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80-459: Due to the inherent dangers in the use of flight vehicles, national aviation authorities typically regulate the following critical aspects of aircraft airworthiness and their operation: Depending on the legal system of the jurisdiction, a CAA will derive its powers from an act of parliament (such as the Civil or Federal Aviation Act), and is then empowered to make regulations within the bounds of

160-404: A combustion chamber , and accelerate the exhaust rearwards to provide thrust. Different jet engine configurations include the turbojet and turbofan , sometimes with the addition of an afterburner . Those with no rotating turbomachinery include the pulsejet and ramjet . These mechanically simple engines produce no thrust when stationary, so the aircraft must be launched to flying speed using

240-433: A lifting gas such as helium , hydrogen or hot air , which is less dense than the surrounding air. When the weight of the lifting gas is added to the weight of the aircraft itself, it is same or less than the mass of the air that the craft displaces. Small hot-air balloons, called sky lanterns , were first invented in ancient China prior to the 3rd century BC and used primarily in cultural celebrations, and were only

320-560: A catapult, like the V-1 flying bomb , or a rocket, for example. Other engine types include the motorjet and the dual-cycle Pratt & Whitney J58 . Compared to engines using propellers, jet engines can provide much higher thrust, higher speeds and, above about 40,000 ft (12,000 m), greater efficiency. They are also much more fuel-efficient than rockets . As a consequence nearly all large, high-speed or high-altitude aircraft use jet engines. Some rotorcraft, such as helicopters , have

400-764: A completely separate personnel licensing system. In the United Kingdom, military aviation is regulated by the Military Aviation Authority . The International Civil Aviation Organization (ICAO) refers to civil aviation authorities as National Airworthiness Authorities (NAA), particularly when referring to an authority in its capacity as an airworthiness authority; or sometimes as National Aviation Authorities (also NAA). EASA refers to them as National Aviation Authorities. The independent development of CAAs resulted in differing regulations from country to country. This required aircraft manufacturers in

480-599: A force on the airfoil in the direction opposite to the deflection. This force is known as aerodynamic force and can be resolved into two components: lift ( perpendicular to the remote freestream velocity ) and drag ( parallel to the freestream velocity). The lift on an airfoil is primarily the result of its angle of attack . Most foil shapes require a positive angle of attack to generate lift, but cambered airfoils can generate lift at zero angle of attack. Airfoils can be designed for use at different speeds by modifying their geometry: those for subsonic flight generally have

560-638: A general purpose airfoil that finds wide application, and pre–dates the NACA system, is the Clark-Y . Today, airfoils can be designed for specific functions by the use of computer programs. The various terms related to airfoils are defined below: The geometry of the airfoil is described with a variety of terms : The shape of the airfoil is defined using the following geometrical parameters: Some important parameters to describe an airfoil's shape are its camber and its thickness . For example, an airfoil of

640-638: A greater wingspan (94m/260 ft) than any current aircraft and a tail height equal to the tallest (Airbus A380-800 at 24.1m/78 ft) — flew only one short hop in the late 1940s and never flew out of ground effect . The largest civilian airplanes, apart from the above-noted An-225 and An-124, are the Airbus Beluga cargo transport derivative of the Airbus A300 jet airliner, the Boeing Dreamlifter cargo transport derivative of

720-620: A higher average velocity on the upper surface than on the lower surface. In some situations (e.g., inviscid potential flow ) the lift force can be related directly to the average top/bottom velocity difference without computing the pressure by using the concept of circulation and the Kutta–Joukowski theorem . The wings and stabilizers of fixed-wing aircraft , as well as helicopter rotor blades, are built with airfoil-shaped cross sections. Airfoils are also found in propellers, fans , compressors and turbines . Sails are also airfoils, and

800-674: A marginal case. The forerunner of the fixed-wing aircraft is the kite . Whereas a fixed-wing aircraft relies on its forward speed to create airflow over the wings, a kite is tethered to the ground and relies on the wind blowing over its wings to provide lift. Kites were the first kind of aircraft to fly and were invented in China around 500 BC. Much aerodynamic research was done with kites before test aircraft, wind tunnels , and computer modelling programs became available. The first heavier-than-air craft capable of controlled free-flight were gliders . A glider designed by George Cayley carried out

