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aircraft,heavier-than-air vehicle, mechanically driven and fitted with fixed wings that support it in flight through the dynamic action of the air.
Parts of an Airplane
The airplane has six main parts—fuselage, wings, stabilizer (or tail plane), rudder, one or more engines, and landing gear. The fuselage is the main body of the machine, customarily streamlined in form. It usually contains control equipment, and space for passengers and cargo. The wings are the main supporting surfaces. Modern airplanes are monoplanes (airplanes with one wing) and may be high-wing, mid-wing, or low-wing (relative to the bottom of the fuselage). At the trailing edge of the wings are auxiliary hinged surfaces known as ailerons that are used to gain lateral control and to turn the airplane.
The lift of an airplane, or the force that supports it in flight, is basically the result of the direct action of the air against the surfaces of the wings, which causes air to be accelerated downward. The lift varies with the speed, there being a minimum speed at which flight can be maintained. This is known as the stall speed. Because speed is so important to maintain lift, objects such as fuel tanks and engines, that are carried outside the fuselage are enclosed in structures called nacelles, or pods, to reduce air drag (the retarding force of the air as the airplane moves through it).
Directional stability is provided by the tail fin, a fixed vertical airfoilairfoil,
surface designed to develop a desired force by reaction with a fluid, especially air, that is flowing across the surface. For example, the fixed wing surfaces of an airplane produce lift, which opposes gravity.
..... Click the link for more information. at the rear of the plane. The stabilizer, or tail plane, is a fixed horizontal airfoil at the rear of the airplane used to suppress undesired pitching motions. To the rear of the stabilizer are usually hinged the elevators, movable auxiliary surfaces that are used to produce controlled pitching. The rudder, generally at the rear of the tail fin, is a movable auxiliary airfoil that gives the craft a yawing (turning about a vertical axis) movement in normal flight. The rear array of airfoils is called the empennage, or tail assembly. Some aircraft have additional flaps near the ailerons that can be lowered during takeoff and landing to augment lift at the cost of increased drag. On some airplanes hinged controls are replaced or assisted by spoilers, which are ridges that can be made to project from airfoils.
Airplane engines may be classified as driven by propeller, jet, turbojet, or rocket. Most engines originally were of the internal-combustion, piston-operated type, which may be air- or liquid-cooled. During and after World War II, duct-type and gas-turbine engines became increasingly important, and since then jet propulsionjet propulsion,
propulsion of a body by a force developed in reaction to the ejection of a high-speed jet of gas. Jet Propulsion Engines
The four basic parts of a jet engine are the compressor, turbine, combustion chamber, and propelling nozzles.
..... Click the link for more information. has become the main form of power in most commercial and military aircraft. The landing gear is the understructure that supports the weight of the craft when on the ground or on the water and that reduces the shock on landing. There are five common types—the wheel, float, boat, skid, and ski types.
Developments in Airplane Design
Early attempts were made to build flying machines according to the principle of bird flightflight,
sustained, self-powered motion through the air, as accomplished by an animal, aircraft, or rocket. Animal Flight
Adaptation for flight is highly developed in birds and insects. The bat is the only mammal that accomplishes true flight.
..... Click the link for more information. , but these failed; it was not until the beginning of the 20th cent. that flight in heavier-than-air craft was achieved. On Dec. 17, 1903, the Wright brothersWright brothers,
American airplane inventors and aviation pioneers. Orville Wright 1871–1948, was born in Dayton, Ohio, and Wilbur Wright, 1867–1912, near New Castle, Ind.
..... Click the link for more information. produced the first manned, power-driven, heavier-than-air flying machine near Kitty Hawk, N.C. The first flight lasted 12 sec, but later flights on the same day were a little longer; a safe landing was made after each attempt. The machine was a biplane (an airplane with two main supporting surfaces, or wings) with two propellers chain-driven by a gasoline motor.
The evolution of the airplane engine has had a major effect upon aircraft design, which is closely associated with the ratio between power load (horsepower) and weight. The Wright brothers' first engine weighed about 12 lb (5.4 kg) per horsepower. The modern piston engine weighs about 1 lb (0.4 kg) or less per horsepower, and jet and gas-turbine engines are much lighter. With the use of jet engines and the resulting higher speeds, airplanes have become less dependent on large values of lift from the wings. Consequently, wings have been shortened and swept back so as to produce less drag, especially at supersonic speeds. In some cases these radically backswept wings have evolved into a single triangular lifting surface, known as a delta wing, that is bisected by the fuselage of the plane. Similar alterations have been made in the vertical and horizontal surfaces of the tail, again with the aim of decreasing drag.
