Marc J. Zeitlin wrote:
Bob Chilcoat asks;


My interest is the word "unporting". It doesn't sound right. I'm an
engineer (biomedical), but not an aeronautical engineer. You

aerospace

engineers out there, is this the right term?


I am an aeronautical engineer, and I've never heard that term other than
in reference to fuel lines. Sounds to me like a load of hooey.


...Gann was not mechanical, and I
was wondering if he got the term wrong.


Sure sounds like it.


"Unporting is the balance destruction of the elevators by

aerodynamic

force. I won't confuse you with theory, but if enough separation

between

the fixed and the balance portion of your elevators occurs.....


This sounds like a very poor laymans interpretation of moving surface
flutter. If a bolt was missing, then the surface (in this case, the
elevator, apparently) could have more motion and less stiffness than it
was designed for, and this could allow the flutter to begin at lower
frequencies (speeds) than it normally would. But "unporting"???


..... But if you had
been the nervous type, if you slowed down, the center of gravity would

have

changed.


The fact that someone thinks that the CG changes substantially with a
change in speed indicates a poor understanding of both aerodynamics and
terminology. People wandering around inside the plane to go to the
bathroom will change the CG more than a couple of degree change in AOA.


..... As
soon as the time came for a normal power reduction and it was

accomplished,

unporting would begin. But not you. In the past you had lost all four
engines so many times, the prospect of losing one gave you relatively

little

concern. So you sat there, fat, dumb, and happy, and you cancelled

all

power reductions. This brilliant decision saved your life the first

time

that day."


And what happened when the plane came in to land - it didn't slow down?
They landed at cruising speed? The air density stayed the same at all
altitudes that day? No change in aerodynamic inputs as the plane went
from cruise to landing configuration?


..... We had some long sessions with our slide rules and we found, my
friend, that you had arranged the only possible combination of power,

speed

and weight which would blockade the chances of unporting."


And if this could possibly be true, at all combinations of climb speeds
and altitudes, cruise speed and altitude, and descent/approach speeds
and altitudes, then the phrase "only possible combination" has very
little meaning.

If this passage is indicative of Mr. Gann's knowledge of aircraft, then
I'm glad that I never read the book.


Interesting passage on this topic.

http://www.rwebs.net/avhistory/fate.htm

Jerry