FIXED WING AIRCRAFT FACTS - HOW AIRCRAFT CREATE LIFT AND FLY
(Parts of an aircraft or airplane that allow it to take flight)
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FIXED WING AIRCRAFT FACTS AND HOW AIRCRAFT FLY
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 the aircraft generates lift. Though technically all aircraft wings flex, and some aircraft have wings that can tilt, sweep back, or fold, 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 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 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. 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.
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.
ach wing is a structure attached to 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 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.
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 anything by Rutan.
An aircraft flies due to the aerodynamic reactions that happen when air passes over the wing.
If a cross-section of an aircraft wing is viewed, the top of the wing can be seen to be curved, while the bottom of the wing is less curved or straight. This shape, called an airfoil or aerofoil, creates lift when a wing travels through the air.
Lift is created as an airstream passes by something which deflects it downward. The force created by this deflection of the air creates an equal and opposite force upward 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" explanation, 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.
It has recently been dubbed the "Equal transit-time fallacy." There is no requirement that divided parcels of air rejoin again, and in fact they do not do so. Such an explanation would predict that an aircraft could not fly inverted, which is not the case. The explanation also fails to account for aerofoils which are fully symmetrical yet still develop significant lift. Any textbook claiming to be a serious work on the topic will never promote the Equal Transit-time fallacy.
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 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 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
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 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 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.
Designing and Constructing 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.
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.
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