880-794: A maximum loaded weight of 550–700 t (1,210,000–1,540,000 lb), it was also the heaviest aircraft built to date. It could cruise at 500 mph (800 km/h; 430 kn). The aircraft was destroyed during the Russo-Ukrainian War . The largest military airplanes are the Ukrainian Antonov An-124 Ruslan (world's second-largest airplane, also used as a civilian transport), and American Lockheed C-5 Galaxy transport, weighing, loaded, over 380 t (840,000 lb). The 8-engine, piston/propeller Hughes H-4 Hercules "Spruce Goose" — an American World War II wooden flying boat transport with

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960-569: A payload of up to 22,050 lb (10,000 kg). The largest aircraft by weight and largest regular fixed-wing aircraft ever built, as of 2016 , was the Antonov An-225 Mriya . That Soviet-built ( Ukrainian SSR ) six-engine transport of the 1980s was 84 m (276 ft) long, with an 88 m (289 ft) wingspan. It holds the world payload record, after transporting 428,834 lb (194,516 kg) of goods, and has flown 100 t (220,000 lb) loads commercially. With

1040-588: A powered "tug" aircraft. For a glider to maintain its forward air speed and lift, it must descend in relation to the air (but not necessarily in relation to the ground). Many gliders can "soar", i.e. , gain height from updrafts such as thermal currents. The first practical, controllable example was designed and built by the British scientist and pioneer George Cayley , whom many recognise as the first aeronautical engineer. Common examples of gliders are sailplanes , hang gliders and paragliders . Balloons drift with

1120-491: A powered rotary wing or rotor , where the rotor disc can be angled slightly forward so that a proportion of its lift is directed forwards. The rotor may, like a propeller, be powered by a variety of methods such as a piston engine or turbine. Experiments have also used jet nozzles at the rotor blade tips . Aircraft are designed according to many factors such as customer and manufacturer demand, safety protocols and physical and economic constraints. For many types of aircraft

1200-577: A rigid basket or gondola slung below it to carry its payload. Early aircraft, including airships , often employed flexible doped aircraft fabric covering to give a reasonably smooth aeroshell stretched over a rigid frame. Later aircraft employed semi- monocoque techniques, where the skin of the aircraft is stiff enough to share much of the flight loads. In a true monocoque design there is no internal structure left. The key structural parts of an aircraft depend on what type it is. Lighter-than-air types are characterised by one or more gasbags, typically with

1280-402: A rounded leading edge , while those designed for supersonic flight tend to be slimmer with a sharp leading edge. All have a sharp trailing edge . The air deflected by an airfoil causes it to generate a lower-pressure "shadow" above and behind itself. This pressure difference is accompanied by a velocity difference, via Bernoulli's principle , so the resulting flowfield about the airfoil has

1360-421: A subsonic flow about a thin airfoil can be described in terms of an outer region, around most of the airfoil chord, and an inner region, around the nose, that asymptotically match each other. As the flow in the outer region is dominated by classical thin airfoil theory, Morris's equations exhibit many components of thin airfoil theory. In thin airfoil theory, the width of the (2D) airfoil is assumed negligible, and

1440-420: A supporting structure of flexible cables or a rigid framework called its hull. Other elements such as engines or a gondola may also be attached to the supporting structure. Heavier-than-air types are characterised by one or more wings and a central fuselage . The fuselage typically also carries a tail or empennage for stability and control, and an undercarriage for takeoff and landing. Engines may be located on

1520-522: Is a lifting body , which has no wings, though it may have small stabilizing and control surfaces. Wing-in-ground-effect vehicles are generally not considered aircraft. They "fly" efficiently close to the surface of the ground or water, like conventional aircraft during takeoff. An example is the Russian ekranoplan nicknamed the " Caspian Sea Monster ". Man-powered aircraft also rely on ground effect to remain airborne with minimal pilot power, but this

1600-437: Is a powered one. A powered, steerable aerostat is called a dirigible . Sometimes this term is applied only to non-rigid balloons, and sometimes dirigible balloon is regarded as the definition of an airship (which may then be rigid or non-rigid). Non-rigid dirigibles are characterized by a moderately aerodynamic gasbag with stabilizing fins at the back. These soon became known as blimps . During World War II , this shape

