Look, Lance G. (Traverse City, MI)
Erickson, David G. (Williamsburg, MI)

04/886322

05/30/1972

12/18/1969

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Hitco (Gardena, CA)

244/218

B64C3/56; B64C3/00; B64C3/54

244/43,45R,46,49,42DA,35R,123,124

3292881

Aircraft with variable geometry

December 1966

Ricard

Buchler, Milton

Rutledge, Carl A.

What is claimed is

1. A deployable aerodynamic structure comprising:

2. The invention as set forth in claim 1 above, wherein said elements are mounted along an axis substantially normal to the chord of the airfoil and where said elements define paired upper and lower aerodynamic surfaces comprising a tapered aerodynamic structure when deployed.

3. The invention as set forth in claim 2 above, wherein said elements assume nesting relation when stowed, and wherein said upper and lower aerodynamic surfaces are substantially continuous in both the span and chord directions throughout the area of said variable area portion when deployed.

4. A deployable aerodynamic structure comprising:

5. The invention as set forth in claim 4 above, wherein said aerodynamic surface elements comprise rib elements having at least upper and lower aerodynamic surfaces, and including a coupling element pivotally coupled to each of said rib elements at spaced points from said body portion, and wherein said rib elements are pivotally coupled internally to said body portion and coupling element.

6. The invention as set forth in claim 5 above, wherein said body portion lies along a first axis, wherein said upper and lower aerodynamic surfaces of said rib elements abut to define substantially continuous aerodynamic surfaces when in the deployed position, and wherein said coupling element lies substantially parallel to said first axis.

7. The invention as set forth in claim 6 above, wherein said body portion and said variable area portions define continuations of an airfoil when said variable area portion is deployed.

8. A deployable airfoil structure comprising:

9. A variable area airfoil structure comprising:

10. A variable area airfoil structure comprising:

11. The invention as set forth in claim 10 above, wherein said rib elements are regularly spaced relative to said spar segment and said pivotally coupled means, so as to define a movable parallelogram linkage, and wherein said rib elements are of generally [ -shaped cross section, with the upper and lower airfoil surfaces being of sufficient width relative to the spacing between them to be in abutting relation when in the deployed position, such that said trailing edge segment means is substantially continuous in both span and chord directions when deployed, and wherein each rib element pivots into the open side of the [ -shaped cross section of the next adjacent element when moving toward the stowed position.

12. The invention as set forth in claim 11 above, wherein said spar segment comprises a leading edge box beam airfoil structure having a trailing edge skirt, wherein said rib elements are pivotally mounted within said trailing edge skirt and substantially retracted within said skirt portion when in the stowed portion, and wherein said pivotally coupled means comprises a trailing edge insert member of fixed configuration providing a trailing edge surface for the airfoil and disposed at least partially between said rib elements at the trailing edges thereof.

13. A deployable airfoil structure comprising:

14. The invention as set forth in claim 13 above, wherein the means for receiving the next outboard section comprises channel means for receiving the section with a sliding fit, and including means at least partially extending through said sections for sliding said airfoil sections relative to each other, and means for deploying said variable area portion.

15. A variable area airfoil structure comprising:

16. The invention as set forth in claim 15 above, wherein said sections preceeding outwardly have successively shorter fixed geometry spar segment means and successively longer deployable means in the chord dimension, and wherein said structure further includes, for each section, a plurality of rib elements defining the substantial majority of said deployable portion, and edge insert means pivotally coupled to said rib elements at the opposite ends from said spar segment means.

17. A variable area airfoil structure comprising:

18. The invention as set forth in claim 17 above, wherein said means for deploying and compacting comprises cable and sheave means disposed within and along the apertures of the spar segments, and wherein said means for deploying the deployable segments includes further cable and sheave means within and along the apertures of the spar segments.

19. A variable area airfoil structure which can be compacted and expanded in both the span and chord dimensions, comprising:

20. A variable area airfoil structure which can be compacted and expanded in both the span and chord dimensions comprising:

21. The invention as set forth in claim 20 above, including means disposed between each pair of sections and mounted in the outboard end of one section and at the inboard end of the adjacent section for locking the same in overlapping relationship.

22. The invention as set forth in claim 21 above, wherein said spar segment means for the successive sections register with a sliding fit, and wherein said pivotable segment means include an edge insert pivotally coupled to the segments thereof, such that the spar segment means, the edge insert and the segments thereof provide a pivotable parallelogram structure.

23. The invention as set forth in claim 20 above, wherein said airfoil structure comprises, when deployed, an aircraft wing, and wherein the center and outboard sections include spar segments having grooves and lands extending along the span direction, and being in mating relationship, and further including locking means for coupling each adjacent pair of sections at a full extension position.

24. The invention as set forth in claim 23 above, and wherein the trailing edge segment of the outboard section and the leading edge spar segment provide a chord dimension of substantially shorter length than the adjacent sections, and wherein in addition said trailing edge segment includes aileron support means mounted in the trailing edge thereof, and said airfoil structure includes deployable aileron means mounted in said aileron support means.

