Futaba Gy401 Gyro How-to
using the Futaba 8U Super

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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 4 on the receiver. Then plug the 1 wire connector into channel 5 - make sure the yellow wire is on the signal side. The signal side will be opposite of the black (ground) side.
  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. This gyro initializes fast, only about 3 or 4 seconds. Also when using a digital servo like the Futaba 9253 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 In this setup we will configure switch E (the flight mode switch) to control the gyro mode.
reverse settings In the REVERS menu set RUD to REV and GYR to NORM
zero center position In the radio go to the 'SUBTRM' menu and set the rudder to 0 and gyro to 0.
trim step rate Go to 'TRIM' press the right arrow key until you get to TRM-RU and use the +- keys to set the value to 1.
set limits to 100% Go to 'ATV' menu and use the right arrow to select 'ATV-RU'. Hold the rudder stick to the left and set the value to 100%, hold the rudder stick to the right and set it to 100%. Go to 'ATV-GY' and make sure both sides are also set to 100%.
dual rates to 100% Go to D/R menu and set the rudder to 100%.
set the gyro gain Go to GYRO in the Advanced menu and look under the word 'GYRO', if it does not say 'on' then press the + key to turn it on. Press the right arrow, then set the gain you want for Normal flight mode. I would start off around 100. Press the right arrow and you will see IDL1, set the gain value to 0 (for now, later this will go to 100). Press the right arrow and use the +- keys to select SW-E. The concept is to use values below 50 and above 50 to not only choose between HH or Normal, but also to adjust the gain in each mode. For example if your value is 80, that would put the gyro in normal mode with 60% gain. If you set the other side to 20 then it would make the gyro operate in heading hold at 60% gain. The further from 50 (high or low) the higher the gain will be. Going below 50 tells the gyro to use standard rate mode and going above 50 tells the gyro to use heading hold mode.
set to normal mode While in flight mode 1, move the rudder stick to the right, then back to center, if the servo does the same then you are in standard rate mode. If the servo moves to one direction but does not move back to center then you are in heading hold mode. If it does this, then reverse the value in the REVERS menu. In this menu select the gyro channel and make it opposite of whatever it is set to now. In most cases this should be right when set to NORM.
servo direction Check the servo direction. Move the rudder stick to the right and watch the servo arm. It should move the servo clockwise which thereby should pull the rudder control link forward. This will make the nose of the helicopter rotate to the right (if you assembled the hub the right way). If not, then go to the rudder channel in the REVERS menu on your radio and change the direction.
gyro direction Rotate the helicopter so the nose goes to the left and watch the rudder servo. The servo needs to rotate clockwise. If not, then flip the reverse switch located on the top of the gyro sensor box.

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, turn on the radio (in normal flight mode) and receiver. Wait until the gyro initializes. Flip to flight mode 1 so the gyro is in standard rate mode. Set the rudder servo arm so that it points straight up with the rudder stick and rudder trim centered. 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 with the collective stick centered up/down and left/right (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 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 arm and you have the 4.5mm at the tail slider, then you can move to the next step.
  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 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. Note: The servo will only move during the first 75% of stick movement. This does not mean something is wrong, this is the way it was designed. Now hold the link over the servo arm to see which hole it will align with and install the ball in that hole. Mine worked out to use the hole that is 11mm from the center. You can use the limit pot to fine tune this adjustment so that the rudder does not try to pull the tail link further then it should and have binding. Now you can snap the link on the ball.
Notes about this radio setup The above configuration currently uses the flight mode switch to select non heading hold while in flight mode 1. With the GY401 there is very little reason to use standard rate mode. I leave mine in HH all the time. On other gyros I would prefer to have Normal flight mode use standard rate because the HH mode would have a kinda jerky non-fluid motion when doing ground maneuvers such as slow piroueting circles. With the GY401 I have found it is smooth all the time in HH mode so I just leave it there. So we need to get flight mode 1 back to a HH mode. Go to the GYRO menu and use the right arrow to get to IDL1, then set it to 100.
Flying adjustments To get the tail to move faster or slower, adjust the rudder channel travel. Go to the 'ATV' menu and set 'RU' left and right. 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 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 you the tail wags in a hover then decrease the gain. Go to the 'GYRO' menu and decrease the value.
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 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 then increase the value of the delay (pot on top of the gyro).