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Comment by rbanffy | Hacker News Reader

What kind of deranged person messes with GPS risking to crash an airplane?

The DoD wants to ensure their forces can operate if GPS is down.

This requirement should be reasonable to most people who aren’t pacifists. So I think the real question is, why aren’t senior level DoD and FAA bosses doing more to increase safety during the planned outages?

You can always disable GPS at the edges. Or almost always. And, for the rest, yes, they should at least be talking to each other and publishing NOTAMs when possible (and ensuring the FAA has it covered when it's a surprise drill).

OTOH, would it be possible to have other location services such as Galileo, GLONASS, and BeiDou available as backups (or letting they all vote on your position)?

I would hope GPS denial tests also include the alt-GPS systems. Who knows what hardware might have unknown dependencies (one would assume military hardware has all been audited, but assumptions make for poor battle plans.)

I shall consult the expert team at 4chan /s

But seriously "We've been told we can't ask to stop jamming, and to just put everyone on headings."... people inbound not ready for this can run out of fuel. Maybe the right passive aggressive response could have been to simply set a really large diameter TFR to keep civilian aircraft away assuming people check NOTAMs.

simply set a really large diameter

I'm not particularly familiar with aviation, so is the radius in this comment (445NM at FL400) considered large? (https://news.ycombinator.com/item?id=28833002)

Yes that is very large however that is just an advisory not a TFR. [1] Only those with special permission and Harrison Ford may enter into a TFR.

[1] - https://en.wikipedia.org/wiki/Temporary_flight_restriction

> people inbound not ready for this can run out of fuel

Shouldn't you always be ready for a GPS (or other instrument) failure?

Yes that's even part of the verbal/written test. You have to calculate fuel requirements to different distances and they give you options that would be technically right but check to see if you pick the conservative approach in the event of this very situation. If you want to see how many people toss that knowledge out the window listen to some of the videos at VASAvation [1] and instead choose to land on freeways, city streets, farm fields, etc... Not all of them are due to fuel, but some are.

[1] - https://www.youtube.com/c/VASAviation/videos

Instrument failures are rare and might impact a handful of aircraft; GPS jamming impacts every aircraft in the vicinity. ATC might have capacity to plan low fuel-consumption flight heading paths for a small number of aircraft, but not 100%?

ATC / radio failures happen. If ATC can't plan a route for you, you're still the pilot in command and responsible for finding a diversion airport and getting down safely, and for having had enough fuel to deal with traffic while doing so.

Sure -- I don't think the concern is literally falling out of the sky, so much as having to divert to another airport that isn't being jammed (inconvenient). But we're speculating on the basis of a vague complaint.

Of course you should be prepared for accidents, but it's quite another to be so prepared accidents don't turn into emergencies.

Would you be ok with a commercial passenger flight operating with 1 of the 2 engines completely disabled? It's technically designed to fly with 1 engine, so what's the problem?

Knocking out a pilot's GPS gives them one less tool in the event that other instruments fail. It's like saying "shouldn't you always be ready for backup hydraulics to fail?". Taking a backup system offline isn't an ideal situation.

> Would you be ok with a commercial passenger flight operating with 1 of the 2 engines completely disabled?

Yes. They are designed for that, and have procedures in place for when it happens, just as they do for a GPS failure.

(Specifically: https://en.wikipedia.org/wiki/ETOPS)

I would not be OK with a pilot who didn’t plan for the possibility of engine failure.

If you run out of fuel because your GPS is jammed, there’s a good chance you’d have run out of fuel if it failed in another more normal fashion.

You miss the point entirely. No commercial aircraft is going to be allowed to take off with only 1/2 engines in operation. If one goes out in flight they'll usually find a place to land bc it's understood that if that last engine dies then that's a bad situation. Which is the entire reason they have backups in the first place.

I'm not arguing about whether it's possible, I'm arguing whether it's smart. Airplanes have backups, and yes they can run on those backups, or else what would even be the point of having them? This kind of goes without saying...

If planes are DESIGNED to have backup systems, in case there is a failure, then do you think it's smart to arbitrarily remove one of said backup systems?

> No commercial aircraft is going to be allowed to take off with only 1/2 engines in operation.

That's a different question.