1680-406: Is a streamlined body that is capable of generating significantly more lift than drag . Wings, sails and propeller blades are examples of airfoils. Foils of similar function designed with water as the working fluid are called hydrofoils . When oriented at a suitable angle, a solid body moving through a fluid deflects the oncoming fluid (for fixed-wing aircraft, a downward force), resulting in

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1760-478: Is called aviation . The science of aviation, including designing and building aircraft, is called aeronautics . Crewed aircraft are flown by an onboard pilot , whereas unmanned aerial vehicles may be remotely controlled or self-controlled by onboard computers . Aircraft may be classified by different criteria, such as lift type, aircraft propulsion (if any), usage and others. Flying model craft and stories of manned flight go back many centuries; however,

1840-401: Is increased before the wing achieves maximum thickness to minimize the chance of boundary layer separation. This elongates the wing and moves the point of maximum thickness back from the leading edge. Supersonic airfoils are much more angular in shape and can have a very sharp leading edge, which is very sensitive to angle of attack. A supercritical airfoil has its maximum thickness close to

1920-1115: Is normally called the powerplant , and includes engine or motor , propeller or rotor , (if any), jet nozzles and thrust reversers (if any), and accessories essential to the functioning of the engine or motor (e.g.: starter , ignition system , intake system , exhaust system , fuel system , lubrication system, engine cooling system , and engine controls ). Powered aircraft are typically powered by internal combustion engines ( piston or turbine ) burning fossil fuels —typically gasoline ( avgas ) or jet fuel . A very few are powered by rocket power , ramjet propulsion, or by electric motors , or by internal combustion engines of other types, or using other fuels. A very few have been powered, for short flights, by human muscle energy (e.g.: Gossamer Condor ). The avionics comprise any electronic aircraft flight control systems and related equipment, including electronic cockpit instrumentation, navigation, radar , monitoring, and communications systems . Airfoil An airfoil ( American English ) or aerofoil ( British English )

2000-509: Is not English) Aircraft An aircraft ( pl. : aircraft) is a vehicle that is able to fly by gaining support from the air . It counters the force of gravity by using either static lift or the dynamic lift of an airfoil , or, in a few cases, direct downward thrust from its engines. Common examples of aircraft include airplanes , helicopters , airships (including blimps ), gliders , paramotors , and hot air balloons . The human activity that surrounds aircraft

2080-452: Is only because they are so underpowered—in fact, the airframe is capable of flying higher. Rotorcraft, or rotary-wing aircraft, use a spinning rotor with aerofoil cross-section blades (a rotary wing ) to provide lift. Types include helicopters , autogyros , and various hybrids such as gyrodynes and compound rotorcraft. Helicopters have a rotor turned by an engine-driven shaft. The rotor pushes air downward to create lift. By tilting

2160-623: Is stored in tanks, usually in the wings but larger aircraft also have additional fuel tanks in the fuselage . Propeller aircraft use one or more propellers (airscrews) to create thrust in a forward direction. The propeller is usually mounted in front of the power source in tractor configuration but can be mounted behind in pusher configuration . Variations of propeller layout include contra-rotating propellers and ducted fans . Many kinds of power plant have been used to drive propellers. Early airships used man power or steam engines . The more practical internal combustion piston engine

2240-475: Is the Lockheed SR-71 Blackbird , a U.S. reconnaissance jet fixed-wing aircraft, having reached 3,530 km/h (2,193 mph) on 28 July 1976. Gliders are heavier-than-air aircraft that do not employ propulsion once airborne. Take-off may be by launching forward and downward from a high location, or by pulling into the air on a tow-line, either by a ground-based winch or vehicle, or by

2320-401: Is the position at which the pitching moment M ′ does not vary with a change in lift coefficient: ∂ ( C M ′ ) ∂ ( C L ) = 0 . {\displaystyle {\frac {\partial (C_{M'})}{\partial (C_{L})}}=0{\text{.}}} Thin-airfoil theory shows that, in two-dimensional inviscid flow,

