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aeroplane  In flight, the forces on an aeroplane are lift, weight, drag, and thrust. The lift is generated by the air flow over the wings, which have the shape of an aerofoil. The engine provides the thrust. The drag results from the resistance of the air to the aeroplane's passage through it. Various moveable flaps on the wings and tail allow the aeroplane to be controlled. The rudder is moved to turn the aeroplane. The elevators allow the craft to climb or dive. The ailerons are used to bank the aeroplane while turning. The flaps, slats, and spoilers are used to reduce lift and speed during landing.  After the end of World War II the wreckage of Allied and Japanese aircraft was found scattered all over Papua New Guinea; some are still to be located.  The inside of the cockpit of a Boeing 737 passenger airliner.  The Bell X-1 plane, famed as US test pilot Chuck Yeager's ‘Glamorous Glennis’, was the first plane to break the sound barrier. It is seen here accelerating towards Mach 1 on its epic flight on 14 October 1947. The aircraft's conical nose, modelled on the lines of a .50 calibre bullet, and the shock diamonds from its exhaust trail, can be seen.  It takes hundreds of people thousands of hours to design and build an aircraft. Each person contributes specific skills, including supervisors who must monitor every single component for quality and precision of manufacture. The completed aircraft must then be air-tested for certification. Only then can it be delivered to the airline.  The ‘Blue Angels’ in FA-18 fighters. The Blue Angels are a special flight demonstration squadron of the US Navy, whose aviation displays for the public are known for the choreographed skills of the pilots and the acrobatic manoeuvres they perform, with up to six jets flying in formation. Powered heavier-than-air craft supported in flight by fixed wings. Aeroplanes are propelled by the thrust of a jet engine, a rocket engine, or airscrew (propeller), as well as combinations of these. They must be designed aerodynamically, since streamlining ensures maximum flight efficiency. The Wright brothers flew the first powered plane (a biplane) in Kitty Hawk, North Carolina, USA, in 1903. For the history of aircraft and aviation, see flight. Design Efficient streamlining prevents the formation of shock waves over the body surface and wings, which would cause instability and power loss. The wing of an aeroplane has the cross-sectional shape of an aerofoil, being broad and curved at the front, flat underneath (sometimes slightly curved), curved on top, and tapered to a sharp point at the rear. It is so shaped that air passing above it is speeded up, reducing pressure below atmospheric pressure, and air passing below it is slower thus increasing pressure and providing a double effect. This follows from Bernoulli's principle and results in a force acting vertically upwards, called lift, which counters the plane's weight. In level flight lift equals weight. The wings develop sufficient lift to support the plane when they move quickly through the air. The thrust that causes propulsion comes from the reaction to the air stream accelerated backwards by the propeller or the gases shooting backwards from the jet exhaust. In flight the engine thrust must overcome the air resistance, or drag. Drag depends on frontal area (for example, large, airliner; small, fighter plane) and shape (drag coefficient); in level flight, drag equals thrust. The drag is reduced by streamlining the plane, resulting in higher speed and reduced fuel consumption for a given power. Less fuel need be carried for a given distance of travel, so a larger payload (cargo or passengers) can be carried. | The shape of a plane is dictated principally by the speed at which it will operate (see aeronautics). A plane operating at well below the speed of sound (about 965 kph/600 mph) need not be particularly well streamlined, and it can have broad wings projecting at right angles from the fuselage. An aircraft operating close to the speed of sound must be well streamlined and have swept-back wings. This prevents the formation of shock waves over the body surface and wings, which would result in instability and high power loss. Supersonic planes (faster than sound) need to be severely streamlined, and require a needle nose, extremely swept-back wings, and what is often termed a ‘Coke-bottle’ (narrow-waisted) fuselage, in order to pass through the sound barrier without suffering undue disturbance. |
| To give great flexibility of operation at low as well as high speeds, some supersonic planes are designed with variable geometry, or swing wings. For low-speed flight the wings are outstretched; for high-speed flight they are swung close to the fuselage to form an efficient delta-wing configuration. |
| Aircraft designers experiment with different designs in wind tunnel tests, which indicate how their designs will behave in practice. In the 1990s fighter jets were deliberately designed to be aerodynamically unstable, to ensure greater agility; an example is the European Fighter Aircraft under development by the UK, Germany, Italy, and Spain. This is achieved by a main wing of continuously modifiable shape, the airflow over which is controlled by a smaller tilting foreplane. New aircraft are being made lighter and faster (to Mach 3) by the use of heat-resistant materials, some of which are also radar-absorbing, making the aircraft ‘invisible’ to enemy defences. |
Construction Planes are constructed from light but strong aluminium alloys such as duralumin (with copper, magnesium, and so on). For supersonic planes special stainless steel and titanium may be used in areas subjected to high heat loads. The structure of the plane, or the airframe (wings, fuselage, and so on), consists of a surface skin of alloy sheets supported at intervals by struts known as ribs and stringers. The structure is bonded together by riveting or by powerful adhesives such as epoxy resins. In certain critical areas, which have to withstand very high stresses (such as the wing roots), body panels are machined from solid metal for extra strength. |
| On the ground a plane rests on wheels, including multiple wheels under the wings and one or more wheels under the nose. For all except some light planes the landing gear, or undercarriage, is retracted in flight to reduce drag. |
| Seaplanes, which take off and land on water, are fitted with nonretractable hydrofoils. |
Flight control Wings by themselves are unstable in flight, and a plane requires a tail to provide stability. The tail comprises a horizontal tailplane and vertical tailfin, called the horizontal and vertical stabilizer respectively. The tailplane has hinged flaps at the rear called elevators to control pitch (attitude). Raising the elevators depresses the tail and inclines the wings upwards (increases the angle of attack). This speeds the airflow above the wings until lift exceeds weight and the plane climbs. However, the steeper attitude increases drag, so more power is needed to maintain speed and the engine throttle must be opened up. Moving the elevators in the opposite direction produces the reverse effect. The angle of attack is reduced, and the plane descends. Speed builds up rapidly if the engine is not throttled back. Turning (changing direction) is effected by moving the rudder hinged to the rear of the tailfin, and by banking (rolling) the plane. It is banked by moving the ailerons, interconnected flaps at the rear of the wings which move in opposite directions, one up, the other down. |
| In planes with a delta wing, such as Concorde, the ailerons and elevators are combined. Other movable control surfaces, called flaps, are fitted at the rear of the wings closer to the fuselage. They are extended to increase the width and camber (curve) of the wings during takeoff and landing, thereby creating extra lift, while movable sections at the front, or leading edges, of the wing, called slats, are also extended at these times to improve the airflow. To land, the nose of the plane is brought up so that the angle of attack of the wings exceeds a critical point and the airflow around them breaks down; lift is lost (a condition known as stalling), and the plane drops to the runway. A few planes (for example, the Harrier) have a novel method of takeoff and landing, rising and dropping vertically by swivelling nozzles to direct the exhaust of their jet engines downwards. The helicopter and convertiplane use rotating propellers (rotors) to obtain lift to take off vertically. |
Operation The control surfaces of a plane are operated by the pilot on the flight deck, by means of a control stick, or wheel, and by foot pedals (for the rudder). The controls are brought into action by hydraulic power systems. An automatic pilot enables a plane to cruise on a given course at a fixed speed. Advanced experimental high-speed craft known as control-configured vehicles use a sophisticated computer-controlled system. The pilot instructs the computer which manoeuvre the plane must perform, and the computer, informed by a series of sensors around the craft about the altitude, speed, and turning rate of the plane, sends signals to the control surface and throttle to enable the manoeuvre to be executed. |
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