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Same here, but I didn't feel like saying anything...

Somehow I missed this post before, looks like this was going to be a complete explanation for how the LNAV/VNAV DA could end up lower, and even includes some diagrams from the current RNAV approach TERPS order .58B. I really wonder what the rest of this paragraph was going to say? Either way...

Downloading it now - thanks. Yeah, I thought the .50 might be way obsolete...

I've been digging through a number of internet sources, including Order 8260.50 (FAA's LPV Approach Procedure Construction Criteria, but might be superseded as it is from 2002) and I think I see another, simpler way the algorithm for determining the LPV and LNAV/VNAV DAs might generate a lower...

The steeper climb gradient on the missed is, of course, to be expected since the RNAV Z gets you so much lower and closer in. And the chart note, I guess, also explains why they created the RNAV Y with its higher minimums, to establish an approach that aircraft incapable of such a steep climb...

Very interesting. Two RNAV approaches along the exact same approach course with the same glide path and TCH, but with vastly different minimums. How can the algorithm to determine the vertically guided DAs and the non-precision MDAs through analysis of obstructions along the final approach path...

Thanks. Now, does anyone know why the LNAV/VNAV DA is significantly lower than the LPV DA on the RNAV 16 X at KRNO? Inquiring minds and all... ;)

In the case of the RNAV 16L X at KRNO (in the thread linked to by @RussR), I think it's more than an academic exercise: if I was flying that approach and the ceiling was right in the 700 to 800 ft. range, I'd definitely want to know whether I can safely descend to the lower LNAV/VNAV DA using...

Thanks @RussR . Still seems somewhat mysterious. One thing I note in this case, though, is that the difference is only 12 feet and thus makes no practical difference in how I'd fly the approach. The difference in the case in the other thread is more significant, roughly 50 feet. So the question...

Now I'm not so sure. This article from IFR magazine discusses the differences between the LNAV OCS and the LNAV/VNAV OCS and the different ways that the MDA and DA are determined. Apparently the LNAV/VNAV OCS has a flat part inside the DA. The LPV OCS is a sloping surface that is offset from the...

On an approach with both LPV and LNAV/VNAV sets of minimums, why might the LNAV/VNAV DA be lower than the LPV DA? Ron says he is aware of such an approach, but I have no more details. I know there are cases where the LNAV MDA can be lower than the corresponding APV DA, because the obstacle...

This makes perfect sense, thank you again.

Thank you. I believe this settles the question. Given (as you confirmed) that the path is the same for LPV and LNAV/VNAV under WAAS, there is no basis in safety for any more restrictive interpretation. Just as an aside, I'm curious that this TSO seems to allow the GPS to downgrade the...

Since you have mentioned the name, I will simply confirm your assumption. :) Thank you, that answers my question as regards safety... ... and this confirms my understanding of the relationship between the two glidepaths. Identical angles, tighter guidance on the LPV. It seems the only...

I know - but it is still something that could make the difference between getting in and not. And I'm interested in the principle here as well - there seems to be a rash of such new NOTAMs in the area lately, and with some of these approaches LPV may confer a greater advantage. And tbh...

So you cannot follow the LPV GS to the LNAV/VNAV DA? Why not?

Well now, again, that's what I'm not sure of. I *thought* the two glidepaths had the same angle but different vertical thicknesses - the L/V being thicker and thus less precise. But I'm not certain of that.

So far the answers all echo my own thinking about this... but I have a very firm answer to the contrary from someone who claims to be very confident (a respected CFII, whom I won't name because he no longer posts here), and who discussed this with Garmin earlier today and came away even more...

Title says it all. The approach in question is the RNAV 17 at KMPV. The approach has an LPV DA, an LNAV/VNAV DA that is about 100 feet higher, and an LNAV MDA that is higher still. The LPV DA is NA by NOTAM due to trees close to the airport perimeter, evidently affecting clearance on the missed...

So is Vermont. I'm over 65, but do not expect to get my first shot until MAYBE April.