n.
The structure of an aircraft, such as an airplane, helicopter, or rocket, exclusive of its power plant.
airframe
Dictionary:
air·frame (âr'frām')  |
| 5min Related Video: airframe |
| Sci-Tech Encyclopedia: Airframe |
The structural backbone of an aircraft that balances the internal and external loads acting upon the craft. These loads consist of internal mass inertia forces (equipment, payload, stores, fuel, and so forth), flight forces (propulsion thrust, lift, drag, maneuver, wind gusts, and so forth), and ground forces (taxi, landing, and so forth).
The strength capability of the airframe must be predictable to ensure that these applied loads can be withstood with an adequate margin of safety throughout the life of the airplane. In addition to strength, the airframe requires structural stiffness to prevent excessive deformation under load and to provide a satisfactory natural frequency of the structure (the number of times per second the structure will vibrate when a load is suddenly imposed or changed). The aerodynamic loads on the airframe can oscillate in magnitude under some circumstances, and if these oscillations are near the same rate as the natural frequency of the structure, runaway deflections (called flutter) and failure can occur. Consequently, adequate structural stiffness is needed to provide a natural frequency far above the danger range. See also Aeroelasticity.
The overall airframe structure is made up of a number of separate components, each of which performs discrete individual functions. The fuselage provides the accommodations of crew, passengers, cargo, fuel, and environmental control systems. The empennage consists of the vertical and horizontal stabilizers, which are used, respectively, for turning and pitching flight control. The wing passing through the air provides lift to the aircraft. Its related control devices, leading-edge slats and trailing-edge flaps, are used to increase this lift at slow airspeeds, such as during landing and takeoff, to prevent stalling and loss of lift. The ailerons increase lift on one side of the wing and reduce lift on the other in order to roll the airplane about its fore-and-aft axis. See also Aileron; Elevon; Fuselage; Wing.
Performance requirements (range, payload, speed, altitude, landing and takeoff distance, and so forth) dictate that the airframe be designed and constructed so as to minimize its weight. All the airframe material must be arranged and sized so that it is utilized as near its capacity as possible, and so that the paths between applied loads and their reactions are as direct and as short as possible. The accomplishment of these goals, however, is compromised by constraints such as maintenance of the aerodynamic shape, the location of equipment, minimum sizes or thicknesses that are practical to manufacture, and structural stability, among others.
To maintain structural efficiency (minimum weight), the material that forms the aerodynamic envelope of the airplane is also utilized as a primary load-carrying member of the airframe. For example, the thin sheets that are commonly used for outer fuselage skins are very efficient in carrying in-plane loads like tension and shear when they are stabilized (prevented from moving or deflecting out of the way when loads are applied). This structural support is provided by circumferential frames and longitudinal primary members called longerons. The compression loads are also carried in the longerons and the thin skins when they are additionally stabilized by multiple secondary longitudinal stiffeners that are normally located between the frames. Illustration a shows a typical fuselage primary load path structure indicating the frames and longerons. This skeleton will be covered by thin skins.
X-31 aircraft. (a) Fuselage structural load paths. (b) Finite element model. (Rockwell International)
Various analytical techniques may be used to determine the internal stress levels for each of the airframe components. The most common analytical methods use the technique of reducing these highly complex structural arrangements into a group of well-defined simple structures known as finite elements. This simplification allows the load distribution to be solved by a series of algebraic equations.
The finite element model used for the determination of the internal load distribution must support various structural objectives that include the analysis of strength, stiffness, and damage tolerance characteristics of the aircraft. In order to accomplish these objectives the finite element model must represent the vehicle configuration in sufficient detail to define adequately the basic characteristics of the local structural load paths and provide for application of all external loading parameters. Illustration b shows the complete finite element model of an airframe. The many varied loading parameters include airloads, structural weight, engine thrust, landing gear reactions, fuel tanks, cargo, and passengers. Environmental factors such as cabin pressure and structural heating must also be considered.
| US Military Dictionary: airframe |
n. 1. the structural components of an airplane, including the framework and skin of such parts as the fuselage, empennage, wings, landing gear (minus tires), and engine mounts.
2. the framework, envelope, and cabin of an airship.
3. the assembled principal structural components of a missile, not including the propulsion system, control system, electronic equipment, and payload.
See the Introduction, Abbreviations and Pronunciation for further details.
| Wikipedia: Airframe |
For the novel by Michael Crichton, see Airframe (novel).
The term airframe refers to the mechanical structure of an aircraft,[1] and as generally used does not include the propulsion system. Airframe design is a challenging field of engineering, combining aerodynamics, materials technology and manufacturing methods to achieve favorable balances of performance, reliability and cost.
Contents |
History
Modern airframe history began in the United States when a 1903 wood biplane made by Orville and Wilbur Wright showed the potential of fixed-wing designs. Many early developments were spurred by military needs during World War I. Well known aircraft from that era include the Dutch Fokker and U.S. Curtiss triplanes and the Italian Taube monoplane. These used hybrid wood and metal structures. Commercial airframe development during the 1920s and 1930s focused on monoplane designs using radial piston engines. Many, such as the Ryan model flown across the Atlantic by Charles Lindbergh in 1927, were produced as single copies or in small quantity. The all-metal Ford 4-AT and 5-AT trimotors[2] and Douglas DC-3 twin prop[3] were among the most successful designs to emerge from the era. During World War II, military needs again dominated airframe designs. Among the best known were the Douglas C-47, Boeing B-17, North American B-25 and Lockheed P-38, all revamps of original designs from the 1930s. The first jets were produced during the war but not made in large quantity.
