Skookum SK360 User manual

Throw out your 1940’s-technology mechanical

flybar, and replace it with a Digital Flybar.

Lightening-quick 3D and solid hovering in wind, with

a less complex, lighter rotorhead that gives you

more power or longer flight times!

SK360 Digital

Flybar

User Manual and Setup Guide

Rev 1.10 SK360 User Manual & Setup Guide

Table of Contents

1 Intro ...............................................................................3

2 Package Contents ........................................................3

3 Safety.............................................................................4

4 Mounting the Gyro........................................................4

5 Helicopter Airframe Setup ...........................................5

6 How to Check Cyclic Pitch & Phasing........................7

7 Connections..................................................................9

8 Modes, Indicators, and Power-Up.............................10

9 Gyro Setup Using the USB Interface ........................11

10 After Setup: Final Check!...........................................13

11 Flight with the SK360 Gyro........................................13

12 Basic Tuning...............................................................14

13 Remote Bank Switching and Hiller Gain ..................15

14 USB Interface Software Reference............................16

15 Advanced Tuning Options.........................................19

16 Tuning Troubleshooting Guide.................................21

Appendix A: Specifications..................................................23

Appendix B: Firmware Upgrades.........................................23

Appendix C: Warranty and Technical Support...................24

1 Intro

The SK360 Digital Flybar is a high performance, compact, and lightweight pitch

and roll stabilizer for model helicopters. Its function is to replace the traditional

flybar (stabilizer bar) and its association linkages, while saving power, increasing

flight times, and reducing repair costs. Features include:

Control Options:

Control over the Bell and Hiller ratio (direct vs. stabilized control)

Control over roll and pitch rates in-software

Control feel is adjustable in software, on the gyro case, or by remote bank

switching

Optional remote gain

Swashplate Options:

Suitable for 120, 135/140, and 90 degree eCCPM, as well as mCCPM

swashplates

Mixing In-Gyro, for higher precision

Swash Ring anti-binding algorithm

Phase Trim adjustable to +-90

Servo Options:

Works with digital or analog servos

Synchronous with receiver’s PWM frames for minimal lag

Groups swash servo PWM pulses for low swash motion error

Swash servo rate-equalizing prevents uncommanded pitch during

aggressive maneuvers

2 Package Contents

Your gyro package should include:

SK360 Gyro unit

Four strips of 3M-4408tm mounting tape

USB Interface with jumper

USB Extension Cable

CD with Interface Software

Note: If your computer can’t read mini-CDs, visit our website at:

www.skookumrobotics.com/support.html

to download the latest version of the setup software (you will not need to

update the firmware).

3 Safety

An R/C Helicopter is not a toy, and can cause serious injury to people or damage to

property. Use of this gyro places a flight control computer (the gyro unit) between

the radio receiver and the servos that drive the swash plate. If the gyro unit is

mistuned or set up incorrectly, loss of control of the helicopter may result. See

Appendix C for warranty information.

Please keep bystanders clear of the flight area at all times. Be sure to test fly away

from spectators, especially when flying the helicopter after any change in the gyro’s

setup or tuning, and keep yourself at a safe distance.

4 Mounting the Gyro

The front side of the gyro is marked on its case. The gyro unit can be mounted

upside down, backwards, or sideways, but it must be level, and have its sides

aligned as accurately as possible with the fore-aft axis of the helicopter.

Misalignments of even a few degrees (2mm or 1/16” difference between the front

and back edges of the case) may cause problems with tuning the gyro. The gyro

should also be as far as possible from any heat sources, and at least 10cm away from

Xtremelinktm receivers. The SK360 label must face up or down.

For vibration resistance, mounting tape with good damping must be used, such as

the 3M-4408tm tape included. The gyro’s case should not directly contact any hard

surfaces of the helicopter’s frame, and if a safety strap is used across the top of the

gyro, it should be padded slightly. Cables connected to the gyro should have some

slack near the gyro’s case.

Before mounting the gyro clean its base and the

mounting site with isopropyl alcohol. Then use

two pieces of the supplied 3M mounting tape on

the base of the gyro, as shown. If you use a

pad/metal plate/pad mounting for a nitro heli, be

careful that the stack is not too thick, as this might

result in resonance.

5 Helicopter Airframe Setup

Good mechanical setup is critical to the gyro performing correctly. Please read this

section fully.

