Wing Planform   The previous discussions on wings have dealt only with airfoil section properties and two dimensional airflow. Wing planform - the shape of the wing as viewed from directly above - deals with airflow in three dimensions, and is very important to understanding wing performance and airplane flight characteristics. Aspect ratio, taper ratio, and sweepback are factors in planform design that are very important to the overall aerodynamic characteristic of a wing (Fig. 17-13).

   Aspect ratio is the ratio of wing span to wing chord.

Taper ratio can be either in planform or thickness, or both. In its simplest terms, it is a decrease from wing root to wingtip in wing chord or wing thickness.

   Sweepback is the rearward slant of a wing, horizontal tail, or other airfoil surface.

 There are two general means by which the designer can change the planform of a wing, either of which will affect aerodynamic characteristics of the wing. The first is to effect a change in the aspect ratio. Aspect ratio is the primary factor in determining the three dimensional characteristics of the ordinary wing and its lift/drag ratio. An increase in aspect ratio with constant velocity will decrease the drag, especially at high angles of attack, improving the performance of the wing when in a climbing attitude.

   A decrease in aspect ratio will give a corresponding increase in drag. It should be noted, however, that with an increase in aspect ratio there is an increase in the length of span, with a corresponding increase in the weight of the wing structure, which means the wing must be heavier to carry the same load. For this reason, part of the gain (due to a decrease in drag) is lost because of the increased weight, and a compromise in design is necessary to obtain the best results from these two conflicting conditions. The second means of changing the planform is by "tapering" (decreasing the length of chord from the root to the tip of the wing). In general, tapering will cause a decrease in drag (most effective at high speeds) and an increase in lift. There is also a structural benefit due to a saving in weight of the wing.

   Most training and general aviation type airplanes are operated at high lift coefficients, and therefore require comparatively high aspect ratios. Airplanes which are developed to operate at very high speeds demand greater aerodynamic cleanness, and greater strength - therefore low aspect ratios. Very low aspect ratios result in high wing loadings and high stall speeds. When sweepback is combined with low aspect ratio, it results in flying qualities very different from a more "conventional" high aspect ratio airplane configuration. Such airplanes require very precise and professional flying techniques, especially at slow speeds, while airplanes with a high aspect ratio are usually more forgiving of improper pilot techniques.

   The elliptical wing is the ideal subsonic planform since it provides for a minimum of induced drag for a given aspect ratio, though as we shall see, its stall characteristics in some respects are inferior to the rectangular wing. It is also comparatively difficult to construct. The tapered airfoil is desirable from the standpoint of weight and stiffness, but again is not as efficient aerodynamically as the elliptical wing. In order to preserve the aerodynamic efficiency of the elliptical wing, rectangular and tapered wings are sometimes "tailored" through use of wing twist and variation in airfoil sections until they provide as nearly as possible the elliptical wing's lift distribution.

   While it is true that the elliptical wing provides the best lift coefficients before reaching an incipient stall, it gives little advance warning of a complete stall, and lateral control may be difficult because of poor aileron effectiveness.

   In comparison, the rectangular wing has a tendency to stall first at the wing root and provides adequate stall warning, adequate aileron effectiveness, and is usually quite stable. It is, therefore, favored in the design of low cost, low speed airplanes.

Stall progression patterns for various wing planforms are graphically depicted in Figure 17-13. Note that it is possible for the trailing edge of the inboard portion of the rectangular wing to be stalled while the rest of the wing is developing lift. This is a very desirable characteristic, and along with simplicity of construction is the reason why this type of wing is so popular in light airplanes, despite certain structural and aerodynamic inefficiencies.

  The modern aircraft has five basic structural components: fuselage, wings, empennage (tail structures), power plant (propulsion system) and the undercarriage.

The fuselage is the main body structure to which all other components are attached. The fuselage contains the cockpit or flight deck, passenger compartment and cargo compartment. While wings produce most of the lift, the fuselage also produces a little lift. A bulky fuselage can also produce a lot of drag. For this reason, a fuselage is streamlined to decrease the drag.

We usually think of a streamlined car as being sleek and compact - it does not present a bulky obstacle to the oncoming wind. A streamlined fuselage has the same attributes. It has a sharp or rounded nose with sleek, tapered body so that the air can flow smoothly around it.

