Although I’ve never really ran into this, i have had my GPS lock up and stop reporting / updating the information.
I was once on my way to a memorial service in Iowa 10 years ago, scud running. The panel GPS worked just fine. My handheld locked up.
25? miles later it started to report again. Not sure what it’s issue was, but it only happened that one time. Perhaps it didn’t like me scud running. )
If you think the high-priced GPS navigator in your airplane is bulletproof, think again. Spoofing by altering the WAAS GPS position is a growing problem that we should all be ready for at any time. Sister publication IFR Magazine recently explained some real-world issues to look for.
The FMS’s in the jet I fly has a function that uses VOR DME signals along with GPS. If the GPS goes out, the DME function will still work for enroute navigation. If flying a GPS approach then you would have to have a VOR backup if equipped. Just goes to show that the 1950’s technology still needs to be available. The FAA reliance on GPS only will eventually come back and bite the agency in the behind.
I get it, and I’ve been preaching the basics as a flight instructor. The editorial emphasizes the need for pilots to stay alert to GPS interference risks, like spoofing and jamming. Bob Teter’s “Tech Talk” article, ‘GPS Jamming, Spoofing,’ is a good read on this. It points out that while GPS interference from military exercises is common in the U.S., deliberate disruptions by bad actors are rare. These issues are more frequent in places like Eastern Europe and war zones, but pilots should always be prepared and avoid over-reliance on GPS. Technical issues such as power loss, antenna disconnects, or broken wires can also cause GPS/WAAS failures. Staying ready for any GPS disruption is always a smart move.
I’ve lost GPS signal several times in and around Nevada. But then they do that sort of thing over there. Luckily I could still hear my CFI telling me to keep my finger on my position on a paper chart. No matter what that gizmo was telling me. Pilotage. Still works.
LORAN may be a more secure alternative.
VORs still work , and there are a large number of them across the US.
No downloads or subscriptions needed, and are almost impossible to jam or spoof.
You are correct, Rafael. Let me add a couple of points that support your post.
These are my opinions and comments and in no way reflect the views/comments of the organization I work for or aviation groups I am a member of.
Some OEMs and operators have begun producing/releasing mitigation procedures due to GNSS interference. If you operate an aircraft that has an OEM or Operator mitigation strategy, please follow it.
If you don’t have an OEM/Operator procedure, please consider the following advice/tips in your ops. NOTE: These are common recommendations (not requirements) that you will need to consider whether they are valid for you and your operation; consider with regard to your MMEL/MEL/Required equipment list; consider with regard to your regulations, route and navigation requirements.
I hope my post can increase awareness regarding this threat to safety-of-flight. While we are relatively inconvenienced/unhindered/safe in the U.S., events and trends elsewhere has shown that it can be a major factor here as well because technology and skills for jamming and spoofing are becoming cheaper, easier to do, and more complicated. ATC is working on their mitigation procedures. U.S. DOD/Air force have begun work on the U.S. GPS system to improve its resiliency. Aviation authorities have started to advise us in letters and circulars more and more. Join discussion groups to learn, know and share more about this threat. Train for this type of threat.
Fly safe!
Excellent technical narrative. Thank you, Joseph.
On magnitude of problem.
After an in-depth search using Google, ChatGPT, and FAA sources, data shows that GPS outages occur less than 1% of the time. Despite this low occurrence, even brief disruptions can have substantial operational consequences in aviation, highlighting the critical need for pilots to maintain proficiency in non-GPS navigation systems to ensure flight safety during these rare but impactful events.
Estimated Key Causes of the 1% of GPS Outages:
Military Exercises (5-10%): GPS signal jamming during military training exercises can cause temporary disruptions, particularly near military installations, which could pose risks to civil aviation operations in adjacent airspace.
Solar Activity (10-15%): Solar flares and geomagnetic storms can degrade satellite signal integrity, resulting in diminished GPS accuracy and availability, particularly during periods of intense solar activity, and affecting high-altitude or polar-region flights.
Jamming and Spoofing (5-8%): Intentional interference, such as GPS jamming and spoofing, can disrupt navigation services. An example is the 2013 Newark airport incident, where a truck’s GPS jamming device interfered with signals, leading to disruptions in airport traffic management and operations.
Aircraft-Specific Issues (2-5%): Faulty components, such as degraded antennas or suboptimal avionics on older or poorly maintained aircraft, can impair GPS signal reception, potentially leading to loss of navigation functionality.
Infrastructure Failures (1-3%): Malfunctions within the GPS satellite constellation or ground-based augmentation systems, though rare, can result in localized or temporary outages, impacting precision navigation services like WAAS or LPV approaches.
Given the critical role GPS plays in modern flight operations, these outages—though infrequent—underscore the necessity for pilots to maintain proficiency with legacy ground-based navigational aids (e.g., ILS, VOR, DME) to ensure redundancy. These systems are vital in maintaining safe and efficient flight operations when GPS is unavailable, allowing for continued safe navigation and approach capabilities, particularly in complex or degraded environments.
More on magnitude of problem.
Upon researching the impact of GPS failures in U.S. aviation, several documented incidents highlight the significant risks these failures pose.
Military GPS Jamming: A considerable number of failures have been attributed to military jamming exercises. In 2017-2018 alone, hundreds of aircraft flying near test sites experienced GPS signal loss, with some planes straying off course. In one notable 2018 incident in Idaho, GPS interference nearly caused a passenger plane to crash into a mountain. The growing dependence on GPS, combined with such disruptions, has raised alarms within the aviation community about the safety and reliability of these systems.
Unexplained GPS Failures: From 2013 to mid-2016, 77 incidents of GPS interference or malfunction were reported. These failures often involved temporary signal loss or incorrect positioning, forcing flight crews to switch to backup navigation methods or rely more heavily on air traffic control.
Personal Privacy Devices (PPDs): In 2012, a famous case at Newark Airport involved a truck driver using a PPD that interfered with the airport’s GPS-based landing systems. Similar incidents have occurred elsewhere, such as in Philadelphia, where PPDs have affected aircraft approaches. These devices, though intended to block personal GPS tracking, can inadvertently create serious risks for aviation operations.
To account for the remaining 62% to 78% of the 1%, factors such as atmospheric conditions, signal interference in urban environments (like tall buildings causing signal shadowing), or undetected minor equipment failures could be involved. Although these issues are less frequently reported or fully understood, they can still significantly contribute to the overall GPS outage percentage.
The problem of GPS jamming becomes more serious as new aircraft like Joby’s eVTOLs and more drones take to the skies, all of which rely heavily on GPS for safe flying. As air traffic grows, so does the chance of GPS signal interference, which could lead to crashes, flight disruptions, or delays.
Cheap jamming devices and political tensions make these issues worse, especially in busy cities where signal interference is already common. To keep things safe, aviation authorities will need to improve GPS reliability and backup systems.
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