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Chat Area => General Discussion Area => Topic started by: Varche on 04 September 2025, 18:16:06

Title: China
Post by: Varche on 04 September 2025, 18:16:06
I am surprised no one has commented or about gps jamming on planes.

Title: Re: China
Post by: STEMO on 04 September 2025, 19:48:24
I am surprised no one has commented or about gps jamming on planes.
Someone just has  :)
Title: Re: China
Post by: Marks DTM Calib on 04 September 2025, 21:08:18
It wasn't jamming, it was spoofing  :y
Title: Re: China
Post by: Doctor Gollum on 05 September 2025, 12:05:29
Flying to India there's no reliable GPS after Turkey.

Which highlights the unintended consequence of Airbus fitting a GPS based auto descend system to the A350 that descends the aircraft automatically following a decompression...

A very real possibility of hitting the mountains.
Title: Re: China
Post by: Viral_Jim on 05 September 2025, 12:14:20
A very real possibility of hitting the mountains.

My understanding is this only kicks in if no pilot intervention post decompression.

It also drops the aircraft to the greater of 10,000 ft or Minimum Enroute Altitude, which is route-based and set prior to departure, so barring a system failure, or an incorrect route being set (seems unlikely as significant deviations from route would trigger alerts) then the plane won't drop itself low enough to interface with the scenery. 

I'm sure LC will be along in a minute to offer further commentary  :)
Title: Re: China
Post by: Doctor Gollum on 05 September 2025, 12:42:48
The 350 does it automatically and they have to tell it not to. We have to allow them time to make contact because the descent itself isn't indicative that they're flying.

Everything else we operate has to be manually descended so you have to wait ~80 seconds before checking the flight crew are ok if nothing happens fairly quickly.
Title: Re: China
Post by: Marks DTM Calib on 05 September 2025, 15:18:08
Flying to India there's no reliable GPS after Turkey.

Which highlights the unintended consequence of Airbus fitting a GPS based auto descend system to the A350 that descends the aircraft automatically following a decompression...

A very real possibility of hitting the mountains.

That makes no sense, the GPS GNSS constellation covers the entire globe, as does Galileo, Glonass, BeiDou etc.

In fact, pretty much every receiver on the planet needs to see a few GPS satellites in order to achieve positioning on the other constellations.
Title: Re: China
Post by: LC0112G on 05 September 2025, 15:37:05
I don't approve of GPS for anything critical. Far too easy to spoof the civil variant, and jam the military equivalent. You can also derive altitude from GPS, and some aircraft systems are starting to use it as input to the flight manegment system - i.e. effectively the autopilot. There are reports over on PPrune of pilots getting 'terrain avoidance' instructions whilst happily bimbling along at 37,000 feet. What exactly are you going to bump into at FL370?

An alarming number of systems also get their time signals from GPS. If GPS stuffs up (either accidentally or through spoofing/jamming) then all types of systems fall over, and an airborne reset is often either not possible or advised against.

The specific problem in this case appears to be known but being kept quiet for whatever reasons. The aircraft spent about 10 minutes extra airborne (not hours) but the ADSB output indicated a good GPS signal throughout. Something obviously happened to the onboard systems which caused the pilots to think the GPS was unreliable, forcing them onto backup systems. Unfortunatly, Plovdiv is a sh1thole (yes I've been there - Mil8/24 base) and most of the other NAVAIDS there were already off line, so AIUI their choices were a Military PAR (Precision Approach Radar - effectively a talk down, left a bit, right a bit, up a bit, down a bit) or a visual approach. The jet in question is civil regisered, but operated on behalf of the Belgian Military so I've no idea what the pilots are allowed to do.

Interestingly, the main Bulgarian fighter base (Graf Ignatievo) is about 10 miles north of Plovdiv. I'd be surprised if the Bulgarian military don't know exactly what happened, and that's why they are trying to shut down the story.
Title: Re: China
Post by: LC0112G on 05 September 2025, 15:44:24
Flying to India there's no reliable GPS after Turkey.

Which highlights the unintended consequence of Airbus fitting a GPS based auto descend system to the A350 that descends the aircraft automatically following a decompression...

A very real possibility of hitting the mountains.

That makes no sense, the GPS GNSS constellation covers the entire globe, as does Galileo, Glonass, BeiDou etc.

In fact, pretty much every receiver on the planet needs to see a few GPS satellites in order to achieve positioning on the other constellations.

There are lots of systems, mostly military, designed to either jam or spoof GPS. The main reason is that many drone and missile systems have been developed for attacking targets using GPS to navigate. If you can spoof or jam the GPS signals over an area then you can stop those drones/missiles finding their targets.

The UK CAA regularly publish NOTAMS about GPS jamming even in UK airspace - usually related to NATO exercises in the North Sea or north of Scotland. There is a big exercise happenig later this month so GPS jamming NOTAMS should appear shortly.
Title: Re: China
Post by: Marks DTM Calib on 05 September 2025, 16:02:08
Jamming is not such an issue as it is easy to detect, the spoofing is more of an issue, we are starting to see spoofing used in car theft now
Title: Re: China
Post by: LC0112G on 05 September 2025, 18:07:47
Jamming is not such an issue as it is easy to detect, the spoofing is more of an issue, we are starting to see spoofing used in car theft now

It is an issue in aviation - many of the newer approach procedures (called RNAV) rely on GPS, and the problem is that if the GPS signal is interrupted/spoofed anywhere along the route then the onboard systems' GPS is considered unreliable, and a RNAV approach cannot be performed. The systems cannot be reset in flight.

As DG says, GPS is routinely 'unreliable' over most of the middle east (Israel, Afghanistan, Iran, Iraq), and with Russian and Ukrainian airspace being off limits to western airliners there aren't many eastbound from Europe long haul flights which aren't affected.
Title: Re: China
Post by: Doctor Gollum on 05 September 2025, 23:02:40
Going east, we either thread the needle across the top of Persia or over the UAE.

If something serious happens there's a very real chance that the aircraft won't be returning home.