For certain applications, e.g., short-haul traffic between small airports, it is desirable to have airplanes capable of operating from a runway of minimum length. Two approaches to the problem have been tried. One, the vertical takeoff and landingvertical takeoff and landing aircraft
(VTOL), craft capable of rising and descending vertically from and to the ground, thus requiring no runway. While a balloon or an airship has obvious VTOL capability, both are very inefficient at moving parallel to the earth's surface.
..... Click the link for more information. (VTOL) approach, seeks to produce craft that take off and land like helicoptershelicopter,
type of aircraft in which lift is obtained by means of one or more power-driven horizontal propellers called rotors. When the rotor of a helicopter turns it produces reaction torque which tends to make the craft spin also.
..... Click the link for more information. , but that can fly much faster. The other approach, short takeoff and landingshort takeoff and landing aircraft
(STOL), heavier-than-air craft, capable of rising from and descending to the ground with only a short length of runway, but incapable of doing so vertically. The precise definition of an STOL aircraft has not been universally agreed upon.
..... Click the link for more information. (STOL), seeks to design more conventional aircraft that have reduced runway requirements. The lessened lift associated with swept-back wing designs increases the length of runway needed for takeoffs and landings. To keep runway lengths within reasonable limits the variable-sweep, or swing, wing has been developed. A plane of this type can extend its wings for maximum lift in taking off and landing, and swing them back for travel at high speeds.
A proposed variant of the swing wing, in which one wing sweeps to the rear and another forward, produces an arrangement that causes a minimum shock wave at supersonic speeds. It is thought that if this modification were applied to supersonic transport (SST) designs it would somewhat lessen their objectionable noise levels. No solution has been proposed to lessen their high fuel consumption, however. Recent developments in fan-jet engines, in which a turbine powers a set of vanes that drive air rearward to augment thrust, have made supersonic flight possible at low altitude. Much research has also gone into reducing the noise and air pollution caused by jet engines.
study of gases in motion. As the principal application of aerodynamics is the design of aircraft, air is the gas with which the science is most concerned. Although aerodynamics is primarily concerned with flight, its principles are also used in designing automobile
..... Click the link for more information. ; airportairport
place for landing and departure of aircraft, usually with facilities for housing and maintaining planes and for receiving and discharging passengers and cargo.
..... Click the link for more information. ; aviationaviation,
operation of heavier-than-air aircraft and related activities. Aviation can be conveniently divided into military aviation, air transport, and general aviation.
..... Click the link for more information. ; autogiroautogiro
, type of aircraft supported in the air by a horizontally mounted airfoil similar to that of a helicopter but unpowered. Invented by the Spaniard Juan de la Cierva, it was first flown successfully in Jan., 1923, in Spain.
..... Click the link for more information. ; gliderglider,
type of aircraft resembling an airplane but having at most a small auxiliary propulsion plant and usually no means of propulsion at all. The typical modern glider has very slender wings and a streamlined body.
..... Click the link for more information. ; seaplaneseaplane,
airplane designed to take off from and alight on water. The two most common types are the floatplane, whose fuselage is supported by struts attached to two or more pontoon floats, and the flying boat, whose boat-hull fuselage is constructed with the buoyancy and
..... Click the link for more information. .
See bibliography under aviationaviation,
operation of heavier-than-air aircraft and related activities. Aviation can be conveniently divided into military aviation, air transport, and general aviation.
..... Click the link for more information. .
a heavier-than-air aircraft for flights in the atmosphere using engines and, usually, fixed wings. Because of its high speed, carrying capacity, effective range, operational reliability, and maneuverability, the airplane has become the most widely used type of aircraft. It is used to transport passengers and cargo and for military and special purposes. (See AVIATION for the historical development of the airplane and basic information.)
Classification. According to function, airplanes are classified as civil or military. Civil airplanes include transports (passenger, cargo-passenger, and cargo airplanes); sports airplanes; airplanes for setting speed, rate-of-climb, altitude, range, and other records; commuter, executive, training, agricultural, and special-purpose airplanes (such as rescue airplanes and remote-controlled airplanes); and experimental airplanes. Military airplanes are designed to destroy airborne and ground or naval targets or to carry out other combat missions. They are subdivided into fighter-bombers, bombers, and reconnaissance, transport, liaison, and ambulance airplanes. (SeeAIR FORCE, FIGHTER AVIATION, FIGHTER-BOMBER AVIATION. BOMBER AVIATION, RECONNAISSANCE AVIATION, and MILITARY TRANSPORT AVIATION.)
