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Version: Development Snapshots

Servos

Open the Servos tab and confirm that you have the correct number of servos. If this is not the case, please confirm you have installed the correct firmware (either 'M' motorized or servo tail) or if you are using a drone FC that your Remapping is correct.

Servo Tab

Servo Numbering​

Direct​

For helicopters that uses mechanical mixing, where the Pitch, Roll, and Collective movements are each controlled by a dedicated servo by means of a complex series of linkages and levers from the servos up to the swashplate.

Servo 1 - Pitch
Servo 2 - Roll
Servo 3 - Collective
Servo 4 - Rudder

CCPM​

For 120, 135 and 140 deg CCPM swashplates. Looking from the tail towards the nose of the helicopter:

Servo 1 - Pitch (inline with the centerline of the helicopter)
Servo 2 - Left side
Servo 3 - Right side
Servo 4 - Rudder

Servo Tab

Fixed pitch​

90deg L​

Servo 1 - Pitch (inline with the centerline of the helicopter)
Servo 2 - Side servo
Servo 3 - Rudder

Servo Tab

90deg V​

Servo 1 - Left side
Servo 2 - Right side
Servo 3 - Rudder

Servo Tab

Servo Override​

The toggle at the bottom of this page enables the servo overrides. The purpose of this is so that each servo can be driven by the slider to calibrate the range and center points. Beside each servo is an individual override.

The servo override slider scale is in degrees

Servo Tab

Servo Configuration parameters​

Servo Tab

Center​

In general this will be 1520us for cyclic servos and 760us for tail servos.

Min and Max​

These are hard limits to prevent servos binding or moving outside of their mechanical limits. If a servo is commanded to a point that is greater or less than it is capable it will buzz and likely burn out. These settings should be used to limit the command.

Scale Neg and Scale Pos​

Scales the negative and positive direction of the servo to match the commanded angle.

Rate​

This is the servo frequency. This will be specified by the manufacturer. A large proportion of servos suitable for cyclic operate at 333Hz.

note

For Rotorflight 2 it is recommended that tail servos are assigned to a different timer than cyclic servos (see Remapping).

This means that tail servos can be set to a different frequency (i.e. faster).

Speed​

Servo Speed Equalization. The aim of this parameter is to remove the collective "bobbing" when fast elevator changes are applied.

The bobbing happens because the elevator servo has to move double distance vs. the aileron servos, when elevator position is changed. If the change is faster than the servos can go, the aileron servos will reach the target sooner than the elevator servo, causing the swash to jump slightly in the process.

To tune this value increase the speed value (it's actually ms/60°, like in the servo datasheet) until the bobbing is not visible any more. It should be always ok to use the value from the servo datasheet if unsure.

Reverse​

Toggle for forward or reverse servo direction.

Geo Cor​

Geometry Correction. Servos are rotary, so at high angles this results in smaller swashplate movement for each degree of servo movement. Geometry correction accounts for this and provides better control at high angles (e.g. 3D flight).

In order to use this feature it is important to set the servo arm at 90° (with servo center) and calibrating the servo scale.

Servo Setup and Calibration​

Step 1​

  • DO NOT CONNECT THE SERVOS YET!
  • Confirm and set the servo center to your servo manufacturers recommendation. For Cyclic this will usually be 1520us, and for Tail it would be 760us.
  • If a servo's center is 760us, make sure to change the min/max to -350/350 instead of -700/700, and pos/neg scales to 250 instead of 500.
  • Confirm and set the servo rate as specified by your manufacturer. For many digital cyclic servos this is 333Hz and for most tail servos this is 560Hz.

Step 2​

  • Connect the servos.
  • Set Servo override to ON.
  • Fit servo arms to as close to 90 degrees as possible.
  • Slide Servo 1 override in the positive direction (i.e. right).
  • Confirm the servo arm travels up towards the swashplate. If not toggle the servo reverse.

Repeat with remaining cyclic servos.

Step 3​

  • Set each of the override sliders to 0 degrees.
  • Adjust center to level the servo arm (0° or 90° depending on servo installation orientation). One quick way is to slide the override bar and copy the output value from the blue bar into the center and press save. Make sure to reset the override to see the correct effect.

Repeat with remaining cyclic servos.

Step 4 (Usually Not Required)​

With the servos installed in the helicopter, adjust Min/Max so that the arm & ball won't hit anything in the heli frame (servo override @ 80° / -80°).

Repeat with remaining cyclic/tail servos.

Step 5 (Usually Optional)​

Calibrate the range. Not all servos move by the same angle for each change in command. This step calibrates this range so that the servo's move by the same amount. This means that the Geometric Correction can be used.

  • Set the override to a positive value (e.g. 30°)
  • measure the current servo arm angle and increase or decrease the Scale Pos until the servo arm angle matches the override angle.

Servo Tab