Abstract:
A helicopter pitch link assembly as described herein includes a length adjustment mechanism, such as a turnbuckle, that is accessible when the pitch link assembly is installed on a helicopter that utilizes a weather cover or canopy and a protective boot. The adjustment mechanism extends above the canopy and the protective boot, even when the rotor blades are in a neutral pitch position. This enables quick and easy access to the adjustment mechanisms while eliminating the need to support the rotor blades, which might otherwise be necessary to alleviate stress on the rotor blade hinge points and pitch link assembly.

Description:
TECHNICAL FIELD 
   The present invention relates generally to helicopter control apparatus. More particularly, the present invention relates to a helicopter blade pitch link assembly. 
   BACKGROUND 
   The prior art is replete with helicopter designs and flight control systems for helicopters. A helicopter employs rotating blades that generate upward thrust that lifts the helicopter above the ground.  FIG. 1  is a perspective view of a section of a helicopter  100 , including two blades  102 , an upper control mechanism  104 , and two pitch link assemblies  106 . In operation, upper control mechanism  104  (which rotates along with blades  102 ) actuates pitch link assemblies  106  to adjust the pitch of blades  102 . In this regard, upper control mechanism  104  generally raises or lowers pitch link assemblies  106  to cause blades  102  to rotate about their respective longitudinal axes. The arrows  108  in  FIG. 1  indicate the rotation of blades  102  about their longitudinal axes. 
   The pitch links of most helicopters include length adjusters that are centrally located between the ends of the pitch links. These length adjusters can be manipulated to ensure that all of the pitch links on the helicopter are of equal length, which results in proper in-flight operation, reduces vibrations, and enhances rotor performance. Some prior art helicopters include shields, guards, covers, or other equipment that protect the upper control mechanism from rain, snow, and other weather elements.  FIG. 2  is a schematic partial cross sectional view of a prior art helicopter  200  having an upper control mechanism  202 , a pitch link assembly  204 , a canopy  206 , and a protective boot  208 ;  FIG. 3  is a top view of a portion of helicopter  200 , showing only one blade  209  attached to the rotor. As shown in  FIG. 3 , helicopter  200  accommodates three blades and three respective pitch link assemblies  204  protruding through canopy  206 . Canopy  206  is a rigid cover that extends over upper control mechanism  202 , thus protecting upper control mechanism  202  from the elements. Canopy  206  includes holes formed therein; pitch link assembly  204  protrudes through one of these holes. Protective boot  208  encircles pitch link assembly  204  and spans the space between pitch link assembly  204  and canopy  206 . In other words, protective boot  208  fills the gap created by the hole that receives the pitch link assembly  204 . 
   Protective boot  208  is formed from a flexible material that enables upper control mechanism  202  to raise and lower pitch link assembly  204  without breaking the weather “seal.” In  FIG. 2 , protective boot  208  has a lower section  210  that resembles an accordion and an upper section  212  that resembles a sleeve. Lower section  210  is secured to the center of pitch link assembly  204  using string or laces  214 , while upper section  212  is secured near the upper end of pitch link assembly  204  using string or laces  216 . These laces  216  are concentrated about the upper end of the tube-shaped portion of protective boot  208 . As depicted in  FIG. 2 , upper section  212  of protective boot  208  covers most of the portion of pitch link assembly  204  located above canopy  206 . 
   Pitch link assembly  204  includes an adjustment mechanism  218  that is located under canopy  206  and, consequently, under protective boot  208 . Adjustment mechanism  218  is rotated (using a wrench or other tool) in one direction to lengthen pitch link assembly  204 , and is rotated in the opposite direction to shorten pitch link assembly  204 . To adjust the length of pitch link assembly  204 , protective boot  208  must be untied, removed, or disassembled to provide access to the hole formed in canopy  206 . When upper control mechanism  202  is in the neutral position (as shown in  FIG. 2 ), however, adjustment mechanism  218  is difficult to access from above canopy  206 . Upper control mechanism  202  can be positioned such that adjustment mechanism  218  can be better accessed from above canopy  206 , however, such raised positioning can create high moments and forces at the hinge points of the blade connected to pitch link assembly  204 , for example, at the vertical hinge pin  220  (see  FIG. 3 ). Such high moments can damage internal parts of the link assembly during adjustment and, therefore, the blade must be lifted or otherwise supported to alleviate the force at the hinge points. This technique can be cumbersome to practice and time consuming to complete. Alternatively, pitch link assembly  204  can be completely removed from helicopter  200  (after installing a pitch lock pin) so that it can be easily adjusted by itself. After adjustment, pitch link assembly  204  must be reinstalled on helicopter  200 . Of course, this can add significant time to the adjustment procedure, particularly when several pitch link assemblies need adjustment and/or when many iterative adjustments are needed for a single pitch link assembly. 
