Category FLIGHT and M ОТІOIM

In some countries air traffic control is run by the military. In others, civilian air traffic controllers may work for the gov­ernment or for a privatized company. The Federal Aviation Administration (FAA) is the national agency responsible for civil­ian aircraft and air safety in the United States. It sets the rules for all commercial aircraft operators and private pilots fly­ing in U. S. airspace. The FAA also certi­fies pilots. Air traffic controllers must undergo a training course before they, too, are certified by the FAA.

The FAA runs a network of twenty Air Route Traffic Control Centers (ARTCCs) across the continental United States. Most centers are named for major cities—although located outside them—

and they are identified by a code. Center code names are prefixed by the letter K, followed by a three-letter identifying tab, such as KZBW (Boston) and KZAU (Chicago). There are also centers outside the continental United States in Alaska, Guam, and Puerto Rico. The Air Traffic Control System Command Center over­sees the national picture.

National airspace is the air above a nation’s territory, which may include stretches of ocean. Each ARTCC has responsibility for its own area, and some have responsibility for airspace over international areas of ocean, allocated to them by the ICAO. (Much of the airspace above oceans, however, is not controlled by any one nation.)

Each center takes charge of an air­plane from the time the pilot enters its area until the airplane is handed off to the next control center. Near the end of its flight, usually at a distance of 5 miles (8 kilometers) from the airfield, the plane is handed over to an air traffic controller at the airport terminal for landing.

The first aircraft used in warfare was the tethered balloon. It was used for obser­vation, rising above battlefields so observers could get a view of the action below. The balloon was later developed into the airship, and airships were also used by the military for observation.

The first gasoline-powered military airplanes were known as scouts because reconnaissance (flying on missions to gather information) was their chief pur­pose. Other uses were soon found for military airplanes. They dropped bombs, fired at enemy ships, and shot down enemy aircraft. Special airplanes, most­ly biplanes, were built for these tasks.

The first air combat took place dur­ing World War I (1914-1918). Pilots shot at one another with pistols, shot­guns, and machine guns. The next step was to attach a machine gun, which the pilot aimed at an enemy, to the airplane itself. By 1915 fighter planes had been developed with synchronized machine guns that fired bullets between the whirling propeller blades. Celebrated fighter pilots, known as aces, created successful air fighting tactics.

By the end of World War I, there were two main types of military air­plane. Fighters flew at around 125 miles per hour (200 kilometers per hour) at heights of up to 22,000 feet (6,700 meters). Larger, heavier bombers flew more slowly, around 100 miles per hour (160 kilometers per hour), but they could fly for up to 8 hours.

In the 1930s the agile biplane was replaced by the much faster monoplane. This new kind of aircraft had an enclosed cockpit, a streamlined metal body, and a high-performance engine. Fighter planes such as the German Messerschmitt Bf 109 and Curtiss P-40 had a top speed of over 350 miles per hour (563 kilometers per hour). Bombers, such as Boeing’s B-17, were slower at around 280 miles per hour (450 kilo­meters per hour), but they could fly for 2,000 miles (3,220 kilometers). The bombers carried 6,000 pounds (2,725 kilograms) of bombs that could be dropped accurately on city targets.

O (From left) An A-10 Thunderbolt II, F-86 Sabre, P-38 Lightning and P-51 Mustang fly in a flight formation during an air show at Langley Air Force Base, Virginia, on May 21, 2004. The formation displayed four generations of U. S. Air Force fighters.

THE VERACRUZ INCIDENT

The first military operation involving U. S. airplanes was during the Veracruz Incident, a dispute between the United States and Mexico that began in April 1914. Five Curtiss flying boats were carried into the Mexican port of Veracruz by U. S. naval ships. The aircraft flew mis­sions to search for mines in the harbor. On May 6, 1914, the airplane flown by Lieutenant Patrick N. L. Bellinger (1885-1962) was shot at from the ground by Mexican forces.

This was the first time that a U. S. military plane was hit by enemy fire while on active service. Bellinger survived and went on to become a distinguished admiral.

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As air travel has grown more popular, some airports have grown so large that
they resemble small cities. A very large international airport, or primary hub, usually covers between 1.5 and 5 square miles (3.9 and 13 square kilometers). Some occupy much more space. The air­port that occupies the most land is King Khalid International Airport in Riyadh, Saudi Arabia, which covers more than 80 square miles (207 square kilometers).

Most airports are located away from the centers of cities, partly because they need so much space for their runways, but also because of noise. Aircraft are noisy, and flights over residential dis­tricts or at night may be limited. Good highways, together with rapid transit systems, are essential for a large airport to work efficiently. These road and rail networks move passengers and freight to and from airports, but they are also necessary to transport the thousands of workers who keep airports running.

