There's nothing wrong with your reasoning in general, but it *was* your
original assertion that the groundspeed is "useless for flying the plane."
Again, in my case, I had no ASI, VSI or altimeter to work with, so how am I
supposed to trim to hold a 500fpm descent? What if the pitch indication
was slightly off? I set it up by sight and feel as best I could and used
the groundspeed as a crosscheck, which I maintain was useful for flying the
plane. You're right about takeoff, I don't see the value there.

BTW, I'm only 3 months less green than you chronologically, and probably
greener in flight-hours


Jeremy
"Colin W Kingsbury" wrote in message
nk.net...

"Jeremy Lew" wrote in message
...
Colin, you adopt quite the air of authority for someone who has had their
ASEL for less than 2.5 years. In this case I wanted to come in at about
80kts and one notch because of the wind shear, which is not a normal
approach speed or flap configuration for me. Are you telling me you have
memorized every permutation of pitch/power/flaps/airspeed for all
possible
gust conditions on approach?

Depending on how and what you fly, 1 notch and 80 kts sounds awfully close
to approach configuration in either level flight or descending on the ILS.
Some people fly a little slower, others a little faster, but it's in the
ballpark. If you told me to climb at 100FPM and 90 knots, no, I have no
idea
what the setting for that is off the top of my head. But that's not the
situation.

If my normal approach speed is 65 knots, and I want to fly 75 for gusty
conditions, I'm not using the GPS groundspeed to do it. It's too coarse a
measure to be used with real precision. I'm setting up for an ILS-type
configuration which normally settles right in at 72 knots, and adding
another 50-100rpm and trim to hold the descent rate around 500rpm. I bet
that'll get me pretty darn close, at least on the right side of things. I
contend that you're better off setting pre-determined power/pitch settings
and understanding control feel than looking at the GPS groundspeed
expecting
to learn too much from it.

This all got started because someone who sounded even greener than me said
they were going to keep an eye on their GPS groundspeed during takeoff,
and
it didn't strike me as such a great idea, for all the reasons I've laid
out.
A reasonable (i.e. can be formed in one good lesson) understanding of
pitch/power settings will allow you to fly the plane safely all day long
without an ASI, in any kind of conditions. I don't think this is
particularly controversial and it's the way I was taught when I got my
private, instrument, and seaplane ratings.

Of course we all use everything available to us to form the most complete
picture possible, and GPS groundspeed can be included in that, so long as
we
account for its limitations. It can tell you magnitude of change (i.e. a
change in groundspeed of 10kts at constant power/pitch means the wind has
changed 10kts) for instance and that is useful. More importantly, it can
tell us how much longer we have to go before we can empty our tanks, or
fill
our plane's.

Forget my authority or lack thereof. What is wrong with my reasoning here?

best,
-cwk.