Futaba GY520 w/ Spektrum DX7
Gyro How-to
last updated 3-15-2010

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1.
There are three things to consider when selecting a place to mount the gyro.
1. On smaller helicopters the flybar can swing down low enough to reach a gyro mounted on the top of the framset. On the Trex450 (not 450 Pro) some people turn the block upside down that the tail boom goes in then mount the gyro under the rear of the frameset.
2. The blue label on the gyro needs to be either up or down. Do not stick the gyro to the side of the frameset.
3. Make sure you can get to the button on the gyro.

When you mount the gyro, use the supplied foam tape. For small 300 class helis use the thin foam pad. For the large 600 and 700 class helis use the two thick pads with the metal plate in between.

2. Connections

Tip: Use a marker to write on the label 'R', 'G', and 'S' as shown in the bottom picture to the left. This would be very simple for Futaba to have done and would save some confusion.
'R' goes to the rudder channel on the receiver labeld 'Rudd' on the Spektrum or Channel 4 on most other receivers.
'G' means Gain and will connect to the 'Gear' channel on the receiver. Most other receivers have it labeled channel 5.

There are three things that need to be connected. 1) Servo, 2)Rudder channel, 3)Gain channel. The tail servo will connect to the side that has one socket. Click on the photo on the left to see the other two connections. This gyro comes with two servo leads, one with black connectors and the other with red connectors. It is great they did this so you do not get mixed up. In the picture on the left you see I am not using them. Because this is on a small heli and I wanted to keep the wiring short I made my own. If you use the two leads that it came with, the black one will connect to the side I labeled Rudder in the picture and the red will connect to the Gear (gain) side. On the receiver side, you will connect the black lead to the 'Rudd' channel and the red lead goes to the 'Gear'. Make sure you pay attention to the polarity of the receiver pins. The signal wire will be next to the labels on the receiver. The black wires will be away from the labels.
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.

3. 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'.

Note: In the picture, Aux2 is set to INH but this does not matter for this gyro setup. You can set this to what you need. For the gyro setup you do need GEAR to be set to GEAR. This tells the radio that you want to control the Gear channel of the receiver by using the switch on the radio that is labeled Gear.

4. Reverse setting Go to the [REVERSING SW] function and set channel 5 to NORM. With it in this position the gyro will be in heading hold with the gear switch up (position 0).
5. 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.
Go to the Program Mixes [PROG.MIX1],[PROG.MIX2], and [PROG.MIX3].

Look at all three program mixes and see if any of them have RUDD or GEAR as shown circled in red in these two pictures. If you do not know why the mix is there you can inhibit it by pressing the 'clear' button at the bottom right of the radio.
6. 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 rudder trim under the rudder stick is centered.
7. 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 100%. 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.
8. set the gyro gain Go to [TRAVEL ADJUST] menu and use the 'select' button to select 'GEAR' and make sure both sides are also set to 50%. 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 50 but later you may need to adjust this up or down a little to get the best performance. On the small helicopters a gain of around 50 is normal. My setup on the miniTitan is 55. On a larger 600 class (50 size) it might be in the 80 to 100 range. If you see the tail wag then lower the gain. If the tail does not feel solid and lets go when in a high load then increase the gain.
9. Disconnect tail servo
electrical and mechanical
In a moment you will turn on the receiver. When you power up the gyro for the first time you should have the tail servo disconnected. The gyro could be set for the wrong type servo. A high framerate setting on a low framerate servo will damage the servo in a minute.

Next disconnect the rudder link from the tail servo. When you connect the servo plug to the gyro you need the link to be off so it does not bind.

Power up the radio and the receiver. Wait three seconds for it to initialize. Hold in the button on the gyro for three seconds. The light will change to a violet color. Release the button and you will see the gyro light repeat a '1 blink'. Note the color of this light. This will tell you the current mode the gyro is in.
Blue = Digital 1520uS
Red = Digital 760uS
Violet = Analog servo
To change the setting, quickly press and release the button on the gyro. Once you have the servo type correctly set then hold the button on the gyro for 2 seconds to move to the next function. This will save the setting. Now power off the receiver and plug the tail servo up to the gyro. Keep the tail control link off of the servo. It will be connected later.

Blue 280Hz Red 560Hz Violet 70Hz
S9253
S9254
S9257
S9650
HS-6965
3400G
BLS251
S9251
S9256
All analog servos
10. Check Point At this time we need to check that the radio is correctly controlling the gyro. Turn on the radio then connect power to the receiver. It will take about 3 seconds for the gyro to initialize. For the first second the light will blink slow. The next second it will blink fast. Then the light will stay on solid. The color at this point will indicate the mode the gyro is in.
Solid Red: Heading Hold
Solid Blue: Standard Rate mode
Flip the Gear switch up (position 0) and confirm that the light on the gyro is solid red. Now flip the switch down and confirm the gyro is now solid blue. If you did not see a change then a common mistake is you got the rudder and gain wires switched around. Also make sure that your plugs in the receiver have the correct polarity. The black wires of every plug all should be on the same side of the receiver.

Next check that the gyro responds to the rudder stick. Watch the light on the gyro, when you move the rudder stick from center, the light needs to change from a solid color to a flashing violet. This needs to occur when you move the stick left as well as right. When the stick is centered it needs to be a solid color (red HH, blue non-HH).

Next check that the gyro can sense the helicopter is moving. Watch the light on the gyro, when you rotate the helicopter the light will blink fast either blue or red. One direction will be blue and the other direction is red.

If all of this checks good then continue to step 11. If not then go back to step 1 and start again. If you did that and still have problems then <email me>. Please provide as much info as you can.

11. set to Standard Rate On this gyro it is easy to see the state it is in. Look at the light:
Solid Red: Heading Hold
Solid Blue: Standard Rate mode

Move the Gear switch down (position 1). The light on the gyro will turn solid Blue.

