GPS approaches with VNAV vertical guidance

In article ,
Dave Butler wrote:

Roy Smith wrote:
wrote:

Once it works, I believe your advantage with be with LPV minimums more than
VNAV/LNAV minimums.


The plate shows a catagory of "GLS PA DA", which I decode as "GPS
Landing System, Precision Approach, Decision Altitude" (with minimums
shown as NA). Is that the same as the LPV you're talking about?

Take a look at RNAV(GPS) RWY 36 at OSH for an example of an approach with
different LPV, VNAV, and LNAV minima.

Dave

Hmm, not so much difference as I would have thought. The LPV only gets
you another 40 feet and 1/4 mile. Better than nothing, I guess, but
still not an earth-shattering improvement.

Is the idea that the synthetic GS for the LPV will be 3 degrees like a
real GS, or will they be all sorts of different angles? I pretty much
know what power settings I need to track a 3 degree GS, and it would be
a shame if I couldn't leverage that knowledge on the LPV.

Thanks.

"J Haggerty" wrote in message
news:fjBhd.93062$tU4.67667@okepread06...
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rescinded, so you'll see future combined LNAV/VNAV and LNAV with a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.

Roy Smith wrote:

wrote:
Once it works, I believe your advantage with be with LPV minimums more than
VNAV/LNAV minimums.

The plate shows a catagory of "GLS PA DA", which I decode as "GPS
Landing System, Precision Approach, Decision Altitude" (with minimums
shown as NA). Is that the same as the LPV you're talking about?

No. GLS is on hold. It would be equivalent to ILS. LPV is close to ILS, but
not quite there. Here is the info in the current AIM (1-1-20):

"2. A new type of APV approach procedure, in addition to LNAV/VNAV, is being
implemented to take advantage of the lateral precision provided by WAAS. This
lateral precision, combined with an electronic glidepath allows the use of TERPS
approach criteria very similar to that used for present precision approaches,
with adjustments for the larger vertical containment limit. The resulting
approach procedure minima, titled LPV, may have decision altitudes as low as 250
feet height above touchdown with visibility minimums as low as 1/2 mile, when the
terrain and airport infrastructure support the lowest minima. LPV will be
published on the RNAV (GPS) approach charts (see paragraph 5-4-5, Instrument
Approach Procedure Charts)."

Another issue is that right now only airlines can really make use of this
stuff anyway, since relatively few people are flying behind v2 GNS-480s.
This is why Jane Garvey said in her AOPA speech that it's important for
pilots to go out and get new equipment that can make use of this. Of course,
I'd like to see her agency help by making it easier to certify and install
such equipment. There's no reason it should cost $15,000 to do so.



Jane Garvey? ;-)

The airlines are NOT making use of WAAS. They have basically told the FAA to
take WAAS and shove it. Almost no airline aircraft have WAAS. In fact, all the
aircraft produced prior to the early 1990s don't even have GPS unless they have
been upgraded (a very expensive upgrade for that type of aircraft certification
process).

The airlines are in the financial fight of their corporate lives. They couldn't
care less about WAAS and LPV.

"Barry" wrote in message ...
The plate shows a catagory of "GLS PA DA", which I decode as "GPS
Landing System, Precision Approach, Decision Altitude" (with minimums
shown as NA). Is that the same as the LPV you're talking about?

GLS does stand for "GPS Landing System," and would provide capability
equivalent to CAT I ILS (200 ft decision height/altitude). WAAS was
originally supposed to provide this, but due to integrity issues is only good
down to 250 ft, which is the limit for LPV approaches. Current plans for WAAS
upgrades include better coverage and redundancy, but not GLS. There are
tentative plans to modernize GPS and add a new civil frequency; if this is
done, then WAAS might provide GLS at some time after 2013.

Just a nitpick:

GLS actually stands for "GNSS Landing System." The intention is have
the term encompass any satellite navigation system, of which "GPS"
(the U.S. based system) is (currently the only certified operational)
one.

It can eventually apply to the European, Japanese, Indian, etc.,
systems if/when those systems support it.

wrote in message ...


The airlines are NOT making use of WAAS. They have basically told the FAA
to
take WAAS and shove it. Almost no airline aircraft have WAAS. In fact,
all the
aircraft produced prior to the early 1990s don't even have GPS unless they
have
been upgraded (a very expensive upgrade for that type of aircraft
certification
process).


No, but they do use LNAV/VNAV with FMS-derived VNAV. Northwest and a few
others got approval for this a few years back IIRC and that's why those new
descent profiles started popping up on Jepp plates. It's also why the new
approaches are all called RNAV and not GPS.

-cwk.

C Kingsbury wrote:

wrote in message ...


The airlines are NOT making use of WAAS. They have basically told the FAA
to
take WAAS and shove it. Almost no airline aircraft have WAAS. In fact,
all the
aircraft produced prior to the early 1990s don't even have GPS unless they
have
been upgraded (a very expensive upgrade for that type of aircraft
certification
process).


No, but they do use LNAV/VNAV with FMS-derived VNAV. Northwest and a few
others got approval for this a few years back IIRC and that's why those new
descent profiles started popping up on Jepp plates. It's also why the new
approaches are all called RNAV and not GPS.

No doubt about it. Most of them use their GPS-equipped aircraft for LNAV/VNAV
as an ILS backup at major airports and as primary IAPs at a few airports. But,
that has everything to do with GPS and nothing to do with WAAS.

wrote:



Another issue is that right now only airlines can really make use of this
stuff anyway, since relatively few people are flying behind v2 GNS-480s.
This is why Jane Garvey said in her AOPA speech that it's important for
pilots to go out and get new equipment that can make use of this. Of course,
I'd like to see her agency help by making it easier to certify and install
such equipment. There's no reason it should cost $15,000 to do so.




Jane Garvey? ;-)

The airlines are NOT making use of WAAS. They have basically told the FAA to
take WAAS and shove it. Almost no airline aircraft have WAAS. In fact, all the
aircraft produced prior to the early 1990s don't even have GPS unless they have
been upgraded (a very expensive upgrade for that type of aircraft certification
process).

True, they want LAAS at just the airports that they use.


Matt

Matt Whiting wrote:



True, they want LAAS at just the airports that they use.

Correct, LAAS, not WAAS.