Cayley made essential observations about drag, including “It has been found by experiment that the shape of the hinder part of the spindle is of as much importance as that of the front in diminishing resistance.” Cayley referred to the shape of a wing as spindle-shaped. Sir George Cayley, often revered as the “Father of Aeronautics,” delineated the problem of sustentation, i.e., aerodynamic lift, from that of drag, i.e., the component of aerodynamic resistance. In this regard, theory and experimentation (e.g., wind tunnel testing) have been used to design airfoils to meet specific operating requirements for different aircraft types, including low-speed airplanes, high-speed airplanes, helicopters, propellers, wind turbines, etc. Historically, the most suitable airfoils for most practical engineering applications were obtained through an evolutionary process. Understand the differences in the shapes between subsonic, transonic, and supersonic airfoil sections.Know how to construct a NACA airfoil profile geometrically using a camberline shape and a thickness envelope.Be able to identify and explain the significance of the critical geometric parameters that define the shape of an airfoil.Appreciate the historical evolution of airfoil sections for aircraft applications.Historically, the design of airfoil shapes for specific applications has proceeded evolutionarily, with wind tunnel experiments, theoretical analysis, and flight testing all being used synergistically to develop the best airfoil shapes for application to specific flight vehicles. Airfoils for high-speed aircraft, especially for supersonic flight, are much thinner with more pointed leading edges and much less camber. To this end, not all airfoils are created equally, and different airfoil shapes will be better suited for one application versus another.įor example, airfoils for use on the wings of low-speed airplanes are generally thicker (in terms of their thickness-to-chord ratio) and have more surface curvature or camber. Aerospace engineers must know how to select or design suitable cross-sectional wing shapes (often called airfoil profiles or airfoils) for use on a diverse range of flight vehicles such as subsonic, transonic, and supersonic airplanes, various types of space launch vehicles, as well as helicopter rotors, propeller blades, wind turbines, UAVs, etc.
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