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A swept wing is a wing that angles either backward or occasionally forward from its root rather than in a straight sideways direction.
Swept wings have been flown since the pioneer days of aviation. Wing sweep at high speeds was first investigated in Germany as early asfinding application just before the end of the Second World War. It has the effect of delaying the shock waves and accompanying aerodynamic drag rise caused by fluid compressibility near the speed of soundimproving performance.
Swept wings are therefore almost always used on jet aircraft designed to fly at these speeds. Swept wings are also sometimes used for other reasons, such as low drag, low observability, structural convenience or pilot visibility. The term "swept wing" is normally used to mean "swept back", but variants include forward sweepvariable sweep wings and oblique wings in which one side sweeps forward and the other back. The delta wing is also aerodynamically a form of swept wing.
For a wing of given span, sweeping it increases the length of the spars running along it from root to tip. This tends to increase weight and reduce stiffness.
Aspect ratio (aeronautics)
If the fore-aft chord of the wing also remains the same, the distance between leading and trailing edges reduces, reducing its ability to resist twisting torsion forces. A swept wing of given span and chord must therefore be strengthened and will be heavier than the equivalent unswept wing. A swept wing typically angles backward from its root rather than forwards. Because wings are made as light as possible, they tend to flex under load.
This aeroelasticity under aerodynamic load causes the tips to bend upwards in normal flight. Backwards sweep causes the tips to reduce their angle of attack as they bend, reducing their lift and limiting the effect.
Forward sweep causes the tips to increase their angle of attack as they bend. This increases their lift causing further bending and hence yet more lift in a cycle which can cause a runaway structural failure. For this reason forward sweep is rare and the wing must be unusually rigid.
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Typical sweep angles vary from 0 for a straight-wing aircraft, to 45 degrees or more for fighters and other high-speed designs. As an aircraft enters the transonic speeds just below the speed of sound, the pressure waves associated with subsonic flight converge and begin to impinge on the aircraft.
As the pressure waves converge the air in front of the aircraft begins to compress. This creates a force known as wave drag.This slide gives technical definitions of a wing's geometry, which is one of the chief factors affecting airplane lift and drag. The terminology is used throughout the airplane industry and is also found in the FoilSim interactive airfoil simulation program developed here at NASA Glenn.
Actual aircraft wings are complex three-dimensional objects, but we will start with some simple definitions. The figure shows the wing viewed from three directions; the upper left shows the view from the top looking down on the wing, the lower right shows the view from the front looking at the wing leading edge, and the lower left shows a side view from the left looking in towards the centerline.
The side view shows an airfoil shape with the leading edge to the left. Top View The top view shows a simple wing geometry, like that found on a light general aviation aircraft. 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 distance from the leading edge to the trailing edge is called the chorddenoted by the symbol c. The ends of the wing are called the wing tipsand the distance from one wing tip to the other is called the spangiven the symbol s. The shape of the wing, when viewed from above looking down onto the wing, is called a planform.
In this figure, the planform is a rectangle. For a rectangular wing, the chord length at every location along the span is the same. For most other planforms, the chord length varies along the span.
The wing area, A, is the projected area of the planform and is bounded by the leading and trailing edges and the wing tips. Note: The wing area is NOT the total surface area of the wing.
The total surface area includes both upper and lower surfaces. The wing area is a projected area and is almost half of the total surface area.
Aspect ratio is a measure of how long and slender a wing is from tip to tip. The Aspect Ratio of a wing is defined to be the square of the span divided by the wing area and is given the symbol AR. For a rectangular wing, this reduces to the ratio of the span to the chord length as shown at the upper right of the figure.
High aspect ratio wings have long spans like high performance gliderswhile low aspect ratio wings have either short spans like the F fighter or thick chords like the Space Shuttle.
