Category FLIGHT and M ОТІOIM

very part of an aircraft has been carefully designed by one or more aircraft designers. The materials used and the shapes of aircraft have changed over the years, but the impor­tance of design remains the same.

Four Aspects of Aircraft Design

There are four main subjects an aircraft designer must understand before an air­craft can be designed: aerodynamics, propulsion, materials and structures, and stability and control.

Aerodynamics is the scientific study of how air flows around an airplane. Propulsion is all about engines, which provide the thrust to move an airplane through the air. Materials and structures
cover what an airplane is made from and how it is built. Stability and control are concerned with how an aircraft flies and how its flight is controlled.

The shape and size of an aircraft depend on what it is designed to do. In other words, form follows function. Airliners have to be big enough to carry a certain number of passengers and their luggage. Fighter planes have to be small, highly maneuverable, and well armed. Cargo planes have to be large and pow­erful enough to carry huge weights of cargo, and they need big doors for load­ing and unloading their cargo easily.

Some use of airships has continued. Graf Zeppelin was briefly used during World War II by the Germans, but it was scrapped in 1940. The U. S. Navy contin­ued to use airships into the 1960s. In 1960 one of its airships flew for 95 hours and 30 minutes without landing or refueling once.

Today, airships are flown mostly for fun or for publicity and media work. There is growing interest, however, in new kinds of airships using modern technology. With modern materials and helium gas, a new generation of airships would be safe, efficient, and able to carry cargo and passengers for very long distances. Cruising at low level, an airship can provide spectacular views for passengers more interested in scenery than fast flight times.

Airships are also environmentally friendly. They use less fuel than air­planes, and they are quiet. Airships do not require airports with runways. Their main disadvantage is their slow speed. Hindenburg (the fastest airship) had a top speed of only 84 miles per hour (135 kilometers per hour). The largest airship currently flying, Spirit of Dubai, a Skyship 600 design, is limited to 50 miles an hour (80 kilometers an hour). Another disadvantage is that airships cannot fly high enough to cross the highest mountain ranges, such as the Rocky Mountains in North America or the Himalayas in Asia.

Current interest in airships focuses on their potential use as floating telecommunications centers or as trans­portation for heavy cargo. A German airship project called CargoLifter pro­poses to carry payloads of about 165 tons (150 metric tons) at a height of 6,560 feet (2,000 meters) for several thousand miles. About the same size as the Graf Zeppelin and Hindenburg, this modern airship can carry three times the payload of those earlier aircraft, because it is much lighter when unloaded. The CargoLifter is semi-rigid, and, instead of a heavy metal frame like a Zeppelin’s, it has a strong lengthwise keel, like a ship. The keel holds the cargo bay, flight deck, crew quarters, and engines.

Aircraft designers are also working on hybrid craft that combine airship and airplane. Such aircraft would need a takeoff run to get airborne, like most airplanes. They would also generate some lift from their shape as well as from the gas inside them. For maximum lift, a hybrid airship would have an effi­cient aerodynamic shape, such as a disk or an aerofoil (flying wing). The airship of the future might well look like the flying saucer of science fiction.

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SEE ALSO:

• Aerodynamics • Balloon • Future of Aviation • Hindenburg

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Date of birth: August 5, 1930.

Place of birth: Wapakoneta, Ohio.

Major contributions: First person to pilot the docking of two space vehicles; first person to set foot on the Moon. Awards: Presidential Medal of Freedom; Congressional Space Medal of Honor; NASA Distinguished Service Medal; Royal Geographic Society Gold Medal; Federation Aeronautique Internationale Gold Space Medal; and many more honors, awards, and honorary degrees.

orn on a farm in rural Ohio, Neil Armstrong took his first airplane flight at age six. He quickly became interested in aviation. Armstrong spent many hours of his childhood building model planes and reading books about flying. He started flying lessons at age fourteen and earned his pilot’s license two years later.

After graduating from high school, Armstrong began studying aeronauti­cal engineering at Purdue University in Indiana. He interrupted his studies to serve in the U. S. Navy from 1949 to 1952. During that time Armstrong flew as a fighter pilot in the Korean War and earned two Gold Stars. After his service in the Navy ended, Armstrong became a civilian again. He graduated from Purdue and became a test pilot for the government. From 1955 to 1962, Armstrong flew more than 1,100 hours, testing many different kinds of aircraft.

In September 1962, Armstrong joined the National Aeronautical and Space Administration (NASA) as an astronaut. He was one of the few civilian astro­nauts. In 1966 Armstrong made history on his first space mission, Gemini 8, when he became the first person to maneuver one spacecraft to dock with another in space.

