I take your word for it! But thank you 
Note that the Visual approaches were still listed as choices when WAAS was disabled.
From here
They should allow +V to be used as the precision approach in IR training and tests
Yes it’s executed as 3D in LNAV+V but the glide path is not protected nor official, if that is not an issue for training you can argue that NDB flown CDFA on 3D GPS overlay or GTN visual approach to Damyns Hall would fit the bill for precision approach during a UK IR exam
In the other hand, L/VNAV is a different league though: LPV with SBAS degradation to L/VNAV with SBAS has never happened in history of GPS (I will let @NCYankee confirm if he ever heard of such thing observed in real life?)
LPV degradation to LNAV is more common, I never saw one but some people with thousands of IFR hours did saw it once or twice…
Although it is technically possible to implement a downgrade from LPV to L/VNAV, I am unaware of any manufacturer that does so. They all implement downgrading to LNAV without any advisory vertical guidance. The reason is simple, the VAL required for L/VNAV and LPV is the same, 50 meters. LPV200 has a 35 meter VPL, so when the LPV DH is less than 250 feet, it would be feasible to downgrade to L/VNAV, but not worth the effort IMHO. Downgrading can be due to either HAL or VAL being exceeded, but since VPL is almost always worse than HPL by a factor of 50% due to geometry, I don’t think I have ever seen a case where HPL exceeds HAL before the VPL exceeds the VAL, which would have to be the case for a downgrade from LPV to L/VNAV. Now that the TSO allows +V when not in an SBAS service volume, a downgrade to LNAV+V might be allowed with a poor VPL as the vertical guidance is only advisory and almost any vertical path used to get to the MDA of an LNAV would be satisfactory as long as the pilot understood that it was illegal and hazardous to use the +V below the MDA (There are approaches in the US where you will hit obstacles or terrain following the +V below the MDA).
Isn’t +V some garmin virtual glideslope thing and it has nothing to do with a real IFR vertical guidance procedure?
Yes but for training & practice flying +V or “real glideslope” are executed the same way? in the same way as using simulator IFR is like real IFR…
On windy & bumpy IMC days, I can go and practice flying the final segment & missed at 6000ft agl on some random waypoint, I just set 0.3nm on CDI scaling & VPATH/VNAV and bang on it as much as I wish (better than doing the same near ground in windy & convective IMC or on sunny days where you spend the whole time watching for traffic unless there is an ATC but then you don’t get to fly as many descents & go-arounds as you want), I could do 10-20 attempts at 6kft in real windy & convective IMC in one single flight, I could also fly LNAV+V to any airport and fly as much as I can on a home simulator with XPlane + Brunner Yoke
None of the above are official vertical guidance but the associated skills seems to work fine for real IFR (as long as one know the theory and differences between LNAV+V, ENR 0.3nm VNAV, L/VNAV and LPV and can add the ATC/RT layer)
Or maybe it’s the question of what works for initial IFR training? vs what works to maintain IFR hand flying currency?
How about PPL PFL training? should we pull the mixture to make it a real glide
Isn’t +V some garmin virtual glideslope thing and it has nothing to do with a real IFR vertical guidance procedure?
+V is a straight line from FAF to MAP, raised if necessary to be above any SDFs in between the two.
So it is safe to follow it, all the way down to the published nonprecision (SDF) IAP. Modern avionics can fly the +V coupled, all the way down to, AFAIK, the tarmac. At a few airports, there are obstacles below the MDA. And with the latest firmware you don’t need the EGNOS signal, so it gets around the Brussels restriction on the UK.
It is what airlines have in the big jets. They get an “ILS” into say Kefalonia. However, they general have lower minima than the published Jepp IAP.
Unfortunately +V is not accepted, anywhere AFAIK, for an IR test.
Although it is technically possible to implement a downgrade from LPV to L/VNAV, I am unaware of any manufacturer that does so.
In the UK, the LPV procedures have been removed from the Jepp data anyway, AFAIK, so a downgrade situation can’t arise. You start with +V and fly that.
Outside the UK, this could happen, so I guess some fast “button work” might be needed. I wonder how much is involved in switching from a “failed LPV” to +V (whose “GS” will probably be above the LPV GS), or is it so complicated one has to go around? With some autopilots you cannot re-intercept any lost GS after the FAF, because they need to see a LOC and only then they switch to GS.
raised if necessary to be above any SDFs in between the two
I am not sure that is true, do you have a reference to this? Glocs +V does not show on GPS (I was under the impression as it penetrates MDA steps inside the hill)
Maybe Greece airliners with their FMS have the capability to have a “steep +V” that stays above the MDAs but surely it’s not the case in GTN/IFD
If ever that +V worked in Glocs, the CAA would have adapt it as tool in “3D training” for CBIR & MEIR due to the big demande in that corner
Done before in various threads. +V is good until the NP MDA.
Snoopy wrote:
Isn’t +V some garmin virtual glideslope thing and it has nothing to do with a real IFR vertical guidance procedure?
It’s a “Garmin thing”, but it’s supposed to be the vertical path you should follow on a CDFA.
