"Bullwinkle" wrote in message
...
On 7/9/06 11:27 AM, in article
,
"Bill Daniels" bildan@comcast-dot-net wrote:


"Don Johnstone" wrote in message
...
At 06:42 08 July 2006, G L I D E R S T U D wrote:

Yaw sting....if you cant feel your body sliding left
or right when your
uncoordinated, you should probably relax some, because
you are way too
uptight. But then again one of my coaches said I was
too relaxed. On
that note my Discus 2ax didn't have a yaw sting, and
my Nimbus 3
doesn't have one either, and I probably won't get it
'fixed' before the
Opens. I fly in the mountains and I don't feel that
it is hazardous.
Plus that sting is way too much drag.

I defy anyone to 'feel' the tiny amount of yaw that
a yaw string will indicate. The drag created by even
the largest piece of wool will be very small compared
to even a small amout of yaw in straight and level
flight. A 'T&S' ball is just not sensitive enough and
the yaw string has the advantage of being in your eye
line, you don't have to go heads down to see it. To
fly efficiently in a big winged glider is is even more
essential as even tiny amoutns of control differences
are magnified with the addition leverage of long wings.


To Don Johnstone - Yep!

The weather is doing something it hasn't done in quite a while -
raining -
therefore, I'm spending the weekend indoors. This has led me to research
a
few ideas that I had set aside. One of them is an angle of attack
indicator
for gliders.

Any reading of accident reports will quickly lead one to the conclusion
that
pilots don't pay enough attention to AOA. No matter how hard AOA is
hammered into a students brain, a few months after their checkride, they
just watch the ASI. Some of them are involved in stall/spin accidents.

AOA indicators have long been essential to the safe operation of large
aircraft so, now that electronics are cheap, why not gliders too?
Gliders
spend a lot of time flying near the stall AOA so we shoud be especially
interested in an AOA indicator.

So, how do we measure AOA? The traditional nose boom pitch vane is too
fragile for gliders but there is another way to get AOA data. Companies
like Masi make a simple AOA probes. See:
http://www.cgmasi.com/aviation/index.html

The Masi probe computes AOA from the pressure difference between two
pressure ports at 45 degrees to the airflow. Could the same be done with
pressure ports located on upper and lower nose? I think so. An
inexpensive
differential pressure sensor and a bit of electronics driving an LED
lightbar plus a calibration proceedure would do it.

The calilbration procedure would be simple since we are only interested
in
three AOA's - Stall, Minimum sink, and Best L/D. These would be very
helpful when flying gliders with a wide range of wing loadings. The min
sink AOA would be particularly helpful when flying at steep bank angles.

Gliders with flaps would have to repeat the calibration procedure for
each
flap setting of interest - those being approach flaps and thermalling
flaps.
Flap setting would have to be sent to the AOA conputer.

Any gadgeteers out there interested in making a few bucks awhile maybe
saving a few lives?

Bill Daniels


Bill,

Two or three pilots at Black Forest have very inexpensive AOA indicators
installed. They have yawstrings taped to the canopy way down the sides,
adjacent to their thighs, basically at the junction of the canopy and the
frame.

They then make marks with grease pencil at the crucial airspeeds, and
report
being happy as clams with it.

Haven't tried it myself. YMMV.

Bullwinkle


I've done that going back several years. It works fine but those darn
strings keep getting caught under the canopy frame when you close it and
some gliders don't have canopies that allow proper placement of the strings.
Also, it only works at a zero slip angle. An electronic AOA system shouldn't
cost much but, of course, it'll cost more than strings.

bildan