Mechanics of Elevator Trim. In Detail.

One point about the lift fairy sitting on the tail I'd like to
understand is this -- actually a serious question. As I understand
it, nearly aways the tail is exerting a downward force, since the
center of lift is aft of the center of gravity on general aviation
airplanes (that is true, isn't it -- that the cg is forward of the
center of lift?). If so the tail really is imposing an increased load
on the airplane, adding to its effective weight. The question I have
is, how many pounds of weight is imposed aerodynamically for an
airplane that might be loaded with its CG at the forward limit? I
don't know where the center of lift is on ga airplanes -- a third of
the way aft of the leading edge of the wing is an ok approximation,
but a few inches error on an airplane weighing what ours does at max
could make a huge change in the required force to overcome the nose
heavy moment.

I'm obviously thinking about increased efficiency -- extra weight
added because of either fat people, full fuel, or aerodynamically
imposed, all cost horsepower (OK, watts for you purists) to move
around.



. On Jun 8, 5:18 am, WingFlaps wrote:
On Jun 8, 5:08 pm, Le Chaud Lapin wrote:



Hi All,

This post is primarily directed toward student pilots like myself.

First, I am not asking because I want to know the answer (I already
know), but do a little experiment. I have maybe 7 or 8 different
sources of flight information that I rely on for ground school
(Jeppesen, FAA Handbooks, etc), and none of them said _how_ it worked
in sufficient detail, they only said what one must do to make the
plane pitch up or downard.

So for you students, please do not cheat and do what I did, which is
watch the airfoils move as you move the trim control. Also, it would
help if you did not think about the correct answer too much, which
would lead you to the correct answer, thereby defeating the purpose of
my experiment.

So, without cheating, and without asking an experienced pilot or
mechanic,...

What exactly happens when the trim is adjusted to point the nose
upward?

Well, since you frame it as a troll:
You scare the lift faries to run forward by waving a very nasty bit of
metal at them.

YAWN
Cheers