Basic Airfoil Terminology

| September 27, 2020 | By: Severe VFR
basic airfoil terminology title graphic

Understanding the wing or airfoil of an aircraft requires an understanding of the basic parts of an airfoil.

There are many dimensions and terminologies regarding an airfoil. The following locations on a wing and their definition are the basic building blocks for a more advanced understanding of an airfoil.

The Leading Edge and Trailing Edge

Airfoil leading edge and trailing edge graphic

The leading edge of an airfoil is the part of the wing that first meets oncoming air. The opposite of the leading edge is the trailing edge or rear part of the airfoil.

Some airfoils, such as the case for turbine propellers, do not define the leading edge as the part of the airfoil that first meets the oncoming air. Instead, the leading edge is defined as the area of minimum radius.

The position of the leading and trailing edge of an aircraft can be manipulated with the use of leading and trailing edge flaps, slots, or slats. Ailerons, elevators, and rudders can also affect the trailing edge position as they are manipulated in flight.

The Chord Line

chordline, upper surface, and lower surface explanation graphic

An airfoils chordline is an imaginary line connecting the leading edge to the trailing edge.

The chord line plays a significant role in determining the coefficient of lift a wing creates and is a component in determining the angle of attack as well as the aspect ratio of a wing.

Since the chord line connects the leading edge to the trailing edge, if a flight surface, such as a flap or aileron, changes the leading or trailing edge's position, then the chord line will change as well. This is most commonly seen with flaps changing the wing's chord line during takeoff and landing, allowing the wing to create more lift at slower airspeeds.

The chord line also marks the points where the upper surface and lower surface of the airfoil begin and end.

Camber, Thickness, and Mean Camber Line

airfoil mean camber line, upper camber, and lower camber explanation graphic

An aircrafts chord line rarely ever splits the airfoil, or wing, into two equal halves. Many airfoils are designed to have more area above the wing than under it. To have a greater area above the chord line, aircraft designers will add a much larger curve to the upper surface than the lower surface.

This curve, or camber, offers two benefits: greater lift and less drag.

A measure of the amount of curve an airfoil possesses is with the mean camber line. The mean camber line splits the wing into two halves of equal cross-sectional areas. These areas are labeled as the upper and lower camber.

The difference between the chord line and the mean camber line is the wings "camber." This camber changes on the wing from the leading edge to the trailing edge.

max camber, mean camber line, and chordline graphic

The location where the difference between the chord line and the mean camber line is the point of the wings maximum camber. The maximum camber can also be referred to as "the camber" because it is the only camber dimension of significance.

airfoil thickness explanation graphic

Another basic measurement for an airfoil is the airfoil's thickness. The thickness of an airfoil is simply the distance between the upper and lower surface. The thickness of most airfoils changes from the leading edge to the trailing edge.

Many wings also make the wing's thickness smaller as the wing works its way from the wing root to the wingtip.

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