Abstract:
A ground maintenance assembly for an aircraft generally including a support member provided with a longitudinal bore and a rigid post portion, a first inner member provided with a longitudinal bore disposed in and secured in such support member and a second inner member provided with a longitudinal recess adapted to receive a pitot tube of such aircraft.

Description:
RELATED APPLICATION 
     This application is a continuation-in-part application of U.S. Ser. No. 13/153,553, filed on Jun. 6, 2011. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the ground maintenance of aircraft and, in particular, to a tether assembly for assuring removal of ground protective devices prior to flight. 
     BACKGROUND OF THE INVENTION 
     During extended ground maintenance times, various protective devices are commonly installed to prevent damage to instrumentation and/or structural damage to the aircraft. Representative are pitot tube covers and landing gear locks pins. 
     Pitot tubes are used on aircraft for measuring speed and altitude. They are sensitive and delicate, and thus prone to damage during maintenance, and storage. To limit damage and contamination, the pitot tube covers are installed during any appreciable outdoor layover to prevent dust, particulates, water, and other foreign matter from entering the probe ports, all of which can contribute to erroneous outputs. Equally important to installation during layover is the need to remove the pitot tube covers prior to flight. Should they remain in place during flight, there are no effective procedures for removal and the instrument&#39;s assessment of speed and altitude are severely compromised. Accordingly and, as a matter of standard operating procedure, if not removed the plane must return to base for cover removal. Inasmuch as the plane may have departed with a full fuel load, landing under such high loading conditions can create substantial forces that can damage the airframe or otherwise affect structural integrity. It would therefor be desirable to provide an apparatus and procedure for assuring the removal of pitot covers prior to flight. 
     It is also desirable to provide the pitot covers and installation equipment in a package that can be carried on the associated plane, thus enabling aircraft, such as military, commercial or business planes, that are transient between facilities of varying ground maintenance capabilities, to have assured access to the covers regardless of landing location. It is also desirable to limit the number of separate items on any maintenance package. Thus installation equipment such as installation poles for higher mounted pitot tubes may be necessary and unavailable at remote locations but present an additional piece of equipment that must. It would thus be further desirable to integrate installation equipment in an assembly that could be readily stowed on and transported with the aircraft. On many aircraft, the covers may be manually installed without auxiliary equipment. On other aircraft, the probes are just out of reach and require installation tools. For larger aircraft with higher mounted probes, an installation tool such as disclosed in our pending application, U.S. Ser. No. 12/580,234 filed on Oct. 15, 2009, provides effective installation assistance. The tool, however, is considered too bulky for aircraft transport, and is generally conveniently available at facilities able to handle the larger aircraft. 
     The landing gear lock pins are installed to disable the landing gear retracting system to prevent inadvertent actuation during maintenance and/or ground operations that could collapse the nose wheel and structurally damage the aircraft. As with the pitot tube covers, the pins must be removed prior to flight, and if not removed, the plane must return to base with the resultant unnecessary expense and potential structural damage from a full weight landing. 
     While there are established procedures for removing the covers and lock pins, human error nonetheless continues to produce non-compliant flights. Accordingly, it would be desirable to provide a maintenance product that would further reduce the chances of the covers and lock pins remaining on the aircraft at takeoff. 
     SUMMARY OF THE INVENTION 
     The present invention provides a highly visible tether assembly for use on parked aircraft that interconnects the pitot tube covers with the landing gear lock pin thereby assuring removal of both the covers and the lock pin as part of the aircraft preflight check list. The assembly is made of heat and environment resistant materials that avoid instrument and air craft damage during installation and residence. For lower mounted probes, the tether connects directly with the covers. For higher mounted probes, the tether attaches to pole mounted covers. 
     More particularly, the tethering assembly comprises a plurality of pitot tube covers for preferably all of the aircraft&#39;s pitot tubes, on both sides of the aircraft, which are interconnected by a lanyard of temperature resistant woven aramid material wherein the lanyard is provided with a middle biasing sleeve that elastically conforms to the fuselage contour in installation. The sleeve includes a connecting strap carrying a lock pin at an outer end that for disabling the landing gear retraction assembly to prevent inadvertent actuation on the ground. 
