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Stability Modes

Normally a helicopter flies in rate (acro) mode: centring the sticks stops the rotation, but it doesn't level the helicopter. Rotorflight also has self-levelling modes, using the accelerometer:

Mode Behaviour
ANGLE The stick sets a tilt angle. Centre the sticks and the helicopter levels itself. It can't flip.
HORIZON Self-levelling near centre stick; at full stick it flips and rolls like normal.
TRAINER Normal flight, but tilt is limited to a set angle (Acro Trainer).
RESCUE A panic button: levels, flips upright if inverted, climbs and hovers.

None of them hold position -- the helicopter will still drift with the wind. They're aids for learning and for getting out of trouble.

You need the accelerometer calibrated with the helicopter level, and turned on on the Configuration tab.

A mode switch

Example: a 3-position switch on channel 8 (AUX 3) -- down for normal flight, middle for HORIZON, up for ANGLE.

  1. On the radio, put the switch on channel 8.
  2. On the Modes tab, Add mode → HORIZON. Set the channel to AUX 3 and drag the range over the middle switch position.
  3. Add mode → ANGLE, AUX 3, range over the top position.
  4. Save, and check each mode lights up in its switch position.

Add RESCUE on its own switch the same way, and set it up on the Profiles tab -- see Rescue.

Stopping the drift

Self-levelling holds the flight controller's idea of level, which is never quite the helicopter's real hover attitude -- so it drifts. Trim that out with the accelerometer trims.

Don't use your radio trims

Keep roll, pitch and yaw trims on the radio at centre. Radio trims are a stick input, which in self-levelling modes means a constant tilt command.

Hover tail-in in ANGLE mode with the sticks centred and note the drift:

Drifts Change
Left Increase roll trim
Right Decrease roll trim
Backwards Increase pitch trim
Forwards Decrease pitch trim

Ways to set the trims:

On the radio, open Accelerometer trims in the Rotorflight Lua suite, change the values, and save. Fly again and repeat.

Under Accelerometer Trim on the Configuration tab.

Add Accelerometer Trim roll and pitch adjustments on a stepped switch, and trim in flight.

With set enable_stick_commands = ON, disarmed, in ANGLE or HORIZON mode: hold collective high, yaw centre, and move the cyclic stick in the direction to trim. Each step beeps; the trims save when you let go of the collective.

Collective Yaw Pitch Roll Does
High Centre Centre Left / Right Trim roll
High Centre Forward / Back Centre Trim pitch
High Left Back Centre Calibrate accelerometer
Low Left Back Centre Calibrate gyro

Tuning the levelling

The Auto-leveling Settings on the Profiles tab set how firmly each mode levels and the maximum angles. The defaults are a good start.