"Bob Chilcoat" wrote in message ...
Ron,

I posted this over on RAP but apparently managed to stump everyone. I
thought that perhaps some of your contacts at Boeing might know if this
word, "unporting" was misused by Gann, or is an old term that is no longer
used. It just doesn't sound right to me.

Bob,

The term was properly used. In this context, unporting means moving the
leading edge of an elevator counter weight from behind the horizontal
stabalizer into the free stream. Think of a frise style aileron. Most of
the Cessnas have them. They have a sharp leading edge placed down at the
bottom of the surface. As soon as you move the wheel to deflect the
aileron up the leading edge deflects down (unports) into the flow off the
bottom of the wing.

From Perkins and Hage "Airplane Performance Stability and Control": "The
pure frise type aileron is characterized by an asymetrical sharp nose
located on the airfoil lower surface so that it will unport as soon as the
control is deflected upward."

In Gann's case, the elevator must have had a part of the elevator leading
edge that was ahead of the rest of the leading edge. This would be both for
static and aerodynamic balance. Normally, in high speed flight the tail is
loaded so that it is not deflected very much. The balance would be hiding
behind the stabilizer and wouldn't cause much of a load on the tail. Had
Gann slowed down it would have been necessary to increase the deflection of
the elevator to keep the airplane balanced. Eventually the balance would
have unported causing a large load on the elevator. With the bolt gone, the
elevator would have bent causing an even greater download on the tail and so
on until either the surface failed or the airplane departed from controlled
flight.

Rich