5 ms·
> The Boeing 737 MAX 8-200 had already descended to around 850ft (259m) when the disruption occurred. Instead of landing, the plane was forced to climb back int
by bArray 2y ago
> The Boeing 737 MAX 8-200 had already descended to around 850ft (259m) when the disruption occurred. Instead of landing, the plane was forced to climb back into the sky and divert nearly 400km (250 miles) south to Warsaw, Poland. Lithuanian air authorities later confirmed the aircraft had been affected by "GPS signal interference".
GPS is incredibly flimsy. Normally it operates by taking the average of 1000 observations to generate a noisy signal. It's not that difficult to be louder than something shouting from space. You can pick up cheap GPS blockers easily about the size of a walkie-talkie (handheld radio).
> By carrying a group of atoms cooled to -273C on the plane itself, rather than relying on an external signal, the technology can't be interfered with by jamming.
Last year I was on a plane where if the engines were not running, it entirely went into darkness. They hooked the plane up to the airport and tripped the airport electrics too. Now imagine if your plane loses power momentarily, and suddenly your GPS stops working entirely.
> Henry White, part of the team from BAE Systems that worked on the test flight, told BBC News that he thought the first application could be aboard ships, "where there's a bit more space".
> Quantum clocks, gyroscopes and accelerometers are large, bulky and incredibly expensive, with an accurate quantum clock costing around £100,000. Yet military research is allowing the creation of smaller, better and cheaper systems.
Likely a minimum of 10 years from being viable. Mt White of BAE is politely saying as much.
- freddie_mercury 2y ago> Now imagine if your plane loses power momentarily, and suddenly your GPS stops working entirely. Now imagine your plane loses power momentarily and switches to a backup system... The exact same GPS every plane is using today.
- SkyPuncher 2y agoEven further, you can loose your super accurate special crystal and simply fall back to “normal” GPS.
- Cthulhu_ 2y agoI don't really understand why the plane was diverted because GPS was jammed; I get that it's important for navigation, but not how it's required for landing when they're that close. There's (iirc) close range guidance systems, and of course visual ones (lamps, stripes, etc).
- mapt 2y agoCommercial air travel is very risk-averse. Best practice is that if something unexpected occurs, and you have plenty of fuel to spare, you go and and find someplace else to land.
- macguillicuddy 2y agoMy understanding is it depends on the amount of visibility, plus what type of approach they were on. One type of approach, an ILS, has big radio transmitters pointing from the runway into the air and allows the plane (either pilots or autopilot) to get close enough to the runway without visibility, and with enough precision, to land. In many circumstances ILS isn't available and an alternative is Required Navigation Performance (RNP) which uses GPS plus a ton of other inputs to give some amount of precision to the same end. If they're on an RNP approach but suffer a reduction in navigation accuracy then I imagine it's a policy 'go-around'. Even if there's enough visibility it allows the pilots to brief a 'visual' approach before attempting it.
- Gathering6678 2y agoConsidering it's below 1000 feet, losing GPS could indicate an "unstablized" approach and require a go-around, as opposed to losing it at a higher altitude where the pilot could have more time to safely switch to alternatives (other navigating aids or go to visual?). Source: my guess after watching a lot of aviation YouTube videos......
- alistairSH 2y agoFor anybody who doesn't know, a "stabilized approach" is an approach with a constant angle and speed as the plane descends and lands. This allows the plane to keep consistent control settings (flaps, throttle, etc). It's best practice/policy for all major airlines to use stabilized approaches and most/all require a go-around if the stabilized approach is interrupted (there are edge cases and exceptions).
- mapt 2y agoChip-scale atomic clocks based on cesium were demonstrated in 2003 with DARPA/NIST funding, and entered commercial production in 2011. https://en.wikipedia.org/wiki/Chip-scale_atomic_clock https://en.wikipedia.org/wiki/Chip-scale_atomic_clock Apparently they're not even export-protected, despite their obvious use in GPS validation schemes and in RTK. > The SA.45s CSAC has an Export Commodity Control Number (ECCN) of EAR99. This means it is not ITAR-controlled and does not require a special license to ship to most nations. The SA.45s CSAC classification is controlled by the Bureau of Industrial Security (BIS) within the US Department of Commerce. The article talks about quantum "optical clocks" but doesn't really explain the concept. Which appears to be this: https://en.wikipedia.org/wiki/Quantum_logic_clock https://en.wikipedia.org/wiki/Quantum_logic_clock Which, like many things named "Quantum", still doesn't really explain how you get an IMU out of it.
- pclmulqdq 2y agoYou can do about 5x worse (in accuracy terms) than a Cesium clock in a smaller package using a rubidium atomic clock. Average ~4 of these and you get to the same accuracy as a cesium clock. They aren't export controlled because they aren't that special in terms of what you get.
- mapt 2y agoTo improve instrumental accuracy by 5x in a single dimension when fighting against random uncorrelated drift/noise, from what I recall of statistics you require 5^2 = 25x as many instruments.
- pclmulqdq 2y agoYeah, I think you're actually right. I was thinking you double them with 2 (experimentally), so you double that again to get 4x, but my curve was pretty off.
- fanf2 2y agoThe article is deeply confused. It’s true that optical clocks will improve the accuracy of our measurement of time, and it’s true that GPS depends on time, but there are several steps between primary frequency standards (ie, optical clocks) and GPS, and several more steps between GPS and navigation applications. So optical clocks cannot, in fact, have any effect on the end-user perceived reliability of GPS. For that, the best solution is to revive LORAN which is much less susceptible to jamming. (And would also benefit from better atomic clocks.)
- gbil 2y agoPersonally, I find it comforting that the plane was able to fly 400km more!