The emergence of GPS as a civil navigation system through the late 1990s and into the 21st century has underpinned a remarkable technological transformation in how transport systems navigate the world.
Initially developed by the U.S. Department of Defense in the 1970s for military navigation, this system of 24 satellites beams time and location signals to GPS receivers on Earth, from our smartphones to aviation navigation systems. We have probably all become over reliant on its pinpoint accuracy and instantaneous ability to give us position information, even in 3D, whether it is to find that new restaurant or to conduct a point-in-space (PinS) approach in poor weather.
Of course, since the original system was made available, new satellite constellations have been put into orbit, such as the European Union’s Galileo or Russia’s Global Navigation Satellite System (GLONASS). It’s now not quite correct to use GPS as the overall term for such systems, but it’s probably easier for all of us to understand.
The intentional disruption of GPS signals poses a silent but significant threat to everyone who uses these systems to navigate. From transportation to telecommunications, the disturbances caused by GPS jamming can have profound impacts. But for aviation, this is especially important since it gives us the guidance we need to keep us away from danger in poor weather, and enables us to complete the various missions and tasks we need to deliver.
Our ability to navigate visually while airborne is something that we learned early in pilot training, focusing on planning a route in detail and then using “clock-map-ground” techniques to get us where we need to be. This ability was checked when we completed our skills test (private and commercial) but it was only a basic level check. For those who needed it, instrument flight training considered the use of both ground-based systems (VOR/DME/ILS) and GPS navigation. However, since then, how many of us are guilty of watching a screen to tell us where we are, either in the form of an integrated cockpit map system or as an application on a tablet or phone rather than actually navigating?
The term GPS jamming refers to the deliberate transmission of radio signals at the same as or close to the frequency of the GPS signals, causing interference. Such jamming can range in complexity and scope from that delivered by state actors, in support of military or other requirements, to more individual based systems designed to fool tracking systems or those required to monitor working patterns.
In the former case, other effects such as spoofing can be used, which attempt to fool the aircraft systems that they are not where they should be. In either case, the effects are similar, affecting airborne navigational accuracy or in some cases, causing the aircraft navigation system to lose its ability to navigate accurately all together.
Of course, we should not ignore the extraterrestrial effects on GPS systems like sun flare activity, which can cause the loss of signals due to electromagnetic interference or the destruction of individual satellite electronics.
The frequency of GPS jamming incidents can vary based on the region, context, and specific timeframe in question. Some factors to consider:
- Regional and political climate: In conflict zones or areas with heightened political tensions, GPS jamming might be more frequent as part of military or disruptive tactics. For example, since the invasion of Ukraine, there has been a marked increase in such events close to the Norwegian border with Russia;
- Criminal activity: Some criminals use GPS jammers to evade tracking or to commit crimes, such as theft from vehicles, without being detected;
- Legal use of jammers: In some situations, jammers might be used legally, such as in specific military operations or exercises. While these activities can interfere with civilian GPS reception, they are conducted within legal parameters;
- Increasing availability of cheap jammers: As technology has advanced, the availability of cheap and portable GPS jammers has increased. While illegal to use in most countries, they are easy to buy on the internet and their use has exploded in the ground transport arena.
In terms of specific numbers, it’s challenging to provide a definitive answer on the frequency of such incidents, but it happens more often than most assume. Monitoring agencies and organizations in different countries might provide periodic reports or statistics on detected incidents, but a global, comprehensive figure is challenging to find.
Helicopter and other aviation operators should consider these factors when reviewing their training and checking systems for pilots/crews. It’s certainly a good idea to make sure that they have the ability to still utilize those old ground-based navigation systems for instrument flight rules (IFR) operations and that they can still use a map when it comes to visual flight rules (VFR) operations.
Other mitigations may also be appropriate, such as regular checks with the aviation authorities on known GPS blackspots. Heathrow Airport in the U.K. has had problems with localized GPS outages due to delivery drivers using jammers in their vans. In addition, how many of us really know what GPS constellation our aircraft or tablet is using and how resilient it might actually be to both transient and long-term loss or disruption of signals?
On a more general basis, aviation authorities and governments are taking more action on countering the issue where possible. This includes:
- Detection systems: Technologies to detect and locate jammers are being developed and deployed, particularly in sensitive areas like airports;
- Backup systems: Recognizing the importance of redundancy, some sectors are turning to alternative navigation systems, such as the European Union’s Galileo or Russia’s GLONASS;
- Enhancing GPS: Steps are being taken to make the GPS system itself more resilient, including developing new signals that are harder to jam;
- Legislation and enforcement: Many countries are imposing stricter regulations on the sale and use of jamming devices, coupled with hefty penalties for violations.
However, where the risk is worth the reward, jammers and spoofing systems are not going away. As helicopter pilots and operators, we need to be sure we can deal with the loss of our systems’ navigational accuracy due to interference with GPS signals and still fly safely.
Simon Sparkes is a test pilot for the Norwegian Defense Materiel Agency who started his flying career with the Royal Navy at the end of the 1980s. With over 50 aircraft types in his logbook, his experience has ranged from anti-submarine warfare operations on the Sea King, to basic helicopter instruction on the Gazelle, to commercial light twin operations in both the EC135 and AS355. Previously the commanding officer of the Empire Test Pilots’ School, he currently works on a variety of projects with the AW101 SAR Queen in the challenging Norwegian environment.
