David M. wrote:
I tried to fix this problem in JSBSim a year or two ago, and I seem to
recall that no one on the flight model list could quite figure out how to
code it back then. I also took a stab at YASim, and failed just as
miserably. Neither model is set up to have the propeller
David Megginson wrote:
When you shut down the engine in YASim, the propeller does not
windmill -- it just slowly spins down and stops.
Probably because of the internal engine friction, I was looking at the
propeller only. What's the right windmilling RPM? I can tune, but
need numbers. :)
Andy Ross wrote:
Probably because of the internal engine friction, I was looking at the
propeller only. What's the right windmilling RPM? I can tune, but
need numbers. :)
The higher the airspeed, the higher the windmilling RPM. Using my very weak
math and physics skills, a fixed 60-inch-pitch
Well Done!
All the best,
Matt.
On 16:11 Wed 04 Feb , Ryan Larson wrote:
I just got back from taking my Commercial Pilot, Airplane Multiengine
Land checkride, and I am happy to say that I passed! Doing a single
engine ILS down to minimums is lots of fun! I took the test in a Piper
Aztec
There's also various scenarios of asymetric thrust - two running engines but one
running roughly or not developing as much power for a plethora of possible reasons.
These incidents have killed many pilots on take off as they think they have plenty of
power, and they do, but the situation
Andy Ross wrote:
That's no doubt true, but hopefully it's more a lack of tuning than it
is a fundamental flaw. For the specific case of YASim: the asymmetric
thrust effects should be more or less correct as-is, because it
applies the force at the location of the engine. The blue line speed
is
The thrust from the good engine is only half the asymmetry -- the
other half is the drag from the windmilling engine (until the pilot
feathers the propeller).
Good point. That's something that's also not too hard to fix.
I could not (yet) find my NACA report on the light twin, but here are
Jon Berndt wrote:
How do we not work well in this case? Do you notice a specific inadequacy?
Yes -- neither JSBSim nor YASim does a good job generating drag for a
windmilling prop.
All the best,
David
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Jon Berndt wrote:
The thrust from the good engine is only half the asymmetry -- the
other half is the drag from the windmilling engine (until the pilot
feathers the propeller).
Good point. That's something that's also not too hard to fix.
I could not (yet) find my NACA report on the light twin,
Jon Berndt wrote:
Good point. That's something that's also not too hard to fix.
I tried to fix this problem in JSBSim a year or two ago, and I seem to
recall that no one on the flight model list could quite figure out how to
code it back then. I also took a stab at YSBSim, and failed just as
On 2/5/04 at 2:36 AM David Luff wrote:
On 2/4/04 at 8:24 PM Curtis L. Olson wrote:
Also, speaking of FDM's. The current JSBSim C172 in cvs seems to have an
engine that can break 3000 rpm in level cruise (150-160kts). That's
clearly way too high for C172. I'm guessing from the engine rpm's
David Luff wrote:
I guess someone who knows JSBSim well needs to look at why the config file
value isn't getting picked up anyone.
I guess it would be a good idea to initialize the various variable
*before* the get initialized by the configuration file ...
Erik
David Luff wrote:
I guess someone who knows JSBSim well needs to look at why the config file
value isn't getting picked up anyone.
Done.
Erik
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David Luff wrote:
I guess someone who knows JSBSim well needs to look at why the
config file
value isn't getting picked up anyone.
Done.
Erik
smacks forehead
Thanks, Erik!
Jon
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David Megginson wrote:
I tried to fix this problem in JSBSim a year or two ago, and I seem to
recall that no one on the flight model list could quite figure out how
to code it back then. I also took a stab at YSBSim, and failed just
as miserably. Neither model is set up to have the propeller
Andy Ross wrote:
Windmill (i.e. zero torque) speed is 450 RPM.
Windmill drag at that speed is 47N, about 10.5 pounds of force, or
about 5 equivalent horsepower at that airspeed.
When you shut down the engine in YASim, the propeller does not windmill --
it just slowly spins down and stops.
All
David Megginson wrote:
Andy Ross wrote:
Windmill (i.e. zero torque) speed is 450 RPM.
Windmill drag at that speed is 47N, about 10.5 pounds of force, or
about 5 equivalent horsepower at that airspeed.
When you shut down the engine in YASim, the propeller does not windmill
-- it just slowly
Curtis L. Olson wrote:
I see the same thing in the JSBSim c172, except that it spins down
rather quickly and stops.