Postwar commercial airframe design focused on larger capacities, on turboprop engines, and then on jet (turbojet, later turbofan) engines. The generally higher speeds and stresses of turboprops and jets were major challenges.[4] Newly developed aluminum alloys with copper, magnesium and zinc were critical to these designs.[5] The Lockheed L-188 turboprop, first flown in 1957, used some of these materials and became a costly lesson in controlling vibration and planning around metal fatigue. Eventually Boeing in the U.S. and Airbus in Europe became the dominant assemblers of large airframes, known as wide-body aircraft. Numerous manufacturers in Europe, North America and South America took over markets for airframes designed to carry 100 or fewer passengers. Many manufacturers produce airframe components.
Present and Future
Four major eras in commercial airframe production stand out: all-aluminum structures beginning in the 1920s, high-strength alloys and high-speed airfoils beginning in the 1940s, long-range designs and improved efficiencies beginning in the 1960s, and composite material construction beginning in the 1980s. In the latest era, Boeing has claimed a lead, designing its new 787 series flagship airframes (scheduled for entry into service in 2010) with a one-piece carbon-fiber fuselage, said to replace "1,200 sheets of aluminum and 40,000 rivets."[6] These airframes are designed to transport 220-300 passengers, while chief competitor Airbus has designed its A380 flagship airframes to transport 550-850 passengers. The A380 is also built with a large proportion of composite material.
Airframe production has become an exacting process. Manufacturers operate under strict quality control and government regulations. Departures from established standards become objects of major concern.[7] The crash on takeoff of an Airbus A300 in 2001, after its tail assembly broke away from the fuselage, called attention to operation, maintenance and design issues involving composite materials that are used in many recent airframes.[8] [9] [10] The A300 had experienced other structural problems but none of this magnitude. The incident bears comparison with the 1959 Lockheed L-188 crash in showing difficulties that the airframe industry and its airline customers can experience when adopting new technology.
See also
- Wing
- Fuselage
- Rib (aircraft)
- Spar (aviation)
- Chord (aircraft)
- Aircraft fairing
- Fillet (aircraft)
- Vertical stabilizer
Notes and references
- ^ Ed Rouen (2005). Airplane Names. San Diego Aerospace Museum. http://www.marchfield.org/rouen01.html. Names and dates of more than 2,800 aircraft models produced since 1900.
- ^ David A. Weiss (1996). The Saga of the Tin Goose. Cumberland Enterprises.
- ^ Peter M. Bowers (1986). The DC-3: 50 Years of Legendary Flight. Tab Books.
- ^ Charles D. Bright (1978). The Jet Makers: the Aerospace Industry from 1945 to 1972. Regents Press of Kansas. http://www.generalatomic.com/jetmakers/index.html.
- ^ Key to Metals Database (2005). Aircraft and Aerospace Applications. INI International. http://www.key-to-metals.com/PrintArticle.asp?ID=96.
- ^ Leslie Wayne (May 7 2006). "Boeing Bets the House on Its 787 Dreamliner". New York Times. http://www.nytimes.com/2006/05/07/business/yourmoney/07boeing.html.
- ^ Florence Graves and Sara K. Goo (Apr 17 2006). "Boeing Parts and Rules Bent, Whistle-Blowers Say". Washington Post. http://www.washingtonpost.com/wp-dyn/content/article/2006/04/16/AR2006041600803.html. U.S. "whistleblower" lawsuit.
- ^ Todd Curtis (2002). "Investigation of the Crash of American Airlines Flight 587". AirSafe.com. http://www.airsafe.com/events/aa587.htm.
- ^ James H. Williams, Jr. (2002). "Flight 587". Massachusetts Institute of Technology. http://web.mit.edu/jhwill/www/Flight587.html.
- ^ Sara Kehaulani Goo (Oct 27 2004). "NTSB Cites Pilot Error in 2001 N.Y. Crash". Washington Post. http://www.washingtonpost.com/wp-dyn/articles/A63850-2004Oct26.html.
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| Translations: Airframe |
Nederlands (Dutch)
romp van vliegtuig
Français (French)
n. - cellule d'avion
Deutsch (German)
n. - Flugwerk
Ελληνική (Greek)
n. - αεροπλαίσιο, φέρουσα κατασκευή αεροσκάφους
Italiano (Italian)
cellula (aer.)
Português (Portuguese)
n. - estrutura (f) de avião (Aer.)
Русский (Russian)
корпус самолета
Español (Spanish)
n. - estructura de avión
Svenska (Swedish)
n. - flygplansskrov
中文（简体）(Chinese (Simplified))
机身
中文（繁體）(Chinese (Traditional))
n. - 機身
العربيه (Arabic)
(الاسم) هيكل ألطائره, جسم ألطائره
עברית (Hebrew)
n. - גוף המטוס
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 | Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved. Read more |
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| Sci-Tech Encyclopedia. McGraw-Hill Encyclopedia of Science and Technology. Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved. Read more |
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| US Military Dictionary. The Oxford Essential Dictionary of the U.S. Military. Copyright © 2001, 2002 by Oxford University Press, Inc. All rights reserved. Read more |
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