Patent ID: 12187415

DETAILED DESCRIPTION

The description that follows, and the embodiments described therein, are provided by way of illustration of an example, or examples, of particular embodiments of the principles, aspects or features of the invention. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the invention. In the description, like parts are marked throughout the specification and the drawings with the same respective reference numerals. The drawings may be taken as being to scale unless noted otherwise.

The terminology used in this specification is thought to be consistent with the customary and ordinary meanings of those terms as they would be understood by a person of ordinary skill in the aircraft industry in North America. The Applicant expressly excludes all interpretations that are inconsistent with this specification, and, in particular, expressly excludes any interpretation of the claims or the language used in this specification such as may be made in the USPTO, or in any other Patent Office, other than those interpretations for which express support can be demonstrated in this specification or in objective evidence of record, (for example, earlier publications by persons not employed by the USPTO or any other Patent Office), demonstrating how the terms are used and understood by persons of ordinary skill in the art, or by way of expert evidence of a person or persons of at least 10 years' experience in the aircraft industry in North America or equivalent.

In terms of general orientation and directional nomenclature, for aircraft described herein the longitudinal or lengthwise direction is defined as being coincident with the fore-and-aft direction of flight of the aircraft in straight and level flight. In the case of a fixed wing aircraft, the longitudinal direction is parallel to the rolling direction of the wheeled landing gear and to the keel direction of the hull or pontoons, as may be. The leading direction, or leading edge lies toward the forward direction of travel; the rearward or trailing direction or trailing edge is oriented away from (i.e., backwards relative to) the normal direction of advance of the aircraft. Unless otherwise noted, vertical, or upward and downward, are terms that use the landing terrain (or, alternatively, undisturbed water level), as a datum. In the context of the aircraft as a whole, the terms cross-wise, lateral, spanwise, or laterally outboard, or transverse, or transversely outboard refer to a distance or orientation relative to the longitudinal centerline of the fuselage, or of the landing gear nacelles or sponsons or pontoons, as may be. The commonly used engineering terms “proud”, “flush” and “shy” may be used herein to denote items that, respectively, protrude beyond an adjacent element, are level with an adjacent element, or do not extend as far as an adjacent element, the terms corresponding conceptually to the conditions of “greater than”, “equal to” and “less than”.

The directions correspond generally to a Cartesian frame of reference in which the x-direction is longitudinal, the y-direction is lateral, and the z-direction is vertical. Pitching motion is angular motion of the aircraft about a horizontal axis perpendicular to the longitudinal direction. Yawing is angular motion about a vertical axis. Roll is angular motion about the longitudinal axis. Given that the aircraft described herein may tend to have a longitudinal axis of symmetry, a description of one half of the aircraft may generally also be intended to describe the other half as well, allowing for differences between right hand and left hand parts. Also, it may be taken as a default that the structure of the aircraft is of aluminum fabrication except as otherwise shown in the illustrations or indicated in the text, although reinforced composite structure may also be employed. Other materials, such as stainless steel, or wood, might be also be used for some components.

In this discussion it may by understood that persons of ordinary skill are familiar with the aircraft construction and maintenance in North America, and may include aircraft maintenance engineers having knowledge of US Department of Transportation, Federal Aviation Administration publication EA-AC 43.13—1A & 2A “Acceptable Methods, Techniques and Practices, Aircraft Inspection and Repair”, or any successor publication thereof, as updated at the date of priority filing of this specification. This specification is to be interpreted in a manner consistent with that publication.

The discussion herein pertains to amphibious aircraft. The terminology “amphibious aircraft” is understood to be, and is intended to be understood as being, interchangeable with the terms “amphibian aircraft” or simply “amphibian”. An amphibious aircraft, or amphibian, by definition is an aircraft that is capable of landing on terrain in one mode, and also capable of landing on water in another mode.

There is also discussion herein, and distinction between “fixed gear” and retractable landing gear. For the purposes of this discussion, retractable landing gear is landing gear whose position is selectable between an extended or deployed, or “down” position, and a raised or retracted, or “up” position. In many aircraft, when the landing gear are “up” or retracted, the wheels of the lading gear are concealed within a faired housing or cowling, such as a nacelle or a hull blister. However, it is not necessary that the wheels be fully hidden. It is possible to have a retracted position in which the wheels are only partially concealed, or partially faired. In either case, the aircraft has a drive, or drive train or transmission system, or linkage or assembly that the pilot operates to select between a first position (e.g., the raised or “up” position) and a second position (e.g., the lowered, extended, or “down” position). The transmission may be a mechanical system of linkages, or an electrical system, or an hydraulic or pneumatic system, or a mixture or combination of electrical, mechanical or hydraulic elements.

