WO1986003172A1

WO1986003172A1 - Graduated aircraft design and construction method

Info

Publication number: WO1986003172A1
Application number: PCT/US1985/002284
Authority: WO
Inventors: William W. Fox
Original assignee: Fox Brothers Limited Partnership
Priority date: 1984-11-23
Filing date: 1985-11-22
Publication date: 1986-06-05
Also published as: IL77125A0; AU5207386A; JPS62501408A; EP0202324A1; EP0202324A4; BR8606990A; BR8507073A

Abstract

A design and construction method for a graduated series of aircraft of various sizes of which development costs are minimized by maintaining a consistant scale configuration from model to model, and production costs are minimized through maximum reuse of molds, jigs, templates or other tooling for the manufacturing of detail parts, subassemblies and components of the airframes. Full implementation of the design and construction method is made possible through the use of "state-of-the-art" composite materials, which have sufficient bending and torsional stifness to permit the construction of a aft-mounted forward-swept wing (12) of high aspect ratio without a severe weight penalty. The forward-swept, high-aspect-ratio wing, in turn, allows the construction of an airframe configuration having, in addition to the forward-swept main wing airfoil (12), a canard airfoil (11), a aft-fuselage-mounted vertical airfoil (13) and propulsion system (6A-6H). Elimination of main-wing attachment points from the center fuselage section facilitates the design and manufacture of that section and allows the use of fuselage nose (81A-81H) and tail sections (82A-82D and 83E-83H) having a high degree of commonality between models. Main wing, canard and vertical airfoild for all models in the series are produced from a subset of molds, jigs, templates or other tooling which are shared to a significant degree by all models in the series.

Description

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 -6-

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 -8*

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 ,

^*!_. .. -- . ~ -^x ; - j ' 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-

_*

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.

S P ' u 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.

Claims

-I -

CLAIMS 1. A methoα for constructing a particular model of a size-graduated series of aircraft comprising the following steps: production of a fuselage nose cone unique to said particular model from a first set of tooling means common to all models in said series, said first set of tooling means having ooth tixed and variable parameters; production of a fuselage tail section unique ^■ to 'said particular model from a second set of

■+ tooling means common to all models in said series, said second set of tooling means having both fixed and variable parameters; production of tapered canard airfoil unique to said particular model from a third set of tooling means having Doth fixed and variable parameters; production of a tapered main wing airfoil unique to said particular model from a fourth set of tooling means having both fixed and variable parameters; production of a tapered vertical airfoil unique to said particular model from a fifth set of tooling means having both fixed and variable -1^*7-

parameters; production of a fuselage center section suited to the mission requirements of said model; interfacing said fuselage nose cone to the forward end of said fuselage center section; interfacing said fuselage tail section to the aft end of said fuselage center section; mounting said canard airfoils to said nose cone; mounting said wing to said tail section;

10 mounting said vertical airfoil to said tail section; and , affixing a means of propulsion of appropriate power for said model to said tail section.

^

2. The method for constructing of Claim 1 wherein the fixed parameters of said first set of tooling means comprise the size and curvature imparted to the outer surface of said nose cone, and the variable parameters comprise means for

20 reinforcement of load bearing areas of said fuselage nose cone commensurate for the loading of said particular model.

3. The method for constructing of Claim 1 wherein -li¬

the fixed parameters of said second set of tooling means comprise the size and curvature imparted to the outer surface of said fuselage tail section, and the variable parameters comprise means for reinforcement of load bearing areas of said fuselage. tail section commensurate for the loading of said particular model.

4. The method for constructing of Claim 1 wherein said third set of tooling means is utilizeable for producing a universal canard airfoil having a root

, chord identical in size to that of the canard airfoil of the largest model in said series and a tip chord identical in size to that of the canard airfoil of the smallest model in said series.

5. The method for constructing of Claim 4 wherein the fixed parameters of said third set of tooling means comprise impartation of fixed curvature imparted to the outer surface of said canard airfoil, and the variable parameters comprise adjustability of the strength of load-carrying elements and adjustability of root chord size and tip chord size of said canard airfoil, with a -;<? ^■

consequent adjustability of the span thereof.

6. The method for constructing of Claim 5 wherein said third set of tooling means comprises separate sets of tooling means for fixed and oveable sections of said canard airfoil.

