Harassment of Civil Traffic

[Stoker]

2 hours ago, herkbier said:

Not an airline guy.. forgive the elementary question.
 

Why is there no ability to exclude the GPSs? Or ability to remove the bias introduced into the INU? Inflight alignment? What do you do if you lose power in flight and have to reboot?

You can set GPS updating to off, which means you're just flying old school off of INUs, VOR/DME updating (which you can also turn off, though those haven't really been spoofed lately). Which is going to restrict you from certain airspaces, approaches, etc. Current procedure seems to be turn off GPS updating when you notice spoofing, but while there are cues you're being spoofed, it isn't as clear as a Master Caution saying GPS SPOOF. So you fly through it for an hour and get infected INUs. You can't remove the bias from the INUs because they need a solid reference point to start from - an airport, gate, lat long, etc. I don't know of any FMS out there that lets you reenter that reference point in flight - not really sure how you'd do that given the speeds we move at.

[Boomer6]

3 hours ago, Stoker said:

not really sure how you'd do that given the speeds we move at.

In some old school systems you can do this by overflying a point with a known lat/lon (VOR/airfield etc.), setting said lat/lon, and updating the INS when over the point. Essentially telling the INS, "here's our location, now do math.." 

It's not something that you're gonna fly an RNAV from, but it'd be a lot better than having your pos be over BFE when you're on final at ATL.

[SurelySerious]

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[Smokin]

16 hours ago, Stoker said:

I don't know of any FMS out there that lets you reenter that reference point in flight - not really sure how you'd do that given the speeds we move at.

You would do it the same way the F-16 EGI works with an in-flight align.  For an airliner, once you're out of the jamming, you do an in-flight align and the INUs takes the input data from the user and GPS.  You input the heading and maintain straight an level flight for a few minutes while the GPS talks to the INUs.  It is very possible as there are platforms that have this capability, but the airlines/FAA haven't seen it as a big enough problem to force the capability (i.e. spend the money for it).

[Clark Griswold]

C-27J could do this also, overflying known lat long and could do a radar offset update off a known location
Honeywell avionics IIRC and then I guess the J model Herc could I imagine


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[Stoker]

The question is, what RNP does that in-flight reinitialization give you? If it's still higher than a mile, not particularly useful since you're still heavily restricted. Might as well stick to INUs with GPS updating off.

[Smokin]

The inflight align is capable getting you back to about the same accuracy as a ground start.  I've seen it back inside low double digit feet accuracy within minutes.

Overfly fix would not be practical for an airliner.  Passengers would get upset at dipping a wing to see straight down.

[polcat]

23 hours ago, Stoker said:

GPS spoofing effectively tells the FMS that the INUs are all off by some degree and should correct their position. Once they change to match the bad GPS signal, even once the spoofing ends, they can't go back to their original, correct position, which means that for the rest of the flight you have the FMS interpolating between good GPS and bad INUs for position, so you won't ever get a really good solution.

https://ops.group/blog/nat-crossing-after-gps-spoofing/

Thanks for the link. Never dealt with GPS spoofing myself. In the C-130J, we just deselected our GPS's to simulate a GPS degraded environment and used the radar or visual aimpoints to update the aircraft's position. Easy peasy.

[polcat]

5 hours ago, SurelySerious said:

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[Clark Griswold]

Some 20 lbs brain has probably already worked this out but a C2 node or radar facility could push an update in a degraded nav environment if they had positive contact with a receiver(s) and the receiver held course/altitude/speed and updated accordingly when they overflew the pushed update
Military application is obvious but I wonder if the commercial world could get this worked out with CPLDC or ACARS


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[Stoker]

1 hour ago, Clark Griswold said:

Some 20 lbs brain has probably already worked this out but a C2 node or radar facility could push an update in a degraded nav environment if they had positive contact with a receiver(s) and the receiver held course/altitude/speed and updated accordingly when they overflew the pushed update
Military application is obvious but I wonder if the commercial world could get this worked out with CPLDC or ACARS
 

That's basically LORAN, right? We de-commissioned that, because there's no way we'd ever lose GPS capability and it cost like a hundred million dollars a year to operate - which is just crazy money for a useless backup. /s

I worry about the security of CPDLC and ACARS though... if bad guys will spoof GPS, why not a message to turn right 30 degrees for traffic?

[Clark Griswold]

That's basically LORAN, right? We de-commissioned that, because there's no way we'd ever lose GPS capability and it cost like a hundred million dollars a year to operate - which is just crazy money for a useless backup. /s
I worry about the security of CPDLC and ACARS though... if bad guys will spoof GPS, why not a message to turn right 30 degrees for traffic?

No LORAN is not exactly what I’m imagining

https://en.m.wikipedia.org/wiki/LORAN

I’m thinking of a station, probably stationary or in a tight and unchanging orbit, actively measuring BRA to another station keeping its heading/altitude/speed, doing trig and telling the receiver in 0.69 seconds input this position as your origin point and nav from there

This system would be mostly silent except for maybe its radar and have to have some freq hopping encryption to transmit as required, unpredictably to its users for their nav updates and not give the baddies something easy to target


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[HuggyU2]

On 9/25/2024 at 9:34 AM, SurelySerious said:

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Haha, this. 
 

The U-2 and SR-71 had an old but great Astro-tracker.  We flew it on missions that went way north, where there was always overcast (which precluded doing a ground fix update), and before GPS was really integrated into military flying ops.
 

I believe it was maintained by Northrop. 

IIRC, it tracked 300 stars and gave us around 700' of accuracy. I had an engineer tell me a few years ago that 700' is terrible, compared to modern standards. 

Unfortunately, airline certification for an Astro-tracker will take decades and cost millions of lives. Too bad. Works great, lasts long time. 

Edited October 2 by HuggyU2

[brabus]

51 minutes ago, HuggyU2 said:

I had an engineer tell me a few years ago that 700' is terrible, compared to modern standards. 

Pictured: Huggy when he is told 700’ is dog shit position quality

[herkbier]

700’ = 0.11 NM

What a twat