A little bit of engineering (Несколько текстов для зачёта), страница 13

Aviation

Aviation, term applied to the science and practice of flight in heavier-than-air craft, including airplanes, gliders, helicopters, ornithopters, convertiplanes, and VTOL (vertical takeoff and landing) and STOL (short takeoff and landing) craft (see Airplane; Glider; Helicopter). These are distinguished from lighter-than-air craft, which include balloons (free, usually spherical; and captive, usually elongated), and dirigible airships (see Airship; Balloon).

Operational aviation is grouped broadly into three classes: military aviation, commercial aviation, and general aviation. Military aviation includes all forms of flying by the armed forces—strategic, tactical, and logistical. Commercial aviation embraces primarily the operation of scheduled and charter airlines. General aviation embraces all other forms of flying such as instructional flying, crop dusting by air, flying for sport, private flying, and transportation in business-owned airplanes, usually known as executive aircraft.

Centuries of dreaming, study, speculation, and experimentation preceded the first successful flight. The ancient legends contain numerous references to the possibility of movement through the air. Philosophers believed that it could be accomplished by imitating the wing motions of birds, and by using smoke or other lighter-than- air media. The first form of aircraft made was the kite, about the 5th century bc. In the 13th century, the English monk Roger Bacon conducted studies that led him to the conclusion that air could support a craft in the same manner that water supports boats. At the beginning of the 16th century, Leonardo da Vinci gathered data on the flight of birds and anticipated developments that subsequently became practical. Among his important contributions to the development of aviation were his invention of the airscrew, or propeller, and the parachute. He conceived three different types of heavier-than-air craft: an ornithopter, a machine with mechanical wings designed to flap like those of a bird; a helicopter, designed to rise by the revolving of a rotor on a vertical axis; and a glider, consisting of a wing fixed to a frame on which a person might coast on the air. Leonardo's concepts involved the use of human muscular power, quite inadequate to produce flight with the craft that he pictured. Nevertheless, he was important because he was the first to make scientific proposals.

The practical development of aviation took various paths during the 19th century. The British aeronautical engineer and inventor Sir George Cayley was a farsighted theorist who proved his ideas with experiments involving kites and controlled and human-carrying gliders. He designed a combined helicopter and horizontally propelled aircraft and deserves to be called the father of aviation. The British scientist Francis Herbert Wenham used a wind tunnel in his studies and foresaw the use of multiple wings placed one above the other. He was also a founding member of the Royal Aeronautical Society of Great Britain. Makers and fliers of models included the British inventors John Stringfellow and William Samuel Henson, who collaborated in the early 1840s to produce the model of an airliner. Stringfellow's improved 1848 model, powered with a steam engine and launched from a wire, demonstrated lift but failed to climb. The French inventor Alphonse Penaud produced a hand-launched model powered with rubber bands that flew about 35 m (about 115 ft) in 1871. Another French inventor, Victor Tatin, powered his model plane with compressed air. Tethered to a central pole, it was pulled by two traction propellers; rising with its four-wheeled chassis, it made short, low-altitude flights.

The British-born Australian inventor Lawrence Hargrave produced a rigid-winged model, propelled by flapping blades that were operated by a compressed-air motor. It flew 95 m (312 ft) in 1891. The American astronomer Samuel Pierpont Langley produced (1896) steam-powered, tandem-monoplane models with wingspans of 4.6 m (15 ft). They repeatedly flew 915 to 1220 m (3000 to 4000 ft) for about 1.5 min, climbing in large circles. Then, with power exhausted, they descended slowly to alight on the waters of the Potomac River.

Numerous efforts to imitate the flight of birds were also made with experiments involving muscle-powered paddles or flappers, but none proved successful. These included the early attempts of the Austrian Jacob Degen, who carried out various experiments from 1806 to 1813; the Belgian Vincent DeGroof, who crashed to his death in 1874, and the American R. J. Spaulding who actually received a patent for his idea of muscle- powered flight in 1889.