There is a component of the drag of an aircraft called induced drag which depends inversely on the aspect ratio. A higher aspect ratio wing has a lower drag and a slightly higher lift than a lower aspect ratio wing.Concept of Wing Aspect Ratio - - GATE Aerospace Engineering
Because the glide angle of a glider depends on the ratio of the lift to the drag, a glider is usually designed with a very high aspect ratio. The Space Shuttle has a low aspect ratio because of high speed effects, and therefore is a very poor glider. The F and F have the best of both worlds. They can change the aspect ratio in flight by pivoting the wings--large span for low speed, small span for high speed.
Front View 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. The angle that the wing makes with the local horizontal is called the dihedral angle.
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. You may have noticed that most large airliner wings are designed with diherdral. The wing tips are farther off the ground than the wing root.The aspect ratio of a geometric shape is the ratio of its sizes in different dimensions. The aspect ratio is most often expressed as two integer numbers separated by a colon x:yless commonly as a simple or decimal fraction.
The values x and y do not represent actual widths and heights but, rather, the proportion between width and height. As an example, 1. In objects of more than two dimensions, such as hyperrectanglesthe aspect ratio can still be defined as the ratio of the longest side to the shortest side. For a rectangle, the aspect ratio denotes the ratio of the width to the height of the rectangle.
A square has the smallest possible aspect ratio of For an ellipse, the aspect ratio denotes the ratio of the major axis to the minor axis. An ellipse with an aspect ratio of is a circle.
In geometrythere are several alternative definitions to aspect ratios of general compact sets in a d-dimensional space: . If the dimension d is fixed, then all reasonable definitions of aspect ratio are equivalent to within constant factors.
Cinematographic aspect ratios are usually denoted as a rounded decimal multiple of width vs unit height, while photographic and videographic aspect ratios are usually defined and denoted by whole number ratios of width to height. In digital images there is a subtle distinction between the display aspect ratio the image as displayed and the storage aspect ratio the ratio of pixel dimensions ; see Distinctions.
From Wikipedia, the free encyclopedia. For other uses, see Aspect ratio disambiguation. Main article: Aspect ratio image. Retrieved 3 February Fractions and ratios.
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When designing an aircraft, there has to be a decision as to the aspect ratio of a wing. It's been said that having a higher aspect wing will reduce drag for the same wing area, however most of the time wings are shorter than they can be.
So my question is, what exactly dictates the aspect ratio of a wing, and why don't they make them as long as possible? Aspect ratio is the ratio based on the span and chord of an aircraft's wings. The span is the length of the wings measured wingtip to wingtip; the chord is the 'depth' of the wing from the leading edge to the trailing edge, measured in a straight line. Because very few aircraft have constant chord planforms, this requires a not-very-fancy formula to calculate source: NASAso that we can effectively average the chord:.
Math aside, aspect ratio is chosen based on an aircraft's role or requirements. A need for agility dictates a low aspect ratio, as does a need for compactness. In both cases, fighter aircraft and bush aircraft benefit from agility and small size. High aspect ratios provide great cruise efficiency but can have poor landing characteristics high drag at low speeds or high angles of attack due to frontal area that are often offset by high-lift devices like flaps and slats.
To the second half of your question: even when a high aspect ratio is desired, wings are not made as long as possible for two reasons. The first is structural; the bending forces associated with wings of extreme length are, well, extreme, and the materials required are pretty space-age. See high-performance gliders, or at the crazy end, solar- or human-powered aircraft, for examples of this.
It's just hard to do at the size of an airliner. The second reason is more practical: space is expensive. An extremely high-aspect ratio wing takes up a ton of space relative to the rest of the aircraft. In an attempt to offset this, early s which had a larger span than s and s were offered with folding wingtips, but nobody bought that option and it got dropped. Increasing the aspect ratio of a wing will not change its induced drag. Increasing the span will. Now let's look at the real numbers and compare two wings of the same span, but different aspect ratios.
