Category FLIGHT and M ОТІOIM

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 Some military experts argued that bombers were obsolete (out of date) and that guided missiles would replace the piloted airplane.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.

Passengers entering an airport must check in with their airline. On many
international flights, check-in time may be two or more hours before takeoff because of growing security measures at the world’s airports.

At the check-in desk, passengers’ baggage is weighed and labeled. Each passenger is allocated a seat in the plane and given a boarding pass. Baggage is checked by machines and security per­sonnel before being loaded into the baggage hold of the airplane. Security became a serious issue in the 1970s after a number of attempts by terrorists to hijack airliners. Even tougher security came into force at airports after the ter­rorist attacks of September 11, 2001. All airlines now impose strict regulations on what air travelers are allowed to carry, especially in small hand baggage taken into the cabin.

At the airport, passengers pass ^ through security gates before boarding their plane. Security checks involve body scanning and X-rays of all hand baggage. |jw Passengers may be asked to remove shoes, belts, and metal objects before they pass through the electronic scanning gates. Security officers make sure no weapons or explosives get on board the plane.

Passengers move through into

a departure zone to wait for their [___ .

flight. In large airports, they may ride from the main terminal to a smaller satellite terminal on a shuttle bus, monorail, or electric vehicle. While they wait, passengers can usually eat or shop in the airport facilities. They can check their departure information on monitors (each airline flight has a number to identify it).

The next step was the Apollo program itself. Launched in 1967, the program began with a disaster. Apollo 1 was being prepared for launch when, on January 27, 1967, its three-person crew climbed into the command module to perform a systems test on the ground. During the tests, a fault in the wiring started a fire. The module had been flooded with pure oxygen, which caused the fire to spread in an instant. Astronauts Ed White, Gus Grissom, and Roger Chaffee were trapped inside, unable to open the hatch in time to escape the flames. All three men died.

After a break in the program for investigation into the accident, NASA quickly redesigned the Apollo spacecraft with several added safety features. When the Apollo program resumed in late

1967, the unmanned Apollo flights 4, 5, and 6 tested the rocket and modules for safety and reliability. (There were no Apollo flights numbered 2 or 3.)

The first manned Apollo flight, by Apollo 7, took place in Earth orbit in

1968. Later that year, Apollo 8 flew around the Moon ten times and returned to Earth safely. In 1969, the landing module was tested in Earth orbit by the crew of Apollo 9. Apollo 10 repeated the

Apollo 8 mission, this time completing thirty-one lunar orbits. During the Apollo 10 mission, two astronauts flew the lunar module within 47,000 feet (14,300 meters) of the Moon’s surface.

Type of aircraft: Airborne Warning and Control System (AWACS). Manufacturer: Boeing.

Maiden flight: 1972.

Use: Military surveillance and command center.

WACS stands for Airborne Warning and Control System. An AWACS is an airplane that is used as a flying radar station and control center. Its jobs are to alert air defenses of incoming enemy aircraft or missiles and to provide a flying opera­tions command center.

Before radar was first fitted to air­craft in the 1940s, pilots had to rely on their eyesight to spot enemy forces. The first planes to use radar in combat were World War II night fighters. In the 1950s, radar was fitted to naval
airplanes and land-based patrol air­planes. They used radar to hunt enemy submarines and detect enemy ships and aircraft. In the 1960s the idea was taken a step further, and this led to AWACS.

U. S. defense planners feared an enemy attack might destroy or damage ground-based radar and communica­tions systems. The answer was to put a radar-based electronic system in a large airplane that could become an “eye in the sky” for commanding officers on the ground.

The U. S. Air Force ordered a conver­sion of a Boeing 707 airliner to become an AWACS. The first of these aircraft came into service in 1977. Named the E-3A Sentry, it looked like a 707 with one very obvious addition: a large,

mushroom-shaped rotodome on top. Inside the rotodome was radar and other electronics equipment. Other electronic gadgetry was packed into the wings, cabin, and tail of the airplane.

AWACS airplanes usually carry a crew of four and up to thirteen elec­tronics warfare specialists. Consoles inside the aircraft display computer – processed data on screens. Missions last eight hours or longer. The aircraft can be refueled in flight by a U. S. Air Force tanker, and crew members can take breaks in the plane’s rest area.

AWACS planes track enemy aircraft and ships and identify friendly forces. They can also listen in to enemy com­munications. Their radar has a range of more than 250 miles (400 kilometers) when tracking low-flying targets. At high altitudes, AWACS can detect a plane or missile at even longer ranges. Information is relayed to military com­manders, battlefield control centers, and even to the president and the secretary of defense. AWACS communications are jam resistant, which means they cannot be blocked by enemy electronic counter­measures. AWACS surveillance operates alongside spy satellites and robot drones, which are also used to gather military information.

