I thought the LPV vertical guidance was like an ILS glideslope i.e. no obstacles all the way to tarmac.
And the +V vertical guidance was a straight line from the FAF to the runway threshold, which usually clears all obstacles (we did this before a few times; IIRC there are some exceptions but they are rare).
Of course you should be visual at the DH, regardless, but if you are talking about a last-resort situation, landing is not optional.
The point is that the +V should be an adequate replacement for loss of LPV, especially in the extremely few UK cases. The termination of the Brussels authorisation paperwork is not going to affect the SBAS signal, of course, even if that was needed for +V.
I have only a sketchy knowledge on how this works but why can’t the UK do a deal with the United States and apply the correction to the US satellites – is that the WAAS system? We have the ground stations. Surely the EU hasn’t the monopoly on this?
The correction signal (the SBAS signal) is not transmitted by the GPS positioning satellites (whether they are the US Navstar system which practically everybody uses, or the European Galileo system which practically nobody uses). It is transmitted by a geostationary satellite(s) which generate/s a conical beam which covers only a patch of the earth’s surface. And the WAAS satellites (which transmit the correction signal for the US) don’t reach over to Europe.
The UK could rent a transponder on some geostationary satellite – like you do if you want to run a satellite TV station – and create its own SBAS signal, using as you say its monitoring station(s). Technically this is trivial. It is just money 
I have no idea of the cost but it is sure to be millions a year, and the main customers would be light GA (which doesn’t pay) and some low-end commercial ops in Scotland (for whom not having LPV translates to higher minima so perhaps a despatch rate down from 90% to 80% or some such). If NATS is involved in this, they aren’t going to go for it. They do nothing unless there is a “business case” and NATS is highly aggressive in operating this policy – just look at the dreadful radar service to GA in UK Class G.
Then I wonder if the GNS-W / GTN / IFD boxes we fly with can support new SBAS channels. They may have been hard-coded for WAAS+EGNOS, plus maybe the Indian and Japanese ones. @Stevavidyne might know.
I think there was a marine system where the local harbour sent the correction signal. Or perhaps this was a proposal many years ago
I wonder if an Airfield could transmit a correction signal just to cover that Airport?
Peter wrote:
would be light GA (which doesn’t pay)
Light GA does pay though, look at the amount of duty and tax on avgas.
Of course but I don’t think NATS gets it.
I am sure the politics behind this are not known to many and certainly nobody posting online. We can only guess how it came about. Could simply have been an oversight on the part of the UK to include it, and Brussels saw an opportunity. OTOH EGNOS is a massively expensive project, like all collaborative projects where there is political pressure to divide it up, and Brussels may have asked a lot of money for participation.
Archer-181 wrote:
I wonder if an Airfield could transmit a correction signal just to cover that Airport?
That’s what GBAS (Ground Based Augmentation System) does. With GBAS you can use GLS (GNSS Landing System) which potentially can offer CAT III capability. There are a few of these around, e.g. at Frankfurt. Norway was a pioneer and several airports in Norway have GLS.
Airborne_Again wrote:
Archer-181 wrote: I wonder if an Airfield could transmit a correction signal just to cover that Airport?That’s what GBAS (Ground Based Augmentation System) does. With GBAS you can use GLS (GNSS Landing System) which potentially can offer CAT III capability. There are a few of these around, e.g. at Frankfurt. Norway was a pioneer and several airports in Norway have GLS.
But! There are no GA-grade aicraft boxes, only for the airliners, and no plans to build them (at least for now).
PeteD wrote:
Maybe I’ve missed something….thought you needed to be be visual to descend below MDA/DA? Certainly was in my day!
What you state is correct, the point being you must be visual below the MDA. The +V is presented below the MDA and extends to the pavement, but there is no consideration for obstacles below the MDA and the path of the +V is not guaranteed or intended to avoid them. Below the MDA, one must be visual and avoid obstacles. There are airports in the US where following the +V below the MDA will take you through the obstacle or hill side.
Peter wrote:
And the +V vertical guidance was a straight line from the FAF to the runway threshold, which usually clears all obstacles (we did this before a few times; IIRC there are some exceptions but they are rare).
Not so rare in the US. +V is only intended for descent down to the MDA. The +V path is a straight line from the FAF at the minimum crossing altitude to the threshold at the TCH altitude. Use of +V below the MDA is a bad idea. In an emergency, one does what they need to do, but for non emergency use, this would be considered careless and reckless.