In a “fixed” landing gear aircraft, there may tend not to be a landing gear drive or transmission, and the pilot is not able to select as between positions. The gear has a single mounting condition or position. While the term “fixed” may be used in the sense of a permanent mounting and lack of choice on the part of the pilot, the gear itself may nonetheless retain a degree of movement in respect of one or more degrees of freedom in the sense of tolerating deflection, as, for example, during landing on terrain. Most typically the deflection is a resilient deflection since the landing gear is sprung. The resilience may arise from the structure of the landing gear legs or struts, or from spring or spring-damper systems with which the landing gear is provided.

FIG.1shows a portion of an aircraft,20. Aircraft20is an amphibious aircraft. Although principles, aspects, and features of the invention herein may be applied to rotary wing aircraft as may be appropriate in respect of landing gear apparatus for use in landings with non-trivial forward approach velocity, it may be taken that in the embodiment ofFIG.1aircraft20is a fixed-wing aircraft. Aircraft20may be a high-wing monoplane, with a fuselage indicated as22and the wing structure indicated as24, the join of wing structure24being at the top of fuselage22. Wing24extends laterally outboard to port and starboard of fuselage22.

Fuselage22of aircraft20may further include a lower portion26which may have formed on the underside thereof a hull28for use in water, hull28having a leading portion such as may be termed a bow, and a trailing portion, such as may be termed a stern, or step30. Hull28may be curved and, in the main portion thereof, may have a profile centrally downwardly and rearwardly curved to a central, longitudinally extending keel32. The tail34of aircraft20may extend rearwardly and generally upwardly of hull28.

Hull28may include lateral bulges36such as may tend to extend laterally outboard of the lower portions of fuselage22. Bulges36may also extend somewhat downwardly and may each define a sponson38. Sponson38may include, or may have mounted thereto, a main landing gear housing, or cowling, or apparatus, such as may be designated as main gear housing assembly40, which, may be either left hand or right hand. Although asymmetric aircraft are known, aircraft20may be generally symmetrical about its longitudinal centerline, such that the right hand main gear housing assembly is the mirror image of the left hand one, and the description of one is the same as the other but for their handedness. Hull28may also include a nose landing gear housing, or cowling, or apparatus such as may be designated as nose gear housing assembly42. The nose gear mounted within nose gear assembly42may be a steerable nose gear. The left and right hand main gear and the steerable nose gear may define a tricycle undercarriage, and, to the extent that they include respective main wheels44and nose wheel46, provide a tricycle landing gear for use on terrain, be it tarmac, hardpack, a prepared landing field, a beach, or other surface suited to wheeled motion. The landing gear may be extended, such as for a wheeled landing; or may be retracted, such as for a water-borne landing.

Referring toFIG.3a, nose wheel46of assembly42is mounted in a clevis or yoke52having a central, vertically oriented pivot shaft that is pivotably mounted in a mating steering mount assembly54. Steering mount assembly54includes a pair of laterally spaced apart left and right side frames56, each of which may be substantially planar, the two being mutually parallel. When viewed in profile, side frames56have a generally four-sided shape, interrupted by a rearwardly extending arm58. Side frames56are held in spaced relationship the rearwardly mounted box-structure of the steering head shaft mount60, and by a forward lateral shear web60mounted on, or across, the downwardly and rearwardly angled lower edge of side frames56.

Upper and lower linkages62and64are pivotally mounted at the upper and lower forward corners of sideframes56. Linkages62and64are of the same length. Each has a first end mounted to the aircraft structure, such as in the nose of the fuselage as at66and68respectively, that first mounting being a pivotal mounting having a single degree of freedom, namely pivotal motion about the y-axis. The second end also has pivotal mountings having axes of rotation in the y-direction. Since the respective first ends and second ends are spaced the same distance apart, the quadrilateral of the four bar linkage so formed (i.e., two linkages, the main aircraft fuselage structure, and sideframes56) defines a parallelogram such that while sideframes56follow the arc of the second ends (i.e., the ends distant from fixed structure) of linkages62and64, the angular orientation of sideframes56about the y-axis is constant. Thus the orientation of the z-axis of the steering stub shaft may tend to remain vertical. Steering yoke52has a laterally extending tiller or arm70and steering linkage72by which nose wheel46may be turned left and right, as appropriate.

The nose gear assembly, and therefore nose gear housing assembly42which moves with the nose gear, is driven up and down by a nose gear actuator assembly, indicated generally as74. Actuator assembly74includes a main shaft, or torque tube76that extends laterally across the fuselage (i.e., in the y-direction) between pivotal mountings mounted to the fuselage structure, such as bushings. Torque tube76is able to pivot in a single degree of freedom, namely angular rotation about the y-axis. An input arm78is mounted generally centrally to toque tube76, and may be pushed or pulled to create a moment couple driving torque tube76clockwise or counter-clockwise. Left and right hand output arms80extend forwardly and downwardly of torque tube76to straddle nosewheel46. A lateral cross-member82is rigidly mounted to, and across, sideframes56, and extends laterally from either side of the lower aft-ward corner thereof. Lateral cross-member82may be a shaft that is free to rotate about the y-axis. Drag links84extend between the respective ends of lateral cross-member82and the distal ends of output arms80, such that when torque tube76turns, the ends of arms80move clockwise or counter-clockwise, drawing (or pushing) on drag links84, thereby forcing shaft86, (and hence sideframes56and nose wheel46), to follow the arc of motion of links62,64. Assembly42may also include a return spring, or counter-weight spring,88, such as may tend to bias nose gear housing assembly42to the retracted position. When not being moved, the nose gear assembly, or actuator assembly76, as may be, has locks that retain the nose gear in either the up position or the down position, with associated up-lock and down-lock indicators.

