I'd like to suggest a couple of changes to the YASim piston-engine
model, keeping in mind Andy's past caveats that it is very simplistic.
The most important one is idle RPM. Currently, the YASim c172 idles
at about 1,350 RPM. From what I've found, recommended RPM for taxiing
a C172 is only about 900 RPM, and some checklists I've see state that
the engine should be idling at over 575 RPM, so I'd guess that 600-750
RPM is probably the right range.
The second one has to do with static RPM. Under "Propeller Limits",
the C172 TCDS lists a maximum static RPM at full throttle of
2,065-2,165. That's well under the maximum 2,400 RPM for a C172R in
motion. Currently, the YASim C172 prop goes right up past 2,400 RPM
even when the plane is not moving.
It would be possible to get these numbers for the C172 by tweaking the
math in PistonEngine.cpp, but then another aircraft might not work.
It would be more in the spirit of YASim simply to provide the numbers
in the config file and interpolate. Where right now, the config file
has
<propeller radius="1.0"
cruise-speed="86" cruise-rpm="2200"
cruise-alt="10000" cruise-power="99"
takeoff-power="160" takeoff-rpm="2500"
eng-power="160" eng-rpm="2500"
x="-.6" y="0" z="0" mass="400" moment="8">
we could have something along the lines of (with an unsubstantiated
guess for idle and static power)
<propeller radius="1.0"
idle-rpm="750" idle-power="45"
static-rpm="2100" static-power="145"
cruise-speed="86" cruise-rpm="2200"
cruise-alt="10000" cruise-power="99"
takeoff-power="160" takeoff-rpm="2500"
eng-power="160" eng-rpm="2500"
x="-.6" y="0" z="0" mass="400" moment="8">
YASim could interpolate between static RPM/power and takeoff RPM/power
to find the effect of velocity, and between idle RPM/power and static
RPM/power to find the effect of the throttle. The engine model would
work much more realistically with only a little more work.
Comments?
All the best,
David
--
David Megginson
[EMAIL PROTECTED]
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