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Slowed Rotor
The slowed rotor principle is used in the design of some helicopters. On a conventional helicopter the rotational speed of the rotor is constant; reducing it at lower flight speeds can reduce fuel consumption and enable the aircraft to fly more economically. In the compound helicopter and related aircraft configurations such as the gyrodyne and winged autogyro, reducing the rotational speed of the rotor and offloading part of its lift to a fixed wing reduces drag, enabling the aircraft to fly faster. Introduction Traditional helicopters get both their propulsion and lift from the main rotor; by using a dedicated propulsion device such as a propeller or jet engine, the rotor burden is lessened.Chandler, Jay.Advanced rotor designs break conventional helicopter speed restrictions (page 1) The "relative blade tip speed" u is the tip speed relative to the aircraft (not the airspeed of the tip). Thus the formula for Advance ratio is \mu = \frac = \frac where Omega (Ω) is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
McDonnell XV-1 In Flight
The McDonnell Aircraft Corporation was an American aerospace manufacturer based in St. Louis, Missouri. The company was founded on July 6, 1939, by James Smith McDonnell, and was best known for its military fighters, including the F-4 Phantom II, and crewed spacecraft including the Mercury capsule and Gemini capsule. McDonnell Aircraft later merged with the Douglas Aircraft Company to form McDonnell Douglas in 1967. History James McDonnell founded J.S. McDonnell & Associates in Milwaukee, Wisconsin, in 1928 to produce a small aircraft for family use.J.S. McDonnell & Associates, Early years: 1927-1938 (part 1) , Boeing.com. The economic depression from 1929 ruined his plans and the company collapsed. He went to work for [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flight Global
FlightGlobal is an online news and information website which covers the aviation and aerospace industries. The website was established in February 2006 as the website of ''Flight International ''Flight International'' is a monthly magazine focused on aerospace. Published in the United Kingdom and founded in 1909 as "A Journal devoted to the Interests, Practice, and Progress of Aerial Locomotion and Transport", it is the world's olde ...'' magazine, ''Airline Business'', ''ACAS'', ''Air Transport Intelligence'' (ATI), ''The Flight Collection'' and other services and directories. FlightGlobal is a resource for aviation history with a picture library of over 1 million images starting with the foundation of ''Flight'' in 1909. Thousands of images and back copies of ''Flight'' are searchable online. FlightGlobal won the prize for of "Business Website of the Year" at the Association of Online Publishers' Digital Publishing Awards 2010. According to the contest judges, "The si ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Drag Divergence Mach Number
The drag-divergence Mach number (not to be confused with critical Mach number) is the Mach number at which the aerodynamic drag on an airfoil or airframe begins to increase rapidly as the Mach number continues to increase. This increase can cause the drag coefficient to rise to more than ten times its low-speed value. The value of the drag-divergence Mach number is typically greater than 0.6; therefore it is a transonic effect. The drag-divergence Mach number is usually close to, and always greater than, the critical Mach number. Generally, the drag coefficient peaks at Mach 1.0 and begins to decrease again after the transition into the supersonic regime above approximately Mach 1.2. The large increase in drag is caused by the formation of a shock wave on the upper surface of the airfoil, which can induce flow separation and adverse pressure gradients on the aft portion of the wing. This effect requires that aircraft intended to fly at supersonic speeds have a large amount ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Speed Of Sound
The speed of sound is the distance travelled per unit of time by a sound wave as it propagates through an elastic medium. At , the speed of sound in air is about , or one kilometre in or one mile in . It depends strongly on temperature as well as the medium through which a sound wave is propagating. At , the speed of sound in air is about . The speed of sound in an ideal gas depends only on its temperature and composition. The speed has a weak dependence on frequency and pressure in ordinary air, deviating slightly from ideal behavior. In colloquial speech, ''speed of sound'' refers to the speed of sound waves in air. However, the speed of sound varies from substance to substance: typically, sound travels most slowly in gases, faster in liquids, and fastest in solids. For example, while sound travels at in air, it travels at in water (almost 4.3 times as fast) and at in iron (almost 15 times as fast). In an exceptionally stiff material such as diamond, sound travel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transonic
Transonic (or transsonic) flow is air flowing around an object at a speed that generates regions of both subsonic and supersonic airflow around that object. The exact range of speeds depends on the object's critical Mach number, but transonic flow is seen at flight speeds close to the speed of sound (343 m/s at sea level), typically between Mach 0.8 and 1.2. The issue of transonic speed (or transonic region) first appeared during World War II. Pilots found as they approached the sound barrier the airflow caused aircraft to become unsteady. Experts found that shock waves can cause large-scale separation downstream, increasing drag and adding asymmetry and unsteadiness to the flow around the vehicle. Research has been done into weakening shock waves in transonic flight through the use of anti-shock bodies and supercritical airfoils. Most modern jet powered aircraft are engineered to operate at transonic air speeds. Transonic airspeeds see a rapid increase in drag fro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dissymmetry Of Lift
Dissymmetry of lift (also known as asymmetry of lift or asymmetric lift) in rotorcraft aerodynamics refers to an unequal amount of lift on opposite sides of the rotor disc. It is a phenomenon that affects single-rotor helicopters and autogyros in forward flight. A rotor blade that is moving in the same direction as the aircraft is called the ''advancing blade'' and the blade moving in the opposite direction is called the ''retreating blade.'' When viewed from above, most American helicopter rotors turn counter-clockwise; French and Russian helicopters turn clockwise. Balancing lift across the rotor disc is important to a helicopter's stability. The amount of lift generated by an airfoil is proportional to the square of its airspeed (velocity). In a hover, the rotor blades have equal airspeeds and therefore equal lift. However, in forward flight the advancing blade has a higher airspeed than the retreating blade, creating uneven lift across the rotor disc. Analysis Consider a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retreating Blade Stall