25. The invention as set forth in claim 24 above, wherein said deployable aileron means comprise a plurality of ribs pivotally mounted in said aileron support means, and a trailing edge insert pivotally coupled to each of said ribs to define therewith and with said aileron support means a movable parallelogram structure pivotable relative to said outboard section.

BACKGROUND OF THE INVENTION

This invention relates to variable area or geometry aerodynamic or airfoil structures, and more particularly to airfoils capable of variation between compacted, high density configurations and fully deployed, aerodynamically functional configurations.

Variable area of geometry airfoils are utilized in a number of aerodynamic vehicles, principally for the purposes of more efficient stowage by virtue of compaction and of improvement of aerodynamic efficiency under different flight conditions. It is known, for example, to provide telescoping airfoils that may be extended spanwise from a compacted stowage configuration for flight purposes. It is also known to employ various forms of pivoted and expandable wing configurations for purposes of stowage or variable geometry operation. Apart from the familiar folding wing structures used on carrier-based aircraft, few of such structures have been proven practical. To meet modern flight conditions such designs must satisfy extreme structural, weight and operative limitations. Past variable geometry wing configurations have generally imposed excessive weight penalties or afforded inadequate structural properties, or both. Helicopter rotor blades are subject to particularly stringent loading and operative requirements which have largely prohibited the use of existing designs of deployable structures. A rotor airfoil must also remain aerodynamically clean when deployed and have an adequate though limited operative life. Further with regard to rotor blades, which are required to operate near the threshold of performance limit and which are subject to severe vibrations, factors such as system resonances and other dynamic properties can become of great importance. Static stresses at rest are entirely different from static and dynamic stresses under different conditions of operation. Because of the length of a rotor blade, for example, starting the rotor at high forward speed may pass the blade through a critical regime in which there is substantial aeroelastic blade divergence due to wide disparities in the lifting forces on different radial segments of the rotor.

With wing and control surface structures, operative life considerations are not as paramount as with rotor blades, but emphasis is necessarily placed on weight factors and aerodynamic properties. As to all variable area or geometry airfoil structures, however, certain common requirements must be met. The airfoil must be aerodynamically clean when extended; the mechanism for deploying the airfoil should not impose a heavy weight penalty; and the structure as a whole should not have substantially greater weight than a conventional fixed design.

Many different types of spoiler and flap mechanisms are known, generally arranged to pivot or shift around an axis or along a plane parallel to the span of an airfoil. Such mechanisms are not well suited for all installations, because some unwanted comprises may be necessary to place the mechanisms where wanted or to integrate them into an airfoil system.

SUMMARY OF THE INVENTION

Objects and purposes of the present invention are met by aerodynamic and airfoil structures incorporating a plurality of hinged upper and lower ribs to define either the leading or the trailing edge portion, or both, of an aerodynamic element. The aerodynamic element is typically an airfoil but may also comprise particular air flow diverting or control surfaces. One end of each of the ribs is hingedly coupled to a fixed spar or base portion of the structure, and may be disposed within a cavity along the fixed portion. A spaced apart point on each of the ribs is pivotally mounted in an insert member, such that the fixed portion, the ribs and the insert form a movable three dimensional parallelogram structure having an internal coupling mechanism. The structure is shiftable between a stowed position in which the ribs are in nested relation, substantially or almost parallel to the longitudinal axis of the fixed portion, and a deployed position in which the upper and lower ribs define aerodynamically clean airfoil surfaces which continue both the chord and the span of the airfoil. In the stowed position the ribs may be incorporated within a cavity of an adjacent spar.

In a specific example of a device in accordance with the invention, an airfoil body which is deployable in both the span and chord directions may be arranged as either a wing or a rotor blade. The body comprises a number of telescoping sections, each of which comprises a spar segment of fixed geometry and at least one edge segment (in the present specific example the trailing edge only) of extendible nature. The sections have fixed geometry spars of successively shorter chord lengths, with interior channels within the spars for receiving both the next outboard spar and the compacted trailing edge segment. The extendible trailing edge segments are successively longer in the chord dimension, so that the body has an essentially uniform airfoil design along the span. Internal cable and pulley mechanisms operable from a central airframe or rotor hub structure may be disposed within the spar segments for effecting spanwise extension and chordwise deployment.

Stowable constructions for aircraft of the fixed wing type may incorporate stowable ailerons, flaps and other control surfaces if desired. When arranged in a rotor blade configuration, only a short relatively stiff assembly need be accelerated when the rotor is started, and thereafter the sections may be extended outwardly, and the trailing edge structures deployed so that aeroelastic divergence problems are minimized. The weight for a given design does not substantially exceed that of conventional structures. A synchronizing extension control system may be utilized to govern concurrent deployment and compaction of the blades.

Rotor blades which can be extended both in the span and chord dimensions are illustrative of relatively complex system configurations in accordance with the invention. A blade or wing need not be extendible in the span direction, but in an alternative system either or both the leading and trailing edges may be collapsible.

