Patent Application
20050082423
The following disclosure relates generally to aircraft structures and, more particularly, to aircraft structures for attaching engines and other objects to aircraft wings.
Many conventional transport aircraft have wing-mounted engines. One such aircraft is illustrated in
An inboard side load clevis 234a and an outboard side load clevis 234b pivotally connect an aft portion of the engine strut 110 (shown schematically) to the inboard side load fitting 224a and the outboard side load fitting 224b, respectively. Additionally, two side load links 236 extend between the aft portion of the engine strut 110 and the center side load fitting 225. An upper pitch strut 231 extends forward from the pitch load fittings 221 and is coupled to a forward portion of the engine strut 110. A lower pitch strut 232 similarly extends forward from the lower pitch load fitting 222 and is coupled to a lower-aft portion of the engine strut 110.
The engine 106 transmits primary structural loads in flight as a result of its weight and propulsive capability. These primary loads can include pitch loads PL acting about a lateral axis 241, and side loads SL acting along the lateral axis 241. In general, the pitch loads PL are transferred to the wing 104 by the combination of the upper pitch strut 231 and the lower pitch strut 232. The side loads SL from the engine 106 are typically transferred to the wing 104 by the side load fittings 224 and the center side load fitting 225. The two pitch struts 231, 232 together with the two side load fittings 224 provide a measure of redundancy; if one of the two pitch struts or a related joint fails, the other pitch strut can adequately carry the pitch load PL from the engine 106 to the wing 104.
Manufacturing the prior art engine support system 214 described above can be a time consuming and costly process. Each of the separate load fittings (i.e., the pitch load fittings 221, 222; the side load fittings 224; and the center side load fitting 225) must be precisely located relative to the others to accommodate interchangeability between different engine struts as engines are changed-out for servicing, etc. A typical method for locating these fittings with sufficient accuracy involves positioning the bare fittings on the wing 104 with an elaborate tooling fixture during build-up of the wing. After the fittings are fixed in position, the various attach points are align-bored to ensure adequate alignment. Bearings are then installed into each of the finished bores. Not only is the tooling for these operations expensive, but the additional time required to install these fittings can add significant cost to the manufacturing process of the wing.
The present invention is directed generally toward apparatuses and methods for attaching engines and other structures to aircraft wings. An aircraft system configured in accordance with one aspect of the invention can include a wing having a front spar and a rear spar forming a wing box. In this embodiment, the aircraft system can further include a unitary fitting fixedly attached at least proximate to the wing box, and a jet engine positioned proximate to the wing and structurally coupled to the unitary fitting. In flight, the unitary fitting transfers at least approximately all of the primary loads from the jet engine to the wing box.
The primary loads transmitted by the jet engine can include pitch loads and side loads. In another aspect of the invention, the unitary fitting can include a first portion having a first attach feature and a second portion having a second attach feature spaced apart from the first attach feature. The first attach feature can be coupled to the jet engine and configured to transfer at least a portion of the pitch loads from the jet engine to the wing box. The second attach feature can also be coupled to the jet engine and configured to transfer at least a portion of the side loads from the jet engine to the wing box.
A method for attaching a propulsive engine to an aircraft wing in accordance with a further aspect of the invention includes attaching a unitary fitting to the aircraft wing. The method can further include attaching the engine to an engine support structure and structurally coupling the engine support structure to the unitary fitting. The unitary fitting can be configured to transfer at least approximately all of the primary loads from the engine to the aircraft wing.
The following disclosure describes apparatuses and methods for attaching engines and other objects to aircraft wings. Certain details are set forth in the following description and in
Many of the details, dimensions, angles, and other features shown in the Figures are merely illustrative of particular embodiments of the invention. Accordingly, other embodiments can have other details, dimensions, and features without departing from the spirit or scope of the present invention. In addition, further embodiments of the invention may be practiced without several of the details described below.
