Category FLIGHT and M ОТІOIM

On October 31, 2000, the ISS was ready for the arrival of the first astronauts, who came in a Russian Soyuz craft. Expedition One, the first ISS crew, con­sisted of U. S. commander Bill Shepherd and two Russian cosmonauts, Yury Gidzenko and Sergey Krikalyov.

The first crew remained in orbit until March 2001, when Expedition Two arrived in the Space Shuttle Discovery. The crews changed places, and the Expedition One astronauts made a safe return to Earth. The Expedition Two crew remained on the space station until August 2001. Since then, regular exchanges of personnel have been made to maintain a constant three-person crew at the ISS.

О An unpiloted Progress spacecraft approaches the ISS in January 2007, carrying food, fuel, oxy­gen, and other supplies for the ISS crew. Progress spacecraft are destroyed after one mission by burning up on reentry into Earth’s atmosphere.

Today, transportation to and from Earth is supplied by the U. S. Space Shuttle, which will be replaced in the future by the Orion space vehicle. A new Russian shuttle, a European Automated Transfer Vehicle (ATV), and a sim­ilar shuttle spacecraft built by Japan also will take people and supplies to and from the ISS. In addition to the Space Shuttle flights needed to transport new components, fuel, and astro­nauts, unmanned Progress spacecraft arrive at regular intervals to bring supplies and remove waste. Visiting space­craft dock with the ISS, and crew members transfer to the station through an airlock.

Wilbur Wright was born April 16, 1867; Orville on August 19, 1871. As children, the brothers played with a toy helicopter that was driven by a twisted rubber band. Rubber-powered flying machines, invented in the 1870s by Frenchman

Alphonse Penaud, were popular toys. Such toys also helped inspire young inventors, including the Wright brothers. The young Wrights went into business, first as printers and then as bicycle makers. In their spare time, they built and flew kites. They became interested in the possibilities of human flight after reading about the pioneering experi­ments of Otto Lilienthal in Germany and Octave Chanute in the United States.

Lilienthal was killed in 1896 when his glider flipped over in midair. This accident convinced the Wright brothers that Lilienthal’s gliders did not have the right wings or control surfaces for safe, manned flight. They tested different wing shapes in a wind tunnel they built themselves. Then the Wrights brought their gliders from their home in Dayton, Ohio, to Kitty Hawk, North Carolina. Kill Devil Hill, a large sand mound at Kitty

Hawk, was a good place for test flights with few inquisitive spectators.

From 1900 to 1902, the Wrights flew three large gliders that carried a person. Flying the gliders, the brothers learned how to control the flimsy craft, using a system of “wing-warping” (altering the angle of the tips of the wings) to control the balance of the airplane. In the modern airplane, ailerons and elevators are used for this purpose, but the Wrights had to learn by experimenting to overcome the stability problems that had cost Lilienthal his life. In their wing­warping system, wires were attached to the wingtips and fastened to the pilot’s hips. By shifting his body position, the pilot could twist (warp) the tip of the wing to maintain control of the airplane. This method seemed to work in a glider, but would it work in a flying machine powered by an engine?

Building the Flyer

An airplane engine had to be small and light. No vehicle engine of the time was suitable, and so the only option for the Wright brothers was to build their own. They built a gasoline engine with a power output of 12 horse­power (9 kilowatts). The brothers fitted the engine into a flimsy-looking air­plane, much like the gliders they had already flown but with two propellers. They optimistically named their new machine the Flyer.

The Wright Flyer was a biplane with a total wing area of 510 square feet

(47.5 square meters). The wings consist­ed of wood frames covered with cloth. The aircraft’s little gasoline engine was linked by chains to two wooden pro­pellers, each 8.5 feet (2.6 meters) in diameter. One chain was crossed over so that the propeller it drove rotated in the opposite direction to the other. These contra-rotating propellers helped bal­ance the airplane.

The Flyer looked strange compared with most later airplanes. Its “tail” was at the front, and the propellers faced backward, as “pushers.” Very little was known about designing airplane pro­pellers, and the Wrights (who made their own propellers from wood) had to experiment to see which kind worked best. Aviation pioneers copied the screws used on steamships or the sails fitted to windmills, but neither was ideal for an airplane propeller.

To launch the airplane, the Wrights laid down a wooden rail 60 feet (18.3 meters) long. The airplane sat on a dolly-a small cart with two bicycle hubs
for wheels-that ran along the rail. The idea was that, as the engine pushed it along, the Flyer would lift off the dolly into the air and fly.