Nose gear housing assembly42is, not surprisingly, mounted at or near the nose of the aircraft. Nose gear housing assembly42may also have, or be, a nose gear shield, or deflector assembly, or shoe, which may be identified generally as nose gear deflector90. Deflector90is pivotally mounted to fuselage22at a pivot fitting location well forwardly of nose wheel46, as indicated at location92, and may be co-axially mounted with either first end66or first end68of linkages62or64, such that deflector90may follow the same arc. The axis (or respective axes) of rotation of the pivot fitting connection at location92(be it at62or64) runs horizontally cross-wise to the aircraft longitudinal centerline. Thus any point of nose wheel landing gear housing assembly42moves in an arc in a vertical plane parallel to the longitudinal centerline (and the presumed direction of forward motion) of aircraft20more generally. Deflector90may have the form of a hull or prow, or stem, or planing surface with a central ridge or stem, such as may tend to displace or ride over, water in the manner of a ski or planing hull. Although deflector90may have an aerodynamic or hydrodynamic form, deflector90is not a cosmetic cowling. It has the structural strength to support the aircraft when landing on water; it is also intended to have structural strength to support the aircraft in an unintentional gear-up landing on terrain, should the range of deflection on impact exceed the limits of deflection of nose wheel46alone while nose wheel46is in the retracted position. To that end, the longitudinal centerline of deflector90may have a central spine, or rib, or keel, or protector, or wear member, wear strip, such as may be in the nature of a sacrificial member or sacrificial keel94extending along the most exposed centerline portion thereof. In the event of a hard landing, or in the event of striking a floating object, sacrificial keel94may tend to contact the terrain or floating object first, and skid along or over it. To either side of sacrificial keel94extending obliquely rearwardly, upwardly and laterally inboard or outboard as the case may be, are first and second side portions identified as93. Which terminate rearwardly in substantially vertical sidewalls95that seat within the side edges of the well in fuselage22that accommodates nose wheel housing assembly42more generally. To the extent that sacrificial keel94is thereby damaged, it is intended that it may be replaced as necessary or suitable. Deflector90may be attached to, or suspended from, spring88.

As can be seen, deflector90extends forwardly of wheel46on a gentle curve that is more forwardly than upwardly, and that, at the point of intersection of the projected curve of the hull and the tangent of the profile of the tire is an oblique angle of perhaps something greater than 120 degrees. As can be seen, nose wheel46is mounted within nose gear housing assembly42, such that the bulk of wheel46is between the inboard and outboard sides of the housing, and the lowermost cusp or portion of wheel46extending through the accommodation, namely aperture48, downwardly proud of the deflector centerline. In the case of a steerable nose-wheel, aperture48is of a shape (such as circular in plan view) to permit wheel46to turn. Nose gear housing assembly42has a main portion that extends forwardly of wheel46, but also side portions that extends alongside, and outwardly and upwardly, of the axle, and most of the sidewall of the body of wheel46. Thus wheel46is mounted within nose gear housing assembly42, generally toward the rearward or trailing end thereof distant from the pivot mounting at the forward or leading end of housing42.

In the example, the extent to which wheel46extends downwardly proud may by 4-6 inches. Expressed differently, the point of intersection of the curves may be somewhere between the 7 o'clock and 8 o'clock positions. Expressed differently again, the wheel may protrude proud of the surface a distance S, where S=D(1−Cos(Theta)), D being the outside diameter of wheel46and theta being the angle (measured from the six o'clock position of wheel46) at which the wheel profile intersects the deflector profile on the centerline. Theta may be in the range of perhaps 15 to 65 degrees, and, in one embodiment, may be in the range of 30-50 degrees. The general tangent slope at mid arc of deflector90, indicated as alpha, may be of the order of 15-40 degrees from the horizontal. In the embodiment shown, it may be 20-35 degrees, with the local tangent angle being closer to 15 or 20 degrees immediately forwardly of nose wheel46, and closer to 35 or 40 degrees in the neighbourhood of forward pivot point68. Expressed differently yet again, deflector90has a length L90forwardly of the axle of nose gear wheel46that may be in the range of about 3-8 times the diameter of nose gear wheel46.

