Re: [Jsbsim-devel] Longitudinal trim: stab or elevator

[Fabian G. <fab...@gm...>]

On 4/27/08, Tony Peden <ton...@co...> wrote:
>The original trimming routine is set up to trim with pitch trim by
default.  It can be configured to do other things at the >C++ level,
however.

So, with the original trimming routine, I can input the pitch-trim-cmd-norm
to the stab (or maybe a canard) and that will be the surface that will be
iterated to achieve trim?

>For FG integration, using the trim systems is highly desirable as FG has no
way of setting the user's controls (joystick, >throttle, ...)

I understand FG do perform a trim by default after initializing.
Moreover, there's an option to select NO trim before start. In this case, if
the sim is started with the aircraft in the air, it will begin in a crazy
roll/pitch/roll until trimmed by the "pilot".
I still cannot understand if it used the pitch trim or the elevator for
that.
If I start with the aircraft in the air without trim, clicking the pitch
trim button on the joystick moves the stabilizer (in my model), as
expected/wanted. But if I ask for a trimmed start, FG does not start. It
seems it tries to trim with the elevator, but it doesn't know the stab
position, then it has no enough power to trim, I guess. Interesting.

Fabian