Patent Publication Number: US-2016244155-A1

Title: Helicopter skid landing gear

Description:
BACKGROUND 
     1. Technical Field 
     The embodiments of the present disclosure relate to skid landing gear for a rotorcraft, such as a helicopter. 
     2. Description of Related Art 
     Conventional skid landing gear can have significant deficiencies. For example, conventional skid landing gear assemblies can be a significant source of aerodynamic drag. Further, conventional landing gear can be expensive to manufacture do in part to complicated geometries. There is a need for an improved skid landing gear. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The novel features believed characteristic of the methods and apparatuses of the present disclosure are set forth in the appended claims. However, each method and apparatus, as well as a preferred mode of use, and further objectives and advantages thereof, will best be understood by reference to the following detailed description when read in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a side view of a rotorcraft according to one example embodiment; 
         FIG. 2  is a perspective view of a skid landing gear, according to one example embodiment; 
         FIG. 3  is a view looking aft of a skid landing gear and rotorcraft, according to one example embodiment; 
         FIG. 4  is a perspective view of a step member of a skid landing gear, according to an example embodiment; 
         FIG. 5  is a top view of a portion of a step member of a skid landing gear, according to an example embodiment; 
         FIG. 6  is a side view of a portion of a step member of a skid landing gear, according to an example embodiment; 
         FIG. 7  is a perspective view of a step member of a skid landing gear, according to an example embodiment; 
         FIG. 8  is a side view of a skid landing gear, according to one example embodiment; 
         FIG. 9  is a perspective view of a skid landing gear, according to one example embodiment; 
         FIG. 10  is a perspective view of a skid landing gear, according to one example embodiment; 
         FIG. 11  is a cross-sectional view of a skid landing gear, taken from section lines  11 - 11  in  FIG. 2 , according to one example embodiment; and 
         FIG. 12  is a cross-sectional view of a skid landing gear, taken from section lines  12 - 12  in  FIG. 1 , according to one example embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Illustrative embodiments of the methods and apparatuses are described below. It will of course be appreciated that in the development of an actual embodiment, numerous implementation-specific decisions must be made to achieve the developer&#39;s specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. 
     In the specification, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices are depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of the present disclosure, the devices, members, apparatuses, etc. described herein may be positioned in any desired orientation. Thus, the use of terms such as “above,” “below,” “upper,” “lower,” or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the device described herein may be oriented in any desired direction. 
     Referring now to  FIG. 1  in the drawings, a helicopter  101  is illustrated. Helicopter  101  has a rotor system  103  with a plurality of rotor blades  105 . The pitch of each rotor blade  105  can be manipulated in order to selectively control direction, thrust, and lift of helicopter  101 . Helicopter  101  can further include a fuselage  107 , anti-torque system  109 , and a tailboom  111 . Helicopter  101  can further include a landing gear  113 . Landing gear  113  has significant advantages over conventional landing gear configurations, as discussed further herein. 
     A helicopter landing gear can appear deceptively simple, but can be complex in analysis, performance, and certification. The landing gear can be one of the last lines of defense for saving lives during a hard landing or crash. Furthermore, it is desirable that the landing gear has a high fatigue life and be very damage resistant. Further, it is desirable that the landing gear promote efficiency of the helicopter by being lightweight and aerodynamic. 
     The embodiments of the landing gear of the present application have significant benefits and advantages over conventional helicopter landing gear configurations. For example, the landing gear of the present disclosure is: 1) inexpensive to manufacture; 2) lightweight; 3) strong; 4) does not require chemical milling, thus is more environmentally friendly; 5) aerodynamic; and 6) minimized part count. These and other advantages of the landing gear  113  are achieved at least in part by a complimentary combination of the flat side-walled skid tubes that can each be canted inboard at a cant angle, and forward and aft cross tubes each with two bends so as to form three straight sections, each outboard most straight section being oriented at the same cant angle as the corresponding skid tube. The outboard most straight sections of the cross tubes terminate adjacent to the skid tubes and since the outboard most straight sections are canted at the same angle as the skid tubes, the bent sheet metal saddle can be used to join the cross tubes to the skid tubes. The aerodynamic advantages of the landing gear are realized from the step member, the outboard most straight section of the forward cross tube, and the outboard most straight section of the aft cross tube all being in aerodynamic alignment with respect to the fore/aft direction. 