In general, deflector90provides a smooth lead-in-surface extending forwardly of wheel46for engaging, and riding upon, water—like a ski, or hull or slipper or shoe. In some embodiments, the surface of deflector90may also extend aftward of wheel46in a trailing edge tail. Wheel46extends partially downwardly proud of the profile of deflector90. The extent to which it stands downwardly proud may correspond to the expected deflection of the tire of wheel46during a normal landing, plus an allowance of extra travel, perhaps 50% of nominal normal landing load travel. In the event that aircraft20should land on water with the nose gear extended, nose wheel46can only partially immerse itself before the aftmost portion of deflector90also engages the water. At speeds of interest, the clock-wise counter-acting lift arising from deflector90planing on the water may tend to counter-act the counter-clockwise pitching moment generated by hydrodynamic drag on the exposed protruding portion of wheel46.

As illustrated inFIGS.7aand8a, the forward facing surface deflector90of housing assembly42defines a portion of the aerodynamic form, or fairing, of the nose of the aircraft in both the retracted and the extended conditions. As seen inFIG.7b, in the retracted position deflector90seats flush with the aftwardly extending keel of fuselage22.

In some embodiments, aircraft20may have hydrofoil members96such as may be mounted to the upstanding laterally spaced apart sidewalls95of housing assembly42. In the retracted position, hydrofoils96seat in accommodations97defined in fuselage22, such that hydrofoils96are substantially flush with the adjacent structure and form a relatively smooth, continuous streamline or continuous fairing surface as shown inFIGS.7a,7band7c. In the extended position of the nose gear as shown in correspondingFIGS.8a,8band8c, hydrofoil members96are exposed to passing water flow, and, upon contact with the water, may tend to exert a lifting force that is transmitted back through the structure to lift the nose of aircraft20(i.e., to give aircraft20a clockwise turning moment in the side view ofFIG.7bto counter-act the counter-clockwise over-turning moment such as may be generated by wheel46(or wheels44further aft, as may be). In the embodiment shown, hydrofoil members96are mounted abreast of wheel46, at a level comparable to, and in some embodiments slightly above, the axle centerline of wheel46.

FIG.4ashows the landing gear transmission, identified generally as100. Many structural features have been omitted from this illustration for the purpose of making the landing gear components more easily visible. As with nose gear housing assembly42, main gear housing assembly40(be it port or starboard) has main gear wheel44installed in a landing gear housing generally indicated as102. Housing102has a stationary upper, or main, portion104, which is rigidly mounted to sponson38; and a co-operating, movable, or lower portion106, which may include a pivotally mounted main gear vane, or protector, deflector, or deflector assembly110. The pivot mounting may be at the first, or leading, end of housing102. Inasmuch as housing102may ultimately transmit the reactive force from the main gear to carry the aircraft structural load, housing102is structurally connected to a laterally extending spar or beam structure, indicated as108. Structure108may include an I-beam and a deep central frame assembly98as shown inFIG.4a. The ends of beam-and-frame structure98are cantilevers, which have a measure of vertical flex, and the main gear loads are carried at the ends of the cantilevers. Main portion104may have an inboard wall112, an outboard wall114, and an upper wall or covering or cowling116all of which may be rigidly interconnected, and which may have a faired aerodynamic shape. Housing102is mounted to the outboard margin of sponson38, be it port or starboard. Sponson38is water tight, and the bottom wall of sponson38forms a portion of hull28. Housing102has a downwardly opening accommodation118. Accommodation118is generally rectangular, being much longer in the x-direction than wide in the transverse y-direction, such as may be co-operatively shaped matingly to work with the generally box-shaped main gear slipper, or shoe,120of lower portion106.

As seen inFIGS.5ato5e, and inFIGS.6ato6e, shoe120may have an inboard longitudinal wall122, an outboard longitudinal wall124, a bottom deflector plate126, joined together to form a generally U-shaped structure, with side walls124,126being generally vertical, parallel and spaced apart. Main gear wheel44is mounted between the inboard and outboard portions or walls of deflector shoe120. There may be lateral shear webs or shear frame braces123extending laterally therebetween forward of main gear wheel44to maintain walls122and124in spaced parallel relationship from each other. The forward end of shoe120is enclosed, as where bottom deflector plate126is curved forwardly and upwardly to define the forward tip of the ski or slipper, or vane, however it may be called. A pivot mount is located at the foremost tip of shoe120, being indicated as128, and is mounted in structural load spreading bushing assemblies in main portion104. The axis of rotation of the pivot mounting may be horizontal and cross-wise to the vertical plane of symmetry of the aircraft centerline. Bottom deflector plate106may be backed by reinforcements in the nature of longitudinal stringers and transverse frames suitable for maintaining its structural integrity in expected operation.

