Step 41 – Gyro Overview

For my helicopter, I have a JRG7703D gyro connected to a Futaba S9257 tail servo.  As stated earlier, this servo is a 4.8volt servo, so I’ve programmed the ESC to output 5 volts.

For videos on gyro set up, visit http://www.helifreak.com/showthread.php?t=95258

For my Futaba R617FS receiver, the gyro gain is fixed at CH 5.  It is not assignable.  Click on image below to enlarge.

Step 42 – Tail Servo Adjustments

  1. Disconnect the Gyro and connect the tail servo directly into the receiver.
  2. Ensure the radio has the GYRO feature set to OFF (inhibit).
  3. Put the throttle to mid-stick and ensure the tail servo arm is at a right angle.
  4. Adjust the linkage rod until the tail rotors are at zero pitch.
  5. Reconnect the gyro.

Step 43 – Futaba T7C Transmitter Configuration

Note that with a Futaba radios, the % gain setting is the true gain applied.  Here are my settings for the Futaba T7C transmitter and the JR G770 3D gyro:

  • REVO-MIX:
    • REVO –> INHibit
  • GYRO:  the gyro gain value is set based on switch position.  If you tie gyro gain to a 2 position switch, then you can have 2 gain values.  For a 3 position switch, you have 3 configurable gain values.
    • UP = A 17% (true gain) – for AVCS heading hold mode.  Gyro will continuously try to pull tail back.
    • CT = x yy % (true gain) – available if 3 position SW-E used.
    • DN = N 17% (true gain) – for NORMAL rate mode.  Gyro will temporarily try to pull tail back.
      • To get the “A” or “N”, you must rotate the silver dial on the Futaba faceplate down past A 0% and it will flip to N 0%.
      • These percentages are define how sensitive you want the gyro to be.  With a low percentage, the gyro will barely move the servo if the heli changes direction.  With a high percentage, the gyro will move the tail servo immediately and the full length of the pitch range.  The higher the gain, the harder your tail servo is working.
    • GYRO = ON
    • MODE = GY
    • SW = B:

Step 44 – Tail Neutral Setting

  1. On the transmitter, set SW-B to set the gyro’s gain to be in HEADING HOLD mode.
  2. Power on the helicopter, but do not touch it for 3 seconds to let the gyro stabilize.  If is important for heading hold gyros to power up in heading hold mode.
  3. Set tail servo horn to 90 degrees (right angle).
  4. Flip SW-B to set the gyro to NORMAL mode.
  5. Adjust the length of the rudder control rod to ensure tail rotors are in the middle.
  6. Adjust the servo travel on the gyro to set the end points to prevent any binding.  That is, adjust the limit pot screw on the gyro to get full range of the blades.
  7. Verify the servo direction is not reversed.
JR G770 3D Gyroscope

JR G770 3D Gyroscope

Step 45 – Attach Tail Rotor Blades

  1. Open bag 500 HT5B and attach the tail blades.
  2. I put loctite on the screws.

We’ll adjust the gyro gain sensitivity once we do our initial flight testing.

Step 46 – Dual Rate, Endpoint and Exponential Settings

D/R and EXPO can be applied to the following channels:

  • CH1 – Aileron (up) & CH1 – Aileron (down)
  • CH2 – Elevator (up) & CH2 – Elevator (down)
  • CH4 – Rudder (up) & CH4 – Rudder (down)

On my Futaba T7CH, the following switches can be used to configure DUAL RATE (D/R) or EXPOnential:

  • SW A – Elevator Dual Rate / TH-CUT / P-MIX / TIMER
  • SW B – Rudder Dual Rate
  • SW D – Aileron Dual Rate
  • SW E – Idle up (norm / 1 / 2 )
    • By assigning CH4 rudder d/r/expo to SW-E, it will allow you to have different pirouette rates based on your flight mode (SW-E).
  • SW G – throttle hold

The following switches are assigned:

  • SW A – Elevator Dual Rate / TH-CUT / P-MIX / TIMER
  • SW B – Rudder Dual Rate
  • SW D – Aileron Dual Rate
  • SW E – Idle up (norm / 1 / 2 )
  • SW G – throttle hold
  • SW H – trainer switch
  • VR – hovering pitch

Pirouette Rate Overview

Pirouette rate is how the tail moves when turning the helicopter.  Two different pirouette rates need to be set:

  • Pirouette rate when turning in the same direction as main rotors.
  • Pirouette rate when turning in the opposite direction of main rotors.

There are two methods to set piro rates:  endpoint configuration OR dual rates.

Setting Piro Rate Using Endpoints

To set pyro rates, you would adjust endpoint settings on the Futaba radio for CH4 – Rudder.

  • E.POINT->CH4.  Push the left thumb stick either left or right to set the endpoint for each direction.

The problem with using ENDPOINTS for the gyro piro rate setting, is you get the same piro rate for all flight modes: NORMAL, IDLE1 and IDLE2.

Setting Piro Rate Using Dual Rates

The DUAL RATE functionality of the Futaba T7CH radio allows you to another set of endpoints for CH4-Rudder.  Using DUAL RATE, you can configure different piro rates depending on whether you’re in NORMAL, IDLE1 or IDLE2 flight modes.  This is useful since when in NORMAL mode, you don’t want rapid piro rates, but when in IDLE2 (3d acrobatics mode), you would want faster piro rates.

  • D/R,EXP -> CH> 4-RUD
    • D/R = xxx %
    • EXP = xxx %
  • Leave ENDPOINTS at 100% (or should it be 140%).