In the Figures, identical reference numbers identify identical or at least generally similar elements. To facilitate the discussion of any particular element, the most significant digit or digits of any reference number refer to the Figure in which that element is first introduced. For example, element 320 is first introduced and discussed with reference to
In another aspect of this embodiment, the first portion 321 of the unitary body 323 includes at least a first attach feature 324a, and the second portion 322 includes at least a second attach feature 326a spaced apart from the first attach feature 324a. In the illustrated embodiment, the first portion 321 further includes a third attach feature 324b spaced apart from the first attach feature 324a, and the second portion 322 further includes a fourth attach feature 326b spaced apart from the second attach feature 326a. Each of the attach features 324 can include a pin bore 325. Each of the pin bores 325 can be configured to receive a structural attach pin, such as a first fuse pin 327a, for coupling a corresponding pitch strut 331 (identified individually as a first pitch strut 331a and second pitch strut 331b) to the support fitting 320. The pitch struts 331 extend at least generally forward from the support fitting 320 and are structurally attached to a forward portion of the engine strut 310 (
In a further aspect of this embodiment, the two pitch struts 331 transfer at least a portion of the pitch loads PL from the engine 306 to a wing box 316 (
In yet another aspect of this embodiment, each of the attach features 326 includes a pin bore 333. Each of the pin bores 333 can be configured to receive a structural attach pin, such as a second fuse pin 327b, for coupling a corresponding side load fitting 334 (identified individually as a first side load fitting 334a and a second side load fitting 334b) to the support fitting 320. The side load fittings 334 are fixedly attached to an aft portion of the engine strut 310. In this embodiment, the second attach feature 326a and the fourth attach feature 326b can transfer the thrust loads TL and at least a portion of the side loads SL from the engine 306 to the wing box 316 (
In a further aspect of this embodiment, the unitary body 323 also includes a fifth attach feature 346a and a sixth attach feature 346b positioned between the second attach feature 326a and the fourth attach feature 326b. In the illustrated embodiment, each of the attach features 346 includes a pin bore 343. Each of the pin bores 343 can be configured to receive a structural attach pin, such as a third fuse pin 327c, for coupling a corresponding side load link 348 to the support fitting 320. The side load links 348 are pivotally attached to the aft portion of the engine strut 310 and can transfer at least a portion of the side loads SL from the engine 306 to the wing box 316 (
In the foregoing embodiments, the unitary body 323 is manufactured from a single or integral piece of material. In other embodiments, however, the unitary body 323 can be manufactured from separate pieces of material that are fixed together into a single unit. For example, in one such embodiment, the unitary body 323 can be manufactured from two separate parts that are fixed together before installation on an aircraft wing. Thus, the term “unitary,” as used herein, refers to a structure that is either fabricated from a single piece of material or fabricated from two or more pieces of material that are fixed together as a unit before subsequent installation on an aircraft wing.
The particular configuration of the support fitting 320 illustrated in
Further, although the embodiment illustrated in
One feature of aspects of the invention described above with reference to
In another aspect of this embodiment, the unitary body 323 of the support fitting 320 can be machined from a metal casting. For example, in one embodiment, the unitary body 323 can be machined from a titanium casting, such as a Ti-6A1-4V HIP casting. One advantage of using a casting is that the machining required to finish the unitary body 323 is minimized because the majority of the exterior surfaces of the unitary body 323 remain in the “as cast” condition. In other embodiments, the unitary body 323 can be manufactured from various other materials suitable for aircraft applications. For example, in one other embodiment, the unitary body 323 can be machined from aluminum. In a further embodiment, it is expected that the unitary body 323 can be manufactured from a composite material, such as carbon fiber. In yet other embodiments, the unitary body 323 can be manufactured from other materials using other manufacturing processes.
Regardless of the type of material used to manufacture the unitary body 323, the unitary body 323 can be configured in such a way as to minimize the likelihood of a structural failure of one of the attach features (i.e., 324, 326, and 346) causing a structural failure of another attach feature. For example, in one embodiment, the unitary body 323 can include features to minimize or eliminate crack or fracture propagation from one attach feature to another. There are various known methods for arresting crack propagation in unitized fittings that can be employed in this context. One such method is to provide undercut portions or holes adjacent to each of the various attach features that are designed to terminate the crack and limit the structural failure to the one corresponding attach feature. In other embodiments, other suitable methods can be employed to prevent propagation of a structural failure.
In another aspect of this embodiment, the secondary pin bores 561 can be utilized to attach secondary structures to the wing 304 (
From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited, except as by the appended claims.