If you're knowingly flying into GPS jamming - these jamming operations are apparently announced via NOTAMs (https://news.ycombinator.com/item?id=28833002) - you should be planning ahead even more.

A pilot is responsible for having enough fuel in case of an emergency, like the GPS unit crapping out. Anyone running out of fuel due to GPS jamming was ill prepared for other emergencies.

Lol, I'm not saying pilots CAN'T operate without GPS (I fly hang gliders and I used to fly with literally no instruments at all).

Think of it this way. A person can live a normal life with 1 arm, 1 leg or even 1 eye or ear. Is it ideal? Probably not. If you lose your other arm, leg, eye/ear it's going to cause many more problems than just losing 1.

Losing any backups in aviation is a less-than-ideal situation. That was the only point I was trying to make. OF COURSE pilots can operate a plane without GPS, my god I'd hope they could. I feel like that kind of goes without saying.

You’re making a lot of specious arguments. I think your laymen’s logic checks out just fine here but that’s not how aviation works…and for good reason.

Taking off with 1 of 2 engines is a lot different than taking off with inoperative avionics. The FAA and airlines dictate what minimum equipment is required for any given aircraft to be airworthy and it’s a fairly robust document that takes into account myriad situations and flight conditions.

Yes and especially because planned GPS jams are published in NOTAMS, in my experience, well in advance of the event. Ignorance isn’t really an excuse.

From the article: "The Pentagon uses its more remote military bases, many in the American West, to test how its forces operate under GPS denial."

Wouldn't it just make sense to tell them not to use GPS?

That's like saying just pretend the internet is down. The goal is to find unanticipated uses.

Also, "jamming" can include sending distorted signals. These distortions can be a spoofed or malformed packet of data. Knowing what happens when a navigation tool suddenly thinks the vehicle is on the other side of the world is important. As is, ensuring that a garbage signal won't crash it.

Or less extreme things. Do the soldiers notice when their GPS shows them as half a mile away from where they need to be. In a slowly changing offset.

That wouldn't test the software, assuming cheating wasn't an issue

Is “them” civilian pilots or the soldiers? Because the military may have all sorts of equipment that has black box GPS functionality they can’t easily control (think of GPS guided munitions for example).

You know how we established radio-comms in the military? By debugging over cell phone links obviously :-)

The US military, per the article.

Makes sense. They don't seem to select for social responsibility.

> The complaints accused the FAA of denying controllers permission to ask the military to cut short GPS tests adversely affecting commercial and private aircraft.

The issue according to the article is with the FAA, not the military

I would expect the FAA to select FOR social responsibility. In the military, sociopathy is sometimes an asset. At the FAA it is inevitably a liability.

There was an issue a few years ago in Chicago where planes at the airport were losing GPS reception, which was eventually traced back to a truck driver who used a jammer to avoid fines based on GPS tracker data on the rental trucks he was assigned to drive.

He wasn't intending to crash an airplane, just avoiding docked pay for driving in traffic, using a $50 device bought online, and his route took him past O'Hare.

The perpetrators aren't playing around to try to crash an airplane, they're merely polluting an invisible commons in their own self-interest, and aviation happens to need that spectrum to be clean.

Well keep in mind that US GPS was developed by and is owned/operated by the US military. They're just letting us use it.

The military serves the taxpayers.

That doesn't entitle them to access to military systems, either individually or as a collective. And surely citizens of other countries are not entitled to access to military systems.

Surely it entitles the citizenry to access military-funded systems that do not benefit from secrecy, like GPS or the internet.

The military serves the tax payer by preserving their sovereignty.

It's nice that they allow civilian use of GPS, but it doesn't follow that they need to. It's perfectly acceptable to say that a civilian organization, government or otherwise, is responsible for providing satellite-based location services for civilian use.

The way GPS is operated is very unusual. The military doesn't provide satphone service to people around the world; are you arguing that they should?

Well the only reason military can own /pay for anything is because it takes our money in a first place. So unless there are specific security concerns civilians should be able to use whatever military tech they've paid for.

Military and government can pay for stuff also using deficit spending, which is not "our" money. It's either FED's money which they create (and thus steal value from us) or it's borrowed money from wealthy interests.

Half-joking that Uber and [Tech Major]s' Map products are among the greatest government subsidy stories of all time. Those satellites are expensive!