For simplicity, wing 1 has an AR of 5 and wing 2 has an AR of Let's further assume that both wings have the same mass. Since both wings have the same span, wing 1 has twice the wing area of wing 2. To create the same lift, wing 1 needs only half the lift per area than wing 2! To reduce induced drag requires a span increase, regardless of aspect ratio. In the end, the wing chord is chosen to minimize wing mass and to yield the minimum required fuel volume, and the aspect ratio is just a consequence of the selected wing span.
To answer your question it's maybe helpful to remember why a higher aspect ratio generates less drag. A higher aspect ratio causes less induced drag at the same lift than an aerofoil with a lower aspect ratio. Okay, we need a certain amount of lift and our aim is to gain this lift as efficient as possible.The weight W of the aircraft and its aerodynamic properties are the primary factors determining its flight performance.
It is not simply a matter of adding the components together to obtain a final answer for the aircraft weight. For example it may be necessary to remove fuel weight so that additional payload may be carried while still maintaining the requirement of a maximum take-off weight. For stability and hence flight safety considerations an accurate "weight and balance" calculation should be performed prior to the flight of the aircraft.
In flight the aircraft weight will change as fuel is burnt by the propulsion system or possibly dumped in an emergency situation. All the weight specifications will need to be identified from data given by the aircraft manufacturer before force equilibrium calculations can be applied.
Aircraft Geometry. A typical aircraft planform layout is shown below. The wing planform area S is shaded as shown. The wing taper ratio can be calculated as the ratio of tip chord to root chord, The mean aerodynamic chord can be found by integrating the individual section chords across the span.
Lift and Lift Coefficient The aircraft generates lift by moving quickly through the air. The wings of the vehicle have aerofoil shaped cross-sections and for the given flow conditions the aerofoil shapes will create a pressure difference between upper and lower wing surfaces.
There will be a high pressure region underneath and a very low pressure region on top. The lift produced will be proportional to the size of the aircaft; the square of its velocity; the density of the surrounding air and the angle of attack of the wing to on-coming flow.
To simplify the problem, lift is typically measured as a non-dimensional coefficient. In the normal range of operations the variation of lift coefficent with angle of attack of the vehicle will be approximately linear, up until a maximum lift coefficient value at which point the wing flow stalls and lift reduces.
The values of the lift curve gradient and maximum lift coefficient are effected by the shape of the wing, its twist distribution, the type of aerofoil section used, the flap configuration and most importantly by the amount of downwash flow induced on the wing by the trailing wing tip vortices. A simple approximation for straight, moderate to high aspect ratio wings is to assume an elliptical spanwise load distribution which gives the following result, where it is assumed that the ideal two-dimensional result for the section used is.
Calculation of zero angle lift coefficient or zero lift angle can be done by crudely assuming that the zero lift angle for the aircraft equals the combination of zero lift angle of the aerofoil section and wing incidence setting. For swept wings, wings with complex taper or wings with flaps, a more accurate calculation needs to be undertaken using either lifting line theory or the vortex lattice method.
Drag and Drag Coefficient In moving through the air the aircraft experiences a resistive drag force. For the more complex flows obtained in the transonic and supersonic regions, CFD analysis or experimental data is required to correctly estimate C D. The lift dependant component can be approximated as where e is the wing planform efficiency factor.
Values for these drag constants for various categories of aircraft are shown in the following table. Thrust to overcome drag is produced by engines generally using one of the following configurations, a Reciprocating Piston Engine driving a propeller.
For cases a and b engine horsepower performance data will be provided from the engine manufacturer. To find thrust, a reasonable estimate of propeller efficiency is required. Propeller efficiency can be measured against advance ratio, the ratio of forward to rotational speed of the propeller. A typical fixed pitch propeller performance graph will be as follows, For detailed methods of calculating propeller performance see the chapter on Blade Element Theory.
By using a constant speed unit on the engine and thus varing the pitch in flight it is possible to maintain high efficiency for a range of advance ratios. The constant speed units typically have a fixed range of pitch change so that again below take-off speed and above high speed cruise the propeller efficiency will rapidly decline.
