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Fourth-generation jet fighter is a general classification of jet fighters in service from approximately 1980 to present day, and represent design concepts of the 1970s. Fourth-generation designs are heavily influenced by lessons learned from the previous generation of combat aircraft. Long-range air-to-air missiles, originally thought to make dogfighting obsolete, proved less influential than expected, precipitating a renewed emphasis on maneuverability. Meanwhile, the growing costs of military aircraft in general and the demonstrated success of aircraft such as the F-4 Phantom II gave rise to the popularity of Multirole combat aircraft in parallel with the advances marking the so-called fourth generation. During the period in question, maneuverability was enhanced by relaxed static stability, made possible by introduction of the fly-by-wire (FBW) flight control system (FLCS), which in turn was possible due to advances in digital computers and system integration techniques. Analog avionics, required to enable FBW operations, became a fundamental requirement and began to be replaced by digital flight control systems in the latter half of the 1980s.〔 The further advance of microcomputers in the 1980s and 1990s permitted rapid upgrades to the avionics over the lifetimes of these fighters, incorporating system upgrades such as active electronically scanned array (AESA), digital avionics buses and Infra-red search and track (IRST). Due to the dramatic enhancement of capabilities in these upgraded fighters and in new designs of the 1990s that reflected these new capabilities, the US Government has taken to using the designation 4.5 generation to refer to these later designs. This is intended to reflect a class of fighters that are evolutionary upgrades of the 4th generation incorporating integrated avionics suites, advanced weapons efforts to make the (mostly) conventionally designed aircraft nonetheless less easily detectable, and trackable as a response to advancing missile and radar technology (see stealth technology).〔Fulghum, David A. and Douglas Barrie ("F-22 Tops Japan's Military Wish List." ) ''Aviation Week and Space Technology,'' 22 April 2007. Retrieved: 3 October 2010.〕〔("The Gray Threat." ) ''Air Force Magazine''.〕 Inherent airframe design features exist, and include masking of turbine-blades and application of advanced sometimes radar-absorbent materials, but not the distinctive low-observable configurations of the latest aircraft, referred to as fifth-generation fighters or aircraft such as the F-22 Raptor and the F-35 Lightning II. The United States defines 4.5 generation fighter aircraft as fourth generation jet fighters that have been upgraded with AESA radar, high capacity data-link, enhanced avionics, and "the ability to deploy current and reasonably foreseeable advanced armaments."〔("CRS RL33543: Tactical Aircraft Modernization." ) ''Issues for Congress 9 July 2009. Retrieved: 3 October 2010.〕〔("National Defense Authorization Act for Fiscal Year 2010 (Enrolled as Agreed to or Passed by Both House and Senate.") ) ''thomas.loc.gov.'' Retrieved: 3 October 2010.〕 Contemporary examples of 4.5 generation fighters are the Boeing F/A-18E/F Super Hornet and the Eurofighter Typhoon. ==Design considerations== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Fourth-generation jet fighter」の詳細全文を読む スポンサード リンク
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