     Referring to  FIGS. 2-11 , landing gear  113  is illustrated in further detail. Landing gear  113  is symmetric between the left and right sides, except that the right side further includes a maintenance step  211 , thus for the sake of clarity some features may only be described herein with regard to one of the left or right sides. Landing gear  113  is a “skid” style landing gear having skid tubes  201   a  and  201   b,  a forward cross tube  203   a,  an aft cross tube  203   b,  step members  207   a  and  207   b,  and saddles  209   a - 209   d.  Wear plates  249  can be utilized as a replaceable wear surfaces under skid tubes  201   a  and  201   b.  Cross tubes  203   a  and  203   b  can be coupled to fuselage  107  with attachment members  213   a - 213   d.    
     In one example embodiment, skid tube  201   a  has an inboard flat side wall  225   a,  an outboard flat side wall  225   b,  an upper rounded portion  226   a,  and a lower rounded portion  226   b,  each having a thickness. In one example embodiment, skid tube  201   a  is a straight constant thickness member that does not require chemical milling or bending. The cross section of skid tube  201   a  provides advantageous inertia qualities about the horizontal neutral axis and is resistant to buckling when landing on obstructions. Further, by canting the skid tube  201   a  at cant angle A 1 , the skid tube  201   a  maintains geometric inertial stiffness while also reducing the length of cross tubes  203   a  and  203   b  and also reducing the complexity of the saddle joint by having the centerline of the skid tube  201   a  being in the same plane as the centerline of the end portions  219   a  and  219   b  of cross tubes  203   a  and  203   b,  respectively. Referring in particular to  FIG. 12 , skid tube  201   a  is illustrated in a cross section view at cant angle A 1 , which in the illustrated embodiment is approximately 20°.  FIG. 12  illustrates the interaction between an obstruction  1201  and a portion of skid tube  201   a  in that the orientation of skid tube  201   a  about cant angle A 1  still provides the desired inertial stiffness when subjected to a load in an upward direction along vertical axis V 1  while also enabling an efficient and aerodynamic attachment cross tubes  203   a  and  203   b  via saddles  209   a - 209   d.    
     In the illustrated embodiment, forward cross tube  203   a  and aft cross tube  203   b  are each symmetric about a butt line zero plane. Forward cross tube  203   a  can include a straight horizontal portion  215   a,  a first bend  221   a  transitioning the straight horizontal portion  215   a  into a straight angled portion  217   a,  and a second bend  223   a  transitioning the straight angled portion  215   a  into a straight end portion  219   a.  Similarly, aft cross tube  203   b  can include a straight horizontal portion  215   b,  a first bend  221   b  transitioning the straight horizontal portion  215   b  into a straight angled portion  217   b,  and a second bend  223   b  transitioning the straight angled portion  215   b  into a straight end portion  219   b.  In one example embodiment, the centerline of the straight end portions  219   a  and  219   b  of cross tubes  203   a  and  203   b,  are in the same plane as a plane defined by the centerline of skid tube  201   a  along the length of skid tube  201   a.  Thus, the centerline of the straight end portions  219   a  and  219   b  of cross tubes  203   a  and  203   b,  and the skid tube  201   a  are all oriented at cant angle A 1 . In one example embodiment, cant angle A 1  is approximately 20°. Another advantageous characteristic of cross tubes  203   a  and  203   b  is that the utilization of two bends on each side eliminates high stress concentrations that might otherwise be present in a single sharp bend, thereby increasing the fatigue tolerance of the cross tubes  203   a  and  203   b.    
