Differential Spoilers

Usage

Normal Flying-wing aircraft uses two control surfaces as Elevons to control pitch and roll. In some cases, rudders are added to the winglets to control yaw. Differential spoiler takes advantage of splitting elevons to 4 independent control surfaces: normal elevon functions are reserved for pitch and roll control, but yaw control is done by using two surfaces on one side of the wing to create drag force thus controlling yaw motion. If calibrated correctly, it will ensure pilot has smooth yaw control during take-off and landing as well as compensation during turning (similar to differential aileron).

Left Yaw by inducing drag on left wing: Right Yaw by inducing drag on right wing:
4surfLeftYaw 4surfRightYaw

Preparation

To use differential spoiler function, the airframe is required to use have 4 control surfaces (2 on each wing) and use elevon configuration. Setup one surface on each side using output channel 1 (roll) and channel 2 (pitch) as elevons:

If you have not done so, please follow the tutorial to setup elevon properly: Archived:APM2.x Wiring QuickStart

Setup

Once you have setup two elevon channels successfully, connect the additional 2 surfaces to auxiliary channels (5 to 11 on APM2.X) and set corresponding RC_FUNCTION:

Function Name Function Number Description
Differential Spoiler 1 16 This should be set to the control surface on the same side of elevon connected to output channel 1 (roll channel)
Differential Spoiler 2 17 This should be set to the control surface on the same side of elevon connected to output channel 2 (pitch channel)

By now, you should have normal elevon function in MANUAL mode. Now switch to FBW mode and use RC controller to test roll, pitch and yaw. Adjust corresponding RC_REV until the behavior is correct.

Note

If you have servo direction reversed on either side of the wing, it is most likely that the servo orientations are different or rotation is reversed through programming on some digital servos