External features are the basis for the classification of airplanes according to design. Such features include the number and position of wings and engines and the shape and position of the empennage. Figure 1 illustrates the principal types of airplanes. Depending on the number of wings, a distinction is
made between monoplanes—airplanes with a single wing—and biplanes—airplanes with two wings positioned one above the other. Biplanes with one wing shorter than the other are called sesquiplanes. Biplanes are more maneuverable than monoplanes, but they have greater drag, which reduces the flying speed. Most modern airplanes therefore use the monoplane design.
Depending on the position of the wing with respect to the fuselage, airplanes are classified as low-wing, midwing, or high-wing.
Depending on the position of the empennage, a distinction is made between airplanes of the classical design, where the empennage is located behind the wing, airplanes with a “canard” configuration, where the horizontal control surfaces are located in front of the wing, and “tailless” airplanes, where the control surfaces are incorporated into the wing. The classical design may feature a single fin, multiple fins, or a V-shaped empennage.
Depending on the type of landing gear, airplanes are classified as land-based airplanes, seaplanes, or amphibians (seaplanes equipped with wheeled landing gear).
Depending on the type of engines, airplanes are classified as piston-engine, turboprop, or turbojet airplanes.
Depending on flying speed, airplanes are classified as subsonic (with a speed corresponding to a Mach number M < 1), supersonic (5 > M≥ 1), or hypersonic (M≥ 5).
Aerodynamics. Aerodynamic force R arises as a result of the action of the air flow on the wing (see AERODYNAMIC FORCE AND MOMENT). The vertical component of this force with respect to the flow is called lift Y, and the horizontal component is called drag Q (seeAERODYNAMIC DRAG). The drag is the sum of the forces of air friction against the surface of the wing Qfr and the pressure of the air flow Qpre (which are combined in a quantity called the profile drag Qpro = Qfr + Qpre) together with the induced drag Qind, which arises when lift is present on the wing. Induced drag is caused by the formation of air vortices at the ends of the wing as a result of the flow of air from the region of positive pressure below the wing to the region of negative pressure above it. At a flying speed close to the speed of sound, wave drag Qw may arise. The lift of an airplane is usually equal to the lift of the wing, and the drag is equal to the sum of the resistances of the fuselage, empennage, and other parts of the airplane over which the airstream flows, together with the interference drag gint (the mutual influence of these parts). The lift-to-drag ratio K = Y/Q is an important characteristic of airplanes; the maximum value of the ratio for modern airplanes reaches 10–20.
Engine installation. The power plant of an airplane consists of aircraft engines and various systems and devices, such as propellers, fire-fighting equipment, and the fuel, induction, starting, lubrication, and thrust control systems. In selecting the point of installation of engines and the number and type of engines, it is necessary to take into account the aerodynamic drag produced by the engines, the rotational moment that arises if one of the engines fails, the complexity of the layout of the air intakes, the possibility of servicing and replacing engines, the noise level in the passenger compartment, and other factors.
Design. The basic parts of an airplane are the wing, fuselage, landing gear, and empennage. The general layout of an I1–62 turbojet passenger airplane is illustrated in Figure 2.
The wing creates lift as the airplane moves. It is usually rigidly fixed to the fuselage but can sometimes be rotated with respect to the lateral axis of the airplane, as in vertical takeoff and landing aircraft, or its configuration (sweep and span) can change. Roll control surfaces (ailerons) and high-lift devices are mounted on the wing. The fuselage houses the crew, passengers, cargo, and equipment, and structurally connects the wing, empennage, and sometimes the landing gear and power plant. The landing gear is used for takeoff and landing and for taxiing on the airfield. Wheeled landing gear, floats (on seaplanes), skis, and caterpillar tracks (on airplanes with cross-country capabilities) may be installed on airplanes. The landing gear may be retractable in flight or fixed. An airplane with retractable landing gear has lower drag but is heavier and more complex in design. The empennage provides stability, control, and balance for the airplane.
