Airplanes
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Wikipedia-Article "Airplanes"
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Fixed-wing aircraft is a term used to refer to what are more commonly known as airplanes in North American English and aeroplanes in Commonwealth English. An airplane is a heavier-than-air aircraft where movement of the wings in relation to the aircraft is not used to generate lift. All aircraft wings flex, and some aircraft have wings that can tilt, sweep back or fold, but if none of these movements are used to generate lift, the wing is considered to be a "fixed-wing."
Fixed-wing aircraft include a large range of craft designed for many purposes from small trainers and recreational airplanes to large airliners and military cargo aircraft. Some aircraft use fixed wings to provide lift only part of the time and may or may not be referred to as fixed-wing. Airplanes have no ability to drive on the ground for extended time periods.
The term also embraces a minority of aircraft with folding wings that are intended to fold when on the ground. This is usually in order to to ease stowage or facilitate transport on, for example, a vehicle trailer or the powered lift connecting the hangar deck of an aircraft carrier to its flight deck. It also embraces an even smaller number of aircraft, such as the General Dynamics F-111 Aardvark, Grumman F-14 Tomcat and the Panavia Tornado, which can vary the sweep angle of their wings during flight. In the early days of their development, these were termed "variable geometry" aircraft. When the wings of these aircraft are fully swept, usually for high speed cruise, the trailing edges of their wings abut the leading edges of their tailplanes, giving an impression of a single delta wing if viewed from above or below. There are also rare examples of aircraft which can vary the angle of incidence of their wings in flight, such the F-8 Crusader, which are also considered to be "fixed-wing".
Two characteristics common to all the airplanes are the necessity of constant air flow over the wings for lifting of the aircraft, and an open area free of obstacles where they can, with sufficient space, take off or land. The majority of airplanes, however, also need an airport with enough infrastructure to receive adequate maintenance, restocking, refueling and for the loading and unloading of crew, cargo and/or passengers, when these are present in sufficient amounts. While the vast majority of airplanes land and take off on land, some are capable of take off and landing on ice, snow and calm water.
The airplane is currently the fastest method of civil and military transport on the planet. Commercial jet airplanes can reach up to 875 km/h, and cover one fourth of the terrestrial sphere in a matter of hours, and single-engine airplanes are easily capable of reaching 175 km/h or more at cruise speed. Supersonic airplanes, currently only military, research and a few private aircraft, can reach speeds that sometime surpass the speed of the sound.
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Conventional airplanes
Conventional airplanes -- from small planes such as the Bumble Bee II and Cessna 140 to a gigantic Antonov 225 -- consist of a longitudinal fuselage, one or more wings to provide the majority of lift, a tailplane for stability, and a one or more vertical surfaces at the tail for stability.
Fixed parts
- Each wing is a single wing structure integrated into the fuselage of the aircraft. Sometimes, the half of a wing on either side of the fuselage is referred to as a wing, e.g. left wing and right wing. Most airplanes are monoplanes having one wing structure for providing lift. Biplanes (two wings) or triplanes (three wings) were popular in the past, and some are still made for special purposes like aerobatics. Fuel is often stored in tanks in the wing.
- In smaller aircraft, fuel is sometimes stored in the fuselage (or main body).
- An engine (or engines): Also known as powerplants, engines serve to propel the aircraft on the ground and the air. Airplanes use a wide variety of engines, including turbine, reciprocating, and radial engines. The engines are usually located under or on the wings or attached to the fuselage. A few aircraft have engines attached to the vertical or horizontal stabilizer.
- The tailplane is a small wing that provides positive or negative lift to stabilize the aircraft in flight. Most often it is configured to provide negative lift. It may be a fixed horizontal stabilizer with a movable elevator or a stabilator that rotates on a shaft to change the angle of incidence.
- The vertical stabilizer is a small vertical wing that is usually attached to the rear of the fuselage. Some aircraft have two vertical stabilizers attached to the horizontal stabilizer or boom structures. A rudder is attached to the vertical stabilizer.
Mobile parts
- Ailerons are located on the wing of the aircraft. They always act at the same time, but in inverse directions, so that the airplane can be turned along its longitudinal axis. This movement is called roll. Because roll changes the direction of lift of the wings, it is the primary method of changing the direction of travel.
- The elevators are located on the horizontal stabilizer to control the rotation around the lateral axis called pitch. The elevator and horizontal stabilizer may be combined into a stabilator.
