Jon Berndt said:
> > Earlier we had a report of a reset issue on the list. It appears that the
> > problem only affects a couple JSBSim aircraft...the c172 (all of
> > them) and the 737. Everything else seems to trim fine.
>
> I wonder why this is only an issue with these aircraft ???
>
> > Which is why I'm calling this a JSBSim bug. If the altitude is < -9990
> and/or
> > the ground_elelvation is < -9990, would it be possible for JSBSim to not
> > ground trim and instead go for a coffee or freeze or whatever it
> > needs to do while the scenery system gets wound up?
>
> So, which one is the key? What is "altitude" in the above context? I assume
> you are not talking about aircraft altitude ... ? What kind of re-init is
> desired or expected?
>
> > In other words, rather than try and find another bandaid, what
> > I would like to do is remove the elevation test from following code in
> > main.cxx and let the fdm take care of itself:
> >
> > if ( !cur_fdm_state->get_inited() &&
> > globals->get_scenery()->get_cur_elev() > -9990 )
> > {
> > SG_LOG(SG_FLIGHT,SG_INFO, "Finally initializing fdm");
> > cur_fdm_state->init();
> > if ( cur_fdm_state->get_bound() ) {
> > cur_fdm_state->unbind();
> > }
> > cur_fdm_state->bind();
> > }
>
> I'm all for "doing it right". I'm sure we can change this to make any
> proposal work. I'm a little rusty on this stuff, though, so the more input
> you give me the better.
It's probably just ground_elev, although I notice the altitude is -9999 on the
first pass. The init and reinit is fine, what is broken is how a bogus value
(ground_evel of < -9990) is handled. The ground elevation test in the
scenery code returns -9999 when the current scenery tile isn't loaded yet.
I'm going to try testing the ground_elev in the update() call in JSBSim.cxx,
but there are several places where elevation is looked at and it isn't clear
to me where (or if) trouble might occur. Probably just checking before
calling dotrim() will fix this particular issue. I would just ask the
question, "if we knew that the elevation (and/or altitude?) values could be
bogus, what would we do differently?" The other question I guess is how we
define "bogus". Is "< -9990" for any value sufficient?
As far as why those two aircraft not the others... I was hoping someone else
might know :-)
Best,
Jim
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