Well, not quite comparable, because here Brussels has created the – arguably wholly artificial – Safety of Life Certification, and they have withdrawn that from the UK, which the UK CAA believes forces it to de-publish the LPV approaches, because they believe the SOL is a “real thing” without which they would not have a liability backstop.
The above is pretty obvious, because the signals are the same 
If you had a homebuilt LPV GPS, it would work just fine.
Everything else in this saga (e.g. why the SOL was withdrawn, etc) is speculation… Lots of stories going around, like £30M/year asked for by Brussels, which has never been evidenced.
Well at least the caa know what’s going on here:
https://publicapps.caa.co.uk/docs/33/EGNOS_V4.pdf
Oh wait…..seems to be some confusion about IAF & IF on page 4
That terminology was never going to end well….
(Not my spot)
PeteD wrote:
Oh wait…..seems to be some confusion about IAF & IF on page 4
Not to mention that they appear to think that integrity checking of the GPS is done by a system separate from the navigator.
Well at least the caa know what’s going on here:
https://publicapps.caa.co.uk/docs/33/EGNOS_V4.pdf
Yes; I posted that PDF further back, but the CAA never “owned” the LPV funding arrangements. They were involved in approving IAPs. AFAIK, and I read this somewhere, the EGNOS project was “owned” by NATS. This is all speculation but it seems very probable that if NATS were asked to pay more than £1 to provide a service which is mostly for GA they would say NO. As I wrote above, there is an ILS at every (?) UK LPV runway (albeit often only at one end) and a “benefit calculation” will quickly get you to LPV not being worth anything to almost everybody who pays money to NATS.
For example EGHI had LPV to 02 and 20 but has an ILS only to 20. So the Q is: who needs LPV to 02? Look at the minima.
RNP 02
VOR/DME 02 (flown by CAT using INS, and probably with a lower specially-AOC-approved minima)
It’s a no-brainer. LPV is basically worthless, because in the UK the DH is never anywhere near 200ft.
On the very few occassions that you cannot get in on 02, but could get in with LPV, you divert somewhere… probably Gatwick. And nearly all AOC (CAT) traffic going into EGHI cannot fly LPV anyway!
So nobody is going to make a financial case for LPV. It is of value purely to non-INS non-AOC non-CAT operators i.e. GA
Many years ago I read an argument against CAT3 capability in airliners. I think it may have been in the US. Some bean counter worked out that the chances of a diversion were 1 day in a year, and it wasn’t worth paying to upgrade the fleet.
PeteD wrote:
Oh wait…..seems to be some confusion about IAF & IF on page 4
That terminology was never going to end well…
That is the terminology used in the US as well. The only difference is that on most RNAV (GPS) (aka RNP) approaches, the center fix has a HILPT (hold in lieu of a PT) and when it does it is listed as both an IAF and an IF and charted as IF/IAF. I don’t see any confusion.
Well it confused the CAA….
PeteD wrote:
Well it confused the CAA….
In what way? IAP begin at an IAF.
Read page 4 of the document!
They call the IF the initial fix and the IAP the intermediate..
If the typical half deflection on a Localiser is the tan of 1.3 degrees, this translates to around 200 feet at minima on a 10,000 foot runway, while the 0.3nm on an LNAV is around 1,700 feet. The difference in sensitivity on an LPV which makes it a LOC equivalent is down to SBAS, and additional waypoints in the database. On an LNAV sensitivity ramps up to 0.3 nm in the run in to the FAF and stays there, whether the GPS navigator is WAAS or not.
Jeppesen will remove the additional dataset for UK LPV approaches, so while the WAAS GPS navigator can navigate to higher accuracy, it will fly the LNAV with the CDI having the same sensitivity as a non WAAS GPS.
PeteD wrote:
Read page 4 of the document!
They call the IF the initial fix and the IAP the intermediate..
I did not read that carefully.
