Category FLIGHT and M ОТІOIM

One of the most important decisions to make is how fast a new aircraft will fly, because this affects its shape and the engine power it needs. It may also affect the choice of materials from which a plane will be built. Aircraft speeds are divided into bands that cover the slowest to the fastest: low speed, medium speed, high speed, super­sonic, and hypersonic. These speed bands are also known as regimes of flight.

О The C-5 Galaxy transport plane is the U. S. Air Force’s largest aircraft. It was designed specifically to accommodate huge cargo, such as this container being loaded at an air force base in Delaware.

An airplane designed to fly well at very high speeds is not generally good at flying slowly, so the designer must choose which is more important. Some aircraft have to perform well at both low speeds and high speeds, however. One way of achieving this is to make the plane change shape. The F-14 Tomcat and Tornado fighter bombers have wings that stick straight out to the side at low speeds but then swivel back as the plane goes faster. These aircraft are variable geometry, or swing-wing, planes. Swing-wing planes are not very common, because the machinery that moves the wings adds extra weight to the aircraft.

Dates of birth: Alcock: November 6, 1892; Brown: July 23, 1886.

Places of birth: Alcock: Manchester, United Kingdom; Brown: Glasgow,

United Kingdom.

Died: Alcock: December 18, 1919;

Brown: October 4, 1948.

Major contribution: Flew the first nonstop flight across the Atlantic Ocean, 1919.

Awards: Alcock: Distinguished Service Cross and Knight Commander of the British Empire; Brown: Knight Commander of the British Empire.

ohn Alcock was raised just outside the large English city of Manchester and trained to become an auto mechanic when he finished school. His employer encouraged the young Alcock in his interest in airplanes. Alcock was then hired by French aviator Maurice Ducrocq to be a mechanic. Ducrocq taught him how to fly, and Alcock obtained a pilot’s license at age twenty.

Prisoners of War

When World War I began in 1914, Alcock joined the Royal Naval Air Service. At first, he was a flight instruc­tor, but he soon became a pilot. In Europe in 1917, Alcock shot down two German planes, for which he won a Distinguished Service Cross. Later the same day, on another mission, his own plane suffered engine trouble. Alcock was forced to crash land in Germany and was captured. He remained a German prisoner until the war ended in November 1918.

There were some striking similarities in the early lives of Alcock and Brown even though their beginnings were dif­ferent. Arthur Whitten Brown was born to American parents in Scotland, part of the United Kingdom. His family then moved to Manchester, where Alcock was raised. Trained as an electrical engineer, Brown became interested in aviation and joined the Royal Flying Corps early in World War I. Brown was shot down over Turkey in 1915 and he lived as a prisoner of war for two years.

An astronaut is a person who travels in space. The word astro­naut means “star traveler.” The Russians (who, as part of the Soviet Union, led the way in manned space­flight in the early 1960s) use the name cosmonaut for their space travelers.

Astronaut Profile

Almost all people who have traveled in space are trained to be professional astronauts. A few people fly as passen­gers, however, after a short period of preparation for spaceflight. Most of the first astronauts came from a military background, but astronauts today include civilian specialists in engineer­ing, space medicine, electronics, and other fields of science. Most astronauts today fly in the Space Shuttle or are sta­tioned aboard the International Space Station (ISS).

The United States and the former Soviet Union have sent more astronauts into space than any other nation. A number of other nations’ astronauts have flown on U. S. or Soviet missions. A few countries, such as China, have launched their own astronauts.

Astronauts must be well educated and physically fit. Many astronauts are experienced aviation pilots. During space training, they experience weight­lessness (being without gravity) to get used to conditions in space. Before every mission, the selected crew of astronauts and their backup crew practice the tasks

TYPES OF ASTRONAUT

Space Shuttle astronauts are desig­nated in one of three categories: pilots, mission specialists, or payload specialists. Pilots are highly trained flight professionals with jet aircraft experience who are in charge of the spacecraft. They operate and navi­gate the spacecraft and keep its occupants safe. A mission specialist carries out tasks and operates onboard equipment. Mission special­ists, for example, will use robotic arms or even leave a spacecraft to perform repairs. They take care of any payload, such as scientific equipment, that is being taken into space. Payload specialists are usually scientists rather than professional astronauts, and they are in space to perform a particular experiment or task.

that will be carried out in space. This training often takes place in simulators that use computerized virtual displays to give astronauts some experi­ence handling situations that might occur during a spaceflight. Trainee astronauts also work inside a full-size model of their spacecraft to familiarize themselves with its layout and fea­tures. When fully trained, an astronaut may have to wait a long time before being assigned to a mission.

