No, I'm thinking of the trim tabs themselves. When you adjust trim,
the tabs move, and deflect the control surface in the opposite
direction of their movement--thus relieving you of the effort required
to move those control surfaces. They relieve control pressures by
moving the control surfaces for you, but the control surfaces _do_
move.

Than is the reverse of the manner in which trim is used--and a guaranteed
way to determine the full extent of foul language which your instructor may
have learned during his lifetime!

The accepted standard procedure is to fly the airplan with its primary
flight controls, and use the trim to reduce/eliminate the required control
pressure. Therefore, any movement of the control surfaces is ignored--there
will be none when the primary controls are simply biased with springs, very
little when there are trim tabs, and more when there is a fully trimming
stabilizer. However, if the amount is signifcand, you were badly out of
trim in the first place--which is another great way to keep your instructor
excited and talkative...

BTW, in calm air, it is possible to fly by use of the trim--although not
very well. Several crews have survived primary control failures on aircraft
which they could not abandon in flight, and the aircraft was saved as well
on at least one occasion. However, there is NO reason for a sane person to
practice that, even in a simulator, unless he has reason to suppose that he
might be the victim of such a failure.

Peter