Futaba GY401 w/ Spektrum DX7
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 (labeled 'Rudd'). Then plug the 1 wire connector into channel 5 (labeled 'Gear') - 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 Spektrum 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. This 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 For this setup we will not use the built-in gyro function. Instead we will use the GEAR switch to control the gyro mode and use the Travel Adjustment for the GEAR to control the gyro gain. Go to the system menu by holding both 'DOWN' and 'SELECT' buttons while you turn the radio on. Use the 'DOWN' button to get to [INPUT SELECT]. Press the 'SELECT' button to get to 'GEAR' and use the INCREASE button to choose 'GEAR'.
zero out anything that would effect the rudder First get in the menu ( press the 'down' and 'select' buttons simultaneously with the radio already on), press 'down' until the screen gets to [REVO MIX], and make sure the UP and DN values are zero for all flight modes (NORMAL, STNT). Use the 'clear' button to set the values to zero.
zero center position And zero out the [SUB TRIM], use the 'select' button to select 'RUDD' then the 'clear' to set the value to zero. Do the same for 'GEAR'.
Also make sure the trims are centered.
set pirouette speed Go to [TRAVEL ADJUST] menu and use the 'select' button to select 'RUDD'. Hold the rudder stick to the left and set the value to 85%, hold the rudder stick to the right and set it to 110%. This will set how fast the helicopter rotates. You may want it faster or slower so change the value appropiately. Notice that the values are different, you do not need as much to rotate the helicopter to the left because it is going 'with' the torque in that direction.
set the gyro gain Go to [TRAVEL ADJ] menu and use the 'select' button to select 'GEAR' and make sure both sides are also set to 100%. To select both sides flip the GEAR switch. One direction will set the gain value for heading hold and the other will be for standard rate. That is the difference between one value having a positive value and the other a negative value. For now set both to 100 but later you may need to adjust this down a little to keep the gyro from 'hunting'. On my gy401 that came with the 9254 servo I have found 84 is what it took.
  Next 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 position you have the GEAR switch (remember this is now the switch that will control the gyro). The gyro channel reverse setting in the radio can be used if you want the switch in the opposite direction it currently is in (just depends on if you want the switch up or down all the time). On my DX7 I have the reverse setting for GEAR set to NORM. This gives HH when the switch is up. 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 start up in HH 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 [REVERSING SW] and change the value for 'GEAR' channel. Then turn off the receiver and then back on and let the gyro initialize in heading hold mode.
set to normal mode Now that you have the gyro initialized correctly, flip the GEAR switch. This will make the gyro go into standard rate mode.
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 not, then go to [REVERSING SW] and change the 'RUDD' channel.
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.
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 have my tail servo mounted up front and I added a slight bend to the front section so the link is at the same height as the ball on the servo arm. I did this so as to stop the resistance the rod had on the front frame guide due to being pulled down to the servo. I also use 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. The instructions with most gyros say to use a much longer distance however I found it to work best at around 13mm. Next 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. If you are not using a stock tail slider then use the other technique. Set the tail lever so that an imaginary line drawn from the two screws is parallel to the tail shaft. Next 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.
  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 9253/9254 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.
Set back to HH Now that you're done with that, you need to flip the GEAR switch back to heading hold mode.
Notes about the gyro HH/Standard Rate 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.
Flying adjustments To get the tail to move faster or slower, adjust the rudder channel travel. Go to [TRAVEL ADJUST] and set 'rudd' 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 9253/9254 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 you the tail wags in a hover then decrease the gain. Go to the [TRAVEL ADJUST] menu and decrease the value for the GEAR.
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).