this post was submitted on 23 Nov 2023
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That just means you can't use autoland in low visibility conditions. Modern IRUs (inertial reference unit) are highly accurate laser gyros that can use GPS for correction, but will throw out the data if it doesn't make sense. Navigation won't be affected much, and autoland (if used) will still rely on VHF guidance.
Modern IRUs also take input from multiple sources (GPS, Navaids) to update their drift error. With spoofed GPS, bad drift corrections are made and when the navigation solution eventually fails the IRU is just as unusable.
ADIRUs will throw out bad GPS data if it disagrees with multiple IRUs, hence why there's usually 3 on the aircraft. That being said, if the GPS is close enough to the three, then correction will still be applied.
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.
Anyone with the ability to jam GPS can easily spoof VOR signals.
But in this case, they're not. Plus, the crew are going to be the ones determining if their VOR/DME makes sense or not.
We don't know that they aren't spoofing VOR/DME as well. We might be seeing reports from affected aircraft, rather than specifically targeted aircraft.