Configurations in accordance with the invention are also of particular utility in conjunction with variable geometry aircraft, including control surfaces and variable wing configurations. In a variable geometry aircraft, for example, a stowable airfoil construction in accordance with the invention may be utilized at the wing root fillets for a predetermined distance along the wing span, to permit shifting of the wing between the extended position and a delta configuration position. Alternatively or in addition to the variable geometry wing construction, segments of the tail and other control surfaces may be collapsed into the fuselage of an aircraft for operation at supersonic speeds. Spoiler or flap mechanisms may be mounted to pivot in a plane lying at an angle to the principal plane of an airfoil, thus to introduce a predetermined discontinuity into the aerodynamic shape when extended.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the invention may be had by reference to the accompanying description, taken in conjunction with the appended drawings, in which:

FIG. 1 is a simplified perspective representation of an aircraft employing a deployable airfoil structure in accordance with the invention;

FIG. 2 is a plan view of a deployable wing construction in accordance with the invention;

FIG. 3 is a partial cross-sectional view, taken along the line 3--3 in FIG. 2 and looking in the direction of the appended arrows;

FIG. 4 is a perspective view, somewhat simplified, of the wing of FIG. 2 in a partially deployed state;

FIG. 5 is a fragmentary perspective view of a portion of the wing construction of FIG. 2, showing further details as to deployment of the wing;

FIG. 6 is a plan view of a part of the wing structure of FIG. 2, showing a deployable aileron structure therein in greater detail;

FIG. 7 is a cross-sectional view of the structure of FIG. 6, taken along the line 7--7 in FIG. 6 and looking in the direction of the appended arrows;

FIG. 8 is a simplified perspective view of a part of the structure of FIG. 2, showing a deployment mechanism for extension of the airfoil body to the extended position;

FIG. 9 is a simplified perspective view corresponding to FIG. 8 but showing the wing in the stowed position;

FIG. 10 is a simplified perspective view, partially broken away, of an illustrative rotor blade configuration in accordance with the invention, including a synchronized deployment mechanism;

FIG. 11 is a simplified perspective view corresponding to FIG. 10 but showing the blade configuration in the stowed condition;

FIG. 12 is a plan view of a fragment of a compactable airfoil structure having both leading and trailing edges that are compactable;

FIG. 13 is a cross-sectional view of the arrangement of FIG. 12, taken along the line 13--13 and looking in the direction of the appended arrows;

FIG. 14 is a plan view corresponding to FIG. 12, but showing the structure in the fully stowed state;

FIG. 15 is a cross-sectional view of the arrangement of FIG. 14, taken along the line 15--15 and looking in the direction of the appended arrows;

FIG. 16 is a plan view of an aircraft having variable sweep wings and deployable tail surfaces in accordance with the invention, showing the fully deployed state;

FIG. 17 is a side view of the aircraft as seen in FIG. 16;

FIG. 18 is a plan view of the aircraft of FIG. 16, showing the wings in the delta configuration;

FIG. 19 is a side view of the arrangement of FIG. 18, showing the tail and rudder in a compacted state;

FIG. 20, comprising sectional fragmentary views 20A and 20B shows details of the section locking mechanism that is employed in the structure of FIG. 2;

FIG. 21, comprising sectional views 21A, 21B and 21C, illustrates three successive states of a deployment sequence control mechanism that may be employed in conjunction with the rotor blade system in FIG. 10;

FIG. 22 is a simplified perspective view of a part of a deployable spoiler device in accordance with the invention, showing the spoiler at the deployed position;

FIG. 23 is a simplified perspective view of the device of FIG. 22, showing the spoiler at the stowed position; and

FIG. 24 is a simplified plan view of a deployable airfoil having tapered planform and arranged in accordance with the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

In accordance with the invention, any of a number of different rotary wing vehicles and variable geometry aircraft may be equipped with compactable and deployable variable area aerodynamic and airfoil structures. Although the following specific examples of fixed and rotary wing structures are illustrative of particularly advantageous usages, it will be appreciated that the principles and features of the invention may also be incorporated in other high density deployable systems, such as those that might be used with reentry vehicles, ejection seats and capsules, aerial delivery systems and vertical or short field takeoff and landing systems.

As illustrated in the simplified perspective view of FIG. 1, a relatively small aircraft 10 in the low performance category has deployable wings 12, 13 which, when extended, duplicate a conventional fixed wing airfoil configuration. The wings 12, 13 may also assume a high density stowed configuration in which the wings 12, 13 are compacted in both the span and chord directions to a relatively small area root section which may also be pivoted relative to the fuselage 15. This deployable airfoil structure includes internal mechanisms (not shown in FIG. 1) for deployment, and integral ailerons 17 which are also compactable.

Details of one wing 12 (the other wing 13 being directly complementary) are illustrated in FIGS. 2 and 3, to which reference is now also made. Broadly, the wing 12 comprises, in this example, three telescoping sections from the wing root, namely an inboard section 19, a center section 20 and an outboard section 21. The center and outboard sections 20, 21 telescope into the inboard section 19, which may be pivoted up (also down or back) around a universal joint mechanism 23 at the root. Chordwise deployment and compaction are achieved by pivotable trailing edge segments 24, 25, 26 of successively greater chord lengths from the inboard to the outboard sections 19 to 21 respectively, with the aileron 17 being incorporated in the trailing edge of the outboard section, and also pivotally deployable. The internal deployment mechanisms (discussed in detail below) comprise cable and pulley systems for telescopic extension of the sections 19, 20, 21 and for pivoting deployment of the trailing edge segments 24, 25, 26, these deployment mechanisms being principally contained within the interior structures of the sections 19, 20, 21.

