Some blade characteristics or output are refered to as being In-plane or out-of-plane. These refers to geometrical planes that are characteristic of a blade and its movement around the main shaft.

When talking about out-of-plane at the blade root, we refer to the plane that contains the main shaft and the Pitch axis. When talking about out-of-plane for a Blade aerodynamical station (for example at the tip of the blade), we refere to the plane that contains the elastic center of that station and that is parallel ot the out-of-plane plane at the blade root.

The figure below illustrates this concept: the out-of-plane plane for the blade that is vertical is highlighted in yellow.

This plane is used mainly for two sensors:

Out-of-plane deflections
This output can be found in the Blade [Time] sensor and the Blade aerodynamical station sensor
The out-of-plane deflection is the deflection along the line defined by the Airfoil plane and the out-of-plane plane.

Out-of-plane moments
This output can be found in the Blade [Time] sensor
The out-of-plane moment is the bending moment that is perpendicular to the out-of-plane plane (i.e. that corresponds to a deflection in the out-of-plane plane)

The figure below illustrates a positive out-of-plane tip deflection, which results in a positive out-of-plane bending moment at the root of the blade.

In normal operating conditions, it is expected that the thrust force on the blade will produce a positive out-of-plane tip deflection and a positive out-of-plane bending moment.