Final answer:
RNAV is a method used by aircraft to navigate, and a magnetic reference bearing provides a direction based on Earth's magnetic field lines.
Step-by-step explanation:
In the context of the question, RNAV refers to Area Navigation, which is a method used by aircraft to navigate using a combination of on-board navigation systems. One of the components of RNAV is the magnetic reference bearing.
A magnetic reference bearing is the direction indicated by a compass needle that aligns with the magnetic field lines of the Earth. It helps pilots navigate by providing a reference to the magnetic north pole.
For example, if an aircraft is flying and needs to follow a specific path, it can use the magnetic reference bearing to navigate accurately and maintain its intended route. Pilots need to account for variations in the Earth's magnetic field, such as magnetic declination, to ensure precise navigation.