What is the term for the reference line that runs parallel to the wings of an aircraft?

The term for the reference line that runs parallel to the wings of an aircraft is known as the lateral axis. This axis is crucial in aviation, as it defines the direction in which the aircraft rotates around its pitch, which is controlled by the elevator on the tail of the aircraft. When the aircraft pitches up or down, it does so about the lateral axis, influencing the altitude and angle of attack.

In the context of aircraft axes, the lateral axis is perpendicular to both the longitudinal axis, which runs from the nose to the tail and is associated with roll movements, and the vertical axis, which extends vertically through the center of gravity and is related to yaw movements. Understanding the role of the lateral axis helps in grasping how an aircraft maneuvers and maintains stability during flight.