     In one aspect, the invention provides a ground maintenance assembly for an aircraft having at least a pitot tube on opposed sides of a fuselage above a front landing gear having a retracting linkage immobilized by insertion of a locking pin into a locking aperture thereon wherein the maintenance assembly includes a pitot tube cover for telescopic insertion over each pitot tube; an expandable tether assembly having opposed elongated straps, each having a distal end connected to one of said pitot tube covers, said tether assembly having a sleeve member with a passage therein, wherein one of said straps has a proximal end fixedly connected to said sleeve member and wherein the other strap has a proximal end connected to first end of an elastic member carried in said passage, said elastic member having a second end connected to said sleeve member whereby the length of the tether assembly is less that the distance about the fuselage between the pitot tubes and in assembly the elastic member is stretched to provide a biasing of the tether assembly against the fuselage; and a connecting strap having a first end attached to said tether assembly and a second end connected to said locking pin, said connecting strap having sufficient length in assembly to enable insertion of said locking pin in said locking aperture. In other aspects, the ground maintenance assembly may also use as the sleeve member is a planar rectangular sheet having opposed longitudinal edges releasably secured by fastening members to form a generally tubular shape with said passage extending therethrough. The ground maintenance assembly may have the straps and said sleeve member formed of a heat and environment resistant woven material, such as a meta-aramid polymer. The elastic member of the ground maintenance assembly may be an elastomer subject to ultraviolet degradation upon exposure to ambient sunlit conditions wherein the elastic member in said sleeve assembly is shielded from said condition in said passage. The ground maintenance assembly may include banners carrying notifications for removal before aircraft flight are attached at plural locations on said covers and/or tether assembly. 
     In another aspect, the invention provides ground maintenance assembly for an aircraft having at least a pitot tube located on opposed sides of a fuselage at an elevation above manual access and a front landing gear having a retracting linkage immobilized by insertion of a locking pin into a locking aperture thereon, said maintenance assembly comprising: a pair of pitot cover pole assemblies, each comprising a pitot tube cover for telescopic insertion over each pitot tube; an elastomeric body comprised of a matrix of fused milled rubber and heat resistant fiber, said body having a longitudinal bore; a tubular member of heat resistant woven material bonded to an inwardly facing surface of said bore with a silicone adhesive, said tubular member telescopically receiving said cover and being connected thereto; a spacer member as shown in U.S. Pat. No. 6,901,793 having one end connected to said elastomeric body and a connecting member at another end; an expandable tether assembly having opposed elongated straps, each having a distal end connected to one of said connecting members of a pole assembly. 
     In a further aspect, the invention provides A pitot tube cover assembly for covering the pitot tube of an aircraft wherein said pitot tube is located at an elevation beyond manual access, comprising: a pitot tube cover formed of a heat resistant woven material and having an open ended cavity for telescopically receiving the pitot tube; a cylindrical elastomeric support collar consisting of a matrix of cured rubber and heat resistant fiber, said sleeve having an axial bore therethrough; a tubular sleeve of heat resistant woven material telescopically received in said bore and bonded to said support sleeve with a two part silicone rubber adhesive; an elongated shaft having first end connected to said support collar whereby said shaft may be manually directed for telescopically inserting said pitot cover over the pitot tube. The assembly may have a tubular arm radially extending from an outer surface of the support collar and having an outwardly opening recess for receiving said first end of said shaft, and may have a connecting member is connected with a second end of said shaft, said connecting member including a restraining device for holding the shaft in operative position on the aircraft. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features and advantages of the present invention will become apparent upon reading the following description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is side view of an aircraft provided with an aircraft ground maintenance tether assembly in accordance with an embodiment of the invention; 
         FIG. 2  is a front view of the aircraft of  FIG. 1 ; 
         FIG. 3  is a top view of the tether assembly; 
         FIG. 4  is a top view of the sleeve assembly for the tether assembly; 
         FIG. 5  is a view taken along line  5 - 5  of  FIG. 4 ; 
         FIG. 6  is a schematic view of a landing gear assembly disabled by the lock pin of the tether assembly; 
         FIG. 7  is a side view of a pitot cover pole assembly for a tether assembly in accordance with another embodiment of the invention; 
         FIG. 8  is a side cross sectional view of the pitot cover pole assembly of  FIG. 7  installed over the pitot tube of an aircraft; 
         FIG. 9  is a fragmentary cross sectional view of pitot cover support sleeve; and 
         FIG. 10  is a cross sectional view of the pitot cover assembly in the manufacturing mold. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to drawings,  FIGS. 1 and 2  show an aircraft ground maintenance tether assembly  10  for assuring the installation and removal of covers for the pitot tubes  14  of an aircraft  16  during ground stays for maintenance, layovers and other normal extended aircraft ground based activities. The tether assembly  10  has particular benefit for the Hercules C130 aircraft. Therein, the aircraft  16  is provided with a pair of vertically spaced pitot tubes  14  on each side of the aircraft, generally vertically positioned above the front landing gear  20 . As described below, the tether assembly  10  also includes a lock pin for conventional insertion into an aircraft dependent aperture in the front landing gear retraction assembly for disabling the retraction system therefor in order to avoid inadvertent collapse during ground operation. As part of the preflight check list, the pitot tube covers are removed and the lock pin is removed whereby retraction mechanism is again enabled. 