- On delta-wing aircraft the ailerons and elevators are combined together to perform the same actions and are called elevons.
- The rudder is located on the vertical stabilizer and controls movement around the vertical axis called yaw.
- The landing gear allow the airplane to take off and land. They usually retract during flight to reduce drag; however, on smaller aircraft the gear are often fixed parts. Some aircraft are equipped with special landing gear, such as pontoons or skis, to allow them to land on various surfaces.
- The flaps change the profile of the wing of the airplane, maximizing lift and control of the speed of the aircraft in air, particularly in operations of low speed - especially important in landing and take-off.
Other common parts of aircraft include trim tabs, air brakes, spoilers, winglets and canards.
Unconventional aircraft have been built in a variety of forms. For example: lifting body, canard, V-tail and flying wing.
Flight (lift)
- Main article: Lift (force)
An airplane flies due to the aerodynamic reactions that happen when air passes at high speed over the wing.
If you look at a cross-section of an airplane wing, you will see that the top of the wing is curved, while the bottom of the wing is straight -- or at least curved less than the top. This shape -- called an "airfoil" -- is what creates lift when a wing travels through the air.
When an airplane wing travels through the air, it forces the air to pass both on top of and underneath the wing. Because the top of the wing is curved more than the bottom, the length of the wing is larger on the top portion than on the bottom. To compensate for the longer distance to be traveled, the air flow moves faster on top of the wing than beneath the wing. This significantly diminishes the pressure of air above the wing, The wing is "pulled" up into this low-pressure area above the wing, creating the necessary lift for flight.
Airplanes need sufficient speed in order to generate the low-pressure area above the wing that creates lift. To reach these high speeds, an airplane needs to cover a certain distance on the ground before reaching the speed needed for take-off. Larger and heavier aircraft will generally require a longer runway to reach the necessary speed for the take-off, given the larger amount of energy needed.
Types of fixed-wing aircraft
Propeller aircraft
Propeller airplanes make use of combustion engines, that in turn, turn a propeller, which creates the necessary force for the movement of the aircraft. They are relatively quiet, but they fly at lower speeds, and have lower load capacity compared to similar sized jet powered aircraft. However, they are significantly cheaper and much more economic than jets, and is the generally the best option for people who need to use an airplane in a smaller company to transport a few passengers and/or small amounts of cargo. They are also the aircraft of choice for pilots who wish to own their own aircraft.
Jet aircraft
- Main article: Jet aircraft
Jet airplanes make use of turbines for the creation of the necessary force for the movement of the aircraft. Jet airplanes generally have turbine engines that are much more powerful than their propeller driven cousins. As consequence, they have greater weight capacity and faster flight speeds than propeller driven aircraft. One drawback, however is the great amount of sound created for a turbine; this makes jet airplanes a source of noise pollution. They also require much larger amounts of maintenance compared to their propeller driven cousins.
Huge widebodies ("wide bodies"), such as the Airbus A340 and Boeing 777, can carry hundreds of passengers and several tons of cargo, and are able to travel for distances of up to 13 thousand kilometers - a little more than one quarter of the circumference of the Earth.
Jet airplanes possess high cruising speeds (700 to 900 km/h) and relatively high speeds for take-off and landing (150 to 250 km/h). Due to the high speeds needed for takeoff and landing, the jet airplane makes great use of flaps for the control of lift and speed, and has engine reversers (to direct the airflow frontward) on most engines for slowing down the aircraft upon landing to supplement the brakes.
Super sonic aircraft
Super sonic airplanes, such as military fighters and bombers, the Concorde and others, make use of special turbines (often utilizing afterburners), that generate the huge amounts of power for flight faster than the speed of the sound. Moreover, the design of the supersonic airplane has substantial differences from the design of sub-sonic airplanes, in order to make the transition to supersonic flight smoother and to make supersonic flight more efficient.
Flight at super-sonic speed creates much more sound pollution than flight at sub-sonic speeds, due to the phenomena of sonic booms. This limits super-sonic flights to areas of minimal population density or open ocean. When they approach an area of heavier population density, super-sonic airplanes are obliged to fly at sub-sonic speed.
Due to the high costs, limited areas of use and low demand there are no longer any super-sonic aircraft in use by any major airline, and the last Concorde flight was November 26, 2003. It appears that supersonic aircraft will remain in use almost exclusively by militaries around the world for the foreseeable future.
