Alex Perry wrote:
I've never noticed it, but that doesn't mean it doesn't happen. For
most throttle transients, the combination of prop momentum, throttle
pump and induction system effects will hide the blade stall
transition. Especially true if you have a controllable prop.
Have
It is gradual. In fact, if you think about it, it has to be. A
propeller that presented the same AoA at every point along the blade
would have to change its degree of twist as the advance ratio changed.
I was just wondering whether the twist happened to correspond to the
AOA-plus-advance so
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
David Megginson wrote:
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
Andy Ross writes:
Basically, if I understand the request, it should be sufficient to set
the takeoff-rpm value to 2100 or so, while leaving the cruise value
alone. That should do what you want. I didn't bother to look up real
numbers when I did most of the YASim planes, so this is
David Megginson wrote:
Andy Ross writes:
Basically, if I understand the request, it should be sufficient to set
the takeoff-rpm value to 2100 or so, while leaving the cruise value
alone. That should do what you want.
I'm not sure that's right. By the time the plane is moving fast
Nope; you can fairly easily get the RPM over 2700 in a fast cruise descent,
but there is no way you'll manage over 2500 at Vy, never mind Vx.
Andy Ross writes:
Basically, if I understand the request, it should be sufficient to set
the takeoff-rpm value to 2100 or so, while leaving the
Alex Perry writes:
Nope; you can fairly easily get the RPM over 2700 in a fast cruise descent,
but there is no way you'll manage over 2500 at Vy, never mind Vx.
We're modelling a C172R, which maxes out at 2400RPM. Would the same
apply there?
All the best,
David
--
David Megginson
You should talk to Andy and look at the prop model; the faster you go,
the faster the prop can turn. Fast cruise descents can overspeed.
I'm not at home and can't look up the exact numbers, sorry.
Alex Perry writes:
Nope; you can fairly easily get the RPM over 2700 in a fast cruise
Alex Perry writes:
You should talk to Andy and look at the prop model; the faster you go,
the faster the prop can turn. Fast cruise descents can overspeed.
I'm not at home and can't look up the exact numbers, sorry.
In JSBSim, the prop maxes out between 2065 and 2165 RPM at 0 velocity,
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
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