2400-629: The Bell Boeing V-22 Osprey ), tiltwing , tail-sitter , and coleopter aircraft have their rotors/ propellers horizontal for vertical flight and vertical for forward flight. The smallest aircraft are toys/recreational items, and nano aircraft . The largest aircraft by dimensions and volume (as of 2016) is the 302 ft (92 m) long British Airlander 10 , a hybrid blimp, with helicopter and fixed-wing features, and reportedly capable of speeds up to 90 mph (140 km/h; 78 kn), and an airborne endurance of two weeks with

2480-495: The Biot–Savart law , the vorticity γ( x ) produces a flow field w ( x ) = 1 2 π ∫ 0 c γ ( x ′ ) x − x ′ d x ′ , {\displaystyle w(x)={\frac {1}{2\pi }}\int _{0}^{c}{\frac {\gamma (x')}{x-x'}}\,dx'{\text{,}}} oriented normal to

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2560-693: The Boeing 747 jet airliner/transport (the 747-200B was, at its creation in the 1960s, the heaviest aircraft ever built, with a maximum weight of over 400 t (880,000 lb)), and the double-decker Airbus A380 "super-jumbo" jet airliner (the world's largest passenger airliner). The fastest fixed-wing aircraft and fastest glider, is the Space Shuttle , which re-entered the atmosphere at nearly Mach 25 or 17,500 mph (28,200 km/h) The fastest recorded powered aircraft flight and fastest recorded aircraft flight of an air-breathing powered aircraft

2640-637: The Harrier jump jet and Lockheed Martin F-35B take off and land vertically using powered lift and transfer to aerodynamic lift in steady flight. A pure rocket is not usually regarded as an aerodyne because its flight does not depend on interaction with the air at all (and thus can even fly in the vacuum of outer space ); however, many aerodynamic lift vehicles have been powered or assisted by rocket motors. Rocket-powered missiles that obtain aerodynamic lift at very high speed due to airflow over their bodies are

2720-1287: The change of variables x = c ⋅ 1 + cos ⁡ ( θ ) 2 , {\displaystyle x=c\cdot {\frac {1+\cos(\theta )}{2}},} and then expanding both dy ⁄ dx and γ( x ) as a nondimensionalized Fourier series in θ with a modified lead term: d y d x = A 0 + A 1 cos ⁡ ( θ ) + A 2 cos ⁡ ( 2 θ ) + … γ ( x ) = 2 ( α + A 0 ) ( sin ⁡ θ 1 + cos ⁡ θ ) + 2 A 1 sin ⁡ ( θ ) + 2 A 2 sin ⁡ ( 2 θ ) + … . {\displaystyle {\begin{aligned}&{\frac {dy}{dx}}=A_{0}+A_{1}\cos(\theta )+A_{2}\cos(2\theta )+\dots \\&\gamma (x)=2(\alpha +A_{0})\left({\frac {\sin \theta }{1+\cos \theta }}\right)+2A_{1}\sin(\theta )+2A_{2}\sin(2\theta )+\dots {\text{.}}\end{aligned}}} The resulting lift and moment depend on only

2800-648: The convolution equation ( α − d y d x ) V = − w ( x ) = − 1 2 π ∫ 0 c γ ( x ′ ) x − x ′ d x ′ , {\displaystyle \left(\alpha -{\frac {dy}{dx}}\right)V=-w(x)=-{\frac {1}{2\pi }}\int _{0}^{c}{\frac {\gamma (x')}{x-x'}}\,dx'{\text{,}}} which uniquely determines it in terms of known quantities. An explicit solution can be obtained through first

2880-411: The trailing edge angle . The slope is greatest if the angle is zero; and decreases as the angle increases. For a wing of finite span, the aspect ratio of the wing also significantly influences the slope of the curve. As aspect ratio decreases, the slope also decreases. Thin airfoil theory is a simple theory of airfoils that relates angle of attack to lift for incompressible, inviscid flows . It

2960-663: The 1/4 chord point will thus be C M ( 1 / 4 c ) = − π / 4 ( A 1 − A 2 ) . {\displaystyle C_{M}(1/4c)=-\pi /4(A_{1}-A_{2}){\text{.}}} From this it follows that the center of pressure is aft of the 'quarter-chord' point 0.25 c , by Δ x / c = π / 4 ( ( A 1 − A 2 ) / C L ) . {\displaystyle \Delta x/c=\pi /4((A_{1}-A_{2})/C_{L}){\text{.}}} The aerodynamic center

