Commercial Flights Are Experiencing 'Unthinkable' GPS Attacks and Nobody Knows What to Do
Commercial Flights Are Experiencing ‘Unthinkable’ GPS Attacks and Nobody Knows What to Do::New “spoofing” attacks resulting in total navigation failure have been occurring above the Middle East for months, which is “highly significant” for airline safety.
ADIRUs will throw out bad GPS data if it disagrees with multiple IRUs, hence why there’s usually 3 on the aircraft.
If they’re using the older IRUs, the drift is corrected via redundancy and not GPS. Usually pilots will report drift based on their final IRU coordinates compared against GPS. Even then, they should still be checking their course with VOR.
Pretty much this, look up Kalman filters if you want details. The most likely explanation is that they are tuned to effectively trust GPS more than the internal IMU for long periods of time. Really good IMUs are very expensive and still drift but have high speed output. When it works well, GPS is cheap and doesn’t drift but with a slow update rate. The cost optimisation probably means that the IMU data is usually only trusted for a few seconds, probably 10 min at most before it takes whatever the GPS says as truth. If they lost gps signal through jamming, then they would keep navigation on the less certain IMU data, but the GPS sensor thinks all is well so they shift position.
There is probably a software upgrade to the filter that could be used to limit these attacks, but I imagine it’s an active area or research.
If it’s a smaller plane (such as a CRJ / ERJ) with only one IRU, it will not be able to determine if GPS is valid or not, so the drift correction gets spoiled.
Large commercial aircraft are using 3 IRUs, with newer aircraft using ADIRUs. If GPS does not agree with the three IRUs, the GPS data is thrown out. If the GPS is within tolerance, correction is applied. You could build up very small errors over a long distance, but you should still be pretty close to the airfield when you get there.
Ignore my ignorance. Are you saying the aircrafts track where they are going by calculating their position from gyroscope data? And this is more precise than GPS?
That’s like using the accelaration sensors in your phone to navigate. Or sailing with compass and nautical maps.
Possible. Tech isn’t even that novel. But still impressive.
Yes. Most of commercial navigation systems rely on the IRUs as a primary source of position data, and they’ll usually have 3 of them. VHF is used by the crew to confirm that the aircraft is on track by referencing VOR stations, though these are slowly being phased out due to GPS.
That being said, a single traditional IRU can have up to 2km of drift over a 2 hr flight (at which point it’s removed from service and replaced). When used in combination with two other IRUs, the error is dramatically reduced. Traditional IRUs are gyroscopically mechanical in nature and do not talk to GPS.
Now, that being said, the new standard is called an ADIRU (ADvanced IRU), which ties in with GPS and features laser gyros. They’re extremely accurate and have essentially zero drift, plus multiple redundant components within each unit.
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