Retreating blade stall is a hazardous flight condition in helicopters and other rotary wing aircraft, where the retreating rotor blade has a lower relative blade speed, combined with an increased angle of attack, causing a stall and loss of lift. Retreating blade stall is the primary limiting factor of a helicopter's never exceed speed, VNE. Retreating blade stall occurs at high forward speeds, and should not be confused with rotor stall, which is caused by low rotor RPM and can occur at any forward speed. Advancing vs. retreating blades A rotor blade that is moving in the same direction as the aircraft is called the ''advancing blade'' and the blade moving in the opposite direction is called the ''retreating blade.'' Balancing lift across the rotor disc is important to a helicopter's stability. The amount of lift generated by an airfoil is proportional to the square of its airspeed (velocity). In a zero airspeed hover the rotor blades, regardless of their position in rotat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Air & Space/Smithsonian
''Air & Space/Smithsonian'' is a quarterly magazine published by the National Air and Space Museum The National Air and Space Museum of the Smithsonian Institution, also called the Air and Space Museum, is a museum in Washington, D.C., in the United States. Established in 1946 as the National Air Museum, it opened its main building on the N ... in Washington, D.C., United States. Its first publication was in April 1986. Articles in the magazine involve topics related to aviation and space travel, historical and current. It also covers military aviation and aeronautical technology. References External links * 1986 establishments in Washington, D.C. Bimonthly magazines published in the United States History magazines published in the United States Aviation magazines Magazines established in 1986 Magazines published in Washington, D.C. Smithsonian Institution publications {{hist-mag-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flight Envelope
In aerodynamics, the flight envelope, service envelope, or performance envelope of an aircraft or spacecraft refers to the capabilities of a design in terms of airspeed and load factor or atmospheric density, often simplified to altitude. The term is somewhat loosely applied, and can also refer to other measurements such as maneuverability. When a plane is pushed, for instance by diving it at high speeds, it is said to be flown "outside the envelope", something considered rather dangerous. Flight envelope is one of a number of related terms that are all used in a similar fashion. It is perhaps the most common term because it is the oldest, first being used in the early days of test flying. It is closely related to more modern terms known as extra power and a doghouse plot which are different ways of describing a flight envelope. In addition, the term has been widened in scope outside the field of engineering, to refer to the strict limits in which an event will take place or mor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
US Army Aviation
The United States Army Aviation Branch is the administrative organization within the United States Army responsible for doctrine, manning and configuration for all army aviation units. After the United States Army Air Corps grew into the Army Air Forces and split into the new service, the United States Air Force, the Army was left with its sole fixed-wing aviation units flying Taylorcraft L-2 Grasshopper observation planes for artillery units. The Army would develop a new concept of aviation using the helicopter that would show promise during the Korean War and would revolutionize warfare during the Vietnam War. History Origins of Army Aviation Army Aviation traces its origins back to the American Civil War. Both Union and Confederate forces used hydrogen-filled balloons to direct artillery fire, marking the beginning of U.S. military aeronautics and of aerial support of Army ground forces. The Army also used balloons during the Spanish–American War and World War I, but airp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sikorsky UH-60 Black Hawk
The Sikorsky UH-60 Black Hawk is a four-blade, twin-engine, medium-lift utility military helicopter manufactured by Sikorsky Aircraft. Sikorsky submitted the S-70 design for the United States Army's Utility Tactical Transport Aircraft System (UTTAS) competition in 1972. The Army designated the prototype as the ''YUH-60A'' and selected the Black Hawk as the winner of the program in 1976, after a fly-off competition with the Boeing Vertol YUH-61. Named after the Native American war leader Black Hawk, the UH-60A entered service with the U.S. Army in 1979, to replace the Bell UH-1 Iroquois as the Army's tactical transport helicopter. This was followed by the fielding of electronic warfare and special operations variants of the Black Hawk. Improved UH-60L and UH-60M utility variants have also been developed. Modified versions have also been developed for the U.S. Navy, Air Force, and Coast Guard. In addition to U.S. Army use, the UH-60 family has been exported to several nations. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wired (website)
''Wired'' (stylized as ''WIRED'') is a monthly American magazine, published in print and online editions, that focuses on how emerging technologies affect culture, the economy, and politics. Owned by Condé Nast, it is headquartered in San Francisco, California, and has been in publication since March/April 1993. Several spin-offs have been launched, including ''Wired UK'', ''Wired Italia'', ''Wired Japan'', and ''Wired Germany''. From its beginning, the strongest influence on the magazine's editorial outlook came from founding editor and publisher Louis Rossetto. With founding creative director John Plunkett, Rossetto in 1991 assembled a 12-page prototype, nearly all of whose ideas were realized in the magazine's first several issues. In its earliest colophons, ''Wired'' credited Canadian media theorist Marshall McLuhan as its "patron saint". ''Wired'' went on to chronicle the evolution of digital technology and its impact on society. ''Wired'' quickly became recognized a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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