History of Planes
The Basics of How Planes Fly
Advanced Aspects of Airplane Flight
HISTORY OF PLANES ^TOP
Flight has astonished humans ever since we noticed the flight of birds. And considering how long we have existed, flight is relatively new to us. When Wilbur and Orville Wright mastered the secret of flight in 1903, they did not try to imitate the flight of birds but they built a machine for flying. That is exactly what an airplane is, a flying machine. Many attempts to fly were made before the famed Wright Brothers, but all were unsuccessful. The coming of the airplane brought worldwide amazement. Even though the Wright Brother's first flight only lasted a few seconds, it gave people hope that one day major flight could be achieved. In fact, the Wright Brother's first flight was shorter in distance than a modern 747 Jumbo Jet is long. The first flight only reached an altitude of about 50 feet. From that point on, everyone pursued the technology of flight. Many people began to try and make "flying machines" of their own, with some successful and some not. The military was one of the first organizations to ask the secret of flight from the Wright Brothers, realising the Airplane could be a usefull recon or survaillance tool. Later they realised the terrible destructive power the airplane had--the ability to drop bombs.
By the beginning of World War I in 1912 all the major countries had flight, including the Air Forces of the U.S., Great Britain, Germany, France, and Russia. During this time, airplanes had a dual or tri-wing design on most occasions, called Biplanes and Triplanes. (Refer to the HOW PLANES FLY section to learn more about Biplanes and Triplanes). Ever since the WWI era large planes have been used for civilian transport. Since WWI, planes have changed dramatically, though.
From the time of WWI to the beginning of WWII, airplanes were switched from a biplane or triplane design to a monoplane design, or a plane with one wing. That design has stayed with virtually all airplanes ever since.
Between WWII and the Vietnam War, planes started to get much more sophisticated. During that period jet engines were developed. Before WWII in the 1940's, all planes were driven by piston engined propellers. The jet engine changed flight forever. Planes became faster, they flew higher, but they also became more expensive and complicated. The first plane reached the speed of sound (Mach 1) in 1947. That plane was the X-1, developed by the Bell company and flown by Chuck Yeager. Today the fastest converntional airplanes can reach Mach 3.5, or three and a half times the speed of sound. Some experimental airplanes can travel hypersonically, or above Mach 5. Airplanes today are very fast and very safe. Despite many of the airplane crashes reported in the news, traveling by plane is the safest way to travel. Only one in several million planes crash.
By the Gulf War in 1990 military aircraft were far more sophisticated than ever thought possible. Although the aircraft used in the Gulf War were very sophisticated, with their high-tech navigational and radar systems, they were also very deadly to the people that they used their weapons against.
As time passes airplanes will continue to grow more sophisticated and technologically advanced, though the military planes may also grow more deadly with stronger weapons. Soon we may see more planes that will fly in the hypersonic regime. By the year 2050 experts say that the only aircraft that will be piloted by humans will be civilian airliners. All military planes and transport planes will be remote-controlled by computers on the ground.
THE BASICS OF HOW PLANES FLY ^TOP
HOW PLANES STAY IN THE AIR ^TOP
Airplanes fly due to one simple aspect of our atmosphere; air pressure. An aerofoil, otherwise known as the wing, is shaped in a special way that keeps air pressure away from the top of the wing while keeping a lot of air pressure under the wing. Air traveling over the curved upper surface of the wing increases its velocity. Acording to Bernoulli, a scientist of several hundred years back who had nothing to do with the invention of the airplane, increased velocity means lower air pressure. When the top of the wing has little air pressure, and when there is a lot of air pressure traveling under the wing, the wing lifts the plane into the sky. If the plane loses speed, and air will not travel fast enough past the wing, the wing will stop producing lift. When the plane does not have enough lift to stay in the air, it will stall. When a plane stalls, it literally falls out of the sky until it gains enough speed to fly straight again. This never happens in civilian planes that you might fly in yourself, but if a fighter jet is flying at too steep of an angle, it might stall. The fighter jet would stall because air would stop flowing over the wing to create lift. There are a few different types of wing design. The most common is swept wings. Swept wings are exactly what they sound like, in that they are swept at an acute angle to the plane's fuselage. Swept wings are common on large civilian planes like 747s. Swept wings let air travel by them faster than a conventional wing because of its sleek shape.
Conventional wings are straight and perpendicular to the planes fuselage. They create a lot of lift though they also create a lot of drag, slowing the plane down.
The most common form of wing on fighter jets is the Delta wing. Delta wings are attached to the plane like triangles, and allow air to flow past them smoother than other wings. This lets the plane go faster.
