A little bit of engineering (562404), страница 19

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Modern large commercial-airplane manufacturers—such The Boeing Company in the United States and Airbus in Europe—offer a wide variety of aircraft with different capabilities. Today’s jet airliners carry anywhere from 100 passengers to more than 500 over short and long distances.

Since 1976 the British-French Concorde supersonic transport (SST) has carried passengers at twice the speed of sound. The Concorde flies for British Airways and Air France, flag carriers of the two nations that funded its development during the late 1960s and 1970s. The United States had an SST program, but it was ended because of budget and environmental concerns in 1971.

Military aircraft are usually grouped into four categories: combat, cargo, training, and observation. Combat airplanes are generally either fighters or bombers, although some airplanes have both capabilities. Fighters are designed to engage in air combat with other airplanes, in either defensive or offensive situations. Since the 1950s many fighters have been capable of Mach 2+ flight (a Mach number represents the ratio of the speed of an airplane to the speed of sound as it travels through air). Some fighters have a ground-attack role as well and are designed to carry both air-to-air weapons, such as missiles, and air-to-ground weapons, such as bombs. Fighters include aircraft such as the Panavia Tornado, the Boeing F-15 Eagle, the Lockheed-Martin F-16 Falcon, the MiG-29 Fulcrum, and the Su-27 Flanker.

Bombers are designed to carry large air-to-ground-weapons loads and either penetrate or avoid enemy air defenses in order to deliver those weapons. Some well-known bombers include the Boeing B-52, the Boeing B-1, and the Northrop-Grumman B-2 stealth bomber. Bombers such as the B-52 are designed to fly fast at low altitudes, following the terrain, in order to fly under enemy radar defenses, while others, such as the B-2, may use sophisticated radar-defeating technologies to fly virtually unobserved.

Today’s military cargo airplanes are capable of carrying enormous tanks, armored personnel carriers, artillery pieces, and even smaller aircraft. Cargo planes such as the giant Lockheed C-5B and Boeing C-17 were designed expressly for such roles. Some cargo planes can serve a dual role as aerial gas stations, refueling different types of military airplanes while in flight. Such tankers include the Boeing KC-135 and KC-10.

All military pilots go through rigorous training and education programs using military training airplanes to prepare them to fly the high-performance aircraft of the armed forces. They typically begin the flight training in relatively simple, propeller airplanes and move into basic jets before specializing in a career path involving fighters, bombers, or transports. Some military trainers include the T-34 Mentor, the T-37 and T-38, and the Boeing T-45 Goshawk.

A final category of military airplane is the observation, or reconnaissance, aircraft. With the advent of the Lockheed U-2 spy plane in the 1950s, observation airplanes were developed solely for highly specialized missions. The ultimate spy plane is Lockheed’s SR-71, a two-seat airplane that uses specialized engines and fuel to reach altitudes greater than 25,000 m (80,000 ft) and speeds well over Mach 3.

General-aviation aircraft are certified for and intended primarily for noncommercial or private operations.

Pleasure aircraft range from simple single-seat, ultralight airplanes to sleek twin turboprops capable of carrying eight people. Business aircraft transport business executives to appointments. Most business airplanes require more reliable performance and more range and all-weather capability.

Another class of general-aviation airplanes are those used in agriculture. Large farms require efficient ways to spread fertilizer and insecticides over a large area. A very specialized type of airplane, crop dusters are rugged, highly maneuverable, and capable of hauling several hundred pounds of chemicals. They can be seen swooping low over farm fields. Not intended for serious cross-country navigation, crop dusters lack sophisticated navigation aids and complex systems.

Before the end of the 18th century, few people had applied themselves to the study of flight. One was Leonardo da Vinci, during the 15th century. Leonardo was preoccupied chiefly with bird flight and with flapping-wing machines, called ornithopters. His aeronautical work lay unknown until late in the 19th century, when it could furnish little of technical value to experimenters but was a source of inspiration to aspiring engineers. Apart from Leonardo’s efforts, three devices important to aviation had been invented in Europe in the Middle Ages and had reached a high stage of development by Leonardo’s time—the windmill, an early propeller; the kite, an early airplane wing; and the model helicopter.

Between 1799 and 1809 English baronet Sir George Cayley created the concept of the modern airplane. Cayley abandoned the ornithopter tradition, in which both lift and thrust are provided by the wings, and designed airplanes with rigid wings to provide lift, and with separate propelling devices to provide thrust. Through his published works, Cayley laid the foundations of aerodynamics. He demonstrated, both with models and with full-size gliders, the use of the inclined plane to provide lift, pitch, and roll stability; flight control by means of a single rudder-elevator unit mounted on a universal joint; streamlining; and other devices and practices. In 1853, in his third full-size machine, Cayley sent his unwilling coachman on the first gliding flight in history.

In 1843 British inventor William Samuel Henson published his patented design for an Aerial Steam Carriage. Henson’s design did more than any other to establish the form of the modern airplane—a fixed-wing monoplane with propellers, fuselage, and wheeled landing gear, and with flight control by means of rear elevator and rudder. Steam-powered models made by Henson in 1847 were promising but unsuccessful.

In 1890 French engineer Clément Ader built a steam-powered airplane and made the first actual flight of a piloted, heavier-than-air craft. However, the flight was not sustained, and the airplane brushed the ground over a distance of 50 m (160 ft). Inventors continued to pursue the dream of sustained flight. Between 1891 and 1896 German aeronautical engineer Otto Lilienthal made thousands of successful flights in hang gliders of his own design. Lilienthal hung in a frame between the wings and controlled his gliders entirely by swinging his torso and legs in the direction he wished to go. While successful as gliders, his designs lacked a control system and a reliable method for powering the craft. He was killed in a gliding accident in 1896.