3040-435: The 1930s, large intercontinental flying boats were also sometimes referred to as "ships of the air" or "flying-ships".  — though none had yet been built. The advent of powered balloons, called dirigible balloons, and later of rigid hulls allowing a great increase in size, began to change the way these words were used. Huge powered aerostats, characterized by a rigid outer framework and separate aerodynamic skin surrounding

3120-467: The 1980s revealed the practicality and usefulness of laminar flow wing designs and opened the way for laminar-flow applications on modern practical aircraft surfaces, from subsonic general aviation aircraft to transonic large transport aircraft, to supersonic designs. Schemes have been devised to define airfoils – an example is the NACA system . Various airfoil generation systems are also used. An example of

3200-657: The European Union and the European Free Trade Association. Member states continue to have their own agencies, which implement EASA rules. EASA has working relationships with non-member states including Armenia, Georgia, Moldova and Ukraine. It was renamed the European Union Aviation Safety Agency in 2018. This is a list of national and supra-national civil aviation authorities. (If the local language

3280-409: The NACA 4-digit series such as the NACA 2415 (to be read as 2 – 4 – 15) describes an airfoil with a camber of 0.02 chord located at 0.40 chord, with 0.15 chord of maximum thickness. Finally, important concepts used to describe the airfoil's behaviour when moving through a fluid are: In two-dimensional flow around a uniform wing of infinite span, the slope of the lift curve is determined primarily by

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3360-770: The act. This allows technical aspects of airworthiness to be dealt with by subject matter experts and not politicians. A CAA may also be involved in the investigation of aircraft accidents, although in many cases this is left to a separate body (such as the Australian Transport Safety Bureau (ATSB) in Australia or the National Transportation Safety Board (NTSB) in the United States), to allow independent review of regulatory oversight. A CAA will regulate

3440-470: The aircraft's weight. There are two ways to produce dynamic upthrust — aerodynamic lift by having air flowing past an aerofoil (such dynamic interaction of aerofoils with air is the origin of the term "aerodyne"), or powered lift in the form of reactional lift from downward engine thrust . Aerodynamic lift involving wings is the most common, and can be achieved via two methods. Fixed-wing aircraft ( airplanes and gliders ) achieve airflow past

3520-428: The airfoil at x . Since the airfoil is an impermeable surface , the flow w ( x ) {\displaystyle w(x)} must balance an inverse flow from V . By the small-angle approximation , V is inclined at angle α- dy ⁄ dx relative to the blade at position x , and the normal component is correspondingly (α- dy ⁄ dx ) V . Thus, γ( x ) must satisfy

3600-409: The airfoil generates a circulation around the blade, which can be modeled as a vortex sheet of position-varying strength γ( x ) . The Kutta condition implies that γ( c )=0 , but the strength is singular at the bladefront, with γ( x )∝ 1 ⁄ √ x for x ≈ 0 . If the main flow V has density ρ , then the Kutta–Joukowski theorem gives that

3680-399: The airfoil itself replaced with a 1D blade along its camber line, oriented at the angle of attack α . Let the position along the blade be x , ranging from 0 at the wing's front to c at the trailing edge; the camber of the airfoil, dy ⁄ dx , is assumed sufficiently small that one need not distinguish between x and position relative to the fuselage. The flow across

3760-501: The autogyro moves forward, air blows upward across the rotor, making it spin. This spinning increases the speed of airflow over the rotor, to provide lift. Rotor kites are unpowered autogyros, which are towed to give them forward speed or tethered to a static anchor in high-wind for kited flight. Compound rotorcraft have wings that provide some or all of the lift in forward flight. They are nowadays classified as powered lift types and not as rotorcraft. Tiltrotor aircraft (such as

3840-407: The chord line.) Also as a consequence of (3), the section lift coefficient of a cambered airfoil of infinite wingspan is: Thin airfoil theory assumes the air is an inviscid fluid so does not account for the stall of the airfoil, which usually occurs at an angle of attack between 10° and 15° for typical airfoils. In the mid-late 2000s, however, a theory predicting the onset of leading-edge stall

