Online Encyclopedia
Aircraft
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This article refers to the tool of travel. There is a separate article about the movie Airplane!. The band, Jefferson Airplane, is often referred to as "Airplane."
An aircraft is any machine capable of atmospheric flight.
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Categories and classification
Aircraft fall into two broad categories:
Heavier than air
- Heavier than air aerodynes, including autogyros, helicopters and variants, and conventional fixed-wing aircraft: aeroplanes in Commonwealth English, airplanes in North American English. Fixed-wing aircraft generally use an internal-combustion engine in the form of a piston engine with a propellor or a jet engine, sometimes with a propellor, to provide thrust that moves the craft forward through the air. The movement of air over the airfoil produces lift that causes the aircraft to fly. Exceptions are gliders which have no engines and gain their thrust, initially, from winche s or tugs and then from gravity and thermal currents. That is, in order to maintain their forward speed they must descend in relation to the air (but not necessarily in relation to the ground). Helicopters and autogyros use a spinning rotor (a rotary wing) to provide both lift and thrust. The abbreviation VTOL is applied to aircraft other than helicopters that can take off or land vertically. Similarly, STOL stands for Short Take Off and Landing.
Lighter than air
- Lighter than air aerostats: balloons and airships. Aerostats float in air in the same way that a ship floats in water, by displacing the air around the craft with a lighter gas (helium or hydrogen), or hot air. The distinction between a balloon and an airship is that an airship has some means of controlling forward motion and steering, while balloons simply drift with the wind.
See also: List of aviation, aerospace and aeronautical terms
There are several ways to classify aircraft. Below, we describe classifications by design, propulsion and usage.
Also see this List of aircraft.
Types of aircraft
By design
Examples of lighter-than-air aircraft include non-steerable balloons, such as hot air balloons and gas balloons, and airships (sometimes called dirigible balloons) such as blimps (that have non-rigid construction) and rigid airships that have a rigid frame. The most successful type of rigid airship was the Zeppelin. The best-known Zeppelin was the Hindenburg which was destroyed in a fire at Lakehurst, NJ, in 1937.
In heavier-than-air aircraft, we can discern two major ways to produce the lift: aerodynamic lift and engine lift. In the case of aerodynamic lift, the aircraft is kept in the air because of aerodynamics, usually by means of wings, or rotors, of some kind. With engine lift, the aircraft defeats gravity by use of vertical thrust, being greater than its weight.
Examples of engine lift aircraft are rockets, and so-called VTOL planes such as the Hawker Harrier.
Among aerodynamically lifted aircraft, the largest number falls in the category of fixed-wing aircraft, where horizontal airfoils produce lift, by profiting from Bernoulli's equation and, to some extent, the Coanda effect (aeroplane or airplane).
The forerunner of these type of aircraft is the kite. Kites have been built which carried a person high up in the air where observation could be made for great distances. Kites depend upon the tension between the cord which anchors it to the ground and the force of the wind currents.
In a "conventional" configuration, the lift surfaces are placed in front of a control surface or tailplane. The other configuration is the canard where small horizontal control surfaces are placed forward of the wings, near the nose of the aircraft. Canards are becoming more common as supersonic aerodynamics grows more mature and because the forward surface contributes lift during straight-and-level flight.
The number of lift surfaces varied greatly in the pre-1950 period, as biplanes (two wings) and triplanes (three wings) were numerous in the early days of aviation. Subsequently most planes are monoplanes. This is principally an improvement in structures and not aerodynamics.
Other possibilities include the delta-wing, where lift and horizontal control surfaces are often combined, and the flying wing, where there is no separate vertical control surface (e.g. the B-2).
A variable geometry ('swing-wing') has also been employed in a few examples of combat aircraft (the F-111, Panavia Tornado, F-14 Tomcat and B-1 Lancer, among others).
The lifting body configuration where the body itself produce lift has been tested. So far the only significant practical application of the lifting body was in the Space Shuttle and its test vehicles, but many aircraft generate lift from other than wings alone.
A second large category of aerodynamically lifted aircraft are the rotary-wing aircraft. Here, the lift is provided by rotating aerofoils or rotors. The best-known examples of this category are the helicopter, the autogyro and the tiltrotor aircraft (such as the V-22 Osprey). Some craft have reaction-powered rotors with gas jets at the tips but most have one or more lift rotors powered from engine-driven shafts.
