Category FLIGHT and M ОТІOIM

One of the most useful military aircraft is the helicopter. Developed toward the end of World War II, helicopters were used in the Korean War (1950-1953) and the Vietnam War (1954-1975). They have been used in all conflicts since.

Helicopters can land combat troops, carry weapons and supplies, evacuate wounded, and fly around a battlefield to support ground troops and destroy tanks. Helicopters rescue air force pilots shot down over enemy territory as well as civilians in trouble on land or off­shore. Naval helicopters may take off from the decks of naval ships to carry out reconnaissance and anti-submarine patrols and to attack enemy ships.

Transportation

The aircraft used by the military to carry troops and equipment are known as transports. Some transports are huge. The U. S. Air Force’s biggest transport is the C-5 Galaxy; only slightly smaller is the C-141 Starlifter. During the Gulf War (1990-1991), the U. S. Air Force air­lifted more than 577,000 tons (523,340 metric tons) of supplies and nearly 500,000 personnel over distances of up to 7,000 miles (11,260 kilometers) to the Middle East combat zone.

The C-130 Hercules is used on shorter – range missions. This sturdy four-engine turboprop transport has been around since 1954. One of its jobs is to drop paratroops, but it also flies as a heavily armed “gunship.” To extend their range, many military airplanes can be refueled in the air by flying tankers, such as the U. S. Air Force’s KC-10.

Military airplanes provide trans­portation wherever people are in danger or in trouble. They fly emergency aid to the victims of hurricanes, earthquakes, and other natural disasters. They evacu­ate civilians from war zones. They bring food, medicines, tents, and other sup­plies wherever there are floods, famines, or fighting.

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SEE ALSO:

• AWACS • Bomber • Fighter Plane

• Helicopter • Missile • Radar

• Stealth

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n airship is a lighter-than-air craft that can be propelled, like a balloon with an engine. An air­ship also has a rudder and fins for steer­ing. Some airships have rigid sides, while others are soft until filled with gas, like a balloon. Airships were used in the first controlled, powered flights.

The First Airships

Before airships were invented, people had developed balloons for air travel. Balloons, however, are not steerable, and they drift with the wind. In the nine­teenth century, aviators tried to build balloons that could be controlled.

French inventor Henri Giffard (1825-1882) built the first airship in 1852. He constructed a cucumber­shaped balloon 144 feet (44 meters) long. The only engine available at the time was a steam engine. Suspended beneath the balloon was a platform on which Giffard fixed a small steam engine that he designed himself to make it as light as possible. The engine drove a propeller, which pushed the airship along at 5 miles per hour (8 kilometers per hour). In this airship, Giffard flew

for 17 miles (27 kilometers). His airship had no way of turning in flight, unfor­tunately, because it had no steering mechanism.

Charles Renard and Arthur Krebs addressed this drawback in 1884. Their airship, La France, had an electric motor plus a rudder and elevator for steering. The inventors proved their airship’s superiority by flying a circular course over Paris, which no balloon could do. This airship was known as a dirigible, from a French word meaning “steer­able.” The name dirigible came to be used for airships in general.

Other airships soon took to the skies. In 1888, Dr. Karl Wolfert of Germany tested the first airship powered by a gasoline engine-an engine already being tested in early automobiles.

The lunar module began its descent toward the target landing site on an area of the Moon called the Sea of Tranquility. By gazing out of the small window, Armstrong was able to choose a
flat landing area. Probes on the lunar module’s legs signaled when it was about 5 feet (1.5 meters) above the dusty surface. The engine cut out, and the Eagle landed on the Moon at 4:17 p. m. (Eastern Daylight Time) on July 20. After touchdown, Armstrong radioed to Mission Control in Houston, Texas: “Houston, Tranquility base here. The Eagle has landed.”

Armstrong and Aldrin wore space – suits to protect them from the Moon’s environment. There is no atmosphere on the Moon—to survive, the men needed the oxygen and steady temperature and air pressure provided by the suits.

Armstrong opened a hatch and climbed down a ladder onto the powdery surface, followed by Aldrin. The astro­nauts’ first steps on the Moon were recorded by a TV camera on the side of the lunar module. Armstrong said,

“That’s one small step for man, one giant leap for mankind.” The astronauts spent two hours on the Moon’s surface, collecting rock samples and setting up scientific equipment. Mission accom­plished, they reentered the Eagle.

