FUTABA GY501 Instruction Manual page 26

B U
EFORE SE
27
Differences in rudder control method
The following describes the differences between conventional gyro
and AVCS gyro rudder control.
The conventional gyro sends the rudder control signals from the
transmitter to the rudder servo and starts to move the tail. When the
tail moves, the gyro detects this movement and generates a signal to
stop it. If the tail continues to move even in this state, a rudder
control signal larger than the signal from the gyro must be applied
from the transmitter. That is, the difference between the rudder
control signal from the transmitter and the control signal that at-
tempts to stop this from the gyro becomes the actual amount of
movement of the tail. Ordinarily, the rudder control signal is ampli-
fied several times over by the gyro amp and is balanced with the
gyro control signal so that the transmitter can be used at the normal
steering angle.
The AVCS system uses a different rudder control method. As
described in the preceding section, it has additional functions that
"attempt to return movement by external force to the original
position" and that generate an angular velocity proportional to the
rudder control signal. That is, it functionally controls the speed of
rotation of the tail. The original AVCS (Angular Vector Control
System) came from this. In the AVCS mode, when the transmitter
rudder stick is moved when the helicopter was stopped, the rudder
servo controls operation until the tail reaches the specified rotational
speed. Trim deviation of the rudder control signal also becomes a
signal that causes the tail to turn so that even a little trim deviation
causes the tail to move. Therefore, the rudder trim is made the same
in all flight states and must match the neutral reference signal at the
gyro. The method of reading the rudder neutral signal at the gyro
will be described separately. Since the rudder mixing signals from
the transmitter also become a tail rotation signal, all the rudder
mixing functions must be disabled.