Step Down or Track Glide slope on GPS overlay approach

Sometimes step-downs are to clear obstacles. I haven't tried the 430W
yet, but how does the "stabilized approach" deal with this? Is there
a variable glideslope?

On 14 Apr 2007 08:16:05 -0700, "paul kgyy" wrote:

Sometimes step-downs are to clear obstacles. I haven't tried the 430W
yet, but how does the "stabilized approach" deal with this? Is there
a variable glideslope?

The GP angle can vary by approach. Not all LNAV approaches will have
advisory vertical guidance.
Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

Mooney wrote:

I have just recently acquired a Garmin 430/WAAS for my Mooney 201. In
practicing approaches to familiarize myself with the unit, I went up
with an instructor to get some advice/tips. I had flown a GPS overlay
approach (NDB/GPS Runway 5 KLWM, Lawrence MA) previously in VFR
conditions and tracked the vertical guidance provided by the GPS and
loved it ... very stable approach and no need to dive/level/dive etc.

Then I went up with the instructor and did what I thought was a great
approach (also NDP/GPS 5 KLWM) and he was upset I didn't fly it more
like the "original" non-precision approach by identifying fixes with
cross radials and doing the stepdowns.

So that is the question. Which technique should be used and why? If I
give up the "track the GPS glideslope" approach I feel I'm giving up
the advantage of a very stable/controlled approach configuration and
not sure what I'm gaining in return.

Comments from the experts??

Final questions: With the WAAS GPS on this approach, can I descend to
the lower minimum based on identifying the final stepdown fix if I am
just flying the GPS's vertical guidance? Where are the answers to
these questions provided?

Your instructor's logic is probably the argument that if you descend to
the next stepdown minimum quickly, say 1000 ft/min, you have a better
chance of getting under the clouds sooner than if you go down the glide
slope. The other danger is that using the LNAV+V glide slope can lure
you into such a steady approach that you forget to level off at the MDA
and continue in level flight until the MAP. You cannot stay on the
glideslope below MDA unless you have landing aids in sight.

In article ,
BillJ wrote:

Mooney wrote:

I have just recently acquired a Garmin 430/WAAS for my Mooney 201. In
practicing approaches to familiarize myself with the unit, I went up
with an instructor to get some advice/tips. I had flown a GPS overlay
approach (NDB/GPS Runway 5 KLWM, Lawrence MA) previously in VFR
conditions and tracked the vertical guidance provided by the GPS and
loved it ... very stable approach and no need to dive/level/dive etc.

Then I went up with the instructor and did what I thought was a great
approach (also NDP/GPS 5 KLWM) and he was upset I didn't fly it more
like the "original" non-precision approach by identifying fixes with
cross radials and doing the stepdowns.

So that is the question. Which technique should be used and why? If I
give up the "track the GPS glideslope" approach I feel I'm giving up
the advantage of a very stable/controlled approach configuration and
not sure what I'm gaining in return.

Comments from the experts??

Final questions: With the WAAS GPS on this approach, can I descend to
the lower minimum based on identifying the final stepdown fix if I am
just flying the GPS's vertical guidance? Where are the answers to
these questions provided?

Your instructor's logic is probably the argument that if you descend to
the next stepdown minimum quickly, say 1000 ft/min, you have a better
chance of getting under the clouds sooner than if you go down the glide
slope. The other danger is that using the LNAV+V glide slope can lure
you into such a steady approach that you forget to level off at the MDA
and continue in level flight until the MAP. You cannot stay on the
glideslope below MDA unless you have landing aids in sight.

More likely, his instructor just isn't up to speed on the new equipment and
doesn't understand that there are better ways to do things than the way he
learned during his instrument training. Other than wanting to bust some
student's balls during training, I can't imagine any reason anybody would
ever want to fly a series of stepdowns if a glideslope is available.

