![]() The maximum distance between the two lines is called the camber, which is a measure of the curvature of the airfoil (high camber means high curvature). But in most cases, the mean camber line and the chord line are two separate lines. For a symmetric airfoil the upper surface is a reflection of the lower surface and the mean camber line will fall on top of the chord line. If we plot the points that lie halfway between the upper and lower surfaces, we obtain a curve called the mean camber line. The chord line cuts the airfoil into an upper surface and a lower surface. The straight line drawn from the leading to trailing edges of the airfoil is called the chord line. This cross-section is called an airfoil, and it has some geometry definitions of its own as shown at the lower right. Airfoil GeometryĪ cut through the wing perpendicular to the leading and trailing edges will show the cross-section of the wing. The Wright brothers designed their 1903 flyer with a slight anhedral to improve the aircraft roll performance. Highly maneuverable fighter planes, on the other hand usually have the wing tips lower than the roots giving the aircraft a high roll rate. The wing tips are farther off the ground than the wing root. You may have noticed that most large airliner wings are designed with dihedral. Dihedral is added to the wings for roll stability a wing with some dihedral will naturally return to its original position if it encounters a slight roll displacement. The angle that the wing makes with the local horizontal is called the dihedral angle (if the tips are higher than the root) or the anhedral angle (if the tips are lower than the root). The front view of this wing shows that the left and right wing do not lie in the same plane but meet at an angle. A higher aspect ratio gives a lower drag, a higher lift to drag ratio, and a better glide angle. ![]() Gliders have a high aspect ratio because the drag of the aircraft depends on this parameter. High aspect ratio wings have long spans (like high performance gliders), while low aspect ratio wings have either short spans or thick chords (like the Space Shuttle). For a rectangular wing, this reduces to the ratio of the span to the chord length (c): AR = s^2 / A = s^2 / (s * c) = s / c Aspect ratio is a measure of how long and slender a wing is from tip to tip. The aspect ratio (AR) of a wing is defined to be the square of the span (s) divided by the wing area (A). The wing area is a projected area and is almost half of the total surface area. The total surface area includes both upper and lower surfaces. Note: The wing area is NOT the total surface area of the wing. The wing area is the projected area of the planform and is bounded by the leading and trailing edges and the wing tips. For most modern aircraft, the chord length varies along the span, and the leading and trailing edges may be swept. For a rectangular wing, the chord length at every location along the span is the same. The shape of the wing, when viewed from above looking down onto the wing, is called a planform. The ends of the wing are called the wing tips, and the distance from one wing tip to the other is called the span. The distance from the leading to trailing edges is called the chord. The front of the wing (at the bottom) is called the leading edge the back of the wing (at the top) is called the trailing edge. The top view shows a simple rectangular wing geometry, like that used by the Wright brothers. This airfoil is a modern, thick airfoil, which is slightly different from the thin airfoils used by the Wrights and shown below. The side view shows an airfoil shape with the leading edge to the left. The figure shows a wing viewed from three directions the upper left shows the view from the top looking down on the wing, the lower left shows the view from the front looking at the wing leading edge, and the right shows a side view from the left looking in towards the centerline. Actual aircraft wings are complex three-dimensional objects, but we will start with some simple definitions. ![]() This slide gives technical definitions of a wing’s geometry, which is one of the chief factors affecting airplane lift and drag. The terminology used here is used throughout the airplane industry today and was mostly known to the Wright brothers in 1900. ![]() Home > Beginners Guide to Aeronautics Wing Geometry ![]()
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