Founded in 1958, the National Aero­nautics and Space Administration

The huge Saturn V rocket that took Apollo 11 into space weighed 5.8 million pounds (2.6 million kilograms). It stood 363 feet (110.6 meters) high. The rocket had three stages. The first and second stage took the spacecraft up into orbit around Earth, while the third stage sent the spacecraft traveling toward the Moon. The five first-stage engines burned liquid oxygen and kerosene. The five second – stage engines burned liquid oxygen and nitrogen. The third – stage engine burned liquid oxy­gen. In the first 2.5 minutes of flight, Saturn V burned about

528,0 gallons (about 2 million liters) of fuel.

The Apollo 11 spacecraft weighed about 103,000 pounds (46,762 kilograms) at launch. The cone-shaped command module Columbia was 12 feet (3.7 meters) high. The cylinder­shaped service module stood 22 feet (6.7 meters) high. The lunar module, the Eagle, was 21 feet (6.4 meters) high. It weighed 29,983 pounds (13,612 kilo­grams). The lunar module had two engines: one for descent and one for leaving the Moon.

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Avionics equipment has to keep working in all conditions. An aircraft could be sitting on the ground on a hot day at more than 104°F (40°C), and a few min­utes later it could be flying through air as cold as -76°F (-60°C). Turbulent (rough) air and hard landings can shake up a plane considerably. Lightning can strike and shock a plane with millions of volts. Avionics have to work reliably through all of this.

If part of an avionics system does break down, however, it is designed to fail in a way that does not put an air­craft in danger. The most important sys­tems have at least one backup. If the main or primary system fails, the back­up takes over. There is often more than one backup, so if the first backup fails, yet another backup can take over. This is called “failsafe operation.”

The Space Shuttle has five flight computers. Four of the computers work together, and they constantly check each other. If one computer fails, the other three vote it out of the system and ignore it so that it cannot command the spacecraft to do anything dangerous. If a second computer fails, the other two can still land the Space Shuttle safely. If all four computers fail, the fifth com­puter takes over. If all five computers were programmed with the same soft­ware, they could all crash because of the same fault in their programming. The fifth computer, therefore, is programmed with different software.

ernoulli’s Principle is a law of nature discovered by Daniel Bernoulli in the early 1700s. It states that when a fluid (either gas or liquid) speeds up, its pressure falls.

Bernoulli noticed that fluids flowing through a tube speed up when they pass through a narrower part of the tube. A tube of this kind, with a narrow section, is called a venturi. Bernoulli wondered where the extra speed came from. He found that it is caused by a fall in pressure inside the narrowest part of the venturi.

There is an easy experiment that shows Bernoulli’s Principle in action.

Blowing air between two regular sheets of paper might be expected to force them apart. Instead, according to Bernoulli’s Principle, the fast flow of air lowers the air pressure between the sheets of paper, and the higher pressure outside pushes them together. Blowing between two sheets of paper actually sucks them together.

Danger at Sea

Bernoulli’s Principle also explains a problem that affects ships. When two ships sail together, side by side, there is a danger that they will be sucked toward each other and collide. The shape of the two ships’ hulls creates a gap between them that narrows in the middle. This gap is the same shape as a venturi.

Water speeds up as it squeezes through the gap between the two ships. According to Bernoulli’s Principle, the water pressure here falls. The higher water pressure outside the ships pushes them together. Ships sailing close together, therefore, have to be steered carefully to keep them apart.

he Boeing Company is the world’s largest manufacturer of airplanes and a leader in the manufacture of space vehicles, satellites, and defense equipment. Boeing’s headquarters are in Chicago, Illinois.

Industry Leader

The two main divisions of the company are Boeing Commercial Airplanes, based at Renton, Washington, and Boeing Integrated Defense Systems in St. Louis, Missouri. A key sector is the research
group, Phantom Works, which designs advanced aircraft. Phantom Works prod­ucts include the Bird of Prey stealth aircraft and the X-45 unmanned Combat Air Vehicle.

Boeing has grown into one of the world’s most powerful industrial giants. It has absorbed other airplane manufac­turers over the years, such as Stearman (1939), Vertol (1960), Rockwell (1996), and McDonnell Douglas (1997). Boeing has for many years been the biggest supplier of aircraft to the world’s commercial airlines. In the 2000s, how­ever, the company has been challenged as market leader by its European rival Airbus. Boeing ranks second in defense equipment, behind Lockheed Martin.

The morning of January 28, 1986, was colder than any previous Space Shuttle launch day. Challenger was due to take off for its tenth space mission. Icicles hung from the tower next to the space­craft. There was concern that ice might fall off and damage the vehicle during launch. A team had worked all night to remove as much ice as possible. The launch was delayed to give more time for the remaining ice to melt.