Each of the sections 19, 20, 21 provides a virtually identical airfoil configuration, the chord length and wing thickness decreasing only slightly in proceeding from the inboard to the outboard sections in this particular structure. The interior configurations, however, change substantially in order to incorporate and provide the telescoping and chordwise deployment functions. With reference to the inboard section 19, for example, as best seen in FIG. 3, the section comprises a box beam in the configuration of a D-spar segment 28 of fixed geometry having a shear web 29 lying parallel to the span axis a selected distance from the leading edge, to define an interior channel within which the center and outboard sections 20, 21 may be received. The D-spar segment 28 also includes a trailing edge skirt 31 on both the upper and lower airfoil surfaces. The compactable trailing edge segment 24 comprises a plurality of substantially identical rib elements 33, pivotally mounted at their leading edges within the trailing edge skirt portion 31 of the D-spar segment 28, and pivotally coupled along their trailing edges to a trailing edge insert element 35 which lies parallel to the span axis.

Additional reference is made here to FIGS. 4 and 5. The ribs 33 comprise channel members having generally rectangular C-shaped or [ -shaped cross sections, defining elongated substantially rectangular upper and lower airfoil surfaces 37, 38, respectively, and an interconnecting apertured web 39. When deployed, the upper and lower airfoil surfaces 37, 38 of the ribs 33 lie in parallel, abutting relation along the chord direction to provide smooth continuations of the airfoil back to the trailing edge insert 35. In addition, the airfoil surfaces are in abutment along the span direction in this position, providing a continuous and uninterrupted surface area. When pivoted to a stowed position in which they approach parallelism to the span direction, the ribs are in nesting relation to each other, and substantially enclosed within the trailing edge skirt 31 of the D-spar segment 28. To resist bending moments, the D-spar segment 28 of the inboard section 19 comprises a laminate having outer and inner skins 41, 42 and a honeycomb material interior 43.

The D-spar segments 45, 46 for the center and outboard sections respectively have similar airfoil configurations, but are of successively shorter lengths in the chord dimension and have exterior dimensions registering with a sliding fit within the interior of the next inboard D-spar segment. As shown for the center and outboard D-spar segments 45, 46 in FIG. 3, the airfoil skins may incorporate skin stiffeners and mating clearances. The shear webs 48, 49 for the center and outer sections 20, 21,respectively, are progressively closer to the leading edge, such that the trailing edge segments 25, 26 when pivoted against the associated shear web are of sufficiently small cross section to be received within the interior channel in the adjacent section 19 or 20.

Referring specifically to FIGS. 1, 2 and 5, the trailing edge segments 25, 26 are progressively longer in the chord dimension proceeding outwardly from the inboard section 19 and the ribs of these segments are pivotally mounted within a trailing skirt portion of the associated D-spar segment 45 or 46, and separately pivotally mounted at the opposite end on a trailing edge insert 51 or 52. The trailing edge insert 52 for the outboard section 21 provides a leading edge base support for the aileron 17, which has its own ribs 54 and trailing edge insert 55. Details of the aileron mounting and structure are further shown in FIGS. 6 and 7. The aileron 17 is disposed such as that the ribs 54 are pivotally mounted on one or more shafts 57 that are rotatable in the trailing edge insert 52, to provide control surface action. FIGS. 5 and 6 show that the segments of the aileron 17 pivot oppositely to the other deployable segments in shifting between the deployed and stowed positions.

Each of the pivotally deployable trailing edge segments 24, 25 and 26 and the aileron 17 are arranged to observe certain relationships of construction and operation. With respect to the inboard section 19 and FIGS. 2, 3 and 4 in particular, for example, each rib 33 is mounted to turn about a leading edge pivot point 62, with the pivot points being regularly and equally spaced along the span dimension of the wing 12. Similarly, at the trailing edge insert 35, the adjacent ends of the ribs 33 each are coupled to a different one of a succession of equally and regularly spaced pivot points 64. Therefore, with the two lines of pivot points lying substantially parallel (also substantially parallel to the span direction in this particular example), the ribs 33 and the trailing edge insert 35 cooperate with the D-spar segment 28 to define a movable parallelogram linkage having upper and lower aerodynamic surfaces. Because of the taper of the ribs 33 from the leading edge backward (best seen in FIG. 5), the dimension of one rib 33 at one chord point starts to fit within a slightly larger dimension of the next adjacent rib at a slightly forward chord point as the system pivots to compact from the fully deployed state. This registration or nesting takes place concurrently along the entire series of ribs, such that there is no substantial restriction or binding as the structure is closed (or when opened). The widths of the airfoil surfaces 37, 38 for each rib may be increased or decreased from the relative proportions shown to meet particular strength and density requirements. The interconnecting webs 39 function as structural reinforcement but, as will be evident to those skilled in the art, need not necessarily be utilized.

