Fly-Sky Configuration
and Helicopter Setup Manual

Tail and Gyro Setup

This is an area that confuses a lot of new hobbyists. It is not complicated if you understand that the Gyro is responsible for most of the work of keeping your helicopter pointed in the direction you intend.

Two new terms to understand is the Gyro Rate Mode, and Head Holding Mode (HH).

Rate mode will try to compensate for unintended tail movement but does not remember the actual starting position and therefore can not bring the tail back into the last known heading. HH mode on the other hand remembers the last heading (when the stick was last centered) and unless it is instructed to get a new heading, it will aggressively attempt to bring the tail back to the saved heading. The HH mode has a signal gain setting that is controlled (the amount of gain) through channel 5 of the receiver. The gain value sets the sensitivity of the HH mode. Too little gain, and the margin (degrees) of off heading increases, too much gain, and it will fight itself trying to maintain a heading (resulting in what is called Tail Wag).

Note:Flying manually without any gyro is possible, but incredibly difficult even for experienced pilots. The gyro helps the pilot by comparing the rudder signal you provide from the transmitter (“what you want the helicopter to do”) with the actual detected motion of the helicopter (“what it’s actually doing” or what was done to it by environmental factors or inherent counter-forces of rotary flight). So, if you told the helicopter to stay pointing (center stick) in one direction and the gyro knows the helicopter is actually rotating anyway because of wind or main blade torque, it will add or subtract from the rudder servo signal until the helicopter actually stops rotating, just like you asked it to. As an example, if you’re in a stable hover when the wind gusts, the gyro will automatically fight to prevent the wind from blowing the tail around downwind (“Weather-veining”). If you increase or decrease throttle, the gyro will automatically try to keep the tail from swinging around due to the reactive torque from the main rotors.

A bit of history: “Gyro” is actually short for “gyroscope”… the same instrument you might have played with as a kid in the form of a top, or used in physics class to learn that a spinning object “wants” to maintain it’s orientation, and will expend rotational energy to do so. Traditional helicopter gyroscopes actually had a motor-driven spinning flywheel weight surrounded by bump switches to detect when it’s orientation was changing. This was an unreliable, slow, and heavy device, but far better than manual rudder control. Modern gyros are lightweight piezo-electric force gauges with no moving parts, and a bit of computer intelligence that allows for a really cool function called “Heading Hold.” Not all gyros have a Heading Hold mode, but it’s a shame to use a gyro without HH mode on a good helicopter.

Because the gyro is now a small computer, it can not only know that the gyro is moving, but how fast and long it’s been moving. This means it mathematically integrates the simple rate changes over time, and because it can keep track of all these changes, it knows “where it actually is” vs. “where it should be” according to what you’ve told the helicopter to do. As a result, when the servo fails to react fast or powerfully enough to overcome an undesired motion, the gyro knows it’s not where it should be and continues to adjust until it achieves the original position. This means any time you’re not telling the helicopter to rotate, HH mode remembers the last commanded heading and will aggressively attempt to bring the tail back to the saved heading, regardless of how long it has to work to get there. The HH mode has a signal gain setting that is controlled (the amount of gain) through channel 5 of the receiver. The gain value sets the motion sensitivity of the HH mode. Too little gain, and it won’t notice small movements that can still add up to being off-heading. Too much gain, and it will see it’s own corrections and fight itself trying to maintain a heading (resulting in what is called “Tail Wag” when it overshoots repeatedly).

What is Drift?

Drift is a term Drift is a term used by pilots to describe the tail wondering off from the center position when there is no rudder input. There are a few things that can cause drift. First not all gyros are of the same quality. Economy gyros are effected by voltage and temperature. As the battery drains during flight, the gyro gain is changed internally. Once the gain reaches a threshold it can actually induce drift. During setup, you can adjust the gain to its edge, and you will notice the servo start to move on its own, and sometimes it will move all the way to one end of travel just sitting there. This is why you will be asked to adjust your gain until you experience an aggressive tail wag, then back off the gain just enough until it stops. This will give you enough margin to keep it from reaching the low voltage threshold where drifting starts. Temperature effects gyros as well. If you fine tune your gyro at one temperature, and then (like the next morning when the temperature is different) fly in a different temperature, you may either see tail wag or drift depending on how the gyro electronics are effected by the temperature. It is a good practice to let the gyro adjust to the current temperature before putting it into flight. In other words, don't just run outside with your room temperature gyro, and start flying in 50 degree skies. You will find yourself fighting for tail control right off the start. Instead, take it outside, and give it ten minutes to adjust to the temperature before flying.

Lets move on to adjusting the tail. Most of the tail setup is done in Rate mode. However for the Gyro to properly initialize, we need to start the model up in HH mode. We need to return to the configuration program to assign the VR(B) dial to channel 5. This is done using the MIX settings (Fig. 17).

Select the MIX option, and select MIX 1 from the drop down list.

Fig 17ates, and the Switch to ON.

