On 01/12/2007 09:23 AM, Stuart Buchanan wrote:
> Perhaps you could take a look at the FDM ?
That's not really on the list of things I was looking forward to....
> I think that most of the
> coefficients were copied from a c172 (from looking at the CVS logs), so
> are probably inaccurate.
>
> As I've previously mentioned, one of the main issues with the c182 is that
> I have never been in one, so I don't know how realistic the adverse yaw
> etc. is.
Here are some remarks that may give you some idea what I'm talking
about:
1) Fly the 182 sim with the yaw damper turned on, i.e.
setprop("/sim/auto-coordination", 1);
That seems to me to handle pretty much like a real 182,
by which I mean the real native aerodynamics, without any
robot yaw damper.
2) Fly the PA24-250 sim. It handles pretty much the way
I would expect a real 182 to handle.
In particular, note the near-absence of adverse yaw at
cruising speed. Also note the negligible roll-wise momentum,
in the sense that if you neutralize the ailerons the plane
stops rolling almost immediately. The current C182 sim
keeps rolling for a while, which would be realistic in a
twin, but not realistic in a light single.
The 182 is famously heavy on the controls, in particular heavy on
the ailerons, much heavier than the 172, and incomparably heavier
than, say, a Bonanza. As a result of this and related factors, the
182 is considered a "solid" instrument platform.
Here's a scenario to consider: ILS, partial panel.
That is: Vacuum pumps are notoriously unreliable. Suppose you've
lost instrument vacuum, and therefore your AI and HSI. The only nice
airport for many miles around has a 210 foot ceiling and 1000 meters
visibility below the ceiling, with light turbulence at all altitudes.
This is doable, but it's 5 or 10 times harder in the 182 sim than
it is in the real 182, because the sim has those lightly damped
yawing and rolling modes. Once the plane starts woggling, it is
very hard to get it stopped. And then you don't know your rate of
turn (because the turn coordinator is sensitive to rate of roll,
not just to rate of turn) and you don't know your heading (because
the compass is sensitive to all sorts of things). If you are
100% smooth and coordinated on the controls, you can make it, but
if you make one mistake, or if the turbulence gets you, things
could get ugly.
========
For my purposes, in the short run, I'm gonna just turn on the yaw
damper for shooting the ILS partial panel ... and turn it off for
crosswind landings. It would be "nice" if the FDM got the handling
right without the fake robot yaw damper, but I'm not going to lose
sleep over this.
======================
Actually higher on my priority list is the power/flaps/trim interaction.
JSB says he knows how to deal with this.
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