The gyro should not be used in addition to a flybar, as the results could be

unpredictable. It is intended for use where the swashplate alone drives blade pitch.

Blades:

Flat bottomed rotor blades are not recommended. They have a pitch-down moment

about their axis of rotation that could put heavy loads on the swashplate servos. The

ideal rotor blades will have a symmetrical airfoil, be torsionally stiff but a bit

flexible spanwise, and balanced both spanwise and chordwise.

Servos:

The best performance will be achieved if the swashplate servo’s full normal range of

movement is used. For good “3D” performance, you will need servos that are fast,

and if possible digital. For analog servos, check their specification, and drive them

at 6v (if they are rated for it). Stronger, faster servos will let you use higher damping

gains (see Section 15), which is important for maneuvers such as piro-flips.

Try to have 90-degree angles between servo and blade grip arms and linkage rods,

for even movement. The gyro’s USB setup interface will allow fine-tuning of servo

centers to achieve this.

Rotorhead:

When setting up the mechanics originally designed for helis with a flybar, just

removing the flybar but keeping normal servo arm length will likely give too much

blade pitch action. Either servo travel or servo arm length will then need to be

reduced. For example, on the Aligntm TREX, you can adapt the flybar mixing arms

as travel-reduction arms on the rotorhead, to reduce the effect of swashplate slop

and reduce servo load. This will allow higher gains, and better performance.

Some kind of anti-rotation or “follower” mechanism will be needed, to keep the top

of the swashplate from rotating relative to the blade grips.

If the swashplate is not held so the linkage to the blade grips is at 90 degrees to the

blades (for 2-bladed rotors), the phase angle will need to be set to compensate. See

the diagram below.

For initial flights, the phase angle should be adjusted so that when the blades are

lined up with the heli’s tail boom, they do not move with elevator input, but do

move with aileron input (for 2-bladed rotors). This can be set either mechanically, or

through the USB setup software.

It is important that the linkages and swash have little slop and the lowest friction

possible.

How stiff the rubber rotor head dampers are will have an effect on tuning the gyro

and flight performance. Performance will be better with the teeter damping a stiffer

than normal, but too stiff can cause vibration, which is hard on the airframe, gyros,

and servos.

Tail:

Because the axis of the tail rotor disk is lined up with the elevator axis of the heli,

it’s important that you minimize tail rotor vibration. Also, if you have a belt-driven

tail, be sure that your tail boom is electrically grounded to the heli’s frame or motor

case, to prevent static electricity buildup.

Balance:

The gyro will perform best with the CG directly under the mainshaft, or very

slightly nose heavy. This is especially important for maneuvers that use fast

collective pitch changes combined with yaw, such as piros.

6 How to Check Cyclic Pitch & Phasing

The goal of mechanical and gyro swashplate setup is to get your normal collective

blade pitch range, and a cyclic range of about +-10 degrees, which means a total

range of 20 degrees. This is important. (Cyclic pitch is blade’s pitch due to aileron

or elevator input)

The rotor blades must also have the correct phasing. This means that aileron and

elevator control input change each blade’s pitch at the correct time. For most

mechanical setups, the phase angle will not need adjusting.

While checking for good cyclic throws, phasing, and even swash motion, the

gyro must be put in setup mode, by pushing the mode switch towards the gain

dials (see Section 8).

While in setup mode, all stick motions are sent directly to the swashplate as if

stability gains were all zero (the gyro only does its mixing function). The gain dials

and gain fields in the PC software will have no effect in this mode.

To check the cyclic range and phasing:

1) Set collective pitch to zero.

2) Align a blade along the fuselage, pointing over the nose of the helicopter as in

the photo below:

3) Now try full nose-up elevator control, with aileron centered. Measure the pitch

of the blade that points over the nose.

4) If the mechanical setup is ideal, the blade should not change pitch. If it does you

will need to adjust the phase angle, either mechanically at the swashplate or

using the gyro’s USB interface. If the pitch becomes negative adjust the phasing

clockwise (+), if positive then adjust it anti-clockwise (-). Note: this will give

you normal phasing (90 degree lead); multi-bladed rotors may fly better with

some positive phase trim.

5) Try full right aileron control, with elevator control centered. The blade’s pitch

should be about -10 degrees.

