Abstract:
A multi-linkage suspension system ( 20 ) including isolators ( 32 ) positioned at the outboard ends of the linkages ( 26 ) for suspending and isolating an engine ( 22 ), such as an Auxiliary Power Unit (APU), from a structure ( 24 ), such as an aircraft fuselage. The system ( 20 ) has a plurality of linkages ( 26 ) extending from the engine ( 22 ) towards the structure ( 24 ); each linkages ( 26 ) including an inboard ( 28 ) and outboard ( 30 ) end, a plurality of outboard isolators ( 32 ) attached at the outboard ends ( 30 ), a bracket ( 27 ) for connecting the outboard isolators ( 32 ) to the structure ( 24 ), a rod end ( 34 ), which is preferably elastomeric and includes an elastomer layer ( 36 ), for connecting the plurality of linkages ( 26 ) to the engine ( 22 ). The system ( 20 ) is easily tuned and provides for common components and the location of the isolators ( 32 ) minimizes direct exposure to heat and aggressive fluids.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to elastomeric mountings and systems utilizing the same for suspending an engine and, more particularly, to a suspension system for supporting and isolating an auxiliary power unit relative to an aircraft fuselage. 
     BACKGROUND OF THE INVENTION 
     An Auxiliary Power Unit (APU) provides auxiliary power to the various accessories in an aircraft (ex. lights, etc.) and is conventionally suspended by a plurality of rigid linkages which attach between the fuselage ceiling and the APU. In prior art systems, vibration transmission into the linkages is minimized by directly attaching the rigid linkages to vibration isolators located at, and secured to, the APU (see FIG. 1 a ). Multiple links generally attach to multiple isolators. For example, in one prior art system, seven links connect into only three isolators. Two links connect to the first and second isolators with three links attached to the third. Notably, in these systems the isolators are placed at the hot location of the engine, thus, the isolators must be manufactured from materials that can withstand very elevated temperatures. Moreover, prior art linkage members include mechanical rod ends having ball and race members to allow pivotal motions, but such mechanical rod end bearings are subject to wear and fretting and can exhibit rattle spaces which can transmit undesirable vibration into the fuselage structure. 
     One example of a Prior Art APU suspension system is shown in FIG. 1 a  and suspends an APU  22  (only a portion is shown) from multiple rigid linkage assemblies  10  (only two of seven links shown) which attach at multiple spaced devises  11   a  located near the ceiling of the fuselage structure  24 . Multiple rigid metal spherical rod end members  12   a,    12   b  including right and left threads, respectively, are included at either end of each linkage assembly  10 . Such rigid metal spherical rod ends include a steel housing and a spherical metal ball and may include a low friction race, such as manufactured from rigid low friction material such as phosfur bronze or Nyloy. Likewise, the linkages  10  attach to multiple isolators  13  (only one of three shown) located on the APU  22  by way of metal spherical rod ends  12   b  attached in clevis members  11   b  extending from the isolator housing  18 . These isolators  13  include a housing  18  having a pocket formed therein for receiving the bonded inner member  14  manufactured from a fluorosilicone material as best shown in cross section in FIG. 1 b.    
     The bonded inner member  14  includes a cone bolt  16  including a tapered section  17   a  which is received in a like tapered section  17   b  formed into an engine attachment bracket  15 . As shown in FIG. 1 b,  the bonded inner member l 4  includes upper and lower elastomer pads  19   a,    19   b  spaced above and below a flange  19   c  formed on the rigid inner member  19   d.  These prior art elastomer isolators  13  tend to be bulky, heavy and expensive, thereby leading to a system that is resultantly complex, heavy and expensive. Moreover, should any one of the linkages  10  have a resonance condition within the APU&#39;s operating frequency range, it is difficult to address it without appreciably affecting the remainder of the system. In other words, the resonance can only be addressed by changing the stiffness/damping of elastomer pads  19   a,    19   b.  Thus, addressing the resonance may change a stiffness which appreciably affects the dynamic properties of the overall system. Furthermore, the isolators of such prior art systems are exposed to intense heat and oil, fuels and other detrimental fluid exposure. Therefore, because of such heat and fluid exposure, the use of undesirable fluorosilicone materials is mandated therein. 
