David Megginson wrote:
> 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.
OK, I've hacked at the idle RPM code a bit to reduce the idle MP.
This is, well, a hack; but it puts the idle in a saner range on the
DC-3 and C-172 without affecting full-throttle performance.
Try the following patch to c172.xml, which makes the takeoff-rpm
modification I talked about*. Hopefully things will be more to your
liking; the aircraft maxes out at 2100 RPM while stopped, then the
speed increases to something more like cruise as the airspeed grows.
If you look carefully, you'll actually see the RPM drop very slightly
before it starts increasing. The physical reason for this is that the
blades are "unstalling". As the flow attaches to them, they
experience a sharp increase in induced drag. I was pretty pleased to
notice this little tidbit; it kinda validates the model in an obtuse
way. That being said, I have *no* idea if this effect is noticeable
in a real aircraft. Alex?
Anyway, the patch to c172.xml:
diff -u -r1.5 c172.xml
--- c172.xml 2002/03/01 07:27:27 1.5
+++ c172.xml 2002/04/09 02:57:35
@@ -57,7 +57,7 @@
<propeller radius="1.0"
cruise-speed="86" cruise-rpm="2200"
cruise-alt="10000" cruise-power="99"
- takeoff-power="160" takeoff-rpm="2500"
+ takeoff-power="134.5" takeoff-rpm="2100"
eng-power="160" eng-rpm="2500"
x="-.6" y="0" z="0" mass="400" moment="8">
<actionpt x="0" y="0" z="0"/>
Have fun,
Andy
* And changes engine power at zero speed to reflect the different RPM.
Don't ask why I don't calculate this myself; the reason is ugly.**
** OK, it has to do with the parser design. At the time the element
is parsed, I may not have a valid engine object yet and I was too
lazy to build a parse tree to inspect. :)
--
Andrew J. Ross NextBus Information Systems
Senior Software Engineer Emeryville, CA
[EMAIL PROTECTED] http://www.nextbus.com
"Men go crazy in conflagrations. They only get better one by one."
- Sting (misquoted)
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