     The tether assembly  10  of the present invention integrates a tethering system with both the pitot covers and the locking pin to assure removal of both items prior to flight. Referring to  FIGS. 3 through 5 , the tether assembly  10  includes an expandable sleeve assembly  30  having straps  32 ,  34  with proximal ends extending from opposite ends thereof and distal ends attached to a pitot tube cover assembly  36 , each comprising a pair of pitot covers  38   a  and  38   b  interconnected by connecting strap  40 . A lock pin strap  42  has an end loop  44  encircling the center section of the sleeve assembly  30  and terminates with a carrying ring  46  threaded through a cross hole in the head section  48  of a landing gear lock pin  50 . The lock pin  50  includes a shank section  52  for coupling with the landing gear retraction system as described below to prevent inadvertent actuation of the retraction system during ground operations. A retaining strap  54  is connected to the cover assembly  32  and retains the strap  42  in assembly. 
     Referring to  FIGS. 4 and 5 , the sleeve assembly  30  comprises a rectangular body panel  60  having a base surface  61  connected to a reversely turned face surface  62 . The base surface  61  has a reversely folder flap  63 , The flap  63  and face surface  62  have a longitudinal fastening system  64 , such as hook and loop strips, at the lateral sides thereof for forming a sleeve with a longitudinal passage  66  therethrough. Other systems such as zippers, button, snaps or the like can be used for the sleeve and to permit access to the interior for assembly and repair. The strap  32  is fixedly attached to the panel  62  by cross stitching  64 . The strap  34  is attached to the panel  62  by an elastic cord assembly  66 . The cord assembly  66  includes end loops  70  connected at outer ends to the straps  32 ,  34 , respectively, and connected at inner ends to end loops  74  of an elastic cord  78 . The entire cord assembly  66 , particularly the elastic cord  78 , is retained interior of the cover assembly  60  and thus shielded from environmentally degrading UV radiation. Normally, these cords are susceptible to environmental degradation during the long layover times the aircraft may experience, and consequently fail and require replacing. By retaining the cord entirely in the passage, the cord in isolated from sunlit conditions, extending the trouble free life thereof. The cord comprises an elastomeric core covered by an outer fabric sleeve. A bungee type cord is a preferred cord construction. 
     Accordingly, the length of the assembly may be elastically elongated in length in the direction of the arrows to provide tensioning of the tether assembly against the fuselage of the aircraft in assembly. 
     Each cover assembly  36  includes one or more pitot covers  38  connected to a distal end of the strap. For the present embodiment two covers are provided, a lower cover  38   a  and an upper cover  38   b . Both covers are provided with diametrically opposed side loops  74 . One loop of each lower cover  38   a  is connected to the distal ends of the straps  32 ,  34 . An opposed loop of the lower cover is connected the connecting strap  40  connected to a comparable loop on the upper cover. Each cover may have an additional loop for mounting a highly visible removal banner  80  thereon carrying an appropriate indicia thereof such as “Remove Before Flight” reinforcing notice for removal prior to flight. Suitable covers are described in our prior patents, U.S. Pat. Nos. 6,412,343 and 6,901,793. Such covers are commercially available from Sesame Technologies Inc. of Belhaven, N.C., exclusive licensee of the above patents. Preferably, the covers are formed of heat and abrasion resistant woven materials such as meta-aramid polymers. Suitable materials are available such as NOMEX™ or KEVLAR™ materials from E. I. DuPont deNemours and Company. 