     Efforts to mount aircraft engines which include linkages 11 a,  11 b  can be found in U.S. Pat. No. 3,727,862 to Kaufold et al. However, Kaufold provided a fairly rigid vibration path into the structure for vertically oriented vibrations. Moreover, the spring elements are torsion bars 7 a,  7 b,  thus do not provide any significant level of damping. Moreover, the system cannot be easily tuned. Other engine mounting systems include some form of linkage include U.S. Pat. No. 4,717,094 to Chee entitled “Aircraft Engine Mount System With Vibration Isolators,” U.S. Pat. No. 3,836,100 to Von Hardenberg et al. entitled “Engine Mounting Arrangement,” U.S. Pat. No. 4,805,851 to Herbst entitled “Turbine Engine Mounting Bracket Assembly,” and U.S. Pat No. 5.108,045 to Law et al. entitled “Engine Mounting Assembly.” The desk reference by A. B. Davey and A. R. Payne entitled “Rubber In Engineering Practice” teaches in FIG. 5.14(a) a focalized suspension system including a plurality of pivotable mounts attached between the engine bracketry and the structure. This system tends to be bulky and the isolators are still subjected to elevated temperatures. 
     Accordingly, there exists a need for a system for suspending and isolating an engine, such as an APU from the structure, such as an aircraft fuselage which is cost effective, light in weight, easily tuned and exhibits improved service life. 
     SUMMARY OF THE INVENTION 
     In view of the above discussion, it is a first aspect in accordance with the present invention to provide a suspension system for supporting an engine relative to a structure, comprising a plurality of linkages (struts) extending from the engine towards the structure, each of the linkages includes inboard and outboard ends, a plurality of outboard isolators attached at the outboard ends, means including a bracket for connecting the outboard isolators to the structure, and means including a rod end for connecting the plurality of linkages to the engine. Placing isolators outboard on the linkages allows each linkage to be independently tuned and places the isolator in a reduced temperature position where more durable materials and those with better dynamic properties may be employed. Moreover, since the outboard isolators experience less fluid exposure, this allows less fluid savy, yet inherently more durable materials to be utilized. 
     In another aspect, at least one and more preferably all the rod ends include an elastomer layer (an elastomeric rod end) which is preferably bonded to an outer surface of an inner member forming a bonded insert. The bonded insert is preferably received in a housing including a pocket formed therein and is preferably unbonded to the housing thereby allowing substantial pivotal motion yet still providing an elastomer discontinuity. 
     Preferably also, at least one and preferably all of the plurality of outboard isolators comprise elastomer. The elastomer preferably includes a sandwich portion loaded predominantly in compression by a weight of the engine and an integral annular portion extending axially therefrom. Preferably, at least one and more preferably all of the outboard isolators comprise opposed identical elastomer mountings. A stud is received through a bore formed through at least one of the mountings and is likewise threaded into an outboard end of at least one of the linkages. Most preferably, at least one of the opposed mountings comprises a rigid member which has a radially extending portion and a cylindrical portion. 
     In another aspect, the means for connecting the plurality of linkages to the engine comprises a plurality of brackets and a plurality of separate clevis members, one each being secured to each bracket. 
     According to a further aspect, the invention provides a suspension system for supporting an engine relative to a structure comprising a plurality of linkage assemblies extending from the engine towards the structure, wherein each of the plurality of linkages assemblies includes a linkage, an outboard isolator attached at the link&#39;s outboard end and a rod end attached at the link&#39;s inboard end, a bracket adapted for attachment to the engine and a clevis member secured to the bracket wherein the rod end is received by the clevis member for interconnecting individual linkage assemblies to the engine. 
