RE: [Jsbsim-devel] Spins, wrecks, and wind

[Tony P. <ap...@ea...>]

On Tue, 2003-07-08 at 19:18, David Megginson wrote:
> Jon Berndt writes:
> 
>  > > What are the philosophical issues?  Intentional spins are an important
>  > > part of many training regimes, not to mention aerobatic flight and
>  > > simple recreational flying, so they're a desirable thing to model.
>  > > Many common trainers, including the Cessna 150, Cessna 152, Cessna
>  > > 172, Cherokee 140, Tomahawk, and (I think) the J3 Cub are all
>  > > spin-certified, at least in the utility category.
>  > 
>  > That's just it.  It's too important not to model with a high degree of
>  > fidelity, and I don't believe any of our FDMs are up to that.  Providing
>  > negative training in something this critical is a bad idea.  I suspect
>  > that's what Tony is getting at.
> 
> JSBSim' stall modelling is better than it used to be, but it started
> off very far from perfect and we never hesitated to model it, despite
> the fact that stalls are at least as critical as spins.

Yes, but recovery from a straight ahead stall is a predictable thing.
I've never heard of an airplane that won't gain speed given nose down
input and power.  Spin recovery technique, OTOH, varies from aircraft to
aircraft and technique that's goodness on one can make things worse on
the next.

> 
> As far as I understand, a spin is not that hard to explain -- it is a
> self-sustaining state where one wing is stalled and one wing is not.
> The problem is simply that JSBSim uses whole-aircraft coefficients,
> which make this behaviour very difficult to model (ditto for
> tail-stalls).

Yes.

> 
> 
> All the best,
> 
> 
> David
-- 
Tony Peden <ap...@ea...>