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4 GY401 F
UNCTIONS
Monitor LED
Indicates the operating status of the GY401. The display
contents are shown below.
Gyro Operation Direction Switch (DIR)
Switches the gyro control direction. It must be
switched according to the direction of rotation of
the main rotor and the direction of the rudder
linkage. If the rudder servo moves in the cancel-
lation direction when the nose of the helicopter
moves, the operating directions are good.
•If you try to fly a model with a clockwise rotation
rotor when the gyro operation direction is reversed,
the nose will turn to the left and result in a danger-
ous situation.
DS Mode Switch (DS)
Digital servo (DS) mode switch. The ON position is
the high-speed output mode for digital servo only.
When using a normal servo, always set this switch to
the OFF position. If it is set to the ON position, the
servo will be destroyed.
Relationship between transmitter sensitivity
adjustment and gyro operation sensitivity
and operation mode
The gyro sensitivity becomes zero when the transmitter sensitivity
switching signal is in the neutral position. The sensitivity can be
adjusted over the deflection width of the signal by operating in the
AVCS mode at the + side and in the normal gyro mode at the - side
of the neutral position.
When the transmitter has a gyro sensitivity switching function
(T9ZHwc Series, T8UHPS, etc.), and the transmitter GYRO setup
screen sensitivity setting is 50%, the GY401 gyro sensitivity be-
comes zero. When the setting exceeds 50%, the gyro enters the
AVCS mode and the sensitivity becomes 100% at 100%. At set-
tings lower than 50%, the gyro enters the normal gyro mode and
the sensitivity becomes 100% at 0%.
When sensitivity setting is performed by transmitter switch channel,
AVCS mode and normal gyro mode switching is performed by
switch position. The sensitivity of each mode is set by the rudder
angle adjustment function (ATV, AFR, etc.) of the respective
channel. When the ATV or AFR set value is 90%, the gyro sensitiv-
ity becomes 100%.
Transmitter with gyro sensitivity switching function
(T9Zwc, FF8S, etc.)
(Example of sensitivity setting with T8UHPS)
Relationship
Idle up
between transmitter set value
switch
and gyro sensitivity
(Transmitter setup screen)
NORM
Transmitter
set value
100%
AVCS mode
80%
75%
IDL1
50%
AVCS mode
60%
25%
IDL2
0%
Normal mode
60%
The figure above is an example of use of the gyro sensitivity switching
function (GYRO) to switch hovering (AVCS mode), idle up 1 (AVCS
mode) and idle up 2 (normal gyro mode) by SW-E and to set the gyro
sensitivity to 80%, 60%, and 60%, respectively.
[Setting procedure]
1. Call the transmitter advance menu GYRO setup screen.
2. Press the cursor key and display the switch selection screen. Press the
data key and select SW-E.
3. Press the cursor key and display the hovering sensitivity NORM screen
and set hovering sensitivity to 90%.
4. Press the cursor key and display the IDL1 screen and set the IDL1
sensitivity to 80%.
5. Press the cursor key and display the IDL2 screen and set the IDL2
sensitivity to 20%.
* The values above are the values when the sensitivity channel reverse
function is normal.
Control Delay Trimmer (DELAY)
Rudder control signal operation speed trimmer. Conversely, to stop hunting, charac-
teristics can be improved by adjusting the delay. When the trimmer is turned clock-
wise, the delay increases.
•When using high-speed servos such as a digital servo, set the delay trimmer to "0".
Limit Trimmer (LIMIT)
Sets the maximum travel of the rudder servo. Move the rudder stick to the
left and right and adjust the limit trimmer so that the servo operating angle
do not strike the linkage. During flight, the servo will not operate beyond
this angle and the linkage is protected. When the trimmer is turned clock-
wise, the servo operating angle increases
Sensitivity Switching Connector
Gyro sensitivity switching signal input connector.
Connect to the receiver sensitivity switching
channel (normally CH5). This connector is also
simultaneously used to switch between the AVCS
and normal operation modes. Since this connector
is a single wire signal line, do not pull it force-
fully.
Rudder Input Connector
Connects to the receiver rudder channel (CH4)
output connector.
Rudder Servo Connector
Connects the rudder servo.
(Monitor LED display)
LED display
Gyro operation state
Rapid flash
Displayed while data is being initialized at power ON.
Steady light
Indicates that the gyro is operating in the AVCS mode.
Off
Indicates that the power is OFF, or the gyro is operating
in the normal gyro mode.