Gyro Gain VR(B) Setup

There does not seem to be a standard on which direction the VR(B) dial should be turned to set the gyro into Head Holding (HH) mode, or Rate mode. I prefer that the HH mode is obtained using a clockwise (CW) rotation, and other pilots prefer to use a Counter Clockwise (CCW) rotation. The Blue Ray 450 RTF package includes this radio, and it is typically setup to use CCW for HH mode.

In some documentation on the Internet, the instructor will tell you to set the dial to 10 o'clock and use CCW to adjust the gain. Others such as this document will demonstrate a method that will work on any FS-CT6A radio. Do not rely on information stating you should set the dial to a specific clock position. That position depends on the way the VR component is installed, the type of gyro, and the reverse setting for channel 5 in the radio, and the reserve setting of the gyro itself.

The VR dials are potentiometers. This is a Variable Resistor hence the abbreviation of VR in the manual, and labeled as such on the radio. Some FS-CT6A radios have the VR dial installed with the halfway point (dial position indicator) pointing straight up. Some have the indicator pointing to 9 o'clock for the mid-point. Some may be different all together. Test your dial by rotating it in both directions to find out the end points, and the halfway point. The VR value at mid-point is the zero voltage setting. At zero voltage signal, the gyro will be on the edge of HH and RATE mode, and will typically default the gyro into rate mode because there is no signal at the zero or halfway position.

To determine which direction your radio uses to obtain HH mode, turn the dial all the way in one direction. Then (with the throttle cut switch On – safety measure) turn on the transmitter, and then plug the battery into the helicopter. If the Gyro HH indicator (light emitting diode - LED) illuminates, then you have found the direction for HH. If you do not like that direction, you can change it very easily. Simply use the RESERVE button in the program to change the CH5 check box, and set the physical REVERSE switch (or dial) on the gyro. Those two settings allow you to set the direction of VR(B) to your preference for HH mode.

The remainder of this document will use the CW direction for HH mode.

On the radio, turn the VR(B) dial to the mid-point and then turn it CW 60 degrees (2 hour markers) to make sure the gyro initializes in HH mode. You can also leave it at the mid-point, then turn on the radio, and rotate the dial until the gyro light illuminates, turn it 60 more degrees, and then disconnect, and reconnect the battery so that the gyro initializes in HH mode. zes in HH mode.

If you have attached the servo horn to the tail servo, then remove it. Verify the tail linkage rod is not binding, and can easily travel to both extremes available by the tail slider. Set the Throttle Cut switch (SW-A) toward you to prevent the motor from turning. Set the Idle Up switch (SW-B) to OFF away from your. Left stick horizontal slider is centered, and the vertical trim slider (on the radio) is all the way down.

Power up the helicopter. Let the Gyro initialize, typically with a three beep signal, and the servo find its center . Attach the servo horn at 90 degrees to the tail rod linkage (Fig.18)

*Note - you can use the boom as your 90 degree reference since the tail rod linkage is supposed to be parallel to the boom. Some servos such as the Align DS-520 (Fig. 18a) need to be mounted at an angle, however the ball link is still 90 degrees to the boom.

Fig 18

Fig 18a

Hint: if you have a slow servo, then using a longer horn will help in maintaining position. If you have a fast digital servo then using a hole closer to the hub will help. The horn and hole position should allow the servo to move the tail slider completely against each side of travel without binding the servo. Verify the servo horn does not come in contact with any part that would result in a stripped servo gear.

Loosen the two screws that mount the servo to the boom. Move the servo along the boom so that the tail slider is slightly closer to the boom from center of the shaft. The tail blades should have a slight pitch.

Snug up the rear mount screw so that the servo does not move on the boom. Now we want to check for correct movement direction. Some Gyros have a reverse switch, others do not. If your gyro does not have a reverse switch, you will need to use the reverse (servo) option in the program for channel 4.

To determine if the servo is moving in the correct direction, power up the helicopter, and apply slight left stick towards the left. If the tail slider (looking from behind) moves to the right, then it is correct. In other words, the tail slider should move in the opposite direction as the radio stick. If your physical arrangement is different than a TRex or clone, then observe the tail pitch. The left stick controls the Nose of the helicopter. With Left stick towards the left, it is responsible for flying the nose of the helicopter to the left or CCW looking from above the helicopter.

*Hint – To keep yourself oriented between the radio controls and the helicopter, always fly the Nose of the helicopter. NEVER fly the tail. This is a common problem for new pilots. Using the left stick pushed over to the left should cause the nose to go left CCW. Right stick with the stick leaning towards the left causes the helicopter to slide to the left. When both sticks are going to the left, you get a nice banking left turn with the tail following the nose. When you start flying “Nose In” (flying towards you), the nose orientation will be even more important. So don't pick up a bad habit of concentrating on the tail. Put your mind's eye in the nose of the helicopter (Fig. 18b)

Fig 18b

Fig 19

Fig 19a - Full Right Rudder (stick right)

Fig 19b – Full Left Rudder (stick left)

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