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Overview

The KFF parameter group (often appearing as KFF_ or MIX_) configures Feedforward mixing for ArduPlane.

Feedforward provides an immediate control surface movement proportional to the pilot's stick input (or another control axis), bypassing the slower PID error-correction loops.

Key Concepts

1. Rudder Mixing (KFF_RDDRMIX)

Used on aircraft without ailerons ("Rudder Only").

  • Function: It mixes the Roll controller output into the Rudder servo. This allows the autopilot to turn the plane using only the rudder.

2. Pitch Mixing (KFF_THR2PTCH)

Mixes throttle into the pitch axis.

  • Function: If your plane pitches up when you add power (due to motor thrust line), this parameter can automatically add down-elevator to compensate.

Parameter Breakdown

  • KFF_RDDRMIX: Roll to Rudder feedforward gain.
  • KFF_THR2PTCH: Throttle to Pitch feedforward gain.

Developer Notes

  • Library: ArduPlane/servos.cpp.

KFF_RDDRMIX

Default 0.5
Range 0 1.0

Rudder to Aileron Mix (KFF_RDDRMIX)

Description

KFF_RDDRMIX automates "Coordinated Turns" for airplanes.

When a plane rolls into a turn using ailerons, it often experiences "Adverse Yaw" (the tail swinging the wrong way). This parameter automatically adds a proportional amount of rudder to keep the nose pointed into the wind during the roll.

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KFF_THR2PTCH

deg
Default 0
Range -5 5

Throttle to Pitch Mix (KFF_THR2PTCH)

Description

KFF_THR2PTCH compensates for the physical design of an aircraft where the motor's thrust "pushes" the nose up or down.

Many planes, especially those with high or low mounted motors, tend to pitch up when you add power. To fly level, you have to manually push the elevator down. This parameter automates that correction. If you set it to 2.0, then at 100% throttle, the autopilot will automatically command a 2-degree pitch-down correction.

Tuning & Behavior

  • Positive Values: Pitch the nose UP as throttle increases.
  • Negative Values: Pitch the nose DOWN as throttle increases.
  • Calibration: Fly the plane in MANUAL mode. Add power and see which way the nose moves. Adjust this parameter until the plane maintains a level attitude when changing throttle.
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KDE Direct CAN Configuration (KDE) Landing Configuration (LAND)