Commercial planes would probably get lost a little bit more often?? (The original incident that motivated the USA to opening up GPS for civilian use was in 1983 when “Korean Air Lines Flight 007 was shot down when it mistakenly entered Soviet airspace”.) But it’s not like planes NEED GPS in order to find their way—commercial aviation is (rightfully) obsessive about safety and redundancy, so planes have lots of ways to stay oriented (even in storms / at night / etc), including: - Inertial navigation systems: per claude, “Every airliner carries ring-laser-gyro or fiber-optic inertial platforms that track position by integrating acceleration from a known starting point. They need no external signal at all. They drift — on the order of a couple nautical miles per hour of unaided flight — but modern aircraft run multiple IRUs and blend them, and over a typical flight the drift is manageable and bounded by periodic updates.” - A variety of old-school navigation systems that the FAA specifically requires be kept in place precisely as a GPS backup, including for instance “VOR” beacons which are basically radio-signal landmarks scattered across america, emitting simple radio signals that planes can measure their distance & bearing to. (I assume all other developed countries also maintain similar navigation backups.) - Ground-based flight controllers (ie the people who hang out in those airport control towers) have access to radar systems and thus can see exactly where all the planes are, and help guide planes even if the planes themselves get confused about their position.
You might think “sure, there are backups, but mightn’t you still end up with overloaded systems if everyone suddenly has to switch to using unfamiliar backups?” But it must be the case that aviation is (like the finance industry which has resilient backups for all their precision-timing needs) sufficiently paranoid that their backup systems are actually up to the task of smoothly taking over—the UK study looked at aviation but considered that the consequences of a 7-day outage would be negligible. Overally, the situation might be a little bit like the situation with the power grid—the power grid doesn’t need GPS for any of its normal functioning, but GPS timing information is an important tool for debugging / monitoring / maintaining the power grid, so the system gets more fragile without it. The civil aviation system in theory should be almost unaffected by the loss of GPS, but in practice you’ve lost one layer of your multilayered swiss-cheese-defense against accidents, so accidents are going to go up slightly.
Of course, for unmanned drones (which in many cases only have GPS), a GPS outage would be disastrous.
For military rather than civilian aviation, I think the airplanes themselves would probably find their way around fine in most circumstances, but GPS-enabled weapons (like JDAM guided bombs) obviously wouldn’t work, and the situation on the ground (tanks, vehicles, logistics stuff) would probably get messy in the same way that civilian ports & logistics stuff would get jammed up.
Really interesting write up, thanks! What would the effects be on aviation?
Commercial planes would probably get lost a little bit more often?? (The original incident that motivated the USA to opening up GPS for civilian use was in 1983 when “Korean Air Lines Flight 007 was shot down when it mistakenly entered Soviet airspace”.) But it’s not like planes NEED GPS in order to find their way—commercial aviation is (rightfully) obsessive about safety and redundancy, so planes have lots of ways to stay oriented (even in storms / at night / etc), including:
- Inertial navigation systems: per claude, “Every airliner carries ring-laser-gyro or fiber-optic inertial platforms that track position by integrating acceleration from a known starting point. They need no external signal at all. They drift — on the order of a couple nautical miles per hour of unaided flight — but modern aircraft run multiple IRUs and blend them, and over a typical flight the drift is manageable and bounded by periodic updates.”
- A variety of old-school navigation systems that the FAA specifically requires be kept in place precisely as a GPS backup, including for instance “VOR” beacons which are basically radio-signal landmarks scattered across america, emitting simple radio signals that planes can measure their distance & bearing to. (I assume all other developed countries also maintain similar navigation backups.)
- Ground-based flight controllers (ie the people who hang out in those airport control towers) have access to radar systems and thus can see exactly where all the planes are, and help guide planes even if the planes themselves get confused about their position.
You might think “sure, there are backups, but mightn’t you still end up with overloaded systems if everyone suddenly has to switch to using unfamiliar backups?” But it must be the case that aviation is (like the finance industry which has resilient backups for all their precision-timing needs) sufficiently paranoid that their backup systems are actually up to the task of smoothly taking over—the UK study looked at aviation but considered that the consequences of a 7-day outage would be negligible. Overally, the situation might be a little bit like the situation with the power grid—the power grid doesn’t need GPS for any of its normal functioning, but GPS timing information is an important tool for debugging / monitoring / maintaining the power grid, so the system gets more fragile without it. The civil aviation system in theory should be almost unaffected by the loss of GPS, but in practice you’ve lost one layer of your multilayered swiss-cheese-defense against accidents, so accidents are going to go up slightly.
Of course, for unmanned drones (which in many cases only have GPS), a GPS outage would be disastrous.
For military rather than civilian aviation, I think the airplanes themselves would probably find their way around fine in most circumstances, but GPS-enabled weapons (like JDAM guided bombs) obviously wouldn’t work, and the situation on the ground (tanks, vehicles, logistics stuff) would probably get messy in the same way that civilian ports & logistics stuff would get jammed up.