> Take the A320 (on FG) and watch the ball. All I want to know, which
> property to use for trigger function to keep the ball centered.
> since you discussed this topic so deeply, I'm sure someone can name me the
> property...
Here's the yaw section from the T-38 FCS:
<!-- YAW FCS ***********************************************************
-->
<COMPONENT NAME="Rudder Command Sum" TYPE="SUMMER">
INPUT fcs/rudder-cmd-norm
INPUT fcs/yaw-trim-cmd-norm
CLIPTO -1 1
</COMPONENT>
<COMPONENT NAME="Yaw SAS Rate" TYPE="SCHEDULED_GAIN">
INPUT velocities/r-aero-rad_sec
SCHEDULED_BY velocities/ve-kts
ROWS 3
30 0.00
60 5.00
220 3.00
</COMPONENT>
<COMPONENT NAME="Yaw SAS Beta" TYPE="SCHEDULED_GAIN">
INPUT aero/beta-rad
SCHEDULED_BY velocities/ve-kts
ROWS 2
30 0.00
60 0.00
</COMPONENT>
<COMPONENT NAME="Yaw SAS Sum" TYPE="SUMMER">
INPUT fcs/yaw-sas-rate
INPUT fcs/yaw-sas-beta
CLIPTO -0.2 0.2
</COMPONENT>
<COMPONENT NAME="Rudder Sum" TYPE="SUMMER">
INPUT fcs/rudder-command-sum
INPUT fcs/yaw-sas-sum
CLIPTO -1 1
</COMPONENT>
<COMPONENT NAME="Rudder Control" TYPE="AEROSURFACE_SCALE">
INPUT fcs/rudder-sum
MIN -0.35
MAX 0.35
OUTPUT fcs/rudder-pos-rad
</COMPONENT>
The component called "Yaw SAS Rate" is what one would call a yaw damper. It's
job is to provide an extra "Yaw_moment_due_to_yaw_rate" for airplanes that
are defficient in this quality. The component looks at beta rate (in JSBSim
it is called "velocities/r-aero-rad_sec").
The component called "Yaw SAS Beta" is what you are looking for. It could be
called an "auto-coordinator", because it is based on the beta angle. In this
case I have the component turned off. To turn the component on you simply
change the scheduling gains from zero. For instance, look at the yaw damper.
At and below 30 knots the yaw damper gain is zero (off). Between 30 knots
and 60 knots the gain is interpolated from zero to 5.0. Between 60 knots and
220 knots the gain is interpolated from 5.0 to 3.0. I recommend this
component be turned off at low speeds, otherwise it will fight a crosswind
even when the airplane is stationary.
The outputs of the yaw damper and auto-coordinator are summed, then limited to
%20 rudder in order to prevent it from overpowering the pilot's input.
This is just one way of building a yaw SAS.
Dave
--
****************************
David Culp
davidculp2[at]comcast.net
****************************
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