Methods of supersonic aircraft preliminary squares graph formation
Aviation technics and technology
2. Experimental design Bureau named after P.O. Sukhoi, 23A, Polikarpova str., Moscow, 125284, Russia
This article describes the approach used by designers in determining fighter aircraft geometric shape. In determining the geometric shape, the boundary conditions are the aircraft squares graphs. The aircraft squares graphs formation takes place on the basis of the classical formula for the body «Sears-Haack.» Further transformation of the aircraft squares graphs is carried out taking into account the changes in statistics. The volume and the squares graphs of bearing surfaces are determined separately.
Designer needs to determine the so-called «Layout area» to form the aircraft geometric shape. At the initial stage of the geometric shape formation «Layout area» is a planned aircraft projection, which determines the airplane carrying capacity, and the squares graphs, defined the sheer aircraft volume and the aerodynamic drag wave increase.
Aircraft planned projection formation traditionally is the first parameter taken in to account for the geometric shape development (after design parameters preliminary determination), is directly related to the aircraft squares graphs and vice versa. Furthermore, the importance of squares graphs defined for the designer illustrates the distribution layout volume in the theoretical layout loop of plane and, thereby, enables the analysis of rational distribution.
Squares graphs (at this stage) is the source of the parameters describing the «necessary» square cross sections. The term «necessary» means that supersonic front aircraft geometric shape formation should follow certain patterns of cross-sectional areas distribution along its length.
In this paper we use two concepts: «aerodynamic» squares graph, and a «full» squares graph.
Under the first refers the cross-sectional and exclude «channels» graph (the volume occupied by the air intakes and engines).
Under the «full» squares graph means aircraft cross-sectional areas graph, built with the contribution of all components, including ducts and nozzles.
After defining the squares graph main parameters, it is necessary to define the parameters of its shape, namely the location of mid-section along the aircraft length. For the Sears-Haack’s body it is characteristically a mid-section location at mid-length, and for modern supersonic aircraft is typical shift back of mid-section. This is due to purely as the layout features, as well as with typical supersonic flight speeds at cruising. That makes it necessary to provide a minimum gain of the wave drag at these flight speeds, and displacement (from the middle of the aircraft length) of mid-section position.
Keywords:shape, jet, volume, midship, layout, designing
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