BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an aircraft engine mount and, more particularly, to an aircraft engine mount which permits the engine to be swung out of its normal operating position for servicing and inspec¬ tion and which prevents the engine from moving from its normal ope'rating position during a crash.

2. Description of the Prior Art

Aircraft engine mounts which act to transmit vertical, lateral, fore-aft and torque loads to the frame to which the engine is mounted, yet permit thermal expansion and contraction of the aircraft engine, have been known in the prior art for a long time. In addi¬ tion, the general mechanical principles which form the basis for the design and operation of struts and other static support members as well described in standard textbooks of physics and mechanical engineering such as Merian, J.L. Mechanics, N.Y. , John Wiley & Sons, 1956 and Kittel, C., Knight, W.D. , Ruderman, M.A. , Mechanics, ^■ Berkeley Physics Course Vol. 1, Newton, Mass., Education Development Center, 1968, reference to which is hereby expressly made.

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Despite the availability of a variety of aircraft engine mounts, there exists a need in the art for an improved engine mount which will facilitate complete, easy inspection and servicing of the engine, without requiring removal of the engine, yet still prevent the engine from breaking free during a crash.

SUMMARY OF THE INVENTION

In order to aid in the understanding of the present invention, it can be stated in essentially summary form that it is directed to an aircraft engine- to-airframe mounting where the rear of the aircraft engine may easily be swung out for inspection and ser¬ vicing, yet is capable of remaining in its operating position during a crash. - To this end, the front upper portion of the engine is attached to the airframe during servicing by removable means that, when attached, trans¬ mits fore-aft, lateral and torque loads of the engine to the airframe. Additionally, the front lower portion of the engine is attached to the airframe so as to transmit only vertical and lateral loads to the airframe. Addi¬ tional removable means are attached to the airframe during servicing so that when attached, fore-aft loads of the engine are transmitted to the airframe and the engine is rotatable about a vertical axis. Also, the rear portion of the engine is removably attached to the airframe so that when attached, fore-aft, vertical, lateral and torque loads of the engine are transmitted to the airframe in such a manner that the engine will remain fixed in the event of a crash.

It is an object of the present invention to provide an aircraft engine mount which permits the engine to be swung out of normal operating position for easy inspection and service.

It is another object of the present invention to provide an aircraft engine mount capable of maintain¬ ing the engine in its normal operating position during a crash.

It is still another object of the present invention to provide an aircraft engine mount having relatively few components.

Further objects and advantages of this inven¬ tion will become apparent from a study of the following portion of the specification, the claims and the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a side view looking inboard of an aircraft engine mounted in accordance with the present invention, immediately before being swung-out for servicing. -

Figure 2 is a top view of the aircraft engine, mounted in accordance with the present invention, immedi¬ ately before being swung-out for servicing, with a phantom view of the engine in swung-out configuration.

Figure 3 is a rear view of a rear mount of the aircraft engine, mounted in accordance with the present invention.

Figure 4 is a section of the rear mount taken along line 4-4 of Figure 3.

Figure 5 is a top view of a front upper mount assembly of the aircraft engine mounted in accordance with the present invention.

Figure 6 is a section of the front upper mount assembly of the aircraft engine mounted in accordance with the present invention.

Figure 8 is a section of a lower strut taken along line 8-8 of Figure 7.

Figure 9 is a section of the front lower mount assembly taken along line 9-9 of Figure 7.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The following specification, taken in conjunc¬ tion with the drawings, sets forth the preferred embodi¬ ment of the present invention. The embodiment of the invention disclosed herein is the best mode contemplated by the inventors for carrying out their invention in a commercial environment, although it should be understood that various modifications can be accomplished within the parameters of the present invention.

The preferred embodiment contemplates the use of the present invention in an aircraft having two turbine engines, symmetrically placed with respect to the vertical centerplane of the fuselage. However, the present invention may be used in an aircraft having one or more engines, and these engines may be either turbine type or other types of aircraft engines. Thus, this description of a two turbine engine mount apparatus is exemplary only. In the following description, reference will be made to only one engine mount. The other engine mount in a two engine arrangement would be a mirror image with respect to the vertical centerplane.

