Aeronautics and astronautics – Aircraft power plants
Reexamination Certificate
1999-12-14
2001-12-11
Jordan, Charles T. (Department: 3643)
Aeronautics and astronautics
Aircraft power plants
C244S05300R, C244S062000
Reexamination Certificate
active
06328258
ABSTRACT:
DESCRIPTION
1. TECHNICAL FIELD
The invention relates to an air intake structure usable on any type of aircraft engine or turbo-jet having an air intake.
In such a structure, the invention more specifically applies to the link between an air intake lip, a front reinforcing frame and an acoustic panel placed immediately behind the lip in the extension thereof.
By convention, the terms “front” and “rear” are used throughout the text using as the reference the front and rear of the engine.
Comparably, the terms “internal” and “external” are used throughout the text using for the reference the complete engine.
Conversely and still in accordance with convention, in the absence of a precision to the contrary, the terms “interior” and “exterior” are used to designated the position or orientation of parts with respect to the air intake structure considered in isolation.
2. PRIOR ART
As is very diagrammatically shown in perspective of
FIG. 1
, an aircraft engine comprises a central part
1
housing the actual engine and an annular part
2
, called a pod, coaxially surrounding the central part of the engine and defining therewith an annular or fan duct
3
. A fan, driven by the central part
1
of the engine, is placed at the inlet of the fan duct
3
.
The front part of the pod
2
constitutes an air intake structure
4
, whose function is in particular to ensure the aerodynamic flow of air on the one hand towards the fan duct
3
and on the other around the pod
As shown in section and on a larger scale in
FIG. 2
, which illustrates a first known method for implementing the air intake structure
4
, such a structure conventionally comprises on the side of the fan duct
3
, an air intake lip
5
, a front reinforcing frame
6
and an acoustic panel
7
.
In cross-section, the air intake lip
5
is in the form of a rearwardly open U. It forms the external envelope of the front part of the air intake structure. It ensures the splitting of the air between the portion penetrating the fan duct and the portion flowing around the pod.
The front reinforcing frame
6
is placed in the interior and to the rear of the air intake lip
5
. It ensures the mechanical strength of the front part of the pod and aids in maintaining shape and dimensioning. To this end, the front reinforcing frame
6
is fixed to the interior of the air intake lip
5
, on the side of the fan duct and the outside of the engine, e.g. by means of rivets (illustrated by mixed lines
8
).
The acoustic panel
7
forms the external envelope of the pod, to the rear of the air intake lip
5
and on the side of the fan duct
3
. Said panel has a structure able to attenuate the noise produced by the central part of the engine and in particular the fan. In practice, this structure is normally of the composite, sandwich type, i.e. the panel
7
integrates a honeycomb core. In the known assembly method illustrated in
FIG. 2
, the front part
7
a
of the acoustic panel
7
, which as no honeycomb core, is externally covered by the rear part
5
a
of the air intake lip
5
and fixed thereto by rivets (illustrated by mixed lines
9
).
In view of its front position, the air intake lip
5
is exposed to damage and deterioration, which can in particular be due to erosion as a result of the air flow entering the engine, rain, hail, particles present in the atmosphere, etc. It can also be a question of accidental damage due to flight impacts (birds) or ground impacts, during the taxying phase (throwing up of pebbles) or during handling.
In order to ensure maintenance, it is clear that the air intake lip
5
of an aircraft engine must be frequently dismantled. In order to facilitate interventions, it is desirable for such a dismantling to be performable easily and rapidly. Therefore maximum importance is attached to the method used for assembling the air intake lip, the front reinforcing frame and the acoustic panel.
In the known assembly method illustrated by
FIG. 2
, the air intake lip
5
is fixed on the one hand to the front reinforcing frame
6
and on the other to the acoustic panel
7
, without there being any link between frame and panel. Thus, on dismantling the air intake lip
5
by removing the rivets
8
and
9
, there is no longer any connection between the front reinforcing frame
6
and the acoustic panel
7
. Thus, the assembly loses all its rigidity, its dimensional references, etc.
To obviate this disadvantage, specific equipment and tools have been designed in order to restore from the outset a certain rigidity to the pod. However, the putting into place of such equipment, which surround the external structure of the air intake, causes heavy handling, which is very disadvantageous for the maintenance personnel. This also involves the equipment being present at the repair locations, which is also very disadvantageous.
FIG. 3
shows in section another known method for assembling the air intake lip
5
, the front reinforcing frame
6
and the acoustic panel
7
. In this case, the rear part
5
a
of the air intake lip
5
and the front part
7
a
of the acoustic panel
7
are placed end to end in an extension of one another. Each of these two parts is then fixed by rivets (respectively illustrated by mixed lines
8
and
9
) on a rear part
6
a
of the front reinforcing frame
6
, placed in the interior of parts
5
a
and
7
a
of lip
5
and panel
7
.
When this method is used, the dismantling of the air intake lip
5
takes place by removing the rivets
8
and does not eliminate the link provided by the rivets
9
between the acoustic panel
7
and the front frame
6
.
However, this method has the disadvantage of leaving uncovered the front end and leading edge of the acoustic panel
7
in the fan duct
3
. This front end of the panel
7
, as well as its leading edge, are consequently exposed to phenomena such as erosion, delamination, water introduction, etc. In view of the fact that the acoustic panel
7
is normally made from a composite material, this leads to a difficultly acceptable speeding up of damage to said panel.
DESCRIPTION OF THE INVENTION
The invention specifically relates to an air intake structure in which the link between the air intake lip, the front reinforcing frame and the acoustic panel is such that the disadvantages of the prior art methods are eliminated. In particular, the dismantling of the lip does not eliminate the link between the frame and the panel and the front end and leading edge of said panel are not exposed to the air flow in the fan duct.
According to the invention, this result is obtained by means of an air intake structure for an aircraft engine comprising:
an air intake lip with a rearwardly open U-shaped cross-section and having an internal, rear part,
a front reinforcing frame installed in the air intake lip,
an acoustic panel having a front part fixed to the front reinforcing frame by first fixing means in order to form a rigid assembly and
second fixing means, independent of the first fixing means, for fixing the internal, rear part of the air intake lip to said rigid assembly,
characterized in that the internal, rear part of the air intake lip covers the front part of the acoustic panel and the first fixing means.
In a first embodiment of the invention, the front part of the acoustic panel is placed in the extension of an internal, rear part of the reinforcing frame and the internal, rear part of the air intake lip is fixed on the one hand to the rear, internal part of the reinforcing frame and on the other hand to the front part of the acoustic panel by second fixing means.
In this case, the first fixing means advantageously comprise a plurality of linking or joining parts, which are circumferentially distributed about a longitudinal axis of the engine and overlap the rear, internal part of the front reinforcing frame and the front part of the acoustic panel within the structure. The first fixing means also comprise fixing members, such as rivets, linking the linking parts on the hand to the rear, internal part of the front reinforcing frame and on the other hand to the front part of
Aerospatial Natra
Burns Doane , Swecker, Mathis LLP
Jakel Kevin
Jordan Charles T.
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