Heiko Schulz wrote:
> > I took the opportunity to check the PoH against the
> > simulator experience. While I didn't go as far as getting
> > the OAT exactly right, the errors I came across were fairly
> > signficant (using a HUD to get accurate altitude/TAS etc.)
> >
> > As I think you've noted before, the climb rate is too high
> > - I consistently see 1000ft/min up to 8000ft ASL, instead of
> > approx 800ft/min at sea level, and 400ft/m at 8000ft ASL.
> >
> > In contrast, the cruise speed is a bit too low - I don't
> > recall what I saw at sea-level, but at 8000ft ASL, I saw 107
> > KTAS rather than 120 KTAS (though as that was very close to
> > the IAS, it may be that the environment was not quite
> > right).
> >
> > I'm not sure what to make of this. Perhaps the drag and
> > power should be reduced, or possibly the alpha drag needs to
> > increase?
> >
> > I suspect I need to use JSBSim directly to tune these
> > parameters better.
> >
> > -Stuart
> >
> I wonder if it makes really sense to compare our C172P-model with a real
> C172N.
>
> Both types has different engines and therefore different perfomances.
> That's why I suggested to have one real aircraft with everything, which our
> sim-model is modelled after it.
>
> The manual should only help to get an idea of some stuff, like panel,
> handling.
> But Perfomance is difficult, as it is not the c172P.
Good point - I should have checked that before looking into this in detail.
>From a quick look at wikipedia, the C172N powerplant is an O-320-H2AD,
while the C172P is an O-320-D2J. Both produce a maximum power of
160hp at 2700rpm. The main difference appears to be that the H2AD used
100LL and a 9:1 compression ratio, rather than 91/96LL and an 8.5:1 compression
ratio.
Anyone care to comment on whether that would materially affect the aircraft
performance?
-Stuart
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