Fixed-wing aircraft
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A fixed-wing aircraft (more commonly known as an airplane in North American English or aeroplane in Commonwealth English) is a heavier-than-air craft where movement of the wings in relation to the aircraft is not used to generate lift. The term is used to distinguish from rotary-wing aircraft, where the movement of the lift surfaces relative to the aircraft generates lift.
Fixed-wing aircraft include a large range of craft from small trainers and recreational aircraft 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.
The current term also embraces aircraft with folding wings that are intended to fold when on the ground. This is usually 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 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. These aircraft are 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 in plan. 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 necessities for all aircraft are air flow over the wings for lifting of the aircraft, and an open area for landing. The majority of aircraft, however, also need an airport with the infrastructure to receive maintenance, restocking, refueling and for the loading and unloading of crew, cargo and/or passengers. While the vast majority of aircraft land and take off on land, some are capable of take off and landing on ice, snow and calm water.
The aircraft is the second fastest method of transport, after the rocket. Commercial jet aircraft can reach up to 875 km/h. Single-engined aircraft are capable of reaching 175 km/h or more at cruise speed. Supersonic aircraft (military, research and a few private aircraft) can reach speeds faster than sound. The record is currently held by the SR-71 with a speed of 3,529.56 km/h.
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Conventional aircraft
Conventional aircraft -- from small planes such as the Cessna 210 and Beech Bonanza to the gigantic Antonov 225 -- consist of a 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
- Wings - Each wing is a structure attached to the fuselage (or body) 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 aircraft 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 but may be stored in the fuselage as well.
- Powerplants - An engine (or engines), also known as powerplants, serve to propel the aircraft on the ground and in the air. Aircraft use a 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.
- Tailplane - A 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.
- Vertical Stabilizer - A vertical stabalizer 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 - Ailerons are movable surfaces on the wings of the aircraft. They always act at the same time, but in inverse directions, so that the aircraft 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. Many larger aircraft use spoilers to achieve the same effect.
- Elevators - 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.
- Elevons - On delta-wing aircraft the ailerons and elevators are combined together to perform the same actions and are called elevons.
- Rudder - The rudder is located on the vertical stabilizer and controls movement around the vertical axis called yaw.
- Landing Gear - The landing gear allow the aircraft to take off and land. They usually retract during flight to reduce drag; however, on smaller aircraft the gear may be fixed. Some aircraft are equipped with special landing gear, such as pontoons or skis, to allow them to land on water, snow or ice.
- Flaps - The flaps change the profile of the wing of the aircraft, 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 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, flying wing and famously, the designs of Rutan.
Flight (lift)
An aircraft flies due to aerodynamic reactions that happen when there is relative motion between air and a wing.
If a cross-section of a typical aircraft wing is viewed, the top of the wing can be seen to be curved downwards, while the bottom of the wing is less curved or straight, but angled to the airflow. This shape, called an airfoil or aerofoil, creates lift when it travels through the air.
Lift is created as an airstream passes by something which deflects it. The force created by this deflection of the air creates an equal and opposite force on the wing according to Newton's third law of motion. The deflection of airflow downward during the creation of lift is known as downwash.
Nearly any shape will produce lift if curved or tilted with respect to the air flow direction. However, most shapes will be very inefficient and create too much drag. One of the primary goals of wing design is to devise a shape that produces the most lift while producing the least lift-induced drag.
A false explanation for lift has been put forward in mainstream books, and even in scientific exhibitions. Known as the equal transit-time fallacy, it states that the parcels of air which are divided by an airfoil must rejoin again; because of the greater curvature (and hence longer path) of the upper surface of an aerofoil, the air going over the top must go faster in order to "catch up" with the air flowing around the bottom. Therefore, because of its higher speed the pressure of the air above the airfoil must be lower. Despite the fact that this "explanation" is probably the most common of all, it is false in that there is no requirement that divided parcels of air rejoin again, and in fact they do not do so.
