Abstract:
A system and method for adjusting a location of a center of gravity of an aircraft relative to a center of lift of a wing of the aircraft. In one innovative aspect, a modular spar tunnel mold is provided and configured to be detachably fixed at a selected location within a main mold for a fuselage portion of the aircraft.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to aircraft manufacturing systems and methods. In particular, but not by way of limitation, the present invention relates to systems and methods for shifting, or repositioning, an aircraft fuselage on a wing during aircraft development or manufacture to adjust the center of gravity (CG) location of a resulting aircraft.  
         BACKGROUND OF THE INVENTION  
         [0002]    In the avionics field, proper positioning of the center of gravity (CG) of an aircraft is essential. For example, if the CG of an aircraft is positioned too far forward of the aerodynamic center of the wing, a pilot can experience significant difficulty in attempting to control the aircraft during flight. Similarly, if the CG of the aircraft is positioned to far aft of the aerodynamic center of the wing, the aircraft will become inherently unstable.  
           [0003]    Stated somewhat differently, in order to maintain proper stability of an aircraft, the CG should not under any condition of fuel loading, passenger loading, cargo loading, or any other type of loading be positioned rearward of a rear stability limit. And, in order to maintain proper control, for example, during take offs and landings, the CG should never be positioned forward of the aerodynamic limit of the aircraft.  
           [0004]    One, thus, can readily understand that, when design criteria are altered for an aircraft, such as when a different passenger seating configuration is selected or a different propulsion system is selected, it can become necessary to shift, or reposition, the fuselage of an aircraft on its wing. And, where conventional aircraft manufacturing systems and techniques are employed, this can result in a complete redesign of the aircraft and the tools used to build or assemble it.  
           [0005]    Those skilled in the art of aircraft manufacture and design will appreciate, therefore, that a need exists for an improved method of repositioning a fuselage on a wing, when significant design changes are encountered in an aircraft development process.  
         SUMMARY OF THE INVENTION  
         [0006]    Exemplary embodiments of the present invention that are shown in the drawings are summarized below. These and other embodiments are more fully described in the Detailed Description section. It is to be understood, however, that there is no intention to limit the invention to the forms described in this Summary of the Invention or in the Detailed Description. One skilled in the art can recognize that there are numerous modifications, equivalents and alternative constructions that fall within the spirit and scope of the invention as expressed in the claims.  
           [0007]    In one particularly innovative aspect, the present invention is directed to systems and methods for adjusting the location of the CG of an aircraft by shifting, or repositioning, the fuselage of an aircraft on its wing without requiring a complete retooling of the fuselage and wing assembly.  
           [0008]    In one presently preferred embodiment, a modular spar tunnel is provided within a mold for constructing a fuselage section of an aircraft. The modular spar tunnel is configured to engage, or be mounted within, a main mold for a portion (typically the right or left side) of the fuselage of the aircraft. In this fashion, the spar tunnel of an aircraft can be shifted forward or rearward within a fuselage section of an aircraft without a major retooling operation, and without modifying other elements or aspects of the aircraft. Thus, if a different propulsion system is selected for an aircraft design, major retooling of the molds used to manufacture the aircraft may not be required.  
           [0009]    In another innovative aspect, the present invention is directed to a method for assembling a fuselage of an aircraft using a multi-component molding and composite manufacturing process. A modular spar tunnel of the type described above is utilized to locate a spar tunnel within a fuselage of an aircraft, and layers of composite fiber are laid up within the mold, and thereafter cured, to form a portion of the fuselage of the aircraft. Using methods in accordance with the present invention, it is possible to accommodate significant design variations between aircraft without engaging in a major retooling process and incurring the costs associated with such retooling.  
