From here
As Timothy has pointed out (I think), we couldn’t care less. We can all have ersatz LPV for the price of a GTN650, so the CAA desk-weenies can go back to counting paperclips, or whatever they do to avoid making decisions.
Incidentally, are there any AIP runways for which the GTN visual approach guidance is not suitable?
Garmin includes self evidently unsafe approaches, such as Oban 19, which is why they should be treated with great caution.
(I should add that approaches which are unsafe for a 3° glidepath offer no vertical guidance. There is even an approach to Courcheval 04).
Yes, those are good examples.
Courchevel 04 is a tricky approach, even for a Maule 
But if we hack the Oban 19 VAG by adding a WPT just offshore of the caravan park, I think the GTN trainer may fly down to the threshold without bumping into the hill – most of the time…
Incidentally, there’s a fly-in at Oban on Sunday.
There is a very interesting post here which nobody picked up on, and which I can’t verify because I don’t have a GTN.
A thread specific to the +V feature (which is present on Avidyne IFD also) and whether it always clears stepdown fixes, is here although that feature is available only where an official IAP is published.
I should add that approaches which are unsafe for a 3° glidepath offer no vertical guidance
Is the “no” correct?
Yes.
On the other point, there appears to be a confusion between the +V feature, the VCALC feature, the Visual Approach feature and the fundamentals of an OBS based CDFA.
Firstly, the feature being discussed here, the Visual approach, normally has a glidepath indication and, to all intents and purposes, looks like and flies like an LPV/ILS. It always has a 3° slope and, when Garmin determines that that would not be terrain and obstacle safe, the glidepath is removed an then it behaves like an LNAV (or, rather, an LP) approach.
The +V feature is added to a published LNAV Final Segment (and nowhere else) and provides an LPV-like glidepath is a straight line between FAF and MAP. It is angle based and will be at whatever angle is required (eg 3.5° at EGBJ).
The VCALC feature simply tells you what RoD is required to get, along the FPL track, from an FPL waypoint to desination. The RoD required does indeed change with groundspeed and therefore needs to be monitored. I am not aware of any way to get the VCALC output to drive the glidepath indicator, though it would be neat. It is a great feature for planning descent from crusing altitude, but I have never thought of using it for the Final Approach segment of an OBS cloudbreak; for that I would use CDFA against range to the threshold every time.
OK; that’s a very useful clarification.
It sounds like the VCALC is what you get on all the Garmin handhelds i.e. you load a DCT to xxxx and it tells you the required VS. I would have never thought of that feature as being any good for DIY approaches. It is good for doing long continuous descents. I guess Valerio, having got the GTN750 installed in his RV7 (the link I posted in #5) was not aware of the “Visual approach” feature. He is long gone (email gone dead etc).
Yes, VCALC is simply automated assistance for the “time to run” calculations we all used to do back in the day.
It gets switched off in OBS mode, so you couldn’t use it in an OBS approach, though you could if you programmed in an FAF before the destination.
The Visual Approach feature is a relatively recent addition, indeed is not yet technically available on EASA reg aircraft, so Valerio, like the rest of us, would not have been aware of it in 2016.
Which of these functions calculates the glide path, if at all, to the respective runway threshold ? VCALC takes the airport reference point, which in IMC would bring you either over mid runway ir worse, over a hangar or taxiway. I use it to request /start descending. I’m not sure I’m into the this DIY IR approaches thing. If there’s a wind energy mast or a crane or whatever, you end up like a fly on the windshield, no ?
In fact there was a twin flying into Mainz which didn’t make the trees, and a Mooney crashing into the taxiway two years ago i’m Zweibrücken, both are suspected to have been self assembled “IFR” approaches; at least looked like it