There are world and national champion­ships for both hot air and gas balloons. Like airplane pilots, balloon pilots in the United States must be licensed by the Federal Aviation Administration.

In 1978, Ben Abruzzo of the United States and two companions made the first flight in a balloon across the Atlantic Ocean, in the helium balloon Double Eagle II. In 1981, Abruzzo also became the first balloon pilot to fly the Pacific Ocean, in his Double Eagle V.

The Pacific crossing of 5,768 miles (9,310 kilometers) took 84 hours and 31 minutes. The first Atlantic crossing by a hot air balloon was made in 1987, by Richard Branson of Britain and Per Lindstrand of Sweden. They also made the first trans-Pacific flight in a hot air balloon, in 1991.

The first balloonists to circle Earth were Bertrand Piccard of Switzerland and Brian Jones of Britain. They made the record-breaking flight of 26,602 miles (42,802 kilometers) between March 1 and March 20, 1999, in their balloon Breitling Orbiter III.

SEE ALSO:

• Airship • Montgolfier, Jacques-

Etienne and Joseph-Michel

• Parachute

Gliding uses less energy than flapping. The bird stretches its wings and coasts through the air, as gulls do when return­ing to their cliff-top roosts at sunset. Gliding birds can also soar (rise high) by seeking out rising currents of air, or thermals. Vultures using thermals circle effortlessly for hours at a time, and they can soar very high-one African vulture collided with an airplane at 37,000 feet (11,280 meters). Birds soar, too, on uplifts of air pushed up by a hillside or cliff or formed where blocks of warm and cold air meet.

Seabirds, such as gulls, make use of the different wind speeds in the air above the ocean. Over the sea, wind speed is reduced close to the water because of friction with the waves. The fastest wind speeds are usually between 50 and 100 feet (15 and 30 meters) above the waves. Some seabirds, such as fulmars, use these faster-moving winds to pick up speed and then glide down with the wind behind them to skim low above the water. Their momentum takes them up again into the wind. For such maneuvers, long wings provide stability as well as high speed.

Hovering

Some birds can hover in the air, using their wings and tail to maintain posi­tion. They hover usually to feed or spot prey below. Kestrels and terns can do this, but the hovering champion is the hummingbird, which not only hovers, but is the only bird able to fly backward.

Hummingbirds hover by beating their wings backward and forward so fast that they produce lift without propulsion. In this way, the bird stays in one place when feeding from flowers. Kestrels use a slightly different hovering technique. This bird flies into the wind at exactly the same speed as the wind, so that one force balances the other.

The U. S. Army obtained its first airplane, a Wright Flyer, in 1909. For almost two years, this was the only plane in what the Washington Star newspaper called the nation’s “aerial fleet.” In 1911 Lieutenant Riley Scott invented a bomb-

sight (a device for aiming bombs) made of nails and wire. He tested it using bombs held in a canvas sling beneath the airplane, and he managed to drop them within 10 feet (3 meters) of a 5-square-foot (0.5-square-meter) target from a height of 400 feet (122 meters). The army was not impressed.

Other people saw a future for bombers, however. In 1911 an Italian army officer named Giulio Douhet described how airplanes could attack an enemy’s communications and supply routes. The Italians were the first to use planes for bombing, in 1911, when one of their airplanes dropped four bombs on a Turkish camp in North Africa dur­ing a war between Italy and Turkey.

ommunication—the conveying of information-is essential to avia­tion and spaceflight. It would be almost impossible to communicate in these fields without radio. Pilots and astronauts use radio to communicate with each other and with air traffic, or mission, controllers on the ground. Aircraft and spacecraft also send and receive text and data by radio.

Commercial aircraft carry a variety of communications equipment. Aircraft crews use some equipment to talk to air traffic controllers and other pilots. Other equipment is used for sending and receiving text messages.

How Radio Works

Information sent by radio travels as a stream of invisible energy waves mov­ing at the speed of light, which is

186,0 miles per second (300,000 kilo­meters per second). A radio wave is actually two waves, one electrical and one magnetic, traveling together. A wave of this kind is called an electro­magnetic wave. Other electromagnetic waves include light and X-rays. The only difference between the different waves is their lengths—radio waves are longer than the other types of waves.

The length of a radio wave is referred to as its wavelength. The number of waves passing by every second is called the frequency. Radio frequency is meas­ured in waves per second, also called cycles per second, or hertz.