12. servo direction This is going to vary for different helicopters and different brand servos. It also depends on how the link connects to the servo. In general 95% of helicopters should pull the tail control rod forward when you move the rudder stick to the right. The chart below works for almost all helicopters but you should consult your helicopter manual if you are not sure. Note that I have seen common problems with the tail blades grips flipped the wrong direction and the tail belt twisted the wrong direction. Look at the picture on the right. With the main blades rotating clockwise as seen from above, the tail rotor should rotate counter-clockwise as viewed from the right side. Most engineers will design the system so the front tail rotor blade moves up into the rotor downwash.
Left Center Right

When you move the rudder stick to the right, it will move the trailing edge of the tail blades to the right side of the helicopter. If it does not do this, then go to [REVERSING SW] in the radio and change the 'RUDD' channel.

13. gyro direction Rotate the helicopter so the nose moves to the left and watch the rudder servo. The servo needs to rotate in the direction that would cause the trailing edge of the tail blades to move to the right side of the helicopter. If not, then enter setup mode of the gyro (hold the button for 3 seconds). The gyro will repeat a '1 blink'. Hold the button down again for 3 seconds to get to the next function. The gyro repeats a '2 blink'. Quickly press and release the gyro button to change the direction. Hold the button on the gyro for 2 seconds to go to the next function. This will set it up for the next step.

Note: If the gyro is set for the wrong direction the helicopter will spin extremely fast as soon as it gets light on the skids. So it is important to make the checks on the bench so you do not risk damaging the helicopter.

14.

With the rudder link disconnected from the servo. The first thing to do is make the link slides as free as possible. Adjust the guides to acheive the least resistance. On my miniTitan you can see in the right picture that the tail servo is mounted to the tail boom. I rotated the servo mount to a position that put the ball directly inline with the tail control rod. Also note that I added a slight bend to the front section of the tail control rod so that the link is at the same height as the ball on the servo arm.

Once you get the link as free from resistance as you can, you need find a position for servo arm. From the previous step the gyro should be on and in a 3-blink mode. If not, hold the button down to enter setup mode. That will get you a 1-blink, hold the button down for 2 seconds to get to 2-blinks, then again for 2 seconds to get to 3-blink. That is the servo limit setting mode. It puts the gyro in a standard rate mode so the servo will center when the rudder stick is centered.

Place the servo arm on the servo spline. At the left, look at the top picture. Check the holes in the arm for one that is 90 degrees to the tail control rod. In the picture you see the link it bent down, the 90 degree angle is in reference to the unbent part of the tail control rod. If you do not have a hole exactly 90 degrees then take the servo arm off and rotate it to another position. If none come close you can use the Rudder Sub-trim to adjust this but after you complete this step make sure you turn the heli off then back on so it will initialize at the new sub-trim position.

Now that you have found a position for the servo arm you need to mount the ball on it. For a 600 to 700 class (50-90) mount it about 13.5mm from the center. For a small heli, 300 class(ex. miniTitan, Rave, Trex 450), mount it 7.5mm from center.

Next adjust the length of the tail control rod so that with the front link connected to the servo, the tail lever is 90 degrees to the tail control rod as seen in the middle picture on the left. The bottom picture on the left also shows another way to look at it, the control lever is parallel to the tail shaft. Make sure when you are adjusting the tail control rod links that you do not get too much of the threads showing. With a tail mounted servo you can move the mount on the tail boom to acheive your goal. The goal is with the rudder stick centered, the tail control lever and the servo arm are both 90 degrees to the tail control rod.

Next you set to limits. The gyro should still be in the 'Servo Limits' mode which is a 3-Blink. And the tail control rod link needs to be disconnected from the tail servo arm. To set the first limit, quickly press and release the button on the gyro. You will see the servo move to one side. Move the tail control rod link to the ball. Just hold it on top of the ball. Use the rudder stick on the radio to increase/decrease the servo. Adjust to get the maximum travel without binding. Now quickly press and release the button on the gyro. If everything was okay then the light on the gyro will momentarily change to violet and the servo will travel to the other side. Once you set the travel for this side, quickly press and release the button on the gyro. If everything was okay then the light on the gyro will momentarily change to violet. Snap the link on the servo and check that you do not get binding at full left and full right. If you need to readjust then quickly press and release the gyro button.

15. Max Rotation Rate From the servo limit function, hold the gyro button down for 2 seconds to get to the Flight Mode selection. The light on the gyro will do a 4-Blink. The color of this 4-Blink indicates the mode it is in.
Blue - F3C 450 degrees per second
Red - 3D 720 degrees per second
To change the mode, quickly press and release the button on the gyro.

Note: Just because you plan to fly 3D does not mean you need to set the gyro to 3D mode. You should make the decision based on what your flying style is. I fly smooth 3D and prefer the slower rotation rate.

16. Gyro Response Rate Hold the gyro button in for 2 seconds to get to the 5-Blink mode.
Blue - Standard Response (default selection)
Red - Fast Response (for lightweight small helis with a fast tail servo)
Violet - Slow Response (for scale helis)
To change the mode, quickly press and release the button on the gyro.
17. Exiting Setup Mode To exit the Setup mode, turn the receiver off.
18. Final Check 1. Move the rudder stick right and verify the trailing edge of the tail blades move to the right.
2. Move the nose of the helicopter left and verify the trailing edge of the tail blades move to the right.
3. Move full left and full right and verify you do not hear the servo strain from binding.
4. Verify the gyro is in Heading Hold mode, light on the gyro is Red.
19. 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.
If you the tail wags in flight then decrease the gain. Go to the [TRAVEL ADJUST] menu and decrease the value for the GEAR.