Category FLIGHT and M ОТІOIM

Modern cruise missiles (missiles with wings and small jet engines) can trace their history back to the flying bombs built during World War II (1939-1945). The V-1 flying bomb was a jet-powered plane without a pilot. It was given the name of “Buzz Bomb” or “Doodlebug”
because of the characteristic buzzing noise its engine produced.

The engine used in the V-1 was a type of jet called a pulsejet. Air entered the engine through shutters, and then fuel was sprayed into it and ignited. The explosion snapped the shutters closed at the front and forced the hot gases out of the engine’s tailpipe. Then the shutters opened, and the process started over again. This happened about 100 times every second.

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STINGERS

The smallest missiles are light enough to be carried by a soldier. Stinger is a portable missile system that soldiers can use to shoot down low-flying air­craft. A soldier holds the launcher on his shoulder and waits for the missile to lock onto the target. When the mis­sile is fired, a small rocket hurls it out of the launch tube. Then the launch rocket falls away, and the main rocket fires at a safe distance from the soldier. The missile accelerates to twice the speed of sound, guiding itself toward the heat given out by the target.

missile test range in New Mexico.

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When the V-1 had flown the right distance to reach the target, a guillotine (sharp blade) cut the cable linked to its elevator, a flap in the V-1’s tail that tilted to control its height. Once the cable was cut, a spring pulled the eleva­tor down and sent the bomb into a dive.

A classic collection of stories from medieval times is One Thousand and One Nights. These tales from Southwest Asia relate the adventures of kings and councillors, fishermen and merchants, soldiers and slaves. In this world of magic and mys­tery, some stories involve that age-old dream of humans flying.

О By the 1800s and 1900s, science fiction had replaced ancient myths and legends about flight. Author Jules Verne described a journey to the Moon and back in From the Earth to the Moon (1865). The launch of Verne’s fictional craft (illustrated here) took place in Florida, which later became the real launch site for the U. S. space program.

MODERN MYTHS

Myths from many different cultures tell of gods who come down to Earth to meet with humans. Some people claim that these stories reveal vis­its from space travelers in ancient times and that some ancient drawings show gods in spaceships or wearing helmets. Scientists dis­miss these claims, however. Today, stories about aliens from other planets focus on unidentified flying objects, or UFOs. Since UFO sightings in Washington and Idaho gained great media attention in 1947, sightings of UFOs have increased dramatically. By the 1950s, some people were beginning to connect UFOs with religious and supernatural beliefs. Claims of UFO sightings are most common in the United States. The kinds of UFOs people report most frequently are flying saucers or moving lights.

О A photograph from the files of the Central Intelligence Agency (CIA) shows what the photographer claimed was a UFO over New Jersey in 1952.

Many UFO images appeared in the period, and there was much doubt about the authen­ticity of the images.

Even a handkerchief will act as a para­chute if strings are tied from each corner to a small weight. The idea may have struck someone far back in history. The Chinese invented the umbrella, and they may have adapted the umbrella shape to try parachuting 1,000 years ago. In around 1485, Italian artist and inventor Leonardo da Vinci drew a cone-shaped

parachute, but it is not known whether his device was ever tested.

The first parachute jumps recorded in Europe were made in 1783 by Sebastien Lenormand of France, who dropped weights and animals from a tower using a parachute that looked rather like a lampshade. In 1797, Andre Jacques Garnerin made a circular parachute of cotton cloth, from which hung a basket for a passenger. On October 22, 1797, he and his parachute were carried aloft by a balloon. Garnerin descended safely from about 2,000 feet (610 meters) above the city of Paris.

In the nineteenth century, parachute jumping from balloons became a popu­lar form of entertainment. Balloon jumper Charles Broadwick invented the first body-pack parachute in 1905. The parachute pack was fastened to the balloon by a line. As the jumper fell, the line tightened and pulled the para­chute canopy open. In 1912, Captain Albert Berry made the first parachute jump from an airplane, at a height of 1,500 feet (460 meters) above St. Louis, Missouri. Georgie Thompson, a teenager who jumped with Broadwick, was the first woman to jump from an airplane and land using a parachute, in 1913.

During World War I (1914-1918) few pilots had parachutes. Generals (and many pilots) argued that parachutes were too cumbersome. Military person­nel who went up in observation balloons did have parachutes, however, so they could leap out if their balloons were hit by enemy gunfire.

HOW A PARACHUTE WORKS

When a parachute opens, air pushes up to fill the canopy. The air acts against the force of gravity and slows the fall of the object to which it is attached. A parachute increases air resistance because it offers a large surface area that produces friction with the air. At first, friction is greater than gravity, so the parachutist slows down. When the friction decreases to the point at which it is equal to the force of gravity, the parachutist descends at a constant speed. In cer­tain weather conditions, the upward force of air may push the parachutist upward for a short time.

