GRADUATED AIRCRAFT DESIGN AND CONSTRUCTION METHOD FIELD OF THE INVENTION
The present invention relates to design and construction methods for aircraft, and especially to those aimed at building a size-graduated series of aircraft having a consistent scale relationship between aircraft of different sizes with a minimum of development and production costs.
BACKGROUND OF THE INVENTION
The numerous models offered in the civil aviation market by the various manufacturers have traditionally been point designs, with a wide variety of engine, avionics and equipment options offered around a given airframe, which has remained in production for many years with little or no technological improvement. This traditional design approach has required an extensive, hence costly, development and certification program to eliminate flaws from a given design in order to assure its airworthiness as required by the FAA rules and regulations. The point design approach for each model in a product line of civil aviation aircraft also requires a completely unique set of production tooling for the manufacture of each model, allowing
a manufacturer little opportunity to reduce manufacturing costs through the partial or complete reuse of molds, jigs, templates or other tooling in the manufacture of other models of different size within his product line.
A search by the applicant reveals no relevant prior art within the field of aviation related to the present invention. In U.S. patent No. 4,417,708, inventor Rosario 0. Negri teaches a design system for an aircraft that allows wings of various different planforms . to be .mounted interchangeably on a common fuselage. It j3iffers significantly from the graduated design and construction method disclosed herein in that no series of models of graduated size are envisioned. Bertram P. . Scott in U.S. patent No. 1,524,059 teaches the use of a tapered template for making a series of organ pipes, each of which is largely a scale replica of the next. In U.S. patent No. 3,545,085, Halbert C. Stewart teaches a scale pattern method for shaping and hanging drapery material. As far as can be ascertained, no like method has ever been applied to the design and construction of a series of aircraft models.
Other than in the field of avionics, the past forty years have seen precious little new technology applied to the design, safety and manufacture of civil aviation aircraft. Although the use of composite materials is revolutionizing the single-point design and construction of military and homebuilt aircraft, civil aviation has remained largely stagnant. As civil aviation aircraft prices continue to escalate and the number of aircraft sold continues to drop, the future of civil aviation manufacturing remains disquietingly uncertain. A* technological revolution in the design and manufacture of civil aviation aircraft could dispell that gloom.
SUMMARY OF THE INVENTION
The first object of the present invention is to reduce aircraft development and certification costs by utilizing a graduated aircraft design approach to produce a series of individual point designs for a wide variety of different-size aircraft that all look alike, fly alike and perform alike because each model is a scale equivalent of other models in the series with
respect to airfoil shape and configuration. Models of a series utilize unique cabin arrangements and propulsion systems selected to match the specific mission requirements for the particular model. The second object of the invention is to reduce aircraft manufacturing costs by maximizing reuseability of molds, jigs, templates, or other tooling for the production of airfoils and fuselage nose and tail cones between the various models of a size-graduated series.
For maximum fulfillment of the aforestated objectives, it is essential to eliminate the mounting of airfoils and propulsion system from the aircraft's center fuselage section. Only with a high-aspect-ratio, aft-mounted forward-swept wing is such a configuration possible. Not until only relatively recently has it been possible to construct a forward-swept wing which will withstand the torsional and bending loads to which such a wing configuration is subjected without incurring a substantial weight penalty. Developments in composite materials have made the forward-swept wing design feasible. As strong or stronger than most metals, composite materials have an
additiional advantage. They are stiff only in the direction of fiber orientation. Hence, a composite structure can be tailored to bend or to resist bending in a specific direction, or, by crisscrossing fibers in the matrix, multi or omni¬ directional stiffness can be achieved.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1A is a top plan view of the ideal configuration;
Figure IB . is a side elevational view of the ideal configuration;
Figure 1C is a front elevational view of the ideal configuration; Figure 2 is a graph of wing area vs. wing span for a wing with an aspect ratio of 10. Points on the graph indicate wing area and span for various models within the illustrated series of aircraft;
Figure 3 is a top plan view showing a mold for the production of the main wing airfoil semi-span of any model within the graduated series of aircraft;
Figure 4 is a side elevational view showing the mold for the production of the vertical airfoil
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of any model within the graduated series of aircraft;
Figure 5 is a top plan view showing the mold for the production of the canard airfoil semi-span of any model within the graduated series of aircraft;
Figures 6A through 6H are top plan views of the tail section of different models showing the mounting of various types of propulsion systems; Figures 7A through 7H ar.e elevational front views of the fuselages for the different-sized models within a suggested series of aircraft, in order of ascending size;
Figures 8A through 8H are elevational side views of the different sized models within a suggested series of aircraft whose fuselages are shown in Figures 7A through 7H; and
Figures 9ft through 9H are perspective views of each of the conceptual point designs, corresponding respectively to the aircraft of Figures 8A through
8H.
DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
The ideal configuration of Fig. 1, characterized by an aft-swept, forward mounted canard 11 and aft-fuselage-mounted forward-swept wing 12 and vertical airfoil 13 allows full implementation of the graduated design and construction techniques which comprise the instant invention. , In addition, . there are several significant aerodynamic and safety advantages which
* are' inherent in this configuration.
First, the forward-swept wing has several aerodynamic advantages well-known in the art.
Adverse yaw while banking, as well as the tendency to roll while slipping are both greatly reduced or altogether eliminated.
Second, the forward-swept wing combined with aft-mounted power make possible the exclusion of all fuel and fuel lines from the crew and passenger fuselage envelope.
Third, it is well known in the art that canards (lifting surfaces mounted forward of the main wing) offer significant advantages over tail- mounted stabilizers. The canard 11 of Figure 1
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will eliminate "deep stall" problems because it is never in the wake of the main wing airfoil- At high angles of attack, the canard creates high- energy vortices that wash over the center section of the main wing, delaying boundary separation in airflow over that section. therefore delaying a stall of that section. Additionally, if the canard's fixed angle of attack is greater than that of the aft-mounted wing, the canard will stall first. causing the nose of the aircraft to drop before the aft-mounted wing reaches its critical angle of attack. Since low-altitude stalls are .the single largest cause of fatal civil aviation crashes. ah aircraft utilizing a canard-type. horizontal surface offers an important safety advantage over aircraft of conventional design.
Fourth. the ideal configuration of Fiqure 1 is especially suited for far-aft-mounted engines, with maximum safety in the event of a powerplant- related fire- since flames and other hot gasses cannot impinge directly on the primary aircraft structure, but are dissipated in the free airstream.
As heretofore stated, the high-aspect-ratio ,
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forward-swept main wing 12 must be constructed of "state-of-the-art" composite materials. However, construction of the entire aircraft from composite materials offers the advantages of greatly reduced weight and drag as compared to a conventionally constructed-aircraft of comparable size utilizing aluminum structure. This inherent strength per unit of weight for composite materials permits the construction of a "high-G" cabin structure for
> improved crash-worthiness without an excessive weight penalty.
The forward-swept, aft-mounted wing 12 of the ideal configuration of Fig. 1 can accomodate leading edge flaps or slats 14 and full-span flaps 15 to improve the coefficient of lift for shorter takeoff and landings if the mission requirements of a specific model so dictate. Lateral control can be achieved through the use of spoilers 16 or by differential use of the wing flaps 15. The canard airfoil 11 , mounted on the forward fuselage, provides the necessary longitudinal stability and control. Longitudinal control can be obtained by means of a conventional elevator 17 or by movement of the entire surface
as a slab. Longitudinal trim can be achieved by means of a conventional trim tab 18 or by trimming the stabilizer surface.
The vertical airfoil 13 mounted on the aft-end of the fuselage provides the necessary directional stability and control. Directional control is achieved through the use of a conventional rudder 19 and directional trim is achieved by means of a conventional trim tab 20. The graduated design method is illustrated in
Fig. 2 with a graph of wing area vs. wing span for an aspect ratio of ten. Points 21, 22, 23 and 24 represent proposed wing areas and wing spans for single-engine models of two, four, six and eight-place capacity, respectively. Points 25, 26, 27 and 28 represent proposed wing areas and wing spans for twin-engine models of eight, ten, twelve and fourteen-place capacity, respectively.