Bottom deflector plate106has a rearwardly located relief107near its trailing end to accommodate protrusion of main gear wheel44. As shown inFIGS.5aand5b,6aand6b, relief107may have the form of an accommodation130which may be a rectangular opening, or it may be a generally oval or rounded elongate opening corresponding to the shape of the tire of wheel44. The opening is such as to have a first edge portion forwardly of wheel44, and side portions running along the sidewalls of wheel44. Main gear wheel44seats, or is mounted within assembly40between the sidewalls thereof, with a portion, or cusp of wheel44protruding through relief107. Since wheel44moves and housing assembly40move together, wheel44protrudes from plate106in both the extended and retracted positions of the landing gear. Bottom deflector plate106may also have, or be formed to have, a lengthwise extending keel,132, which may have a replaceable sacrificial wear member or skid134. Skid134may be made of a consumable material such as stainless steel. As seen inFIGS.5dand5ekeel132is gently upwardly angled, being nearly horizontal at the point at which the foremost portion of wheel44crosses the profile of keel132, and is formed forwardly curvedly with an increasing angle of slope toward the nose. As may be understood, in a normal landing, shoe120may tend to plane along the water. In an inadvertent gear-up landing on terrain, wheel44may contact the terrain first, and only to the extent that the landing is heavy will shoe120, and, in particular skid134, ride along the terrain. In an inadvertent gear-down landing on water, even as fully deployed inFIG.5e, the clockwise overturning moment due to drag on the exposed portion of wheel44may tend to be counteracted by the lift generated in planing as soon as leading portion136of shoe120immediately forward of wheel44begins to bear on the water surface. The protective presence of the slipper or shoe120forward of wheel44may tend to limit or counteract the overturning drag that can be developed by water drag on wheel44. Further, consideringFIG.3a, to the extent the nose gear deflector90may also engage the water, the counter-acting lifting force of deflector90planing on the water has a very long moment arm relative to wheel44.

The primary element of transmission100ofFIG.4ais a laterally extending shaft140that extends outboard to both port and starboard. At its most outboard extremity shaft140is connected to a co-axial outer tube142, which may be termed a torque tube. At its most inboard end, torque tube142terminates at a lever arm144that has a hollow center to permit the passage of shaft140. Arm144extends to the top end of a damper or spring-damper combination, identified as shock absorber146. The other end of shock absorber146is mounted to a bushing, which is itself mounted to a load spreading bracket (not illustrated) within the frame of the fuselage or sponson. An input arm150is mounted to a sleeve152on shaft140. As may be understood, moving input arm150clockwise and holding arm144stationary will cause shafts140and142to wind up as two torque springs in series.

As shown inFIG.4a, the outboard end of torque tube142is carried in a bearing mounted to upper portion104of housing102. There may also be a central bearing at sleeve152, and another bearing mounted about torque tube142immediately outboard of arm144. At the outboard end of torque tube142is a first pair of matched rearwardly extending arms defining a first wishbone154. At the tips of the legs of first wishbone154is a cross-shaft156that ties the two tips together. A second wishbone158with hollow shaft mounted co-axially with cross-shaft156, and two extending legs (i.e., a fork or clevis, or wishbone) reach from shaft156to axle160of wheel44. The ends of axle160are mounted in seats or bushings that are themselves mounted to inboard wall122and outboard wall124respectively. The assembly so described defines a four bar linkage. That is, the first bar of the linkage is the fixed structure of the aircraft. The second bar of the linkage, effectively pivotally mounted to the fixed structure, is the first wishbone,154. The third bar of the linkage is the second wishbone158, and the fourth bar of the linkage is the deflector or slipper, or shoe,120which is pivotally mounted to the fixed structure of the first bar at pivot128. That is, relative to the fixed structure of the aircraft, shoe120defines the fixed radius arm constraining the arc of motion of wheel46and main gear bottom deflector plate126. Input to shaft140uniquely determines the position of first wishbone154, and therefore also the position of second wishbone158which functions as a drag link or slave link in this mechanism. Thus wheel44is limited to translation in a single degree of freedom along the circumferential arc described by the axle bushings mounted to deflector120. Given the relative length of the arm defined by deflector120, and given the close to horizontal orientation of the arm, that motion is substantially, predominantly, upward-and-downward. Wheel44is movable between retracted and extended positions, as shown. There is an up-lock, and there is a down-lock, not shown. On landing, shaft140and torque tube142provide a somewhat resilient response, that response being damped by shock absorber146.

Transmission100is driven between retracted and extended positions by actuator assembly170mounted within hull28. Actuator assembly170includes a motor (and motor control)172, a gear reducer174driven by motor172; a worm drive176connected to the output of gear reducer174; and a reciprocally movable actuator178driven by worm drive176. As will be understood, driving motor172in a first direction will cause the jack of actuator178to extend, driving arm144clockwise with the effect of extending the main gear; driving motor172in the opposite direction will cause the jack of actuator178to retract, driving arm44counter-clockwise, with the effect of retracting the main gear. Other arrangements of drives could be used. In each case, deflector120moves with the main gear, or, expressed differently, the deflector and the wheeled landing gear move together.

