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An ASH 31 glider with very high aspect ratio (AR=33.5) and lift-to-drag ratio (L/D=56) In aeronautics, the aspect ratio of a wing is the ratio of its span to its mean chord. It is equal to the square of the wingspan divided by the wing area. Thus, a long, narrow wing has a high aspect ratio, whereas a short, wide wing has a low aspect ratio. [1]
The ratio of the length (or span) of a rectangular-planform wing to its chord is known as the aspect ratio, an important indicator of the lift-induced drag the wing will create. [7] (For wings with planforms that are not rectangular, the aspect ratio is calculated as the square of the span divided by the wing planform area.)
The natural outcome of this requirement is a wing design that is thin and wide, which has a low thickness-to-chord ratio. At lower speeds, undesirable parasitic drag is largely a function of the total surface area, which suggests using a wing with minimum chord, leading to the high aspect ratios seen on light aircraft and regional airliners ...
In an airfoil, the mean line curvature is designed to change the flow direction, the vane thickness is for strength and the streamlined shape is to delay the onset of boundary layer separation. Taking all the design factors of an airfoil , the resulting forces of lift and drag can be expressed in terms of lift and drag coefficient.
It is measured empirically by testing in a wind tunnel or in free flight test. [1] [2] [3] The L/D ratio is affected by both the form drag of the body and by the induced drag associated with creating a lifting force. It depends principally on the lift and drag coefficients, angle of attack to the airflow and the wing aspect ratio.
A design approach used by Burt Rutan is a high aspect ratio canard with higher lift coefficient (the wing loading of the canard is between 1.6 and 2 times the wing one) and a canard airfoil whose lift coefficient slope is non-linear (nearly flat) between 14° and 24°. [36] Another stabilisation parameter is the power effect.
The ratio of the length of a nose cone compared to its base diameter is known as the fineness ratio. This is sometimes also called the aspect ratio, though that term is usually applied to wings and tails. Fineness ratio is often applied to the entire vehicle, considering the overall length and diameter.
For a thin airfoil of any shape the lift slope is π 2 /90 ≃ 0.11 per degree. At higher angles a maximum point is reached, after which the lift coefficient reduces. The angle at which maximum lift coefficient occurs is the stall angle of the airfoil, which is approximately 10 to 15 degrees on a typical airfoil.