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

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

On 4/27/08, Tony Peden <ton...@co...> wrote:
>
>
> A pitch control issue is always a possibility.  Are the engines running
> when you start FG?
>
>
Tony,
Well, if you refer to the problem I'm having in FG with my aero model, I
start FG in the same way I do with the original HondaJet; engines are at
idle by default. In the original HondaJet everything is fine. In my modified
HondaJet (only the configuration file is changed with my model, where pitch
is buildup from the wing-body-vertical + isolated horizontal tail effect),
FG doesn't launch, and I get the following error:
FGMultiplayMgr::MP_ProcessData: Domain error.
Is this connected to multiplayer mode? but..., I am not running
inmultiplayer mode at all! I just changed the aero and FCS models!

I see (in the FG code) that it performs "A static map of protocol property
id values to property paths,...". Maybe the stabilizer property I defined in
the FCS of my model confuses FG? Maybe that's the reason why the way to work
with an isolated tail is to "use property names to represent something that
they don't exactly name" (see David Culp reply). I saw somewhere in some 747
model that the speedbrakes are used as if they were the horizontal
stabilizer. I think this is not the way we should work (even if we don't
want to model the speedbrakes effects, together with the stabilizer
effects).

David Culp wrote:
>I also prefer pitch-trim-cmd-norm, but be advised that this will break all
the existing model configurations and AeroMatic.

If things work as I understand, the user, or aerodynamic/FCS modeler, will
input the pitch-trim-cmd-norm to whatever aerosurface he/she wants to use
for trim. Existing models will continue to work. Since I've been noticed by
Tony that the original trimming routine do use pitch-trim-cmd-norm for trim,
then this proves we have no problem here. The only issue is the need to add
a stab property (non-existent so far). See issue above.

I don't understand how AeroMatic output would be affected.

Fabian