Category FLIGHT and M ОТІOIM

A number of biplane types were still in military service when World War II began in 1939. Most were soon with­drawn, although there were exceptions. The last frontline biplane with the U. S.

Navy was the Curtiss SBC Helldiver, a dive bomber that was still flying at the time of the Japanese attack on Pearl Harbor in 1941. The Curtiss Seagull scout plane served with the U. S. Navy from 1933 until the end of World War II. This aircraft had the unusual distinction of outlasting at least two later designs intended to replace it. So did the Fairey Swordfish torpedo plane, which flew from British aircraft carriers during World War II naval battles, despite hav­ing a top speed of only 138 miles per hour (222 kilometers per hour).

Many wartime pilots learned to fly in a two-seater biplane. The De Havilland Tiger Moth, first flown in 1931, was still in use in the early twenty-first century.

Another very successful trainer biplane was the Boeing/Stearman Model 75, which became the standard World War II trainer for the U. S. military.

О Vintage biplanes are used today for recreation and for aerobatics demonstrations. These airplanes are flying while tied together.

Lloyd Stearman started building biplanes in 1927, and the Stearman Company became part of Boeing in 1939. Being slow and safe to handle, the Boeing/Stearman Model 75 was ideal for pilots who were learning basic flying skills. Ten thousand Model 75s, known unofficially as Kaydets, were built before 1945. After the war, many Model 75s were sold to the air forces of other nations, while others ended up as agri­cultural airplanes.

William Boeing still dreamed of a new, fast airliner. This dream came true in

1933 with the Boeing 247. The 247 is widely regarded as the first “modern” airliner. It was a low-wing, twin-engine monoplane, made completely of metal and with retractable landing gear. The 247 was flown by a pilot and copilot, while a flight attendant catered to the ten passengers. Two Pratt & Whitney Wasp radial engines gave the 247 a speed of 200 miles per hour (320 kilome­ters per hour), and it could fly for 745 miles (1,200 kilometers) before refueling.

By 1934, Boeing was operating an airline and manufacturing aircraft, which was prohibited by a new law (the

1934 Air Mail Act). The federal govern­ment ordered that Boeing be divided, and the company was split into United Aircraft, United Air Lines, and the Boeing Airplane Company.

О Workers install fixtures to the tail fuselage of a B-17 bomber in 1942.

In 1939 Boeing released the elegant 314 Clipper flying boat. Designed for passenger routes over the oceans, the Clipper had a range of 3,500 miles (5,630 kilometers). The same year, how­ever, World War II halted commercial flying between the United States and Europe and brought an end to the flying boat era.

Aircraft manufacturers had begun to design new warplanes some years before World War II began in Europe in September 1939. In May 1934 the U. S. Army issued a specification for a new bomber, and Boeing came up with the four-engine 299, which was first flown on July 28, 1935. Three weeks later, the 299 flew nonstop for 2,100 miles (3,380 kilometers) at an average speed of 252 miles per hour (406 kilometers per hour). Boeing’s delight at this success turned to gloom when, in October, the bomber crashed on takeoff. New prototypes were quickly in the air, however; the Y1B-17, first flown on December 2, 1936, became the B-17 Flying Fortress.

The cockpit is the compartment in an aircraft’s nose where pilots sit to fly the aircraft. It contains the flight controls, engine controls, and instruments that show information about the aircraft. An airliner’s cockpit is also known as the flight deck.

Flight and Engine Controls

Most aircraft have two seats in the cock­pit, side by side. Each seat has its own set of flight controls, so the aircraft can be flown from either one. There is one set of engine controls between the seats.

There are two main flight controls: the control yoke and a pair of foot ped­als. The yoke looks like a car’s steering wheel with the top cut off. Turning the yoke makes a plane bank to one side. Pushing on the yoke makes an airplane’s nose tip down so the plane loses height.

Pulling the yoke back tips a plane’s nose up and makes the plane climb. The pedals control the rudder that is in the tail of an airplane.

Pushing the left pedal turns the plane’s nose to the left. Pushing the right pedal turns the nose to the right.