As high speeds became sought after, an aircraft’s shape became more important. Parts that stuck out into the air flowing around an aircraft had to be removed or smoothed out to reduce air resistance. The wooden struts and bracing wires between biplane wings had to go. Wood and fabric biplanes were replaced by all­metal monoplanes.

By the 1930s, nearly all new aircraft were monoplanes made from duralumin or similar aluminum alloys. Lots of new alloys with different properties were invented for building different parts of aircraft and spacecraft.

О The Boeing P-26A, nicknamed the "peashooter," was the first U. S. Army low-wing monoplane fighter constructed entirely of metal. This full-size peashooter was mounted for testing in a wind tunnel in 1934.

At first metal airplanes were built in exactly the same way as wooden planes. The structure was the same, and only the materials that were used were changed. The new materials made aircraft heavier, however, and a new type of structure was soon devised. Instead of building an airplane’s body from a strong, heavy, metal frame cov­ered with sheets of metal, a lot of the frame was removed. The thin metal skin itself provided some of the plane’s strength. This is called a stressed-skin structure. To make sure the thin skin did not bend or buckle, it had to be fastened securely to the frame with thousands of metal fasteners called rivets.

Mitchell’s work met resistance, however. Senior officers were not yet willing to accept the idea that air power would be important. They were outraged at Mitchell’s charge that battleships had become outdated. At that time, U. S.

battleships were the largest and most powerful ships in any navy. Naval offi­cers insisted that the defense of the United States depended on a fleet of these ships to block any invasion of the nation.

Mitchell countered that the ships could easily be destroyed by air. He campaigned in the press for the right to test his theories. He suggested a simulat­ed attack on a German battleship seized at the end of World War I. In June and July 1921, Mitchell got his chance. In tests, as he had predicted, aircrews sank several ships, including four battleships. “No surface vessels can exist wherever air forces acting from land bases are able to attack them,” Mitchell wrote.

Although proven correct, Mitchell remained unpopular in military circles. He continued to use the press to accuse senior military officers of ignoring air defenses. He toured U. S. naval bases in the Pacific Ocean and issued a stark warning: “If our warships [at Pearl Harbor, Hawaii] were to be found bottled up in a surprise attack from the air and our airplanes destroyed on the ground. . . it would break our backs. The same prediction applies to the Philippines.”

Mitchell’s words proved uncannily accurate years later, when the Japanese severely damaged U. S. ships and grounded airplanes with the 1941 attack on Pearl Harbor from the air.

C In one of Billy Mitchell’s tests to prove the value of air power, an MB-2 aircraft successfully blew up an obsolete battleship in 1921.

Court-Martial

In early 1925, Mitchell’s appointment in the U. S. Air Service expired. Instead of renewing it, army commanders sent him to an isolated military base in Texas. Later that year, the navy suffered two air disasters when a seaplane broke down and a dirigible exploded. Mitchell immediately released a stinging attack on the heads of the navy and the army, accusing them of “almost treasonable negligence of our national defense.”

His superiors had had enough, and they convened a court-martial. Mitchell was charged with insubordination (not obeying senior officers). After a seven – week trial he was found guilty. The ver­dict was suspension from duty for five years, but Mitchell decided to resign from the U. S. Army altogether.

Mitchell spent his remaining years writing and speaking to promote the ideas he had long advanced. He became ill in the mid-1930s and died at the age of fifty-six. During World War II, Mitchell’s basic argument was proven true. Air power proved vital to Allied victory in both Europe and the Pacific.

In April 1942, a few months after the attack on Pearl Harbor, U. S. bombers attacked Japan using B-25s, nicknamed “Mitchells.”

In 1946, ten years after his death, the U. S. Congress voted to award Mitchell a Congressional Medal of Honor, in trib­ute to foresight.

SEE ALSO:

• Aircraft, Military • Curtiss, Glenn

• World War I • World War II

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avigation is the steering or directing of a course. Migrating birds, animals, and even insects seem able to navigate across the world with ease. People have developed ways of using nature, science, and technology to do the same thing—to figure out their position and find their way across land, sea, sky, and even in space.

Following Instinct and Landmarks

Monarch butterflies fly more than 1,500 miles (2,400 kilometers) on their annual migration across North America. One seabird, the Arctic tern, makes the longest migration journeys of any living creature. Every year, it flies up to 22,000 miles (35,400 kilometers) between the Arctic and Antarctic. Some animals are born with an instinct for migrating in a particular direction. Birds may navigate by recognizing familiar landmarks such as rivers and mountains. They also may use the position of the Sun and stars. Yet others seem to be able to sense the Earth’s magnetism, as if they have a nat­ural compass that directs them.

