Futaba GY401 w/ RD8000
Gyro How-to

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Mount the Gyro on the back plate behind the main shaft. Yes, the tape that comes with the gyro is not very cushiony, but that's the way it needs to be. The cushioning is done inside the gyro. The tape works great, use it. As you can see in the picture to the left, I mounted it with the cords coming out toward the back of the helicopter.
Make the connections just as shown in the manual (picture to the left comes from the manual). This is very simple, nothing special here, just connect the rudder servo to the female connector. That leaves two other connectors, one with 3 wires and the other with 1 wire. Connect the one with 3 to the rudder channel of the receiver (channel 4). Then plug the 1 wire connector into the gear channel (channel 5) - make sure the yellow wire is on the signal side. The signal side will be opposite of the black (ground) side. Note: To get the two Futaba connectors into your Airtronics Z type receiver you will have to trim the flat piece that sticks out on the side. Use an exacto knife to shave this off.
  Before we continue it helps to understand the characteristics of this gyro. You have to start up this gyro in heading hold mode. Also as with all heading hold gyros you have to wait for the gyro to initialize after power up before you can move the helicopter. The gyro initializes fast, only about 3 or 4 seconds. Also when using a digital servo like the Futaba 9253/9254 you need to flip the tiny switch on top of the gyro to "on", the swith is labeled "DS".
Common misconception of all heading hold gyros Another thing that a lot of people don't understand is that the rudder travel adjust (ATV's / EPA's) does not adjust how far the servo moves. You cannot use this to prevent linkage binding. This adjustment only effects how fast the tail moves (your pirouette rate).
radio setup This radio has a gyro switch on the top/front/left that you can use to toggle between two different settings for each flight mode. So between Normal, 1, 2, and 3(hold) that is eight different settings! Yes that is a lot and no it is unlikely you will use all of that unless you use this gyro menu for a governor/rpm limiter (and put the gyro on channel 7 or 8).

Go to the 'G' menu and down to 'GYR'. Use the flight mode button to set 'N'. Is the value shown positive or negative? If it is negative then flip the gyro switch. Now that the number is positive set it to +90. Press the flight mode button to get to '1', '2', and '3' and set all of them to +90. Now flip the gyro switch and set 'N', '1', '2', and '3' all to -90. When you flip the gyro switch once more that should show +90 again. Leave it here in the positive range for the next steps.

Center trim If you have 'DTM' in the 'etc' menu set to 'ACT' then make sure the rudder trim is 0 for all flight modes. Go to 'RU' then down to 'TRM' and set it to 0, if 'DTM' is on then use the flight mode button to change to each mode and set all modes to 0.
zero center position Go to 'Ru' and down to 'CNT' and also set it to 0.
set limits to 100% Go to 'Ru' and down to 'EPA'. Move the rudder stick left and set it to 90% then move the stick to the right and set the value to 100%.
dual rates to 100% Go to 'Ru' and down to 'D/R' and use the f.mode button to set all flight modes to 100%
Turn off Revolution mixing Go to 'RU' and down to 'RV.H', use the flight mode button to toggle betwen N, 1, and 2 and set all to 0. Do the same for 'RV.M' and 'RV.L'
  First disconnect the rudder link from the servo. Turn on the receiver. Wait 4 seconds for the gyro to initialize. It may or may not initialize correctly depending on where the gyro channel reverse setting is set in the radio. Remember the gyro has to start up in HH (Heading Hold) mode. Continue with the next step to determine if it's in the right mode.
set to normal mode Move the rudder stick to the right, then back to center, if the rudder servo does the same then you are in normal mode which is wrong. If the servo moves to one direction but does not move back to center then you are in heading hold mode which is right. If you ended up in normal mode then go to the 'G' menu in the radio and down to 'REV' and change the setting. If it's set to 'NOR' then change it to 'REV' or vise versa. Then turn off the receiver and then back on and let the gyro initialize in heading hold mode.
  Now that you have the gyro initialized correctly in HH mode you need to set it to non-HH mode while you do the next few steps. So flip the gyro switch on the top/front/left of the radio (do not turn the receiver off). We will change this to HH after we get everything setup but for now leave it in standard rate mode.
servo direction Check the servo direction. Move the rudder stick to the right and watch the servo arm. It should pull the rudder control link forward. This will make the nose of the helicopter rotate to the right. If not, then go to 'RU' and down to 'REV' and change it.
gyro direction Rotate the helicopter so the nose goes to the left and watch the rudder servo. The servo needs to pull the rudder control link forward. If not, then flip the reverse switch located on the top of the gyro.