Rocket-powered aircraft
- Main article: Rocket-powered aircraft
Experimental rocket powered aircraft were developed by the Germans as early as World War II, although they were never mass produced by any power during that war. The first fixed wing aircraft to break the sound barrier was the rocket powered Bell X-1. The later North American X-15 was another important rocket plane, that broke many speed and altitude records and laid much of the groundwork for later aircraft and spacecraft design. Rocket airplanes are not in common usage today, although rocket-assisted takeoffs are somewhat common for military aircraft. SpaceShipOne is the most famous current rocket airplane that is the testbed for developing a commercial sub-orbital passenger service.
Ramjet aircraft
Ramjet (and the Scramjet variant) aircraft are mostly in the experimental stage. The D-21 Tagboard was an unmanned Mach 3+ reconnaissance drone that was put into production in 1969 for spying, but due to the poor level of success and the development of better spy satellites, it was cancelled in 1971. The SR-71's Pratt & Whitney J58 engines act as ramjets at high-speeds (Mach 3.2). The last SR-71 flight was in October 1999. The Boeing X-43 is an experimental scramjet with a world speed record for a jet-powered aircraft - Mach 9.6, or nearly 7,000 mph. The X-43A set the record on Nov. 16, 2004.
History
- Main articles: Aviation history & First flying machine
The dream of flight goes back, for Man, to the days of pre-history. Many legends, beliefs and myths of antiquity involve flight, such as the legend of Icarus. Leonardo of the Vinci, among others visionary inventors, drew an airplane, in the 15th century. With the first flight made by man (Francois Pilatre de Rozier and Francois d'Arlandes) in an aircraft lighter than air, a balloon, the biggest challenge became to create other craft, capable of controlled flight.
Years of research by many eager people who dreamed of flight produced very slow, but continuous, progress. On August 28 of 1883, John J. Montgomery became the first person to make a controlled flight in a glider. Other aviators who had made similar flights at that time were Otto Lilienthal, Percy Pilcher and Octave Chanute. Sir George Cayley, the inventor of the science of aerodynamics, was building and flying models of fixed wing aircraft as early as 1803, and he built a successful passenger-carrying glider in 1853, but it is known the first practical self-powered aeroplanes were designed and constructed by Clément Ader. On October 9, 1890, Ader attempted to fly the Éole, which succeeded in taking off and flying a distance of approximately 50 meters before witnesses. In August 1892 the Avion II flew for a distance of 200 metres, and on October 14, 1897, Avion III flew a distance of more than 300 metres.
On August 28, 1903 in Hanover, the German Karl Jatho made his first flight. The Wright Brothers made their first successful test flights in December 17, 1903 and by 1904 Flyer III was capable of fully-controllable stable flight for substantial periods. Strictly, its wings were not completely fixed, as it depended for stability on a flexing mechanism named wing warping. This was soon superseded by the competitive development of ailerons, attached to an otherwise rigid wing.
In some countries today, particularly Brazil, Santos-Dumont is considered to be the "Father of Aviation", because of the official and of public character of the 14-bis flight and/or technical points such as the plane's integral landing gear and its ability to take off on open ground.
The 14 Bis, was the first to take off, fly, and land without the use of catapults, high winds, or other external assistance. Most Brazilians, and many other admirers of Alberto Santos-Dumont consider him, instead of the Wright Brothers, to be the true inventor of the airplane, although the very concept of the invention of the first flying machine has substantial ambiguity.
Wars in Europe, in particular, the First World War, served as initial tests for the use of the airplane as a weapon. First seen by generals and commanders as a "toy", the airplane proved to be a machine of war capable of causing serious casualties to enemy lines. In the first war, great aces appeared, of which the greatest was the German Red Baron. On the side of the allies, the ace with the biggest amount of downed aircraft was René Fonck, of France.
After the First World War, airplanes gained innumerable technological advances. Charles Lindbergh became the first person to cross the Atlantic Ocean in solo flight nonstop, on May 20, 1927. The first commercial flights took place between the United States and Canada, in 1919. The turbine or the jet engine was in development in the 1930's, military jet airplanes began operating in the 1940's.
Airplanes played a primary role in the Second World War, having a presence, either major or minor, in all the known major battles of the war, especially in the Attack on Pearl Harbor, the battles of the Pacific and D-Day. They were also an essential part of several of the new military strategies of the time period, such as the German Blitzkrieg or the American and Japanese Aircraft carriers.