The wings are the most important lift-producing part of the aircraft. Wings vary in design depending upon the aircraft type and its purpose. Most airplanes are designed so that the outer tips of the wings are higher than where the wings are attached to the fuselage. This upward angle is called the dihedral and helps keep the airplane from rolling unexpectedly during flight. Wings also carry the fuel for the airplane.

All planes have wings. The wings are shaped with smooth surfaces. There is a curve to the wings which helps push the air over the top more quickly than it goes under the wing. As the wing moves, the air flowing over the top has farther to go and it moves faster than the air underneath the wing. So the air pressure above the wing is less than below it. This produces the upward lift. The shape of the wings determines how fast and high the plane can fly. Wings are called airfoils. The hinged control surfaces are used to steer and control the airplane.

The flaps and ailerons are connected to the backside of the wings. The flaps slide back and down to increase the surface of the wing area. They also tilt down to increase the curve of the wing. The slats move out from the front of the wings to make the wing space larger. This helps to increase the lifting force of the wing at slower speeds like takeoff and landing.

The ailerons are hinged on the wings and move downward to push the air down and make the wings tilt up. This moves the plane to the side and helps it turn during flight. After landing, the spoilers are used like air brakes to reduce any remaining lift and slow down the airplane.

Aripa

În zborul aerodinamic, bazat pe forța portantă, cea mai importantă parte a avionului este aripa. Împreună un ampenajele, aripa asigură sustentația, stabilitatea și manevrabilitatea avionului. În general aripa este compusă din structura de rezistență, înveliș exterior, rezervoarele integrate de combustibil, aparatura hidro-pneumatică aferentă comenzilor. Sub aripă se instalează trenul principal de aterizare al avionului, sistemul de propulsie, acroșaje speciale rachete, bombe sau rezervoare lărgabile.

Forma în plan a aripii este extrem de diversificată, în funcție de destinația, rolul, dimensiunile, forma sau viteza avionului: aripa dreaptă (An-2, Cessna 172), aripă trapezoidală (F-22 Raptor), aripă în săgeată (A300, BAC 1-11, Su-27), aripă în săgeată cu geometrie variabilă (Tornado, B-1), aripă triunghiulară (F-16, Saab-37 Viggen), aripă delta gotic (Concorde), etc.

Triplan Fokker Dr.I

Biplan Pitts S1s

Biplan An-2 cu aripă dreaptă

F-22:aripă trapezoidală

Su-27 in aerobatics show.jpg

Su-27:aripă în săgeată

F-111:aripă în săgeată cu geometrie variabilă

Concorde:aripă delta gotic

Elementele constructive ale unei aripi de avion obișnuite sunt: lonjeroanele, lisele, nervurile, panourile de înveliș și alte piese componente, de rigidizare (ex: montanți) folosite pentru transmiterea eforturile între aripă și fuzelaj sau între tronsoanele aripii.

Aripile cu cel puțin două lonjeroane împreună cu învelișul formează chesonul de rezistență, care are sarcina de a prelua eforturile aerodinamice și mecanice la care este supusă aripa.

Cheson de rezistență

Componentele principale ale chesonului

Lonjeroanele sunt elemente de rigidizare așezate de-a lungul aripii, care preiau cea mai mare parte din forțele și momentele ce acționează asupra acesteia. Au aspectul unei grinzi consolidate alcătuite din tălpi (profile corniere) și inimă (platbandă), îmbinate între ele cu nituri. Sunt realizate de regulă din materiale rezistente la încovoiere și răsucire: duraluminiu, titan, oțeluri speciale.

Nervurile sunt elemente de rigidizare transversală a aripii, montate de obicei perpendicular pe bordul de atac al aripii. Nervurile au rolul de a păstra forma aripii și de a transmite solicitările aerodinamice la lonjeroane și lise. Pot fi nervuri simple sau nervuri de forță, acestea din urmă având rolul suplimentar de a prelua forțele concentrate datorate diverselor echipamente și instalații acroșate de aripi.

Lisele sunt elemente de rigidizare montate în lungul aripii cu rolul de a prelua solicitările axiale datorate încovoierii aripii. Ele trebuie să fie rezistente la întindere și compresiune și măresc rezistența învelișului la deformație. Sunt obținute tehnologic prin extrudare sau îndoire și sunt alcătuite din duraluminiu, aliaje pe bază de titan sau oțel inoxidabil.