The main engine control is called the throttle, or power

lever. If the aircraft has more than one engine, there is a power lever for each engine. Moving the power levers changes the amount of fuel supplied to each engine. Giving an engine more fuel makes it run faster and pro­duce more power.

Airbus airliners are unusual because they have no control yokes for steering the plane.

Instead, they are steered by small hand controllers, called side-stick controllers, that look like com­puter game joysticks. There is one on each side of the cockpit.

The finished prototype rolled out for its test flight program in 1949. The Comet looked futuristic compared with the pro­peller planes being used at the time. It was a sleek metal airplane with slightly swept-back wings. Its four turbojet engines fitted neatly into the root of the wing (where the wing joins the fuse­lage), giving the airplane an elegant look. If the Comet flew as fast as

planned, it would surely be a success. Piloted by wartime fighter ace John Cunningham, hired as a De Havilland test pilot, the Comet made its first flight in July 1949. The new jetliner made headlines the world over. Sleek and fast, the Comet seemed to embody the jet age.

After its first flight in 1949, the Comet continued test flights, including long-distance trips from the United Kingdom to Italy, Egypt, South Africa, and Singapore. All went well. On May 2, 1952, the British Overseas Airways Corporation (BOAC) began the world’s first jet passenger service, from London to Johannesburg in South Africa. The

Comet 1 was not a very big airplane: it carried about forty passengers and a crew of four (pilot, copilot, engineer, and navigator). Its attraction was its speed: 150 miles per hour (241 kilometers per hour) faster than the propeller-driven planes then flying the world’s air routes. It also was quieter than the propeller planes it was intended to replace, and it took less time to service between flights. The future appeared bright.

nergy is the ability to do work. In science and engineering, work is done when a force moves an object. The work done to move an air­craft requires energy.

Forms of Energy

There are many different forms of ener­gy. Everything that moves has energy; the energy of movement is called kinet­ic energy. The more massive something is and the faster it moves, the more kinetic energy it has. Something can also have energy because of its position or condition. This is potential energy, or stored energy.

There are different types of potential energy. If a ball is taken up to the top of a hill, work has to be done to move the ball upward against gravity. The ball
thereby acquires gravitational potential energy. The energy stored in a squashed spring is known as elastic potential energy. The type of energy stored in chemicals, including aircraft fuel and rocket fuel, is chemical potential energy.

Kinetic energy and potential energy are both types of mechanical energy. Other forms of energy include heat ener­gy, electrical energy, magnetic energy, light energy, nuclear energy, and sound energy. Heat energy is also called ther­mal energy, and light energy from the Sun is called solar energy.

Energy cannot be created or destroyed. It can only be changed from one form to another. If a ball taken up to the top of a hill is allowed to roll down the hill, its potential energy changes to kinetic energy. If a squashed spring is released, its potential energy changes to kinetic energy. Burning a fuel changes

О This diagram shows how potential energy can turn to kinetic energy when a ball is pushed up a hill and then rolled downward. The ball stores potential energy acquired on the upward journey that is released as kinetic energy on the way down.

WHERE DOES A GLIDER’S ENERGY COME FROM?

Gliders have no engines, so they need to get their energy from another source. Gliders are towed into the air by a cable pulled by a plane or by a winch on the ground. When the cable is released, the glider has a certain amount of energy-part – ly kinetic energy because of its movement and partly gravitational potential energy because of its height. When a glider dives toward the ground, some of its potential energy changes into kinetic energy, and it speeds up.

Energy can be changed in the opposite direction as well. When a pilot makes a glider climb, the aircraft’s kinetic energy changes back into potential energy. In still air, a pilot cannot make a glider climb back up to the same height that it started from, because it loses energy to the surrounding air. The only way a glider pilot can avoid sinking slowly to the ground is to find a new supply of energy. When a glider flies into rising air, it gains potential gravitational energy as the air carries it upward. Then it can convert this into kinetic energy all over again.

its chemical potential energy to heat energy and light energy.

If all the different forms of energy are added up, the total is always the same. When a ball rolls down a hill, the sum of its potential energy and kinetic energy at every instant during its roll stays the same. This is also called the law of conservation of energy. An air­craft is more complicated than a rolling ball, but it follows the same law.