   Accordingly, it is desirable to have a helicopter pitch link assembly that can be easily adjusted while installed on a helicopter having a protective canopy and/or a protective boot surrounding the pitch link assembly. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background. 
   BRIEF SUMMARY 
   A pitch link assembly as described in more detail herein enables relatively quick and easy length adjustment while the pitch link assembly is installed on a helicopter. When deployed on a helicopter having a protective canopy and/or a protective pitch link boot, the pitch link assembly can be accessed from above the canopy and without having to remove or destroy the protective boot. Moreover, a technician can easily adjust the pitch link assembly without having to raise the pitch link assembly into a non-neutral position, thus making it easier to perform the adjustment procedure while avoiding pitch link damage. In practice, use of the pitch link assembly can save numerous man hours in completing repetitive adjustments and protective boot maintenance. 
   The above and other aspects of the invention may be carried out in one form by a helicopter blade pitch link assembly having a first link member having a first end configured to be coupled to a pitch control mechanism for the helicopter, a protective boot interface feature located on the first link member, a second link member coupled to the first link member, the second link member having a first end configured to be coupled to a rotor blade for the helicopter, the first link member and the second link member defining a length for the helicopter blade pitch link assembly, and an adjustment mechanism coupled to the first link member and to the second link member. The adjustment mechanism is configured to adjust the length, and the protective boot interface feature is located between the adjustment mechanism and the first end of the first link member. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete understanding of the present invention may be derived by referring to the detailed description and claims when considered in conjunction with the following figures, wherein like reference numbers refer to similar elements throughout the figures. 
       FIG. 1  is a perspective view of a portion of a prior art helicopter; 
       FIG. 2  is a partial cross sectional view of a portion of a prior art helicopter; 
       FIG. 3  is a top view of a portion of a prior art helicopter with the blade aligned with its pitch axis; 
       FIG. 4  is a plan view of a prior art pitch link assembly; 
       FIG. 5  is a plan view of a pitch link assembly according to a first example embodiment of the invention; 
       FIG. 6  is a plan view of a pitch link assembly according to a second example embodiment of the invention; 
       FIG. 7  is a plan view of a portion of the pitch link assembly shown in  FIG. 5 ; 
       FIG. 8  is a cross sectional view of the pitch link assembly shown in  FIG. 7 ; 
       FIG. 9  is a partial cross sectional view of a portion of a helicopter, along with a pitch link assembly of the type shown in  FIG. 5 ; 
       FIG. 10  is a partial cross sectional view of the pitch link assembly, protective boot, and canopy shown in  FIG. 9 ; 
       FIG. 11  is a plan view of a portion of the pitch link assembly shown in  FIG. 6 ; 
       FIG. 12  is a cross sectional view of the pitch link assembly shown in  FIG. 11 ; and 
       FIG. 13  is a partial cross sectional view of a portion of a helicopter, along with a pitch link assembly of the type shown in  FIG. 6 . 
   

   DETAILED DESCRIPTION 
   The following detailed description is merely illustrative in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. 
   For the sake of brevity, conventional aspects and features of helicopters and helicopter control systems may not be described in detail herein. Furthermore, the example embodiments of the invention described herein may be deployed in helicopters having designs that differ from that shown in the figures. In this regard, the inventive concepts can be implemented in the context of different practical helicopter designs, and the particular helicopter assemblies shown and described herein are not intended to limit the scope or applicability of the invention in any way. 
   The following description may refer to elements or features being “connected” or “coupled” together. As used herein, unless expressly stated otherwise, “connected” means that one element/feature is directly joined to (or directly communicates with) another element/feature, and not necessarily mechanically. Likewise, unless expressly stated otherwise, “coupled” means that one element/feature is directly or indirectly joined to (or directly or indirectly communicates with) another element/feature, and not necessarily mechanically. 
   The following description may use descriptive terms such as “upper” and “lower” to refer to the relative positioning of elements or features. Unless otherwise noted, the use of such terms is not intended to limit the scope or application of the invention. Rather, such terms may be used for consistency with the figures and for ease of description. 