American inventor Samuel Pierpont Langley had been working for several years on flying machines. Langley began experimenting in 1892 with a steam-powered, unpiloted aircraft, and in 1896 made the first sustained flight of any mechanically propelled heavier-than-air craft. Launched by catapult from a houseboat on the Potomac River near Quantico, Virginia, the unpiloted Aerodrome, as Langley called it, suffered from design faults. The Aerodrome never successfully carried a person, and thus prevented Langley from earning the place in history claimed by the Wright brothers.

American aviators Orville Wright and Wilbur Wright of Dayton, Ohio, are considered the fathers of the first successful piloted heavier-than-air flying machine. Through the disciplines of sound scientific research and engineering, the Wright brothers put together the combination of critical characteristics that other designs of the day lacked—a relatively lightweight (337 kg/750 lb), powerful engine; a reliable transmission and efficient propellers; an effective system for controlling the aircraft; and a wing and structure that were both strong and lightweight.

At Kitty Hawk, North Carolina, on December 17, 1903, Orville Wright made the first successful flight of a piloted, heavier-than-air, self-propelled craft, called the Flyer. That first flight traveled a distance of about 37 m (120 ft). The distance was less than the wingspan of many modern airliners, but it represented the beginning of a new age in technology and human achievement. Their fourth and final flight of the day lasted 59 seconds and covered only 260 m (852 ft). The third Flyer, which the Wrights constructed in 1905, was the world’s first fully practical airplane. It could bank, turn, circle, make figure eights, and remain in the air for as long as the fuel lasted, up to half an hour on occasion.

The airplane, like many other milestone inventions throughout history, was not immediately recognized for its potential. During the very early 1900s, prior to World War I (1914-1918), the airplane was relegated mostly to the county-fair circuit, where daredevil pilots drew large crowds but few investors. One exception was the United States War Department, which had long been using balloons to observe the battlefield and expressed an interest in heavier-than-air craft as early as 1898. In 1908 the Wrights demonstrated their airplane to the U.S. Army’s Signal Corps at Fort Myer, Virginia. In September of that year, while circling the field at Fort Myer, Orville crashed while carrying an army observer, Lieutenant Thomas Selfridge. Selfridge died from his injuries and became the first fatality from the crash of a powered airplane.

On July 25, 1909, French engineer Louis Blériot crossed the English channel in a Blériot XI, a monoplane of his own design. Blériot’s channel crossing made clear to the world the airplane’s wartime potential, and this potential was further demonstrated in 1910 and 1911, when American pilot Eugene Ely took off from and landed on warships. In 1911 the U.S. Army used a Wright brothers’ biplane to make the first live bomb test from an airplane. That same year, the airplane was used in its first wartime operation when an Italian captain flew over and observed Turkish positions during the Italo-Turkish War of 1911 to 1912. Also in 1911, American inventor and aviator Glenn Curtiss introduced the first practical seaplane. This was a biplane with a large float beneath the center of the lower wing and two smaller floats beneath the tips of the lower wing.

The year 1913 became known as the “glorious year of flying.” Aerobatics, or acrobatic flying, was introduced, and upside-down flying, loops, and other stunts proved the maneuverability of airplanes. Long-distance flights made in 1913 included a 4,000-km (2,500-mi) flight from France to Egypt, with many stops, and the first nonstop flight across the Mediterranean Sea, from France to Tunisia. In Britain, a modified Farnborough B.E. 2 proved itself to be the first naturally stable airplane in the world. The B.E. 2c version of this airplane was so successful that nearly 2,000 were subsequently built.

During World War I, the development of the airplane accelerated dramatically. European designers such as Louis Blériot and Dutch-American engineer Anthony Herman Fokker exploited basic concepts created by the Wrights and developed ever faster, more capable, and deadlier combat airplanes. Fokker’s biplanes, such as the D-VII and D-VIII flown by German pilots, were considered superior to their Allied competition. In 1915 Fokker mounted a machine gun with a timing gear so that the gun could fire between the rotating propellers. The resulting Fokker Eindecker monoplane fighter was, for a time, the most successful fighter in the skies.

The concentrated research and development made necessary by wartime pressures produced great progress in airplane design and construction. During World War I, outstanding early British fighters included the Sopwith Pup (1916) and the Sopwith Camel (1917), which flew as high as 5,800 m (19,000 ft) and had a top speed of 190 km/h (120 mph). Notable French fighters included the Spad (1916) and the Nieuport 28 (1918). By the end of World War I in 1918, both warring sides had fighters that could fly at altitudes of 7,600 m (25,000 ft) and speeds up to 250 km/h (155 mph).

Commercial aviation began in January 1914, just 10 years after the Wrights pioneered the skies. The first regularly scheduled passenger line in the world operated between Saint Petersburg and Tampa, Florida. Commercial aviation developed slowly during the next 30 years, driven by the two world wars and service demands of the U.S. Post Office for airmail.

In the early 1920s the air-cooled engine was perfected, along with its streamlined cowling, or engine casing. Light and powerful, these engines gave strong competition to the older, liquid-cooled engines. In the mid-1920s light airplanes were produced in great numbers, and club and private pleasure flying became popular. The inexpensive DeHavilland Moth biplane, introduced in 1925, put flying within the financial reach of many enthusiasts. The Moth could travel at 145 km/h (90 mph) and was light, strong, and easy to handle.

Instrument flying became practical in 1929, when the American inventor Elmer Sperry perfected the artificial horizon and directional gyro. On September 24, 1929, James Doolittle, an American pilot and army officer, proved the value of Sperry’s instruments by taking off, flying over a predetermined course, and landing, all without visual reference to the Earth.

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