7. The method for constructing of Claim 1 wherein said fourth set of tooling means is utilizeable for producing a universal main wing airfoil having a root chord identical in size to that of the main wing airfoil of the largest model in said * series

** and a tip chord identical in size to that of the main wing airfoil of the smallest model in said series.

8. The method for constructing of Claim 7 wherein the fixed parameters of said fourth set of tooling means comprise impartation of fixed curvature to the outer surface of said main wing airfoil, and the variable parameters comprise adjustability of the strength of load-carrying elements and adjustability of root chord size and tip chord size of said main wing airfoil, with a consequent adjustability of its span.

9. The method for constructing of Claim 8 wherein said fourth set of tooling means comprises separate sets of tooling means for fixed and moveable sections of said main wing airfoil.

10. The method for constructing of Claim 1 wherein said fifth set of tooling means is utilizeable for producing a universal vertical airfoil having a root chord identical in size to that of the vertical airfoil of_ the largest model in said series and a tip chord identical in size to that of the vertical airfoil of the smallest model in said series.

11. The method for constructing of Claim 10 wherein the fixed parameters of said fifth set of tooling means comprise impartation of fixed curvature to the outer surface of said vertical airfoil, and the variable parameters comprise adjustability of the strength of load-carrying elements and adjustability of root chord size and tip chord size of said vertical airfoil, with a

iUBSTlTUTESHEET consequent adjustability of the height thereof.

12. The method for constructing of Claim 11 wherein said fourth set of tooling means comprises separate sets of tooling means for fixed and moveable sections of said vertical airfoil.

13. A method for constructing one of a size- graduated series of airfoils, straight tapered in width and thickness, from a set of mold, jigs, templates or other tooling utilizeable for producing a universal airfoil having a, root chord identical in size to that of the largest airfoil in said series and a tip chord identical in size to that of the smallest airfoil in said series.

14. The method for constructing of Claim 13 wherein said set of tooling means have both fixed and variable parameters.

15. The method for constructing of Claim 14 wherein said fixed parameters comprise impartation of fixed curvature to the outer surface of said airfoil, and said variable parameters comprise -s«r

adjustability of the strength of load-carrying elements and adjustability of root chord size and tip chord size of said airfoil, with a consequent adjustability of the span thereof.

16. A method for constructing one of a size- graduated series of tapered airfoils from a set of tooling means utilizeable for producing a universal airfoil having a root chord identical in size to that of the largest airfoil in said series and a tip chord identical in size to that of the smallest airfoil in saiή series.

17. The method for constructing of Claim 16 wherein said set of tooling means have both fixed and variable, parameters.

18. The method for constructing of Claim 17 wherein said fixed parameters comprise impartation of fixed curvature to the outer surface of said airfoil, and said variable parameters comprise adjustability of the strength of load-carrying elements and adjustability of root chord size and tip chord size of said airfoil, with a consequent adjustability of the span thereof.

19. The method for constructing of Claim 1 wherein said first set ot tooling means comprises a set of molds.

20. The method for constructing of Claim 1 wherein said first set of tooling means comprises a set of jigs.

21. The method for constructing of Claim 1 wherein said first set of tooling means comprises a set of templates.

22. The method for constructing of Claim 1 wherein said second set of tooling means comprises a set of molds.

23. The method for constructing of Claim 1 wherein said second set of tooling means comprises a set of jigs.

24. The method for constructing of Claim 1 wherein said second set of tooling means comprises a set of - -

templates .

25. The method for constructing of Claim 1 wherein said third set of tooling means comprises a set of molds.

26. The method for constructing of Claim 1 wherein said third set of tooling means comprises a set of jigs.

27. The method of constructing of Claim 1 wherein said third set ot tooling means comprises a set of templates.

28. The method of constructing of Claim 1 wherein said fourth set of tooling means comprises a set of molds.

29. The method of constructing of Claim 1 wherein said fourth set of tooling means comprises a set of jigs.

30. The method of constructing of Claim 1 wherein said fourth set of tooling means comprises a set of templates.

31. The method of constructing of Claim 1 wherein said fifth set or tooling means comprises a set of molds.

32. The method of constructing of Claim 1 wherein said fifth set of tooling means comprises a set of jigs.

33. The method of constructing of Claim 1. wherein said fifth set of tooling means comprises a set of templates.