This is part 5 in a series of fundamental aircraft design articles that aims to give you an introduction to aircraft design principles. In a previous post we looked at the importance of the shape and plan-form of the wing, and how this has a great impact on the flying characteristics of the aircraft. Specifically we looked at wing area and aspect ratio. In this post we look more closely at the shape of the wing airfoil: why this differs from aircraft to aircraft, and how a careful airfoil selection will help to produce the flying characteristics you desire for your airplane.
Aspect ratio is a measure of the ratio between the span of the wing to its chord. In most cases the wing chord is not equal along the length of the span which is why aspect ratio is most commonly calculated by dividing the square of the wing span by the reference wing area.
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See the image below which shows a number of fundamental definitions typically associated with airfoil nomenclature.
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Angle of attack refers to the angle between a reference line on a body and the vector representing the relative motion between the body and the fluid through which it is moving.
It is most often used in an aeronautical context to describe the angle between the chordline of an airfoil and the relative wind or resultant direction of airflow. In cases where a wing has twist, it is often taken as the angle between the chordline at the wing root and the relative wind.
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The calculator below can be used to display and extract coordinates of any NACA 5-series airfoil. The chord can be varied and either a blunt or sharp leading selected. The most common NACA 5-series airfoils are available from the drop-down menu; or alternatively you can design your own.
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