     FIG. 4  is a plan view of a prior art pitch link assembly  400 ,  FIG. 5  is a plan view of a pitch link assembly  500  configured in accordance with a first example embodiment of the invention, and  FIG. 6  is a plan view of a pitch link assembly  600  configured in accordance with a second example embodiment of the invention. Pitch link assemblies  500 / 600  represent an improvement over pitch link assembly  400  in that they eliminate steps currently required during pitch link adjustment and protective boot maintenance. In practice, use of pitch link assemblies  500 / 600  can save many man hours related to repetitive adjustment associated with blade tracking. In pitch link assembly  500 / 600 , the components used for pitch link length adjustment are located near the upper end of the assembly, which provides access to wrench flats and the length adjustment mechanism from above the protective canopy, while the rotor controls are set at a neutral position (such that the lag pin remains vertical). With the lag pin in a vertical position, the rotor blade is balanced about its pitch axis. Consequently, little effort is needed to move the adjustment mechanism to track the rotor blade. This condition will reduce the likelihood of damage to pitch link assembly  500 / 600  during tracking adjustment. This condition will also eliminate the need to physically lift the blade during pitch link adjustment. Moreover, with the adjustment mechanism located near the top of pitch link assembly  500 / 600 , the weather protective boot can be mounted below the adjustment mechanism. This mounting position eliminates the need to disconnect and reconnect the protective boot during adjustment of pitch link assembly  500 / 600 . In addition, the protective boot can be replaced in the field by simply removing the old boot without having to disconnect pitch link assembly  500 / 600 . 
   Referring to  FIG. 4 , prior art pitch link assembly  400  includes a length adjustment mechanism  402  that is located near the center of its length. Specifically, the distance identified as “L 1 ” in  FIG. 4  is 9.62 inches. Adjustment mechanism  402  includes wrench flats  403  sized to fit a wrench or other adjustment tool. Adjustment mechanism  402  is a turnbuckle that is rotated to increase or decrease the overall length of pitch link assembly  400 . Adjustment mechanism  402  includes a boot mounting surface  404  that is formed as a cylindrical recess around the top of adjustment mechanism  402 . Boot mounting surface  404  is shaped to receive the protective boot, which can be secured to boot mounting surface  404  using tie down laces. In this regard,  FIG. 2  shows laces  214  securing protective boot  208  around the boot mounting surface of pitch link assembly  204 . These laces  214  are concentrated about the lower end of the tube-shaped portion of the protective boot  208 . When installed, adjustment mechanism  402  is covered by the protective boot and adjustment mechanism  402  is located under the protective canopy. 
   Referring to FIGS.  5  and  7 - 10 , pitch link assembly  500  generally includes a first or lower link member  502 , a second or upper link member  504  coupled to lower link member  502 , a protective boot interface feature  506 , and an adjustment mechanism  508 . Lower link member  502 , upper link member  504 , and adjustment mechanism  508  are formed from a rigid and strong material, such as stainless steel or titanium alloy. Lower link member  502  has a first or lower end  510 , which is suitably configured to be coupled to a pitch control mechanism for the helicopter (not shown in  FIG. 5 ). For example, end  510  may be coupled to the upper control mechanism of the helicopter, as depicted in  FIG. 1  or  FIG. 2 . Moreover, end  510  may be coupled to a swash plate of the helicopter, which tilts to vary the angle of the rotor disc plane, which results in forward/reverse propulsion. End  510  can be coupled to the upper control mechanism using known devices, couplers, bearings, or joints, such as a spherical bearing or a gimbal mechanism and through bolts. Similarly, upper link member  504  has a first or upper end  512 , which is suitably configured to be coupled to a rotor head assembly and blade for the helicopter (not shown in  FIG. 5 ). For example, end  512  may be coupled to a pitch arm, a bracket, or other feature of the rotor head and blade, as depicted in  FIG. 1  or  FIG. 3 . End  512  can be coupled to the rotor head and blade using known devices, couplers, bearings, or joints, such as a spherical bearing or gimbal mechanism and through bolts. When assembled, upper link member  504  and lower link member  502  combine to define an overall length for pitch link assembly  500 . This overall length can be increased or decreased via adjustment mechanism  508 . 
   Protective boot interface feature  506  is located on lower link member  502 . In this example embodiment, protective boot interface feature  506  is located in a fixed position relative to end  510 . In one practical embodiment, the distance identified as “L 2 ” in  FIG. 5  is 9.18 inches. This distance generally corresponds to the fixed length between the mounting hole for lower link member  502  and the center of protective boot interface feature  506 . Notably, the distance L 2  is approximately equal to the distance L 1  in prior art pitch link assembly  400 . 
