Aeronautics and astronautics – Aircraft power plants – Mounting
Reexamination Certificate
1999-02-04
2001-04-03
Swiatek, Robert P. (Department: 3643)
Aeronautics and astronautics
Aircraft power plants
Mounting
C248S554000
Reexamination Certificate
active
06209822
ABSTRACT:
DESCRIPTION
1. Technical Field
The invention relates to a device for attaching or hooking an aircraft engine to a strut fixed to a structure of the aircraft, such as a wing or a fuselage element.
More specifically, the invention relates to an attachment device for absorbing or taking up lateral and vertical thrust forces and the torque produced by the engine and which must be retransmitted to the aircraft by means of the strut.
2. Prior Art
Each of the engines is suspended or attached in lateral manner to a strut, which is itself respectively fixed beneath the wing or to the aircraft fuselage.
The attachment systems connecting engines to struts are generally formed from two or three separate attachment devices. One of these devices is responsible for taking up the lateral and vertical thrust forces and the engine torque, which are produced by the engine, in order to retransmit them to the aircraft by means of the strut.
In the prior art, the attachment devices responsible for the taking up of the lateral and vertical thrust forces and the engine torque are essentially constituted by a monolithic or one-piece fitting, which is substantially circular arc-shaped. This structure is fixed to the strut in its central portion and connected to the engine at each of its ends by a one-piece attachment part. An attachment device of this type is e.g. described in U.S. Pat. No. 4,044,973.
As a result of the monolithic or one-piece character of the fitting and the attachment parts, a failure of any random one of these parts is liable to cast into doubt the integrity of the overall attachment device, thus seriously affecting aircraft safety.
In order to eliminate this risk, certain improved attachment devices add to the previously described structure a supplementary connection between the central portion of the fitting and the engine. This supplementary connection has sufficient clearance to ensure that it does not work during the normal operation of the attachment device. However, it does function when any random element of said device fractures.
The improved attachment devices incorporating such a supplementary connection still suffer from a certain number of disadvantages.
Firstly, the supplementary connection is not generally dimensioned in order to comply with the regulations, which require such a connection to be able to function in a completely satisfactory manner for thousands of flying hours corresponding to the inspection interval defined by said regulations for the aircraft in question.
Moreover, this solution requires the provision of a third attachment point on the engine, which leads to a modification of the latter.
In reality, the supplementary connection introduced into certain improved attachment devices already in existence only constitutes a rudimentary safety connection or link, intended solely to enable the aircraft to return to the ground under minimum safety conditions.
Thus, this connection is unable to comply with new demands laid down by the certification authorities in connection with the integrity of the device.
DESCRIPTION OF THE INVENTION
The object of the invention is to solve in a reliable and durable manner the safety problems caused by existing aircraft engine attachment devices, but without leading to any modification to the engines.
In other words, the object of the invention is an aircraft engine attachment device, whose original design enables it to maintain its integrity and consequently does not bring into doubt the safety of the aircraft, in the case of a failure of any one of its components, without it being necessary to add a supplementary connection to the two connections normally connecting the fitting to the engine.
According to the invention, this result is obtained by means of a device for the attachment of an engine to a strut fixed to an aircraft, said device comprising a substantially circular arc-shaped fitting having a central part fixed to the strut and two end parts connectable to the engine by connecting means, characterized in that the central part and the end parts of the fitting are formed both in two elementary portions thereof, able to individually transmit to the strut the stresses produced by the engine, the fitting being solely connected to the engine by said connecting means, and each of them includes a holding part, which is non-working in normal operation, able to transmit said stresses in the case of the fracture of another part of said connecting means.
The two elementary portions of the fitting, which can be implemented in the form of a single part or in the form of two separate parts, ensure the redundancy of the part of the device constituted by the fitting.
Moreover, the holding part integrated into each of the two connections between the fitting and the engine, ensures the redundancy of these connections.
Thus, the sought objective is achieved, no matter what the nature of the possibly defective part and without any modification being required to the engine.
In a preferred embodiment of the invention, the two elementary portions of the fitting are constituted by two separate parts, connected to one another by fixing means distributed over the entire length of said parts.
The fixing means connecting the separate parts of the fitting can in particular comprise bolts passing through said parts.
Each of the elementary portions of the fitting is itself fixed to the strut by at least two tension screws. Thus, the sought redundancy is also obtained in the connection provided between each of the portions of the fitting and the strut.
In the preferred embodiment of the invention, each of the two connecting means comprises a shock absorber block, fixed to the engine by a tension screw system and penetrating a female fork formed in a corresponding end part of the fitting, a spindle traversing without clearance the shock absorber block and, on either side of the latter, flanks of said female fork, formed in each of the two elementary portions of the fitting.
The non-working holding part is then advantageously constituted by a plate, fixed between the shock absorber block and the engine by the aforementioned tension screws and connected to the two elementary portions of the fitting by a joint with clearance.
The joint with clearance is then preferably a hinge-type joint, including multiple forks formed on the two parts constituted by the holding part and the fitting, said multiple forks intersecting with clearance. A second spindle traverses the multiple forks and is fixed to one of the two parts and traverses the other with clearance.
According to another embodiment of the invention, the spindle connecting the shock absorber block to one of the two end parts of the fitting is a hollow, external spindle, traversed with clearance by an internal spindle forming the non-working, holding part.
In this case, three different variants can be envisaged.
According to a first variant, a plate having a U-shaped cross-section simultaneously surrounds the two elementary portions of the fitting, at each end part thereof including said female fork, said plate being fixed to the two elementary portions of the fitting, apart from said fork, by a series of bolts successively traversing the two elementary portions and, on the other side thereof, two flanges of said plate, the hollow, external spindle also traversing without clearance each of said plate flanges.
According to a second variant, two substantially planar plates are fixed on either side of each end part of the fitting, apart from said female fork, by a system of bolts successively traversing the two elementary portions of the fitting and, on either side thereof, said plates, the hollow, external spindle also traversing without clearance each of the plates.
Finally, according to a third variant, each of the elementary portions of the fitting has, at each end portion thereof, a separate female fork penetrated by a part of the shock absorber block, the two female forks and the two parts of the shock absorber block being traversed by said hollow, external spindle.
REFERENCES:
patent: 404497
Aerospatiale - Societe Nationale Industrielle
Burns Doane , Swecker, Mathis LLP
Swiatek Robert P.
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