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

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

On Tuesday 28 August 2001 04:30 am, you wrote:
> On Tue 28. August 2001 00:38, you wrote:
> > On Monday 27 August 2001 11:28 am, you wrote:
> > > Observation number one was that the problem is specific to the JSBSim
> > > code.  When using LaRCsim, the ball behaves more or less like it
> > > should.  A few printf's later, I thought I had it: when asked for the
> > > local (pilot) acceleration, LaRCsim will return a value including
> > > gravity, but JSBSim won't.  The Z component of JSB's pilot
> > > acceleration is zero when the plane is stopped on the ground, LaRCsim
> > > reports -32.1 ft/sec^2.
> >
> > While it is certainly true that gravity is acts on the aircraft, it is
> > also true that while at rest on the ground, the ground is acting on the
> > aircraft as well.  In fact, the force produced by the ground should be
> > exactly equal and opposite to that produced by gravity.  Therefore, the
> > total vertical acceleration of the aircraft is zero, not 1.0 or -32.174
> > ft/sec^2
>
> This is IMHO wrong idea. Because here you talk about pilot accels.
> When you are counting with gravity as acceleration, and  when you are
> sitting on the ground, you are moving (and ground  with you)  acceleration
> 9.82 m/s^2 up. The acceleration is zero only when you make free fall.
> When you are not counting gravity as acceleration then you are right, but
> then you mast add gravity force to result to properly simulate forces which
> act on pilot.

I will agree that the pilot *feels* the seat pushing up on him and that 
reporting the accels that way is fine with the understanding that we're 
attempting to report what the pilot might feel and not necessarily anything 
about his motion.
  

>
> Regards,
> Madr

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