|
Swept-wing
A swept wing is a wing that angles either backward or occasionally forward from its root rather than in a straight sideways direction. Swept wings have been flown since the pioneer days of aviation. Wing sweep at high speeds was first investigated in Germany as early as 1935 by Albert Betz and Adolph Busemann, finding application just before the end of the Second World War. It has the effect of delaying the shock waves and accompanying aerodynamic drag rise caused by fluid compressibility near the speed of sound, improving performance. Swept wings are therefore almost always used on jet aircraft designed to fly at these speeds. The term "swept wing" is normally used to mean "swept back", but variants include forward sweep, variable sweep wings and oblique wings in which one side sweeps forward and the other back. The delta wing is also aerodynamically a form of swept wing. Reasons for sweep There are three main reasons for sweeping a wing: 1. to arrange the center of gravi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sabre Dance (pitch-up)
In aerodynamics, pitch-up is an uncommanded nose-upwards rotation of an aircraft. It is an undesirable characteristic that has been observed mostly in experimental swept-wing aircraft at high subsonic Mach numbers or high angle of attack. History Pitch-up problems were first noticed on high-speed test aircraft with swept wings. It was a common problem on the Douglas Skyrocket, which was used extensively to test the problem. Before the pitch-up phenomenon was well understood, it plagued all early swept-wing aircraft. In the F-100 Super Sabre it even got its own name, the Sabre dance. In aircraft with high-mounted tailplanes, like the F-101 Voodoo, recovery was especially difficult because the tailplane was placed directly in the wing wake during the pitch-up, causing Stall (flight)#Deep stall, deep stall (although the T-tail was meant to prevent pitch-up from starting in the first place). Deployment of the braking parachute and a considerable height above the ground were essential f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HFB 320 Hansa Jet
The HFB 320 Hansa Jet is a twin-engine, ten-seat business jet that was designed and produced by German aircraft manufacturer Hamburger Flugzeugbau between 1964 and 1973. The most recognisable and unconventional feature of the aircraft is its forward-swept wing. The Hansa Jet begun development during the 1960s, the selection of the forward-swept wing can be largely attributed to head engineer Hans Wocke, who had previously worked on the experimental Junkers Ju 287. It possessed a spacious cabin, which was achieved due to its wing design, but was a relatively heavy aircraft, posing some issues during both take-off and landing. On 21 April 1964, the prototype conducted its maiden flight. On 12 May 1965, the first prototype was lost during a test flight, killing Hamburger Flugzeugbau's chief test pilot; several design changes were made to change the Hansa Jet's stall characteristics. Type certification of the Hansa Jet was received during early 1967 and the first deliveries commen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adolph Busemann
Adolf Busemann (20 April 1901 – 3 November 1986) was a German aerospace engineer and influential Nazi-era pioneer in aerodynamics, specialising in supersonic airflows. He introduced the concept of swept wings and, after emigrating in 1947 to the United States under Operation Paperclip, invented the shockwave-free supersonic Busemann biplane. Education and early life Born in Lübeck, Germany, Busemann attended the Technical University of Braunschweig, receiving his Ph.D. in engineering in 1924. Career and research The next year he was given the position of aeronautical research scientist at the Max-Planck Institute where he joined the famed team led by Ludwig Prandtl, including Theodore von Kármán, Max Munk and Jakob Ackeret. In 1930 he was promoted to professor at University of Göttingen. He held various positions within the German scientific community during this period, and during the war he was the director of the Braunschweig Laboratory, a famous research establishme ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Angle Of Attack
In fluid dynamics, angle of attack (AOA, α, or \alpha) is the angle between a reference line on a body (often the chord line of an airfoil) and the vector representing the relative motion between the body and the fluid through which it is moving. Angle of attack is the angle between the body's reference line and the oncoming flow. This article focuses on the most common application, the angle of attack of a wing or airfoil moving through air. In aerodynamics, angle of attack specifies the angle between the chord line of the wing of a fixed-wing aircraft and the vector representing the relative motion between the aircraft and the atmosphere. Since a wing can have twist, a chord line of the whole wing may not be definable, so an alternate reference line is simply defined. Often, the chord line of the root of the wing is chosen as the reference line. Another choice is to use a horizontal line on the fuselage as the reference line (and also as the longitudinal axis). Some aut ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mach Cone
In fluid dynamics, a Mach wave is a pressure wave traveling with the speed of sound caused by a slight change of pressure added to a compressible flow. These weak waves can combine in supersonic flow to become a shock wave if sufficient Mach waves are present at any location. Such a shock wave is called a Mach stem or Mach front. Thus, it is possible to have shockless compression or expansion in a supersonic flow by having the production of Mach waves sufficiently spaced (''cf.'' isentropic compression in supersonic flows). A Mach wave is the weak limit of an oblique shock wave where time averages of flow quantities don't change; (a normal shock is the other limit). If the size of the object moving at the speed of sound is near 0, then this domain of influence of the wave is called a Mach cone. Mach angle A Mach wave propagates across the flow at the Mach angle ''μ'', which is the angle formed between the Mach wave wavefront and a vector that points opposite to the vector of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Douglas DC-8