Sleeve152also carries an output interface, or output arm180, which is connected to a drag link182, which drives a bell-crank184. The output of bell crank184is connected to a shock absorber186, which in turn carries the aftmost end of a connecting rod188. Connecting rod188has a foremost end mounted to input arm78which drives torque tube76of nose gear assembly42. Shock absorber186may tend to provide a measure of damping decoupling of the nose gear from the main gear. Thus motion of actuator178drives all three wheels of the tricycle assembly in a co-ordinated manner up and down. In each case, the action of the respective wheel carries the associated deflector up and down as well.

Referring again to the main gear, deflector120protects the forward side of main wheel44. As noted, deflector120has a long and thin shape, deployed leading main wheel44. The moving protective deflector, or vane, or shoe, may extend 2-8 wheel diameters forward of the main gear axle centerline, and, as above, it may be positioned and angled to leave exposed only a portion of main wheel44, as seen from looking aft along the wheel centerline.

Expressed differently, the point of intersection of the curves of the profile of deflector plate126and wheel44may be somewhere between the 7 o'clock and 8 o'clock positions. Expressed differently again, the wheel may protrude proud of the surface a distance S, where S=D(1−Cos(Theta)), D being the outside diameter of wheel44and theta being the angle (measured from the six o'clock position of wheel44) at which the wheel profile intersects the deflector profile on the centerline. Theta may be in the range of perhaps 15 to 65 degrees, and, in one embodiment, may be in the range of 30-50 degrees. The general tangent slope at mid arc of deflector plate126may be of the order of 15-40 degrees from the horizontal. In the embodiment shown, it may be 20-35 degrees, with the local tangent angle being closer to 15 or 20 degrees immediately forwardly of main gear wheel44, and closer to 35 or 40 degrees in the neighbourhood of forward pivot point68. Expressed differently yet again, deflector plate126has a length L126forwardly of the axle of main gear wheel44that may be in the range of 2-10 times the diameter of main gear wheel42. Deflector126may provide a smooth lead-in-surface extending forwardly of wheel44for engaging, and riding upon, water—like a ski, or hull or slipper or shoe. Wheel44extends partially downwardly proud of the profile of deflector plate. The extent to which it stands downwardly proud may correspond to the expected deflection of the tire of wheel44during a normal landing, plus an allowance of extra travel, perhaps 50% of nominal normal landing load travel. In the event that aircraft20should land on water with the main gear extended, wheel44can only partially immerse itself before the aftmost portion of deflector plate126also engages the water. At any significant speed, the clock-wise counter-acting lift arising from deflector plate126planing on the water may tend to counter-act the counter-clockwise pitching moment generated by hydrodynamic drag on the exposed protruding portion of wheel44.

In an alternate, or additional, embodiment, main gear housing assembly40may include hydrofoil members, such as a first or outboard hydrofoil member190and a second or inboard hydrofoil member192, and, should the deflectors not be considered sufficient, hydrofoils190and192may tend also to generate a clockwise lifting moment tending to counteract the overturning moment arising from hydrodynamic drag. Hydrofoils190and192may be relatively small, and may have the appearance of relatively short “fins” extending laterally of the sponson structures respectively. Aircraft20may have respective outboard and inboard reliefs or rebates, or seats or accommodations191and193corresponding to hydrofoils190and192, such that in the retracted position of the landing gear, hydrofoils190and192are at least partially (in the case of hydrofoil member190) or fully (in the case of hydrofoil member192) concealed or seated in a position that is flush with the adjacent faired structure, giving a relatively smooth streamlined form. As above, in the extended position of the landing gear hydrofoils190and192are fully exposed. Hydrofoils190and192may be located generally abreast of wheel44and set at a level near the level of the axle of wheel44, such that in the event that a gear-down landing is made on water, and hydrofoils190and192may engage the water and begin to provide a lifting force even while the depth of wheel44in the water is relatively shallow.

In the event of a flat tire, or in the event of a gear transmission failure in which not all of the gear move to the selected position (be it up or down), the presence of nose deflector90and main gear deflector plates126may be such as to tend to provide a back-up skid surface for landing on terrain.

Nose wheel46has two rotational degrees of freedom—namely rotation about its axle, and pivoting rotation about its predominantly vertical steering shaft. Motion of the nose gear between retracted and extended positions is restricted to a single degree of freedom along the constrained arc of the parallelogram in the x-z plane. Deflector90has a single degree of freedom of motion—namely translation in the arc in the x-z plane associated with motion of the nose gear assembly generally. The up-and-down orientation of the nose gear steering shaft remains constant in the x-z plane.

Similarly, the main gear four bar linkage is constrained to motion in an x-z plane, and the wheel itself, while rotatable in the normal manner about its own axis of rotation to permit wheeled operation, is restricted to the single degree of freedom of travel along the arc traced by the bushings of shoe120relative to pivot point128.

