搜尋結果
The double sovereign is a gold coin of the United Kingdom with a nominal value of two pounds sterling (£2). It features the reigning monarch on its obverse and, most often, Benedetto Pistrucci 's depiction of Saint George and the Dragon on the reverse (pictured). It was rarely issued in the first century and a half after its debut in 1820 ...
Taiwan,[II][k] officially the Republic of China (ROC),[I][l] is a country[27] in East Asia.[o] It is located at the junction of the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the northeast, and the Philippines to the south. The territories controlled by the ...
2024 AFC U-23 Asian Cup. The 2024 AFC U-23 Asian Cup was the 6th edition of the AFC U-23 Asian Cup (previously the AFC U-23 Championship before rebranding from 2021), [1] the biennial international age-restricted football championship organised by the Asian Football Confederation (AFC) for the men's under-23 national teams of Asia.
- Etymology and Usage
- History
- Propulsion
- Design and Manufacture
- Characteristics
- Safety
- Environmental Impact
- See Also
- Bibliography
- External Links
First attested in English in the late 19th century (prior to the first sustained powered flight), the word airplane, like aeroplane, derives from the French aéroplane, which comes from the Greek ἀήρ (aēr), "air" and either Latin planus, "level", or Greek πλάνος (planos), "wandering". "Aéroplane" originally referred just to the wing, as it is a plan...
Antecedents
Many stories from antiquity involve flight, such as the Greek legend of Icarus and Daedalus, and the Vimana in ancient Indian epics. Around 400 BC in Greece, Archytas was reputed to have designed and built the first artificial, self-propelled flying device, a bird-shaped model propelled by a jet of what was probably steam, said to have flown some 200 m (660 ft).This machine may have been suspended for its flight. Some of the earliest recorded attempts with gliders were those by the 9th-centur...
Early powered flights
The Frenchman Clement Ader constructed his first of three flying machines in 1886, the Éole. It was a bat-like design run by a lightweight steam engine of his own invention, with four cylinders developing 20 horsepower (15 kW), driving a four-blade propeller. The engine weighed no more than 4 kilograms per kilowatt (6.6 lb/hp). The wings had a span of 14 m (46 ft). All-up weight was 300 kilograms (660 lb). On 9 October 1890, Ader attempted to fly the Éole. Aviation historians give credit to t...
Development of jet aircraft
The first practical jet aircraft was the German Heinkel He 178, which was tested in 1939. In 1943, the Messerschmitt Me 262, the first operational jet fighter aircraft, went into service in the German Luftwaffe. The first jet airliner, the de Havilland Comet, was introduced in 1952. The Boeing 707, the first widely successful commercial jet, was in commercial service for more than 50 years, from 1958 to 2010. The Boeing 747 was the world's biggest passenger aircraft from 1970 until it was sur...
Propeller
An aircraft propeller, or airscrew, converts rotary motion from an engine or other power source, into a swirling slipstream which pushes the propeller forwards or backwards. It comprises a rotating power-driven hub, to which are attached two or more radial airfoil-section blades such that the whole assembly rotates about a longitudinal axis. Three types of aviation engines used to power propellers include reciprocating engines (or piston engines), gas turbines, and electric motors. The amount...
Jet
Jet aircraft are propelled by jet engines, which are used because the aerodynamic limitations of propellers do not apply to jet propulsion. These engines are much more powerful than a reciprocating engine for a given size or weight and are comparatively quiet and work well at higher altitude. Variants of the jet engine include the ramjet and the scramjet, which rely on high airspeed and intake geometry to compress the combustion air, prior to the introduction and ignition of fuel. Rocket moto...
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 or longer for larger planes. During this process, the objectives and design specifications of the aircraft are established. First the cons...
Airframe
The structural parts of a fixed-wing aircraft are called the airframe. The parts present can vary according to the aircraft's type and purpose. Early types were usually made of wood with fabric wing surfaces, When engines became available for powered flight around a hundred years ago, their mounts were made of metal. Then as speeds increased more and more parts became metal until by the end of WWII all-metal aircraft were common. In modern times, increasing use of composite materialshas been...
Wings
The wings of a fixed-wing aircraft are static planes extending either side of the aircraft. When the aircraft travels forwards, air flows over the wings, which are shaped to create lift. This shape is called an airfoiland is shaped like a bird's wing.
Fuselage
A fuselage is a long, thin body, usually with tapered or rounded ends to make its shape aerodynamically smooth. The fuselage may contain the flight crew, passengers, cargo or payload, fuel and engines. The pilots of manned aircraft operate them from a cockpitlocated at the front or top of the fuselage and equipped with controls and usually windows and instruments. A plane may have more than one fuselage, or it may be fitted with booms with the tail located between the booms to allow the extre...
When risk is measured by deaths per passenger kilometer, air travel is approximately 10 times safer than travel by bus or rail. However, when using the deaths per journey statistic, air travel is significantly more dangerous than car, rail, or bus travel. Air travel insurance is relatively expensive for this reason—insurers generally use the deaths...
Like all activities involving combustion, fossil-fuel-powered aircraft release soot and other pollutants into the atmosphere. Greenhouse gases such as carbon dioxide (CO2) are also produced. In addition, there are environmental impacts specific to airplanes: for instance, 1. Airplanes operating at high altitudes near the tropopause (mainly large je...
Blatner, David. The Flying Book: Everything You've Ever Wondered About Flying On Airplanes. ISBN 0-8027-7691-4
The Boeing 777, commonly referred to as the Triple Seven, is an American long-range wide-body airliner developed and manufactured by Boeing Commercial Airplanes. The 777 is the world's largest twinjet and the most-built wide-body airliner.
The UEFA Champions League (previously known as the European Cup, abbreviated as UCL, or sometimes, UEFA CL) is an annual club association football competition organised by the Union of European Football Associations (UEFA) and contested by top-division European clubs, deciding the competition winners through a round robin group stage to qualify ...
In mathematics, the Pythagorean theorem or Pythagoras' theorem is a fundamental relation in Euclidean geometry between the three sides of a right triangle. It states that the area of the square whose side is the hypotenuse (the side opposite the right angle) is equal to the sum of the areas of the squares on the other two sides.