6) Try full left aileron control, with elevator control centered. The blade’s pitch

should be about +10 degrees.

7) Align a blade at 90 degrees to the fuselage, pointing over the right side of the

helicopter as in the photo below:

8) Try full nose-up elevator control, with aileron control centered. Measure the

pitch of the blade that points over the right side of the helicopter. It should be

about -10 degrees.

9) Try full left nose-down elevator control, with aileron control centered. The

blade’s pitch should be about +10 degrees.

If the cyclic blade pitch range is changed, the gyro’s stability gains will need to

be changed as well. For example, increasing cyclic pitch range by 10% is the same

as increasing the stability gains by 10%.

7 Connections

The gyro normally has 3 inputs, and 4 outputs, labeled on the top of its case. Note

that the USB interface does not supply power. For the inputs from the radio

receiver, the connector mapping is:

Swash Setup Type Input 1 Input 2 Input 3

120 deg eCCPM Elevator Ch Aileron Ch Pitch Ch

135/140 degree eCCPM Elevator Ch Aileron Ch Pitch Ch

“1-servo” mCCPM Elevator Ch Aileron Ch n/a

90-deg eCCPM Elevator Ch Aileron Ch Pitch Ch

Left/Right means the heli’s left and right, looking from its tail to its nose.

The SK360 needs to receive separate aileron, elevator, and pitch inputs so set the

swash-type in your radio to “1-servo” for all swash setups. You also have the

option of using the “A4” port as a remote gain and bank-switching input. But do not

connect this port to your radio until the SK360 unit is told to use it as an input with

its setup software, or your radio receiver could be damaged (see Section 13).

For the outputs to the servos, the connector mapping is:

Swash Setup Type Servo 1 Servo 2 Servo 3 Servo 4

120, 135/140 deg eCCPM Centre Right Left n/a

“1-servo” mCCPM Elev Aile n/a n/a

90-deg eCCPM Fwd Aft Right Left

8 Modes, Indicators, and Power-Up

The two primary modes are Setup mode, and Flight mode, chosen by the position of

the small switch on the gyro’s side. Towards the gain dials is Setup mode, and

away from the dials is Flight Mode.

Note: The gyro will change from Setup to Flight mode right away, but won’t change

from Flight to Setup until you also cycle its power.

Setup mode lets you use the USB connection, and also used for mechanical setup -

control motions pass straight through, with no stabilizing action. While in this mode,

the indicator LED will slowly flash green.

In Flight mode, the LED Indicator will show solid red while it’s still initializing, and

turn solid green when it’s ready to fly. The gyro will not finish initializing unless it

is completely still. It will also not read in new values from the gain dials until it is

left still for a few seconds.

The option button is used for Firmware Updates (described in Appendix B).

WARNING: Always check before flight that the LED is solid green. If you take

off in setup mode the flight will be “very exciting”, short, and possibly also

expensive.

The LED flashing red rapidly indicates an error. There are four possible causes:

1. The cyclic stick wasn’t centered at initialization in flight mode

2. The supply voltage fell below 3.6v at some point

3. It is too hot or too cold

4. The gyro has a systems fault

If the first three causes can be ruled out, please contact technical support.

9 Gyro Setup Using the USB Interface

Step 1: Connecting

First install the USB Interface software for your SK360 gyro. Unplug the

swashplate servos the gyro for now.

Set your radio’s transmitter so Aileron, Elevator, and Pitch (Collective) are

output each on a separate channel (“Normal” or “1 Servo” swashplate

mode).

The initial setup will be easier if you use a straight-line pitch curve, and no

expo or dual rates. Later those features can be set in the transmitter as you

normally would.

Connect the gyro to the USB interface, and set the mode switch on the

gyro toward the gain dials to put it in setup mode. Turn on the heli’s

power, and start the setup software.

Check that the connection indicator in the upper left is green and says

Connected.

Step 2: Match the Gyro to Your Transmitter

In the Offline Setup Values area in the lower half of the window, click the

Swashplate tab. Then select the Swash Type that matches your heli’s

swashplate, and make sure Mixing Location is set to In Gyro.

Now click the Control tab. Center all the trims on your transmitter, and be

sure the cyclic stick is centered.

Click the Send Setup button, or press the F1 key to set the changes on the

gyro. You must SEND the setup whenever you want to test changes.

