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Mixer & Swashplate Setup

The mixer calibration makes the blade pitch the flight controller asks for match the blade pitch you get. Rotorflight's rates, limits and default PIDs are all in real degrees, so this step matters: with an uncalibrated mixer, every number is wrong by the same unknown factor.

You need the servos set up first, and a blade pitch gauge. All settings are on the Mixer tab.

1. Swashplate type and directions

  1. Choose the Swashplate Type -- CCPM 120° for most helicopters -- and check the servo layout diagram matches your helicopter.
  2. Set the Main Rotor Direction (looking from above; usually clockwise).

  3. Turn on Enable Mixer Override and check the directions with the roll, pitch and collective sliders:

    Command Swashplate must
    Positive roll Tilt right
    Positive pitch Tilt forward
    Positive collective Rise -- blade pitch increases

    If an axis moves the wrong way, change its Control Direction to Reverse. (If the whole swashplate moves oddly -- one servo fighting the others -- go back and check the servo directions.)

Use your radio sticks

Enable Mixer Passthrough drives the override from your radio sticks, which is handy for the direction checks.

2. Level the swashplate and zero the pitch

With all overrides at 0° (servo arms level):

  1. Adjust the servo-to-swashplate links until the swashplate is level, both side to side and front to back.
  2. Adjust the swashplate-to-grip links until the main blades read 0° on the pitch gauge.

If the links aren't adjustable, use the Roll, Pitch and Collective trim under Swashplate Trims instead.

3. Calibrate collective

  1. Set the collective override to +10°.
  2. Measure the blade pitch.
  3. Adjust Collective calibration until the gauge reads 10°.
  4. Set collective to -10° and check. If it isn't also 10°, adjust Collective Geometry Correction until +10° and -10° read the same.
  5. Set collective back to 0°.

4. Calibrate cyclic

  1. Fit the pitch gauge and turn the rotor head until moving the roll override changes the blade pitch the most -- that's where cyclic is measured.
  2. Set the roll override to +8° and measure the blade pitch.
  3. Adjust Cyclic calibration until it reads 8°.

5. Set the limits

These protect against mechanical binding. Use the override to find where the head runs out of travel:

Limit Set it to
Collective blade pitch limit The most collective the head can do without binding -- usually 14-16°. The collective you actually fly is set on the Rates tab, below this.
Cyclic blade pitch limit The most cyclic the head can do around zero collective -- usually 12-16°. This isn't your cyclic rate; it's the physical limit.
Total blade pitch limit The most cyclic + collective together. At full collective, add cyclic until something binds or a servo reaches its end -- the swashplate centre ball will stop following. Repeat at full negative collective.

Check there's no binding anywhere across the full range of collective and cyclic combined.

6. Collective tilt correction (optional)

At the extremes of collective, some heads tilt the swashplate when cyclic is added. At full positive collective, add cyclic and watch the swashplate centre ball: adjust Positive Collective Tilt Correction until it stays put. Repeat at full negative with Negative Collective Tilt Correction.

7. Tail rotor

  1. Set Tail rotor type to Variable pitch.
  2. Set the yaw override to 0°. Adjust the tail pushrod so the tail bellcrank is at 90°; if that doesn't give 0° tail blade pitch, fine-tune with Yaw center trim.
  3. Check the direction: positive yaw must push the nose right (tail left). Reverse Yaw Control Direction if not.
  4. Set the yaw override to +22°, measure the tail blade pitch, and adjust Yaw calibration until it's about 22°. Check -22° too.
  5. Override to about ±60° and set the CW / CCW Yaw Blade Angle Limits to the most that doesn't bind.

Tail geometry is never perfectly symmetric, so the calibration and limits won't match the gauge exactly at every angle. That's fine; the point is to get the numbers close, so the default tail gains work.

  1. Set Tail rotor type to Motorised. The tail ESC goes on motor output 2.
  2. Leave Yaw calibration at 100%.
  3. Set Motor idle throttle just high enough that the tail motor keeps turning.
  4. See Motorised Tail & TTA for the rest.

Turn the mixer override off when you're finished -- it blocks arming.

Next: RPM Measurement and the Governor.