Învelișul aripii are rolul de a menține forma sa și este realizat din tablă de duraluminiu sau aliaje pe bază de titan, magneziu etc. Învelișul este solicitat la eforturi de încovoiere și răsucire. Ele este prins de celelalte elemente prin nituri. Dacă distanța dintre lise este mică se folosește pentru rigidizarea învelișului tablă ondulată. Îmbinarea tablei ondulate cu invelișul se poate face prin metoda suduri, nu prin nituire. Dacă aripa are grosime mică, învelișul se poate realiza prin panouri monolit. Construcția unei astfel de aripi se realizează prin îmbinarea panourilor dintr-o singură bucată. La aripile cu grosime foarte mică, spațiul interior nu mai cuprinde elemente de rigidizare, ci este umplut cu structură de tip fagure sau cu alt material compozit, rezultând o structură compactă, cu rezistență mecanică mare.

[modificare] Fuzelajul

Fuzelajul (din franceză fuselage) este partea aeronavei în care este plasată cabina piloților, cabina pasagerilor, încărcătura de transport și cea mai mare parte a echipamentelor și instalațiilor de bord. El reprezintă corpul central de care se leagă aripa, ampenajele și trenul de aterizare. Fuzelajul trebuie să aibă o rezistență la înaintare minimă. De aceea forma sa trebuie să fie aerodinamică, să aibă cât mai puține proeminențe, suprafața "spălată" de curentul de aer să fie bine finisată și cu cât mai puține ondulații.

Fuzelajele tip cocă sunt cele mai folosite în prezent în construcția aerospațială, ele s-au impus definitiv odată cu apariția motoarelor turboreactoare. Elementele principale ale fuzelajelor de tip cocă sunt: structura longitudinală formată din lonjeroane și lise, structura transversală formată din cadre, și învelișul rezistent.

Structura fuzelajului

Se folosesc în prezent la aeronave două tipuri de fuzelaje tip cocă:

semimonococă cu structură formată din lonjeroane puternice și dintr-o rețea rară de lise și înveliș subțire

semicocă, structura constând dintr-o rețea deasă de lise, lonjeroane false (lise rigidizate) și înveliș subțire.

Fuzelajele tip cocă sunt rigidizate cu ajutorul unor pereți și podele care formează împreună cu restul structurii diverse compartimente folosite pentru amplasarea echipamentelor și instalațiilor de bord, pentru depozitarea încărcăturii de transport.

[modificare] Ampenajele

Structura unui ampenaj orizontal văzut "de sus"

Ampenajele sunt elemente care reprezintă pentru aeronavă organele de echilibru, stabilitate și comandă. După modul cum sunt construite depinde în mare măsură capacitatea de manevră a aeronavei. Se compun de regulă din ampenajul orizontal format din stabilizator (partea fixă) și profundor (partea mobilă) și ampenajul vertical format din direcție (partea fixă) și derivă (partea mobilă). La aeronavele supersonice se instalează câteodată două ampenaje verticale, iar stabilizatorul are numai parte mobilă, fiind realizat dintr-o singură bucată. În configurația clasică stabilizatorul este plasat în spatele aripii, dar la avioanele de vânătoare moderne poate apare în fața sa, rezultând așa-zisa configurație "canard" (rață) (de exemplu la Eurofighter).

Eurofighter:stabilizator configuraţie "canard" (raţă)

Se observă diferenţa dintre avionul-cisternă KC-10 Extender cu ampenaje standard şi bombardierul fără ampenaje (BWB - Blended Wing Body) B-2 Spirit

La alte avioane moderne ambele ampenaje pot lipsi, aripa preluând în totalitate rolurile de stabilizare și comandă (de exemplu la B-2) prin folosirea suprafețelor de comandă numite elevoane.

Construcția ampenajelor respectă în general schemele de construcție ale aripii.

WingsThe wings are airfoils attached to each side of the fuselage and are the main lifting surfaces that support the airplane in flight. There are numerous wing designs, sizes, and shapes used by the various manufacturers. Wings may be attached at the top, middle, or lower portion of the fuselage. These designs are referred to as high-, mid-, and low-wing, respectively. The number of wings can also vary. Airplanes with a single set of wings are referred to as monoplanes, while those with two sets are called biplanes.