Nevertherless, the deflection of the air does cause changes in the pressure above and below the wing; generally a higher pressure area forms below and a lower pressure forms above; these changes in pressure are necessary for the deflection to occur, and it is these pressure differences over the area of the wing that provides the force that holds the aircraft in the air.
Types of fixed-wing aircraft
Propeller aircraft
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Smaller and older propeller aircraft make use of reciprocating internal combustion engines that turns a propeller to create thrust. They are 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 are generally the best option for people who need 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.
Turboprop aircraft are a halfway house between propeller and jet: they use a turbine engine similar to a jet to turn propellers. These aircraft are popular with commuter and regional airlines, as they tend to be more economical on shorter journeys.
Jet aircraft
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Jet aircraft make use of turbines for the creation of thrust. These engines are much more powerful than a reciprocating engine. As a consequence, they have greater weight capacity and fly faster than propeller driven aircraft. One drawback, however, is that they are noisy; this makes jet aircraft a source of noise pollution.
The jet aircraft was developed in England and Germany in 1931. The first jet was the Heinkel He 178, which was tested at Germany's Marienehe Airfield in 1939. In 1943 the Messerschmitt Me 262, the first jet fighter aircraft, went into service in the German Luftwaffe. In the early 1950's, only a few years after the first jet was produced in large numbers, the De Havilland Comet became the world's first jet airliner, but was removed from service due to structural inadequacies discovered after numerous pressurization and depressurization cycles.
Wide-body aircraft, 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 up to 13 thousand kilometers.
Jet aircraft possess high cruising speeds (700 to 900 km/h) and high speeds for take-off and landing (150 to 250 km/h). Due to the speed needed for takeoff and landing, the jet aircraft makes use of flaps and leading edge devices for the control of lift and speed, and has engine reversers (or thrust reversers) (to direct the airflow forward) to slow down the aircraft upon landing, as well as the wheel brakes.
Supersonic Jet aircraft
Supersonic aircraft, such as military fighters and bombers, 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. The design problems for supersonic aircraft are substantially different to those for sub-sonic aircraft.
Flight at supersonic speed creates more noise than flight at subsonic speeds, due to the phenomenon of sonic booms. This limits supersonic flights to areas of low population density or open ocean. When approaching an area of heavier population density, supersonic aircraft are obliged to fly at subsonic speed.
Due to the high costs, limited areas of use and low demand there are no longer any supersonic aircraft in use by any major airline. The last Concorde flight was on 26 November, 2003. It appears that supersonic aircraft will remain in use almost exclusively by militaries around the world for the foreseeable future, though research into new civilian designs continues.
Rocket-powered aircraft
Template:Main Image:X-15 in flight-750px.jpg Image:Bell X-1A in flight.jpeg 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 aircraft are not in common usage today, although rocket-assisted takeoffs are used for some military aircraft. SpaceShipOne is the most famous current rocket aircraft, being the testbed for developing a commercial sub-orbital passenger service; another rocket plane is the XCOR EZ-Rocket.
Ramjet aircraft
Image:Lockheed SR-71 Blackbird.jpg Ramjet 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 development of better spy satellites, it was cancelled in 1971. The SR-71's Pratt & Whitney J58 engines ran 80% as ramjets at high-speeds (Mach 3.2). The last SR-71 flight was in October 2001.
Scramjet aircraft
Image:X-43A.jpg Scramjet aircraft are in the experimental stage. 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 flight speed record on 16 November, 2004.
History
Template:Main articles The dream of flight goes back to the days of pre-history. Many stories from antiquity involve flight, such as the legend of Icarus. Leonardo da Vinci drew an aircraft 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.