3920-703: The control of air traffic but a separate agency will generally carry out air traffic control functions. In some countries a CAA may build and operate airports , including non- airside operations such as passenger terminals; the Civil Aviation Authority of Nepal and the Civil Aviation Authority of the Philippines being among such authorities. In other countries, private companies or local government authorities may own and operate individual airports. Civil aviation authorities do not regulate military aviation. Military aviation will typically have

4000-403: The design of aircraft, propellers, rotor blades, wind turbines and other applications of aeronautical engineering. A lift and drag curve obtained in wind tunnel testing is shown on the right. The curve represents an airfoil with a positive camber so some lift is produced at zero angle of attack. With increased angle of attack, lift increases in a roughly linear relation, called the slope of

4080-435: The design process is regulated by national airworthiness authorities. The key parts of an aircraft are generally divided into three categories: The approach to structural design varies widely between different types of aircraft. Some, such as paragliders, comprise only flexible materials that act in tension and rely on aerodynamic pressure to hold their shape. A balloon similarly relies on internal gas pressure, but may have

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4160-598: The first few terms of this series. The lift coefficient satisfies C L = 2 π ( α + A 0 + A 1 2 ) = 2 π α + 2 ∫ 0 π d y d x ⋅ ( 1 + cos ⁡ θ ) d θ {\displaystyle C_{L}=2\pi \left(\alpha +A_{0}+{\frac {A_{1}}{2}}\right)=2\pi \alpha +2\int _{0}^{\pi }{{\frac {dy}{dx}}\cdot (1+\cos \theta )\,d\theta }} and

4240-477: The first manned ascent — and safe descent — in modern times took place by larger hot-air balloons developed in the 18th century. Each of the two World Wars led to great technical advances. Consequently, the history of aircraft can be divided into five eras: Lighter-than-air aircraft or aerostats use buoyancy to float in the air in much the same way that ships float on the water. They are characterized by one or more large cells or canopies, filled with

4320-532: The first true manned, controlled flight in 1853. The first powered and controllable fixed-wing aircraft (the airplane or aeroplane) was invented by Wilbur and Orville Wright . Besides the method of propulsion (if any), fixed-wing aircraft are in general characterized by their wing configuration . The most important wing characteristics are: A variable geometry aircraft can change its wing configuration during flight. A flying wing has no fuselage, though it may have small blisters or pods. The opposite of this

4400-405: The following important properties of airfoils in two-dimensional inviscid flow: As a consequence of (3), the section lift coefficient of a thin symmetric airfoil of infinite wingspan is: (The above expression is also applicable to a cambered airfoil where α {\displaystyle \alpha \!} is the angle of attack measured relative to the zero-lift line instead of

4480-418: The fuselage or wings. On a fixed-wing aircraft the wings are rigidly attached to the fuselage, while on a rotorcraft the wings are attached to a rotating vertical shaft. Smaller designs sometimes use flexible materials for part or all of the structure, held in place either by a rigid frame or by air pressure. The fixed parts of the structure comprise the airframe . The source of motive power for an aircraft

4560-514: The gas bags, were produced, the Zeppelins being the largest and most famous. There were still no fixed-wing aircraft or non-rigid balloons large enough to be called airships, so "airship" came to be synonymous with these aircraft. Then several accidents, such as the Hindenburg disaster in 1937, led to the demise of these airships. Nowadays a "balloon" is an unpowered aerostat and an "airship"

4640-795: The laminar flow, making it turbulent. For example, with rain on the wing, the flow will be turbulent. Under certain conditions, insect debris on the wing will cause the loss of small regions of laminar flow as well. Before NASA's research in the 1970s and 1980s the aircraft design community understood from application attempts in the WW II era that laminar flow wing designs were not practical using common manufacturing tolerances and surface imperfections. That belief changed after new manufacturing methods were developed with composite materials (e.g. laminar-flow airfoils developed by Professor Franz Wortmann for use with wings made of fibre-reinforced plastic ). Machined metal methods were also introduced. NASA's research in

4720-594: The leading edge to have a lot of length to slowly shock the supersonic flow back to subsonic speeds. Generally such transonic airfoils and also the supersonic airfoils have a low camber to reduce drag divergence . Modern aircraft wings may have different airfoil sections along the wing span, each one optimized for the conditions in each section of the wing. Movable high-lift devices, flaps and sometimes slats , are fitted to airfoils on almost every aircraft. A trailing edge flap acts similarly to an aileron; however, it, as opposed to an aileron, can be retracted partially into