Slow flash
Displayed when there are no rudder operation signal being
input from the transmitter. At this time, the rudder servo
does not operate.
Intermittent flash Alarm display when the power was turned on in the
normal gyro mode. For the rudder neutral signal to be
read correctly, set the transmitter to the AVCS mode
and turn on the gyro power again.
Double flash
Displayed when the rudder signal from the transmitter
in the AVCS mode is different from the neutral signal
memorized in the gyro. Also flashes when the rudder stick
was operated.
Single flash
Displayed only when the transmitter sensitivity switch is
rapidly switched between the normal and AVCS positions
at least 3 times, then returned to the AVCS position and
the transmitter rudder stick was rapidly moved to the left
and right at least 3 times. After this display goes off, the
rudder is in the neutral position.
Transmitter with ATV function
(T9Z, FF8, FF7S, FF6S, etc.)
(Example of sensitivity setting with T6XHS)
Sensitivity
switch
between transmitter set value
(CH5)
and gyro sensitivity
(Transmitter setup screen)
(Forward
Gyro
Transmitter
position)
sensitivity
set value
100%
AVCS mode
80%
50%
0%
Cannot be set
(Backward
in this range.
position)
50%
Normal mode
60%
100%
The figure above uses the CH5 ATV function and is an example of switch-
ing to hovering (AVCS mode) in the switch forward position and to idle up
(normal gyro mode) in the backward position) and setting the sensitivity of
each mode to 80% and 60%, respectively.
[Setting procedure]
1. Call the CH5 ATV screen.
2. Pull the CH5 switch forward and set the ATV rate to 72%.
3. Push the CH5 switch backward and set the ATV rate to 54%.
However, when sensitivity switching is performed with the CH5 switch, the
AVCS mode cannot be used at both hovering and idle up. The AVCS
mode and normal gyro mode are switched by switch position.
*The values above are the values when the sensitivity setting channel
reverse function is normal.
5 U
Mount and adjust the GY401 as described
SE
below.
Use the miniature screwdriver supplied and
operate the GY401 switches and trimmers so
that excessive force is not applied.
Installing to fuselage
(1) Gyro installation
GY401
Fuselage gyro bed
Always install the GY401 using the
double-sided sponge tape supplied.
(2) Gyro connection
Connect to rudder servo.
(3) Servo selection
When using a digital servo (S9253, S9250,
S9450, etc.) as the rudder servo, set the DS
switch to the ON position.
(4) Rudder servo linkage check
Set the transmitter gyro sensitivity switch to the AVCS position and
turn on the transmitter power, then turn on the gyro power (shared with
receiver). Since the GY401 initializes the data when the power is
turned on, set the rudder stick to the neutral position and do not move
the helicopter for approximately 3 seconds.
If the monitor LED lights, the gyro is operating in the AVCS mode.
When the power is turned on in the normal mode, the monitor LED
will display an alarm by flashing intermittently. Set the sensitivity
switch to the AVCS position and turn on the gyro power again.
Next, switch the transmitter switch to the normal gyro mode position
and check the linkage.
In the rudder neutral position, connect the linkage
Perpendicular
so that the servo horn and control wire are
perpendicular.
Relationship
Move the rudder stick to the left and right, and check the direction of
operation of the tail rotor. If the tail rotor rotates in the wrong direction,
adjust the direction with the transmitter reverse function.
Gyro
sensitivity
90%
100%
(5) Gyro sensitivity setting criteria
The gyro sensitivity differs with the servos used and the fuselage.
45%
50%
Generally, the faster the servo operating speed, the higher the gyro
sensitivity. Also, when the main rotor speed is raised, the tail sensitivity
10%
of the helicopter itself rises and the gyro sensitivity at idle up must be
0%
0%
10%
dropped below the sensitivity when hovering. This tendency is greater
with 60 class helicopters than with 30 class helicopters.
45%
50%
Start sensitivity adjustment with a gyro sensitivity of 70 ~ 80% when
hovering and 60 ~ 70% during flight as the criteria and search for the
90%
100%
best sensitivity for the helicopter used.
(6) Gyro operation direction check
If the rudder servo moves to the left when the nose of the helicopter
moves to the right, the gyro direction is correct.
If the rudder servo operates in the reverse direc-
tion, switch the switch.
Since the switches are close to each other,
switch them carefully.
When the rotor rotates clockwise, if you try to fly while the
gyro direction is wrong, the nose will rotate to the left and
result in a dangerous situation.