More advanced turbo-prop units have a greater pitch range including the options of reverse thrust and feathered aligned with airflow, min drag with no rotation positions. Given information regarding the propeller efficiency, the engine horsepower output and the speed of the vehicle, thrust produced by the propeller can be predicted by.
Aircraft Type.Average wing chord for a tapered wing is the root chord plus the tip chord divided by two. For a constant chord wing, the average chord is the chord anywhere along the wing panel. The Aspect Ratio of a wing is an indicator of the aircraft's roll response. All else being equal, high aspect ratio wings narrow chord to span will have a slower roll response than a low aspect ratio wing.
The Aspect Ratio of a flying surface largely determines the lift to drag ratio of the surface. High aspect ratio wings, such as on sailplanesare more efficient and have a higher lift to drag ratio. High aspect ratio wings are more easily broken and are less tolerant of poor engineering, poor building and flight outside design parameters.
There are two ways to calculate the Aspect Ratio of a flight surface. Divide the wing span by the average wing chord. For example, if the root chord is 12" and the tip chord is 8", then the average chord is 10" assuming a straight tapered wing. Let's say the wing span is 50". Divide the span by the average chord to determine the aspect ratio:. Square the wing span and divide by the wing area. This is helpful for wings where determining the average chord would be difficult such as elliptical wings.
You can also trace this information backwards to find the average chord of a wing. Simply divide the wing area by the wing span. May 05, Method 1 Divide the wing span by the average wing chord.
Previous — Next —. Comments about this article. Back to Formulas Airfield Models Home.Wing shapes and sizes of both birds and planes determine how they might perform or what they might be capable of for example, gliding, sustained high speed and manoeuvrability. One way in which the shape of the wing can be described is through wing aspect ratio. The ratio of the length of wings to their width is called aspect ratio.
A high aspect ratio indicates long, narrow wings. A low aspect ratio indicates short, wide wings. Generally, high aspect ratio wings give slightly more lift and enable sustained, endurance flight, while low aspect ratio wings are best for swift manoeuvrability.
Stability: Long narrow wings give a plane or bird more stability. Less induced drag Long, narrow wings also have less induced drag than shorter wider wings.
Induced drag is created at the tips of the wings where the high pressure air from beneath the wing comes up over the wing tips into the low pressure zone. This meeting place of different air pressures becomes a turbulent area creating induced drag.
Long narrow wings have less end edges tips and more stable wing area than shorter wider wings so they have less drag. Less fuel consumption: Having less induced drag means there is less fuel consumption for planes and birds fat consumption so they can keep their speed for a longer time than short wide-winged fliers.
Higher fuel consumption: Shorter wider-winged planes and birds have a bigger wing tip edge, which means more induced drag. This means they go slower unless they have extra power to counteract the drag. More fuel would be needed to keep them at a constant speed. More manoeuvrable: The less stable wing area means the low aspect ratio wing is more manoeuvrable than the high aspect ratio wing.
The peregrine falcon, for example, tucks its wings in producing a low aspect ratio for swift manoeuvrability. Aspects ratios and wing loading are combined for different flying capabilities. For example, high aspect ratio combined with low wing loading is used for slow flight such as gliding or soaring. Read our latest newsletter online here. Activity ideas Continue the learning with your students with one or more of these activities Birds and planes — explore the importance of wing shape and size and how this determines the flight capabilities of birds and planes.
Aerofoils and paper planes — learn how to make an aerofoil and to make and fly paper planes.
How Does Aspect Ratio Affect Your Wing?
Making a glider — handcraft a glider from balsa wood and in the process learn about aerofoil wing shape, glider parts and terminology. Then experiment with flight using variables of wind and nose weight. Twitter Pinterest Facebook Instagram. Email Us. Would you like to take a short survey? This survey will open in a new tab and you can fill it out after your visit to the site.