First attempts
Image:LeBris1868.jpg In 1853, Englishman George Cayley made the first manned glider flight. In 1856, Frenchman Jean-Marie Le Bris made the first powered flight, by having his glider "L'Albatros artificiel" pulled by a horse on a beach. On 28 August 1883, the American John J. Montgomery made 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 planes 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 are commonly credited with the invention of the aircraft, but like Alexander Graham Bell's telephone, theirs was rather the first sustainable and well documented attempt. They made their first successful test flights on December 17, 1903 and by 1904 Flyer III was capable of fully controllable, stable flight for substantial periods. Strictly speaking, the Flyer's wings were not completely fixed, as it depended for stability on a flexing mechanism named wing warping. This was later superseded by the development of ailerons, devices which performed a similar function but were attached to an otherwise rigid wing.
However, in some countries, particularly Brazil, Alberto Santos-Dumont is considered to be the "Father of Aviation". Though launched after the Wright Brothers' attempts, his 14-bis was the first to take off, fly, and land without the use of catapults, high winds, or other external assistance. Most Brazilians, as well as admirers of Santos-Dumont, consider him to be the true inventor of the aircraft, although the very concept of the invention of the first flying machine has substantial ambiguity.
Wars in Europe, in particular World War I, served as initial tests for the use of the aircraft as a weapon. First seen by generals and commanders as a "toy", the aircraft proved to be a machine of war capable of causing casualties to the enemy. In the first world war, the fighter "aces" appeared, of which the greatest was the German Manfred von Richthofen, commonly called the Red Baron. On the side of the allies, the ace with the highest number of downed aircraft was René Fonck, of France.
After the First World War, aircraft continued to advance their technology. Charles Lindbergh became the first person to cross the Atlantic Ocean in solo flight nonstop, on 20 May, 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 aircraft began operating in the 1940's.
Aircraft played a primary role in the Second World War, having a presence in all the major battles of the war, especially in the attack on Pearl Harbor, the battles of the Pacific and D-Day, as well as the Battle of Britain. They were also an essential part of several of the military strategies of the period, such as the German Blitzkrieg or the American and Japanese Aircraft carriers.
In October 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.
Aircraft 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 aircraft, and the Boeing 747, was the biggest commercial aircraft in the world up to 2005, when it was surpassed by the Airbus A380.
Designing and constructing an aircraft
Small aircraft can be designed and constructed at home. Other aviators with less knowledge make their aircraft using complete kits, with pre-manufactured parts, and assemble the aircraft themselves.
Most aircraft 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 aircraft with the capacity of the A380.
During this process, the objectives and design specifications of the aircraft are established. First the construction company uses drawings and equations, simulations, wind tunnel tests and experience to predict the behavior of the aircraft. Computers are used by companies to draw, plan and do initial simulations of the aircraft. Small models and mockups of all or certain parts of the aircraft are then tested in wind tunnels to verify the aerodynamics of the aircraft.
When the design has passed through these processes, the company constructs a limited number of these aircraft for testing on the ground. Representatives from an aviation governing agency often make a first flight. The flight tests continue until the aircraft has fulfilled all the requirements. Then, the governing public agency of aviation of the country authorizes the company to begin production of the aircraft.
In the United States, this agency is the Federal Aviation Administration (FAA), and in the European Union, Joint Aviation Authorities (JAA). In Canada, the public agency in charge and authorizing the mass production of aircraft is the Department of Transport.
In the case of the international sales of aircraft, a license from 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 few companies that produce aircraft on a large scale. However, the production of an aircraft 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.
The parts are sent to the main plant of the aircraft company, where the production line is located. In the case of large aircraft, production lines dedicated to the assembly of certain parts of the aircraft can exist, especially the wings and the fuselage.
When complete, an aircraft goes through a set of rigorous inspection, to search for imperfections and defects, and after being approved by the inspectors, the aircraft is tested by a pilot, in a flight test, in order to assure that the controls of the aircraft are working properly. With this final test, the aircraft is ready to receive the "final touchups" (internal configuration, painting, etc), and is then ready for the customer.
Safety
Template:Main Statistics show that the risk of an air accident is very small. An accident while driving to the airport in a car is more likely than an accident during the 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.
Aircraft are the second safest way to travel long distances after railway trains. The per-trip safety of aircraft is somewhat safer than cars, but over the long distances that aircraft can cover they are much safer.
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
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