Leading Turns with Rudder - Revisited

On Tue, 12 Aug 2008 20:09:25 GMT, Eric Greenwell
wrote:

bagmaker wrote:
-
I don't have the full context from the quote above, and while I am
normally loathe to contradict Langewiesche, I must report I have
successfully produced turns with just the rudder in gliders. Give it a

try, and you will find you can produce an adequate turn, because the
yawing causes the dihedral to bank the glider in the desired direction.


I suggest you give it a try at or near the stall...

I've not done it myself, but I've read about how attempting a
coordinated turn at or near stall can cause an "over the top" spin entry
when the out-of-turn aileron is deflected downward and stalls the outer
wing tip. In any case, my experience (and the text books) indicates that
an attempt to turn at or near a stall risks entering into a spin, even
with "proper" use of the controls. The pilot should speed up before
attempting the turn, coordinated or not.

This reminds me of another frequently repeated statement: "you won't
spin if you keep the yaw string centered." Besides my amazing ability to
turn a glider with just the rudder, I also have the ability to enter a
spin from a coordinated turn! I've done it in our club's Blanik and my
current glider, and I think it works on most gliders. Here's my secret:

*enter a coordinated, shallow (say, about 10 degree bank) turn
*reduce the airspeed slowly while keeping the yaw string straight
*at some point, the inner wing will drop, and the spin begins (it might
be spiral dive with some gliders)
*recover in the usual fashion when desired (I prefer to do it sooner
than later)

Of course, the glider's attitude is nose high, along with other warning
signs that the pilot is not doing things right. Still, I wonder how many
pilots unintentionally flew too slowly, but thought they were safe
because the yaw string was centered.

The understanding of just what a centered yaw string indicates is
something I have always struggled with.

After some thought experiments, and some flying experiments too,
I have come to my own realization that I must never assume that
a centered yaw string indicates anything about the angle of attack
occuring on the left and right wings.

In a coordinated turn, that is, a turn during which the yaw string
is centered, the angle of attack of the inside and outside wings is
not the same. the AOA of the inside (on the turn side) wing is
greater than the AOA of the outside wing and will stall before the
outside wing, and if the pilot allows this process to further develop
the glider will enter a spin.. We all know this, but I have to keep
reminding myself. The centered yaw string is not an indication of
equal AOA of the two wings. It only indicates the direction of air
flow right where the yaw string is. I think I better write this
on a postit and stick it to my panel!