Relatively simple and economical pivot mechanisms, as best seen in FIGS. 2, 3 and 5, comprise mating hinge shoulder portions 59, 60, 61 for the rib 33 and the D-spar segment 28, respectively. An interior pivot pin 62 extends through the central holes in the aligned hinge shoulder portions 59, 60, 61. At the trailing edge insert, a pivotal coupling is provided by a single eyelet 64 for each rib 33.

It will be apparent that the telescoping and deployable airfoil structure thus far described may be manually extended and stowed, and locked at each extreme position by pins or other suitable conventional locking mechanisms. If such an operative mode is suitable, only a conventional internal cabling system for operating the aileron 17 need be utilized. In the present example, however, the aircraft 10 of FIG. 1 is intended for conditions of operation in which it may be manually stowed for transport or storage, with the added requirement that the wings be readily deployable by mechanical means for flight. The specific example shown therefore includes a first cable and sheave system for telescopic deployment, a second cable and sheave system for pivotal deployment of the trailing edge segments 24, 25, 26, and deployment and control linkages for the ailerons 17. The first cable and sheave mechanism 66 is shown for clarity in simplified form in FIGS. 8 and 9, although the elements utilized are also shown and correspondingly numbered in the views of FIGS. 2 and 3. An extension control cable 68 extends inwardly from the interior of the D-spar segments 28, 45 and 46 to within the fuselage 15 for application of a force by suitable actuator, such as a manually or hydraulically operable drum or linear actuator. A number of rotatable sheaves are mounted on the inside of the D-spar segments within the channels of the D-spar segments 28, 45, 46. The free end of the cable 68 is attached to the inboard end of the outboard section 21. The cable 68 first passes over a turn-around idler sheave 70 mounted at the outboard end of the inboard section 19 and onto an adjacent relatively large diameter sheave 71 rotatably mounted in brackets 72 (FIG. 3 only) at the inboard end of the center section 20. Thereafter, the cable 68 turns around a sheave 74 mounted at the outboard end of the center section 20, with the free end being fixedly held at an end attachment 77 such as a pin at the inboard end of outboard section 21. In comparison of FIGS. 8 and 9, it is seen that shortening of the cable 68 by retraction into the aircraft acts to close the distance between sheaves 70 and 71 and between sheave 74 and the end attachment 77. Consequently, the center and outboard sections move outwardly toward limit and locking positions.

An exemplary cable assembly for controlling trailing edge segment deployment is best seen in FIG. 2. A deployment control cable 79 within the inboard and center sections 19, 20, for example, is utilized to deploy the trailing edge segment 26 of the outboard section. Inasmuch as identical arrangements can be utilized for all sections, varying only with the length of cable, only one example will be discussed in detail. The deployment control cable 79 turns around a sheave 80 (when the outboard section ribs are in the stowed position) which is mounted at the outboard end of the shear web 48 of the center section 20. The free end of the cable 79 is attached to a tab 82 at the inboard end rib of outboard trailing edge segment 26. Inasmuch as all of the ribs are linked together, action on one of the ribs suffices to pivot the trailing edge segment from the stowed position to the fully deployed position. Consequently, withdrawal into the fuselage by mechanical or manual means (not shown) of the inner end of the deployment control cable 79 over a relatively short arc suffices to fully deploy the trailing edge segment 26. Generally, the trailing edge segments are deployed consecutively, with the inboard segment 24 being first, then the center and outboard segments 25, 26, and terminating with the aileron unit 17. The separate cables for the individual controls may however be synchronized so that deployment is virtually concurrent. As noted above, the ribs 54 for the aileron 17 pivot inwardly (toward the wing root) in changing to the stowed position.

The aileron control cable 84, as seen in FIG. 2, passes across sheaves 85 in both outgoing and return paths, and at the root of the aileron 17 (FIGS. 6 and 7) is wrapped around a drum 87, for pivoting the aileron 17 in conventional fashion.

As previously mentioned, the three adjacent wing sections 19, 20, 21 are arranged such that the D-spar segments 28, 45, 46 have a sliding fit. In addition, when the center and outboard sections 20 and 21 are fully deployed, they overlap the adjacent sections 19 and 20 respectively over a predetermined length. To enhance span rigidity and react against loading forces, however, a number of locking elements are used which also act to limit pivoting of the successive sections in the plane of the wing. With reference to FIG. 2, one set of locking elements 89, 90, 91, and 92 may be disposed between the inboard section 19 and the center section 20. Similarly, a different set of locking elements, which may be lesser in number, may be disposed between center section 20 and outboard section 21 in the overlap region. A detailed view of one of the locking elements is shown in FIG. 20, to which reference may now be made. Sectional views 20A and 20B represent two different relative positions of a pair of spar elements 93, 94 that are slidable relative to each other (e.g., the skins of inboard and center sections 19 and 20). One segment 93 includes an integral tongue element 95 defined in outline by a generally U-shaped aperture (shown in FIG. 2). The tongue element 95 is resilient and may be pivoted away from the adjacent spar segment 94, to constantly urge a locking button 96 against the segment 94, as shown in FIG. 20A. When a locking aperture 97 in the segment 94 moves opposite the button 96, upon relative movement of the two segments 93, 94 to a predetermined relationship, the button 96 registers within the aperture to lock the two segments 93, 94 together.