     The mounting system of the present invention overcomes the shortcomings of the afore-described systems. More particularly, the system allows for tuning of each linkage assembly individually without significantly or adversely affecting the performance of the overall system. This tunable feature allows a shift in response frequencies of the linkage away from major operating frequencies. Moreover, dynamic changes in the overall system can be easily accomplished, if desired. Further, the system allows for the use of a simple and common isolator configuration which is positioned at a maximum distance from the engine, thus minimizing exposure to heat and aggressive fluids. In a preferred aspect, the addition of a elastomer rod end allows an additional elastomer discontinuity in the vibration path. Furthermore, the system provides lower weight and cost and ease of changeout of the isolator assemblies without the need to support the engine. The mounting system of the present invention is particularly useful for suspending an APU system of an aircraft. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
     FIG. 1 a  is a side view of a portion of a prior art APU suspension system; 
     FIG. 1 b  is a cross sectioned side view of the bonded inner member in the prior art APU suspension system of FIG. 1 a;    
     FIG. 2 a  is an isometric view of a four point mounting system according an embodiment of the present invention with the engine and structure removed for clarity; 
     FIG. 2 b  is an isometric view of a three point mounting system according an embodiment of the present invention with the engine and structure removed for clarity; 
     FIG. 3 is a side view of the outboard isolator; 
     FIG. 4 is a side view of the inboard elastomer rod end interconnected to the clevis and bracket; 
     FIG. 5 is a side view of the inboard elastomer rod end; 
     FIG. 6 is a frontal view of the inboard elastomer rod end; 
     FIG. 7 a  is a side view of the bonded inner member of the elastomer rod end; 
     FIG. 7 b  is a cross-sectioned side view of the bonded inner member of FIG. 7 a  along line  7   b—   7   b;    
     FIG. 8 is a side view of a linkage; 
     FIG. 9 is a side view of the outboard isolator; 
     FIG. 10 is a top view of the outboard isolator of FIG. 9; 
     FIG. 11 is a cross sectioned side view of a first embodiment of mounting used in the outboard isolator; 
     FIG. 12 is a cross sectioned side view of a second embodiment of mounting used in the outboard isolator; 
     FIG. 13 is a top view of an engine attachment bracket; 
     FIG. 14 is a frontal view of the engine attachment bracket of FIG. 14; 
     FIG. 15 is a frontal view of a single link clevis member; 
     FIG. 16 is a side view of the single link clevis member of FIG. 15; 
     FIG. 17 is a frontal view of a double link clevis member; 
     FIG. 18 is a side view of the double link clevis member of FIG. 17; 
     FIG. 19 is a frontal view of a triple link clevis member; 
     FIG. 20 is a side view of the triple link clevis member of FIG. 19; 
     FIG. 21 is a frontal view of another embodiment of engine attachment bracket; 
     FIG. 22 is a side view of the engine attachment bracket of FIG. 21; 
     FIG. 23 is a frontal view of another double link clevis member; and 
     FIG. 24 is a top view of the double link clevis member of FIG.  23 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
     Referring now to FIGS. 2 a  and  3 - 4 , a suspension system  20  according to an embodiment of the present invention is illustrated. The system  20  includes a APU or engine  22  suspended and isolated relative to a fuselage structure  24 . In FIG. 2 a,  a four point mounting system has been depicted with the engine and fuselage removed for clarity. According to the invention, the suspension system  20  comprises a plurality of rigid linkages  26  extending outwardly and preferably generally upwardly from the engine  22  towards the structure  24 . Each of the plurality of linkages  26  includes an inboard end  28  adjacent to the engine  22  and an outboard end  30  adjacent to the structure  24  as best shown in FIG. 2 a.    
     A plurality of outboard isolators  32  are preferably attached at the outboard ends  30  of each of the linkages  26 . The plurality of outboard isolators  32  connect to the structure  24  by appropriate means, such as the upper bracketry  27  shown. The bracketry  27  may be part of the fuselage structure  24 , separate brackets added thereto, or part of a substructure which itself attaches to the fuselage  24 . Elastomer rod ends  34  preferably comprise the means for interconnecting the plurality of linkages  26  to the engine  22  at the inboard ends  28 . At least one elastomer rod end  34  and more preferably all the elastomer rod ends in the system  20  include an elastomer layer  36  (FIG. 7 b ). The preferred structure of the elastomer rod end  34  will be described more fully with reference to FIGS. 5-7 b  below. Each of the linkage assemblies  25   a-   25   g  comprise a slender, rod like linkage  26 , an outboard isolator  32  including opposed mounts  40 U,  40 L, and a elastomer rod end  34 . 
     Now referring to FIGS.  3  and  9 - 12 , in the suspension system  20 , at least one of the outboard isolators, and more preferably all the outboard isolators  32  also, comprise elastomer  44 . Moreover, preferably, at least one of the plurality of outboard isolators  32 , and more preferably all of them, comprise opposed mountings  40 U,  40 L. Several preferable embodiments of such mountings being illustrated in FIGS. 11 and 12. The opposed mountings  40 U,  40 L are preferably identical center bonded mountings and further comprise a sandwich portion  50  and an annular portion  52 . The sandwich portion  50  is loaded predominantly in compression by the weight of the engine  22  and the annular portion  52  extends axially from the sandwich portion  50  and is preferably formed integrally therewith. The annular portion  52  positions the mounting relative to the upper bracketry  27  and also accommodates any radial loading. 