Radio signals are divided into fre­quency bands. The high frequency (HF) and very high frequency (VHF) bands are used for aircraft communications. A radio signal is transmitted at a particu­lar frequency, or waves per second. To receive the signal, a radio has to be tuned in to the same frequency. Airports and air traffic control centers have their own radio frequencies. During a flight, a pilot has to keep retuning a plane’s radio to match local frequencies.

VHF signals travel in a straight line from transmitter to receiver. When a transmitter and receiver are no longer in line because an airplane has traveled below the horizon, VHF radio contact is lost. Pilots can use VHF radio to talk to air traffic controllers up to only 230 miles (370 kilometers) or so away.

HF radio is used for communicating over longer distances. HF signals can travel beyond the horizon, because they bounce off a layer of Earth’s atmosphere called the ionosphere.

TECH lbTALK

FREQUENCY BANDS IN AVIATION

Band: High frequency (HF).

Frequency: 3-30 megahertz.

Band: Very high frequency (VHF). Frequency: 30-300 megahertz.

(1 megahertz = 1 million hertz)

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О This diagram shows the wavelength and fre­quency measurements for electromagnetic waves. Radio waves are long compared to X-rays, and so their frequency is comparatively low.

A radio link for sending signals up to an aircraft or spacecraft is called the uplink. A radio link for sending signals from an aircraft or spacecraft down to the ground is the downlink. The infor­mation to be sent by radio-whether a pilot’s voice or data from instruments-is added to a radio signal called a carrier wave. The information changes, or mod­ulates, the carrier wave. When the radio signal is received, the carrier wave is filtered out, leaving the voice or data.

DC-3s flown during the Korean War in the early 1950s and in the Vietnam War of the 1960s and 1970s looked, on the out­side, the same as the DC-3s that flew across the battle­fields of World War II. Inside, many changes were made as technology impro­ved. Radar and electronic equipment were updated. In some military variants, heavy machine guns were fitted so the airplane could operate as a low-flying gunship. There also were many updates to the engines over the years.

The last DC-3 was delivered from the factory in 1946, but there are still hun­dreds of DC-3s flying in many countries around the world, carrying passengers and cargo. Perhaps more than any other airplane, the DC-3 established flying as a safe, affordable, and popular form of transportation.

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SEE ALSO:

• Aerospace Manufacturing

Industry • Aircraft, Commercial

• Aircraft, Military • Aircraft Design

• Boeing • Engine • Materials and

Structures • World War II

After World War I, other types of engines began to replace the rotary engine. One of these was the radial engine. A radial engine looks like a rotary, but the radial engine’s cylinders do not spin.

Radial engines were made smoother and more powerful by adding more

cylinders. The most popular rotary engines of the time had nine cylinders, but the biggest radial engines used in aircraft had up to twenty-eight cylin­ders. Big radial engines caused a lot of air resistance, or drag. The drag was reduced by fitting a streamlined cover, called a cowling, over the engine to deflect air around it.

Radial engines were popular until the 1940s, when there was another change in aircraft design. Designers wanted to create faster, more streamlined planes, so they needed a slimmer engine than the radial to fit inside the slender nose of the aircraft. They chose the inline engine. Its cylinders are in a straight line, like a row of bottles. Bigger inline engines had two rows of cylinders meet­ing at the bottom, forming the shape of a letter V. An inline engine with two rows of six cylinders—twelve cylinders in all—is called a V-12.

When World War II began in 1939, fighters were powered by radial engines. By the end of the war in 1945, faster fighters such as the P-51 Mustang and the Spitfire were using V-12 engines. Radial engines continued to be used by bigger, slower bombers and airliners.

Friction is a force that resists movement. It is caused by surfaces catching or lock­ing together as they try to slide against each other. The size of the force depends on the roughness of the surfaces and on how much force is pushing them together. Friction between objects that are stationary is called static friction. Friction between objects sliding against each other is called dynamic friction, or kinetic friction.

Friction is vital in some places but unwanted, or even damaging, in other places. People, cars, bicycles, and other
land vehicles depend on friction between them and the ground to move around. Friction stops feet and wheels from slipping and gives them something to push against.

Inside engines, however, friction is not wanted. It slows down moving parts as they try to slide over each other. It also causes wear and overheating as sur­faces rub together. One way to reduce friction is to use oil to make surfaces more slippery. Using oil to reduce fric­tion is called lubrication, and the oily liquids used are known as lubricants.