[I think this didn't get through yesterday, so I'm resending.]
Because of problems with the plane I had originally booked, I ended up
doing circuits in my club's Cessna 172R, precisely the plane we're
modelling. Here are some notes:
1. I love the panel and especially the avionics. Since I was flying
VFR, I didn't actually get to use most of the stuff, though. On
the bright side, I didn't get in trouble for forgetting carb heat,
since there isn't any.
2. From the outside, it is very noticeably a different plane than the
172N or 172P which I have flown before. The wings don't look the same
-- they're fatter and more rounded -- and the preflight walkaround is
different because of the different fuel arrangements (five --count
'em -- separate drains in each wing).
3. At the controls, it's even more noticeably a different plane:
- Startup is different because of the fuel pump, etc.
- It *really* yaws on lift-off -- it feels like you're taking off
sideways if you don't pound the right rudder pedal fast enough.
It's definitely yaw and not roll: the wings stay more or less
level, but the tail spins around hard to the right (pulling the
nose to the left).
- A 70kt climb is very steep and very fast compared to the 160HP
and even 180HP 172's I've flown before. With a pilot, instructor,
and about 70% fuel, we climbed at 70-75kt at a steady 850fpm --
that means something like 40 seconds from liftoff to crosswind
turn.
- The power settings are different, of course, since the engine is
derated to 160HP and 2400RPM, but you don't need a lot. I ended up
throttling back to 1700RPM for a 90KIAS downwind at 1500ft ASL.
- It has a more solid feel -- it tends to stay in whatever attitude
I put it in (within reason). I've read that a 182 feels like that.
- It glides very, very well -- with no significant headwind, it was
too easy to overshoot the runway. I did most approaches with
idle power and full flaps and I still had to start bleeding off
speed before the base turn, and even *then* I had one missed
approach (on a 3300ft runway). With the other 172's on previous
days, I used about 1200-1400RPM power on every approach and cut
to idle only near the threshold (at which point the plane started
dropping like a stone).
- The RPM gauge doesn't start to drop until I've pulled out the
throttle a fair bit. I'm not sure what that means.
According to my instructor, the 172R carries a smaller useful load
but also burns less fuel at any given power setting, though I didn't
get to experiment with either of those.
There are obviously some aerodynamic changes in the 172R as well as
the more obvious powerplant and panel changes. Our JSBSim model uses
mostly the standard 172/182 coefficients that Roskam provides, but
these are probably wrong for the 172R.
A while ago, Alex suggested that we would be better modelling the
172M/N/P (I think), since those are more common. In retrospect, I
agree, for a slightly different reason -- I don't think that we have
access to the right numbers for a 172R.
What does everyone else think? Would you all be happy to see the tach
calibrated to 2700 rather than 2400, and lose 100RPM when you switch
on carb heat?
All the best,
David
--
David Megginson
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