The wheeled landing gear deflectors or shoes or slippers or protectors, however termed, shown and described herein are not to be confused with landing gear “spats”. First, “spats” are aerodynamic fittings employed to reduce fixed landing gear drag that generally are not intended to, and typically do not, produce lift (aerodynamic or otherwise); the shoes described herein are hydrodynamic lift members. Second, true “spats” tend to be a feature of fixed landing gear rather than retractable landing gear. Third, “spats” are aerodynamic fairings of very light structure, as opposed to being structural members intended to take substantial dynamic loads such as landing loads. Fourth, spats tend to extend predominantly rearwardly of the axle of the wheel, with the form of a trailing edge of diminishing section to reduce rearward separation of airflow. The present hydro-dynamic deflectors or slippers or shoes extend predominantly forwardly of the gear, as opposed to aftward.

As described above, the anti-flip, or flip discouraging aspect is passive. That is, it does not rely on pilot intervention, or on electronic sensing or control systems to prevent landing in the wrong configuration. Of course, aircraft20may have such warning systems. However, even if they fail, the deflector may tend to work to protect against an overturning moment.

The deflector moves with the landing gear, and the forward facing surface of the deflector also defines a portion of the exterior fairing of the aircraft in its normal operation in flight. That is, the deflector is not concealed behind other structure, or inside a nacelle in the retracted position, but rather forms a surface of the normal exterior of the aircraft. In the retracted position that surface may be flush with adjacent external surfaces to form a relatively smooth, streamlined form. The deflector protects its respective wheel in both the retracted and the extended position.

Also, as described, the wheel protrudes from the deflector, or shoe, structure in both the extended and the retracted position. In both positions the wheel is in its rolling orientation, i.e., the axle is horizontal and perpendicular to the line of forward motion of the aircraft. In both positions the shoe or deflector protects, or encloses, more than half of the wheel, with the sides of the shoe or deflector extending from the downward portion thereof upwardly and rearwardly or the axle. That is, the wheel is covered on both front and sides.

In the embodiment ofFIGS.10a,10b,11aand11bthere is an amphibious aircraft220, which, unless otherwise noted, may be taken as being the same, or substantially the same, as aircraft20, but that does not have a drive train, or actuator and mechanical transmission, for moving the landing gear from an extended (or “down”) position to a retracted (or “up”) position. That is, aircraft220is a fixed-gear amphibian, and, more particularly, a fixed gear flying-boat amphibian. It has a fixed, or single position, gear. The fixed gear is sprung, i.e., resiliently mounted, such that there is a range of motion of deflection of the wheels such as may be desired for lending on terrain, without a selection of positions. In respect of aircraft220, it may be taken that the views ofFIGS.5ato5eand6ato6e,7ato7c,8ato8c,9aand9bapply to aircraft220as they do to aircraft20. However, rather than representing selected “up” and “down” positions, the two positions shown may be thought of as representing a range of travel from the passive, extended, or no-load position, to the passive, deflected position at full load during landing, e.g., landing on terrain. To see the differences between aircraft220and aircraft20,FIG.10b, with the landing gear deflected upward as under load, andFIG.10awith the landing gear in an un-loaded condition may be compared withFIGS.1,3aand4a. Similarly,FIGS.11aand11b, the corresponding side views, may be compared withFIGS.2a,2b,3a,3band4b.

The embodiment of aircraft220ofFIGS.10a,10b,11aand11bmay be thought of as being equivalent to the embodiment ofFIG.1with the gear selected “down”, except that there is no selection. The gear has only a single “fixed” position. The fixed position nonetheless is the fixed position of a resilient suspension, the resilience of the suspension permitting deflection of the wheels. In this deflection, the leading cowlings, or protectors, or deflectors, or vanes, or shoes, however they may be termed, move with the wheels. The lead-in vane remains in the position to engage water at all positions of travel of the wheels within their resilient range of motion. Expressed differently, aircraft220is an amphibian in which a portion of the water-riding hull is resiliently mounted to deflect on landing. Alternatively, it can be said that aircraft220is an amphibian in which a portion of the water-riding hull moves with, or deflects with, a wheel of the landing gear.

In terms of the nose gear, nose gear222may be generally similar to nose gear42. Nose gear222has a torque tube226corresponding to torque tube76of aircraft20. However, torque tube226is in a fixed position corresponding to the extended position of the nose gear as seen inFIG.3a(and inFIG.10a). Torque tube226does not have an input crank arm78, and is likewise not connected to a drive linkage such as connecting rod188. An input crank arm, analogous to input crank arm78, and having a distal end of the arm secured to fixed structure could be used in place of input arm78to secure torque tube226in the fixed position. Otherwise, nose gear222may be understood as being the same as, or substantially the same as nose gear42.

