Airplane

• 1. Introduction

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  The airplane is a fixed-wing aircraft pushed forward by thrust from a jet engine, a propeller, or a rocket engine. Every year, commercial aviation carries more than four billion passengers and moves over 200 billion tonne-kilometers of cargo. That cargo total is still less than 1% of all the goods the world ships. Most of these machines have a pilot on board, though some, like drones, are flown remotely or by computer.

  In 1903 the Wright brothers built and flew the first one, an achievement recorded as the first sustained and controlled heavier-than-air powered flight. They did not start from nothing. How did a French word for a wing come to name an entire flying machine? Why did men strap on gliders and injure themselves for centuries before anyone left the ground under power? And how did a craft of wood and fabric become an all-metal jet crossing oceans in hours? The answers run through dreamers, engines, and the strange physics of moving air.

• 2. A Word For The Wing

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  First attested in English in the late 19th century, the word airplane appeared before the first sustained powered flight ever happened. It came, like aeroplane, from the French aéroplane, which drew on the Greek ἀήρ, meaning air, and either the Latin planus, meaning level, or the Greek πλάνος, meaning wandering. Originally aéroplane referred only to the wing itself, a plane moving through the air. Through synecdoche, the word for that single part came to stand for the whole aircraft.

  Geography split the spelling in two. In the United States and Canada, airplane describes powered fixed-wing aircraft. In the United Kingdom, Ireland, and most of the Commonwealth, the same machines are usually called aeroplane. According to the Oxford English Dictionary, airplane became the standard U.S. term after the National Advisory Committee for Aeronautics adopted it in 1916, displacing aeroplane on that side of the Atlantic.

• 3. Dreamers And Crashes

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  Around 400 BC in Greece, Archytas was reputed to have built the first artificial, self-propelled flying device, a bird-shaped model driven by a jet of what was probably steam. It was said to have flown some 200 m, possibly suspended for its flight. Long before him, antiquity told of flight through the Greek legend of Icarus and Daedalus and the Vimana of ancient Indian epics.

  The 9th-century Andalusian poet Abbas ibn Firnas and the 11th-century English monk Eilmer of Malmesbury both attempted glides, and both experiments injured their pilots. Leonardo da Vinci studied how birds' wings worked and designed a man-powered aircraft in his Codex on the Flight of Birds of 1502. There he noted for the first time the distinction between a flying bird's center of mass and its center of pressure.

  In 1799, George Cayley set out the concept of the modern airplane as a fixed-wing machine with separate systems for lift, propulsion, and control. He was flying models as early as 1803 and built a successful passenger-carrying glider in 1853. Between 1867 and 1896, the German pioneer Otto Lilienthal became the first person to make well-documented, repeated, successful gliding flights. His flight attempts in 1891 are seen as the beginning of human flight, and his work heavily inspired the Wright brothers.

• 4. Lift Under Power

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  Sir Hiram Maxim built a craft weighing 3.5 tons, with a 110 ft wingspan driven by two 360 hp steam engines turning two propellers. In 1894 he tested it on overhead rails meant to stop it rising, and the test showed it had enough lift to take off. The machine was uncontrollable, and Maxim, presumably realizing this, abandoned the work.

  The Frenchman Clement Ader built the Éole in 1886, a bat-like design run by a lightweight steam engine of his own invention. Its four cylinders developed 20 hp and drove a four-blade propeller, the engine weighing no more than 4 kg/kW. The wings spanned 14 m and the all-up weight was 300 kg. On the 9th of October 1890, Ader attempted to fly it, and historians credit the effort as a powered take-off and uncontrolled hop of roughly 50 m at a height of about 200 mm.

  The Wright brothers' flights of 1903 are recognized by the Fédération Aéronautique Internationale, the standard-setting and record-keeping body for aeronautics, as the first sustained and controlled heavier-than-air powered flight. By 1905, the Wright Flyer III could fly in fully controllable, stable flight for substantial periods. In 1906 the Brazilian Alberto Santos-Dumont flew 220 m in less than 22 seconds, claimed as the first airplane flight unassisted by catapult and certified by the FAI.

• 5. Wings Into War

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  World War I served as a testbed for the airplane as a weapon. The aircraft first proved itself as a mobile observation platform, then as a machine of war able to inflict casualties on the enemy. The earliest known aerial victory with a synchronized machine gun-armed fighter came in 1915, scored by the German Luftstreitkräfte Leutnant Kurt Wintgens. Fighter aces emerged, the greatest by number of aerial combat victories being Manfred von Richthofen, known as the Red Baron.