The first pilots relied on navigation methods similar to those used by birds. Planes flew low so that pilots could nav­igate visually by following landmarks such as roads, rivers, and railroads. For longer flights and for flights over oceans, a method called dead reckoning was used. A pilot used a map to figure out which direction to fly and then

measured the distance to the destination. Knowing how fast a plane flew, a pilot could figure out the journey time. If the plane was flown in the right direction (using a compass) at the correct average speed for the calculated length of time, it should arrive at its destination. In the real world however, an aircraft could be blown off course by wind, so pilots had to allow for this when plotting their course. Today, pilots of small aircraft still can navigate using dead reckoning and by looking out for landmarks.

THE STARDUST MYSTERY,

In 1947, an airliner called Stardust was flying from Buenos Aires, Argentina, across the Andes moun­tain range to Santiago, Chile. Just before it was due to land, it van­ished. Searchers found nothing. In 2000, the wreckage was found, and an explanation to the old mystery was pieced together. Because of bad weather, the airliner had flown so high that it reached the high-speed air current of the jet stream and was flying against it. The crew’s naviga­tion calculations indicated that they had crossed the mountains, but the jet stream had slowed them down so much that they were still over the mountains. Thick clouds prevented them from seeing the ground. As they descended to land, the plane crashed into a mountainside and fell onto a glacier, a slow-moving river of ice. The wreck was soon covered with snow and then sank into the glacier. It took fifty-three years for the wreckage to travel downhill inside the glacier and appear at the bottom.

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Professional pilots must have an instru­ment rating. For this, they need to do at least 50 hours of cross-country flying (between one airfield and another). They must be able to fly by visual flight rules (VFR) and instrument flight rules (IFR) using electronic aids. IFR involves instrument training, during which pilots fly using just their instruments so that they will be able to fly even when visi­bility is poor or zero. Commercial pilots also familiarize themselves with the use
of radio, radar, and the landing systems used at airports, such as the microwave landing system (MLS) and the older instrument landing system (ILS).

Before gaining a commercial pilot license (CPL), a pilot must have complet­ed at least 250 hours of flight time, recorded in a personal log book, and must have learned to fly more complex aircraft (with flaps and retractable land­ing gear). The flight examination includes two flight sessions: one in a training aircraft and another in a more complex airplane, although a student may fly the entire test in the complex airplane. Many commercial pilots add a multi-engine rating, which they need to fly aircraft with more than one engine.

The basic principle of radar is very sim­ple. It sends out radio waves and then picks up any waves that are reflected back. Most radar systems are more com­plex, however, and they can tell much more about an object than just the fact that it is there. They can show its loca­tion, bearing (direction), range (dis­tance), velocity, and altitude.

A radar system has four main parts. A transmitter produces radar signals.

An antenna sends signals in the form of electromagnetic waves and picks up any reflections that return. A receiver ampli­fies the weak radar reflections and ana­lyzes them. A display shows the received information on a screen.

Radar uses short radio waves called microwaves. The simplest type of radar is pulse radar. It sends out short bursts, or pulses, of radio waves and listens for any reflections that bounce back from a target, such as an aircraft. The direction from which the reflection comes shows the aircraft’s bearing. The time the pulse takes to bounce back gives its range.

Antennae

A dish-shaped antenna can be steered to scan a particular area of the sky. It may swing back and forth, or it may rotate so that it scans the whole sky in all direc­tions. The most modern radar systems use a flat antenna that stays fixed in one place. A flat antenna is constructed from

О A simple radar has an antenna that sends out signals in the form of pulses of radio waves. It picks up any echo pulses that come back and uses them to measure an object’s distance and movement.

DOPPLER RADAR

When a police car races past sound­ing its siren, the sound rises in pitch as the car approaches and falls as it goes away. This is called the Doppler effect, and it happens with all kinds of waves, including microwaves. Radar equipment can be designed to make use of this effect. It can show if something is flying toward the radar antenna or away from it, and how fast. A type of radar called Doppler radar was developed in the 1960s. It uses continuous radar waves instead of pulses. Pulse – Doppler radar systems combine basic pulse radar systems with Doppler radar.

