aircraft carrier Naval vessel equipped with a platform that allows air¬ planes to take off and land. Takeoffs are facilitated by the use of catapults or by a ramp at the end of the flight deck. For landing, aircraft are fitted with retractable hooks that engage arresting wires on the deck, or they are built with vectored-thrust engines that allow them to be landed vertically. Britain’s Royal Navy developed the first true aircraft carrier near the end of World War I, and carriers played leading roles in World War II naval engagements such as the Pearl Harbor attack and the Battles of Midway and the Coral Sea. The largest modern carriers are 1,000-ft (300-m) nuclear-powered vessels of the U.S. Navy, which can carry 100 jet air¬ craft. Other types include the light carrier, equipped for anti-submarine warfare and ground attack, and the helicopter carrier, intended for con¬ ducting amphibious assault.
airplane Fixed-wing aircraft that is heavier than air, propelled by a screw propeller or a high-velocity jet, and supported by the dynamic reac¬ tion of the air against its wings. An airplane’s essential components are the body or fuselage, a flight-sustaining wing system, stabilizing tail sur¬ faces, altitude-control devices such as rudders, a thrust-providing power source, and a landing support system. Beginning in the 1840s, several British and French inventors produced designs for engine-powered air¬ craft, but the first powered, sustained, and controlled flight was only achieved by Wilbur and Orville Wright in 1903. Later airplane design was
affected by the development of the jet engine; most airplanes today have a long nose section, swept-back wings with jet engines placed behind the plane’s midsection, and a tail stabilizing section. Most airplanes are designed to operate from land; seaplanes are adapted to touch down on water, and carrier-based planes are modified for high-speed short takeoff and landing. See also airfoil; aviation; glider; helicopter.
wing
Two physical forces essential to airplane flight are thrust and lift. Jet engines, such as the turbofan shown, provide forward thrust by taking in air through the front of the engine, compressing it, and burning it with fuel in the combustor. Hot exhaust gases and air are then expelled at high speed from the rear of the engine. Lift is generated by the flow of air past the wings. Air flowing over the rounded upper surface of a wing moves faster than air flowing past the flat lower surface; as a result, the air above the wing exerts a lower pressure than the air below, producing a net upward force, or lift. Both lift and drag (friction caused by the plane moving through air) can be adjusted by the movement of ailerons, landing flaps, and tabs on the wings' edges. At the rear of the plane, the elevator, located on the horizon¬ tal stabilizer, controls the airplane's movement around the lateral axis. Both the elevator and the rudder, located on the vertical stabilizer, help to control turning movements initiated by the ailerons.
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airport Site and installations for the takeoff and landing of aircraft. Early airports were open, grass-covered fields, called landing fields, that allowed a pilot to head directly into the wind to aid a plane’s lift on take¬ off and to decrease its speed on landing. In the 1930s heavier airplanes required paved runway surfaces. Larger planes needed longer runways, which today can reach 15,000 ft (4,500 m) to accommodate the largest jet aircraft. Air traffic is regulated from control towers and regional cen¬ tres. Passenger and cargo terminals include baggage-movement and passenger-transit operations.
airship or dirigible Lighter-than-air aircraft with steering and propul¬ sion systems. Airships could be nonrigid (blimps), semirigid, or rigid.
Airedale terrier Dog breed that is the largest of the terriers, probably descended from the otterhound and the extinct Old English terrier. It stands about 23 in. (58 cm) high, weighs 40-50 lbs (18-23 kg), and has a boxy appearance, with a long, squared muzzle. Its coat is dense and wiry, with a black saddle and tan legs, muzzle, and underparts. Intelligent and courageous, powerful and affec¬ tionate (though reserved with strang¬ ers), the Airedale has been used as a wartime dispatch carrier, police dog, guard, and big-game hunter.
airfoil Shaped surface, such as an airplane wing, tail, or propeller blade, that produces lift and drag when moved through the air. An airfoil pro¬ duces a lifting force that acts at right angles to the airstream and a drag¬ ging force that acts in the same direction as the airstream. High-speed aircraft usually employ thin, low-drag, low-lift airfoils; slow aircraft that carry heavy loads use thicker airfoils with high drag and high lift.
Airedale terrier
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compressor core turbine fan fan turbine
jet engine
core
nozzle
air
intake
exhaust
fan air duct
fuel
fan
combustor nozzle
© 2006 Encyclopaedia Britannica, Inc.
34 I 'A’ishah ► Akhenaton
They all included a large cigar-shaped bag or balloon filled with a gas such as hydrogen or helium, a car or gondola suspended below the balloon that held the crew and passengers, engines to drive the propellers, and rudders for steering. Attempts to control the flight of balloons began soon after their invention in the 1780s. The first propeller-driven airship, built by Henri Giffard, flew in 1852 in France; design improvements led to construction of the rigid zeppelin (1900). The nonrigid helium-filled blimp was principally developed by Alberto Santos-Dumont (1873-1932). In 1928 Germany began regular transatlantic airship passenger service. Sev¬ eral explosions, particularly the 1937 Hindenburg disaster, and airplane developments made the airship commercially obsolete. See also balloon.
‘A’ishah \'a-esho\ (bint AbT Baler) (b. 614, Mecca, Arabia—d. July 678, Medina) Third wife of Muhammad. The daughter of his supporter Abu Bakr, she became Muhammad’s favourite wife. Left a childless widow at 18, she became politically active during the reign of the third caliph, ‘Uth- man ibn ‘Affan, leading the opposition that resulted in his murder in 656. She led an army against his successor, 'All, who defeated her in the Battle of the Camel. She was allowed to live her remaining years quietly in Medina and is credited with transmitting more than a thousand HadIth.
Aitken, William Maxwell See Baron Beaverbrook
Aix-en-Provence \,eks-a n -pro-'va n s\ City (pop., 1999: 134,222), southeastern France. Founded as a military colony by the Romans c. 123 bc, it was the scene of the defeat of the Teutons by Marius in 102 bc. Visigoths, Franks, Lombards, and finally Muslim invaders from Spain successively plundered the town. As the capital of Provence, it was a cen¬ tre of culture during the Middle Ages; it became part of France in 1486. It is now a residential suburb of Marseille; its industries include tourism, food processing, and the manufacturing of electrical machinery.
Aix-la-Chapelle See Aachen
Aix-la-Chapelle \,eks-la-sha-'pel\, Congress of (Oct. 1-Nov. 15, 1818) First of four congresses held by Britain, Austria, Prussia, Russia, and France to address European problems following the Napoleonic Wars. At Aix-la-Chapelle (now Aachen, Ger.), the participants accepted an offer by France to pay most of the war indemnity owed to the allies in exchange for the withdrawal of their armies of occupation. France was also admit¬ ted to the new Quintuple Alliance.