  After the war, the technology kept advancing. Alcock and Brown crossed the Atlantic non-stop for the first time in 1919, the same year the first international commercial flights ran between the United States and Canada. Airplanes then appeared in every major battle of World War II. They were essential to the strategies of the era, from the German Blitzkrieg and the Battle of Britain to the American and Japanese aircraft carrier campaigns of the Pacific War.

• 6. The Jet Age

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  The first practical jet aircraft was the German Heinkel He 178, tested in 1939. In 1943 the Messerschmitt Me 262, the first operational jet fighter, entered service in the German Luftwaffe. Jet engines became the answer where propellers failed, since the aerodynamic limits of propellers do not apply to jet propulsion. The upper design speed limit for propeller-driven aircraft is Mach 0.6, and faster machines need jets.

  The de Havilland Comet, introduced in 1952, was the first jet airliner. The Boeing 707, the first widely successful commercial jet, stayed in commercial service for more than 50 years, from 1958 to 2010. From 1970 the Boeing 747 reigned as the world's biggest passenger aircraft until the Airbus A380 surpassed it in 2005.

  Supersonic airliners faced a harder road. Flights of the Concorde were limited to over-water routes at supersonic speed because their sonic boom is prohibited over most populated land. High operating cost per passenger-mile, together with a deadly crash in 2000, led its operators to withdraw the Concorde from service.

• 7. Engines That Push

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  An aircraft propeller, or airscrew, turns rotary motion from an engine into a swirling slipstream that pushes it forward or backward. Its thrust depends partly on disk area, the area swept by the blades, and its limit is the speed of sound, because when a blade tip passes that speed, shock waves cut efficiency. Three engine types drive propellers: reciprocating piston engines, gas turbines, and electric motors. Reciprocating engines come in radial, in-line, and flat configurations, the radial arranging cylinders outward from a central crankcase like the spokes of a wheel.

  Most jet aircraft use turbofan engines, in which a gas turbine drives a ducted fan, with the ratio of air passing around the turbine to that going through it called the by-pass ratio. Airliners use high by-pass engines for fuel efficiency, while jet fighters use low-bypass turbofans. A ramjet contains no major moving parts and needs forward motion before it can produce thrust, useful for missiles. A scramjet uses internal supersonic airflow, and the experimental NASA X-43 set a world speed record in 2004 for a jet-powered aircraft at Mach 9.7, nearly 7500 mph.

  Rocket aircraft carry their own oxidizer rather than drawing oxygen from the air. In World War II the Germans deployed the Me 163 Komet, and in 1948 the Bell X-1 became the first plane to break the sound barrier in level flight. In the 1960s the North American X-15 broke many speed and altitude records and pioneered engineering concepts for later aircraft and spacecraft.

• 8. Shaping The Airframe

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  The structural parts of a fixed-wing aircraft are called the airframe. Early types were usually wood with fabric wing surfaces, and as engines arrived around a hundred years ago their mounts were made of metal. More and more parts turned to metal as speeds rose, until all-metal aircraft were common by the end of World War II, with composite materials growing in modern times. A typical airframe carries one or more wings, a fuselage, a vertical stabilizer mounting the rudder, a horizontal stabilizer mounting the elevators, and landing gear of wheels, skids, or floats.

  Wings began weak. Early engines had little power and lightness mattered, and early airfoil sections were too thin to hold a strong frame, so until the 1930s most wings needed external bracing struts and wires. As engine power grew through the 1920s and 30s, wings could be built strong enough to drop the bracing, giving the cantilever wing. A monoplane has one wing plane, a biplane two stacked together, while the three-winged triplane gained some fame in World War I. At transonic speeds, sweeping a wing back or forward reduces drag from supersonic shock waves.

  The flying wing, a tailless craft with no definite fuselage, was studied heavily in the 1930s and 1940s by Jack Northrop and Cheston L. Eshelman in the United States and by Alexander Lippisch and the Horten brothers in Germany. Renewed interest in the 1980s came from the low radar reflection of such shapes, and fly-by-wire systems tamed their aerodynamic drawbacks. That path led to the Northrop B-2 Spirit stealth bomber, an efficient and stable long-range design built on the oldest idea in flight, the wing itself.