     In the present embodiment, the pitot tubes are at an elevation that manual positioning of the covers on the pitot tubes is required. 
     The length of the connecting strap  40  is preferably slightly longer than the distance between the pitot tubes to avoid imposing any adverse loading thereon. The overall length of the tether assembly with respect to the first or lower pitot tube covers is slightly less than the distance from the associated pitot tubes about the fuselage, so as to result in an elastic biasing from the cord to retain the tether assembly snugly against the aircraft, notwithstanding ambient wind conditions, without imparting significant loading on the pitot tubes. The connecting strap  42  and the lock pin  50  have a length allowing insertion of the lock pin without strap tensioning, but short enough so as not to become entangled with any neighboring components. 
     The landing gear disabling takes various forms dependent on the aircraft, mechanically preventing actuation of a retraction linkage or by disabling a retraction actuator. In these designs, a lock pin is inserted into the appropriate aperture. By way of example and not limitation, referring to  FIG. 6 , the front landing gear retraction assembly  90  is provided with aligned through holes in the gear struts  92 ,  94 . The shank  52  of the lock pin  50  is inserted into the holes and prevents articulation of the struts thereby disabling the retraction system and maintaining the lowered position of the gear. 
     For installation, the covers are installed alternately at the sides of the aircraft thereby tensioning the cover assembly to provide the biasing of the tether assembly against the fuselage. Thereafter the lock pin in installed. Removal is by reverse sequence. By coupling the landing gear locking pin and covers in a single assembly with highly visible banners and covers. The identification of one component is an indication that preflight removal has not been completed. Thereafter, undertaking the removal of one component is physically coupled to adjacent components thus compelling the ground personnel to remove all items in order to stow the assembly prior to flight. Also, the woven fabric construction of the major components of the tether assembly lends to compact storage on the aircraft thus providing an assured deployable maintenance assembly at the next required layover. 
     In the embodiment shown in  FIGS. 7-10 , the tether assembly  110  is adapted for manual installation of the pitot tube covers on pitot probes that are positioned at an elevation above manual access. Therein, a pitot cover pole assembly  112  allows manual positioning and installing of the covers at the higher elevation, while providing integration in a tether assembly for unitized deployment and storage, or without the tether, and allowing singular disposition, transport, and/or storage. In the latter condition, the end of the cover assembly is provided with a connecting member for attaching to an aircraft surface to restrict movement during deployment. 
     Referring to  FIGS. 7 and 8 , the cover pole assembly  112  comprises an elastomeric heat resistant support sleeve  120  carrying a heat resistant woven support tube  122  holding a pitot over  124 , a rigid support post  126  connected to the sleeve  120  and a connector arm  128  attached at the bottom end of the support post  126 . The connector arm  128  is connected to one end of a tether assembly  129  as described above, the other end of the tether assembly  129  connected with a cover assembly for the pitot probe(s) on the other side of the aircraft. 
     The support sleeve  120  comprises an elastomeric cylindrical body  130  having a longitudinal bore therethrough. The body  130  includes an integral connecting arm  132  extending radially downward from the outer surface of the body  130 . The arm  132  includes a downwardly opening recess  134  for receiving in assembly a terminal end of the support post  126 . 
     The support tube  122  is a woven cylindrical sleeve of a heat resistant material such as Kevlar having a diameter about the same as the bore of the support body  130 . The body  130  is a cured matrix of milled rubber and heat resistant fibers, preferably the same material as the sleeve. As such, the body does not bind adequately directly to the woven tube. Referring to  FIG. 9 , we have found that pretreating the woven tube  128  with a two part silicone rubber  140  will provide a tightly bonded interface with the body matrix. 