In October of 1947, Chuck Yeager, in the Bell X-1, was the first person to exceed the speed of sound. The Boeing X-43 is an experimental scramjet with a world speed record for a jet-powered aircraft - Mach 9.6, or nearly 7,000 mph.
Airplanes, in a civil military role, continued to feed and supply Berlin in 1948, when access to railroads and roads to the city, completely surrounded by Eastern Germany, were blocked, by order of the Soviet Union.
The first commercial jet, the de Havilland Comet, was introduced in 1952, and the first successful commercial jet, the Boeing 707, is still in use 50 years later. Boeing 707 would develop into the later in Boeing 737. The Boeing 727 was another widely used passenger airplane, and the Boeing 747, was the biggest commercial airplane in the world up to 2005, when it was surpassed by the Airbus A380.
Designing and constructing an airplane
Small airplanes can be designed and constructed at home, by aviators who possess sufficient knowledge in the areas of engineering, physics and aerodynamics. Other aviators with less knowledge make their airplanes using complete kits, with pre-manufactured parts, and assemble the aircraft themselves.
While there are thousands of "amateur-built" airplanes flying around the world, they are still a small minority. Given their complexity, most airplanes are constructed by companies with the objective of producing them in quantity for customers. The design and planning process, including safety tests, can last up to four years for small turboprops, and up to 12 years for airplanes with the capacity of the A380.
During this process, the objectives and design specifications of the aircraft are established. First. the construction company uses a great number of drawings and equations, simulations, wind tunnel tests and experience to predict the behavior of the aircraft. Generally, computers are used by companies to draw, plan and do initial simulations of the airplane. Small models and mockups of all or certain parts of the airplane are then tested in wind tunnels to verify the aerodynamics of the aircraft.
When the airplane has made it through this process, the company typically constructs a limited number of these aircraft for testing on the ground. Special attention is given to the engines (or turbines) and to the wings.
After passing the above-designated process, representatives from an aviation governing agency often make a first flight. When the behavior of the aircraft does not present suspicion of imperfections, the flight-tests continue until the airplane has fulfilled all the necessary requirements. Then, the governing public agency of aviation of the country authorizes the company to begin production of the aircraft en masse.
In the United States, this agency is the Federal Aviation Administration (FAA), and in the European Union, Joint Aviation Authorities (JAA). These two are the agencies of regulation of most important aircraft of the world. In Canada, the prescribed the public agency in charge and authorizing the mass production of aircraft is the Department of Transport.
In the case of the international trade of airplanes, a license of the public agency of aviation or transports of the country where the aircraft is also to be used is necessary. For example, aircraft from Airbus need to be certified by the FAA to be flown in the United States and vice versa, aircraft of Boeing need to be approved by the JAA to be flown in the European Union.
Industrialized production
There are relatively few companies that produce airplanes on a large scale. However, the production of an airplane for one company is a process that actually involves dozens, or even hundreds, of other companies and plants, that produce the parts that go into the aircraft. For example, one company can be responsible for the production of the landing gear, while another one is responsible for the radar. The production of such parts is not limited to the same city or country; in the case of large aircraft manufacturing companies, such parts can come from all over of the world.
After being manufactured, the parts are sent to the main plant of the aircraft company, where the production line is located. The different parts are assembled with the others, eventually, producing the aircraft. In the case of large airplanes, lines of production are dedicated to the assembly of certain parts of the aircraft can exist, especially the wings and the fuselage.
When complete, an airplane goes through a set of rigorous inspection, to search for imperfections and defects, and after being approved by the inspectors, the airplane is tested by a pilot, in a flight test, in order to assure that the controls of the aircraft are in working properly. With this final test, the airplane is ready to receive the "final touchups" (internal configuration, painting, etc), and is then ready to be sent to the customer.
Safety
Statistics show that the risk of an air accident is very small. One is more likely to have an accident going to the airport in a car than have one during your flight. Many people have a fear of flying because the risk of death in an aircraft accident, if there is one, is extremely high. Furthermore, car crashes rarely feature outside local news whereas air crashes are reported internationally, making the risk seem greater.
The majority of aircraft accidents occur due to human error, that is, an error of the pilot(s) or control tower. After human error, mechanical failure is the biggest cause of air accidents, which sometimes also can involve a human component (ie: negligence of the airline in carrying out proper maintenance). Adverse weather is the third largest cause of accidents. Icing of wings, downbursts and low visibility are often major contributors to weather related crashes.
See also
