MIAMI – In order to face possible threats, the US military conducts routine testing on GPS that affects all ATM, CNS, and ADS-B systems, the latter which reports an aircraft location to Air Traffic Control (ATC).

The above acronyms ATM and CNS stand for Air Traffic Management and Communication Navigation Surveillance. An FAA commissioned report – Operational Impacts of Intentional GPS Interference – of March 2018 states that these jamming exercises are on the increase and create serious problems to air traffic control and commercial airlines.

Photo: Matthew Calise/Airways

Moreover, GPS jamming extends well beyond the testing area, affecting signals as far as 400nm (nautical miles) and up to FL400 (40000ft) and above.

Military issued NOTAMs (Notice to Air Men) covering great expanses of land, at times entire states, create problems of its own generating a ‘chicken little’ syndrome in Pilots: It is so big it cannot be true! In the case of the Florida exercise, the area affected was 125000 square miles.

Florida GPS Interference Testing. Image: FAA

Serious GNSS Loss Incidents

Some serious incidents could have taken place following the loss of the Global Navigation Satellite System (GNSS). Cases in Texas, Idaho, and Nevada have resulted in serious incidents, which could have easily evolved into accidents, following the loss of GPS navigational aids during approach or navigation.

To avoid such issues on 24 occasions (in 2017), ATC had to revert to an action called ‘stop buzzer’ that requests the military to pause the jamming. In the Texas incident, a commercial flight approaching El Paso lost all GPS aids due to exercises held at the White Sand missile range.

The aircraft missed an approach due to wind conditions, tried again, and landed visually with no access to its Instruments Landing System (ILS) with vertical guidance. The runway in question has a high Controlled Flight Into Terrain (CFIT) risk due to terrain configuration.

Aircraft tracks disruption during GPS jamming. Image: RTCA report

Finding Solutions

The problem is being addressed both by the International Civil Aviation Organization (ICAO) and the FAA since GPS jamming has a direct incidence to the Next Generation navigation systems. Commercial aviation is becoming more and more GNSS-reliant while traditional navigational equipment is being phased out.

Lack of reliable GPS services would adversely impact operations, causing delays in landings and take-offs at major airports or adversely affect situational awareness in crowded airspace if ADS-B fails.

Photo: Mateo Skinner/Airways

To address these problems, the Radio Technical Commission for Aeronautics (RTCA), a nonprofit organization founded in 1935 and author of the FAA commissioned report ‘Operational Impacts of Intentional GPS Interference’, has issued 25 recommendations on how industry and government should work together to achieve secure civil aviation operations alongside the necessary military activities.

These recommendations include “Planning process for interference events…Notifications of interference events to Pilots…Alerting process during interference events…Protect, Toughen and Augment by issuing a better advisory…Improve GPS and radio navigation aid ILS which should not be phased out to become backup systems.”

Photo: Nick Sheeder/Airways

Featured image: Brandon Farris/Airways