The E-3A Sentry is still used by the U. S. Air Force, which had thirty-three AWACS planes as of 2006. Some of these are deployed overseas in combat zones. The AWACS E-3A Sentry is also used by NATO, the British Royal Air Force, and the air forces of France, Chile, and Saudi

TECH’^TALK

THE E-3A SENTRY

The E-3A Sentry is a modified

Boeing 707/320. It has:

• Four Pratt & Whitney turbofan engines.

• A rotodome 30 feet (9 meters) in diameter that rotates at six revolutions per minute in normal operations.

• A cruising speed of 530 miles per hour (853 kilometers per hour).

• An operational height of 29,000 feet (8,840 meters).

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Arabia. The Japanese Air Self-Defense Force uses a Boeing 767 version.

Other types of airplanes are used as AWACS aircraft. The U. S. Navy flies the Grumman E-2 Hawkeye on Airborne Early Warning (AEW) missions from its aircraft carriers. The Russians converted the Ilyushin Il-76 airliner into an AWACS airplane. Israel has its own AWACS system, without the big rotodome, in the Gulfstream G-550 air­plane. The Royal Australian Air Force uses the Wedgetail, an AEW aircraft based on the Boeing 737.

biplane is an airplane with two sets of wings, one above the other. The biplane was developed from the box kite, which was invented by an Australian named Lawrence Hargrave in 1893.

Before the days of powered flight, aviation pioneers, such as Otto Lilienthal in Germany and Octave Chanute in the United States, flew biplane hang gliders. They experimented with how to control an aircraft carrying a human pilot with no engine. The first controlled powered flight, in 1903, was made by a biplane, the Wright brothers’ Flyer. The first powered flight in Europe was also made by a biplane, this time flown by a Brazilian pilot called Alberto Santos – Dumont, in 1906.

One Wing or Two?

In the early years of airplane develop­ment, engineers were not sure which design flew best: the monoplane (with one wing) or the biplane (with two wings). They tried adding more wings to see if this worked. In 1908 the first tri­plane (with three wings) took to the air, but triplanes never became widespread.

The biplane appeared to fly more steadily than the monoplane. Engineers believed this was because two wings gave more lift than one wing. In fact, a disadvantage of the biplane is that the two sets of wings tend to interfere with one another, thereby reducing lift and increasing drag.

Overall, early wing designs were not very efficient. There was little difference between the performance of monoplanes and biplanes in the days of low-power engines and slow speeds. Biplanes were stronger than monoplanes, however— their wings were braced by taut wires and wooden struts. This was important in the early days, before 1930, when most airplanes were flimsy structures of wood and cloth. The wings were an air­plane’s weakest point, and it was not unusual for the wings to fall off when a plane was diving or turning, usually with fatal consequences for the pilot.

To improve lift and reduce drag, biplane designers tried “staggering” the wings. This usually meant fixing the upper wing slightly in front of the lower wing, but there were also biplanes that had the lower wing set farther forward. Staggering worked quite well, and biplanes proved as useful as monoplanes for some time.

William Boeing, founder of the aero­space giant that bears his name, was
born in 1881 in Detroit, Michigan. His father was a wealthy mining engineer of German origin. After graduating in engineering from Yale University, William Boeing made his own fortune trading forestlands in Washington State. Airplanes, however, were his main inter­est. In 1910 he went to Los Angeles to watch planes gather at the first air meet to be held in the United States, but to his disappointment failed to persuade any of the pilots there to take him for a flight.

Boeing found a partner in a U. S. Navy engineer named George C. Westervelt. The two young men were convinced that they could build air­planes, and they began work on a biplane. Having taken to the air for the

first time as a passenger in a Curtiss biplane, William Boeing learned to fly in 1915, taking lessons from pioneer pilot Glenn L. Martin.

The first Boeing airplane was the Model 1, also known as the B&W. It was

a biplane with floats for landing on water, and it flew for the first time on June 29, 1916. Its top speed was only 75 miles per hour (121 kilometers per hour).

Westervelt went his own way, and Boeing set up a business, Pacific Aero Products, to build the B&W. In April 1917, Pacific Aero Products became the Boeing Airplane Company, based in Seattle, Washington. Boeing sold air­planes to the government—the United States was now engaged in World War I.

Back in 1981, Columbia had been the first Space Shuttle to go into space. The tragic accident on February 1, 2003, that destroyed the spacecraft and claimed the lives of its crew took place at the end of its twenty-eighth mission.

