Trim tab location

I have wondered why some aircraft, use a small moveable control
surface seperate from the normal controls. I believe I have seen this
in the form of a small wing under the horizontal stab being used as
elevator trim.
I once installed a trim tab on the back of the elevator on an
Ultralight Challenger and induced severe flutter, something I did not
want to repeat and obviously it is more than just deflecting the
control.

Ray

On Thu, 24 Jun 2004 10:16:24 +0200, "Jan Carlsson"
wrote:

A small tab at the trailing edge is moving the control surface so the
control surface is doing the job (trimming) by a small change in the angle,
if the trim tab is sitting on a fixed part of the plane a bigger tab and or
angle is needed.

Jan

"Jay" skrev i meddelandet
. com...
I've noticed that a lot of aircraft put trim tabs on the trailing
edges of the normal movable control surfaces. Wouldn't this just
deflect the control surface to neutralize the forces and not affect
much change except drag? It seems like you'd want to put the trim tab
on the fixed part of the wing/stab/vert, that way its pushing the
airplane instead of the flight controls in your hands. I've noticed
some articulated mechanisims on some aircraft (anti-servo) but this
seems to be a complicated way to make up for the fact that the tab was
put in the wrong place to begin with. What am I missing?