> Coming back to the (default) JSBSim Cessna 172p after spending a couple of
> months flying the YASim pa28-161, I find the 172 extremely slippery, far too
> much for a trainer.  While the Cherokee tends to feel more stable in flight
> than a 172 (i.e. it has more roll, pitch, and yaw damping), the 172 still
> shouldn't be nearly so light in roll, pitch, or especially yaw as it
> currently is.
>
> I've made a patched-up file that allows the 172p to handle much more
> realistically, but I'm not willing to upload it to CVS yet, because I'm not
> sure that I've done the right thing.  To keep the 172 from wallowing, I
> increased the roll damping coefficient (Clp) from -0.484 to -1.2, the pitch
> damping coefficient (Cmq) from -12.4 to -15, and the yaw damping coefficient
> from -0.0937 to -0.2.  The patched file ($FG_ROOT/Aircraft/c172p/c172p.xml)
> is available at
>
>    http://www.megginson.com/Aviation/c172p.xml
>
> I don't want to commit this file to CVS yet for a couple of reasons:
>
> 1. Increasing the damping may simply mask a different problem, such as a
> unit mismatch or mistaken value for another coefficient (the biggest problem
> comes around yaw/roll coupling) -- someone who understands aerodynamics
> better needs to look at the actual moments generated by each coefficient at
> runtime to see if they are out of whack.
>
> 2. I have over 200 hours in a Piper since I last sat in a Cessna 172, so I
> don't know how accurate my memory is of its handling -- I remember that it
> felt a bit less stable than a Cherokee, but as a trainer, it still had a
> *lot* of damping compared to a high-performance aircraft.
>
> My revised file seems to fly much better to me, but I'd like to hear
> opinions from other people with real experience in 172's, as well as the
> aerodynamic engineering types.  I'd also be interested in feedback from
> non-pilots about the handling difference.

Thanks, David. There are a couple of things I can think of to do, here. One is that I 
sure
wish I had time to make a DATCOM model of the C-172 that could give me some aero data 
for
comparison. But with my schedule now I can't make any promises, but I will get to this
someday! The second comment is that it ought to be possible to get some real numbers 
for
you pretty quickly from comparable aircraft. I think I can do that tonight or tomorrow.
Third, there are some equations that ought to shed some light on things. Fourth, it 
will
be interesting to see if pilot perceptions suggest altering all/most coefficients in 
the
same direction for all aircraft in order to give the perception of proper flight
characteristics.

Jon


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