AoA keep it going!

I recall a teaching aid used to train WWII pilots. It was a simple table
top wind tunnel made of plexiglass with a "test section" about an inch wide
and 6" high. It came with various aerodynamic shaped bits of plastic that
could be used to visualize flow. There was a small exhaust fan to pull air
through the tunnel and a clever "smoke rake" made with a small electrically
heated pot and a rake made of small diameter brass tubes soldered together.
It was a simple two dimensional wind tunnel.

You put an ounce or so of kerosene in the pot and turned on the heat. After
a bit, smoke started coming out of the dozen or so rake tubes. You then
turned on the fan and neat parallel streams of smoke flowed around the shape
in the test section.

The reynolds number was all wrong but the visualization of air flow was way
more than good enough to get the idea of angle of attack across. The
airfoil shaped test bit was nearly perfect. At about 16 degrees of AOA, the
smoke streams would burble and separate from the upper surface. No one left
the demonstration unconvinced.

The thing was a little messy. To see the smoke streamers clearly you needed
to be in a dimly lit room which quickly filled with kerosene smoke. That's
probably why it isn't used much anymore. Still, I'd love to have one.
Maybe a computer program could be just as good.

The thought occurs to me that those WWII flight schools went to a lot of
trouble to teach AOA and the graduates were among the best pilots ever
trained. Maybe we should take a look at that they did to train them.

Bill Daniels


"fred" wrote in message
...
In my early hours of being instructed, not one went by without stall
and spin practice. They also taught me to look out of the window.
Maybe I've done a thousand or more turns before I found myself in a
spin that I did not intend to happen. I was in an HP11, over a ridge,
with a 1-26 out climbing me. "He can't do that!" With over 60 degrees
bank, I just tightened my turn by pulling back on the stick. I
increased my AoA without concern. Snap!
The ridge was spinning below my nose and getting larger very fast. My
old instincts kicked in. I was looking at the grass when I recovered.

Now, AoA is my favorite subject to teach. My God! The ignorance is
rampant. A tow pilot applied for a job. I asked him what the
approximate angle of attack was for the Super Cub wing when it
stalled. A commercial pilot raised his arm and pointed up about 40
degrees above the horizon. He went home. I was stunned.

A favorite question I use for instruction... Which wing in a turn has
the greatest angle of attack? The pilot has a 50-50 chance at the
correct guess. No matter what his answer, I ask why? I get no answer.

A problem I find is a lack of understanding of "relative wind" Is
there no hope?

I have witnessed a low altitude spin to impact. It was not nice.

Another spin to impact gave me the opportunity to ask the pilot the
question..."What makes the glider turn?
His answer:"The rudder" He was a military acadamy pilot.

We absolutly must teach and demonstrate more angle of attack
recognition and recovery. It doesant take long before you hear or
read about a stall spin fatality, Don't let your stundent go out into
the wold without being trained in ALL aspects of AoA and stall spin
recovery.Maybe the instructor should learn first.
God bless good instructors,Fearless Fred