I get LNAV+V in raw NDB approach flown on magentas, what I should call that?
You can get +V displayed and flyable with an autopilot, on a runway which has only an NDB approach, and no GPS approach? Where is it, and with what avionics?
I know airliners and some higher-end bizjets have this.
With the GTN Xi series, the database includes conventional approach procedures and for straight in approaches, they provide LNAV+V GPS guidance. To legally fly the procedure using the GPS for navigation, the ground station (VOR or NDB) must be operating and a separate VOR or NDB indication from a bearing pointer or CDI must be used to monitor the course alignment. So it is a GPS version of the conventional procedure, it annunciates as LNAV+V.
GTN show LNAV+V to all runways with straight-in (G430W show LNAV+V in few cases where NDB is coded in the database by Jeppsen, not lot of offset, and it has a published FAF in plates)
I don’t think AP matters much? it worked with KAP140 and GFC500
With the GTN Xi series, the database includes conventional approach procedures and for straight in approaches, they provide LNAV+V GPS guidance
I should have done more homework, where does gradient profile for those +V comes from? best fit on AIP IFR plates recommanded profile, or some Jeppsen proprietary FAS data block, or it’s Garmin implementation of some hard-coded glide or calculations? 
I recall “Visual Approach” use hard-coded 3deg from Garmin and only show +V when it does not penetrate obstacles…
Ibra wrote:
GTN show LNAV+V to all runways with straight-in (G430W show LNAV+V in few cases where NDB is coded in the database by Jeppsen, not lot of offset, and it has a published FAF in plates)
+V with a VOR/NDB straight in procedure was introduced with the GTN Xi. It is not available with the GTN and is not available with the GNS series. This was one reason I upgraded from the GTN 750 to the GTN 750 Xi.
My bad, it’s NXI that has it when you load from NDB from DB or when you set “Visual Approch”
G430W/530W do not have it for NDB, only LNAV+V for RNP !
Is this available in “Perspective G1000nxi” for Cirrus? they had few GTN features released in G1000…they also have BARO-VNAV in G5/G6 models, will that generate LNAV+V on NDB overlay?
I do find the terminology and the inconsistency of different people’s use of it confusing, but no argument from me that having +V guidance is v helpful! I suspect though there are pilots who see the annunciation and treat it as primary rather than advisory. Not sure if that’s really a safety issue or not.
On the question of EGNOS accuracy, I still don’t get the assertion that it doesn’t improve accuracy of GPS. I don’t know enough of the technical details to argue either way, I’m just genuinely curious to know whether that is really the case.
Yes you are not supposed to fly advisory +V bellow LNAV MDA
Above MDA (or MDAs altitudes) following +V does not hurt
Peter wrote:
WAAS should be better because the sats participate in the 3D solution, but here we have EGNOS which doesn’t.
What exactly does that mean? That WAAS satellites work as regular GPS satellites beside sending the correction signal?
Are there so few regular satellites available that the addition of the WAAS satellites actually matter?
Or does it mean that they WAAS satellites “participate” in the 3D solution in some other way?
Yes.
Probably not, but that is how it was done.
Not AFAIK. At the receiver end, whether the signal comes from a geostationary sat or an orbiting sat, is transparent. IIRC, some countries have done geostationary positioning entirely – India? Not sure. For one country, it is nice and cheap.
I posted an update here.
The SBAS signals use the L1 frequency and provide corrections data and integrity data to the WAAS receiver. The same satellite can also use the L1 frequency to provide a timing and ranging signal the same as a GPS provides. In effect, the GPS signal can be used as if it were another GPS satellite, high in the sky and can be used as part of the position solution. These satellites GPS signal are then corrected by the SBAS signal, like any other GPS satellite. There are probably circumstances where the geostationary satellite may be used as one of the best choices for determining a position. It is not clear if having more satellites in view will improve the accuracy than the minimum number of 4 for an X, Y, Z, t position. I expect the receiver chooses the best 4 based on geometry and residuals, all of which changes continuously as the satellites in view change positions.
The WAAS geo satellites are specially designed packages added to a regular geo communications satellite and integrated with the communications satellite prior to launch. They coexist on the same satellite that has C band and K band transponders used for communications.
