Pinging Ron Wanttaja - "Unporting?"

Thanks, Richard. I couldn't imagine Gann making something up in what is a
biographical remembrance of his flying experiences, but since he was clearly
no engineer, I also suspected that he could have been wrong. If he'd been a
bit more knowledgeable, perhaps he might have done a better job of
describing the term. OTOH, as "Howard" explained in the quote, if he'd been
more knowledgeable, he might not have survived to write the book.

Marc, if you are interested in flying, you should read the book. One of the
best about flying. In fact, all of his flying books are worth the time,
just because they very accurately capture the feel of flying. JMHO.

--
Bob (Chief Pilot, White Knuckle Airways)

"Richard Isakson" wrote in message
...
"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

"Richard Isakson wrote:

The term was properly used. ....... Had
Gann slowed down .......

I appreciate the pointer to a definition of the term "unporting". While
uncommon, it clearly was used in a way that meant something as Mr. Gann
described it - thanks for the education.

OTOH, this still makes no sense, since the airplane had to fly through
the slow speed regime in order to reach the cruise speeds at which the
tail is lightly loaded, and conversely, had to fly through them twice to
land. Why did the aircraft not crash during those flight regimes?
While the plane may have been in steady state for most of the time it
was flying, it wasn't at full speed for the whole time.....

Also, the issue of the "phantom moving CG" also makes no sense.....


Bob Chilcoat wrote:

... OTOH, as "Howard" explained in the quote, if he'd been
more knowledgeable, he might not have survived to write the book.

Nah, see comments above.....

Marc, if you are interested in flying, you should read the book. One
of the
best about flying. In fact, all of his flying books are worth the
time,
just because they very accurately capture the feel of flying. JMHO.

I appreciate the pointer - maybe I'll check them out if I get some time.
I'd still be interested in the rationale behind the issues raised above,
even if the term "unporting" was a real one, describing a phenomena that
could theoretically lead to some problems.


And for BB, I'm quite suitably chilled, thank you :-).

--
Marc J. Zeitlin
http://marc.zeitlin.home.comcast.net/
http://www.cozybuilders.org/
Copyright (c) 2004

On Tue, 23 Nov 2004 20:26:33 GMT, "Marc J. Zeitlin"
wrote:


Marc, if you are interested in flying, you should read the book. One
of the
best about flying. In fact, all of his flying books are worth the
time,
just because they very accurately capture the feel of flying. JMHO.

I appreciate the pointer - maybe I'll check them out if I get some time.
I'd still be interested in the rationale behind the issues raised above,
even if the term "unporting" was a real one, describing a phenomena that
could theoretically lead to some problems.


And for BB, I'm quite suitably chilled, thank you :-).
++++++++++++++++++++++++++++++++++++++++

Heh, heh.
You are most welcome, Marc.

However, as nafod sez...
There are no equations, so beware. 8-Q


Barnyard BOb --