During flight, each engine is attached to the aircraft's airframe by a rear mounting ring which is attached to and encircles the rear portion of the engine and is also attached to the airframe, serving to trans¬ mit vertical, lateral, fore-aft and torque loads of the engine to the airframe. The engine is also attached, during flight, to a front lower mount, which is in turn attached to the airframe so that vertical, lateral and torque loads of the engine are transmitted" to the airframe. In addition, the front lower mount has a

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generally vertically mounted spherical bearing assembly and is movable in the fore-aft direction so as to permit fore-aft thermal expansion and contraction of the engine. In order for ground maintenance to be per¬ formed on the engine, three struts which are used solely for maintenance purposes are installed. A lower strut .is installed between the front lower mount and the air¬ frame so that fore-aft loads of the engine are trans- mitted to the airframe. Two upper struts are attached between the airframe and a common pivot point on a front upper mount attached to the engine. This pivot point has an axis which generally coincides with the axis of the front lower mount. After the rear mounting ring is disconnected from the airframe, the three- struts serve to support the engine while it is swung out for servicing. During swing-out the engine is primarily rotating on the lower mount bearing. When servicing is complete and the rear mounting ring is reattached, the three maintenance struts are removed. Upon reattachment of the driveshaft, the aircraft is then ready for flight.

Referring now to the drawings for a detailed description for the engine mounts and maintenance struts of the present invention, reference is made first to the front upper portion of an engine 14, as shown in Figure 5. A front mount 10 having a generally arc- shaped bracket 11 is secured to the aircraft engine 14 by bolts 15. A tongue 18 projects generally perpen¬ dicularly from the plane of a bracket 10, and has a generally vertical hole 19 as more clearly shown in Figure β.

A first, relatively longer, upper strut 21 is seen generally in Figure 5. The strut 21 has a male rod

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portion 22 with a cylindrical shoulder 23 separating a relatively larger diameter portion 24 form a relatively smaller diameter portion 25 having threads 26. The larger diameter portion 24 of male rod 22 rigidly attached, for instance, by welding, to a tongue 23 which has a hole 29 in a rounded end 30, as more clearly shown in Figure 6. A female rod portion 31 is bored and tapped on an end 32 with threads 33 so as to mate with the threads 26. End 34 of female rod 31 is attached to a flat tongue 35 and an S-shaped tongue 36, as seen more clearly in Figure 1.

A second, relatively shorter upper strut 38 is seen generally in Figure 5, the strut 38 having female rod portion 39. The sole difference between the first, longer upper strut 21 and the second, shorter upper strut 38 is the relative length of the female rods 31 and 39, respectively. Therefore, for the sake of brevity, the description of longer upper strut 21 will be adopted but not repeated with respect to shorter upper strut 38.

Figure 5 shows a first upper strut bracket 52 and a second upper strut bracket 53, and Figure 7 shows a lower strut bracket 54, each having a flat rectangular base portion 56 and an asymmetrical tongue 58 projecting perpendicularly from the base portion 56. The thickness of the tongue 58 is chosen so as to fit between the tongues 35 and 36 of the struts 21 and 38. The strut brackets 52, 53 and 54 are secured to the airframe 60 by bolts 61, as shown, for instance, in Figures 1 and 5, and the tongues 35 and 36 of upper struts 21 and 33 are removably attached to the upper strut brackets 52 and 53 by pivot pins 62.

As shown in Figure 6, the tongue ^' s 28 of the upper struts 21 and 38 are removably and rotatably

attached to the front upper mount 10 by a pivot pin 64, which has a flanged upper head 65, a shank portion 66., a tapered lower tip 67, a spring-loaded retaining ball 68 and a release button 69. Now turning attention to the front lower portion of the engine 14, Figure 9 shows a front lower mount 75 generally in shape of an A-frame, with inclined side tubular members 76 attached to a cylinder 77 so that the axes of the side tubular members 76 are coplanar with the axis of the cylinder 77. The lower ends of the side tubular members 76 are attached to pivot tubes 78 so that the axes of the pivot tubes 73 coincide and are coplanar with the axes of the side tubular members 76, and are perpendicular to the axis of the cylinder 77. Inserted into each end of the pivot ^• tubes 78 are bearings 79 having flanges 80. Brackets 81 are each formed by a right angular portion 82 and by triangular portions 83 attached perpendicularly to each end of the right angular portions 82, with one side of each of the right angular portions 82 having a hole 84. The brackets 31 are attached to the airframe 60 by bolts 85 so that the axes of the holes 84 coincide and form an angle of approximately 3° from normal with respect to the vertical centerplane of the aircraft. The acute angles formed by the right angular portions 82 each face inboard and are separated pairwise by the length of the pivot tubes 78 and flanges 80 of the bearings 79. The pivot tubes 78 are rotatably secured between pairs of the brackets 81 by bolts 86, nuts 87 and washers 88 through the holes 84.

As also seen in Figure 7, the cylinder 77 is bored at a relatively larger diameter 89 through its lower portion, a relatively smaller diameter 90 through

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its central portion and an intermediate diameter 91 through its upper portion so that the central portion forms an annular shoulder 92. A spherical bearing 93 is located in the upper portion 91 and rests on the shoulder 92 while being fixed by a retaining ring 94 which fits into an annular slot 95.