   Protective boot interface feature  506  is suitably configured to maintain the protective boot on lower link member  502 . In one practical embodiment, protective boot interface feature  506  includes a bulb-shaped protrusion around lower link member  502 , as depicted in  FIG. 5 . Moreover, protective boot interface feature  506  may be integrally formed in lower link member  502  via machining, bonding, welding, or the like.  FIG. 8 , which is a cross sectional view of a portion of pitch link assembly  500 , depicts one example embodiment of protective boot interface feature  506 . In this embodiment, protective boot interface feature  506  includes a protrusion  513  located on lower link member  502 , resilient material  514 , and a rigid outer shell  516 . Protrusion  513  resembles a spherical bulge in this example, and protrusion  513  may be integrally machined into the barrel of lower link member  502 . The shape of protrusion  513  helps to retain resilient material  514  on lower link member  502 . 
   In the example embodiment, resilient material  514  forms a ring that surrounds lower link member  502 . Resilient material  514  has an inner surface that is attached to lower link member  502  via sealant, vulcanization, bonding, adhesive, or the like. In one practical embodiment, resilient material  514  is formed from rubber having a thickness of about 0.25 inch. The shape and composition of resilient material  514  provides a soft and pliable protective boot mount that can seal the protective boot around lower link member  502 . Resilient material  514  has an outer surface that is attached to the inner surface of rigid outer shell  516 . In this manner, rigid outer shell  516  surrounds at least a portion of resilient material  514 , as depicted in  FIG. 8 . In the example embodiment, rigid outer shell  516  has a contoured outer surface that forms a protrusion around lower link member  502 . The outer surface of rigid outer shell  516  provides a suitable clamping surface for mounting of the protective boot. In practice, resilient material  514  may follow the general shape of protrusion  513  and rigid outer shell  516  may follow the general shape of resilient material  514 . Rigid outer shell  516  may be formed from a stiff and tough material, such as stainless steel, titanium alloy, aluminum alloy, fiberglass composite, or carbon fiber composite, and rigid outer shell  516  may be attached to resilient material  514  via sealant, vulcanization, bonding, adhesive, or the like. As described in more detail below, protective boot interface feature  506  facilitates attachment of the protective boot to pitch link assembly  500  at a single location rather than at multiple locations as required by the design shown in  FIG. 2 . 
   Adjustment mechanism  508  is coupled to upper link member  504  and to lower link member  502  in a suitable manner that enables adjustment mechanism  508  to be manipulated to adjust the length of pitch link assembly  500 . Notably, protective boot interface feature  506  is located between adjustment mechanism  508  and end  510  of lower link member  502 . In particular, all of the components of adjustment mechanism  508  are located above protective boot interface feature  506 , as shown in  FIG. 5 . This configuration allows adjustment mechanism  508  to be exposed above the protective boot and the protective canopy when pitch link assembly  500  is installed on the helicopter, thus facilitating easy adjustment of pitch link assembly  500 . In the example embodiment, adjustment mechanism  508  is realized as a turnbuckle that is configured to increase the length of pitch link assembly  500  when rotated in a first direction (e.g., clockwise) and to decrease the length of pitch link assembly  500  when rotated in a second direction (e.g., counterclockwise). 
   The cross sectional view of  FIG. 8  depicts the inner configuration of the turnbuckle employed by pitch link assembly  500 . In this example, lower link member  502  has an externally threaded second or upper end  518 , and upper link member  504  has an externally threaded second or lower end  520  (the dashed lines in  FIG. 8  represent threads). Upper end  518  of lower link member  502  is hollow to receive an extension  522  of lower end  520  of upper link member  504 . The tip of extension  522  is forked to enable the tip to engage an alignment pin  524 . The engagement of the forked tip and alignment pin  524  ensures that upper link member  504  and lower link member  502  do not rotate about their longitudinal axes relative to each other. 
   The turnbuckle itself includes a first or lower internally threaded end  526  that is configured to receive the externally threaded end  518  of lower link member  502 . The turnbuckle also includes a second or upper internally threaded end  528  that is configured to receive the externally threaded end  520  of upper link member  504 . The directions of the threads are selected such that rotation of the turnbuckle in one direction causes lower link member  502  and upper link member  504  to extend outward relative to the turnbuckle (thus increasing the overall length of pitch link assembly  500 ), while rotation of the turnbuckle in the opposite direction causes lower link member  502  and upper link member  504  to withdraw into the turnbuckle (thus decreasing the overall length of pitch link assembly  500 ). 