Alternatively, manually inserted pins or retainers may be utilized for locking and limiting, or hydraulic or cable mechanisms might be utilized for this purpose.

To summarize the operation of the deployable airfoil structure of FIGS. 1-9, therefore, the telescoping center and outboard sections 20, 21 are first slid outwardly to their full limit by actuation of the first cable and sheave mechanism 66. It may be important in some instances to have the center section deployed first, or to have the trailing edge segments 24, 25, 26 deployed as quickly as possible. In view of the fact that there is no interference between a given section 19, 20, or 21 and the associated trailing edge segments 24, 25 or 26, a number of spanwise extension and chordwise deployment sequences may be employed, as will be evident to those skilled in the art. Similarly as described below in conjunction with a rotor blade configuration, the center section 20 may be fully extended and locked prior to extension of the outboard section 21, if desired. Consequently, the successive trailing edge segments 24, 25, 26 may be pivoted from the stowed position to the fully extended position by action on the appropriate control cables, such as deployment control cable 79. When the wing 12 is fully deployed, the aileron 17 may then be deployed and thereafter operated by the control cable 84 in conventional fashion.

In the fixed wing configuration, this airfoil structure imposes neither a significant weight penalty, nor a significant sacrifice in airfoil characteristics. The operative structures are internally contained within the airfoil. The exterior surface of the airfoil remains aerodynamically clean and continuous across the D-spar segment, the surfaces of the pivotable ribs, and the trailing edge insert for each of the inboard, center, and outboard sections. This continuity exists in both the span and chord directions, but the system at the same time preserves the three-dimensional external geometry desired for the airfoil. Both the maximum thickness and the taper of the deployable portion of the airfoil may be selected in accordance with particular design requirements, a significant aspect which is seldom provided by deployable structures of the prior art. Only limited forces need be applied in effecting the complete deployment cycle. Comparably simple mechanisms or any of a variety of alternative mechanical, hydraulic or pneumatic drives may be utilized to return to the stowed status from a fully deployed status. Those skilled in the art will recognize that a given density may be achieved for a predetermined wing configuration through a selection of the number of telescoping sections or the number of pivotable rib elements for a given area of wing surface. The construction is suitable for use with a wide variety of materials and fabrication techniques, including filament reinforced composites as well as other laminates and various metals.

It will be recognized, with reference to the form shown and described in conjunction with FIGS. 1-9, that essentially the same type of deployable structure is directly applicable to a rotor blade configuration. However, different operative requirements apply to the deployment mechanism and cycle as well as usage of the deployable configuration. The rotor configuration should remain in balance during deployment. Aeroelastic divergence problems superimposed upon the severe vibration and fatigue problems encountered with helicopter rotor blades make it undesirable to start rotation in the fully deployed state as a normal case. Therefore it is desirable as a general rule to bring a short, stiff telescoped assembly up to speed, then extend and deploy the assembly. While it must be recognized that practical limitations exist on the operative life of any deployable rotor blade structure, a high density stowable rotor structure makes possible a number of hitherto unattainable uses for helicopter vehicles.

A synchronized deployment mechanism and a helicopter rotor blade assembly in accordance with the invention are illustrated in somewhat simplified form in FIG. 10. As with the wing structure of FIGS. 1-9, a nestable and pivotally compactable construction is employed, and therefore will not be discussed in detail. Cable and sheave or other mechanisms for deployment and restowing of the trailing edge segments are also not shown in detail.

In FIGS. 10 and 11 are illustrated in simplified form a first rotor blade 100 having three telescoping sections, and a second blade 101, only partially illustrated but which is similarly configured and operated and which therefore need not be described in detail. The sections of the blade 100, as well as the blade 101, are deployed by an extension control cable mechanism 103. It will be appreciated that roller or shoe type guides (not shown) may be utilized to direct control cabling as desired, so that the synchronizing drive assembly may be located in virtually any position or attitude desired. In the present example, the extension control cable mechanism 103 includes a blade extension cable 106, and a blade takeup cable 107 disposed within the interiors of the separate D-spar segments of the rotor blade sections. The cables 106, 107 may be separate or as shown and may comprise the separate ends of a single cable fixed as described below to a selected point on the outboard section of each rotor blade 100, 101.

The cable and sheave system for extension and retraction corresponds in certain respects to that described in conjunction with FIGS. 1-9. That is, relative to the blade 100, the blade extension cable 106 passes over a first sheave 108 rotatably mounted on the inboard section of the blade 100, then passes around a second sheave 110 rotatably mounted at the inboard end of the center section, and then passes around a third sheave 111 rotatably mounted at the outboard end of the center section. The cable ends 106 and 107 are attached to the inboard end of the outboard section by a fixed clip 113 which corresponds to the fixed end attachment shown in the construction previously described.