I've never shut down an engine in flight in real life, but from reports I've
heard, you have to bring a 172 almost to the stall to stop the propeller
from windmilling; once
On 2/5/04 at 7:10 PM David Megginson wrote:
Curtis L. Olson wrote:
I see the same thing in the JSBSim c172, except that it spins down
rather quickly and stops.
I've never shut down an engine in flight in real life, but from reports
I've
heard, you have to bring a 172 almost to the stall
I just got back from taking my Commercial Pilot, Airplane Multiengine
Land checkride, and I am happy to say that I passed! Doing a single
engine ILS down to minimums is lots of fun! I took the test in a Piper
Aztec (PA23-250).
The hardest part of the checkride was trying to get the aircraft
Ryan Larson wrote:
I just got back from taking my Commercial Pilot, Airplane Multiengine
Land checkride, and I am happy to say that I passed! Doing a single
engine ILS down to minimums is lots of fun! I took the test in a Piper
Aztec (PA23-250).
Congrats!
On a related note, I'd like to
On a related note, I'd like to figure out how to make FlightGear more
useful
for ME practice -- I don't think either of the main FDM's does a very good
job on single-engine, but I don't have any real experience to
compare them with.
?? This is confusing on several fronts. You don't have any
On 2/4/04 at 8:24 PM Curtis L. Olson wrote:
Also, speaking of FDM's. The current JSBSim C172 in cvs seems to have an
engine that can break 3000 rpm in level cruise (150-160kts). That's
clearly way too high for C172. I'm guessing from the engine rpm's that
this is an engine or prop
Jon Berndt wrote:
for ME practice -- I don't think either of the main FDM's does a very good
job on single-engine, but I don't have any real experience to
compare them with.
?? This is confusing on several fronts. You don't have any single engine
experience?
Not in the context of ME
Jon Berndt wrote:
On a related note, I'd like to figure out how to make FlightGear more
useful
for ME practice -- I don't think either of the main FDM's does a very good
job on single-engine, but I don't have any real experience to
compare them with.
?? This is confusing on several fronts. You
The main one that comes to mind is that with an engine out there is a
minimum speed you must maintain, or else the torque of the good engine
will
overcome the ability of the rudder to hold heading and you end up
spiraling
until you can get the nose down enough to pick up some speed. Not fun
?? This is confusing on several fronts. You don't have any single engine
experience?
Not in the context of ME (multi-engine) flying.
Aha! OK, I would call that engine-out experience.
Jon
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for ME practice -- I don't think either of the main FDM's does a very
good job on single-engine, ...
I think JSBSim does a good job of modeling single engine operation. The big
problem is with these cheesy twist-grip rudder controls on the joysticks.
They make the engine-out work harder
Curtis L. Olson wrote:
The real fun comes from practicing with only one engine running
[...] There are some real world effects that are important for
training which I don't think we model well on existing twins.
The main one that comes to mind is that with an engine out there is
a minimum
Andy Ross wrote:
Curtis L. Olson wrote:
The real fun comes from practicing with only one engine running
[...] There are some real world effects that are important for
training which I don't think we model well on existing twins.
The main one that comes to mind is that with an engine out there is
On Wed, 2004-02-04 at 19:54, Curtis L. Olson wrote:
Andy Ross wrote:
Curtis L. Olson wrote:
The real fun comes from practicing with only one engine running
[...] There are some real world effects that are important for
training which I don't think we model well on existing twins.
The
Curtis L. Olson wrote:
It very well could be a model setup issue at which point it's probably
beyond my ability to debug, but with the JSBSim c310, I took off,
climbed to a comfortable altitude and speed, and chopped the throttle
on my right engine. Then I slowly pitched up to bleed off speed
On Wed, 04 Feb 2004 21:54:41 -0600,
Curtis L. Olson [EMAIL PROTECTED] wrote in message
[EMAIL PROTECTED]:
Andy Ross wrote:
Curtis L. Olson wrote:
The real fun comes from practicing with only one engine running
[...] There are some real world effects that are important for
training
BTW, does FG currently simulate P-factor?
JSBSim does, and IIRC YASim does as well. JSBSim does it with a tweak that
offsets the point of force application. It could probably be done better if
we set our minds to it, and it is a factor that needs to be set from testing
and experience - i.e.
I'm sure this is just a matter of tweaking the configuration file. But
this is an important behavior to have reasonably correct in small twins.
Yes, it would most certainly be a setup issue in the config file. I've got
a book of aero data for a twin around here somewhere. I'll see if I can
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