The first manned Mercury spaceflight, launched by the United States in 1961, was ballistic. A rocket carried the space capsule into space. Forty-two seconds after liftoff, the rocket shut down, and the capsule separated from it. The cap­sule’s momentum carried it on upward. The capsule did not go into orbit around Earth. Gravity slowed its upward flight until, at a height of 118 miles (190 kilometers), it stopped climbing and began falling. Parachutes opened to slow the capsule’s fall before splashdown in the Atlantic Ocean.

THE BALLISTA

The word ballistic comes from a Greek word meaning "to throw." A weapon called the ballista was invented in ancient Greece in about 400 b. c.e. It was a throwing machine, like a huge crossbow. It hurled heavy stone balls or spears.

A spacecraft coming back to Earth can follow a ballistic trajectory, which simply means that it falls through the atmosphere. A ballistic reentry is uncomfortable for astronauts, however. The strong forces produced by drag slow the spacecraft down suddenly, like a car braking hard. Also, once the spacecraft begins its return to Earth on a ballistic reentry, it cannot be steered toward a particular landing area.

Another way to return to Earth is to use the spacecraft’s shape to create lift instead of letting it fall back to Earth. A spacecraft produces lift simply by tilt­ing, like a kite. As it plunges through the atmosphere, its angle to the oncoming air lifts it up.

A spacecraft returning from space in this way slows down more gently than in a ballistic reentry. By changing the amount and direction of its tilt, the
spacecraft can then be steered through the atmosphere toward a chosen landing site. The Space Shuttle comes back to Earth in this way.

SpaceShipOne, the first private spacecraft, uses a ballistic reentry. When its rocket engine shuts down after launch, at a height of 150,000 feet (45,720 meters), the spacecraft’s momen­tum carries it up another 150,000 feet (45,720 meters). From that point, SpaceShipOne falls back through the atmosphere. The pilot then retakes control and flies the spaceship like a glider to a landing on a runway.

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SEE ALSO:

• Gravity • Lift and Drag • Space­flight • Space Shuttle • Takeoff and Landing

A number of biplane types were still in military service when World War II began in 1939. Most were soon with­drawn, although there were exceptions. The last frontline biplane with the U. S.

Navy was the Curtiss SBC Helldiver, a dive bomber that was still flying at the time of the Japanese attack on Pearl Harbor in 1941. The Curtiss Seagull scout plane served with the U. S. Navy from 1933 until the end of World War II. This aircraft had the unusual distinction of outlasting at least two later designs intended to replace it. So did the Fairey Swordfish torpedo plane, which flew from British aircraft carriers during World War II naval battles, despite hav­ing a top speed of only 138 miles per hour (222 kilometers per hour).

Many wartime pilots learned to fly in a two-seater biplane. The De Havilland Tiger Moth, first flown in 1931, was still in use in the early twenty-first century.

Another very successful trainer biplane was the Boeing/Stearman Model 75, which became the standard World War II trainer for the U. S. military.

О Vintage biplanes are used today for recreation and for aerobatics demonstrations. These airplanes are flying while tied together.

Lloyd Stearman started building biplanes in 1927, and the Stearman Company became part of Boeing in 1939. Being slow and safe to handle, the Boeing/Stearman Model 75 was ideal for pilots who were learning basic flying skills. Ten thousand Model 75s, known unofficially as Kaydets, were built before 1945. After the war, many Model 75s were sold to the air forces of other nations, while others ended up as agri­cultural airplanes.

William Boeing still dreamed of a new, fast airliner. This dream came true in

1933 with the Boeing 247. The 247 is widely regarded as the first “modern” airliner. It was a low-wing, twin-engine monoplane, made completely of metal and with retractable landing gear. The 247 was flown by a pilot and copilot, while a flight attendant catered to the ten passengers. Two Pratt & Whitney Wasp radial engines gave the 247 a speed of 200 miles per hour (320 kilome­ters per hour), and it could fly for 745 miles (1,200 kilometers) before refueling.

By 1934, Boeing was operating an airline and manufacturing aircraft, which was prohibited by a new law (the

1934 Air Mail Act). The federal govern­ment ordered that Boeing be divided, and the company was split into United Aircraft, United Air Lines, and the Boeing Airplane Company.