Early in 1969, Armstrong was named as commander and pilot of the Apollo 11 mission that aimed to take the first peo­ple to the Moon. Also on the crew were Buzz Aldrin and Michael Collins, both experienced astronauts.

On July 16, 1969, the trio blasted off from Florida. A few days later, they

entered orbit around the Moon. Armstrong and Aldrin climbed into the lunar landing craft, the Eagle. Collins remained in orbit aboard the command module, Columbia. The two craft sepa­rated, and Aldrin piloted the Eagle down to the Moon’s surface. Shortly after 4:00 p. m. on July 20, the landing craft touched down. Armstrong announced by radio, “The Eagle has landed.”

For the next six and a half hours, the two astronauts prepared for their his­toric walk on the Moon’s surface. Just before 11:00 p. m., Armstrong stepped down the ladder onto the Moon’s sur­face. As he did so, he said, “That’s one small step for man, one giant leap for mankind.” A camera on the side of the spacecraft displayed the historic step to millions of people around the world watching on television.

Armstrong and Aldrin took some rock samples, set up some experiments, and placed a U. S. flag on the Moon. Fired by rockets, the ascent stage of the lunar module took the astronauts safely back to the Columbia on July 21. The next day, they began the return trip to

О Most of the photos from the Apollo 11 mis­sion were of Buzz Aldrin taken by Neil Armstrong. This is one of the few clear photographs of Armstrong, showing him next to the modular equipment storage assembly of the Eagle.

Earth. Columbia splashed down in the Pacific Ocean on July 24.

Officials worried that the astronauts might bring back some unknown space germs with them. Armstrong, Aldrin, and Collins were held in isolation for more than two weeks. When finally released, they were celebrated in cities across the United States and in many countries around the world.

From 1970 to 1971, Armstrong served NASA in an administrative job. He then resigned and became a professor of aerospace engineering at the University of Cincinnati in Ohio until 1979. Later Armstrong worked for companies in the aerospace industry. Armstrong also helped lead the commission that investi­gated the fatal loss of the Space Shuttle Challenger shortly after takeoff on January 28, 1986.

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SEE ALSO:

• Apollo Program • Astronaut

• Challenger and Columbia • NASA

• Spaceflight

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In a hot air balloon, the heat comes from a propane gas burner. The pilot turns on the burner to send hot air into the balloon. The balloon is made of a tough, nonflammable material such as nylon

BALLOON JUMP

The world’s longest delayed-drop parachute jump was made from a balloon. On August 16, 1960, Captain Joe W. Kittinger jumped out of a balloon 102,800 feet (31,333 meters) above New Mexico. He fell 84,700 feet (25,817 meters) before his para­chute opened. In 1984, Kittinger became the first person to fly the Atlantic Ocean alone in a balloon.

He flew from Maine to Italy in about 86 hours.

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or polyester. The bigger the bag, the more weight (payload) the balloon can lift. Passengers ride in a basket or similar structure hanging beneath the balloon. To descend for landing, the pilot releases air from the top of the balloon. Hot air balloons are popular with sports balloonists.

Gas balloons are usually filled with helium. This gas is safer than hydrogen because it does not catch fire. Gas bal­loons have more lifting power than hot air balloons. They can also go higher and stay aloft longer.

The largest type of gas balloon is a superpressure balloon. The pressure of gas inside the bag is higher than the pressure of the outside air. At launch, a superpressure balloon is only partly filled with gas. As the balloon rises, the gas expands and fills the bag. The

largest such balloons have a volume of more than 70 million cubic feet (2 mil­lion cubic meters), and they are unmanned aircraft.

Today, scientists find unmanned gas balloons useful for studying the weather and the upper atmosphere. Weather bal­loons carry radiosondes—instruments that measure temperature, humidity, and air pressure—which send back data by radio.

There are two kinds of bird flight: flapping and gliding. During flapping flight, the bird beats its wings up and down. The large primary feathers in the wing do most of the propulsion; the smaller secondary feath­ers help to maintain lift. The wings move in two directions while flapping: up and down and in a circular or figure 8 move­ment. The wingtips move faster and farther than the rest of the wings. The smaller the bird, the faster its wings flap.

The downbeat is the power stroke. On the downbeat, the wing feathers overlap closely so that air cannot pass through them but is instead pushed downward. The wing moves downward and forward. The primary feathers are bent back at their tips so the wing performs like a
propeller, pulling the bird forward. Power is produced on the upbeat, too, although less so than on the downbeat. As the wing moves upward, the primary feathers are bent back and move apart a little, fanning open to allow air to slip through the gaps between them. This reduces wind resistance and saves energy.