Between the rotor blades 100, 101, the cable ends 106, 107 wrap around a drive drum 114 and interconnect so that the extension cable for one blade is connected to the takeup cable for the other. A bidirectional drive system 116 rotates the drum 114 in either direction and may be stopped to secure the blades in any desired position of extension. The cables 106, 107 from the righthand blade 100 are wrapped about the drum 114 from opposite sides, and thereafter continued into the appropriate cable end for the other blade 101. Thus rotation of the drum 114 in a particular direction causes the desired synchronized but opposite movement of the cable ends 106, 107.

The system of FIGS. 10 and 11 extends and retracts the blades in synchronism automatically. In the fully compacted or stowed position of the rotor blade 100, as seen in FIG. 11, the relative distance between the first and second sheaves 108 and 110 and between the third sheave 111 and the fixed attachment 113 is at a maximum. Therefore the extension cable end 106 is at maximum length, and if released, centrifugal force can be used to move the blade sections outwardly, with limited brake action being exerted if desired. The same action transpires at the other blade 101, and because of the cross-coupling of the cables 106, 107 between blades, the blades must move together. By driving the drum 114 at an appropriate rate, however, the rate of extension may be limited or controlled. Reversal of rotation effects telescoping of the blades to the stowed position of FIG. 11, again maintaining synchronism. It will be recognized that no drum need be employed, and that the cable ends 106, 107 from the two blades 100, 101 may be directly interconnected, with extension effected manually or by centrifugal force.

A fragment of an airfoil assembly that has both leading and trailing edges that are compactable and deployable is shown in FIGS. 12-15, to which reference is now made. FIGS. 12 and 13 represent the plan and cross-sectional configurations of the airfoil 120 in the fully extended state, whereas FIGS. 14 and 15 represent plan and cross-sectional views of the corresponding airfoil in the stowed condition.

The fixed structural element comprises a pair of back to back [ -shaped spars 122, 123 with the upper and lower surfaces of the spars 122, 123 extending forwardly and reversely, respectively, to receive the support leading edge and trailing edge rib elements 125, 126, respectively. The opposite edges of the rib elements 125, 126 are pivotally mounted in leading edge and trailing edge inserts 128, 129, respectively. The leading and trailing edge deployable segments are similarly arranged, and therefore only the leading edge segment will be described in greater detail. As shown in FIGS. 12 and 13, and comparable to the example of the ribs 33 in FIGS. 1-9, the rib 125 has a principal airfoil length which is of [ -shaped cross section, and incorporates tapering upper and lower airfoil surfaces and an interconnecting web lying along a chord plane of the airfoil 120. Within the skirt portion of the associated spar 122, the rib 125 terminates in an L-shaped flexure pivot 130, one leg of which is fixed to the interior of the spar 122. The flexure pivot arrangement may provide automatic deployment of the ribs 125 from the stowed position, it being evident that a lock (not shown) may be used to hold the ribs compacted. For stowage, the ribs may again be flexed, manually or by a control system (not shown) to the compacted position of FIGS. 14 and 15. Adjacent to the leading edge of each rib, the rib is pivotally coupled to the leading edge insert 128 by a pivot pin 132.

The airfoil 120 is therefore stowable to a high density configuration in which its chord dimension is reduced to a minor fraction of the fully deployed chord dimension. The airfoil structure is aerodynamically clean when deployed, as in the prior examples. A box beam with interior channels may be used to permit telescoping of successive sections in a fashion corresponding to the form of FIGS. 1-9. Alternatively or in conjunction, the fixed airfoil portion may comprise a central box beam.

FIGS. 16-19 illustrate two other configurations in accordance with the invention, as applied to a high performance variable geometry aircraft 135. Variable sweep aircraft wings 136,137 include deployable segments 139, 140 for a selected length along the trailing edge from the wing root. When deployed these segments 139, 140 are continuations of the wing airfoils. When pivoted to the high density configuration, however, the segments 139', 140' (shown in dotted lines) comprise nonstructural beam incorporated within the wing interior. Consequently, the trailing edge sections of the wings 136, 137 at the root are pivoted out of the way during the sweep back operation and available space in the fuselage is more effectively used. The segments 139'; 140' pivot oppositely in the present example to illustrate the flexibility of the arrangement. Both segments may pivot outwardly or inwardly at the same time, or they may compact in a pattern opposite to that shown.

A cooperative function for a high performance variable geometry aircraft which nonetheless has utility as an independent unit, is the variable geometry tail structure 142 best seen in FIGS. 17 and 19. Along with change of the wing geometry to the delta configuration, it is desirable to retract the tail 142 to sharply reduce the airfoil area, and to substitute a small control surface 144 for the control surface 146 used at lower velocities. To this end, the tail structure 142 not only pivots down but its geometry changes as well to a stowed, high density configuration by virtue of inclusion of an interior deployable segment 148. The ribs of the deployable segment 148 are pivotally mounted in the trailing edge of the tail structure 142, and may pivot outwardly or inwardly relative to the fuselage for registration in appropriate recesses as the tail is retracted.