The high degree of reuseability of the manufacturing molds for the wing, horizontal and vertical surfaces for the eight specific models chosen to illustrate the graduated design and consruction method is shown in Figures 3, 4 and
5, respectively. Each mold is capable of producing a universal airfoil 31, 41 and 51, which would be the length of the entire mold, and which accomodates all models in the size graduated series. The surfaces for the two-place airplane 32, 42 and 52 are those with the smallest tip and root chords. The surfaces for the four-place airplane 33, 43 and 53 do not use a small portion of the tip of the two-place airplane 'surfaces 34, 44 and 54. In addition, the surfaces"'for the four-place airplane are lengthened and enlarged at the inboard end to obtain the desired four-place airplane root chord 35, 45 and 55. This step by step process is repeated in a like manner for each successive model in the entire product line. The degree of reuseability of the manufacturing molds, jigs, templates or other tooling for airfoil surfaces is dictated by the magnitude of step increase in size from one model to the next. As the length and width of an airfoil increase, required design loads are also increased. To handle the additional forces to which the larger airfoil structure will be subject, it will be necessary, in the case of an airfoil manufactured
of composite materials, to increase the reinforcing material in the composite layup for the airfoil structures. In the case of airfoils manufactured of conventional materials, the cross sectional area of the load-supporting elements such as spars or stressed skin will require augmentation over the length of the span- This graduated scale construction method applies to any tapered surface. without regard to its sweep angle-
Although the airfoils of Figures 3. 4 and 5 are illustrated as solid structures, the method as described applies to all of the elements thereof, such as leading edges, spars, skin panels, moveable surfaces and other necessary components-
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Hence- a canard, main wing, or vertical airfoil could be constructed from several sets of universal molds, jigs, templates or other tooling.
Various propulsion systems may be conveniently installed on the ideal configuration of Fig. 1- as shown in Figures 6A through 6H, to meet the specific mission requirements for each model in a size-graduated series of aircraft- The power plants for the single-engine aircraft are housed in a nacelle that is part of the fuselage tail cone.
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Power plants for twin-engine applications are housed in nacelles that are attached to the aft-end of the fuselage tail cone by means of stub pylons, thus minimizing assymetric thrust geometry. In the case of propeller driven aircraft, the propeller diameter is reduced to between 75 and 80 percent of that of conventional aircraft, with the propeller being housed in a shroud for decreased noise and vibration levels and improved efficiency. As engine power output increases, the width and number of blades per propeller are increased while the diameter of the propeller remains constant. Figures 6A and 6B illustrate single and twin mountings of conventional piston engines, respectively. Figures 6C and 6D illustrate single and twin mountings of turbo-prop engines, respectively. Figures 6E and 6F illustrate single and twin mountings of fan-jet engines, respectively. Figures 6G and 6H illustrate single and twin mountings of future prop-fan engines, respectively.
Figures 7A through 7H are elevational front views of the fuselages for the eight models chosen to illustrate the graduated design and
construction method, in order of ascending size- Figures 8A through 8H are elvational side views of the same eight models in the same ascending order. Figures 9A through 9H are perspective views of the same eight models in the same ascending order.
The high degree of commonality between the fuselages of different models is significant. The eight aircraft utilize nose cones 81A through 81H fabricated in identical molds, with additional reinforcement added for larger models in areas of increased stress. The four single-engine aircraft utilize fuselage tail sections 82A through 82D fabricated in a common mold, with additional composite material reinforcement added for larger models in areas of increased stress. The four twin-engine aircraft utilize fuselage tail sections 83E through 83H fabricated in a common mold, with additional composite material reinforcement added for larger models in the areas of increased stress. The twin engine aircraft all utilize fuselage cockpit sections 84E through 84H fabricated in a common mold. Only the passenger- carrying fuselage sections vary significantly from
one model to the next, increasing both in width and length as seating capacity increases.
Although the fuselage is depicted as comprising three sections in Figures 8A through 8H, the process of manufacturing such sections could just as easily be broken down into the manufacture of smaller subunits such as longerons, stringers, frames, skin panels, etc. which could later be used to build an entire fuselage section. While the preferred embodiment- of the invention has been disclosed, other embodiments may be devised and modifications made within the spirit of the invention and within the scope of the appended claims.