     Preferably, at least one of the mountings  40 U,  40 L and more preferably all of the mountings are manufactured from a silicone elastomer material or other like suitable high temperature, lightly damped, flexible material. The damping level of the elastomer is preferably about a loss factor of about 0.1. By way of example, and not to be considered limiting, the static spring rates of the isolators in the axial direction are between about 15,000 lbs/inch (2,627 N/mm) and 150,000 lbs/inch (26,270 N/mm) and more preferably 120,000 lbs/inch (21,000 N/mm) and in the radial direction are between about 10,000 (1,750 N/mm) and 100,000 Ibs/inch (17,500 N/mm) and more preferably about 50,000 lbs/inch (8.750 N/mm). The rigid member  42  of the mountings of FIGS. 11 and 12 are preferably titanium or stainless steel. The stiffness and/or the damping level of each individual isolator  32  may be changed to dynamically tune the system characteristics. 
     A stud  41  is received through a bore  43  formed through at least one, and preferably both, of the mountings  40 U,  40 L and the stud  41  is likewise threaded into the threaded portion  45   b  (FIG. 8) of the outboard end  30  of at least one of said plurality of linkages  26 . A jam nut  23   c  on stud  41  prevents backout of the stud  41 . A top nut  23   a  together with shoulder  23   b  the stud  41  secures the assembly  25   e  to the upper bracketry  27  and compresses the lower mount  40 L between the shoulder  23   b  formed on the stud  41  and the bracketry  27  and the upper mount  40 U between the nut  23   a  and the bracketry  27 . 
     Preferably, at least one, and more preferably, all of the opposed mountings  40 U,  40 L comprises a rigid support member  42 . The rigid member  42  preferably comprises a radially extending washer-like portion  46  and a cylindrical tube portion  48  formed adjacent thereto and extending axially therefrom. Alternatively, the rigid member  42  may be formed of two separate pieces as shown in FIG. 12 wherein the radially extending portion  46  is a disc-shaped washer and the cylindrical portion  48  is a hollow tubular cylinder. Preferably, the mountings  40 U,  40 L each include a sandwich elastomer portion  50  adjacent to the radially extending portion  46  and an annular portion  52  adjacent to the cylindrical portion  48 ; the sandwich portion  50  being formed integrally with the annular portion  52 . 
     In both the FIG.  11  and FIG. 12 embodiments, the annular portion  52  is preferably bonded to the cylindrical portion  48  via a suitable bonding process known to those of ordinary skill in the art. In the FIG. 11 embodiment, the sandwich elastomer portion  50  is bonded to the radially extending portion  46 , whilst in the FIG. 12 embodiment, the radially extending portion  48  is unbonded to the sandwich elastomer portion  50  and the radially extending portion  46  is comprised of a separate flat washer. The bore  43  receives the stud  41  (FIG.  9 ). Preferably, the elastomer utilized for the mountings  40 U,  40 L is silicone or other like high temperature material. 
     As best exemplified in FIGS. 2 a  and  4 , the means for connecting the plurality of linkages  26  to the engine  22  at their inboard ends  28  preferably comprises a plurality of brackets  54   a - 56   b  for attachment to the engine  22  and a plurality of separate clevis members  56   a - 56   c  one each being secured to each of the brackets  54   a - 54   b.  As best shown in FIG. 4, the brackets  54   a  are preferably attached to the engine via engine bolts  55 . Similar bolts attach brackets  54   b.  The clevis members, such as member  54   c  shown comprise one or more devises (ex. Clevises  62   a,    62   b,    62   c ) and a tapered pilot  58 . In this figure a three linkage clevis member is shown. But as can be seen in FIG. 2 a,  single  54   a  and double  54   b  linkage clevis members are also utilized in the system  20 . 
     To secure the bracket  54   c  to the clevis member  56   c,  a bolt  64  is inserted through a bore  68  in the clevis member  56   c  through bore  63  in bracket  54   b  and a nut  66  is threaded thereon. This draws the tapered pilot  58  into a like tapered recess  70  securing the clevis member  56   c  to the bracket  54   a.  The elastomer rod ends  34  attach to the linkage  26  by threading the threaded shaft  45   a  into the threaded end  45   b  of the linkage  26 . A jam nut  23   c ′ prevents backoff of the elastomer rod end  34 . A through bolt  69   b  and nut (not shown) securely attach the inner member (not shown) of the elastomer rod end  34  to the clevis  62   c.  Like fastening means are employed for all the elastomer rod ends  34 . 