   As mentioned above, pitch link assembly  500  can be adjusted without having to remove it from the helicopter. Adjustment is accomplished as follows. First, cotter pins (not shown) that secure lock nuts  530  to lock washers  531  are removed. Next, lock nuts  530  are loosened to release the turnbuckle. Then, the turnbuckle can be rotated (in either direction, depending upon the desired adjustment) using a wrench or other tool that engages wrench flats  532  formed on the turnbuckle. After rotation of the turnbuckle, lock nuts  530  are tightened to maintain the turnbuckle in its current position and, therefore, maintain the length of pitch link assembly  500 . After lock nuts  530  are tightened, cotters pins are installed to secure lock nuts  530  to lock washers  531 . 
     FIG. 9  is a partial cross sectional view of a portion of a helicopter with pitch link assembly  500  installed therein. For clarity, the helicopter blade and pitch control mechanism are not depicted in  FIG. 9 . This helicopter subassembly includes a protective boot  534  coupled to pitch link assembly  500 . More specifically, protective boot  534  is coupled to lower link member  502  at protective boot interface feature  506  (see  FIG. 10 ). Protective boot  534  may be formed from any suitable material that is flexible and resilient, for example, rubber, nylon, or a rubber/nylon composite. In this example, protective boot  534  is double layered at the section that slides over pitch link assembly  500 , as shown in  FIG. 10 . This double layering reinforces protective boot  534  where it is clamped to pitch link assembly  500 .  FIG. 10  depicts one suitable arrangement for coupling protective boot  534  to protective boot interface feature  506 . In this example, protective boot  534  is positioned over pitch link assembly  500  such that the inner “donut” hole of protective boot  534  is located at protective boot interface feature  506 . Then, a split collar  540  formed of plastic, composite material, pliable metal, or any suitable material is placed around protective boot  534 . As shown in  FIG. 10 , collar  540  may be contoured to better mate with protective boot interface feature  506 . Once collar  540  is in place, a clamp  542  is installed around collar  540 . Clamp  542  may include a lever actuator  544 , a threaded tightening mechanism, or other securing feature that is configured to secure protective boot  534  around protective boot interface feature  506 . In practical embodiments, clamp  542  may be held in position using a cotter pin or any appropriate locking element. 
   In addition, the helicopter subassembly includes a canopy  536  that is configured to cover the pitch control mechanism for the helicopter. Canopy  536  may be formed from a rigid and weatherproof material such as fiberglass, aluminum, carbon fiber and a NOMEX or aluminum honeycomb core, or the like. Canopy  536  includes a hole  538  formed therein for each pitch link assembly (see  FIG. 3 ). As shown in  FIG. 9 , hole  538  receives pitch link assembly  500  such that end  510  is located below canopy  536  and such that end  512  is located above canopy  536 . Protective boot  534  may also be coupled to canopy  536  such that protective boot  534  spans the space between pitch link assembly  500  and canopy  536 . In this example, the outer lip of protective boot  534  overlaps canopy  536 , and this outer lip is secured to canopy  536  via a ring element  546  (depicted in cross section in  FIG. 9  and  FIG. 10 ) that is clamped, bolted, or otherwise secured to canopy  536 . Notably, when pitch link assembly  500  is installed as shown in  FIG. 9 , adjustment mechanism  508  is completely exposed above canopy  536 . Consequently, adjustment mechanism  508  is readily accessible from above canopy  536  and a technician need not remove protective boot  534 , canopy  536 , or pitch link assembly  500  to make adjustments to pitch link assembly  500 . 
   Pitch link assembly  600  represents another example embodiment of the invention (see FIGS.  6  and  11 - 13 ). Pitch link assembly  600  shares a number of features, elements, and functions with pitch link assembly  500 , and such common features, elements, and functions will not be redundantly described in connection with pitch link assembly  600 . Referring to  FIG. 6 , pitch link assembly  600  generally includes a first or lower link member  602 , a second or upper link member  604  coupled to lower link member  602 , a protective boot interface feature  606 , and an adjustment mechanism  608 . Lower link member  602  has a first or lower end  610 , which is suitably configured to be coupled to a pitch control mechanism for the helicopter (not shown in  FIG. 6 ). Upper link member  604  has a first or upper end  612 , which is suitably configured to be coupled to a rotor blade for the helicopter (not shown in  FIG. 6 ). The overall length of pitch link assembly  600  can be increased or decreased via adjustment mechanism  608 . 