4800-433: The lift curve. At about 18 degrees this airfoil stalls , and lift falls off quickly beyond that. The drop in lift can be explained by the action of the upper-surface boundary layer , which separates and greatly thickens over the upper surface at and past the stall angle. The thickened boundary layer's displacement thickness changes the airfoil's effective shape, in particular it reduces its effective camber , which modifies

4880-747: The moment coefficient C M = − π 2 ( α + A 0 + A 1 − A 2 2 ) = − π 2 α − ∫ 0 π d y d x ⋅ cos ⁡ ( θ ) ( 1 + cos ⁡ θ ) d θ . {\displaystyle C_{M}=-{\frac {\pi }{2}}\left(\alpha +A_{0}+A_{1}-{\frac {A_{2}}{2}}\right)=-{\frac {\pi }{2}}\alpha -\int _{0}^{\pi }{{\frac {dy}{dx}}\cdot \cos(\theta )(1+\cos \theta )\,d\theta }{\text{.}}} The moment about

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4960-486: The overall flow field so as to reduce the circulation and the lift. The thicker boundary layer also causes a large increase in pressure drag , so that the overall drag increases sharply near and past the stall point. Airfoil design is a major facet of aerodynamics . Various airfoils serve different flight regimes. Asymmetric airfoils can generate lift at zero angle of attack, while a symmetric airfoil may better suit frequent inverted flight as in an aerobatic airplane. In

5040-799: The past to develop different models for specific national requirements (such as the BAe Jetstream 31 ), and impeded airline travel into foreign jurisdictions. The Convention on International Civil Aviation (Chicago Convention) was signed in 1944 and addressed these issues. This then led to the establishment by the United Nations of the International Civil Aviation Organization (ICAO) in 1947 which now oversees member states, and works to implement regulatory changes to ensure that best practice regulations are adopted. The Joint Aviation Authorities (JAA)

5120-404: The region of the ailerons and near a wingtip a symmetric airfoil can be used to increase the range of angles of attack to avoid spin – stall . Thus a large range of angles can be used without boundary layer separation . Subsonic airfoils have a round leading edge, which is naturally insensitive to the angle of attack. The cross section is not strictly circular, however: the radius of curvature

5200-411: The rotor forward, the downward flow is tilted backward, producing thrust for forward flight. Some helicopters have more than one rotor and a few have rotors turned by gas jets at the tips. Some have a tail rotor to counteract the rotation of the main rotor, and to aid directional control. Autogyros have unpowered rotors, with a separate power plant to provide thrust. The rotor is tilted backward. As

5280-436: The second type of aircraft to fly, the first being kites , which were also first invented in ancient China over two thousand years ago (see Han Dynasty ). A balloon was originally any aerostat, while the term airship was used for large, powered aircraft designs — usually fixed-wing. In 1919, Frederick Handley Page was reported as referring to "ships of the air," with smaller passenger types as "Air yachts." In

5360-530: The tether or kite line ; they rely on virtual or real wind blowing over and under them to generate lift and drag. Kytoons are balloon-kite hybrids that are shaped and tethered to obtain kiting deflections, and can be lighter-than-air, neutrally buoyant, or heavier-than-air. Powered aircraft have one or more onboard sources of mechanical power, typically aircraft engines although rubber and manpower have also been used. Most aircraft engines are either lightweight reciprocating engines or gas turbines . Engine fuel

5440-458: The total lift force F is proportional to ρ V ∫ 0 c γ ( x ) d x {\displaystyle \rho V\int _{0}^{c}\gamma (x)\,dx} and its moment M about the leading edge proportional to ρ V ∫ 0 c x γ ( x ) d x . {\displaystyle \rho V\int _{0}^{c}x\;\gamma (x)\,dx.} From

5520-471: The underwater surfaces of sailboats, such as the centerboard , rudder , and keel , are similar in cross-section and operate on the same principles as airfoils. Swimming and flying creatures and even many plants and sessile organisms employ airfoils/hydrofoils, common examples being bird wings, the bodies of fish, and the shape of sand dollars . An airfoil-shaped wing can create downforce on an automobile or other motor vehicle, improving traction . When