The principal structural parts of the wing are spars, ribs, and stringers. These are reinforced by trusses, I-beams, tubing, or other devices, including the skin. The wing ribs determine the shape and thickness of the wing (airfoil). In most modern airplanes, the fuel tanks either are an integral part of the wing’s structure, or consist of flexible containers mounted inside of the wing.

Attached to the rear or trailing edges of the wings are two types of control surfaces referred to as ailerons and flaps. Ailerons extend from about the midpoint of each wing outward toward the tip, and move in opposite directions to create aerodynamic forces that cause the airplane to roll. Flaps extend outward from the fuselage to near the midpoint of each wing. The flaps are normally flush with the wing’s surface during cruising flight. When extended, the flaps move simultaneously downward to increase the lifting force of the wing for takeoffs and landings.

________

An airplane in flight is the center of a continuous tug of war between four forces: lift, gravity force or weight, thrust, and drag. Lift and Drag are considered aerodynamic forces because they exist due to the movement of the aircraft through the air.  The weight pulls down on the plane opposing the lift created by air flowing over the wing. Thrust is generated by the propeller and opposes drag caused by air resistance to the frontal area of the airplane. During take off, thrust must overcome drag and lift must overcome the weight before the airplane can become airborne. In level flight at constant speed, thrust exactly equals drag and lift exactly equals the weight or gravity force. For landings thrust must be reduced below the level of drag and lift below the level of the gravity force or weight.

 

Lift

Lift is produced by a lower pressure created on the upper surface of an airplane's wing compared to the pressure on the wing's lower surface, causing the wing to be "lifted" upward. The special shape of the airplane wing (airfoil) is designed so that air flowing over it will have to travel a greater distance faster, resulting in a lower pressure area (see illustration) thus lifting the wing upward. Lift is that force which opposes the force of gravity (or weight).

Who invented it?

Many people tried to invent a wing that would let people fly. Even the famous inventor, Leonardo da Vinci drew up plans for different ways of flying with wings like a bird. The first wing that let a person fly was in ancient China in the year 559. It was really just a large kite. In 877, long before Marco Polo and other explorers brought back information about Chinese kites to Europe, an Arab inventor in Spain named Abbas Ibn Firnas made the first hang glider, and tested it himself.

Sir George Cayley and later Otto Lilienthal created working gliders that allowed people to fly as long ago as the 1800s. The Wright Brothers were famous for the airplane that they first demonstrated in 1903 in Kitty Hawk, North Carolina, but their airplane's wings worked in the same way as Otto Lilienthal's glider wings from 1891.

[edit] How does it get power?

The only power that a wing needs is to be moved forward through the air. In a glider the wing is either pushed to get it started, or it is brought somewhere high up and dropped, like a hang glider pilot starting from the top of a cliff. In a powered airplane, the engines either push or pull the wings through the air.

The shape and positioning of a wing is very important. Most wings are curved, which makes the air going over them go faster than the air going under them. Because the air above the wing moves faster, it is more spread out than the air below the wing. Air presses on everything around it, even though you can't feel it. When there is more air it pushes more on the things around it. The fast-moving, spread-out air over the top of the wing lets the air on the bottom of the wing push the wing up, creating lift.

Another way to think of it is that the wing of an airplane is usually tilted so that the front is higher than the back. The air that follows the upper and lower surfaces of the wing is directed downward by the wing's shape and tilt. This creates an opposing upward lifting force on the wing itself. It is the lift from the wings that carries a plane through the air.

[edit] How dangerous is it?

Airplane wings are not dangerous. Airplanes themselves have a good safety record when they are well maintained. There are risks with any travel and planes travel at high speeds. However, nowadays air travel is so safe that you are more likely to get killed driving to the airport than you are flying on the plane!

[edit] What does it do?

A commercial airplane landing. The flaps on the trailing edge of the wing are fully extended in landing position.

A wing is a part of airplane that lifts it up. There are mainly four forces acting on airplane while in air. Wings provide the force to the airplane that takes it up against the force of gravity due to earth. An airplane wing is specially designed so that air that passes around it actually helps lift up the plane. It is also streamlined in shape so that the plane can move at maximum speed.

[edit] How does it vary?

All airplane wings contain flaps to increase lift and drag. Some airplane wings, especially those of larger jets, have spoilers that will further slow down the airplane. This is important in landing, where one must land at the slowest speed possible without stalling and then stop the airplane's movement as quickly as possible.