After a few seconds, check Inputs from Receiver again. The % values for

Elevator, Aileron, and Pitch should be close to zero. You can trim the

collective pitch centering on the Controls tab.

Try moving the elevator stick towards you (nose up), and look at the Pilot

Control field under Elevator. The number displayed should be close to

100% and show green. If it is negative, reverse that channel in your radio.

If it’s too low or reaches 100% much before the stick’s limit, adjust

endpoints and sub-trims for that channel in your radio.

Repeat for Aileron Pilot Control, but move the stick right (green). Then

repeat for the Pitch input, but move the stick up (green).

Step 3: Check the Gyro’s Sense Directions

Now look at the Gyro Rates fields in the Live Data area. Note: the Rate

fields only sense movement, not angle.

Pick up the heli and slowly tilt it nose-up. The Gyro Rate for Elevator

should be positive and show green. If not, click Flip Elevator Axis on the

Control tab. If the gyro rate for Aileron is high instead, click Rotate 90

Degrees on the Control tab.

Repeat for the Aileron (roll) axis, but slowly tilt the heli to the right. The

Gyro Rate for Aileron should be positive and show green.

WARNING: All the control input and sense directions in steps 2 and 3 must be

correct, otherwise your heli will instantly crash if you try to fly it.

Step 4: Swash Mixing / Servo Setup

Go to the Swashplate setup tab again, and set the Swash Mixing values

(“CCPM and Travel”) just as you would in your transmitter.

Go to the Servos tab, select the frame rate according to servo type, and

enter the speed of your servos from their specifications.

Make sure the control sticks are centered, and then plug the servos into the

gyro. Check for good motion and no binding.

NOTE: While in setup mode, the gyro will give 100% swash control to the

transmitter sticks (zero stability gains), to allow for mixing, servo travel,

and mechanical setup.

Check that the swashplate motion is correct. Note: the correct blade pitch

range for elevator or aileron input is about +-10 degrees.

If the servos don’t move in the correct directions, reverse them on the

Servos tab. If the Aileron or Elevator motion is reversed, change the sign

of their swash mixing value (ex, + to -). Try to keep swash mixing values

below 60%. If you need more motion increase the servo travels instead, for

ex. to all to 125%. This prevents unwanted interaction at max and min

collective.

Do not try to change cyclic throw using the Control tab.

Adjust the servos for a level swashplate on the Servo tab.

Step 5: Ready for Flight

Save your setup to disk, then go to Section 10 of this manual.

Final Setup Note: The expo, dual-rate, and pitch-curve features of your radio can

be used normally, as long as they do not exceed 100% travel.

10 After Setup: Final Check!

Any time you change the gyro’s setup, always do these checks:

1) Put the gyro into setup mode, with the servos connected and the swashplate

mechanically set up.

2) Try full right aileron. Check that the swashplate tilts to the right.

3) Try full up elevator (nose up). Check that the swashplate tilts back.

4) Command full up collective pitch. Check that the swashplate moves to give

maximum blade pitch.

5) Try zero collective pitch, with throttle hold active. Check that the

swashplate moves to give zero blade pitch.

6) Put the gyro into Flight mode, leave it undisturbed and wait for the LED to

turn green.

7) Pick up the helicopter, wait a few seconds, and then tilt it nose down and to

the right. The swashplate should tilt back and left.

Note: In flight mode, the swash will tilt forward slightly at full positive collective

pitch, and backward slightly at full negative pitch, to compensate for tail-drag

during fast climbs and descents.

11 Flight with the SK360 Gyro

In flight mode, the swashplate will not respond to the controls directly. Its action

will be similar to a heading-hold tail gyro. Also, after it has been static for a few

seconds, it will level the swash during spool up to ensure a stable take off.

When you land your heli, always wait at least 5 seconds after the rotor spools down

before spooling up again, so the gyro knows the helicopter is spooling up. Don't

move the cyclic stick until the heli is light on its skids to prevent confusing the gyro

when it can’t fly. If the Auto trim at Initialization feature is on, avoid using the

transmitter trims for elevator or aileron. If you do use trims, you’ll have to zero

them before every flight.

ALWAYS do these pre-flight checks:

1) The Indicator LED should be solid green (not flashing).

2) Positive collective should increase blade pitch.

3) Right aileron stick should tilt the swash for a right roll.

4) Nose-up elevator stick should tilt the swash for nose-up.

