Flight safety in Estonia not compromised by Russian GPS disruptions
While Russian interference with global satellite navigation (GNSS) has been on the rise in recent years, aviation safety in Estonia has not been negatively impacted, authorities say.
Estonia still faces issues, however, due in part to its small size.
Disruptions to satellite navigation systems caused by Russia have once again been rising in the Baltic Sea region, after Ukraine's repeated successful drone strikes on Russian Baltic ports such as Ust-Luga.
Raine Luojus, head of aviation safety at Finland's transport agency Fintraffic, told Finnish public broadcaster Yle (link in Finnish) that while the disruptions have not created any dangerous situations in aviation, they extend across practically all of Finland, including the country's largest airport, Helsinki-Vantaa.
However, the disruptions have not affected Estonia's largest airport, Tallinn Airport, Estonian Air Navigation Services (EANS) air traffic controller Mariliis Õun told ERR, the reason being technical.
"The disturbances spread from the source station as radio waves, meaning in straight lines, and at lower altitudes in Estonia they remain 'hidden behind the curve of the Earth.' In other words, they do not reach Tallinn Airport. The impact is at higher altitudes — the farther from the interfering station, the higher the altitude at which they begin," Õun said.
Statistics on the number and impact area of GNSS disruptions in Estonia are compiled by the Consumer Protection and Technical Regulatory Authority (TTJA).
Erko Kulu, head of the agency's frequency management bureau, also told ERR that no significant increase in GNSS disruptions has been observed in recent weeks.
Kulu added that flying will in any case remain safe as aviation relies primarily on other navigation systems that can be used without GPS signals.
Õun too said that while GNSS interference has been a daily reality for them in recent years, with disruptions rising over time, this does not mean flying has become riskier, though it has given extra tasks for her authority.
"Although GNSS disruptions serve to make air traffic management more complicated, they do not compromise flight safety. The systems in use provide controllers with accurate information about aircraft positions, and both controllers and pilots have adapted to the situation, and act to ensure flights remain safe," she said.
Warmer water helps disruptions spread more effectively
Finland's Border Guard issued a warning on Monday LINK to vessels operating in the Gulf of Finland due to GNSS interference. The warning advised mariners to determine their position in old-school style, using nautical charts.
Kulu reiterated that disruptions are strongest at higher altitudes, where commercial aircraft usually fly, but also on the seawater surface in the eastern part of the Gulf of Finland. In the latter case, the arrival of the warmer weather is a factor.
"An increase in the spread of disruptions is expected on the water surface. This relates more to warming weather than to intensified interference from Russia. Warmer water creates favorable conditions for disruptions to spread further," he said.
To date, no GNSS disruptions have been detected in Estonia's territorial waters away from the Gulf of Finland, Kulu added.
Across the Baltic Sea region, there are two main sources of interference: Kaliningrad and St. Petersburg. For Estonia, this means that when flying drones, for example, the impact of disruptions may be felt near the eastern border, and generally not in central or western parts of the country, Kulu noted.
The Police and Border Guard Board (PPA) has established a 5-kilometer no-fly zone near the eastern border, to prevent accidents caused by interference.
Air traffic controllers assist pilots
The most widely used navigation systems in aircraft are GNSS-based satellite navigation systems such as GPS, which provide highly accurate positioning at low cost. If these systems get disrupted, the signal may be lost or may display an incorrect position to the aircraft.
Air traffic controllers also monitor aircraft using secondary radar and MLAT (multilateration), with systems continuously calculating aircraft positions. This means controllers always have an accurate picture of the situation, and GNSS disruptions do not affect this, Õun noted.
"We are always ready to assist pilots if GNSS interference causes them to doubt their correct position," she said.
Controllers also help determine the correct flight path: Where necessary, aircraft are vectored — meaning they are given a magnetic heading to follow — and the entire flight path is then monitored and controlled by the controller, Õun added.
"For final approach, the ILS (Instrument Landing System) is used — a ground-based system that guides the aircraft safely and precisely to the runway and is not affected by GNSS interference," she continued.
Complete independence from GNSS does not at present exist, however.
While GNSS is the most commonly used system, aircraft also rely on traditional radio navigation, which uses conventional aids such as VOR and NDB beacons to determine position via ground transmitters. Larger and more modern aircraft also use inertial navigation and onboard computer systems, said Helen Reinhold, head of the aviation operations department at the Transport Administration (Transpordiamet).
Reinhold noted that while it may seem at first glance that disruptions only affect GNSS-based aircraft, the reality is broader.
"Many modern aircraft use GNSS as part of their onboard computer systems, so disruptions can affect other systems as well, including autopilot, obstacle and terrain avoidance systems, weather radar, and many other things," she said.
Inertial systems are not entirely independent of GNSS either: Over time, they can accumulate errors that are usually ironed out using GNSS data. Consequently, long-term GNSS disruptions can also impact these systems, Reinhold noted.
Estonia faces other issues, too, with other navigation means.
"Estonia's particular challenge is its relatively limited radio navigation network. The country has only one VOR beacon in use, meaning traditional radio navigation cannot be widely relied upon. This means many aircraft in Estonia depend either on GNSS or more complex onboard systems. Smaller aircraft are especially vulnerable, as they lack inertial navigation systems and rely heavily on GNSS or conventional navigation," Reinhold said.
Relying on air traffic controllers is also not a universal solution in any case, and controllers use radar data to assist, though radar coverage and communication capabilities are limited, especially at lower altitudes or in more remote areas — radar coverage in Estonia mainly covers the Tallinn region.
"GNSS disruptions can particularly affect airfields that rely solely on satellite-based approach systems. In Estonia, examples include Pärnu Airport and Kärdla Airport," Reinhold noted.
"If the GNSS signal is not reliable, pilots may not be able to use these approaches. In such cases, an alternate airport must be designated. Often this role is fulfilled by Tallinn Airport, which has a ground-based ILS system that does not depend on GNSS," she added.
Going forward, Reinhold said GNSS disruptions in Tallinn could increase the workload for air traffic controllers and reduce airspace capacity, especially in situations where many aircraft require assistance.
"However, the volume of air traffic at Tallinn Airport is currently not high enough to cause serious problems," she noted.
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Editor: Andrew Whyte
