The Alarming Surge of GNSS Jamming That’s Threatening Flight Safety

GNSS Jamming (and Spoofing) is becoming a massive threat to flight safety, especially now that we’re fully transitioning to Performance Based Navigation (PBN) procedures across the globe 🌎

EUROCONTROL reported a 2000% increase in GNSS interference incidents in 2018, and almost 40% of European air traffic operates through regions that are regularly affected by GNSS Jamming and Spoofing.

How does GNSS work exactly, and what does Jamming and Spoofing mean?

Let’s take a look! 👀

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How does GNSS Work?

GNSS stands for Global Navigation Satellite System. Don’t confuse GNSS with GPS. GNSS is the name of the group of systems that all try to achieve the same thing: provide accurate positioning data to users. GPS is just one of these systems that are out there.

The 4 main GNSS systems in the world today are:

Before we can understand what exactly is going on with GNSS Jamming or Spoofing, let’s quickly go over the general principles of how GNSS works.

There are 3 main components of GNSS:

The space segment is the satellites, the user segment is the plane, helicopter, or even iPhone trying to get a location, and the control segment is the ground stations providing corrections for time dilation and other inaccuracies we have to deal with, we covered this here.

There are 4 main steps involved:

This is just a basic outline, and there’s a lot more involved behind the scenes, but keep this basic working principle in mind.

What is GNSS Jamming?

GNSS Jamming is a method that interrupts the service of GNSS by interfering with the signals that the space segment (the satellites) send out that users normally calculate their position with.

Jamming devices send out a radio frequency signal on a similar frequency that is also used by GNSS satellites. These signals then interrupt or sometimes even completely block the original signals that the user is trying to receive.

GNSS receivers are designed to pick up multiple signals from as many satellites as possible to provide the best possible accuracy.

This means that the more satellites get blocked from sending signals to the user, the more serious the disruption becomes.

What is GNSS Spoofing?

While GNSS spoofing has the same end result as GNSS jamming (disrupting GNSS services), the method is completely different.

Spoofing works by trying to trick the GNSS receivers. It does this by generating fake signals that try to mimic satellite transmissions.

When GNSS receivers then pick up this fake signal, it ends up using a signal that does not come from the actual satellites it’s trying to use, but it thinks it is!

This results in a system that considers 1 of the satellites to be either really close or really far away. This completely screws up the location calculation, i.e a bad day for pilots (especially in the middle of an approach).

Spoofing is considered to be a little bit more ‘sophisticated’. Rather than just disrupting signals, it’s actively trying to be perceived as an original signal!

Both of these methods can result in significant disruptions, and have a massive impact on flight safety every day.

This is an example of an airline flight crew experiencing spoofing above the Middle East, causing spurious GPWS warnings. You can probably imagine how confusing this could be at night over mountains.

How is GNSS Jamming and Spoofing Affecting Aviation?

As we said in the intro, EUROCONTROL reported a 2000% increase in GNSS interference incidents in 2018, and almost 40% of European air traffic operates through regions that are regularly affected.

EUROCONTROL also reported:

Between 2016 and 2020, the highest percentage of GPS outages were during the en route flight phase. The next highest at 12.77% was during the approach phase.

In addition to this, the Airbus Flight Data Monitoring system reported an increase in GNSS outages. For instance, 2021 had 49605 reported outages. In 2022, this has risen to a total of 10843 reported outages, that’s a crazy increase!

If we extrapolate these numbers, we can see it could mean even more GNSS service outages in the next few years. A lot of these interference areas are close to conflict zones, where different militaries are the source of the jamming or spoofing. The problem is that the effects of this spread to areas way beyond the conflict zones themselves, affecting civil aviation.

For reference the biggest areas of reported interference are:

• The Black Sea area
• The south and eastern Mediterranean area
• The Middle East
• The Baltic Sea area
• The Arctic area

Recognising the Signs of GNSS Jamming and Spoofing as a Pilot

While both GNSS jamming and spoofing do not have a specific symptom, there are various things we can note as pilots that indicate something weird is going on. Here are main things to look out for:

• Non-sensical GNSS position indications
• GNSS and FMS disagreements and/or warnings
• Unexpected differences in True Airspeed and Groundspeed
• Time shifting (if your onboard chronometers are GNSS adjusted)
• Problems with onboard Inertial Navigation and Reference Systems
• Inconsistent Flight Guidance that the Autopilot references GNSS for
• RNP values that are out lof limits for normal operations

Again, none of these specifically guarantee that jamming or spoofing is the root cause. However, where there’s smoke, there could be fire.

What can be Done About GPS Jamming and Spoofing?

EUROCONTROL and many other regulators like EASA and the FAA have indicicated they are actively working to create regulatory frameworks to tackle this issue. The question is: what can actually be done about it if the majority of the sources come from conflict areas?

Well, first of all the reporting needs to become more accurate. There are still loads of occurances that go undetected or unreported because equipment does not tend to give alerts specifically related to interference.

Sure, you could argue that RAIM, SBAS and overall integrity monitoring can help with this, but none of these tools specifically point at whether or not active interference is taking place.

EASA said this in a recent bulletin:

Pilots need to be trained to recognise the main signs of GNSS jamming, and report the findings. Only with accurate reporting can regulators and organisations like EUROCONTROL investigate these issues further to come up with better policies to tackle the issue.

In addition to this, EASA has suggested these main mitigations (and more):

• Ensure that contingency procedures are established by operators and third parties, and that conventional navigation aids are maintained while this problem is being addressed
• Implement pro-active mitigation measures, including the issuance of NOTAMs
• Come up with a way to collect information regarding GNSS degradations
• Initiate discussion at a national level to discourage GNSS Jammers
• Engage with operators to make sure they raise awareness across their workforces and train for specific scenarios where GNSS references are inaccurate or completely lost

If you detect or suspect an issue with your GNSS location, these are the main actions to take:

• Verify your positions by referencing anything other than GNSS, such as conventional charts or radio navigation aids
• Double-check that you can still fly your intended procedure based on the RNP integrity and accuracy levels (is SBAS still available?)
• Verify GNSS chronometers are not affected by using other time sources
• Remain prepared to fly a non-RNP procedure to break cloud
• Report the issue to your local authority in the form of an MOR

While this list is not exhaustive, these are the main ways CAA’s as well as pilots can deal with this rising threat, while it’s being addressed on a global level.

References

EUROCONTROL on GNSS Jamming

EASA on GNSS Jamming

Report GNSS Jamming to the FAA

Conclusion

GNSS jamming and spoofing continues to be threat to flight safety. The data shows it’s becoming a bigger problem as time goes on. It’s up to regulators and organisations like ICAO to address this problem head on, especially in times where PBN becomes the norm more and more.

We don’t publish all our Notes from the Cockpit (like this one) publicly, some are shared only by email. Get the next one sent straight to your inbox ⤵️