12 Basic Tuning

If you have set up your helicopter’s mechanics properly, and the cyclic throws are

correct, then tuning should be easy. Note: always let the gyro be still for a few

seconds after adjusting the gain dials, so the gyro knows to read the new settings. If

your heli is nitro-powered, you’ll need to stop the motor.

Definitions:

Bell gain adjusts how much aileron and elevator control will directly tilt

the swashplate.

Hiller gain adjusts the stability and holding ability of the gyro.

Follow these steps:

1) As a starting point, adjust the dials on the gyro to about 30% for the Bell

elevator gain, and 50% for Hiller gain.

2) Lift the helicopter off into a hover, and try some small elevator and aileron

motions. If it oscillates or does anything violent as you spool up, email

tech support for help.

3) If the helicopter doesn’t hold well in pitch or roll, or “slides” to the side,

turn the Hiller gain up a small amount. If the helicopter oscillates while

hovering, turn the Hiller gain dial down slightly. Repeat until you get the

best gain.

4) Try some forward flight. If the helicopter oscillates in roll at high speed,

turn the Hiller gain down a small amount. If it doesn’t hold well in pitch,

turn the Hiller gain up.

5) While in a hover, pitch the helicopter sharply nose down, centre the cyclic

stick, then do the same nose-up. If the helicopter is slow to start, turn the

Bell gain dial up a small amount. If the helicopter snaps back a bit and

oscillates after it stops, turn the Bell gain dial down a small amount. Repeat

until you get the best balance. For sport flyers, the Bell gain needs to be

only roughly correct.

For most users, no further tuning should be required. But if the maximum aileron

and elevator motion of the heli is not fast enough for you, or for other advanced

tuning, see Sections 15 and 16.

Good starting points for the gains can be found in the “Default”, “Scale”, or

“Basic_3D” setup files, all of which are included with the USB interface software.

13 Remote Bank Switching and Hiller Gain

If you have a seven-channel radio receiver and your swashplate only uses three

servos, you can set the fourth servo output to act as a gain input.

This allows you to switch between two banks of all the settings on the “Advanced”

tab, as well as set the Hiller gain input for each bank at your transmitter. The

concept is similar to the way tail gyros have both rate and heading-hold modes, with

the endpoints in each direction setting the gain for each mode.

To use this feature, first connect to the SK360 using the interface software. Then go

to the Control tab, and enable “Use Gain Channel Input”, then sent the changed

setup to the gyro. You must complete this step before you connect the A4 port to

your receiver, or there is a small chance your receiver could be damaged.

The A4 port is now an input, so connect it to the channel you wish to use on your

receiver. Notice that there are now two versions of the Advanced tab, so you can try

out two sets of gains at the field, or select sport vs 3D tuning.

This channel also acts as a remote version of the Hiller gain dial. Negative-side

endpoint values of more than 15% on the gain channel will select Bank 1, and

positive-side endpoint values of more than 15% will select bank two.

Also note that now the Bell” dial on the case acts as the Bell Gain dial for bank 1,

and the dial labeled “Hiller” acts as the Bell Gain dial for bank 2. To learn how the

gain channel, Bell dials, and Advanced (bank) tabs work together, click “Show

Actual Gains” on one of the Advanced tabs.

You must toggle the gain channel’s switch between banks for a change

in the remote Hiller Gain to be registered.

14 USB Interface Software Reference

To use the SK360 interface software, first install the software on your PC, and plug

in the USB interface. Then attach the jumper to the gyro, set its mode switch for

setup mode, and power it up (with the motor disabled, if you have an electric heli).

On your PC, the “Connected” indicator should turn green, and the gyro’s serial

number and firmware revision should be displayed (Note: the servos may be slightly

jittery while connected to the USB port, due to noise from your computer).

If the software will not run at all, make sure your “Windows .NET Runtime” is up

to date. Check the Microsoft website for the latest version.

On the menu bar, the File menu allows you to save or load gyro configurations

(setups), or go back to the default setup. The Connect menu allows you to send a

setup to the gyro (burning it into its memory), or fetch a setup from the gyro. Any

setup sent to the gyro will be labeled with the first 8 letters of its filename.