While Columbia was still in space, engineers studied video images of its launch. The images showed a piece of insulating foam falling off the external fuel tank and hitting Columbia’s left wing 82 seconds after liftoff. It was not a serious concern at the time. When Columbia began its return to Earth from space, however, it began to heat up. As Columbia hurtled deeper into the atmos­phere, ground controllers noticed that sensors in the left wing were showing unusually high temperatures. Then, the
sensors failed. Sensors in the landing gear inside the left wing showed tire pressures rising, and then these sensors failed, too. A few seconds later, radio contact with the crew was lost.

Although Columbia was still nearly 39 miles (62.8 kilometers) above the ground, traveling at more than 12,500 miles per hour (more than 20,000 kilo­meters per hour), eyewitnesses on the ground could see it was breaking up. They saw flashes and streaks of light

О The last crew of the Space Shuttle Columbia were (from left to right): Mission Specialist David Brown, Commander Rick Husband, Mission Specialist Laurel Clark, Mission Specialist Kalpana Chawla, Mission Specialist Michael Anderson,

Pilot William McCool, and Payload Specialist Ilan Ramon.

coming from its bright trail in the sky and knew this was not what a reentering Space Shuttle usually looked like.

Debris fell over a huge area. Pieces of wreckage were collected from 2,000 locations across the United States.

Investigation

A team of independent experts investi­gated the cause of the accident. They carried out experiments to see if a piece of foam falling from the external tank could have damaged the spacecraft’s wing. It seemed unlikely because the leading edge of the wing is much harder and stronger than the foam. The wing was made of a material called reinforced carbon-carbon. Surprisingly, experi­ments showed that a piece of foam could indeed punch a hole straight through the wing’s leading edge.

If the foam that fell off the fuel tank just after Columbia’s launch made a hole in the left wing, hot gas would blast through the hole to inside the wing during reentry. It would burn and melt its way through the wing’s internal structure. This explains why sensors in the left wing showed rising temperatures and then failed. The weakened wing would have broken up, quickly followed by the rest of the vehicle.

All Space Shuttles were grounded for more than 2 years while the problems were investigated and resolved. Space Shuttles are now inspected in space dur­ing each mission to check for damage that might prove dangerous during the spacecraft’s return to Earth.

Challenger’s wreckage was buried in an unused missile silo at Cape Canaveral. Columbia’s wreckage is stored in the Vehicle Assembly Building at the Kennedy Space Center. Parts of it are used for research. When Columbia broke up, pieces of all shapes, sizes, and mate­rials flew through the atmosphere at speeds they were not designed for. Scientists and engineers are interested in precisely what happened to them, what temperatures they experienced, and how they were affected. The lessons learned by studying these pieces may help in the design of future high-speed aircraft.

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Date of birth: April 15, 1452.

Place of birth: Anchiano, Italy.

Died: May 2, 1519.

Major contributions: Artist; engineer; developer of early designs for parachutes and helicopters.

eonardo da Vinci was born during the Italian Renaissance, a period marked by great interest in the arts and literature as well as the begin­nings of modern science. The ideal man of learning at the time was one who could understand many different fields. Leonardo (today, he is often referred to by his first name alone) embodied that ideal.

Paintings such as the Last Supper and the Mona Lisa cemented Leonardo’s reputation as a brilliant artist with a subtle understanding of human emotion. His studies of human anatomy reveal a painstaking attention to detail and knowledge far in advance of his time. The mechanical devices that Leonardo built and sketched prove that he was an accomplished engineer with a powerful imagination. Some of these devices show a brilliant mind wrestling with the the principles and problems of flight.

Leonardo received standard school­ing for his time. When he displayed obvious artistic talent, he was appren­ticed to an artist’s workshop in Florence, Italy, to learn art. From age fifteen to his late twenties, he studied art, drawing, and engineering. In 1481, Leonardo

began to work on his own. Soon after, he began filling notebooks with his observations of the world and his thoughts about them.

Leonardo lived much of his adult life away from Florence, working for the duke of Milan and the king of France. He was renowned for his skill as a painter, sculptor, and designer of machines, including weapons.

Early in his life, Leonardo had devel­oped an interest in designing a machine that could fly. To prepare for this possi­bility, he carefully studied the properties of air and the anatomy and flight of birds. These studies led Leonardo to propose several remarkable ideas. In 1500, for example, he suggested that the weight of a person could be carried by a tentlike structure made of cloth. Leonardo sketched such a cloth para­chute in the shape of a pyramid. Near the drawing, he predicted that by using it a person could “throw himself down from any great height without sustain­ing any injury.” Modern adventurers have built such a device, following Leonardo’s design, and have managed to use it successfully.