A further category might encompass the wing-in-ground-effect types, for example the Russian ekranoplan also nicknamed the "Caspian Sea Monster" and hovercraft; most of the latter employing a skirt and achieving limited ground or water clearance to reduce friction and achieve speeds above those achieved by boats of similar weight.
And finally the flapping-wing ornithopter is a category of its own. These designs may have considerable potential but are not yet practical.
- Reference http://history.nasa.gov/SP-367/appenda.htm
By propulsion
Some types of aircraft, such as the balloon or glider, do not have any propulsion. Balloons drift with the wind. For gliders, takeoff takes place from a high location, or the aircraft is pulled into the air by a ground-based winch or vehicle, or towed aloft by a powered "tug" aircraft.
Most early aircraft used a piston-engine with propeller as propulsion. Although the configuration of the engine can vary (rotary, radial, inline), they all work according to the same principles.
During World War II, emphasis placed on air superiority brought about development of the first jet engines. Different types exist, such as the ramjet, pulse jet, turbojet, and the turboprop, the latter of which still uses a propeller.
Rocket planes have occasionally been experimented with. They are restricted to rather specialised niches, such as spaceflight, that require exceptionally high speed.
There are also model airplanes and even model helicopters. Many are radio controlled. They are flown at special fields
By usage
Three major uses for aircraft may be seen: recreational, military, and commercial.
Recreational pilots generally make use of single engine; easy to fly aircraft or non-complex aircraft. (e.g. Cessna High Wing design). Gliders and balloons are used almost exclusively for recreational purposes although they have been used in times of war in the past. For instance, balloons were used for observation in the American Civil War and World War I. Gliders were used to deliver troops into occupied territory during World War II and also for recreation.
Though used a handful of times for reconnaissance during the Italo-Turkish War, the first widespread use of military aircraft was in World War I, for reconnaissance and surveillance. Soon they were adapted for attacking the ground or enemy vehicles/ships/guns/aircraft, and the first bombers were born. In order to prevent the enemy from bombing, fighter aircraft were developed to intercept and shoot down enemy aircraft.
Tankers are used to refuel planes in mid-air, thus increasing their operational range.
Commercial aviation can be divided into passenger transport and cargo transport. For the former, large planes have been developed that can transport up to 500 passengers over large distances. Commercial cargo aircraft are often similar to military transport aircraft, or might be adapted from the passenger fleets of an earlier era.
Other uses include search-and-rescue operations (especially by helicopters), border protection and water-bombing (fire-fighting). Further divisions can be drawn between aircraft designs having conventional (taildraggers), tricycle (nosedragger), undercarriage, and amphibious floatplanes (wheeled aircraft converted with pontoon floats) or flying boats (which use the body of the aircraft for floation).
Related topics
- Aerial refueling
- Aeronautics
- Aircraft carrier
- Aircraft manufacturers
- Aircraft spotting
- Airline call signs
- Airliner
- Air safety
- Amelia Earhart
- Aviation
- Bomber
- Charles Lindbergh
- Contrail
- Early flying machines
- Fighter aircraft
- Flight controls
- Flight instruments
- Jet engine
- Lifting body
- Military aircraft
- Model aircraft
- Santos Dumont
- Spacecraft propulsion
- Spacecraft
- Successful aircraft types
- Undercarriage
- Wright brothers
External links
- Smithsonian Air and Space Museum http://www.nasm.si.edu/ - Excellent online collection with a particular focus on history of aircraft and spacecraft
- Virtual Museum http://invention.psychology.msstate.edu/Tale_of_Airplane/taleplane.html
- Prehistory of Powered Flight http://www.centennialofflight.gov/essay/Prehistory/PH-OV.htm
- Aircraft-Info.net http://www.aircraft-info.net
- HomebuiltAircraft.com http://www.HomebuiltAircraft.com - Information Portal about Homebuilt Aircraft
- The Evolution of Modern Aircraft (NASA) http://www.hq.nasa.gov/office/pao/History/SP-468/contents.htm
- Airforces http://www.DefenceTalk.com
- Series of Photo Essays on British Aviation http://www.challoner.com/aviation/index.html
- Check-Six http://www.check-six.com - Information on historic aircraft crashes including the X-15 and Flying Wing
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A separate article is about the movie Airplane!.