As seen in Figure 7, generally triangular tongue 96 of a thickness substantially equal to that of the tongues 53 is attached to the forward side of the cylinder 77 so that the tongue 96 is perpendicular to the axis of the cylinder 77 and forms an inboard angle of approximately 30° with respect to the vertical center- plane of the front lower mount 75.

Figure 9 also shows a mounting pin 110 which has a shank portion 111 of a diameter permitting it to -fit through the bearing 93. The shank portion has threads 112 by which the mounting pin 110 may be attached to the spherical bearing 93 by a nut 113, a washer 114 and a spacer tube 115 so that the mounting pin 110 may rotate about a generally vertical axis and also about horizontal and fore-aft axes- to a lesser extent. On the opposite end of the shank portion 111 is a larger diameter portion 113, having a chamfer 116. A generally triangular plate 117 having holes 113 at each vertex is attached normally to the mounting pin 110, and the mounting pin 110 is attached to the engine 14 by bolts 119 through the holes 113.

A lower strut 120 is shown generally in Figure 7. A first section 121 bored and tapped at 123 is more clearly shown in Figure 8,. and an end 122 is attached to S-shaped tongues 124 and 125. The tongues 124 and 125, each having a pivot hole (not shown), are separated by a gap wide enough to permit either the tongue 58 or the tongue 96 to be sandwiched

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in between the tongues 124 and 125. A second sec¬ tion 128, having a bore 129, is symmetrically attached to S-shaped tongues 130 and 131, each having a pivot hole (not shown), and the gap between the tongues 130 and 131 ideally the same as the gap between the tongues 124 and 125 so that lower strut 120 is endwise interchangable.

Figure 8 depicts an intermediate rod 132 having a male threaded end 133 which mates with the threads 123, an unthreaded end 134 whose diameter permits it to fit into the bore 129, and a tip 135 on unthreaded end 134 of a relatively smaller diameter. The tip 135 has a hole 136 whose axis is perpendicular to the axis of the lower strut 120 so that when the end 134 is inserted into bore 129, a cotter pin (not shown) may be placed through the hole 136 to prevent sep¬ aration of ^' the parts of ^■ the lower strut 120. A central portion 138 of the intermediate rod 132 has a diameter larger than either of the ends, and has parallel flattened faces 139 which are separated by a distance which permits the use of an open-end wrench to adjust the length of the lower strut 120 by way of the threads 133. For lower strut 120 to be installed, either of its ends may be attached to the tongue 96 by ^' a pivot pin 59, with the remaining end attached ^' to the lower strut bracket 54 by one of the pivot pins 62.

Shifting attention to the rear portion- of the aircraft engine 14, a rear mounting ring is seen gen¬ erally in Figure 3 at 140. A C-shaped tube 141 generally encircles the rear of the engine 14, with an inboard bracing tube 142, having angled ends 143 attached planarly near ends 144 of the C-tube 141. Triangular gussets 145 are attached to the tubes 141 and

142. Mounting pads 143 are attached with an outboard

face 147 normal to the ends of C-tub 141 and are of a generally oblong shape, as shown more clearly in Figure 1.

As shown in Figure 2, an inboard face 149 of the pads 148 makes an angle of approximately 3° with respect t the outboard face 147, with the thickest and the thinnest portion of the pads 148 defining a line normal to the plane of the C-tube 141, the thinnest por¬ tions being at the aft end. Thus, when the mounting ring 140 is attached, the axis of the aircraft engine 14 makes an angle of approximately 3° with respect to the center line of the ^" aircraft. The rear mounting ring 140 is removably attached to the airframe 60 by bolts 150 located near each end of the pads 148 and oriented normal to the face 149. The pads 143 are oriented with respect to the plane of the C-tube 141 so as to form a right angle from lines bisecting their respective oolts 150, as shown more clearly in Figure 1.

Figure 4 depicts an outboard insert tube 151 having threads 152 attached to the C-tube 141 through a hole 153 so that the axis of the tube 151 lies in the plane of the C-tube 141. An outboard engine mount pin 154 has an inboard end 155 whose outside diameter is substantially the same but less than the inside diameter of the outboard insert tube 151, and an outboard end 156 having threads 157 which are secured by a washer 158 and a nut 159, and mate with the threads 152 of the tube 151. A tip 160 of the outboard end 156 is formed to be a hexagonal head and is of a size permitting use of a standard wrench. A safety wire hole 161 appears in the tip 160 and is perpendicular to the axis of pin 154. A bore 162 extends from a chamfer 163 into the threaded section 157. An outboard pin mount socket 164 of gen¬ erally trapezoidal shape has holes 165 at each vertex by