At first, Doppler radar was used mainly for weather forecasting. By the 1980s, Doppler weather radars were able to measure the speed and direction of raindrops inside clouds and storms. Portable Doppler radars carried on the back of trucks are used to study the most extreme weather systems, especially thun­derstorms and tornadoes.

thousands of small, electronic transmit – and-receive modules, and the radar beam is steered electronically. These radars are called electronically scanned arrays, or phased arrays. They can scan far faster than a rotating dish antenna, they can track many more targets, and – with fewer moving parts-they are more reliable.

Advanced combat aircraft, such as the F-22, are equipped with electronically scanned array radar. They can locate and track multiple high-speed targets and pass on the target information to the air­craft’s weapons systems.

Navigational satellites are very useful pieces of space equipment. They provide the Global Positioning System (GPS) network, which enables pilots, sailors, drivers, and hikers to fix positions almost anywhere on the globe with pin­point accuracy. Developed by the U. S. Department of Defense as NAVSTAR (Navigation Satellite Timing and Ranging Global Positioning System), the GPS uses at least twenty-four satel­lites to make sure that at least four are always within the line of sight of a nav­igator on the ground or ocean. One early navigation satellite, Transit 4A, was the first satellite to carry a small nuclear power plant.

Earth Observation and Weather Satellites

Earth observation (environmental) satel­lites are used to monitor changes in the environment such as melting ice caps, deforestation, and desertification. Earth observation satellites are normally launched into Sun-synchronous polar orbits so that they can survey the entire globe. They can scan for minerals, water, and other resources and record land use

Although accidents do happen, skydiv­ing and parachute sports have a good safety record. Accidents are most com­mon when people jump in poor weather conditions, such as unpredictable winds. Jumping from buildings, cliffs, or other high structures (known as BASE jump­ing) is especially dangerous. Because the modern parachute can be steered, there is little chance of the parachutist landing accidentally in a lake or a tree, as was often the fate of parachutists in the past.

Drop zones in the United States and Canada are required to have an experi­enced person who acts as a safety offi­cer. In most countries, skydivers are required to carry a reserve parachute that has been packed and inspected by a certified parachute rigger. In the United States, certification is provided by the Federal Aviation Administration (FAA).

Many countries have national para­chuting associations, affiliated to the Federation Aeronautique Internationale (FAI). In the United States, skydiving permits and ratings are issued by the United States Parachute Association.

EXTREME SKYDIVING

Specialized forms of skydiving and parachuting include:

• Accuracy landing: Aiming to land on or very near a drop zone target.

• Blade running: Like slalom skiing with a parachute.

• Formation skydiving: Also called relative work (RW).

• Paraskiing: Landing on a snowy mountain on skis.

• Skysurfing: Landing with a surfboard strapped to the feet.

• Stuff jumping: Jumping with

an object, such as a bicycle, which is ridden through the air before the sky – diver lets go and opens the parachute.

The history of aeronautics began long before people understood the principles of flight. The Italian explorer Marco Polo (1254-1324) was one of the first Europeans known to have gone to China. When he returned to Europe in 1295, he told stories of people who flew using giant kites. Kites may have been built in China as long ago as 1000 b. c.e. They are the world’s first aerial vehicles.

Even before Marco Polo, there were people who believed they would fly if they strapped a pair of wings to their arms and flapped like a bird. They tested their ideas by jumping from towers and mountains. Without any real understanding of lift, gravity, or the properties of air, they fell to the ground much faster than expected. Injuries and death were common.

О Samuel Perkins tested man-lifting kites for observational uses by the U. S. Army during World War I. This 1910 photograph shows five Perkins kites holding a man aloft at Harvard Aviation Field in Atlantic, Massachusetts.

One of the most famous of these early “jumpers” was Abbas Ibn Fimas (810-887 c. e.). He lived in Andalusia, now part of Spain. Firnas was an inven­tor who studied chemistry, astronomy, and physics. In 875, when he was sixty – five years old, Firnas built a glider. He made a successful flight, which was seen by a large number of people, but he was injured when the glider hit the ground. This happened about 1,000 years before modern aeronautical pioneers started making successful glider flights.

In the year 1010, an English monk named Eilmer tried to fly from the top of a tower with wings fastened to his arms and feet. Eilmer managed to glide for about 650 feet (200 meters), but he landed badly and broke his legs.

Many of the wings used by early fliers copied the wing shape or flapping action of birds’ wings. Even the great Italian artist and inventor Leonardo da Vinci (1452-1519), who drew designs for flying machines more than 500 years ago, thought the first successful flying machine would have flapping wings.