More successful were the attempts of aeronauts who advanced the art through their study of gliding and contributed extensively to the design of wings. They included the Frenchman Jean Marie Le Bris, who tested a glider with movable wings, the American John Joseph Montgomery, and the renowned Otto Lilienthal, of Germany. Lilienthal's experiments with aircraft, including kites and ornithopters, attained greatest success with his glider flights in 1894-96. In 1896, however, he met his death when his glider went out of control and crashed. Percy S. Pilcher, of Scotland, who had attained remarkable success with his gliders, had a fatal fall in 1899. The American engineer Octave Chanute had a limited success with multiplane gliders, in 1896-1902. Chanute's most notable contribution to flight was his compilation of developments, Progress in Flying Machines (1894).

Additional information on aerodynamics and on flight stability was gained by a number of experiments with kites. The American inventor James Means published his results in the Aeronautical Annuals of 1895, 1896, and 1897. Lawrence Hargrave invented the box kite in 1893 and Alexander Graham Bell developed huge human-carrying tetrahedral-celled kites between 1895 and 1910.

Powered experiments with full-scale models were conducted by various investigators between 1890 and 1901. Most important were the attempts of Langley, who tested and flew an unmanned quarter-sized model in 1901 and 1903 before testing a full-scale model of his machine, which he called the aerodrome. This model was the first gasoline-engine-powered heavier-than-air craft to fly. His full-scale machine was completed in 1903 and tested twice, but each launching ended in a mishap. The German aviator Karl Jatho also tested a full-scale powered craft in 1903 but without success.

Advances through the 19th century laid the foundation for the eventual successful flight by the Wright brothers in 1903, but the major developments were the result of the efforts of Chanute, Lilienthal, and Langley after 1885. A sound basis in experimental aerodynamics had been established, although the stability and control required for sustained flight had not been acquired. More important, successful powered flight needed the light gasoline engine to replace the heavy steam engine.

On December 17, 1903, near Kitty Hawk, North Carolina, the brothers Wilbur and Orville Wright made the world's first successful flights in a heavier-than-air craft under power and control. The airplane had been designed, constructed, and flown by them, each brother making two flights that day. The longest, by Wilbur, extended to a distance of 260 m (852 ft) in 59 sec. The next year, continuing the development of their design and improving their skill as pilots, the brothers made 105 flights, the longest lasting more than 5 min. The following year, their best flight was 38.9 km (24.2 mi) in 38 min 3 sec. All these flights were in open country, the longest involving numerous turns, usually returning to near the starting point.

Not until 1906 did anyone else fly in an airplane. In that year short hops were made by a Romanian, Trajan Vuia, living in Paris, and by Jacob Christian Ellehammer, in Denmark. The first officially witnessed flight in Europe was made in France, by Alberto Santos-Dumont, of Brazil. His longest flight, on November 12, 1906, covered a distance of about 220 m (722 ft) in 21.2 sec. The airplane, the 14- bis, was of his own design, made by the Voisin firm in Paris, and powered with a Levavasseur 40-horsepower Antoinette engine. The airplane resembled a large box kite, with a smaller box at the front end of a long, cloth-covered frame. The engine and propeller were at the rear, and the pilot stood in a basket just forward of the main rear wing. Not until near the end of 1907 did anyone in Europe fly for 1 min; Henri Farman did so in an airplane built by Voisin.

