Ну это чисто субъективный взглядСообщение от Kill Lock
McDonnell Douglas, North American Rockwell, and Fairchild-Republic submitted proposals in the ensuing design competition. Many of the basic design features of U.S. fighter aircraft have resulted from technology pioneered at NASA's Langley Research Center. In 1967, Langley disseminated the results of in-house studies of a fighter configuration known as LFAX-8, which incorporated several features that would later be evident in the F-15 aircraft. Some of these features were
* Short propulsion package to minimize weight
* Engines placed forward for balance
* Horizontal ramp engine inlets for good performance at high angles of attack
* Horizontal tails located far aft on booms for increased stability and control
* Tailored twin-engine aft-end spacing and interfairing for efficient subsonic cruise conditions
In 1968, the Department of Defense requested that NASA respond to the F-15 request for proposals (RFP) in a manner similar to the industry contractors. The key person behind the NASA participation was Dr. John Foster, Director of the Defense Department Research and Engineering organization. He requested the participation for two reasons. First, Foster felt that NASA’s aircraft designs for the F-15 mission would embody advanced technology and serve as the upper limit of technology for industry proposals. Second, NASA and its problem-solving expertise could minimize risks and problems later in the development program. Four fighter concepts were studied in great detail:
* LFAX-4—a variable-sweep configuration
* LFAX-8— a fixed-sweep version of LFAX-4
* LFAX-9—wing-mounted twin-engine configuration
* LFAX-10—similar in external shape to Soviet MiG-25 Foxbat
Industry design teams visited Langley during the efforts and were continually updated on the advantages, disadvantages, and technical maturity of the configurations. The NASA team also briefed high ranking DOD officials. The LFAX-4 and LFAX-8 embodied features that would subsequently be evident in the McDonnell Douglas F-15 and Northrop Grumman F-14 aircraft. The LFAX-8 design made an indelible impression on the McDonnell Douglas design team, which embraced the fundamental layout of the NASA configuration. The cranked-wing design of the LFAX-8 had to be modified by McDonnell Douglas as the requirements for transonic maneuvering became more important. Another modification to the LFAX-8 involved the installation of a larger radar dish in the nose than the NASA team had allowed for in their design. The installation required a larger diameter nose cone, and although the NASA researchers deplored the increased supersonic drag caused by the larger nose, the final design incorporated the larger dish.
An industry-wide competition ended on December 23, 1969 when McDonnell Douglas was awarded the contract for the F-15.
Previous experiences with the F-111 and other advanced fighter concepts indicated that an extremely large portion of the subsonic cruise drag of modern twin-engine fighters is contributed by the aft end of the configuration (approaches 50 percent for some configurations). Careful tailoring of the engine inter-fairings and tail surfaces could prevent excessive aft-end drag. Configuration changes to the initial F-15 design significantly reduced the subsonic cruise drag of the aircraft. Specifically, the ventral fins were removed and the height of the vertical tails was increased to compensate for the resulting loss of directional stability.
http://www.globalsecurity.org/milita.../f-15-lfax.gif
http://www.globalsecurity.org/milita...15-history.htm
И того имеем начало концептуальной разработки 1967. Получение контракта в 1968. Выбор концептуальной модели LFAX-8 произрастающей из LFAX-4 (F-111)
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