     Now referring to FIGS. 5-7 b,  the preferred elastomer rod end  34  is illustrated. The elastomer rod end  34  comprises a rigid housing  35  including a preferably spherical-shaped pocket  39  formed in a head portion  29  thereof and a threaded shaft  45   a  for insertion into the like threaded portions  45   b  of the inboard end  28  of linkages  26  (FIG.  8 ). A bonded insert  31  including a rigid inner member  38  is rotatably received in the pocket  39  thereby accommodating pivotal motion between the housing  35  and insert  31 . The housing  35  is preferably manufactured from stainless steel or titanium and the inner member  38  is preferably aluminum. The insert  31  includes a thin elastomer layer  36  to provide an elastomer discontinuity. 
     This discontinuity acts as an additional barrier to sound transmission through the link. By way of example, and not to be considered limiting, the elastomeric rod end preferably includes a very high spring rate of about 500,000-2,000,000 lbs./inch (87,000-348,000 N/mm). The material utilized for the elastomer layer  36  is preferably a synthetic elastomer, such as an epichlorohydrin elastomer having a static shear modulus of between about 250-750 psi and more preferably about 500 psi and a thickness of about 0.03-0.05 inches (0.76-1.27 mm) and more preferably about 0.04 inch (1.02 mm). 
     The thin layer  36  is bonded to the preferably spherical outer surface  37  of the inner member  38  through conventional means. Notably, the elastomer layer  36  is preferably unbonded to the pocket  39  of the housing  35 . A Molycoat lubricant (dry film lubricant) is preferably used on the pocket  39  to aid in assembly. The bonded insert assembly  31  is preferably separately bonded and then inserted into the pocket  39  in the housing  35  by turning it endways and inserting through localized windows  47  formed in the head  29  then rotating the bonded insert  31  into place. The outer dimension of the bonded insert  31  are preferably a precompressed fit with the pocket  39 . This allows for no play in the elastomer rod end  34  while still allowing the pocket  39  and exterior surface  33  of the bonded insert  31  to slide relative to one another thereby providing significant misalignment capability yet minimizing wear, fretting and vibration at the connection point experienced by prior art systems. 
     Alternatively, the housing  35  and inner member  38  may be placed in a mold and the elastomer transferred or injected into the pocket  39  under pressure where only the outer surface  37  of the inner member  38  includes a bonding adhesive; the pocket  39  being devoid of adhesive. This also results in the elastomer layer  36  being unbonded to the pocket  39  and generally precompressed. Preferably, the amount of precompression is to be maximized. The elastomer discontinuity formed by the elastomer layer  36  and the damping provided thereby aid in reducing vibration and noise transmission into the linkages  26 . Moreover, the isolator inserts  31  may be easily removed to allow tuning of the dynamics of the system via changing the mountings  40 U,  40 L, such as to avoid linkage resonance. Further, interchangeable inserts may be bonded in several different materials exhibiting more or less damping. 
     The linkage  26  is best illustrated in FIG.  8  and comprises a tubular portion  49  with threaded end caps  51   a,    51   b  welded thereto. The outboard end cap  51   a  includes right hand threads whereas the inboard end cap  51   b  includes left hand threads. The tube  49  and end caps  51   a,    51   b  are preferably manufactured from stainless steel or titanium. 
     FIGS. 13 and 14 illustrate a typical engine bracket  54   a  for attachment to the outside of the engine  22 . The bracket  54   a  comprises a planar flange  53  including a plurality of lugs  57  having a plurality of engine bolt holes  59  formed therein. A projecting portion  61  depends from the planar flange  53  and includes the tapered recess  70 , through bore  63 , and alignment tab  76 . An engine pilot  65  positions the bracket  54   a  relative to a like-shaped bore formed on the engine casing (not shown). The bracket  54   a  may be manufactured from titanium or stainless steel material or other suitable rigid material. The offset of the through bore  63  and tapered portion  70  from the planar flange  53  should be manufactured to meet the clearance requirements for each respective clevis member. For example, the triple clevis member  56   c  requires more clearance on the bracket  54   b  than the double or single, as best shown in FIG. 2 a,  thus the bore  63  would be positioned further from the planar flange  53 . 