(7) Limit setting
Move the rudder stick to the left and right and adjust
the limit trimmer so that the servo operating angle
does not strike the linkage. During flight, the servo will
not operate beyond this limit and the linkage will be
protected. If the setting is too low, the gyro perfor-
mance will be affected.
Flight adjustment
In the AVCS mode, the gyro automatically adjusts the rudder neutral
position so that mechanical rudder neutral position changes are un-
known. When the rudder neutral position changes substantially, a left
and right rudder error is generated and gyro performance may drop.
When making your first flight and when reconnecting the linkage, set the
mechanical rudder neutral position by first flying in the normal mode and
then flying in the AVCS mode.
(Rudder neutral position adjustment)
Install the gyro so that the bottom of the
gyro is perpendicular to the direction of
(1) Set transmitter revolution mixing (pitch->rudder) to 0% or OFF.
the main rotor shaft axis. Changes of
this axis are also reflected in the roll and
(2) Set the transmitter gyro sensitivity switch to the AVCS position. First, turn on
pitch directions.
the transmitter power, then turn on the gyro power (shared with receiver). Since
the GY401 initializes the data when the power is turned on, set the rudder stick
When using the GY401 with a
to the neutral position and do not move the helicopter for approximately 3
motor helicopter, install the
seconds.
gyro at least 10cm from the
If the monitor LED lights, the gyro is operating in the AVCS mode.
drive motor.
When the power is turned on in the normal mode, the monitor LED will
display an alarm by flashing intermittently. At this time, set the sensitiv-
ity switch to the AVCS position and turn on the gyro power again.
Connect to receiver sensitivity
switching channel (CH5).
(3) Switch the transmitter gyro sensitivity switch to the normal position. At this time,
the monitor LED goes off. Lift off the helicopter and hover and adjust the rudder
Connect to receiver rudder
neutral position with the transmitter trim lever.
channel (CH4).
Large rudder neutral position deviation may require readjustment of
the fuselage linkage.
(4) Set the gyro sensitivity to the point just before the helicopter tail begins to hunt.
For a digital servo,
switch to ON position.
When the helicopter tail hunts, set the gyro sensitivity to a lower value.
When adjusting the gyro sensitivity, increase and decrease the sensi-
tivity gradually while checking.
(For other information, see "One point advise".)
This completes mechanical neutral position adjustment. Land the helicopter and
set the gyro to the AVCS mode. When flying, the power must always be turned
on in the AVCS mode and the rudder neutral position read each time.
(AVCS side adjustment)
(5) Set the rudder trim position for all flight conditions which use the AVCS mode to
the trim position flight-adjusted in the normal mode.
When using common trim in both the AVCS and normal modes, this
operation is unnecessary.
When the power is turned on thereafter, the gyro reads this trim position as
the rudder neutral position.
(6) Set the rudder stick to the neutral position, switch the transmitter sensitivity
switch between the AVCS and normal modes at least 3 times at an interval of 1
second or less, then set the switch to the AVCS position.
This operation memorizes the AVCS side neutral data to the gyro. At
Tail control wire
this time, the monitor LED flashes once. The neutral data is also
memorized by setting the transmitter sensitivity switch to the AVCS
Set the servo horn length based on the
position and turning on the gyro power again.
model manufacturer's instructions.
Switch the transmitter flight mode to hovering, idle up and all other flight condi-
tions used and confirm that the monitor LED lights.
If the LED flashes twice, the rudder trim of that flight condition has
shifted. Readjust the rudder trim.
(7) Hover and fly in the AVCS mode and set the gyro sensitivity to the point just
before hunting begins. The AVCS mode sensitivity is slightly lower than in the
normal mode.
When hunting occurs, lower the sensitivity. When adjusting the sensi-
tivity, proceed slowly while checking.
(For other information, see "One point advise".)
(8) Adjust the rudder steering effect using the transmitter rudder angle adjustment
functions (AFR, D/R, etc.).
(9) When hunting occurs at pirouette stop, increase the delay with the delay trim-
mer. This hunting occurs easily when the servo operation speed is slow. If the
delay is increased too much, the tail will drift when stopping and rudder operation
will become sluggish. Adjust the delay to a suitable value.
With a high-speed servo such as the S9253,
set the delay trimmer to "0".
(10) Switch to the AVCS or normal mode, whichever your prefer. In the AVCS
mode, the tail neutral position is forcefully restrained even when external distur-
bances such as cross winds occur. On the other hand, in flight, the weathervane
effect cannot be expected like in the normal mode. When the tail turns, that
attitude is maintained. Operation that sets the rudder to a suitable position is
required.
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