With both these variable area structures, particular operative advantages are achieved without significant cost or weight penalties. Although the deployable segments are aerodynamically clean for purposes of relatively low velocity operation, it should also be noted that these segments are completely enclosed when in the high performance mode.

A feature that may be incorporated in a multiple-section extendible airfoil structure is a control mechanism to insure successive telescoping deployment of the sections, so as to conclude with extension of the outboard section. While this can be effected by separate controls, it is preferable to utilize a single control, such as the cable and sheave mechanism previously shown and described in conjunction with FIGS. 8 and 9. Controlled extension is of particular utility in limiting the extend of aeroelastic divergence of rotor blades. One suitable sequencing control is shown in the three successive views, designated A, B and C of FIGS. 21, to which reference is now made. These views each illustrate D-spar segment fragments 150, 151, 152 of inboard, center and outboard sections, respectively. The center segment 151 includes an aperture 154 for receiving a detent ball 155 also registering within a mating recess in a detent insert 157 mounted in the outboard or tip section 152. The detent ball 155 is spring loaded outwardly by a leaf spring 159 in the detent surface of the insert 157, but is held by the facing surface of the inboard section 150 until the center section 151 is fully extended. Thus the detent system controls sequencing and insures that outward extension forces (e.g., from a cable and sheave system) acting on the outboard section do not cause relative motion between the center and outboard sections until the center section has been fully extended. Then, as seen in FIG. 21B, the detent ball 155 is free of the inboard section 150 and pops out, permitting the outboard section 152 to move to its outward limit. Other expedients, such as a locking pin or mechanism mounted in the center section, will also suggest themselves to those skilled in the art. Of course, no spring 159 or equivalent is needed to force the ball 155 out if the center of the ball is arranged to be spaced on the open side of the aperture 154 relative to the mating surfaces of the sections 151, 152.

A deployable aerodynamic structure that does not provide a continuation of the basic airfoil, i.e., a spoiler or flap mechanism, is illustrated generally in FIGS. 22 and 23. The body portion 165 of an airfoil structure 160 includes a recess 167 along an axis substantially parallel to the span, within which a deployable aerodynamic segment 169 is pivotally mounted. In general correspondence to the previous arrangements, the deployable segment 169 comprises a number of ribs 171, each coupled to the body portion 165 and to a coupling member 173 by pivot couplings 174, 175, respectively. In this instance however, the pivot axes are substantially parallel to the principal plane of the airfoil 160, although they might be at any angle, to provide an acute or even oblique angle to the airstream. Therefore, the deployable segment 169 can be deployed outwardly (FIG. 22) to provide a discontinuity relative to the airfoil 160, or completely nested (FIG. 23) within the airfoil. The internally contained deployment means may be as previously discussed, and have been omitted for simplicity.

The coupling member 173 in this example is configured to have a surface that is flush with the airfoil body 160 when the segment 169 is stowed. Alternatively, a hinged cover (not shown) in the airfoil 160 adjacent to the segment 169 may simply open to permit deployment and close down to provide a smooth airfoil surface. It will also be evident to those skilled in the art that in addition to varying the angle of deployment, other modifications might also be desirable. For aerodynamic purposes the ribs might be spaced or have particular aperture patterns. In operation, control of the extent of deployment may be sufficient for variation of flap or spoiler effect for most applications. Where desired, however, the entire deployable segment 169 might be pivoted as previously shown for aileron structures. In any event, material advantages are achieved by virtue of the design flexibility resulting from the high density configuration and the relatively simple and economical deployment mechanisms that may be used. It should be noted that in deployment only the compact relatively stiff structure is initially exposed to the airstream, so that the arrangement may advantageously be used at high aircraft velocities. In addition, the force of the airstream largely acts against the pivot couplings, not in resisting deployment. Therefore, substantially smaller forces and deployment mechanisms can be used when compared to conventional flap systems, for example.

Airfoil structures previously described have largely been of rectangular planform, but as shown in FIG. 24, this is not a necessary precondition to use the concepts of the invention. A tapered planform wing 180 may, for example, have an outboard section including a leading edge spar segment 182 of fixed geometry and a variable geometry trailing edge segment 184, comprising deployable rib elements 186 of successively shorter length (proceeding outboard). The coupling member 188 in this instance is internally disposed within the ribs 186, apart from the trailing edge but parallel to the axis along which the ribs 186 pivot in the spar segment 182.

As in the previous examples, the pivotable trailing edge segment 184 may be moved to a stowed position, by shifting inwardly toward the airfoil root. Each rib 186 then nests progressively within the next inboard rib 186. The rib elements may again be [ -shaped, but internal clearance sufficient for the coupling member 188 is needed for whatever nesting angle is chosen for the stowed position.

While there have been described above and illustrated in the drawings various forms of variable area airfoil structures, it will be appreciated that other structures and applications are comprehended within the scope of the invention. Such structures and applications include but are not limited to propellors, control surfaces, flaps, variable lift structures, vertical flight and short takeoff and landing vehicles and combinations thereof.