Considering the main gear, main gear assembly230is substantially the same as the main gear assembly of aircraft20. Main gear wheels46are resiliently sprung on a spring such as torque shaft assembly232. Torque shaft assembly232includes a laterally extending shaft240and respective left and right hand co-axial outer torque tubes connected at either ends thereof, (substantially the same as shaft140and tubes142). As before, left and right hand lever arms144are connected to respective shock absorbers, or spring dampers,146. In contrast to the structure of aircraft20shown inFIG.4a, the main gear assembly of aircraft220does not a driven input arm150, but may have a fixed arm250secured in a position that may otherwise correspond to the “down” position of the main gear in aircraft20. Similarly, there is no transmission100, and no actuator170or its motor, worm drive linkages, or other features. Given that there is no nose gear transmission, parts180,182,184,186and188may be omitted as well. Thus, as can be seen, the resilient torque tube arrangement of the main gear suspension is retained, without the drive and transmission. This may permit a reduction in aircraft weight and complexity. As such, the landing gear may be termed a “single position” landing gear since there is no active choice of more than one position.

Alternatively, the aircraft may have a combination of fixed gear and retractable gear. In an alternate embodiment, the aircraft may have a retractable nose gear, as in aircraft20, and fixed main gear as in aircraft220. In a further alternative, the aircraft may have a fixed nose gear as in aircraft220and retractable main gear as in aircraft20.

As can be seen, aircraft220is a fixed-gear amphibian aircraft. It has a fixed gear having three movably mounted water-riding hull portions—one at the nose, and two at the main gear sponsons. Those hull portions are resiliently mounted. In a further feature of that aspect, the water-riding hull portion is mounted forwardly or, and as a shield for, a first wheel if the fixed gear. The water-riding hull portion is mounted to move when the fixed gear deflects under load.

The amphibian aircraft having at least a first fixed landing gear. The aircraft has fixed main gear. It has a fixed nose gear. It has tricycle landing gear. All of the landing gear is, or are, fixed landing gear. The landing gear includes at least one resiliently mounted landing gear. Aircraft220has a first water riding member mounted to extend forwardly of the first fixed landing gear. The first water-riding member is movably mounted. The first water-riding member is mounted to deflect when the first fixed landing gear deflects.

There description is of a landing gear for amphibious aircraft220. The landing gear includes a wheel for rolling contact with a landing surface, and a deflector. The deflector defines a water-riding hull extending predominantly forwardly of the wheel. The deflector has an accommodation in which the wheel is mounted. The wheel extends partially downwardly proud of the deflector. The wheel and the deflector are mounted to move together, with the wheel protruding partially downwardly proud of the deflector. The landing gear is a single position landing gear. The wheel is resiliently mounted in a single position, and is resiliently movable in a range of motion in response to loading, the water-riding hull being correspondingly movable in co-operation with the wheel. The range of motion of the wheel has a first end of travel and a second end of travel. The first end of travel is a fully loaded position, and the second end of travel is an unloaded position. Immediately forward of the wheel the deflector has a centerline slope forwardly and upwardly of the wheel of less than 30 degrees from horizontal when the wheel is in the unloaded position. In the fully loaded position, immediately forward of the wheel the deflector has a centerline slope forwardly of the wheel that is tangent to horizontal.

The deflector forms one leg of a four-bar linkage. The wheel is carried in a seat defining at least one other leg of that four-bar linkage. The wheel has a foremost exposed portion and at the foremost exposed portion of the wheel a tangent to the wheel, when seen in side view has an angle of less than 45 degrees of arc from horizontal. The deflector has an opening formed therein, and the wheel protrudes through the opening. The opening has a first edge portion running along a first sidewall of the wheel, and an opposed second edge portion running along a second sidewall of the wheel. The deflector has a first side portion, a second side portion, and a keel portion therebetween, the wheel being mounted between the first side portion and the second side portion. The deflector extends at least three wheel diameters forward of the wheel. Immediately forward of the wheel the deflector has a centerline slope forwardly and upwardly of the wheel of less than 20 degrees from horizontal. The deflector has a sacrificial spine. The sacrificial spine is exposed and foremost, whereby in a gear-up landing the sacrificial spine is closer to the ground than any other non-wheel structure.

Aircraft220is an amphibious aircraft having a wheeled landing gear for landing on a landing field. The wheeled landing gear is a fixed gear having a range of motion between an unloaded position and a fully loaded position. The landing gear is mounted within, and extends partially downwardly proud of, a movable landing gear housing, or housings, that define water-engaging surfaces forwardly and laterally of the landing gear and, when the landing gear moves within the range of motion, the landing gear housings and the landing gear move together, with the landing gear extending partially downwardly proud thereof. One of the landing gear wheels is a steerable nose gear. The landing gear housing, or shell, has an external surface defining an external surface of the amphibious aircraft during both flight and water borne operation. The shell has an hydrofoil member mounted thereto.

It may be understood that the various aspects and features may be mixed and matched as may be appropriate. It may also be understood that the foregoing is not intended to be an exhaustive listing of aspects and features of the invention. These and other aspects and features of the invention may be understood with reference to the description which follows, and with the aid of the illustrations of a number of examples.

Various embodiments have been described in detail. Since changes in and or additions to the above-described examples may be made without departing from the nature, spirit or scope of the invention, the invention is not to be limited to those details.