The Douglas DC-8 (sometimes McDonnell Douglas DC-8) is a long-range narrow-body airliner built by the American Douglas Aircraft Company. After losing the May 1954 US Air Force tanker competition to the Boeing KC-135, Douglas announced in July 1955 its derived jetliner project. In October 1955, Pan Am made the first order along with the competing Boeing 707, and many other airlines followed. The first DC-8 was rolled out in Long Beach Airport on April 9, 1958, and flew for the first time on May 30. FAA certification was achieved in August 1959 and the DC-8 entered service with Delta Air Lines on September 18. The six-abreast, low wing airliner was a four-engined jet aircraft with initial variants being long. The DC-8-10 was powered by Pratt & Whitney JT3C turbojets and had a MTOW, the DC-8-20 had more powerful JT4A turbojets for a MTOW. The intercontinental models had more fuel capacity and up to MTOW, powered by JT4As for the Series 30 and by Rolls-Royce Conway turbofa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dietrich Küchemann
Dietrich Küchemann CBE FRS FRAeS (11 September 1911 – 23 February 1976) was a German aerodynamicist who made several important contributions to the advancement of high-speed flight. He spent most of his career in the UK, where he is best known for his work on Concorde. Biography Küchemann was born in Göttingen where he studied at its University of Göttingen, home of the largest German institute of aerodynamics. He was originally going to move on to pure physics research under Max Born, a friend of his father's, but lost this chance when Born and several other Jewish members of the University staff were expelled from the country by the Nazi regime. Instead Küchemann went on to join Ludwig Prandtl in aerodynamics research. He published his doctoral thesis in 1936. With the war looming, Küchemann volunteered for service in 1938, and as expected was given a non-combatant role in Signals. He held the rank of Unteroffizier from 1942 to 1945, but he saw no active ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oblique Wing
An oblique wing (also called a slewed wing) is a variable geometry wing concept. On an aircraft so equipped, the wing is designed to rotate on center pivot, so that one tip is swept forward while the opposite tip is swept aft. By changing its sweep angle in this way, drag can be reduced at high speed (with the wing swept) without sacrificing low speed performance (with the wing perpendicular). This is a variation on the classic swing-wing design, intended to simplify construction and retain the center of gravity as the sweep angle is changed. History The oldest examples of this technology are the unrealized German aircraft projects Blohm & Voss P.202 and Messerschmitt Me P.1009-01 from the year 1944, based on a Messerschmitt patent. After the war, constructor Dr. Richard Vogt was brought to the US during Operation Paperclip. The oblique wing concept was resurrected by Robert T. Jones, an aeronautical engineer at the NASA Ames Research Center, Moffett Field, California. Analytic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Empennage
The empennage ( or ), also known as the tail or tail assembly, is a structure at the rear of an aircraft that provides stability during flight, in a way similar to the feathers on an arrow.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', p. 194. Aviation Supplies & Academics, 1997. Aviation Publishers Co. Limited, ''From the Ground Up'', p. 10 (27th revised edition) The term derives from the French language verb ''empenner'' which means " to feather an arrow". Most aircraft feature an empennage incorporating vertical and horizontal stabilising surfaces which stabilise the flight dynamics of yaw and pitch, as well as housing control surfaces. In spite of effective control surfaces, many early aircraft that lacked a stabilising empennage were virtually unflyable. Even so-called "tailless aircraft" usually have a tail fin (usually a vertical stabiliser). Heavier-than-air aircraft without any kind of empennage (such as the Northrop B-2) are rare, and generally u ... [...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] |
Critical Mach
In aerodynamics, the critical Mach number (Mcr or M*) of an aircraft is the lowest Mach number at which the airflow over some point of the aircraft reaches the speed of sound, but does not exceed it.Clancy, L.J. ''Aerodynamics'', Section 11.6 At the lower critical Mach number, airflow around the entire aircraft is subsonic. Supersonic aircraft such as Concorde and combat aircraft also have an upper critical Mach number at which the airflow around the entire aircraft is supersonic. Aircraft flight For an aircraft in flight, the speed of the airflow around the aircraft differs considerably in places from the airspeed of the aircraft; this is due to the airflow having to speed up and slow down as it travels around the aircraft's structure. When the aircraft's airspeed reaches the critical Mach number, the speed of the airflow in some areas near the airframe reaches the speed of sound, even though the aircraft itself has an airspeed lower than Mach 1.0. This creates a weak shock wave ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Drag (physics)
In fluid dynamics, drag (sometimes called air resistance, a type of friction, or fluid resistance, another type of friction or fluid friction) is a force acting opposite to the relative motion of any object moving with respect to a surrounding fluid. This can exist between two fluid layers (or surfaces) or between a fluid and a solid surface. Unlike other resistive forces, such as dry friction, which are nearly independent of velocity, the drag force depends on velocity. Drag force is proportional to the velocity for low-speed flow and the squared velocity for high speed flow, where the distinction between low and high speed is measured by the Reynolds number. Even though the ultimate cause of drag is viscous friction, turbulent drag is independent of viscosity. Drag forces always tend to decrease fluid velocity relative to the solid object in the fluid's path. Examples Examples of drag include the component of the net aerodynamic or hydrodynamic force acting opposite to the d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