I wish I could use my phone on GPS only. Somehow the damn thing still needs a cell connection despite having the hardware allegedly.

You can, you just need to download the maps for offline use. Google maps makes it easy:

https://support.google.com/maps/answer/6291838

It's very useful for navigating crowded touristy areas, remote nature preserves, sports/music events that jam the towers, etc.

Some more specialized apps also support doing the same thing with other types of maps, like USGS quad sheets.

I wish you could download a lightweight map of the entire country. The way the selector rectangle works in my city makes it awkward to capture it well since its kinda longer east west rather than north south. If a garmin from 2002 could hold maps of the entire country, surely my iphone with 512gb of storage should be able to do it too.

Use OSMAnd instead, it can download entire country map with a click without dragging rectangles around

I'm still surprised when people are still surprised that this exists.

No plane is going to crash because it doesn't have GPS. Aircraft have other ways to navigate.

Governments messing with other governments?

I think it’s for military protection. I had a flight canceled due to GPS jamming. I think it was to protect a U2 flight. Putin also flies around with GPS jammers.

Wouldn't that mean that Putin's flights can't use GPS to navigate? But maybe he worries more about someone intercepting his plane than he does about crashing due to a navigation mistake. And his risk assessment may in fact be accurate...

You can jam 99.99% off the time except when your software takes a reading. So you get clear signal everyone else can’t.

I'm not sure that'd work very well as the primary strategy. A hot start can take 20+ seconds and the attacker has no particular advantage in time to fix when the interference stops.

I'd assume a russian military plane would primarily use GLONASS. GLONASS has the advantage of being more resistant to narrowband single tone jamming because it uses FDMA rather than CDMA like GPS. The signals are also in slightly different frequency ranges.

Obviously we navigated acceptably, including aircraft, long before the development of GPS in the 1970s. GPS is easy and precise and can make risky edge cases (like very low altitude flight) safer or allow higher density in air spaces and such, but it's not necessary particularly not at the government aircraft level. Inertial guidance, ground based Doppler navigation systems, and even automated celestial navigation in combo can produce great results just at a much, much higher expense. That isn't an issue for the leader of a major power though.

The SR-71 was a cool example of a system that used a hybrid of automated celestial navigation and inertial. Fully self-contained.

Presumably Putin's flights, on Russian-built aircraft (specifically the Il-96), use GLONASS?

Of course, the VC-25A used as Air Force One has a cockpit station for a navigator, specifically so that it can use old-style navigation methods if access to GPS and other navigational aids is lost. Putin's modified Il-96-300PU may well also have one.

Yeah, the original 747s flat out had a sextant port in the roof. Could navigate by the stars the old fashioned way. Given how crazy precise (and expensive) inertial guidance systems were developed for ICBMs in the Cold War I have to imagine though they have one on Air Force One, along with an automated celestial guidance system for recalibration. The AIRS (advanced inertial reference system) used in the LGM-118A Peacekeeper missiles have to be some of the most mindblowingly precisely made machines in human history. Drift of something like 1.5/10000° per hour! .003° per week (not that they'd ever run that long obviously, ICBM and all). At any rate, highly precise IGS is doable for enough money, even with older tech though these days I'd assume they're using fiber optic gyros or something like that. It's a neat area.

It should be possible for the jammer to subtract off its own signal rather more effectively than anything which doesn't have access to the pRNG it uses to generate the interference.

The thing is, GPS signals are really weak at the receiver. They're technically below the noise floor, and receivers have to use shenanigans to get a usable signal at all. If you're transmitting the jamming signal, you're really close to it, and therefore it is really strong near your receiver. I wouldn't like to calculate how many orders of magnitude stronger than the real GPS signal, but it would be a lot. Generally, subtraction works when the two signals are similar in strength, and you still lose definition in the received signal. GPS signals are so on the borderline of being able to be received that this would just not work at all.

> They're technically below the noise floor, and receivers have to use shenanigans to get a usable signal at all.

This is nonsense.

There are other accurate systems for navigation available for aircraft, like the network of Non-Directional Beacons (https://en.wikipedia.org/wiki/Non-directional_beacon). It's a bit more of a pain in the butt to fly, because you're going from waypoint-to-waypoint, rather than a course relatively towards your destination, but it was how we did aircraft navigation up until relatively recently.

The same kind that shines laser pointers in planes?

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