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Servo Travel:
Amount of servo motion on either side of centre (endpoints).
Servo Trims and Reversing:
Sets the tail servo’s centre point and direction.
Setup Servo with Rudder Stick:
This
button starts a wizard that allows you to
easily set up the tail servo’s centre point and travel. Just press the button and
follow the prompts.
19.1 Advanced Tuning Options
The helicopter can be tuned in a more detailed way using the advanced user
settings of the SK720 setup software. To enable the advanced settings, select
Advanced User Settings
in the
Options
menu.
Cyclic Tuning Tabs
The two
Cyclic
tabs are found in the
Offline Setup Values
region of the main
SK720 setup software window as shown in Figure 19.6 below. The tab that is
currently active is denoted by the blue bar. Switch the active tab using your
transmitter’s gain/bank channel.
Figure 19.6 – SK720 Setup Software
Cyclic
Tabs
Control Rates:
The roll or pitch rate of the helicopter at maximum cyclic stick
deflection. This setting has a similar effect to changing the area of a flybar’s
paddles.
Bell Gain:
Amount of motion of the swashplate in response to cyclic stick
deflection, normally auto-tuned by the SK720. To manually adjust the Bell
gains: While in a hover, pitch the helicopter sharply nose down, centre the
cyclic stick and then do the same nose-up. If the helicopter is slow to
respond, turn the Bell gain up a small amount. If the helicopter snaps back a
bit and oscillates after it stops, turn the Bell gain down a small amount.
Repeat until you get the best balance. For sport flyers, the Bell gain needs to
be only roughly correct.
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Hiller Gains:
This gain’s effect is similar to “heading hold” on a yaw gyro.
Higher Hiller Gain is equivalent to increasing the weight of a flybar’s
paddles and adds stability and resistance to wind gusts. This feature gives the
heli a “locked-in” feel. Slop-free linkages, rigid rotor head mechanics,
stronger servos and stiff blades allow higher gains here. When hiller gain is
too high, the heli will oscillate at 1-2 cycles per second.
Damping Gains:
Roll and pitch rate motion damping. Higher gain is equivalent
to having heavier rotor blades or a higher head speed and helps with stability
during forward flight and piros. Fast digital servos allow higher gain here.
The default gains are best for analog servos but can be set to 20/16 for digital
servos. When damping gain is too high, the heli will oscillate quickly.
Tail Drag Compensation:
All helicopters have uneven drag on their airframes,
especially the tail. For better piros and tick-tocks, this feature lets you trim
out the effect of tail boom drag during hard collective pitch use.
Lock Cyclic Gain:
This allows you to lock in the value for overall cyclic gain,
which the gyro uses to scale the Hiller and Damping gains. The gyro will
then only pay attention to the gain channel for selecting this bank, but it will
ignore the % value the channel has.
Cyclic Gain Channel Also Scales Damping Gain:
If enabled, then the Cyclic
gain channel will also adjust the damping gains by the ratio of the Cyclic
Gain input vs. the elevator Hiller gain in the setup.
For example, if Elevator Hiller gain is 50% on a Cyclic gains tab, the Cyclic
Gain channel is set to 100% and Damping is set to 20% for elevator on the
Cyclic gains tab, then the resulting damping gain would be 100/50*20 =
40%.
This option can make it easier to re-tune the gyro when mechanical changes
are made that will affect the gains, such as to cyclic pitch or head speed.
Self Tune Bell Gains:
If enabled, the SK720 will auto-tune the Bell Gains in
flight and save the new values in the setup a few seconds after it lands. To
lock in the values once auto tuning is complete, disable this checkbox.
Note: If you have auto-bell tuning on and it sets the bell gain above 85%,
then the control rates are higher than your helicopter is capable of
