Re: [Flightgear-devel] Turn ball fix & JSB notes

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

On Monday 27 August 2001 04:46 pm, you wrote:
> > > In any case, I believe the accelerations the pilot feels should be the
> > > acceleration of the center of the vehicle (total acceleration in local
> > > coords including gravity)
> > > [...]
> >
> > Ack, no.  That's the bug!  Think about it: what's the total
> > acceleration in local (!) coordinates of an F15 in a 9G turn?  Well,
> > this second, the air is flowing directly at me at 260 knots.  It was
> > doing that last second too, and the next second will be the same.  So
> > the acceleration is zero.  Bzzt.  The acceleration is 9G, but you
> > can't see that in the plane's (accelerated) reference frame.  You can
> > ONLY see that acceleration with reference to the ground (or another
> > unaccelerated) reference frame.
>
> No. I was correct. We may be confusing local coords with body coords. THe
> acceleration the pilot feels is:
>
> acceleration of aircraft cg in local coords
>
> +
>
> w X (w X r)

According to Etkin there is another term

 vPilotAccel = Translation->GetUVWdot()
                    + Rotation->GetPQRdot() * vToEyePt
                    + Rotation->GetPQR() * (Rotation->GetPQR() * vToEyePt);

and that is how we calculate it.

>
> Definition: Local frame = world frame ... sort of)
>
>
> I'll respond more later. I am being called for dinner.
>
> Jon
>
>
> _______________________________________________
> Flightgear-devel mailing list
> Fli...@li...
> http://lists.sourceforge.net/lists/listinfo/flightgear-devel

-- 
Tony Peden
ap...@ea...
We all know Linux is great ... it does infinite loops in 5 seconds. 
-- attributed to Linus Torvalds