Live Data

This area displays constantly updated telemetry from the gyro, including the control

inputs from the receiver, and position outputs to the servos. Remember that

while in setup mode, all elevator or aileron stick motions are sent directly to the

swashplate (as if stability gains were all zero, and bell gain is 100%), to allow for

easy mechanical setup.

For Inputs and Outputs, the units displayed can be percent of full throw from the

current setup, or PWM pulse-width (microseconds). Note that the collective Pitch

display should turn green for positive (climb) pitch if the gyro is set up correctly.

Under “Gyro Internals”, the Pilot Elevator and Aileron command percentage is

given as a guide for setup. It is important that cyclic stick input for nose-up, and

for right-roll, should give positive values here. Nose-up stick and right aileron

should both show green backgrounds. These readings can also be used to test the

dead-band settings.

The elevator and aileron Gyro Rates values are in degrees per second, and show the

currently sensed motion of the gyro.

The Bell Gain and Hiller Gain dial settings are displayed here for ease of

recording values arrived at by field-testing. For each type of gain, the first

percentage is the gain for elevator, the second is the gain for aileron (they’re linked

by the ratio of elevator vs. aileron for each gain on the Advanced tab of the gyro’s

setup).

Swash Tab

Swashplate Type: Select your swashplate and mechanical mixing type. Options

are 120 eCCPM, 135/140 degree eCCPM, 90 degree mechanically mixed

(separate servos for each of elevator, aileron and pitch control), and 90 degree 3

or 4 servo eCCPM, where servos are directly connected to the swash but 90

degrees apart.

Mixing: The SK360 takes over swashplate mixing, so the inputs to the gyro are

separate channels for elevator, aileron, and pitch (collective) control. This

gives the full precision of your radio set, rather than losing half of its precision

with in-transmitter mixing. It also allows for extra mixing features normally

only available on high-end radios, such as Swash Ring and Servo Equalizing.

Elevator Cyclic: Percent of full swashplate motion at full stick deflection for

elevator cyclic. This can be a negative number, but cannot be zero.

Aileron Cyclic: Percent of full swashplate servo motion at full stick deflection for

aileron cyclic. Can be a negative number, but cannot be zero.

Collective Pitch: Percent of full swashplate servo motion at full stick deflection for

collective. This can be a negative number.

Phase Trim: Rotates the plane of cyclic action about the mainshaft, to allow

correction for gyroscopic and aerodynamic effects, and the use of 3 or 4 blade

rotor heads. For example, setting phase trim to 90 degrees would make full

stick deflection for aileron tilt the swashplate down. Note that the phase angle

depends on the rotor rpm and load.

Swash Ring: Limits motion of the swashplate to prevent binding when large

amounts of both elevator and aileron cyclic are used (i.e. assume the swashplate

is round, not square).

Servo Tab

Frame Rate: The Analog servo mode synchronizes pulses to the servos with your

receiver’s output for minimum latency. Digital uses higher frame rates than

analog servos can handle and has little latency. Do not use digital frame rates

for analog servos.

Equalize Servo Speeds: Accounts for the different radius of motion for the servos

in an eCCPM swashplate arrangement. For example, for a 120-degree swash, an

aggressive pitch motion will demand higher speed from the centre servo than

the left or right servos, so it may lag behind causing uncommanded collective

input. This feature would slow all the servos evenly to the maximum rate of the

centre servo.

Servo Speed: Take this from your servo manufacturer’s specifications. Units are in

seconds per 60 degrees of motion. This helps the gyro move the swash evenly.

This field only matters if Equalize Servo Speeds is on.

Servo Travel: Amount of servo motion on either side of centre. Servo motion

outside of its mechanical limits can cause binding and overheating. The servo

travels can be set individually to trim the swash to be level at max, zero, and

min collective pitch.

Servo Trims and Reversing: Here each servo’s center point can be set, and each

can be reversed if needed. This is the same idea as sub-trim on your transmitter.

Be careful that the servo doesn’t bind.

Control Tab

Receiver/Control Setup: Similar to the settings for the servos, but here the centers

and reversing for the inputs from the radio receiver are set. To use this section,

you must first unlock it on the Options drop-down menu. Note: Features of

your radio such as exponential or pitch curves will work normally.

Use Gain Channel Input: With this feature enabled, the gyro will use A4 port as a

bank-select and hiller-gain input. The concept is similar to the way tail gyros

have a rate/heading-hold mode, with the endpoints in each direction setting the

gain for each mode.