In larger airplanes the wings often have the engines fixed onto them.

[edit] How has it changed the world?

An airplane wing is one of the most fundamental things that allow a plane to fly. Without it, a plane does not fly and it has brought planes all over the world.

[edit] What idea(s) and/or inventions had to be developed before it could be created?

The first plane had to be invented before any experimentation with the wing could occur. The earliest wings were simply light framed wooden planks, with no such inbuilt drag or lift functions.

 To maintain its all-important aerodynamic shape, a wing must be designed and built to hold its shape even under extreme stress. Basically, the wing is a framework composed chiefly of spars, ribs, and (possibly) stringers (see figure 1-5). Spars are the main members of the wing. They extend lengthwise of the wing (crosswise of the fuselage). All the load carried by the wing is ultimately taken by the spars. In flight, the force of the air acts against the skin. From the skin, this force is transmitted to the ribs and then to the spars.

   Most wing structures have two spars, the front spar and the rear spar. The front spar is found near the leading edge while the rear spar is about two-thirds the distance to the trailing edge. Depending on the design of the flight loads, some of the all-metal wings have as many as five spars. In addition to the main spars, there is a short structural member which is called an aileron spar.

   The ribs are the parts of a wing which support the covering and provide the airfoil shape. These ribs are called forming ribs. and their primary purpose is to provide shape. Some may have an additional purpose of bearing flight stress, and these are called compression ribs.

   The most simple wing structures will be found on light civilian aircraft. High-stress types of military aircraft will have the most complex and strongest wing structure.

   Three systems are used to determine how wings are attached to the aircraft fuselage depending on the strength of a wing's internal structure. The strongest wing structure is the full cantilever which is attached directly to the fuselage and does not have any type of external, stress-bearing structures. The semicantilever usually has one, or perhaps two, supporting wires or struts attached to each wing and the fuselage. The externally braced wing is typical of the biplane (two wings placed one above the other) with its struts and flying and landing wires (see figure 1-6).

-___________________

The spar is often the main structural member of the wing, running spanwise at right angles (or thereabouts depending on wing sweep) to the fuselage. The spar carries flight loads and the weight of the wings whilst on the ground. Other structural and forming members such as ribs may be attached to the spar or spars, with stressed skin construction also sharing the loads where it is used. There may be more than one spar in a wing or none at all. However, where a single spar carries the majority of the forces on it, it is known as the main spar.

Spars are also used in other aircraft aerofoil surfaces such as the tailplane and fin and serve a similar function, although the loads transmitted may be different to those of a wing spar.

In the framework of a wing, ribs are the crosspieces running from the leading edge to the trailing edge of the wing. The ribs give the wing its contour and shape and transmit the load from the skin to the spars. Ribs are also used in ailerons, elevators, fins, and stabilizers. Former ribs, located at frequent intervals throughout the wing, are made of formed sheet metal and are very lightweight. The bent-up portion of a former rib is the flange and the vertical portion is the web.

A longeron or stringer or stiffener[1] is a thin strip of wood, metal or carbon fiber, to which the skin of the aircraft is fastened. In the fuselage, longerons are attached to formers (also called frames) and run the longitudinal direction of the aircraft. In the wing or horizontal stabilizer, longerons run spanwise and attach to ribs.

Sometimes the terms "longeron" and "stringer" are used interchangeably. Historically, though, there is a subtle difference between the two terms. If the longitudinal members in a fuselage are few in number (usually 4 to 8) then they are called "longerons"If the longitudinal members are numerous (usually 50 to 100) then they are called "stringers".

On large modern aircraft the stringer system is more common because it is more weight efficient despite being more complex to construct and analyze. Some aircraft, however, use a combination of both stringers and longerons.

_____Longerons often carry larger loads than stringers and also help to transfer skin loads to internal structure. As stated above longerons nearly always attach to frames or ribs. But stringers often are not attached to anything but the skin, where they carry a portion of the fuselage bending moment through axial loading.[

The wings are the most important lift-producing part of the aircraft. Wings vary in design depending upon the aircraft type and its purpose. Most airplanes are designed so that the outer tips of the wings are higher than where the wings are attached to the fuselage. This upward angle is called the dihedral and helps keep the airplane from rolling unexpectedly during flight.