In great contrast were the flights of the Wright brothers. Orville, in the U.S., demonstrated a Flyer for the Army Signal Corps at Fort Myer, Virginia, beginning September 3, 1908. On September 9 he completed the world's first flight of more than one hour and, also for the first time, carried a passenger, Lieutenant Frank P. Lahm, for a 6-min 24-sec flight. These demonstrations were interrupted on September 17, when the airplane crashed, injuring Orville and his passenger, Lieutenant Thomas E. Selfridge, who died hours later from a concussion. Selfridge was the first person to be fatally injured in a powered airplane. Wilbur, meanwhile, had gone to France in August 1908, and on December 31 of that year completed a flight of over 2 hours and 20 minutes, demonstrating total control of his Flyer, turning gracefully, and climbing or descending at will. Recovered from his injuries, and with Wilbur's assistance, Orville resumed demonstrations for the Signal Corps in the following July and met their requirements by the end of the month. The airplane was purchased on August 2, becoming the first successful military airplane. It remained in active service for about two years and was then retired to the Smithsonian Institution, Washington, D.C., at which it is displayed today.

Prominent among American designers, makers, and pilots of airplanes was Glenn Hammond Curtiss, of Hammondsport, New York. He first made a solo flight on June 28, 1907, in a dirigible airship built by Thomas Baldwin. It was powered with a Curtiss engine, modified from those used on Curtiss motorcycles. In the following May, Curtiss flew alone in an airplane designed and built by a group known as the Aerial Experiment Association, organized by Alexander Graham Bell. Curtiss was one of the five members. In their third airplane, the June Bug, Curtiss, on July 4, 1908, covered a distance of 1552 m (5090 ft) in 1 min 42.5 sec., winning the first American award, the Scientific American Trophy, given for an airplane flight. At Reims, France, on August 28, 1909, Curtiss won the first international speed event, at about 75.6 km/h (47 mph). On May 29, 1910, he won the New York World prize of $10,000 for the first flight from Albany, New York, to New York City. In August of that year he flew along the shore of Lake Erie, from Cleveland, Ohio, to Sandusky, Ohio, and back. In January 1911 he became the first American to develop and fly a seaplane. The first successful seaplane had been made and flown by Henri Fabre, of France, on March 28, 1910.

The pioneer airplane flight across the English Channel, from Calais, France, to Dover, England, a distance of about 37 km (about 23 mi) in 35.5 min, was made July 25, 1909, by the French engineer Louis Blériot, in a monoplane that he had designed and built.

During the period before World War I the design of both the airplane and the engine showed considerable improvement. Pusher biplanes— two-winged airplanes with the engine and propeller behind the wing—were succeeded by tractor biplanes, with the propeller in front of the wing. Only a few types of monoplanes were used. Huge biplane bombers with two, three, or four engines were introduced by both contending forces in World War I. In Europe, the rotary engine was favored at first, but was succeeded by radial-type engines. In Britain and the U.S., water-cooled engines of the V type predominated.

The first transportation of mail by airplane to be officially approved by the U.S. Post Office Department began on September 23, 1911, at the Nassau Boulevard air meet, Long Island, New York. The pilot was Earle Ovington, who carried the mail bag on his knees, flying about 8 km (5 mi) to Mineola, Long Island, where he tossed the bag overboard, to be picked up and carried to the post office. The service was continued for only a week (see Airmail).

In 1911 the first transcontinental flight across the United States, from New York City to Long Beach, California, was completed by the American aviator Calbraith P. Rodgers. He left Sheepshead Bay, in Brooklyn, New York, on September 17, 1911, using a Wright machine, and landed at his goal on December 10, 1911, 84 days later. His actual flying time was 3 days, 10 hr, and 14 min.

During World War I both airplanes and lighter-than-air craft were used by the belligerents. The urgent necessities of war provided the impetus for designers to construct special planes for reconnaissance, attack, pursuit, bombing, and other highly specialized military purposes.

Because of the pressure of war, more pilots were trained and more planes built during the 4 years of conflict than in the 13 years since the first flight.

Many of the surplus military planes released after the war were acquired and operated by wartime-trained aviators, who “barnstormed” from place to place, using such fields as were available. Their operations included practically any flying activity that would provide an income, including carrying passengers, aerial photography, advertising (usually by writing names of products on their airplanes), flight instruction, air racing, and exhibitions of stunt flying.