5600-441: The wind is obstructed by an object such as a flat plate, a building, or the deck of a bridge, the object will experience drag and also an aerodynamic force perpendicular to the wind. This does not mean the object qualifies as an airfoil. Airfoils are highly-efficient lifting shapes, able to generate more lift than similarly sized flat plates of the same area, and able to generate lift with significantly less drag. Airfoils are used in

5680-460: The wind, though normally the pilot can control the altitude, either by heating the air or by releasing ballast, giving some directional control (since the wind direction changes with altitude). A wing-shaped hybrid balloon can glide directionally when rising or falling; but a spherically shaped balloon does not have such directional control. Kites are aircraft that are tethered to the ground or other object (fixed or mobile) that maintains tension in

5760-505: The wing if not used. A laminar flow wing has a maximum thickness in the middle camber line. Analyzing the Navier–Stokes equations in the linear regime shows that a negative pressure gradient along the flow has the same effect as reducing the speed. So with the maximum camber in the middle, maintaining a laminar flow over a larger percentage of the wing at a higher cruising speed is possible. However, some surface contamination will disrupt

5840-431: The wing. A flexible wing is a wing made of fabric or thin sheet material, often stretched over a rigid frame, similar to the flight membranes on many flying and gliding animals . A kite is tethered to the ground and relies on the speed of the wind over its wings, which may be flexible or rigid, fixed, or rotary. With powered lift, the aircraft directs its engine thrust vertically downward. V/STOL aircraft, such as

5920-402: The wings by having the entire aircraft moving forward through the air, while rotorcraft ( helicopters and autogyros ) do so by having mobile, elongated wings spinning rapidly around a mast in an assembly known as the rotor . As aerofoils, there must be air flowing over the wing to create pressure difference between above and below, thus generating upward lift over the entire wetted area of

6000-427: Was devised by German mathematician Max Munk and further refined by British aerodynamicist Hermann Glauert and others in the 1920s. The theory idealizes the flow around an airfoil as two-dimensional flow around a thin airfoil. It can be imagined as addressing an airfoil of zero thickness and infinite wingspan . Thin airfoil theory was particularly notable in its day because it provided a sound theoretical basis for

6080-672: Was founded in 1970, for cooperation between European CAAs. It published the Joint Aviation Requirements (JAR), to create minimum standards across agencies. It was replaced by the European Aviation Safety Agency and disbanded in 2009. The European Aviation Safety Agency (EASA) was created in 2003 as an agency of the European Union, replacing the Joint Aviation Authorities. It standardises aviation regulations across

6160-675: Was of the NASA X-43 A Pegasus , a scramjet -powered, hypersonic , lifting body experimental research aircraft, at Mach 9.68 or 6,755 mph (10,870 km/h) on 16 November 2004. Prior to the X-43A, the fastest recorded powered airplane flight, and still the record for the fastest manned powered airplane, was the North American X-15 , rocket-powered airplane at Mach 6.7 or 7,274 km/h (4,520 mph) on 3 October 1967. The fastest manned, air-breathing powered airplane

6240-418: Was proposed by Wallace J. Morris II in his doctoral thesis. Morris's subsequent refinements contain the details on the current state of theoretical knowledge on the leading-edge stall phenomenon. Morris's theory predicts the critical angle of attack for leading-edge stall onset as the condition at which a global separation zone is predicted in the solution for the inner flow. Morris's theory demonstrates that

6320-490: Was used for virtually all fixed-wing aircraft until World War II and is still used in many smaller aircraft. Some types use turbine engines to drive a propeller in the form of a turboprop or propfan . Human-powered flight has been achieved, but has not become a practical means of transport. Unmanned aircraft and models have also used power sources such as electric motors and rubber bands. Jet aircraft use airbreathing jet engines , which take in air, burn fuel with it in

6400-439: Was widely adopted for tethered balloons ; in windy weather, this both reduces the strain on the tether and stabilizes the balloon. The nickname blimp was adopted along with the shape. In modern times, any small dirigible or airship is called a blimp, though a blimp may be unpowered as well as powered. Heavier-than-air aircraft or aerodynes are denser than air and thus must find some way to obtain enough lift that can overcome

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