     The cross tubes  203   a  and  203   b  are each coupled to skids tubes  201   a  and  201   b  with saddles  209   a - 209   d.  In one example embodiment, each saddle  209   a - 209   d  is an identical common part. The outside diameters of the straight end portions  219   a  and  219   b  of cross tubes  203   a  and  203   b  are approximately the same as the thickness between inboard flat side wall  225   a  and outboard flat side wall  225   b  of the skid tube  201   a,  thereby allowing for a coupling mechanism, such as a saddle  209   a  to be used therebetween. Conventional saddles are very complicated and expensive members that must be forged, cast, or machined to a complicated geometry. In contrast, saddles  209   a - 209   d  can be made from a constant thickness sheet metal. In the example embodiment, each saddle  209   a - 209   d  can include an outboard planar portion  231   b  and an inboard planar portion  231   a  with a bend portion  233  therebetween, the outboard planar portion  231   b  being adjacent and parallel to the outboard flat side wall  225   b  of the skid tube  201   a,  the inboard planar portion  231   a  being adjacent and parallel to the inboard flat side wall  225   a  of the skid tube  201   a.  In one embodiment, the centerline of bend portion  233  lies in plane P 1 . The forward surface of bend portion  233  also acts as an aerodynamically advantageous profile to decrease drag that may otherwise be associated with a conventional saddle joint. A line of fasteners  235  can be used to attach the saddles  209   a - 209   d  to the cross tubes  203   a  and  203   b.  The fasteners  235  can be located along a crest line where the saddle contacts the outside diameter of the cross tube  203   a.  Fasteners  237  can be used to couple the saddles  209   a - 209   d  to the flat side walls of the skid tubes  201   a  and  201   b.  Flat side walls  225   a  and  225   b  provide an advantageous flat mating area to the planar surfaces  231   a  and  231   b  of saddle  209   a  thereby allowing a multiple row arrangement of fasteners  237  to be used. In another embodiment, skid tubes  201   a  and  201   b  can be round, thus in such an embodiment fasteners  237  could be located in a single line along the crest of the round skid tube. 
     The configuration of saddles  209   a - 209   d,  cross tubes  203   a  and  203   b,  and skid tubes  201   a  and  201   b  produces an efficient and strong gusset shaped attachment without requiring a forged, casted, machined or other support member having a complicated geometry that would be expensive to manufacture. For example, the resulting gusset shape  801  is schematically illustrated in  FIG. 8 . Moreover, a method manufacturing each saddle  209   a - 209   d  can include cutting the overall shape out of a constant thickness sheet metal stock, and then bending each saddle  209   a - 209   d  to form bend portion  233 . 
     In the example embodiment, step members  207   a  and  207   b  are configured as common parts in order save the expense associated with having unique left side and right side parts. Further, step members step members  207   a  and  207   b  are configured to be in aerodynamic alignment with skid tubes  201   a  and  201   b,  and end portions  219   a  and  219   b  of cross tubes  203   a  and  203   b.  To this end, a central axis  229   a  of step member  207   a  lies in a plane P 1  defined by the central axes of straight end portions  219   a  and  219   b  of cross tubes  201   a  and  201   b,  and central axis  226  of skid tube  201   a.  Plane P 1  is a plane in the fore/aft direction and is canted at cant angle A 1 . Axis  229   a  of step member  207   a  starts at a front end portion of skid tube  201   a  and curves upward and forward along plane P 1  to a step portion  239 . Step portion  239  can include an integral tow ring  241  and a striated portion  243 . The striated portion  243  is configured as a stepping area for a person to ingress and egress the aircraft, e.g. helicopter  101 . It should be appreciated that striated portion  243  can be any variety of implementation specific surfaces and geometries. In an example embodiment, striated portion  243  is crowned to promote an ergonomic stepping motion for the person as the contact of between a person&#39;s shoe and the striated portion  243  occurs during an egress or ingress. For example, since step member  207   a  is oriented at cant angle A 1  and the step portion  239  being normal thereto, having striated portion  243  crowned provides an outboard contact surface for a person&#39;s shoe when the person is more outboard relative to the helicopter  101 , and an inboard contact surface for a person&#39;s shoe when the person is more inboard relative to the helicopter  101  during the ingress or egress procedure. This feature allows the same step member  207   a  to be utilized on the left hand side or right hand side of the rotorcraft  101  and still provide an acceptable passenger step regardless of side or angle. 
     In one example embodiment, step member  207   a  can be coupled to skid tube  201   a  with fasteners  245 . An aft portion of step member  207   a  fits within a forward portion of skid tube  201   a.  Interference features  247  can be implemented on the aft portion of step member  207   a  as localized assembly features that can be ground down until a tight fit is achieved to the interior of the forward portion of skid tube  201   a.    
     The particular embodiments disclosed above are illustrative only, as the apparatuses and methods may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Modifications, additions, or omissions may be made to the apparatuses described herein without departing from the scope of the invention. The components of the system may be integrated or separated. Moreover, the operations of the system may be performed by more, fewer, or other components. 
     Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the application. Accordingly, the protection sought herein is as set forth in the claims below. 
     To aid the Patent Office, and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants wish to note that they do not intend any of the appended claims to invoke paragraph 6 of 35 U.S.C. §112 as it exists on the date of filing hereof unless the words “means for” or “step for” are explicitly used in the particular claim.