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Main Motor

To control the main motor of your model, the mixer must be configured using the CLI.

# Use the Stabilized Throttle at full range:
mixer input ST 0 1000 1000

# Mix the Stabilized Throttle (ST) into Motor 1:
mixer rule 8 set ST M1 1000 0

Tail Motor

If you have a motor-driven tail you must mix the Stabilized Yaw (SY) into the tail motor. Also tell Rotorflight that you use a tail motor, so yaw PID output won't be normalized. You can also specify a minimum idle speed, so the tail motor won't completely stop in-flight if the mixer output is zero or less.

mixer input SY -1000 1000 500
mixer rule 9 set SY M2 1000 0
set tail_rotor_mode = MOTORIZED
set tail_motor_idle = 30

Always save your changes in the CLI.

Tail Torque Assist (TTA)

A servo driven tail can provide thrust in two directions. Although it's technically possible to reverse the tail motor direction on a motor driven tail in order to reverse thrust, it's usually not done because it's too slow. Instead, most helicopters with a motor driven tail rely on torque generated by the main motor instead of reversing the tail motor direction.

The K110 is an example of an helicopter with a motorized tail. The tail motor can only provide thrust for right yaw, not for left. If you give right rudder, the tail motor will speed up and the tail will move to the left. If you steer left, the tail motor will slow down and the tail will be swung in the right position due to the main motor torque. At least, that's the plan. There are situations where this doesn't always work, e.g. if you unload the main rotors and thereby decreasing torque: this can lead to weathervaning in some situations. Running a governor might make things even worse.

Rotorflight offers a feature called Tail Torque Assist to make the tail more effective by increasing and decreasing main motor torque at the right moment. Currently it can only be used when tail_rotor_mode = MOTORIZED. Servo driven tails could benefit from TTA as well, but that needs more work.

To activate TTA set gov_tta_gain to non zero. TTA works only with the governor enabled, i.e. when gov_mode is not NONE and feature GOVERNOR is enabled. There are two settings that affect TTA:

• gov_tta_gain: defines the gain used, 1 - 200, typical value 10..50. A value of 0 disables TTA.
• gov_tta_limit: the upper bound for the RPM/throttle increase in %. The resulting headspeed might be more than gov_headspeed.

The concept of TTA was introduced in Heliflight 3D, and is also used in the OMP M1 and M2 V2. Jonas Wackershauser calls it TALY, or Torque Assisted Left Yaw, and he has a great video describing the benefits of it.