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.