     FIGS. 15 and 16 illustrate a typical single clevis member  56   a  which comprises a body portion  67   a  and a clevis  62   a  extending and offset therefrom. The body portion  67   a  includes a tapered pilot  58   a,  a bore  68   a,  and flat register surface  78   a.  Cross holes  69   a  formed in the clevis  62   a  receive a bolt which attaches, for example, the elastomer rod end  34  (FIG. 2 a ) to the clevis member  56   a.  A slot  71   a  formed between the devises  62   a  receives the head of the elastomer rod end  34  (FIG. 2 a ). The single clevis members  56   a  attach linkages  25   f  and  25   g  to the brackets  54   a  on the right and left aft sides of the engine  22 . The outboard ends  30  of the linkages  25   f,    25   g  are preferably oriented such that they angle towards each other. Flats  74   a  formed on the body  67   a  register with, and prevent the rotation of, bolt  64  (FIG.  4 ). This enables easy one-handed installation of the nut  66  (FIG.  4 ). Upon tightening the bolt (ex.  64  of FIG. 4) thereby drawing the taper  58   a  into the recess  70 , the tab  76   a  registers with flat register surface  78   a  to ensure alignment and prevent rotation to the clevis member  56   a  relative to the bracket  54   a.  Similar locating means are provided on the bracket/clevis member assemblies described with reference to FIGS. 17-20. 
     FIGS. 17 and 18 illustrate a double clevis member  56   b  to which two linkage ssemblies  25   a,    25   b  attach (FIG. 2 a ). These two linkage assemblies  25   a,    25   b  preferably attach to the front right side of the engine  22 . The structure of this clevis member  56   b  and its attachment to the bracket  54   a  is identical to the single clevis member  56   a  except that it includes an additional clevis  62   b.  Linkages  25   a,    25   b  angle forward and aft of the clevis member  56   b,  respectively, but attach in line with a for-and-aft extending vertical plane passing through the bracket  54   a.  Similarly, FIGS. 19 and 20 illustrates a triple clevis member  56   c  to which three linkage assemblies  25   c,    25   d,  and  25   e  each attach. Preferably, the triple clevis  56   c  attaches to bracket  54   b  on the left front of the engine  22 . The structure of this clevis member  56   c  and its attachment to the bracket  54   b  is identical to the double clevis member  56   b  (FIG. 17,  18 ) except that it includes an additional clevis  62   c.  Of the linkage assemblies  25   c,    25   d,    25   e,  the first  25   c  angles forward, the third  25   e  angles aft and the second  25   d  angles right to secure to the structure above the engine&#39;s center of gravity. 
     FIGS. 21 and 22 illustrate another type of engine bracket  54   c.  This engine bracket  54   c  would be used to replace the two brackets  54   a  mounted on the aft sides of the engine by mounting on the aft top of the engine instead As shown in FIG. 2 a.  This engine bracket  54   c  comprises a planar flange  53   c  including a cone bolt portion  72   c  extending therefrom. The cone bolt portion  72   c  includes a tapered pilot  58   c  and a threaded portion  73   c.  The planar flange  53   c  includes a plurality of lugs  57   c  including holes  59   c  for attachment to the top of the engine. 
     FIGS. 23 and 24 illustrate the double linkage clevis member  56   d  (FIG. 2 b ) which is used with the bracket  54   c  of FIGS. 21 and 22. Two aft linkages  25   h  and  25   j  of the three point mounting system shown in FIG. 2 b  are secured in the devises  62   d,    62   e  of clevis member  56   d  via bolts. In FIG. 2 b,  the outboard ends of the linkages  25   h,    25   j  diverge outwardly from each other and attach to the structure (not shown). The orientation of the other linkages assemblies  25   a - 25   e  are the same as in the FIG. 2 a  embodiment. As with the other afore-described clevis assemblies and brackets, the tapered recess  70   d  is received over the tapered pilot  58   c  (FIG. 21) and secured in place with a nut threaded onto the threaded portion  73   c.  To prevent rotation between the clevis member  56   d  and bracket  54   c,  a pin  80   d  registers with the cutout portion  82   c  of flange  53   c.  Preferably, the clevis members  56   a,    56   b,    56   c  and brackets  54   a,    54   b,    54   c  may be manufactured from cast Titanium, such as 6Al-4V, or cast Stainless Steel, such as 15-5PH. 
     The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. Although a few exemplary embodiments of this invention have been described, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the claims. For example, it will be appreciated that different constructions and arrangements of the attachment brackets, clevis members linkages and the outboard isolators may be used. In the claims, any means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Therefore, it is to be understood that the foregoing is illustrative of the present invention and is not to be construed as limited to the specific embodiments disclosed, and that modifications to the disclosed embodiments, as well as other embodiments, are intended to be included within the scope of the appended claims. The invention is defined by the following claims, with equivalents of the claims to be included therein.