"Jeremy Lew" wrote in message
...
In my case, it was a CAVU day but extremely windy and quite turbulent. It
snip
was nice to be able to know I was nowhere near the stall by adding 25 to
my
GPS groundspeed.

I'm still not sold. Here's my thinking. You've got squirrely winds changing
direction and speed with altitude. So, at best you have to bracket that
GPS-derived airspeed by +/- 10kts just to be sure. If we're talking about
approach speeds this is quite a difference. So, broken record again, it's
not fundamentally useful since it can't be considered accurate for flying
the plane.

OTOH, here comes the broken record again, trimming for pitch attitude and
setting power for the chosen regime of flight *will* produce a known
airspeed. In my Skyhawk if you set one notch of flaps and 1900rpm and trim
for level flight, the speed will stabilize around 72kts. Pull 500rpm and
trim nose up one full turn and you'll descend at just about 500fpm at 72
kts. 2350 and level will always indicate 95-100kts. Climb is of course
whatever you can get with full throttle and 10deg nose up. This is the Law
of the Wing: it has ever been thus, and thus it ever shall be.

Also, if you fly the same plane regularly, or even just the same type, you
should be able to "feel" the airspeed reasonably well without any
instruments at all. Obviously this is easier in a pussycat like a 172
compared to a Mooney or Bo, but its still possible. Most pilots today just
don't get enough practice in slow flight because our instinct has become to
avoid it. Instrument pilots get a double whammy because we tend to focus our
proficiency activities on IFR skills, which expressly avoid true slow-flight
for good reason, but this compounds the problem. Of course, I'm speaking
about myself here as well, but all this is the way my CFII trained me, and I
try to live up to it.

Best,
-cwk.