The FAA changed the obstacle clearance assumptions about VNAV about two
years ago because WAAS wouldn't provide the vertical integrity they were
hoping for. If they hadn't tinkered with the VNAV criteria, VNAV DAs
would have usually been lower than LPV DAs. That is not their political
objective. ~

The new RNAV (RNP SAAAR) criteria overcomes this political issue by using
a very different methodolgy for VNAV surfaces. But, those IAPs will be
slow in coming along and will not be available for aircraft without Baro
VNAV.

The two RNAV (RNP) SAAAR IAPs for Palm Springs, CA (KPSP) were posted on
the FAA's IAP coordination web site yesterday. They will publish on
December 22nd.

wrote:

Take a look at the Mobile Alabama KMOB rnav Rwy 14, should be
available here

http://www.myairplane.com/databases/...s/00267R14.PDF

I notice that lnav/vnav minimums are 660 feet while lnav minimums are
620 feet. My question is, if someone has lnav/vnav authorization, why
wouldn't they prefer to do the lnav, using the glideslope as advisory,
and descend to an mda which is 40 feet below the decision altitude? I
understand the da allows a slight descent below it while initiating a
missed approach, but it still seems the lnav only approach would be
preferable.

Any gurus out there that can provide some input?

Any approaches around with an even greater disparity between lnav and
lnav/vnav minimums?

Stan