THE SPEED OF BIRDS

Peregrine falcon: 200 miles per hour (320 kilometers per hour) in a dive.

Spinetailed swift: 105 miles per hour (170 kilometers per hour). Canvasback duck: 65 miles per hour (105 kilometers per hour).

Pigeon: 60 miles per hour (96 kilometers per hour).

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bomber is a military airplane designed to attack targets on the ground or at sea by dropping explosives. A bomb, a metal case filled with high explosives, is just one of the weapons that a bomber can drop. These airplanes also may be armed with mis­siles, rockets, and guns.

Types of Bombers

Most air forces have bombers of two main types: fighter-bombers, also called strike fighters, and strategic bombers. Strike fighters, such as the U. S. Navy F/A-18 and the British Royal Air Force Tornado, can fly as fast as a fighter plane, although how they perform is affected by the weight of the weapons they carry. Their main role is to carry out tactical (battlefield) attacks on troop
concentrations, airfields, bases, ships, and supply routes. Some bombers oper­ate from naval aircraft carriers, while ground-attack airplanes such as the A-10 Thunderbolt fly over a battlefield to destroy tanks, artillery, or other small targets.

Strategic bombers, such as the B-52 and B-1B, are bigger planes. They can fly for 10,000 miles (16,090 kilometers), and even farther when refueling in the air from tanker planes. They are used to attack targets such as factories, military bases, ports, and cities. Even when they fly above 50,000 feet (15,240 meters), these planes are relatively easy to pick up on radar and so risk being shot down by fighters or ground-to-air missiles.

In 1989 the B-2 Spirit stealth bomber gave the bomber a new edge. Its revolu­tionary technology (a flying wing shape and special materials used in construc­tion) enabled it to sneak through radar defenses. Most early bombers had crews of eight or more, but the B-2 needs only two crew members and can

DROPPING BOMBS

A bomber’s weapons may be carried inside the aircraft, in a compartment known as the bomb bay, or attached to the outside of the aircraft. In the early days of air warfare (1914 to 1939), bombs were simply dropped from airplanes over the target area, frequently scattered to increase the chance of actually hitting the target. During World War II, large groups of bombers flew together in formation, often guided to the target by a pathfinder plane that marked the location of the target with flares. Accuracy improved as bombing and navigation equipment became more sophisticated, but bombs still were dropped in a fairly haphazard man­ner. A modern bomber can attack targets many miles away, using elec­tronic guidance systems to send its weapons precisely to their targets. Laser-guided bombs fly along a laser beam directed at the target either from the bomber or from another plane flying nearby.

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Date of birth: January 26, 1892 or 1893.

Place of birth: Atlanta, Texas.

Died: April 30, 1926.

Major contributions: First American woman to gain international pilot’s license; first African American woman to fly in the United States.

nown as “Queen Bess,” Bessie Coleman was the first African American woman to fly and a well-known early stunt pilot. Her example inspired other African Americans to take up flying.

Coleman was one of thirteen chil­dren born to a father who was part Native American and a mother who was African American. When she was nine, her father decided to move to Indian Territory—now the state of Oklahoma-hoping to escape the discrimination that he faced in Texas. Bessie remained behind in Texas with her mother and several sisters. Soon after, she finished elementary school and began working as a laundress. Bessie hoped to continue her education, but she could only afford to attend school for one more semester.

In 1915 Bessie Coleman moved to Chicago, where she joined a brother who lived there. Working in a barbershop as a manicurist, she became friends with Robert S. Abbott, publisher of the Chicago Defender, an important African American newspaper.

Newsreel and magazine stories about the new field of aviation interested Coleman. She applied to flight schools across the United States but was turned down because of her race and gender. Abbott suggested that she obtain the needed training in France, where there was less racial prejudice. Taking his

advice, Coleman learned French and saved her money to pay for lessons. She sailed for France in November 1920.

After several months of training, Coleman received her license to fly and returned to the United States. Black newspapers across the country hailed her as the first female African American pilot. To earn a living, Coleman decided to become a stunt pilot. To be success­ful, however, she needed to learn more tricks. Once again unable to find anyone in the United States to teach her, she returned to Europe early in 1922 for a few more months of training.

Back in the United States once again, Coleman took part in her first air show in September 1922. She was sponsored by Abbott’s newspaper and dazzled the crowd. A few weeks later, she appeared in another show in Chicago and went on to take part in several more.

Coleman dreamed of launching a fly­ing school for African Americans, but she could not afford to buy an airplane until early 1923. The plane she bought was an older model, and it stalled and crashed during a flight. Seriously injured in the crash, Coleman needed eighteen months to recuperate.