With the rudder link disconnected from the servo. The first thing to do is make the link slide as free as possible. Adjust the guides to acheive the least resistance. I added a slight bent to the front section of the rod as you can see if you click on the photo to the left. I did this so as to stop the resistance the rod had on the first frame guide due to being pulled down to the servo. I also used a JR Ball link resizing tool to remove unecessary resistance from the ball links. Once you get the link as free from resistance as you can. You need to take off the rudder servo arm and install/move the ball to a position that is about 13mm from the center. Next set the rudder servo arm so that it points straight up. The best position for tail centering is to adjust the rudder link so that you have 4.5mm between the pitch slider and the tail rotor casing (see the picture to the left). Another way to find center other then measuring 4.5mm is to visually align the control arm to be parallel with the tail shaft. Check that the front link is centered with the ball on the servo arm. If it's not, turn the link clockwise to move it toward the back or counter clockwise to move it forward. Once the center of the ball link matches with the center of the ball and you have the 4.5mm at the tail slider, then you can move to the next step.
Set to Heading hold mode In a previous step you set the gyro to standard rate mode by flipping the gyro switch. Now you need to reverse it again so the gyro is back in heading hold mode.
Set Limit and Delay First make sure the 'Limit' on the top of the gyro to it's max (140), while you're adjusting that go ahead and make sure the 'Delay' is set to 0 if you are using the 9253 or 9254 servo, otherwise start around 30 and later experiment to find the best value for the servo you use.
Hold the tail rotor stick full right and pull the control rod all the way forward. Pull the link as far forward as it can go then adjust the 'Limit' control on the top of the gyro so that the ball on the servo arm centers with the link. Once you are finished you can snap the link on the ball.
Flying adjustments To get the tail to move faster or slower, adjust the rudder channel travel. Go to 'RU' on the menu and down to 'EPA'. Adjust both left and right stick positions. A higher value will make the heli pirouette faster and a lower value will make the tail slower.
Also if you are using a servo other then the 9253/9254 then you may need to adjust the Delay pot on top of the gyro to stop the tail from wagging after a quick stop.
If the tail wags in a hover then decrease the gain. Go to the 'G' menu and down to 'GYR'. Decrease the value in each flight mode.
Symptom Cause
Gain values have to be set low to stop any tail wagging. 1. The helicopter is out of balance. Vibration is the cause of low gain settings. Check the blades, check for bent main shaft, spindle shaft, tail shaft, out of balance tail blades, etc.
2. I found that a sticky clutch caused me to have to turn down my gain by 20%. Check the
engine/start shaft alignment and look for a broke shoe.
3. The ball on the rudder servo is too far away from the center.
HH doesn't hold good 1. The RPM's should be 1850 to 1950 for 3D flight. It's also important that your engine is running good. If your engine loads up a lot then you won't be able to keep a consistent RPM. Remember that a few hundred rpm drop on the head is several hundred rpm drop on the tail.
Tail wags only right after a pirouette, or anytime I move the tail then stop. If you are using the 9253/9254 servo then you probably have some resistance in your tail control rod. Make sure the guides are aligned for least resistance. Also keep your tail shaft oiled. If it is dry and tacky this will cause the problem.
If using a servo other then the 9253/9254 then increase the value of the delay (pot on top of the gyro).