There are very few perfectly rectangular wings and so a little manipulation is required in order to calculate the aspect ratio of a tapered wing.įigure 7: Calculation of the aircraft wing Aspect Ratio The aspect ratio is the ratio of the span of the wing to its chord. This is the area of the wing when viewed from directly above the aircraft.įigure 6: The planform wing area and aspect ratio of a tapered wing The wing area is defined as the planform surface area of the wing. Here we will briefly touch on two wing design variables: the planform wing area and the aspect ratio, which are two primary drivers behind the performance of a general aviation wing. You are encouraged to go and read through the posts on wing area and aspect ratio, sweep and airfoil aerodynamics if you are interested. In our Fundamentals of Aircraft Design series there are three posts dedicated to preliminary wing design. The strut may reduce the bending at the root but does produce more drag than an equivalent cantilevered wing.įigure 5: Braced Cessna 172 and cantilevered Cessna 210ĭesigning the planform or shape of a wing is a complicated process undertaken to optimize the aircraft for a particular mission. Many light aircraft make use of a strut which reduces the bending moment at the wing root, allowing a smaller (lighter) wing-to-fuselage attachment. Wings can be located above the fuselage (high wing), through the center of the fuselage (mid wing), or towards the bottom of the fuselage (low wing).įigure 4: Low wing Piper Seminole (top) and high wing Cessna CaravanĪ cantilevered wing has no external bracing and is connected to the fuselage only at the root. Number of WingsĪ triplane has three wings, a biplane two, and a monoplane the most common configuration in use today, has a single primary lifting surface.įigure 3: Boeing Stearman Bi-plane (top) and Piper PA-28 monoplane (bottom) We can broadly classify a wing-fuselage interface in terms of three design variables: the number of wings used to produce the required lift, the location of the wing, and the wing-fuselage attachment methodology. There are many different wing configurations in use today. While the magnitude of the drag force produced is a lot smaller than the lift, the structure must still be designed to support these forces at the limits of the design envelope. Induced drag is formed as a by-product of the lift generated, and along with profile drag introduce forces into the wing which tend to push the wing backward. The wing also tends to pitch up and down during flight which is reacted at the root by a torque at the attachment points.įigure 2: Lift distribution and wing bending moment The two primary contributors to the total stress are the vertical lift force and the resulting bending moment. The maximum wing loads are seen at the wing root where the wing attaches to the fuselage. Wing LoadsĪ wing is not designed to produce an equal upward force at all points along the span but rather produces the greatest percentage of the total lift closer to the root, diminishing outwards towards the span.įigure 1: Full span lift distribution on an aircraft The various components that make up the wing structure must be capable of supporting this aerodynamic load throughout the certified design envelope. Most general aviation aircraft are designed to a load factor of between four and six. This is termed the load factor and was discussed in part one of this series. Every wing is therefore designed to produce and support a multiple of the total weight of the airplane. IntroductionĪ wing is designed to produce sufficient lift to support the aircraft throughout its design envelope. This tutorial focuses on the structural design of an aircraft wing and introduces the various control surfaces attached to the wing’s trailing edge. This is part three in a five-part series on airframe structures and control surfaces.
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