I am testing out a small preliminary fix for the landing gear jitter seen in
various
JSBSim aircraft. Curt has relayed that the default C-172 does have this problem
- and I
have now seen that. The preliminary fix does seem to have fixed that, although
when brakes
are applied while at rest there
Actually, in the English system the mass unit is slugs - not pounds (lbs):
Thanks, I stand corrected.
-Gerhard
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differential equation sense). Fixing *this* by interpolating the
force function over small velocities leads to a stable but
non-physical solution that exhibits the drift problem that was
talked about.
Ah, OK. So did I get this right, here's a tradeoff between the
``physically correct''
be skidding at any given moment. The notion of holding forces at
zero makes intuitive sense, but underneath that it has very little
physical meaning.
On the contrary. I haven't followed this discussion too closely and I'm
no physicist either, but this sounds to me exactly like static vs.
depending on tire pressure (etc.) I'd guess that it takes somewhere
between 100-200 lb of force (is that the right term?) to start a
Almost :-)
The actual physical unit of force is the Newton [N=kg m/s^2], which is
the force needed to accelerate an object of 1kg with 1 m/s^2, i.e.: The
In practice, humans feel the _weight_ of objects as a force which is the
product of its mass (lb or kg) and gravity (~9.81 m/s^2). Because
gravity is, by and large, constant on our planet, this force and the
mass are proportional. Hence one often uses mass (lb) to denote forces.
The force
Hi,
I'm no math or phisics genius but I was wondering if anyone has
tried making the friction logarithmic. As in high friction at slow
speeds and quickly dropping to normal friction.
This is just a suggestion. :-)
Stephen
___
Flightgear-devel
Hi,
I'm no math or phisics genius but I was wondering if anyone has
tried making the friction logarithmic. As in high friction at slow
speeds and quickly dropping to normal friction.
This is just a suggestion. :-)
Stephen
Actually, there is some truth in this. To show yourself, try
David Megginson wrote:
Again, I'm wondering if this is an aerodynamic problem (aside from
the bouncing-around-sitting-still thing). [...] I expect that the
same applies to the assumptions made by YASim's solver.
I'll take a look. By design, at least, YASim should be reasonably
immune to
Gerhard Wesp wrote:
On the contrary. I haven't followed this discussion too closely and
I'm no physicist either, but this sounds to me exactly like static vs.
gliding friction.
Yes, there are separate coefficients of friction for the static
vs. dynamic case. But these are only different
Jon Berndt writes:
In the end, it could turn out that a physics-based approach is not
worth the effort, and we should simply make the aircraft do what
experience tells us a real aircraft would do.
As either you or Andy mentioned before, the problem is the
transition. Improving the
Jon Berndt [EMAIL PROTECTED] said:
If there were no winds at all, that might help. Otherwise, it doesn't work
at all.
Jon
Let me expand on that. If you do come to a stop, and there are no winds at
the moment, then the winds come up after you have stopped, then having
reduced the
Jim Wilson writes:
So then what would happen if you artificially introduced resistance at the
same time (near zero velocity) in a manner similar to a partially applied
parking brake?
The problem is that if the landing gear produces opposing forces or
moments that are too great, the plane
Andy Ross writes:
Hrm... well that throws a wrench into the static spring force while
stopped idea. Maybe it could be salvaged by doing the static spring
computation only in the (1D) transverse direction...
Again, I'm wondering if this is an aerodynamic problem (aside from the
On Mon, 17 Nov 2003 11:33:35 -0500
David Megginson [EMAIL PROTECTED] wrote:
Again, I'm wondering if this is an aerodynamic problem (aside from
the bouncing-around-sitting-still thing). Because of its lifting
surfaces, a plane is certainly more vulnerable to the wind than a car,
even when it is
David Megginson [EMAIL PROTECTED] said:
Jim Wilson writes:
So then what would happen if you artificially introduced resistance at the
same time (near zero velocity) in a manner similar to a partially applied
parking brake?
The problem is that if the landing gear produces opposing
Jim Wilson wrote:
Can't we bring in some sort of damping factor that would just render the
aircraft stuck at very small velocities, but would still allow it to become
unstuck if a great enough force was applied? A sort of automatic parking
break that gets applied gradually starting at 0.01 fps
David Megginson wrote:
I was amazed at how tricky this got a year or so ago when I was
experimenting with it. I agree that we need some kind of damping at
slow speed. Essentially, the gear forces have to become a special
case, reducing forces and moments towards zero but never beyond into
David M. wrote:
Unfortunately, not -- when the JSBSim and YASim aircraft are rolling,
they are still far too much affected by the wind. In real life, even
with 30 kt gusts, you can usually taxi a 172 or Cherokee around as if
it were a car. Personally, I do set the controls appropriately
At flaps-1 the LE flaps (inboard of the engines) all come out all the way, and
all the LE slats (outboard of the engines) come out half way. At flaps-10
all the LE slats come out all the way.
If at any time you approach a stall with flaps at less than 10, the autoslat
system will extend the
Thanks Dave will keep it in mind when doing the panel.
Cheers
Innis
David Culp writes
At flaps-1 the LE flaps (inboard of the engines) all come out all the way,
and
all the LE slats (outboard of the engines) come out half way. At flaps-10
all the LE slats come out all the way.
If at any time
Innis Cunningham wrote:
Hi Guys
Also is there a way to put a time delay in XML.The flap needle moves way
to fast compared with real life.And were is the xml code that will allow
more than three steps between flaps up and flaps down.Or is this hard
coded.
These can all be set in the
Is there somewhere in the docs that gives what boolien expressions work for
the FlightGear XML.
The T38-gear.xml config has an example of how to do a conditional statement in
xml.
Also is there a way to put a time delay in XML.The flap needle moves way to
fast compared with real life.
The
Thanks David and Eric
I have got the Flaps to read to 40 in three steps just by changing the
scaleing and the offset.Once I can get the required increments I will try
David Megginson's interpolation method.
David the 737 flap guage shows 1,5,10,15,25,30 and 40 are all these
increments used in
David the 737 flap guage shows 1,5,10,15,25,30 and 40 are all these
increments used in the real aircraft.
Yes, and 2 as well. Takeoff with flaps 5. Land with 30 or 40 (short field).
One thing that isn't modeled exactly yet is the relationship between flap
detent, flap position, and flap
Sorry Dave forgot the two.Also when do the leading edge flaps run and are
they split or do all sections run at once.
Cheers
Innis
David Culp writes
David the 737 flap guage shows 1,5,10,15,25,30 and 40 are all these
increments used in the real aircraft.
Yes, and 2 as well. Takeoff with
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