In the middle of 1925, Coleman began stunt flying again, putting on a spectacular show in Houston, Texas. Coleman also began touring to give lec­tures to black audiences about the thrill of flying. She hoped to use the fees she received to launch her flying school.

Early in 1926, she managed to buy another plane. Once again, it was an

BESSIE COLEMAN’S LEGACY

Coleman’s bravery and determination inspired African Americans in a time when they suffered from segregation and other forms of dis­crimination. In 1929, pilot William J. Powell and other African American aviators formed the first Bessie Coleman Aero Club. On Labor Day 1931, the club organized an all-black air show in Los Angeles, California. Similar aero clubs were founded in many cities across the country. Also in 1931, a group of African American pilots flew over Coleman’s gravesite in Chicago, a tradition still carried on today. Powell continued to honor Bessie Coleman by promoting avia­tion in the black community.

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older plane, one left over from World War I. The day before an air show in Jacksonville, Florida, Coleman and her mechanic took the plane aloft to test it. A loose wrench fell into the plane’s gears, causing the mechanic-who was piloting the plane-to lose control. The plane flipped over, throwing Coleman to her death. The plane then crashed, killing the pilot.

SEE ALSO: • Aerobatics • Barnstorming • Pilot

When World War II came to an end, hundreds of DC-3s no longer required by the military were quickly snapped up by airlines desperate for aircraft with which to start postwar passenger services. The DC-3 continued to do a valuable job even in the jet age, being used in civil avia­tion, in the military, and in scientific work. In 1956, a DC-3 flown by the U. S. Navy became the first airplane to land at the South Pole, while assisting an Antarctic expedition named Operation Deep Freeze. The DC-3 design was so effective that it never had to be radically altered. The plane did not change much during its sixty-plus years of service.

THE ADAPTABLE AIRLINER

Very few aircraft have been built in as many versions as the DC-3. It is truly one of the great multipurpose aircraft in aviation history, with about 100 different versions developed over the years for dif­ferent tasks. Some of those versions are:

• TC-47B Navigator trainer.

• XC-47 Experimental floatplane.

• AC-47D 1965 version with three 7.62-millimeter machine guns.

• SC-47D Search and rescue model.

• C-53 Skytrooper with twenty-eight seats and glider-towing hook.

• C-53B 1942 version with special Arctic equipment.

• E4D-4 U. S. Navy model, later adapted for electronic countermeasures.

О In 1946, a C-47 is used to take paratroopers on a practice jump at Fort Benning, Georgia.

The flywheel worked well, but it added a lot of extra weight to the engine. Another type of engine, the rotary engine, solved this problem. The engine’s massive cylinders spun around like the spokes of a wheel. The spinning cylinders did the same job as the fly­wheel, so the heavy flywheel was no longer needed. Famous World War I fighter planes, such as the Sopwith Camel, were powered by rotary engines.

The rotary engine was popular because it produced a lot of power for its weight, but it caused some problems. A heavy weight spinning on the nose of an aircraft affects the way it flies. Pilots who flew the Sopwith Camel found that it turned swiftly to the right, but it was much slower to turn to the left.

It also was difficult to build increas­ingly powerful rotary engines. As the cylinders tried to spin through the air, the air pushed back against them. This air resistance, or drag, slowed the cylin­ders down. The engine had to use some of its power to overcome this drag.

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Spinning the cylinders faster or adding more cylinders to produce more power caused even more drag and wasted more of the engine’s power.

orces are pushes or pulls that can cause objects to accelerate or change shape. Aircraft fly because they produce forces that overcome grav­ity and allow them to rise into the air. They move through the air because of the forces produced by their engines. Spacecraft, which are not traveling in air once they leave Earth’s atmosphere, use the force of gravity to move in a circle.

Basics of Force

In everyday language, acceleration means speeding up. To a scientist or engineer, however, acceleration can mean speeding up, slowing down, or changing direction.

If a force acts on an object that is free to move, it makes the object accelerate. The larger the force, the greater the acceleration. Acceleration also depends on mass. A small mass accelerates faster than a big mass pushed with the same force.

Every force has size and direction. Quantities such as these are called vec­tors. Forces acting in the same direction combine to produce an even larger force. When forces act in opposite direc­tions, they produce a force equal to the difference between them. If the forces acting on something exactly balance each other, there is no overall force, and the forces are said to be in equilibrium.

Some forces, such as friction, act when objects touch each other. These are contact forces. Other forces, such as gravity and magnetic forces, work at a distance. The objects that experience these forces need not touch each other. These are noncontact or distance forces.