Relative Wind

RELATIVE WIND
It doesn't take long for a student pilot studying basic aerodynamics to come upon a term so fundamental to piloting that understanding it unlocks the door to understanding many advanced principles of flight. The term is relative wind.

The glossary of the Pilot's Handbook of Aeronautical Knowledge defines relative wind as "the direction of the airflow with respect to the wing. If a wing moves forward horizontally, the relative wind moves backward horizontally. Relative wind is parallel to and opposite the flightpath of the airplane."

Sounds simple enough, but there are nuances. To visualize relative wind, you must understand the flight path of the aircraft. "As students, pilots learn that relative wind occurs opposite the direction of flight. That is not to be confused with the direction the nose is pointing.

Note that the safety advisor's illustration demonstrates how relative wind is used to diagram the aircraft's angle of attack—the source of lift. "Wings are able to create lift by accelerating air over their top surfaces, which are curved expressly for that purpose. As the oncoming air—called the relative wind—strikes a wing's leading edge, it splits and travels aft until meeting again at the trailing edge. The airfoil's curve guarantees that the air flowing over the top surface travels faster than the air passing beneath the wing.

Grasping relative wind is a simple step that will simplify your introduction to aerodynamics.