For a while, LNAV procedures with a stepdown were not allowed to be
combined with a LNAV/VNAV. If you wanted a stepdown to get lower LNAV
MDA, you had to create a separate procedure. That rule has since been
rescinded, so you'll see future combined LNAV/VNAV and LNAV with a
stepdown if appropriate. In the meantime, the "X" and "Y" procedures
will remain as they are until amended, but amending them is not a priority.

JPH

Stan Prevost wrote:
"Roy Smith" wrote in message
...


Our local "big" airport has four ILS's to 200 ft DH, and various VOR, GPS,
and NDB approaches. There are four new RNAV(GPS) approaches: for each
runway (36L and 36R), there are two of these approaches (Y and Z). In each
case, Z has LNAV and LNAV/VNAV minima, and Y has LNAV only. The Y and Z
approaches have the same IAFs, IF, FAFs, and MAPs. The Z LNAV MDA is 545
ATDZE, the Z LNAV/VNAV MDA is 325 ATDZE, a 220 ft advantage. But on the Y
approach, the LNAV MDA is 325 ATDZE. The only difference between the
approaches is that Y has a stepdown fix after the FAF, which is apparently
avoided by VNAV. Heck, with a 325 ft ATDZE MDA with LNAV alone, I sure
don't need VNAV, if it just gets me to the same DA. And 325 is pretty darn
good.

It's curious to me that two approach plates were published for Y & Z, rather
then combining them and noting the stepdown fix as applicable to LNAV only.
Maybe it made for too much chart clutter.

I hope we get the corresponding approaches for 18L and 18R.