Auto Trim at Initialization: With this feature enabled, the gyro will use the cyclic-

stick centre it receives at initialization as neutral cyclic. If left off, the gyro will

use the exact values entered in the Control tab.

Dead Band: A dead-band can be set for the cyclic (elevator and aileron) functions,

so the heli doesn’t drift with small errors in stick centering. One percent is a

good value for most radios (note your radio’s centering may change with

temperature). For scale models, deadband can give a solid control feel while in

stationary hover.

Mounting Orientation: The motion sensing directions can be flipped or rotated 90

deg, to allow the gyro to be mounted in any orientation. After mounting, always

send the setup to the gyro, and then move the heli slowly and watch Gyro Rates

on the Live Data display to be sure nose down is negative elevator rate, and

right tilt is positive aileron rate.

15 Advanced Tuning Options

The helicopter can be tuned in a more detailed way using the settings on the

Advanced tab of the USB interface program:

Maximum Rate: The desired roll or pitch rate of the heli at maximum cyclic stick

deflection. Equivalent to the area of a flybar’s paddles. If increased, Bell gain

will also need to be increased slightly.

Bell Gain: Amount of motion of the swashplate in response to cyclic stick

deflection. Normally set by a gain dial on the gyro’s case, that dial can be

disabled to lock the bell gain to a specific value.

When the gain dial is used, it will set the elevator bell gain, but the aileron

bell gain will be a fraction of that, by the ratio set here. Example: The

Advanced Tab shows Bell gains of 20% elevator and 10% aileron, and the gain

dial is not disabled. Then if the gain dial is set to 50%, the elevator bell gain

will be 50% and the aileron bell gain will be 25%.

Hiller Gains: 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 rotorhead mechanics, stronger servos, and stiff blades allow

higher gains here.

The Hiller gain dial is used to set the elevator and aileron hiller gains in the

same manner as described above for the Bell gain dial.

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 pyros. 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. Appropriate Damping gains are normally about 1/3 as large as the Hiller

gains.

Tail Drag Compensation: All helis have uneven drag on their airframes,

especially the tail. For better piros and tick-tocks, this feature lets you trim

out the effects that has during hard collective pitch use. To use this feature,

follow these three steps:

1) Make sure your heli’s balance point is under the main shaft, or slightly

nose-heavy.

2) Check that your swash is level at min, zero, and max collective pitch while

in Setup mode. On the servo tab, first adjust the swash to be level at zero

pitch using the trims, then use the servo travels to make sure the swash is

level at min and max collective. This is needed because servos are not all

identical; the pots that measure their position can vary by 10% or more.

3) If the heli tends to nose-up when max collective is applied quickly from a

hover, subtract one from elevator tail comp. If the heli goes right, subtract

one from aileron tail comp. Add one to the fields if it noses down, or goes

left.

Hiller Decay: Causes accumulated Hiller response to decay back to neutral, to

make the gyro more forgiving of insults. If you watch a heli with a flybar in

hover, after a sharp control input you’ll see the flybar’s disk offset for a

moment, then drift back to level. This provides the same effect.

A value of 100% here can help smooth out rapid tic-tocks, piros, or other 3D

maneuvers, especially repeated ones. However, high values for Hiller Decay

will also limit the gyro’s ability to hold steady in gusty wind, or trim the heli

perfectly in hover.

Disable Gain Dials: If enabled, the gain dials on the gyro itself will have no effect.

The gains will be taken straight from those entered in the gains setup tab.

Hiller Dial Also Scales Damping Gain: If enabled, then the Hiller gain dial will

also adjust the damping gains, by the ratio of the Hiller Dial setting vs. the

elevator Hiller gain in the setup.

For example, if Elevator Hiller gain is 50% on the Advanced tab, the Hiller

Dial is set to 100%, and Damping is set to 20% for elevator on the Advanced

tab, the resulting damping gain would be 100/50*20 = 40%.

This 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.

Show Actual Gains: Brings up a table of the actual gains the SK360 will use in

flight. These gains are based on the settings on the Advanced tab, modified by

the Bell and Hiller dial’s settings. This feature can help you understand how

the gain dials and base-gains work together.

Default Gains: Resets all of the settings on the Advanced tab to those in the

Default setup file. Does not effect any settings on the other tabs.

Table of contents

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