О Workers install fixtures to the tail fuselage of a B-17 bomber in 1942.

In 1939 Boeing released the elegant 314 Clipper flying boat. Designed for passenger routes over the oceans, the Clipper had a range of 3,500 miles (5,630 kilometers). The same year, how­ever, World War II halted commercial flying between the United States and Europe and brought an end to the flying boat era.

Aircraft manufacturers had begun to design new warplanes some years before World War II began in Europe in September 1939. In May 1934 the U. S. Army issued a specification for a new bomber, and Boeing came up with the four-engine 299, which was first flown on July 28, 1935. Three weeks later, the 299 flew nonstop for 2,100 miles (3,380 kilometers) at an average speed of 252 miles per hour (406 kilometers per hour). Boeing’s delight at this success turned to gloom when, in October, the bomber crashed on takeoff. New prototypes were quickly in the air, however; the Y1B-17, first flown on December 2, 1936, became the B-17 Flying Fortress.

The cockpit is the compartment in an aircraft’s nose where pilots sit to fly the aircraft. It contains the flight controls, engine controls, and instruments that show information about the aircraft. An airliner’s cockpit is also known as the flight deck.

Flight and Engine Controls

Most aircraft have two seats in the cock­pit, side by side. Each seat has its own set of flight controls, so the aircraft can be flown from either one. There is one set of engine controls between the seats.

There are two main flight controls: the control yoke and a pair of foot ped­als. The yoke looks like a car’s steering wheel with the top cut off. Turning the yoke makes a plane bank to one side. Pushing on the yoke makes an airplane’s nose tip down so the plane loses height.

Pulling the yoke back tips a plane’s nose up and makes the plane climb. The pedals control the rudder that is in the tail of an airplane.

Pushing the left pedal turns the plane’s nose to the left. Pushing the right pedal turns the nose to the right.

The main engine control is called the throttle, or power

lever. If the aircraft has more than one engine, there is a power lever for each engine. Moving the power levers changes the amount of fuel supplied to each engine. Giving an engine more fuel makes it run faster and pro­duce more power.

Airbus airliners are unusual because they have no control yokes for steering the plane.

Instead, they are steered by small hand controllers, called side-stick controllers, that look like com­puter game joysticks. There is one on each side of the cockpit.

The finished prototype rolled out for its test flight program in 1949. The Comet looked futuristic compared with the pro­peller planes being used at the time. It was a sleek metal airplane with slightly swept-back wings. Its four turbojet engines fitted neatly into the root of the wing (where the wing joins the fuse­lage), giving the airplane an elegant look. If the Comet flew as fast as

planned, it would surely be a success. Piloted by wartime fighter ace John Cunningham, hired as a De Havilland test pilot, the Comet made its first flight in July 1949. The new jetliner made headlines the world over. Sleek and fast, the Comet seemed to embody the jet age.

After its first flight in 1949, the Comet continued test flights, including long-distance trips from the United Kingdom to Italy, Egypt, South Africa, and Singapore. All went well. On May 2, 1952, the British Overseas Airways Corporation (BOAC) began the world’s first jet passenger service, from London to Johannesburg in South Africa. The

Comet 1 was not a very big airplane: it carried about forty passengers and a crew of four (pilot, copilot, engineer, and navigator). Its attraction was its speed: 150 miles per hour (241 kilometers per hour) faster than the propeller-driven planes then flying the world’s air routes. It also was quieter than the propeller planes it was intended to replace, and it took less time to service between flights. The future appeared bright.

nergy is the ability to do work. In science and engineering, work is done when a force moves an object. The work done to move an air­craft requires energy.

Forms of Energy

There are many different forms of ener­gy. Everything that moves has energy; the energy of movement is called kinet­ic energy. The more massive something is and the faster it moves, the more kinetic energy it has. Something can also have energy because of its position or condition. This is potential energy, or stored energy.

There are different types of potential energy. If a ball is taken up to the top of a hill, work has to be done to move the ball upward against gravity. The ball
thereby acquires gravitational potential energy. The energy stored in a squashed spring is known as elastic potential energy. The type of energy stored in chemicals, including aircraft fuel and rocket fuel, is chemical potential energy.

