Re: spins from coordinated flight

>> Ok, then what exactly is "yaw"?  My understanding is that it is a change
of direction of the longitudinal axis of the aircraft in the plane that is
roughly coplanar with the wings.
> 
> Yaw, as we define the term in flight test as it relates to directional
stability is defined as moments about the VERTICAL axis, not the
longitudinal axis.

Yes, that is pretty much what I said.  Change in direction =of= the
longitudinal axis, =in= the plane (of the wings), [(therefore) =about= the
vertical axis.]  I am however using "vertical" and "horizontal" as
referenced to the aircraft, not the earth, thus when the aircraft pitches
up, the yaw axis (as I understand it defined) would change.

Jose
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