"kirk.stant" wrote in message
...
On Dec 8, 4:29 am, John Galloway wrote:
Kirk,

I agree with your assessment. A simple LED index system of three lights.
One indicating "fast", another "on speed" (Max Cl) and finally one that
flashes when nearing stall. Sound familiar from your F-4 days?

Wayne
Retired A-6 Bombardier.
http://www.soaridaho.com/Schreder

John,

I tried this technique on an LS4. While you could see the difference
in angle of attack quite clearly, there was a huge difference when any
yaw was introduced, with the yarns showing significant differences in
relative airflow on opposite sides of the canopy. In effect, with
this system, you are really showing the instantaneous airflow over the
canopy, and deriving AOA from that indication - which is not much
better than just using airspeed, really, and effectively impossible to
use due to yaw effects and the flapping of the yarn masking the small
AOA changes you are interested in.

Having some time in airplanes that used AOA (gauge, lights, and
variable audio cues) in preference to airspeed during low speed flight
(F-4s, in my case) I can vouch that it's a much better way to fly -
especially when the AOA is coupled with an audio signal. But in a
glider, I thing the working AOA range that we are interested in is a
lot smaller than the AOA range that low aspect ratio jets use, so in
practice it may be more difficult to implement.

What I would like to see is a simple AOA indicator that would tell me
when I am at the optimum AOA for efficient thermalling. No fancy
indicator, just a bright LED that would be on steady at thermalling
AOA. Have it start flashing when approaching the desired AOA, and
have a different flash rate when below the desired AOA (which would
also function as a stall warning, since there is really no reason for
ever flying below min sink, especially in the pattern.

To use, pull into the thermal and set your attitude to the approximate
AOA, glance at the LED to adjust to the exact AOA, then fly that,
occasionally crosschecking the light. No figuring for bank angle or
ballast required, the wing takes care of that. Sweet...

AOA is really not that useful in cruise, since we are really more
concerned with the appropriate MC speed, and rarely fly at L/D max.
But again, that would be a single AOA point to measure, and could use
a different color LED.

Obviously, with a flapped ship, flap position would have to be sensed
and compensated for.

Since I'm really only concerned about one angle of attack, a moving
vane should not be necessary - I think it can be done with
differential pressure ports, so no moving parts or drag. Flaps may
complicate things, but even if there has to be a different set of
ports for each thermalling flap position, it may still be easier than
a mechanical AOA vane. Or just pick your favorite flap setting, and
TLAR it from there...

Comments from smarter people out there are welcome!

Kirk
LS6b "66"