The first airplane to take off from water was the Hydravion, piloted by Henri Fabre of France in 1910. The first sea­plane competition, held in Monaco in 1912, attracted seven entries.

A pioneer of seaplanes in United States was Glenn Curtiss. As early as 1910, he and some friends tried to fit cloth-covered wooden pontoons to an airplane Curtiss had designed, the Aerodrome No. 3 June Bug. The first attempt to land was unsuccessful, but in June 1910, Glenn Curtiss landed on Lake Keuka in a biplane attached to a canoe! Unfortunately, the canoe plane was unable to take off again. Curtiss went on to build floatplanes and flying boats, such as his Flying Fish of 1912. This flying boat set a precedent for later design by having a hydrodynamic hull shape that made take­off from water easier.

О The Dornier Do-X was a luxury passenger flying boat of the 1930s. First built in 1929, it was the largest heavier-than-air aircraft of its day.

The first airplane built by Boeing, the Model 1 (1916), was a floatplane. Many early airplanes were fitted with floats because a watery landing was not likely to smash up the plane’s flimsy structure. Also, airplanes of this era were often forced to land due to bad weather or engine failure or when pilots got lost. There were few airfields, but there were plenty of rivers, lakes, and ocean.

In 1919 a U. S. Navy Curtiss NC-4 fly­ing boat made the first crossing of the Atlantic Ocean. It traveled in stages from May 16 to 31. The NC-4 was a four-engine biplane with a speed of 85 miles per hour (137 kilometers per hour). Three Curtiss flying boats set off from Newfoundland, Canada, but only one reached Plymouth, England, after a jour­ney of 3,925 miles (6,315 kilometers). In 1924 two Douglas World Cruisers flew

JET FIGHTERS

The first and only flying boat fighter plane with jet engines was the Saunders Roe SR/A1. First flown in 1947, this airplane was a twin – engine fighter, intended to operate from water without the need for runways. The SR/A1 managed 512 miles per hour (824 kilometers per hour) but was not agile in air combat because of the extra weight of its boat-shaped hull. It never went into production. A later experiment with a jet fighter on water skis, Convair’s Sea Dart (1953), was similarly disap­pointing. The Sea Dart had extend­able skis for takeoff and landing.

In 1954, it became the first seaplane to fly supersonic, in a shallow dive. The Sea Dart did not meet expectations, however, and the pro­gram was ended in 1956.

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around the world. These airplanes had floats and wheels, and their record­breaking flight took 363 hours.

The International Space Station (ISS) began to take shape in Earth orbit in 1998. It has been permanently manned by teams of visiting astronauts since November 2000. Still under construc­tion, it is due to be completed by the year 2010. Progress on the ISS was held up by the grounding of the Space Shuttles after the loss of Columbia in 2003. With Shuttle flights resumed in 2006, however, the remaining modules of the ISS should be in place on sched­ule. They include the European module Columbus along with the Japanese mod­ule Kibo. Russia has plans to launch a third module, the Multi-purpose Laboratory Module (MLM) in 2009, using its Proton rocket. The ISS presently can accommodate a crew of three, and it cir­cles the Earth at an average speed of 17,165 miles per hour (27,618 kilometers per hour). When fully assembled, the space station will be a fully functional space laboratory above Earth, crewed by international scientists.

The space station is an example of international cooperation. Five national space agencies are involved in its construction and use: NASA (United States), the Canadian Space Agency, the European Space Agency, the Russian Federal Space Agency, and the Japanese Aerospace Exploration Agency. The Brazilian and Italian space agencies also are taking part.

Like many other space projects, the ISS represents a compromise. In the 1980s, the United States, Europe, and the Soviet Union (now Russia) all had plans to establish their own space stations, but high cost forced them to pool resources. Even so, the ISS is likely to cost more than $100 billion by the time it is completed.

