LPV vs LNAV/VNAV?

Andrew Sarangan wrote:

Sam Spade wrote:

paul kgyy wrote:


Both of these options require a WAAS receiver, I presume?


Yes, and if WAAS is not available to the standards required by the specs
then the 146 box will not accept the WAAS solution, which means (using
Garmin as an example) LPV, L/VNAV, and LNAV+V will not be available;
only LNAV will be available.


Something I never understood is why LNAV approaches don't automatically
show a glideslope so that the airplane arrives at the MDA at the VDP.


With the 146 spec you will often have an advisory glideslope to MDA.
That is the LNAV+V mode and will be provided if Jeppesen has coded that
capability into the approach's database string. As Garmin says in the W
handbood, not all LNAV-only IAPs have been so coded.

Sam Spade wrote:

Andrew Sarangan wrote:

Sam Spade wrote:

paul kgyy wrote:


Both of these options require a WAAS receiver, I presume?


Yes, and if WAAS is not available to the standards required by the specs
then the 146 box will not accept the WAAS solution, which means (using
Garmin as an example) LPV, L/VNAV, and LNAV+V will not be available;
only LNAV will be available.



Something I never understood is why LNAV approaches don't automatically
show a glideslope so that the airplane arrives at the MDA at the VDP.


With the 146 spec you will often have an advisory glideslope to MDA.
That is the LNAV+V mode and will be provided if Jeppesen has coded that
capability into the approach's database string. As Garmin says in the W
handbood, not all LNAV-only IAPs have been so coded.

I misstated that somewhat.

If I read it correctly (assuming WAAS is available and passes muster)
you will always get LNAV+V on an LNAV-only IAP, thus you will have
vertical guidance to MDA.

If, on the other hand, it is an LNAV/VNAV approach you will get L/VNAV
if Jeppesen has that approach so coded, otherwise you will get LNAV+V.
You'll have vertical guidance in both cases, but I presume you can only
use the DA concept and VNAV minimums if you get the L/VNAV annuciation.

"Sam Spade" wrote in message
...
Sam Spade wrote:
If I read it correctly (assuming WAAS is available and passes muster) you
will always get LNAV+V on an LNAV-only IAP, thus you will have vertical
guidance to MDA.


Can an RNAV approach have stepdown fixes on the final approach segment?

Stan Prevost wrote:

"Sam Spade" wrote in message
...

Sam Spade wrote:
If I read it correctly (assuming WAAS is available and passes muster) you
will always get LNAV+V on an LNAV-only IAP, thus you will have vertical
guidance to MDA.



Can an RNAV approach have stepdown fixes on the final approach segment?


Yes.

When VNAV first came in they could only be an an LNAV-only IAP. Then,
quite a few years ago that was changed to permit them for LNAV minimums
on an LNAV/VNAV IAP.

"Sam Spade" wrote in message
...
Stan Prevost wrote:


Can an RNAV approach have stepdown fixes on the final approach segment?


Yes.

When VNAV first came in they could only be an an LNAV-only IAP. Then,
quite a few years ago that was changed to permit them for LNAV minimums on
an LNAV/VNAV IAP.

An "advisory" guide slope could only be applied to a final approach segment
without stepdown fixes, or one in which the glide slope clears the
obstacle(s) by the required margin. I doubt that all LNAV-only approaches
have been TERPSed for that, especially those without VDPs.