LNAV, VNAV and LPV

You have to contact a Garmin dealer and get your 430 on the list for the
WAAS upgrade. The price is $1500 plus extra for antenna and maybe coax
replacement, and shipping. It is a major upgrade to the unit, which then
becomes the 430W. I have heard that it replaces almost everything inside
the box except the front panel and display. The manual and simulator are
available on the Garmin website.

LNAV/VNAV can be accomplished with certified barometric VNAV installations,
or with WAAS-derived vertical navigation. I think the requirement for WAAS
on the lateral component of navigation is due to the lower minima and thus
higher required lateral accuracy. The lower you are going, the closer to
the runway you want to be.




"Andrew Sarangan" wrote in message
ups.com...
Is there a formal discussion of these various approach minimums? I
looked through all the obvious places (AIM, GPS manuals, AOPA
articles), but I haven't found a comprehensive discussion of these.

Example:
My understanding of LNAV/VNAV is that it has a barometrically generated
glideslope. That would mean that any GPS with LNAV functionality should
be able to generate a glideslope if it has an appropriate altimeter
functionality. However, LNAV/VNAV is only discussed in the context of
WAAS (AIM 5-4-5(e)) . If the glideslope is purely barometric, why does
one need WAAS for LNAV/VNAV?

Only a few places spell out what LPV is, but I finally figured out that
it stands for Localizer Precision Vertical Navigation. Perhaps LPVNAV
might have been a better acronym. In any case, I am assuming that the
altitude in LPV is generated from WAAS, hence it is not prone to
altimeter errors.

Finally, if I have the GNS-430, what options do I have to enable these
features? Does the installation need to be recertified, or is it simply
a firmware upgrade?

Any explanations or pointers to other articles would be appreciated.