Kinetic energy and potential energy are both types of mechanical energy. Other forms of energy include heat ener­gy, electrical energy, magnetic energy, light energy, nuclear energy, and sound energy. Heat energy is also called ther­mal energy, and light energy from the Sun is called solar energy.

Energy cannot be created or destroyed. It can only be changed from one form to another. If a ball taken up to the top of a hill is allowed to roll down the hill, its potential energy changes to kinetic energy. If a squashed spring is released, its potential energy changes to kinetic energy. Burning a fuel changes

О This diagram shows how potential energy can turn to kinetic energy when a ball is pushed up a hill and then rolled downward. The ball stores potential energy acquired on the upward journey that is released as kinetic energy on the way down.

WHERE DOES A GLIDER’S ENERGY COME FROM?

Gliders have no engines, so they need to get their energy from another source. Gliders are towed into the air by a cable pulled by a plane or by a winch on the ground. When the cable is released, the glider has a certain amount of energy-part – ly kinetic energy because of its movement and partly gravitational potential energy because of its height. When a glider dives toward the ground, some of its potential energy changes into kinetic energy, and it speeds up.

Energy can be changed in the opposite direction as well. When a pilot makes a glider climb, the aircraft’s kinetic energy changes back into potential energy. In still air, a pilot cannot make a glider climb back up to the same height that it started from, because it loses energy to the surrounding air. The only way a glider pilot can avoid sinking slowly to the ground is to find a new supply of energy. When a glider flies into rising air, it gains potential gravitational energy as the air carries it upward. Then it can convert this into kinetic energy all over again.

its chemical potential energy to heat energy and light energy.

If all the different forms of energy are added up, the total is always the same. When a ball rolls down a hill, the sum of its potential energy and kinetic energy at every instant during its roll stays the same. This is also called the law of conservation of energy. An air­craft is more complicated than a rolling ball, but it follows the same law.

The first airplane to take off from water was the Hydravion, piloted by Henri Fabre of France in 1910. The first sea­plane competition, held in Monaco in 1912, attracted seven entries.

A pioneer of seaplanes in United States was Glenn Curtiss. As early as 1910, he and some friends tried to fit cloth-covered wooden pontoons to an airplane Curtiss had designed, the Aerodrome No. 3 June Bug. The first attempt to land was unsuccessful, but in June 1910, Glenn Curtiss landed on Lake Keuka in a biplane attached to a canoe! Unfortunately, the canoe plane was unable to take off again. Curtiss went on to build floatplanes and flying boats, such as his Flying Fish of 1912. This flying boat set a precedent for later design by having a hydrodynamic hull shape that made take­off from water easier.

О The Dornier Do-X was a luxury passenger flying boat of the 1930s. First built in 1929, it was the largest heavier-than-air aircraft of its day.

The first airplane built by Boeing, the Model 1 (1916), was a floatplane. Many early airplanes were fitted with floats because a watery landing was not likely to smash up the plane’s flimsy structure. Also, airplanes of this era were often forced to land due to bad weather or engine failure or when pilots got lost. There were few airfields, but there were plenty of rivers, lakes, and ocean.

In 1919 a U. S. Navy Curtiss NC-4 fly­ing boat made the first crossing of the Atlantic Ocean. It traveled in stages from May 16 to 31. The NC-4 was a four-engine biplane with a speed of 85 miles per hour (137 kilometers per hour). Three Curtiss flying boats set off from Newfoundland, Canada, but only one reached Plymouth, England, after a jour­ney of 3,925 miles (6,315 kilometers). In 1924 two Douglas World Cruisers flew

JET FIGHTERS

The first and only flying boat fighter plane with jet engines was the Saunders Roe SR/A1. First flown in 1947, this airplane was a twin – engine fighter, intended to operate from water without the need for runways. The SR/A1 managed 512 miles per hour (824 kilometers per hour) but was not agile in air combat because of the extra weight of its boat-shaped hull. It never went into production. A later experiment with a jet fighter on water skis, Convair’s Sea Dart (1953), was similarly disap­pointing. The Sea Dart had extend­able skis for takeoff and landing.

In 1954, it became the first seaplane to fly supersonic, in a shallow dive. The Sea Dart did not meet expectations, however, and the pro­gram was ended in 1956.

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around the world. These airplanes had floats and wheels, and their record­breaking flight took 363 hours.