     Referring additionally to  FIG. 10 , this is accomplished by placing the woven tube  128  over a cylindrical core mandrel  144  and applying a layer of the silicone rubber  140  about the tube and through the weave to establish to establish coating layers on the inner and outer surfaces of the tube. The ends of the tube are reversely tucked into the mandrel bore to form the tube mandrel assembly  148 . A suitable silicone rubber is a two part silicone package from Wack Chemie AG comprising Part A as product no. 3009-28 and Part B as product no. 3009-20B. 
     As shown in  FIG. 10 , the tube/mandrel assembly  148  is mounted in a three piece mold  150  comprising a split two-piece center section  152  having interior surfaces corresponding to the outer surfaces of the support sleeve  120 , and end caps  154  having inner hubs  156  supporting the tube/mandrel assembly  148  and providing the end surfaces of the sleeve. A side core  158  is provided for establishing the recess for the support post. 
     The mold halves of the center section are packed with the milled uncured rubber and fiber mixture and manually distributed to the desired contours for the support sleeve. A high temperature silicone rubber is sheet form is milled with loose, chopped fiber fines to form a matrix of about 1-2% fiber by weight. The fibers are preferably the heat resistant fibers used in the covers, such as Kevlar. A suitable uncured rubber is a 70 durometer rubber available as product no. 25787-V-Red from Silcotech North America, Inc. The matrix is processed into thin sheets for conformal insertion into the mold. 
     With the mandrel assembly and side core roughly positioned, the mold halves are assembled and clamped. The mold assembly is heated at a temperature and for a time sufficient to cure the matrix. Temperatures in the range of about 350° F. to 400° F. for a period of about 10 to 20 minutes have provided satisfactory results. 
     After curing, the part is disassembled from the mold components, the ends of the sleeve removed from the mandrel, and the mandrel removed. The sleeve ends are inwardly folded as shown in  FIG. 8  to form outer annuli  164  with aligned openings. A pitot cover  124  is then inserted into the annuli, which are circumferentially attached thereto by stitchings  168 ,  169 . The pitot cover  124  is of the type disclosed in U.S. Pat. No. 6,901,793. Other suitable covers are commercially available from Sesame Technologies, Inc. The cover  124  on the forward end  170  includes an annular sealing element  172  that is telescopically inserted over the frontal end  174  of the pitot probe  176  is inserted. The rearward end  178  of the cover is folded and stitched for form a closure. A banner  180  containing conventional indicia such as “Remove Before Flight” is attached to the rearward end  178 . 
     The support post  126  is formed of a relatively rigid but limitedly flexible heat resistant material such a fiberglass. The ends of the post  126  are inserted into recesses in the support body and the connector arm  128  and attached thereat by a suitable adhesive. The connector arm  128  is preferably molded from the said material as the support collar to provide a flexible, durable and soft material to avoid any impact or abrasion damage to the fuselage during deployment. For additional resistance to separation, the post ends may be connected to the associated part by cross members  182 , such a rigid pin, or by flexible lashing. The connector arm  128  includes an end aperture  184  for connection with the tether  129  or mechanical attachment to the aircraft. The arms and support post may be clad by heat shrink tubing  184  to provide exterior protection and to unitize the assembly of the support post assembly. 
     For aircraft installation, the cover assemblies may be attached to a tethering assembly as described above, before or after installation over the pitot probes. If after installation, it is preferred to incorporate a decoupling component such as clip at both ends to facilitate interconnection and separation. While extended lengths of support post may be used, it is generally preferred to limit the length to about 1-2 feet, depending on the aircraft being serviced. For instance, a 12 inch post has been demonstrated as sufficient for the expected range of personnel on military aircraft such as, without limitation, the C130H, commercial aircraft such as the Boeing 737, and business aircraft such as Challenger and Gulfstream planes. Higher elevation probes are preferably handled by specialized installation tools such as the installer described in out pending application, U.S. Ser. No. 12/580,234 filed on Oct. 15, 2009 and entitled “PITOT TUBE COVER INSTALLATION TOOL”. 
     Having thus described a presently preferred embodiment of the present invention, it will now be appreciated that the objects of the invention have been fully achieved, and it will be understood by those skilled in the art that many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the sprit and scope of the present invention. The disclosures and description herein are intended to be illustrative and are not in any sense limiting of the invention, which is defined solely in accordance with the following claims.