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.
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.
How do IRUs work do to give you location?
Imagine you can’t see or hear anything but you can read a compass, and you have an internal map of your house and neighborhood. You also know how long your steps are with some amount of accuracy. You would probably be able to get out of your house and maybe to the corner store, but the inaccuracies in your compass and distance estimation would add up over time, and on a long walk you might overshoot the sidewalk and walk down the middle of a busy street by mistake.
“Give me a stopwatch and a map and I’ll fly the Alps in a plane with no windows?”
This was supposed to be a wild boast by the Russian navigator in Hunt for Red October but is apparently now standard piloting procedure.
They know where you took off from, and can detect your movement with precision.
It’s knows where it was and where it isn’t
They use gyroscopes and accelerometers to measure the aircrafts movement from the starting position at takeoff. That can then be used to plot the course the aircraft has taken to show the current location.
https://en.m.wikipedia.org/wiki/Dead_reckoning
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.
Well the article says it caused at least one plane to almost fly into Iran’s restricted airspace…
I’m glad I wasn’t the only one scratching my head at why was this an issue….(30 + years in aircraft maintenance just not avionics trade, airframes and engines)
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