Pressure is the pressing effect of a force acting on a surface. Scientifically expressed, pressure is the force per unit area acting on a surface. Pressure (P) is defined as the force applied (F) divided by the area (A) of application. The equation for pressure is: P=F/A.

When a force acts on a material (solid, liquid, or gas), the result is pres­sure. The causes of pressure are as var­ied as the causes of forces. The force of a party balloon squeezing the air inside it produces pressure. The weight of a book pressing down onto a table pro­duces pressure. Oil forced through the pipes of an aircraft’s hydraulic system produces pressure. Gravity pulling air against Earth’s surface produces atmospheric pressure.

Atmospheric Pressure

Atmospheric pressure, or air pressure, can be measured in various ways. The weight of air pressing down on the Earth’s surface produces an air pressure at sea level of 14.7 pounds per square inch (psi), or about 100 kilopascals (100,000 pascals). Meteorologists (weath­er scientists) measure pressure in bars. The air pressure at sea level is about 1 bar, or 1,000 millibars. This pressure also is known as “1 atmosphere.”

Air pressure in the atmosphere falls with increasing height. Gravity pulls air against Earth’s surface. Air at Earth’s surface has the weight of all the rest of

THE BAROMETER

Atmospheric pressure is measured with an instrument called a barome­ter. The first barometer was made in 1643 by an Italian scientist named Evangelista Torricelli (1608-1647). He filled a long glass tube with mer­cury. Then he turned the tube upside down with its open mouth in a bowl of mercury. Some of the mercury ran down into the bowl, but not all of it. A column of mercury about 30 inches (76 centimeters) high stayed in the tube. Its weight was balanced by air pressure acting on the mercury in the bowl. Torricelli realized that changes in the column’s level were due to changes in atmospheric pressure. Mercury barometers work in this way.

An aneroid barometer works in a different way. It is a sealed can with some air taken out. Atmospheric pressure squashes the can. The amount of squashing changes when the air pressure changes. These small movements are linked to a needle pointing at a press scale. Because they do not need a tall tube of mercury, aneroid barome­ters are much smaller than mer­cury barometers.

the air above it bearing down on it, so the pressure is greatest here. Air higher in the atmosphere has less air from above pressing down on it, so the air pressure higher above the ground is lower. This is an important factor to consider for a person flying high in the atmosphere or going into space.

One-fifth of air, or about 20 percent, is oxygen. The thin, low-pressure air at the top of a high mountain contains the same percentage of oxygen as air near the ground, but because there is less air at high altitude, there is also less oxy­gen. The human body is very sensitive to sudden, even small, changes in pressure. Going up a tall building in a fast eleva­tor can make someone’s ears pop. The shortage of oxygen in low-pressure air at high altitudes can cause more severe effects. When people go higher in the atmosphere, they may experience a vari­ety of problems due to low air pressure.

Mountain climbers can suffer headaches, nausea, and dizziness when at altitude.

Controlled spaceflight needs a rocket in which the power can be varied and turned on and off. Liquid-fuel rockets can be controlled in this way. Liquid-fuel rockets are more complicated than solid rockets, because piping, valves, and pumping systems are needed to move the liquid propellants from their storage tanks to the engines. A type of kerosene called RP-1 (Refined Petroleum-1) is a commonly used liquid rocket fuel.

Unlike RP-1, some liquid propellants have to be kept very cold. Hydrogen and oxygen are common rocket propellants. They are normally gases, but they can be packed into very small tanks by chang­ing them into liquids. Hydrogen becomes liquid below a temperature of -423°F (-253°C). Oxygen becomes liquid
below -298°F (-183°C). Liquid oxygen also is called LOX. Propellants that have to be kept super-cold are known as cryo­genic propellants. They are not suitable for most military rockets and missiles because it is difficult to keep them sufficiently cold for long periods, and military equipment always must be kept ready to use. Instead, cryogenic propel­lants are used for civilian spaceflight, such as the Space Shuttle missions, because they are highly efficient, yield­ing a lot of power per gallon.

Some small rockets use propellants that ignite as soon as they meet. These are called hypergolic propellants. Rocket engines that use hypergolic pro­pellants can be very simple and reliable, because they do not need complicated ignition systems. Small rockets called thrusters use hypergolic propellants.

Strange materials have been used as rocket propellants. The Mythbusters tele­vision program, which aims to prove or disprove myths, built a working rocket fueled by a salami. SpaceShipOne, the first privately funded manned space

plane and winner of the Ansari X-Prize, burns rubber as its fuel. The rubber is solid, and the oxidizer, nitrous oxide, is liquid. A rocket like this, with a mixture of solid and liquid (or gas) propellants, is called a hybrid rocket.