That same year, Leonardo sketched an even more remarkable device: a heli­copter with a central screw that could turn the propeller. His notes explained how springs could be used to turn the screw, but here Leonardo ran up against the limitations of technology: at the time there was no mechanical force pow­erful enough to provide the needed lift.

Leonardo spent much time trying to figure out how to create an ornithopter, a device that achieved flight by having a person flap its wings. The action was not always carried out with arms-in some versions, Leonardo intended the power to be provided by the flier’s legs. Unfortunately, humans do not have enough muscle to lift their weight into the air in this way. Also, Leonardo did not quite understand how bird’s wings provide both thrust and lift. His designs were doomed to failure. According to legend, he tested one of his designs using a servant-the story says that the servant crashed and broke his leg. Leonardo’s last drawing of a flying

machine abandoned the ornithopter for a fixed-wing glider. He described how the pilot could shift weight in the craft to change its direction.

Leonardo’s notebooks hold about 150 drawings of flying machines. His vision­ary ideas did not influence the history of aviation, however. His notebooks were forgotten until the 1800s, and by that time some early advances in flight had already been made.

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SEE ALSO:

• Glider • Helicopter • Lift and

Drag • Ornithopter • Parachute

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n ejection seat is a complex piece of equipment with a sim­ple aim: to save pilots’ lives by propelling them out of airplanes that are damaged and unable to land safely. Ejection seats are used in warfare-they are not found on civilian aircraft. They have saved hundreds of pilots’ lives.

How It Works

Aircraft crew members sit in ejection seats during normal flight. The seat has
the basic parts of bucket, back, and headrest as well as some special features. Ejecting at supersonic speed subjects the human body to forces in excess of 20g (twenty times the force of normal gravi­ty). The seat, therefore, is designed to protect the body from g-force and from debris. Once clear of the airplane, a parachute opens.

A combat pilot may have to eject because of engine failure or a collision with another aircraft, or after being hit by missile attack. The process has to be quick. To activate the ejection seat, the pilot can do one of two things: pull a handle attached to the seat or pull down a small curtain that will protect the pilot’s face. The pilot’s action begins a sequence that removes the canopy from the cockpit and sends the seat (which is mounted on rails) shooting up and away from the airplane. It is catapulted clear by a ballistic cartridge working with a rocket unit fitted underneath the seat. Once clear of the air-

О In 2003, Captain Christopher Stricklin ejected from a Thunderbird aircraft less than a second before it hit the ground at an air show in Idaho. The pilot had miscalculated a maneu­ver and knew he could not save the aircraft. He ejected after guiding the jet away from the crowd of more than 60,000 people and was not himself injured.

plane, a small drogue parachute opens to slow the seat before the main descent parachute deploys. The pilot can discard the seat before landing.

The modern fighter pilot has a comput­erized control system. Not only does it fly the airplane, but it also detects a target and fires missiles long before the pilot can even see the target. A display panel shows the pilot a virtual picture of the combat zone as the airplane “locks on” its guided weapons-all this while flying at twice the speed of sound.

With so much equipment and weaponry to carry, fighter aircraft have

become steadily larger. The F-4 Phantom used in the Vietnam War weighed four times as much as a World War II Mustang, and a modern F-15 is almost ten times heavier. There are a few excep­tions, such as the lighter AV8 Harrier Jump Jet and the F-117 Nighthawk.

Modern fighters include the F-14 Tomcat, a shipboard interceptor, with variable-geometry wings, or swing wings. The aircraft flies well at low speed, with its wings extended, but also has good performance at supersonic speed with its wings swept back. One of the most successful U. S. fighters is the F-16 Fighting Falcon. Sold to a number of countries, this agile, single-seat air­craft is capable of flying at 1,320 miles per hour (2,124 kilometers per hour).

Current frontline fighters, such as the F-15 Eagle, fly at Mach 2.5 and climb to

100,0 feet (30,480 meters). They are armed with cannons and air-to-air missiles and can carry an additional

16,0 pounds (7,264 kilograms) of weapons externally. Like many modern airplanes, the F-15 has had a long life. Design studies began in the late 1960s, the first prototype flew in 1972, and the aircraft saw its first combat in the Gulf War of 1990. The F-15’s replacement is the multi-role F-35 Lightning II Joint Strike Fighter, which made its inaugural flight in 2006.

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SEE ALSO:

• Aircraft, Military • Bomber

• Control System • Radar • World

War I • World War II

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