On 13 Apr 2007 19:26:50 -0700, "Mooney" wrote:

I have just recently acquired a Garmin 430/WAAS for my Mooney 201. In
practicing approaches to familiarize myself with the unit, I went up
with an instructor to get some advice/tips. I had flown a GPS overlay
approach (NDB/GPS Runway 5 KLWM, Lawrence MA) previously in VFR
conditions and tracked the vertical guidance provided by the GPS and
loved it ... very stable approach and no need to dive/level/dive etc.

Then I went up with the instructor and did what I thought was a great
approach (also NDP/GPS 5 KLWM) and he was upset I didn't fly it more
like the "original" non-precision approach by identifying fixes with
cross radials and doing the stepdowns.

So that is the question. Which technique should be used and why? If I
give up the "track the GPS glideslope" approach I feel I'm giving up
the advantage of a very stable/controlled approach configuration and
not sure what I'm gaining in return.

Use the stabilized approach because, as you have discovered, it is easier
to fly! Aren't ILS's easier to fly than dive & drive non-precision
approaches? Just don't forget to level off at the MDA. "You" cannot treat
MDA as a DA without special authorization.

Comments from the experts??

Final questions: With the WAAS GPS on this approach, can I descend to
the lower minimum based on identifying the final stepdown fix if I am
just flying the GPS's vertical guidance?

The requirement to identify KRIED is not dependent on how you are flying
the approach. However, if KRIED is in your DB, you can use the GPS to
identify it.

Where are the answers to these questions provided?

Which question?

The issue of stabilized versus D&D approaches is discussed in airline
safety material.

Rules for flying approaches are in the FAR's and AIM.

Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

I think what we are saying is that even though Jeppesen says the VNAV
GS ensures being above the step-down fixes and GARMIN wrote approved
software to make sure the GS needle properly indicates the Jeppesen-
provided vertical guidance, the pilot needs to explicitly note whether
the step-down fixes have been passed and not follow the GS unless it
is consistent with these restrictions. So, it is ok to fly the
glideslope, but you must perform these checks as the approach
progresses.

Seems like a good double check yet lets me keep the stablized
approach. The other issues of MDA vs DA and the possible advantage of
entering VFR earlier if you dive & drive are noted. Thanks to everyone
who responded.

Mooney wrote:
I think what we are saying is that even though Jeppesen says the VNAV
GS ensures being above the step-down fixes and GARMIN wrote approved
software to make sure the GS needle properly indicates the Jeppesen-
provided vertical guidance, the pilot needs to explicitly note whether
the step-down fixes have been passed and not follow the GS unless it
is consistent with these restrictions. So, it is ok to fly the
glideslope, but you must perform these checks as the approach
progresses.

Seems like a good double check yet lets me keep the stablized
approach. The other issues of MDA vs DA and the possible advantage of
entering VFR earlier if you dive & drive are noted. Thanks to everyone
who responded.

Google for "constant angle non-precision approach" for lots of
discussion about the pros and cons.

Dave

Stable controlled descent approaches are both easier and safer than
stepdown approaches, which was what the airlines found. There is no
reason to expect different from light airplanes.

I would find an instructor more amenable to new technologies.

Mooney wrote:
I have just recently acquired a Garmin 430/WAAS for my Mooney 201. In
practicing approaches to familiarize myself with the unit, I went up
with an instructor to get some advice/tips. I had flown a GPS overlay
approach (NDB/GPS Runway 5 KLWM, Lawrence MA) previously in VFR
conditions and tracked the vertical guidance provided by the GPS and
loved it ... very stable approach and no need to dive/level/dive etc.

Then I went up with the instructor and did what I thought was a great
approach (also NDP/GPS 5 KLWM) and he was upset I didn't fly it more
like the "original" non-precision approach by identifying fixes with
cross radials and doing the stepdowns.

So that is the question. Which technique should be used and why? If I
give up the "track the GPS glideslope" approach I feel I'm giving up
the advantage of a very stable/controlled approach configuration and
not sure what I'm gaining in return.

Comments from the experts??

Final questions: With the WAAS GPS on this approach, can I descend to
the lower minimum based on identifying the final stepdown fix if I am
just flying the GPS's vertical guidance? Where are the answers to
these questions provided?