATCA), the International Federation of Air Line Pilots’ Associations (IFALPA) and the International Air Transport Association (IATA) are pressing the issue.

The paper points out that the impacts of disruptions go far beyond their significant negative effects on safety of flight, efficiency and air traffic management:

In addition to aircraft navigation, GNSS is a main component of various essential communication, navigation and surveillance (CNS) and flight safety/control systems,” they argue.

They cite the fact that GNSS is used to provide timing signal to some satellite communications avionics which are essential for operations in oceanic and remote airspaces where the sole aircraft position source is Automatic Dependent Surveillance – Broadcast (ADS-B).

Some business aircraft are also using GNSS as a reference source for aircraft flight control and stability systems. “Particularly noteworthy, GNSS is a necessary component of an aircraft terrain awareness and warning system (TAWS) – a mandatory aircraft safety system implemented to alert pilots of upcoming terrain,” the report authors state.

The Resilient Navigation and Timing Foundation (RNTF) which represents the interests of GNSS users pointed out that the aviation groups express ‘in the somewhat stilted language of diplomacy and international organisations’ that ICAO signatory states know what to do, but have failed to take action.

It said that in 2012 ICAO recognized the vulnerabilities of weak GNSS signals and recommend that states ‘develop and enforce a strong regulatory framework governing the use of global navigation satellite system repeaters, pseudolites, spoofers and jammers’ and ‘apply, as necessary, recognized and available mitigation methods’.

“We know of no nation that has undertaken such an effort,” said RNTF. “We hope it will not take one or more mishaps for nations to recognize and deal with the very real threat to safety of life posed by GNSS disruption.”

RNTF cites an example from a June 2019 NASA newsletter of a passenger aircraft that was making an approach to an airport serving the ski resort town of Sun Valley, Idaho in the North American Rockies.

Smoke in the area was limiting visibility and according to the report filed with NASA, the aircraft was cleared to descend to 9,000 feet on a GPS-based instrument approach. GPS interference had been reported earlier, but had cleared up. Minutes later a radar controller 250 miles away noticed that the aircraft was at 10,700 feet approaching a 10,900 foot mountain. He called the control tower which vectored the aircraft in time to avoid a disaster. The reporting party concluded “had [the radar controller] not noticed, that flight crew and the passengers would be dead, I have no doubt”.

RNTF said interference with GNSS signals has become the bane of the global aviation system and is responsible for delayed pushbacks, extended routings, missed approaches, and delays.

“Global aviation operators have long contended with unreliable GPS/GNSS service in some parts of the world. Reception anywhere near North Korea, around Manila, and some parts the Arab world has been infamously unreliable for years,” it said.

“Increasing armed conflict in the eastern Mediterranean has compounded problems there recently. Eurocontrol reported a several fold increase in outage reports in 2018 over previous years. Aircraft arrivals and departures at Israel’s Ben Gurion Airport experienced GPS disruptions for two months this summer.

“Yet Sun Valley, Idaho is in the heartland of North America, far from any international conflict zone. It is presumably under the firm control of domestic authorities with an interest in keeping GPS and other GNSS signals clear and uninterrupted. Whether the cause of the near-miss was a poorly communicated military exercise, a citizen with an illegal jammer, or some other reason, has yet to be made clear.”

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