Puchaz Spinning thread that might be of interest in light of the recent accident.

On Wed, 04 Feb 2004 14:07:52 -0800, Jim wrote:

On Wed, 04 Feb 2004 16:06:08 -0500, Todd Pattist
wrote:

Bruce Greeff wrote:

You are correct that their vertical component of velocity must be the
same because of geometry, if the bank angle remains constant. However,
because the inner wing is describing a smaller diameter spiral the
relative wind will present at a higher angle of attack on the inner wing
tip - relative to the outer wingtip.

This is quite true, but it's the difference in the
horizontal velocity that causes the difference in the angle
of attack, and IIRC, that's what Robert said in his earlier
post in this thread when he wrote:

"Some difference in AOA between both wings is already
provided by the simple fact that the glider is sinking, i.e.
both wings have the same vertical component of velocity but
different horizontal ones. "

In the same time the inner tip travels a smaller distance, but descends
the same vertical distance, hence the greater angle of descent, not
rate.

True, but Jim was disagreeing with Robert when he
(incorrectly) wrote:

"In a descending turn, which is what gliders do in turns, it
is not the case that both wings have the same vertical
component of velocity."

People seem to continuously confuse rates and angles?

Too true :-)

Todd Pattist - "WH" Ventus C
(Remove DONTSPAMME from address to email reply.)

Thank you for pointing this out! I guess my fingers on the keyboard
out ran my brains. I should not have gone farther than just the
observation that the inside wing in a stable descending turn is
going down while the outside wing is going up ( and the opposite
situation in an ascending turn). I guess I really don't understand
the notion of differing horizontal vs vertical "components".
In other words, the aircraft is actively rolling about its
longitudinal axis during the turns. From this I incorrectly deduced
that one wing was moving downward more than was the other wing.

I also wish I could remember where I first read this description.
It was in a book about stalling and spinning by the fellow who
I believe flew with Tony DeVere and originally set up the
emergency maneuver training at Santa Paula. Oh well, this
is hardly the only memory that has vaporized from my ageing
brain!


Now I remember! The book is "Stalling, spinning and safety"
by Sammy Mason. It's a good read.