GroundDirection
This Node can be used to retrieve a direction vector (3 values: X, Y, Z) based on a projection of the current aircraft position and orientation on the ground. Essentially this node will project the the aircraft along the gravity vector onto the ground to create a 2D vector with the X and Z components of this projection. The Z vector is the "up" vector along the line of gravity from the projection to the aircraft.
Before this GroundDirection vector is returned, it can be modified using the X, Y, Z inputs for the node, with the additional vector components being added to the ground vector before being output. Alternatively you can edit these values in the node Inspector:
Node Input
The GroundDirection node has the following inputs:

X
The X component of the vector that will be added to the base ground direction vector. Default value is 0 (editable in the node) and the input node value is a single float.

Y
The Y component of the vector that will be added to the base ground direction vector. Default value is 0 (editable in the node) and the input node value is a single float.

Z
The Z component of the vector that will be added to the base ground direction vector. Default value is 0 (editable in the node) and the input node value is a single float.
Node Output
This node will output a 3 value vector of the X, Y and Z components for the ground direction (summed with the addtional vector generated by the X, Y, and Z input values, if supplied).