Sikorsky struggled during his first few years in the United States. In 1923, with the assistance of several other Russian exiles, he formed Sikorsky Aero Engineering Company to build airplanes.

Within a few years, Sikorsky was build­ing successful aircraft again. His S-29 carried fourteen passengers. With two engines, it could reach a speed of 115 miles per hour (185 kilometers per hour). Sikorsky gave it an all-metal body.

Sikorsky’s company also produced the S-38, a ten-seater that could land on water. Pan American Airways bought several of these planes as the airline began to build its network, providing an air service to South America. Sikorsky based his company at Stratford, Connecticut. He became an U. S. citizen when he was naturalized in 1928.

Sikorsky ran into problems in 1929. He had built and sold several expensive planes, called “flying yachts,” to wealthy businessmen. The planes were not all paid for when, in October 1929, the stock market in New York City crashed.

Most of Sikorsky’s customers lost their fortunes when the stocks they owned plunged in value. As a result, many of the buyers did not make their promised payments. Losing money, Sikorsky sold out to the United Aircraft Corporation. Sikorsky continued to produce planes for Sikorsky Aircraft, which has remained part of what is now United Technologies Corporation (UTC).

Sikorsky’s next achievement was one of his most impressive. In 1931, the company launched the S-40, or the American Clipper. This large flying boat carried four engines. Pan American bought the planes and, by the late 1930s, was using Clippers to provide air service across both the Pacific and Atlantic oceans.

Modern aerobatic aircraft can per­form maneuvers impossible for an ordinary airplane, such as torque rolls (rolling and sliding backward at the same time) or lomcevaks (tumbling end over end). Aerobatic

О The U. S. Navy’s Blue Angels, using F/A-18 Hornets, perform aerobatic movements at an air show in 2006.

planes are strong but very light in rela­tion to the power of their engines. Most use piston engines and propellers.

One outstanding aerobatic airplane is the U. S. Pitts Special. The first Pitts flew in 1947, and since then Pitts Specials have dominated aerobatic competitions. The later versions of this little plane remain close to the original design.

Formation teams perform their dis­plays with as many as sixteen aircraft, although a team of nine or ten is more usual. During a per-formance, aircraft change formations a number of times. They split up into smaller groups, fol­lowing the instructions of the team leader by radio. Pilots often use colored smoke trails to highlight the patterns they are flying.

Famous aerobatic teams include the Blue Angels of the U. S. Navy, the Thunderbirds of the U. S. Air Force, and the Red Arrows of the British Royal Air Force. Unlike other aerobatic performers, military teams usually fly jet planes. These planes fly faster than propeller planes and need more space to display their formations. The Thunderbirds fly the F-16 Fighting Falcon that has a top speed of 1,300 miles per hour (2,092 kilometers per hour).

Accidents are rare, but aerobatics are demanding. Pilots practice constantly to perfect new formations and sequences. They also must keep physically fit to cope with the stress of aerobatics, which subjects their bodies to strong g-forces (acceleration measured as multiples of the force of gravity at Earth’s surface).

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PATTY WAGSTAFF

Born in 1951 in St. Louis, Missouri, Patty Wagstaff flew with the U. S. aerobatics team from 1985 to 1996. She was the first female U. S. National Aerobatic champion, a title she won three times. Wagstaff was International Aerobatic champion in 1993. In 2004, she was elected to the National Aviation Hall of Fame. The Goodrich Extra 260 plane flown by Patty Wagstaff in the 1990s is displayed at the Smithsonian Institution’s National Air and Space Museum. Wagstaff has flown at air shows all over the world and says she likes the precision of aerobatics. "I like flying a perfect loop. . . a per­fect maneuver."

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SEE ALSO:

• Aerodynamics • Barnstorming

• Gravity

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The aerospace industry has cut thou­sands of jobs in recent years, however, because of a drop in orders due to finan­cial problems in the airline industry. A decline in airline business followed terrorist attacks on the United States in 2001. Rising fuel prices also hit airlines hard, and several major U. S. airlines have filed for bankruptcy in recent years.

The aerospace industry has also been troubled by disputes between the United States and Europe over government sub­sidies (payments to offset the cost of developing new aircraft). Boeing, facing stiff competition from the new, giant

Airbus A380, has complained to the World Trade Organization about low – interest loans made to Airbus by the European Union.

The space industry has been hit by uncertainty over plans for the future of manned flights. Programs such as the International Space Station (ISS) and a replacement vehicle for the Space Shuttle, however, continue to create demand and challenge the industry’s best workers. Aerospace manufacturers are facing another challenge, posed by envi­ronmental concerns—how to build quiet and fuel-efficient aircraft for the future.

