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.
How do IRUs work do to give you location?
First, they have to align on the ground. You initialize them with your current known position (usually by GPS or your known airport/gate spot). Then, you wait for them to synchronize with the Earth's rotation. If you're far north, like in Alaska, this could take half an hour. If you're close to the equator, it could take 5 minutes. Once they're ready, from that point, any movement you make, it will know where you are and where you've been.
If you spin up a gyro and begin moving around, it will maintain it's starting position. You can use this deflection to calculate direction. If you know how fast you are going and for how long, you'll have your position.
Mechanical gyros drift. It's the nature of a world with friction. Newer IRUs use laser gyros, so the only real drift they have comes from extremely minute rounding errors.