8 things that are disappearing from airplanes

tomjnx wrote:

We now (or soon) have 3 independent GNSS systems (GPS, Glonass, Galileo) operating on many different frequency bands. What is the (realistic) threat model that all three systems fail simultaneously?

Something like this.

Airborne_Again wrote:

Something like this.

What makes you so confident that a large coronal mass ejection like this will completely knock out GNSS but not affect VOR or NDB?

• GPS alone operates in three different civilian accessible frequency bands, while VOR and NDB each only use one

• Lower frequencies (what NDB and VOR use) tend to be more affected by ionospheric effects; effects like Mögel-Dellinger, nighttime missing D layer, sporadic E layer all affect NDB, VORs even without any large scale CME event

• If you look at CME papers, they seem to measure CME radiation mostly in the 100-300MHz frequency range – where VORs lie, but far away from GNSS

• Even if a CME event could knock out all satellites in sight (which I doubt, given that the satellites are already in a harsh environment with little atmospheric protection, so they must be quite well protected), it would still only knock out half the fleet of SVs; so chances are degraded navigation would be possible relatively quickly after such an event.

• The bigger problems might be the user equipment. There’s a chance that in aircraft receivers may be damaged. But there, I expect GNSS to have a much higher survivability due to the sheer number of GNSS receivers; a typical GA aircraft has 2 VOR receivers, 0-1 ADF receiver, and with 2 people on board probably 10 GNSS receivers…

tomjnx wrote:

What makes you so confident that a large coronal mass ejection like this will completely knock out GNSS but not affect VOR or NDB?

I’m not thinking of temporary interference effects but of damaging the satellites. VOR and NDB transmitters are located on the ground and are much more protected thann satellites which are in space.

Anyway, I am not confident about anything. I just gave a “realistic threat model”.

If CME were a realistic threat airlines would account for it. They do not.

Airborne_Again wrote:

I’m not thinking of temporary interference effects but of damaging the satellites. VOR and NDB transmitters are located on the ground and are much more protected thann satellites which are in space.

Really?? I doubt it.

We do account for it. We have IRSs, which will get us to a safe landfall to VOR land, and so on. All sorts of contingencies and requirements when going oceanic.

And it IS a realistic threat. Satellites aren’t exposed to those levels of radiation normally at all.

tomjnx wrote:

What makes you so confident that a large coronal mass ejection like this will completely knock out GNSS but not affect VOR or NDB?

GNSS signals are several orders of magnitude weaker than VOR and NDB. GNSS signals penetrate the ionosphere, while VOR and NDB are largely below it. I don’t think a powerful solar storm would damage the satellites themselves, or knock GNSS out all over the globe, but the places around the poles – Iceland, Greenland, northern Canada – would be especially vulnerable.
A good backup to GNSS for such problems would be eLoran, if and when it comes into being.

In a 100 year solar storm, you might well lose electrical grids as well. Are NDB/VOR installations typically covered by backups?

Ultranomad wrote:

GNSS signals are several orders of magnitude weaker than VOR and NDB

Yes, but so is the path loss from the sun, given that higher frequencies have a bigger attenuation.

Ultranomad wrote:

GNSS signals penetrate the ionosphere, while VOR and NDB are largely below it.

I find it a bit hard to argue VOR/NDB won’t be affected by large scale CME when they are already affected by effects of normal scale CME we experience every year, namely by tropospheric ducting and sporadic E, in the VOR case.

Ultranomad wrote:

A good backup to GNSS for such problems would be eLoran, if and when it comes into being.

That is the propaganda of the eLoran crowd, at least. However, IMO, they operate in the worst possible frequency band. It transmits in a frequency band where switch mode power supplies operate. The world is full of high power switch mode power supplies such as modern electric train locomotives, solar panel installations etc. So that frequency band will get increasingly unusable in populated areas. The real purpose of eLoran IMO is to get further funding for the General Lighthouse Authorities of the UK.

kwlf wrote:

Are NDB/VOR installations typically covered by backups?

While Annex 10 Vol 1 Attachment C Section 8— does require a secondary power supply (with 15 seconds switch over time) for navigation aids used for approaches, it IMO does not require backup power for enroute navigation systems. And IMO that secondary supply does not necessarily be a local power source, could be a second grid attachment too.