It is true that we get used to the air speed indicator and get a feel
for the glider. But I still would prefer an A of A indicator. Looking
back, when I was testing my glider, I wish I had an A of A indicator.
It would have made the initial tests to find the right flap settings
and corresponding airspeed faster and easier. Pilots generally do not
what to hang around for test, especially when a home built is nibbling
on there tail.
I knew where I needed to be with my flaps and airspeed, based on the
theoretical polars but making adjustment by adding or subtracting a
degree of flap deflection and making speed adjustments at the same
time you either need a good A of A indicator are a very patient pilot
partner. Hence It took many flights nearly 70 to 90 contest hours to
fine tuning the glider (I am not talking about handling the glider)
Once the parameters had been established there was very little need
for an
A of A. Still I would prefer one for changing ballast and when flying
in marginal conditions at a contest to have a glancing look at it the
odd time.

Udo


On Dec 8, 2:49 pm, Eric Greenwell wrote:
kirk.stant wrote:
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.

Does anyone know of documentation that supports the idea showing the
pilot the AOA will actually improve a glider pilot's thermalling? Or
even that the range of AOA needed to be "efficient" is too small for a
pilot to obtain it easily by using airspeed, or by just looking out the
canopy, once he's flown the glider enough to be familiar with it?

For example, I couldn't even find a mention of AOA in "Fundamentals of
Sailplane Design" when discussing thermalling. Circling efficiency is
discussed (page 63-65), but without mention of AOA, which suggests to me
that it's not the important factor. Climb performance, which is what we
really are after, is very dependent on the thermal shape (pages 65-66).
Circling at the best AOA doesn't give you the best rate of climb;
instead, the circling radius is the most important factor.

Look at the "rate of sink versus turn radius" table like the one on page
64 of "Fundamentals...". Does anyone know if the optimum is always at
the same AOA? And if not, what the range of AOA is for the table?

Regardless of the answer is to the question above, what would be useful
would be two additional tables "rate of sink versus turn radius". One
table would use an AOA greater (say, 3 degrees) than optimum; the other
table would use an AOA smaller by the same amount from optimum. This
would give us an idea of how sensitive circling efficiency is to AOA
errors.

If performance is not sensitive to the AOA, there is no need to look for
an indicator of it. A stall warning device would still be useful, but it
doesn't have to be based on AOA: it just needs to tell you when the wing
is getting close to a stall.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes"http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" atwww.motorglider.org