   Protective boot interface feature  606  is located on lower link member  602 . In this example embodiment, protective boot interface feature  606  is located in a fixed position relative to end  610 . In one practical embodiment, the distance identified as “L 3 ” in  FIG. 6  is 9.73 inches. This distance generally corresponds to the fixed length between the mounting hole for lower link member  602  and the center of protective boot interface feature  606 . Notably, the distance L 3  is approximately equal to the distance L 1  in prior art pitch link assembly  400 . 
   Adjustment mechanism  608  is coupled to upper link member  604  and to lower link member  602  in a suitable manner that enables adjustment mechanism  608  to be manipulated to adjust the length of pitch link assembly  600 . Notably, protective boot interface feature  606  is located between adjustment mechanism  608  and end  610  of lower link member  602 . In particular, all of the components of adjustment mechanism  608  are located above protective boot interface feature  606 , as shown in  FIG. 6 . This configuration allows adjustment mechanism  608  to be exposed above the protective boot and the protective canopy when pitch link assembly  600  is installed on the helicopter, thus facilitating easy adjustment of pitch link assembly  600 . In the example embodiment, adjustment mechanism  608  is realized as a turnbuckle that is configured to increase the length of pitch link assembly  600  when rotated in a first direction (e.g., clockwise) and to decrease the length of pitch link assembly  600  when rotated in a second direction (e.g., counterclockwise). 
   The cross sectional view of  FIG. 12  depicts the inner configuration of the turnbuckle employed by pitch link assembly  600 . In this example, lower link member  602  has an internally threaded second or upper end  618 , and upper link member  604  has an externally threaded second or lower end  620  (the dashed lines in  FIG. 12  represent threads). Upper end  618  of lower link member  602  is hollow to receive an extension  622  of lower end  620  of upper link member  604 . The tip of extension  622  is forked to enable the tip to engage an alignment feature  623 . In  FIG. 12 , alignment feature  623  is depicted in cross section, with one side of the forked extension  622  behind alignment feature  623 . The engagement of the forked tip and alignment pin ensures that upper link member  604  and lower link member  602  do not rotate about their longitudinal axes relative to each other. 
   The turnbuckle itself includes a first or lower externally threaded end  626  that is configured to receive the internally threaded end  618  of lower link member  602 . The turnbuckle also includes a second or upper internally threaded end  628  that is configured to receive the externally threaded end  620  of upper link member  604 . The directions of the threads are selected such that rotation of the turnbuckle in one direction causes lower link member  602  and upper link member  604  to extend outward relative to the turnbuckle (thus increasing the overall length of pitch link assembly  600 ), while rotation of the turnbuckle in the opposite direction causes lower link member  602  and upper link member  604  to withdraw into the turnbuckle (thus decreasing the overall length of pitch link assembly  600 ). 
   As mentioned above, pitch link assembly  600  can be adjusted without having to remove it from the helicopter. Adjustment is accomplished as follows. First, cotter pins (not shown) that secure lock nuts  630 / 632  to lock washers  631 / 633  are removed. Next, lock nuts  630 / 632  are loosened to release the turnbuckle. Then, the turnbuckle can be rotated (in either direction, depending upon the desired adjustment) using a wrench or other tool that engages wrench flats formed on the turnbuckle. Due to the perspective of  FIG. 11  and  FIG. 12 , the wrench flats on the turnbuckle are not distinguishable. These wrench flats, however, may be located on a section  635  of the turnbuckle. After rotation of the turnbuckle, lock nuts  630 / 632  are tightened and secured to lock washers  631 / 632  to maintain the turnbuckle in its current position and, therefore, maintaining the length of pitch link assembly  600 . 
     FIG. 13  is a partial cross sectional view of a portion of a helicopter with pitch link assembly  600  installed therein. For clarity, the helicopter blade and pitch control mechanism are not depicted in  FIG. 13 . As described above in connection with  FIG. 9 , this helicopter subassembly includes a protective boot  634  coupled to pitch link assembly  600  and a canopy  636 , where protective boot  634  is also coupled to canopy  636 . When pitch link assembly  600  is installed as shown in  FIG. 13 , adjustment mechanism  608  is completely exposed above canopy  636 . Consequently, adjustment mechanism  608  is readily accessible from above canopy  636  and a technician need not remove protective boot  634 , canopy  636 , or pitch link assembly  600  to make adjustments to pitch link assembly  600 . 
   While at least one example embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the example embodiment or embodiments described herein are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the described embodiment or embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the invention as set forth in the appended claims and the legal equivalents thereof.