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GPS Jamming Report, Korea

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GPS Jamming Report, Korea

Old 2nd May 2012, 12:56
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GPS Jamming Report, Korea

Read an article in the news that concerns me. This is a non trivial safety issue that probably isn't confined to North Korea.

World News - N. Korea accused of jamming commercial flight signals

If the GPS signal is being jammed while you are in the terminal area, what does it look like in the cockpit when the signal begins to go wrong.

Do you get caution lights or warnings or ECAMS notifications?

More importantly, how often does this happen and you, as flight deck crew, are not aware?

I suspect that by the time you are on the ILS, a GPS jam probably would not materially influence your approach, but what about if you have to do a missed approach? If GPS is being jammed, how will you know?

Have any of you experienced this?

As I am not sure what the NORKERS are jamming, nor how, perhaps all that happens is that one of the signals feeding your system goes unreliable, but there are enough signals from the constellation to allow the system to remain effective.
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Old 2nd May 2012, 13:33
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The UK has been running GPS jamming trials north of London for a year or so now. There's been a NOTAM on and off warning crew to disregard GPS in the area (which includes Stansted Airport).

but what about if you have to do a missed approach?
You're kidding, right?
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Old 2nd May 2012, 13:36
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Have any of you experienced this?
Yep flying into Stornoway in Scotland they have an exercise every year were the GPS is jammed on and off for two weeks.

To be honest it can happen anywhere in the UK. The was a little scrot in the Isle of White that had a jammer for about 3 months or it could have been the navy range areas.
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Old 2nd May 2012, 15:06
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Experienced a similar GPS jamming out of Calicut and Jeddah recently. Nothing on the Notam though. ATC didnt have a clue either.
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Old 2nd May 2012, 16:40
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[SLF]: what ever happened to inertial nav (INS)? There was a time when that was the miracle that got airliners across oceans within a km or so of intended.
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Old 2nd May 2012, 16:51
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It's still there, it drives many of the flying instruments as well as providing back-up to GPS.
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Old 2nd May 2012, 16:56
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We have the problem on a regular basis operating around Syria (officially no jamming takes place but still the faithful GNSS goes kaput more often than not around there)... The 737NG gives a scratchpad message, (GPS L/R INVALID) and will stop updating from there. ANP will go up obviously. On most of our planes the DME-DME updating is off by default, worth checking if you are planning to stay in the area for longer

Last edited by STBYRUD; 2nd May 2012 at 17:56.
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Old 2nd May 2012, 17:41
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what exactly is the purpose of doing this?
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Old 2nd May 2012, 17:44
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If you thought someone was likely to shoot GPS guided cruise missiles at you, I think you would soon work it out, Irish
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Old 2nd May 2012, 19:26
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Checkerboard:
It's still there, it drives many of the flying instruments as well as providing back-up to GPS.
Yeah, I kind of realized that. My thought was that if steam-powered 1980's INS could get one through some 8 hours of flight with a km of accuracy, by 2011 better solid-state gyros and hugely better computers could, if desired, know the state of the platform with sub-meter and fractional-degree accuracy and thus internally* provide for all the navigation one would need up to Cat III landings. (*perhaps granted an external fix now and then to take care of any long-term drift that the platform might still be guilty of.)

As an extreme example it was noted during AF447 discussions that the inertial stuff knew the a/c was seriously pitched up, but wasn't designed to mention it to the humans. (If I understood that correctly.)

Countering my suggestion is the presumed fact that the military continues to use GPS for delivering ordnance to target. But that might mean that GPS is "good enough" and cheaper - a factor for their single-use toys, or that I don't know what they're actually using, or just that no one has given Lockheed or Boeing some money to look into the alternative, or that GPS is the sexy Thing du Jour.
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Old 2nd May 2012, 20:09
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STBYRUD - you said
On most of our planes the DME-DME updating is off by default
Why is that?? I don't have a lot of experience of state-of-the-art navigation, but on the only type I have flown with FMS updated by GPS, DME/DME, and laser inertial, the manual definitely said that DME/DME is the most accurate - makes sense that it would be more accurate than GPS as it is basically the same method of determining position, but from fixed position beacons rather than ones flying round in space..........
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Old 2nd May 2012, 20:45
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Thanks for the responses.

I guess most modern airliners have inertial nav ... so my Terminal Area question is covered by another system.

The question initially came to me as something like "do the children of the magenta line" have a back up plan if the GPS goes whack, but that wasn't a very good question, it turns out.
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Old 2nd May 2012, 21:26
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the manual definitely said that DME/DME is the most accurate
DME/DME is more accurate than GPS, really? That's a bit of a surprise, what type and brand of FMS manual stated that? I'll admit it has been five years since I have retired, but it was my understanding that the GPS was the most accurate navigation system one could have.

Have things changed that much?
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Old 2nd May 2012, 22:43
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INS/GPS

Any little chav can buy a GPS jammer, there small enough now to be concealed in a fag packet and be able to block GPS receivers for approx 5kms. I'm no expert on the nav systems of modern airliners but i'll hazard a guess that they work the same as most INS/GPS systems?
If so then when the INS initialises to it'd start state, when ever the laser gyros detect movement in the linear, and vertical plane it is able to provide a direction and distance travelled by the movement of the gyros. The GPS system just aids in the correction of any errors in the INS. This is a very basic principle behind any INS/GPS system, even down to precision guided weapons. The faster something travels the more inherent GPS lag is, so the missile has moved past and beyond where the GPS has just said where the missile has been, with out the INS system the phrase a dog chasing it's own tail springs to mind.
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Old 2nd May 2012, 23:18
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FMC and GPS position always seem to coincide the times I have checked. The navaid updating is usually pretty accurate as well but not to the same degree as the GPS and depends on navaid coverage. The IRS is the least accurate and after a few hours could be a couple of miles off. Sometimes they even come and go, had one IRS that had been reported dodgy drift something like 3 miles off in 30 min to eventually end up within a mile or so of the aircraft position at the end of the day… randomly of course.
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Old 3rd May 2012, 09:42
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Obviously a GPS update is more accurate than DME updating, the story I have been told is that when DME updating is on together with GPS it only degrades the actual navigational performance by introducing another source with a certain uncertainty... The problem is that in said area the authorities are planning to roll out RNP-GNSS approaches
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Old 3rd May 2012, 12:09
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One HARM would do the job nicely...
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Old 3rd May 2012, 16:22
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GPS at its best
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Old 3rd May 2012, 18:56
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Countering my suggestion is the presumed fact that the military continues to use GPS for delivering ordnance to target. But that might mean that GPS is "good enough" and cheaper - a factor for their single-use toys, or that I don't know what they're actually using, or just that no one has given Lockheed or Boeing some money to look into the alternative, or that GPS is the sexy Thing du Jour.
There are different guidance systems depending on the job and the threat environment. Laser, INS, GPS, GPS/INS systems, electro-optical, CCD, IIR, etc.

You don't think the military would put all eggs in one basket, now would you?
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Old 3rd May 2012, 21:22
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poorjohn,

As an extreme example it was noted during AF447 discussions that the inertial stuff knew the a/c was seriously pitched up, but wasn't designed to mention it to the humans. (If I understood that correctly.)
Wasn't designed to mention it... apart from the big artificial horizon display in front of each pilot you mean?
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