DIFFERENT TYPES OF PLANES ^TOP
Besides the different wing types listed above, there are a few other different airplane designs. The oldest is the Biplane. The Biplane is a plane with two wings stacked on top of each other. This design creates a lot of lift, but it also creates a lot of drag. (Further details are available in the next section). Another design that is about as old as the Biplane is the Triplane. The Triplane is just like the Biplane, though the triplane has three sets of wings instead of two. Biplanes and Triplanes were used during the WWI era and are no longer made. Another old design is the "flying boat" Flying boats were large planes that had boat hulls instead of wheels. Flying boats land on water, taxi to a dock, and pick up people or goods that need to be transported. Back between WWI and WWII flying boats were made very large and were only used as transports.
Another interesting design, which was used around WWII, was the dual-tail airplane. These planes had two fuselages and two tail sections, with a space in between the two tail sections or the two fuselages. This design is very rare now, and sometimes the dual-tail and flying boat designs were combined to make a double-tailed flying boat.
LIFT, WEIGHT, THRUST, AND DRAG ^TOP
The four main aspects of a plane's flight are lift, weight, thrust, and drag.
Lift is what keeps the plane in the air. Wings produce the lift that is necessary to stay in flight, as described before. Lift is the opposite of weight.
Weight is what prevents the plane from getting off the ground. If a plane is too heavy for the amount of thrust and lift it produces, it will not take off. The heavier the plane, the slower it goes. Civilian planes are designed to fly at high speeds, even with a full load of people. Military planes must be very careful about the loads of weapons it carries. Some military planes are strong and can carry heavy loads of weapons; but lighter, weaker planes cannot carry such heavy loads for their thrust and lift will not be great enough to overcome the weight.
Thrust is the motion that propels the plane through the air. Without enough thrust, the plane will not fly. Thrust is produced by the engine, and thrust is the opposite of drag.
Drag is the air that is flowing against a plane that keeps a plane from moving forward. If a plane has many protruding objects on its surface, the objects will disrupt airflow over the plane's surface. This creates drag. Biplanes and triplanes create a lot of lift, but they have too much drag. Their large wings are very bulky and not aerodynamic. Planes today are very sleek and aerodynamic with a minimal amount of objects sticking out. The more aerodynamic a plane, the less drag it produces; resulting in faster and smoother flight.
Wings are the most essential part of the airplane. Its shape, an AEROFOIL, creates lift as described before by creating high pressure below the wing and low pressure above the wing. The wings house most of the plane's control surfaces, like flaps or the others below. A wing has several aspects to it. First of all the length of a wing, a straight line from the formost tip to the end, is called the chord line. A wing is curved, though, to slow down air above it. The line that goes straight through the center of the wing, following the curve, is called the camber line. The front of the wing is called the leading edge and the back of the wing is called the trailing edge. The camber line and chord line are what make up a wing's a ablilty to create lift. If a wing's camber line is greater than the chord line, as in most cases, lift will be high but so will drag. This means that the more a wing is bent (or the greater the camber), the more lift and drag it will produce. These aspects get even further complicated and we will stop here.
LEADING EDGE FLAPS: On the front end of the wing there are flaps. Flaps are hinged areas of the wing that are lowered to provide extra lift. As the leading edge flaps are lowered, the wing's camber line is extended resulting in added lift. This is useful for takeoffs and landings or at slow speeds.
TRAILING EDGE FLAPS: There are also flaps on the rear of the wing. As they are lowered, drag is increased as well as camber and the plane slows down. This is useful to slow the plane down for landings.
To keep the plane from wobbling back and forth in the air, the plane has a vertical stabilizer and two horizontal stabilizers. These stabilizers make up the airplane's tail section. The vertical stabilizer is the wing-like structure jutting out from the top of the plane's fuselage.This keeps the plane's tail from swinging side to side. The plane's horizontal stabilizers are the small wings that jutt out from the sides of the fuselage in the back of the plane. These keep the plane from rolling wildly or tilting up and down, and in most cases the plane's horizontal stabilizers are used to store the elevators or aileorons.
Elevators are small hinged parts of the wing or horizontal stabilizer. When moved up or down, the elevators move the plane up or down. Elevators cause the first main aspect of a plane's movement; pitch. The elevators are controlled by moving the joystick in the cockpit forward and back. Forward makes the plane dive, backwards makes the plane climb.
A plane's aileorons are also hinged parts of the horizontal stabilizer or the wing like elevators, and sometimes aileorons and elevators are combined as one. These are called Elevons. Aileorons or elevons are used to roll the plane. When the two aileorons are moved in opposite directions, they cause the plane to roll, or spin. This is the second main aspect of a plane's movement; roll. The aileorons are controlled by moving the joystick in the cockpit left and right. This is not turning from side to side. Rudders are used for turning a plane side to side.
