Category FLIGHT and M ОТІOIM

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 ______________ /

In 1940, Hurricane and Spitfire fighters of the British Royal Air Force fought one of the most important air battles of the war, the Battle of Britain. Fighter pilots battled hundreds of German bombers and fighters, including Bf 109s. In this battle, British pilots had the benefit of a new invention: radar. Radar gave early warning of incoming enemy aircraft, so ground controllers could direct fighters to intercept them.

Fighter pilots had to adapt their tac­tics as air battles became faster and more deadly. In the 1930s, pilots flew in rigid formation, often in groups of three airplanes. By 1940, German pilots found it was better to fly in pairs or groups of four, and their example was followed by many Allied fighter pilots. Allied pilots in Europe also used tricks to provoke combat. “Rodeo” meant flying over enemy territory to entice enemy fighters. “Circus” was sending in a decoy force of bombers to draw enemy fighters into the air, then pouncing on them from above. Fighter aircraft that flew in support of ground attacks were called fighter-bombers. They shot troop con­voys, tanks, and trains and bombed fuel depots, highways, and airfields.

Designers strove to produce faster fighters with longer range and better armament. Outstanding aircraft of World War II were the German Bf 109 and Fw 190; the Japanese A6M2 Zero; the British Spitfire and Tempest; and the American P-47 Thunderbolt and P-51 Mustang. These were all single-engine planes. There were also twin-engine, long-range fighters, such as the P-38 Lightning that was used widely in the Pacific, and twin-engine night fighters, such as the P-61 Black Widow, the first U. S. fighter to be equipped with radar.

In the Pacific, the main fighter battles of World War II were between carrier – based airplanes. The U. S. Navy met the challenge of the Japanese Zero with the

F6F Hellcat and the F4U Corsair. The Corsair was said by many Japanese fly­ers to be the best U. S. combat aircraft they faced.

Developing a new airliner or military jet can take ten years or more, and its serv­ice life may be thirty or forty years. Often, engineers have to choose between existing technologies and new ones. They also must predict what demand will be like in twenty or fifty years.

Aviation industry experts foresee a huge market for new airplanes in Asia, especially in India and China. These nations may well become leading air­plane manufacturers. At present, the world’s airline business is dominated by the manufacturers Airbus and Boeing.

The European aerospace group Airbus is backing its A380 “super jumbo” airliner, which can seat 555 peo­ple. U. S. giant Boeing hopes that its hi – tech 7E7/787 Dreamliner will be more attractive to airlines, although this plane seats only half as many passengers. The A380 will be able to land only at large airports, whereas the smaller Dreamliner will fly to more destinations. Boeing also plans to keep building the reliable 747 (first flown in 1969).

Like all airplanes, a glider must maintain a flow of air over its wings to sustain lift. Lacking a motor, a glider cannot fly level for long and still maintain that airflow. In calm air, the pilot must keep the nose of the air­craft angled slightly toward the ground-as the glider flies in a gentle dive, gaining speed, the airflow around the wings pro­vides lift. Having built up speed, it can rise up before descending again. A glider can soar to great heights if the pilot can locate rising air currents, known as thermals or updrafts. Carried up by such currents, the plane spirals upward, just as a vulture or buzzard soars on widespread wings and can fly for many hours in this way.

A glider has a high glide ratio, which determines the distance it can travel forward compared to its height loss. If a particular aircraft has a glide ratio of 40:1, it can glide 40 miles (64 kilo­meters) forward for every mile of altitude it loses. Once this glider has reached an altitude of around 3,000 feet (915 meters), the pilot has a good chance of flying around 120,000 feet (36,600 meters) in distance. If the pilot can gain greater height by soaring in a rising air current, the length of the flight will be

much longer. Some gliders have a glide ratio of 70:1. The Space Shuttle, by con­trast, has a glide ratio of only 4:1.

In 1936, a helicopter flown in Germany became the forerunner of the modern helicopter. The Focke-Achgelis FW-61

THE CONVERTIPLANE

A variation on the helicopter princi­ple is the convertiplane. This concept dates back to the autogiro of the 1920s. A convertiplane is capable of vertical takeoff and landing (VTOL) using rotary-wing flight, but then switches to normal layout for for­ward flight at speeds matching those of conventional airplanes. The idea was demonstrated in 1957 by the British Rotodyne, a helicopter-like airliner with wings and engines for normal flight. An example of a modern convertiplane is the tilt-wing CV-22 Osprey.

had two rotors mounted on outriggers (metal frames) on either side of the fuselage. This aircraft could take off and land vertically, it could hover, and it could fly at 76 miles per hour (122 kilo­meters per hour) during flights of over an hour in duration.

Igor Sikorsky, who had left Russia in 1919 and had become a U. S. citizen, was still busy working on ideas for heli­copters. In 1940, his new helicopter, the VS-300, made its first flight without being tethered to the ground. It was a

BELL HELICOPTERS

The Bell Aircraft Corporation was founded by American Lawrence Bell (1894-1956). The company made its name with airplanes, such as the record-breaking X-1, but became equally famous for helicopters, start­ing with the Bell Model 47 (1945). This small, bubble-nosed whirlybird stayed in production until 1973 and was used by armed forces all over the world. Its original piston engine gave the Model 47 a top speed of 105 miles per hour (169 kilometers per hour).

small, single-seat machine with a single rotor. The VS-300 was followed in 1942 by the XR-4, the first military helicopter to be put into production. A small number of XR-4s were flown by Allied forces during World War II (1939-1945). In 1943, an XR-4 became the first heli­copter to take off from a ship.

Date of birth: December 24, 1905.

Place of birth: Houston, Texas.

Died: April 5, 1976.

Major contributions: Set speed records for flying across the United States and around the world; founded Hughes Aircraft Company, a major producer of airplanes and satellites; built the world’s largest fly­ing boat; expanded TransWorld Airlines (TWA) into a major airline.

Awards: Harmon Trophy (twice); Collier Trophy; Octave Chanute Award; Congressional Gold Medal; member of Aviation Hall of Fame.

oward Hughes had a remarkable career that including setting world speed records as a pilot, creating one of the giant companies of the aerospace industry, and building a major airline. In the later decades of his
life, he lived almost completely isolated from other people.

Making Movies

Hughes was the son of a Texas oilman. The family became wealthy when Hughes’s father invented a drill bit that could dig deep through rock for oil. The company that made the drill bit—the Hughes Tool Company—generated huge profits that funded other business ven­tures. In 1924, at age eighteen, Howard Hughes gained control of his family for­tune when his father died.

Two years later, Hughes moved to Hollywood in Los Angeles, California, to follow his passion for movies. He began producing movies and took over direct­ing his favorite, Hell’s Angels. The movie portrayed air combat during World War I. Hughes bought nearly ninety vintage planes (forming the largest private air fleet in the world as a result) and filmed hours of aerial com­bat scenes. Released in 1930, the movie was a box-office success, but it came nowhere near earning back its stunning cost, $3.8 million (which would be ten times that amount today). From the late 1940s to the late 1950s, he owned a major motion pic­ture studio called RKO Pictures.

О After making the movie Hell’s Angels, Howard Hughes went on to make Sky Devils, a comedy about World War I aviation. Hughes reused many of the airplanes from his large fleet. He is shown here on the Sky Devils set in 1931.