which socket 164 is attached to engine 14 by bolts 166. A collar 167 is attached normally to the socket 164 and permits the inboard end 155 of the pin 154 to be inserted. Also, as depicted in Figure 4, an inboard engine mount pin 169 has a rod portion 170 attached nor¬ mally to a generally trapezoidal plate 171 having holes 172 at each vertex. A tip 173, having a chamfer 174, projects through the plate 171 and is bored at 175. The other end of pin 169 forms a hemispherical tip 176 angled at approximately 12° from the axis of the pin 169, towards the relatively longer parallel side of the _. trapezoidal plate 171. The inboard engine mount pin 169 is 'oriented with the relatively longer parallel side of the trapezoidal plate 171 vertical, with the hemispherical tip 176 angled in the forward direction, towards the front of the engine 14. The inboard engine mount pin 159 is inserted through hole 177 in the C-tube 141 and is attached to the engine 14 by bolts 178. An engine mount pad 179 is of generally square shape, having holes 180 at each corner by which it is attached to the airframe 60 by studs 181, nuts 182 and washers 133, and also has a central hole 184 of a diameter larger than that of the hemispherical tip 176. A collar 185 is attached to the pad 179 at an angle towards* aft of approximately 15° from normal to the ver¬ tical centerplane, and has an inside diameter which permits the hemispherical tip 176 to. fit through the col¬ lar 185 and the central hole 184, and into a hole 186 in the airframe 60.

In the event of a crash, - the engine 14 would be subjected to considerable force in the forward direc¬ tion, however, this force is transmitted to the airframe 60 at several points, thereby permitting the

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engine 14 to remain in a firebox 137 formed by the air¬ frame 60 on the fore, aft, inboard side, upper side and lower side of the engine and by an access door (not shown) . First the engine 14 is directly connected to the inboard engine mount pin 169, whose hemispherical tip 176 projects through the collar 135 of engine mount pad 179 into the hole 186 of the airframe 60. Thus, force on the engine 14 in the forward direction would be transmitted to the airframe 60 directly from inboard engine mount pin 169 and indirectly by way of engine mount pad 179. Further, any movement by the engine 14 and the inboard engine mount pin 169 in the forward direction would cause hemispherical tip 176 to move deeper into the hole 186 due to the forward angle of the tip 176 and rearward angle of the collar 185, thus pro¬ viding an even more solid connection between the ^■ engine 14 and the airframe 60. Second, the engine 14 is connected to the outboard engine ^' mount pin 154 so as to transmit forward forces to the rear mounting ring 140, and hence to the airframe 60, by way of the bolts 150 through the pads 148.

In order to utilize the swing away feature of the engine mount, thereby facilitating servicing of the rear portion of the engine, it is first necessary to install the longer and shorter upper struts 21 and 38 by way of the pivot pins 62 to the first and second upper strut brackets 52 and 53, and by way. of two of the pivot pins 62 to the tongue 18. Similarly, the lower strut 120 is installed by the pivot pin 59 to the tongue 96, and to the lower strut bracket 54 by one of the pivot pins 62. Figures 1 and ^~ 2 show the struts 21 and 38 installed in this manner. Next, the rear portion of the engine 14 is disconnected from the drive- shaft 188, and in a similar manner other disconnections

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may be made as required by the specific engine connec¬ tions being utilized. The four bolts 150 which attach the rear mounting ring 140 to the airframe 60 are next removed. The engine is now ready to swing out of the firebox 187 by way of an engine service portal 189 through an angle of approximately 50°, as more clearly shown in Figure 2.

The engine 14 is primarily supported by the front lower mount 75 and is allowed to rotate due to the spherical bearing 93. After the swing-out procedure and during servicing, the lower strut 120 prevents any fore- aft or lateral motion of the front lower mount 75. Simi¬ larly, the upper struts 21 and 38 prevent the engine 14 from moving laterally or in a fore-aft direction, and also prevent any rotation of the engine 14 except that about the axis of the spherical bearing 93.

It is noted that flexible fuel and oil lines remain connected during the swing out procedure as do hydraulic and electrical connections. When the engine 14 is in its swung out configuration, the servic¬ ing of the aft portion of the engine is greatly facilitated so that the fuel nozzle, igniter plugs, bleed valve hot sections are most easily accessible.

To move the engine 14 from its swung ou con¬ figuration back into the firebox 187, the engine 14 is swung in through the service portal 189, the rear mounting 140 is reattached to the airframe 60 by the bolts 150, the driveshaft 138 is reconnected to the engine 14 and the upper struts 21 and 38, and the lower strut 120 is disconnected and removed. The engine 14 is thus mounted for flight.

The present invention having been described in its preferred embodiment, it is clear that it is sus¬ ceptible to numerous modifications and embodiments with¬ in the ability of those skilled in the art and without the exercise of the invention faculty. Accordingly, the scope of the present invention is defined by the scope of the following claims.

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