Rudders, which are used for turning a plane left to right (side to side), are a hinged area of the vertical stabilizer. These cause the third and final aspect of a plane's motion; yaw. Rudders are controlled by foot pedals in the cockpit where the pilot sits.
Airbrakes are used to slow the plane down while in flight. Airbrakes are usually small flap-like panels that come out of the plane to create drag and slow the plane down.
THE POWER PLANT ^TOP
The power plant, or engines, are used to provide thrust to move the plane. Most modern planes today use jet engines which are very strong and powerful. To power a jet engine, it must have air. The front of a jet engine is the air intake, where the air is sucked in. On fighters the air intakes are large openings found below or to the sides of the fuselage. On larger planes the jet intakes and the entire engine are found hanging under the wings, below the vertical stabilizer, or to the sides of the fuselage on the tail of the plane. At the other end of the jet engine is the nozzle. The nozzle expels the thrust that pushes the plane through the air. On large planes the engine nozzle is on the end of the engine, but on fighter planes the engine nozzle is in the very back of the plane. The engine's power output is controlled by a small lever in the cockpit called a throttle. When the throttle is pushed back, the engine produces less thrust. When the throttle is moved forward, the engine produces more thrust. A jet engine is a very complicated piece of machinery and its explanations are far beyond the simplicity of this report. To put it simply though, an engine compresses air, ignites it, and expels it to create thrust using Newton's law where every action must have an equal and opposite reaction (that's simple rocket science!).
LANDING GEAR ^TOP
To stay on the ground and to support the plane, the plane needs landing gear. Landing gear are the wheels that hang below the plane. During flight, the landing gear is kept in an internal bay under the plane so that they don't create drag and slow the plane down. During takeoffs and landings and while the plane is on the ground, the landing gear is lowered out of the internal bays.
In order for the pilot to control the plane, an aircraft has a complex set of gears, wires, hydraulics, and sometimes computers to control the control surfaces. In most planes, when the pilot moves the rudder pedals or joystick, a chain of events occurs, with hydraulics and whatnot, to control what is needed. In newer planes, though, there is something called fly-by-wire. This kind of system is controlled by computers. You may have a joystick for your computer. It is small, at your side, and the computer uses it to tell what you are doing. This is exactly what happens on a real plane with fly-by wire controls; a pilot moves a small stick on his right that tells the computer what to move, and the computer moves it, without all the complex gears and mechanics running throughout the plane.
ADVANCED ASPECTS OF AIRPLANE FLIGHT ^TOP
There are several military planes today that are stealth. There are others that are being developed, too. Stealth is when radar cannot see a plane. This is very useful in the military since the planes can fly into enemy territory without being detected. To be stealth, a plane uses radar absorbing paint, and it uses a special design. Only a few planes use this special design, such as the F-117, B-2, or F-22. These planes are designed in such a way that the radar waves are deflected, absorbed, or sent around the plane instead of back to the radar.
FORWARD-SWEPT WINGS ^TOP
An experimental U.S. plane that uses forward-swept wings is the X-29. Forward-swept wings decrease drag, which means the plane can fly faster. Planes that use forward-swept wings are still being tested with. Forward-swept wings may decrease drag, but they are not practical. They tend to be structurally less stable than conventional wings, which means heavy loads like weapons, fuel, or engines could not be carried on them.
VECTORABLE THRUST ^TOP
Vectorable thrust means that a plane can change the position of its engine nozzles to direct the thrust into different directions. If a plane can vector its thrust, it is very maneuverable. Few planes today can vector their thrust in different directions to turn themselves, and some other planes can vector their thrust up and down so it can take off vertically without a runway, like the Harrier. The planes that can make vertical take-offs are not new to the flight world, but the planes that can use vectorable thrust to turn are very new.
G - FORCES ^TOP
The forces of lift and weight described above are measured in terms of `G,' where 1g equals the force of the Earth's gravity. For an aircraft to fly, its wings must generate more than 1g of lift to overcome the 1g of weight gravity puts on all objects. Once airborne, the wings must maintain at least 1g of lift or the aircraft succumbs to gravity. When a plane turns, it creates its own center of increased gravity, so it "pulls Gs". The sharper and faster a turn, the more g-forces there are. When a civilian plane turns, it only pulls between 1 and 2 Gs. When a fighter plane makes a sharp and fast turn or pulls up (climbs) fast, it may pull up to 8 or 9 Gs. That means if the pilot weighs 200 pounds and he pulls a 9 G turn, he will weigh 1800 pounds. When a pilot experiences this, he may black out. The g-forces cause all the blood in his body to fall to his legs, which means there is no blood in his head. If a pilot blacks out for a very long time he may become unconscious. If as plane pulls negative Gs, which is when a plane dives or does an inverted turn, the pilot will redout. This is when all the blood in his body rushes to his head.