A 2D RNAV system provides guidance in?

A 2D RNAV (Area Navigation) system is designed to provide navigation guidance primarily in the horizontal plane. This means it focuses on defining the aircraft's position in relation to waypoints or routes laid out on a horizontal map or chart. The system uses positional information, such as coordinates derived from GPS or other navigation aids, allowing pilots to fly directly to a waypoint, regardless of the underlying ground features.

In contrast, vertical guidance, which involves altitude control and descents, falls into the realm of systems designated as 3D RNAV or those that provide vertical navigation (VNAV) capabilities. Therefore, the essence of a 2D RNAV system is its function in guiding the aircraft along specified flight paths without any reference to vertical flight profiles or altitudes. Understanding this distinction is crucial for interpreting how different navigation systems operate and the specific capabilities they offer to pilots in flight planning and execution.