Control systems and equipment. The control systems of an air plane are divided into the primary and auxiliary systems. The control systems for the control surfaces are commonly listed as primary systems. The auxiliary systems are used to control the
engines, trim tabs, landing gear, brakes, hatches, and doors. The airplane is controlled by means of a control column or stick, pedals, switches, and other devices located in the crew cabin. Automatic pilots and on-board computers may be included in the control system to facilitate piloting and increase flight safety; dual-type controls are used. The loads acting on the controls when control surfaces are operated are reduced by hydraulic, pneumatic, or electrical amplifiers called boosters and by servomechanisms. If the control surfaces prove ineffective, for example, during flight in very thin atmosphere or on vertical takeoff and landing aircraft, control is accomplished by means of gas vanes.
The equipment of an airplane includes instrumentation, radio and electrical equipment, deicers, high-altitude and special-purpose equipment, and cabin furnishings. Additional equipment for military airplanes includes armament, such as cannon, rockets, and aerial bombs, and armor. Depending on the function, instrumentation is classified as flight-control and navigational equipment, including variometers, artificial horizons, compasses, and automatic pilots, equipment for monitoring engine operation, such as pressure and fuel consumption gauges, and auxiliary equipment, such as ammeters and voltmeters. The electrical equipment provides for the operation of instruments, control equipment, radios, the engine starting system, and lighting. The radio equipment includes radio communication, radio navigation, and radar equipment and automatic takeoff and landing systems. The high-altitude equipment, including air-conditioning and oxygen supply systems, is used to protect and ensure the safety of passengers and crew during flight at high altitudes. Cabin furnishings provide convenience and comfort for the passengers and crew. The special equipment includes systems that provide automatic monitoring of the operation of equipment and aircraft structures, aerial photography systems, and equipment for transporting the sick and wounded.
Vertical takeoff and landing (VTOL) and short takeoff and landing (STOL) aircraft. An increase in the flying speeds of airplanes results in an increase in takeoff and landing speeds. Consequently, the lengths of runways can reach several kilometers. STOL and VTOL aircraft are being developed in connection with this trend. STOL aircraft feature high cruising speeds (600–800 km/hr) and a takeoff and landing distance no greater than 600–650 m. The reduction in takeoff and landing distance is achieved primarily by using powerful high-lift devices, by controlling the boundary layer, by using acceleration assists during takeoff and speed-reducing devices during landing, and by deflecting the thrust vector of the main engines. In VTOL aircraft, vertical takeoffs and landings are accomplished by using special lift engines, by deflecting the jet nozzles, or by rotating the main engines, which are generally turbojets. Typical configurations for VTOL aircraft are illustrated in Figure 3.
REFERENCESPalenyi, E. G. Oborudovanie samoletov. Moscow, 1968.
Kurochkin, F. P. Osnovy proektirovaniia samoletov s vertikal’nym vzletom i posadkoi. Moscow, 1970.
Shul’zhenko, M. N. Konstruktsiia samoletov, 3rd ed. Moscow, 1971.
Nikitin, G. A., and E. A. Bakanov. Osnovy aviatsii. Moscow, 1972.
Proektirovanie samoletov, 2nd ed. Moscow, 1972.
Sheinin, V. M., and V. I. Kozlovskii. Problemy proektirovaniia passazhirskikh samoletov. Moscow, 1972.
Schmidt, H. A. F. Lexikon Luftfahrt. Berlin, 1971.
Jane’s All the World’s Aircraft. London, 1909—.
G. A. NIKITIN and E. A. BAKANOV
What does it mean when you dream about an airplane?
Airplanes in dreams may carry the same connotations as air (e.g., ideas, intellect) or simply represent flying dreams. Particularly if one is the pilot, an airplane may represent one’s body, freedom, the power to “rise above” a situation, soaring to new heights, or even escape from everyday concerns.
A heavier-than-air vehicle designed to use the pressures created by its motion through the air to lift and transport useful loads. To achieve practical, controllable flight, an airplane must consist of a source of thrust for propulsion, a geometric arrangement to produce lift, and a control system capable of maneuvering the vehicle within prescribed limits. Further, to be satisfactory, the vehicle should display stable characteristics, so that if it is disturbed from an equilibrium condition, forces and moments are created which return it to its original condition without necessitating corrective action on the part of the pilot. Efficient design will minimize the aerodynamic drag, thereby reducing the propulsive thrust required for a given flight condition, and will maximize the lifting capability per pound of airframe and engine weight, thereby increasing the useful, or transportable, load. See Airframe, Flight controls