           [0010]    As previously stated, the above-described embodiments and implementations are for illustration purposes only. Numerous other embodiments, implementations, and details of the invention are easily recognized by those of skill in the art from the following descriptions and claims.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    Various objects and advantages and a more complete understanding of the present invention are apparent and more readily appreciated by reference to the following Detailed Description and to the appended claims when taken in conjunction with the accompanying Drawings wherein:  
         [0012]    [0012]FIG. 1 is an illustration of a mold incorporating a modular spar tunnel in accordance with a preferred form of the present invention.  
         [0013]    [0013]FIG. 2 is an enlarged illustration of a modular spar tunnel in accordance with a preferred form of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0014]    Referring now to the drawings, where like or similar elements are designated with identical reference numerals throughout the several views, and referring in particular to FIG. 1, a modular spar tunnel tool  10  is shown mounted within a mold  20  for a portion of an airplane fuselage. A preferred form of the modular spar tunnel tool is shown in FIG. 2.  
         [0015]    As shown in the drawings, the mold  20  has provided thereon a plurality of raised members  22  that preferably are designed to engage a corresponding set of recesses  12  provided within the modular spar tunnel tool  10 . Thus, by adjusting the position of the modular spar tunnel tool  10  within the mold  20 , the location of the spar tunnel of an aircraft can be readily adjusted to adjust for other design criteria, such as modifications to a seating arrangement or substitution of a propulsion system.  
         [0016]    Turning now in detail to FIG. 2, the modular spar tunnel tool  10  preferably is manufactured from composite materials, such as carbon fiber or KEVLAR™, but those skilled in the art will understand that the modular spar tunnel tool  10  also can be manufactured from metal, such as aluminum, or any other material, so long as the material can withstand the conditions present in a typical composite curing process.  
         [0017]    The modular spar tunnel tool  10  preferably includes a pair of raised sections  14 ( a ) and  14 ( b ) for defining the spar tunnel of an aircraft fuselage and a mounting plate  16  for engaging the mold  20  for the main aircraft fuselage. As noted above, the mounting plate  16  preferably has a plurality of recesses  12  formed therein for receiving a corresponding set of raised or protruding members  22  provided on the mold  22 . In a currently preferred form, the recesses  12  may have a semi-spherical shape corresponding to a semi-spherical shape of the raised or protruding members  22 .  
         [0018]    Those skilled in the art, however, will appreciate that numerous other methodologies can be employed for positioning the modular spar tunnel tool within the main mold  20 , and that the present invention should not be limited to the particular embodiments described herein. For example, in alternative embodiments, the raised or protruding members  22  can take the form of pins, and the recesses  12  can take the form of a plurality of holes provided in the mounting plate  16  of the modular spar tunnel tool  10 .  
         [0019]    Those skilled in the art also will appreciate that the main body  18  (including the raised sections  14 ( a ) and  14 ( b )) and the mounting plate  16  of the modular spar tunnel tool  10  can be manufactured as a single unit or, alternatively, the various portions of the modular spar tunnel tool  10  can be manufactured separately and combined prior to being placed within the main mold  20 .  
         [0020]    Finally, those skilled in the art will appreciate that, where a modular spar tunnel tool  10  in accordance with various forms of the present invention is used to manufacture a series of aircraft, adjustments to the spar location of the aircraft can be made relatively easily without significant retooling of the manufacturing process. This allows aircraft manufacturers using a modular spar tunnel tool  10  in accordance with the present invention to much more quickly respond to customer design change requests and other design and development issues that may arise during the creation of a line of aircraft.  
         [0021]    In conclusion, the present invention provides, among other things, an improved system and method for manufacturing a series of aircraft and, in particular, an improved system and method for adjusting the CG and/or spar tunnel location within a series of aircraft. Those skilled in the art can readily recognize that numerous variations and substitutions may be made in the invention, its use and its configuration to achieve substantially the same results as achieved by the embodiments described herein. Accordingly, there is no intention to limit the invention to the disclosed exemplary forms. Many variations, modifications and alternative constructions fall within the scope and spirit of the disclosed invention as expressed in the claims.