Engineers were also worried about rubber rings in the two solid rocket boosters. The boosters are made in sections that stand on top of each other. The joints between them are sealed with putty and rubber rings. Engineers were concerned that the cold weather could make the rubber too stiff to seal the joints properly. If a seal failed, hot gases from inside the rocket could escape. After some lengthy discussions between engineers and managers about

the weather and the rubber rings in the boosters, it was decided to go ahead with the launch.

Things started to go wrong just moments after liftoff. Close-up photo­graphs of the spacecraft would later reveal puffs of smoke spurting out of the side of one of the solid rocket boosters. This was clear evidence that the seal in one of the joints had failed, as the engi­neers had feared.

The amount of mechanical equipment in an aircraft can be reduced by using a control system called fly-by-wire. Mechanical links between flight controls and hydraulics are replaced with electric wires. When the pilot moves the con­trols, electric impulses flow along the

wires to the airplane’s flight computers, which activate the hydraulic system.

An even more advanced control sys­tem is called fly-by-light. The control signals sent out from the cockpit to the various parts of the plane are not elec­trical impulses. Instead, they are pulses of light that travel along cables made of thin strands of glass called optical fibers. Glass normally breaks when someone tries to bend it, but optical fibers are so thin that they can even be tied in knots without breaking.

Another control system being devel­oped is power-by-wire. A fly-by-wire system replaces mechanical links with electric wires, but the aircraft still needs

SPACE SYSTEMS

Manned spacecraft have used automatic control systems and fly-by-wire since manned spaceflight began in the 1960s. Early manned spacecraft were controlled automatically. They also had a manual fly-by-wire control system for use as a backup and for maneuvering operations in orbit. Today, the Space Shuttle’s auto­matic control system can fly the craft from launch to landing. The only part of a mission that must be flown manually by the crew is when the Space Shuttle docks with another spacecraft. The Space Shuttle’s fly-by-wire control system fires rocket thrusters in space and moves the control surfaces in its wings and tail when it is flying in the atmosphere.

a hydraulic system to power the actua­tors. A power-by-wire control system uses electric actuators that are powered by small electric motors. The goal is to produce an all-electric airplane without any hydraulics. By getting rid of the hydraulic equipment, an aircraft could be made much lighter. Making an aircraft lighter means that it would burn less fuel.

SEE ALSO:

• Aileron and Rudder • Avionics

• Cockpit • Tail

All of these triumphs impressed Edward Elliott, the president of Purdue Univer­sity in Indiana. He set up a fund to carry out aeronautical research and bought Earhart a new plane. It was a Lockheed Electra, equipped with many instru­ments. Earhart was determined to use the plane for a last flight around the world. Pilots Wiley Post and Howard

Hughes had done such a flight, but they had taken a northerly route that did not travel around Earth at its widest point. Earhart set out to do just that. “When I finish this job,” she said, “I mean to give up long-distance ‘stunt’ flying.”

Earhart and navigator Fred Noonan took off from Miami, Florida, on June 1, 1937, heading southeast. They flew to Brazil and then headed northeast to Senegal in Africa. They crossed the African continent, skirted the southern coast of Arabia, and flew over India before turning southeast to reach Indonesia. They arrived at Lae, New Guinea, on June 28, having made sever­al stops and flown nearly 20,000 miles (32,180 kilometers).

The next leg, from Lae to Howland Island in the central Pacific Ocean, was the longest single section of the trip, more than 2,200 miles (3,540 kilo­meters). Some technical difficulties arose before takeoff, but Noonan and Earhart departed on July 1. As they neared Howland Island early on July 2, Earhart asked by radio for a weather update; there was a storm near the island. A few more messages were received, including one that mentioned low fuel levels. The last radio transmission came at 8:45 a. m. The plane never arrived at Howland’s airfield. Earhart and Noonan were never heard from again.

The U. S. Navy quickly began to search the waters near Howland Island for some sign of the plane and the two fliers, but searchers found absolutely nothing. The commonly accepted view is

INITIAL FAILURE

Earhart first tried the round-the – world trip on March 17, 1937. She, Noonan, and two other fliers took off from Oakland, California, for Hawaii that day. The first leg of the trip went fine, but mechanical problems devel­oped in Hawaii. While the plane was being fixed, the other two fliers dropped out. Since Noonan was more familiar with a transatlantic route, the decision was made to change directions. That led to the final takeoff from Miami.

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that the plane ran out of gas and went down in the ocean, killing Earhart and Noonan. Some people have said that Earhart was spying on Japanese facili­ties in the Pacific on behalf of the U. S. government. These people suggest that she and Noonan were captured by the Japanese after landing. No strong evidence has ever been found for this.

Whatever her fate, Amelia Earhart was an inspirational figure. Although she first gained fame as only a passen­ger, she proved to be an able and daring pilot. Her skill, bravery, and winning personality made her one of early avia­tion’s most beloved figures.

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SEE ALSO:

• Lindbergh, Charles • Pilot ______________ /