Future ISS-linked developments include the European Automated Transfer Vehicle (ATV) and a similar spacecraft being built by Japan. There will be new passenger-carrying shuttle vehicles, such as the Space X Dragon (2009) and the Russian Kliper (2012). Europe’s first ATV is designed to be launched by an Ariane 5 rocket and to dock automatically with the space sta­tion to deliver fuel and other supplies. At the end of its stay, the ATV will be loaded with trash and sent on a deliber­ately destructive reentry into Earth’s atmosphere, where it will burn up and disintegrate. Six more ATVs will be launched, at eighteen-month intervals, to visit the space station.

Radio signals from the satellites travel at the speed of light. It takes less than one-

tenth of a second (only 65 to 85 milli­seconds) for a radio signal to travel from a GPS satellite to a GPS receiver on Earth. A GPS receiver picks up the signals and measures the time that they took to travel from the satellites. It then multiplies these times by the speed of light to calculate the distance to each satellite. Knowing how far it is from the satellites enables the receiver to pinpoint its own location.

The satellites transmit on two differ­ent radio frequencies, L1 and L2. The signals may slow down a little as they travel through the atmosphere, and this can cause an error in calculating a posi­tion. Because of this, the simplest GPS receivers are accurate to within about 30 to 60 feet (about 9 to 18 meters). More advanced receivers can correct errors caused by the atmosphere, and so they are more accurate. These receivers can calculate their position to within about 15 to 30 feet (about 5 to 10 meters).

A helicopter has four main controls: throttle, cyclic control, foot controls (to control torque), and collective. The pilot uses the throttle to control the speed of the engine. By moving the cyclic control lever or control column, the pilot can alter the tilt of the rotor blades. For example, pushing the stick forward tilts the rotor forward, and the helicopter flies forward.

The pilot uses foot pedals to turn the helicopter by altering the pitch of the tail rotor blades, which swings the tail around. The collective pitch stick or lever is used to control the angle, or pitch, of the rotor blades. This action affects the amount of lift generated and thus makes the helicopter fly up or down, or causes it to hover.

In 1930, scientists at Gottingen University, Germany, tried to figure out how a bumblebee could actually fly. When they analyzed their studies and
calculations, these experts concluded that—from a scientific point of view—the bumblebee should not actually be capa­ble of flight. It was not the right shape. More recently, scientists have used robot insects to study the mechanics of insect flight. They created large-scale model insect wings, stuck them in a tank of thick oil, and used a motor to beat the wings up and down. Flapping slowly in the oil, the model wings acted much as tiny wings do when they are flapping very fast in the air.

Such experiments have shown that an insect can use three kinds of wing movements to perform amazing maneu­vers. When a fly is trying to dodge a predator, such as a human trying to swat it, the insect can change direction in thirty-thousandths of a second.

Three Maneuvers

The first movement, unique to insects, is known as delayed stall, which means that the insect wing sweeps forward at a high angle. The insect wing cuts through the air at a steeper angle than an air­plane wing. An airplane at this stage would stall, losing lift and increasing drag, and it would most likely crash. In an insect, however, the steep angle pro­duces a vortex (like a whirlpool in the air) above the wing, cre­ating extra lift.

The second insect technique is rotation­al circulation. Toward the end of its stroke,

О A swarm of locusts surrounds a farmer in the Philippines. Locusts can destroy entire crops of rice and sugar.

О The mosquito belongs to the same insect family as a housefly. Instead of rear wings, mosquitoes and flies have two halteres to help them fly.

the insect wing rotates backward. This produces backspin, which in turn pro­duces extra lift.

The third insect trick is wake capture, which gains extra lift by recapturing energy lost in the wake (the disturbed air left behind the flying insect). As the wing moves through the air, it creates turbulent air behind it. By rotating the wing before starting the return stroke, the insect captures some of this air, and the energy within it, for extra lift.

Acrobatic insects, such as the hover – fly, make use of rotational circulation and wake capture but do not often use delayed stall. Butterflies do not appear
to use any of these three techniques very much. They fly more like birds, gliding or flapping their wings in a less complex fashion. Flies have a pair of special balance organs instead of rear wings. Called halteres, they are shaped some­what like tiny clubs. These organs help give flies their remarkable flying skills.