GPS approaches with VNAV vertical guidance

With all the talk about the GNS80 and the Garmin 430 having VNAV and
LAAS capability, I would like to know something. Are there any actual
approaches in use that one can fly, today, that use these features? Do
you get vertical guidance from GPS derived altitude or is it vertical
guidance from altimeter derived altitude? Where are these approaches?

In article ,
(Doug) wrote:

With all the talk about the GNS80 and the Garmin 430 having VNAV and
LAAS capability, I would like to know something. Are there any actual
approaches in use that one can fly, today, that use these features? Do
you get vertical guidance from GPS derived altitude or is it vertical
guidance from altimeter derived altitude? Where are these approaches?

The GPS-16 at HPN has both LNAV and LNAV/VNAV minimums published. LNAV
alone gets you 600 & 1, VNAV gets you another 120 feet lower.

What's a little silly is that there's also an ILS-16 which gets you the
standard 200 & 1/2, so except as a contingency against the ILS being
OTS, having the LNAV/VNAV approach doesn't buy you anything. The big
payoff is still in the future, when the FAA starts publishing LNAV/VNAV
approaches to runway ends (and airports) which aren't already served by
ILS or other ground-based approaches.

I havn't actually flown a VNAV approach yet. When we get our CNX-80's
upgraded to the new software (RSN), I'll be able to try it out.

Roy Smith wrote:

In article ,
(Doug) wrote:

With all the talk about the GNS80 and the Garmin 430 having VNAV and
LAAS capability, I would like to know something. Are there any actual
approaches in use that one can fly, today, that use these features? Do
you get vertical guidance from GPS derived altitude or is it vertical
guidance from altimeter derived altitude? Where are these approaches?

The GPS-16 at HPN has both LNAV and LNAV/VNAV minimums published. LNAV
alone gets you 600 & 1, VNAV gets you another 120 feet lower.

What's a little silly is that there's also an ILS-16 which gets you the
standard 200 & 1/2, so except as a contingency against the ILS being
OTS, having the LNAV/VNAV approach doesn't buy you anything. The big
payoff is still in the future, when the FAA starts publishing LNAV/VNAV
approaches to runway ends (and airports) which aren't already served by
ILS or other ground-based approaches.

I havn't actually flown a VNAV approach yet. When we get our CNX-80's
upgraded to the new software (RSN), I'll be able to try it out.

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

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?

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

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.

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.

"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.

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)."

"Roy Smith" wrote in message
...

What's a little silly is that there's also an ILS-16 which gets you the
standard 200 & 1/2, so except as a contingency against the ILS being
OTS, having the LNAV/VNAV approach doesn't buy you anything.

There's significant labor involved in charting a new approach- obstacle
analysis, airspace planning, test-flying, etc. My guess is that where there
is an ILS already, creating an LNAV/VNAV approach is relatively low-cost
since you can piggyback on most of the existing labor.

Likewise, I suspect most of the new approaches we'll see over the next year
or two will be added to fields already equipped with an ILS. Lots of fields
here in the Northeast have an ILS but only on one runway end. I suspect in
five years or so every airport with air carrier traffic will have a
precision approach to every runway end. Somewhere along the way, we'll start
to see a trickle of these come to fields that currently have published
approaches but no ILS.

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.

-cwk.