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SEE ALSO:

• Aircraft, Commercial • Aircraft,

Military • Boeing • Curtiss, Glenn

• Wright, Orville and Wilbur

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Aileron and Rudder

he ailerons and rudder are two of the three control surfaces on an airplane (the third is the elevator). They are the moving parts that steer a plane through the air. The ailerons are panels in the trailing (back) edges of the wings. The rudder is part of an airplane’s tail fin.

Pilots use the ailerons and rudder together to make a turn. They learn how to steer their aircraft smoothly through a turn with the nose pointing in the right direction.

A good air traffic controller needs to have spatial awareness and mathe­matical abilities. Above all, a con­troller must stay calm under pressure.

He or she must be able to absorb data, assess a situation accurately, and make the right decision quickly. Fitness, good vision and hearing, and a clear radio speaking voice are also essential. A controller should be a good team worker because safe air travel requires cooperation from many people. Air accidents are rare, but near misses sometimes do occur. After the attacks of September 11, 2001, terrorism brought a new dimension of risk, adding to U. S. air traffic controllers’ responsibilities.

In 1981 air traffic controllers in the United States went on strike. They were protesting their increasing workload and the stress and dangers of handling more airplanes every year. The federal government dis­missed 10,000 controllers. To reduce pressure, however, a flow control system was introduced. Under this system, an airliner could not leave an airport unless landing space was available at its destination airport at the time it was due to arrive. This eased the stress on controllers who were handling the holding stacks of airplanes waiting to land.

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on a highway. The difference, of course, is that aircraft travel much faster than cars and fly at different heights. Several aircraft may be flying over an airfield while other planes are preparing to land or take off below. For safety, all these aircraft must keep safe distances apart, both vertically and horizontally. The normal vertical distance between air­craft, known as safe vertical separation, is 1,000 feet (305 meters) below 29,000 feet (8,840 meters) and 2,000 feet (610 meters) at altitudes above 29,000 feet (8,840 meters). For planes at the same height, a distance of at least 10 miles (16 kilometers) apart is regarded as safest.

In the United States each ARTCC’s zone is divided into smaller sectors. Around airports, the airspace comes under Terminal Radar Approach Control (TRACON). Each TRACON covers rough­ly a 50-mile (80-kilometer) radius of air­space, and within each airspace is at least one airport. Each airport also has its own airspace, with a radius of 5 miles (8 kilometers). Around some busy inter­national hubs, one main computerized center handles all traffic. London, for example, has one main center that con­trols air traffic in and out of the city’s five major airports.

At a small airport, controllers may have control of aircraft on the ground and in the air around their airfield. Small flight service stations (FSS) help and advise private pilots flying in coun­try districts or from small airfields.

At a larger, busier airport, different types of controllers may be assigned to

various tasks. Tower con­trollers keep a visual watch on aircraft as well as using radar. Approach controllers follow the movements of airplanes approaching and leaving the airfield, usually up to a distance of 50 miles (80 kilometers) and to a height of 10,000 feet (3,050 meters). Area controllers are responsible for planes flying at higher altitudes.

The duties of an air traffic controller include using the radio to pass instructions to pilots about takeoff and landing and to relay weath­er information. Controllers use radar to track airplanes during their flights and plot the locations of aircraft on charts (maps). They check aircraft speed, direction, and altitude and keep a record of all movements and commu­nications. Computers are vital to air traffic controllers for processing and accessing information.

In 1947 the U. S. Air Force became an independent service, free of U. S. Army control. After World War II, jets rapidly replaced propeller aircraft in the world’s major air forces. The first U. S. super­sonic fighter was the F-100 (1953). By 1958 the F-104 could exceed 1,400 miles per hour (2,253 kilometers per hour).

The mid-1940s to the 1970s was the period of the Cold War, when the United States confronted a hostile Soviet Union. Both sides set out on an arms race that included producing new warplanes. Changes in design of this period included the introduction of delta, sweptback, and swing-wing wing shapes. Other developments included the first V/STOL (or jump jet), more powerful engines, and new radars and missiles. Ejection seats were invented to allow a pilot to escape from a damaged airplane, even at high speed and great heights.

Both the United States and the Soviet Union developed giant bombers able to fly nonstop for 10,000 miles (16,090 kilometers). The biggest U. S. bomber was the B-36 (1946). Such bombers were designed to carry nuclear bombs and guided missiles. Planes also had to counter missile attacks-the first U. S. missile built to shoot down enemy planes was the Nike-Ajax of the early 1950s. Some military experts argued that bombers were obsolete (out of date) and that guided missiles would replace the piloted airplane. Strategic nuclear weapons systems were indeed developed,
using land-based and submarine – launched missiles. The piloted bomber did not disappear, however, and the B-52 is still in service today, more than fifty years after its first flight.