Thrust reverser door with spring biased movable external panel

A thrust reverser is disclosed for an aircraft jet engine having a cowling with an outer surface and at least one reverse thrust opening, the thrust reverser including a thrust reverser door assembly movable with respect to the cowling between a forward thrust position, in which the reverse thrust opening is uncovered, and a reverse thrust position in which the thrust reverser door uncovers the reverse thrust opening. The thrust reverser door assembly includes an inner structure, an external panel movably connected to the inner structure and one or more resilient devices acting on the inner structure and the external panel to bias the external panel toward the inner structure such that, when the thrust reverser door is in the forward thrust position the external panel is displaced away from the inner structure by contact with the cowling such that an outer surface of the external panel is substantially flush with the outer surface of the cowling.

BACKGROUND OF THE INVENTION 
The present invention relates to a thrust reverser door with a movable 
external panel to prevent misalignment between the thrust reverser door 
and the cowling opening during engine operation. 
Turbofan-type turbojet engines are well known in the art and typically 
comprise a fan at the front of the turbojet engine which directs a flow of 
bypass air through a duct bounded by the engine cowling on the inside and 
a fan cowling on the outside. The generally annular duct bounded by the 
engine cowling and the fan cowling may channel both the bypass flow and 
the primary exhaust gas flow downstream from the turbojet engine, or may 
channel only the bypass flow. 
In aircraft on which the turbojet engine is mounted outside of the airframe 
structure, the fan cowling and the engine cowling are configured to form 
boundaries of the bypass flow duct and to provide aerodynamic outer 
surfaces to reduce drag. 
FIGS. 1 and 2 illustrate a known pivoting door-type thrust reverser 
associated with the cowling of a turbofan-type turbojet engine. As 
illustrated in FIG. 1, the upstream portion of the cowling which defines 
the outer limits of the bypass flow duct and which is generally 
concentrically arranged about the turbojet engine (not shown) is 
designated as 1 and generally comprises an external cowling panel and an 
internal cowling panel interconnected by a frame 6. The outer surface of 
the external cowling panel has an aerodynamic surface over which the air 
external to the engine passes during aircraft flight. The inner surface of 
the inner cowling panel defines the outer boundary of the bypass flow duct 
15 through which the bypass flow air passes from left to right as viewed 
in FIG. 1. 
The cowling also comprises a thrust reverser, illustrated generally at 2, 
and a downstream cowling portion 3. The thrust reverser 2 comprises a door 
7 pivotally attached to the cowling so as to pivot about transverse axis 
17 such that it is movable between a closed, forward thrust position, 
illustrated in FIG. 1, and an open, reverse thrust position in which the 
forward end (towards the left as viewed in FIG. 1) of the thrust reverser 
door 7 is moved outwardly from the cowling, while a rear portion is moved 
inwardly into the bypass flow duct airstream so as to redirect at least a 
portion of the bypass flow through an opening in the cowling in a 
direction that has a reverse thrust component. 
An actuator 8 for moving the door 7 between its forward thrust and reverse 
thrust positions may comprise a cylinder extending through and mounted to 
the frame 6, and having an extendable and retractable piston rod connected 
to the thrust reverser door 7. 
The thrust reverser door 7 has an outer door panel 9 and an inner door 
panel 11 joined together by an internal structure. The forward end of the 
door 7 may have a deflector 13 to maximize the efficiency of the thrust 
reverser when the door 7 is in the reverse thrust position. When the door 
is in the forward thrust position, as illustrated in FIG. 1, the outer 
door panel 9 is substantially flush with the external surfaces of the 
upstream panel and the downstream cowling portion 3. The inner face 11 
tapers toward the outer surface 9 at the forward end of the door 7, 
forming a cavity 16 when in the forward thrust position. 
As illustrated in FIG. 2, a plurality of thrust reverser doors 7 may be 
incorporated into the cowling, such doors being circumferentially spaced 
around the periphery of the cowling. Longitudinal beam portions 18 extend 
axially between forward part 4 and rear part 3 of the cowling between 
adjacent thrust reverser doors 7 to provide structural rigidity to the 
cowling and to provide pivot mounting points for attaching the doors 7 to 
the cowling. U.S. Pat. No. 3,605,411, and French Patents 1,482,538 and 
2,030,034 illustrate typical, known thrust reversers. 
It is known to utilize one linear actuator per thrust reverser door affixed 
to the cowling and the thrust reverser door to move the door between the 
forward and reverse thrust positions, as illustrated in the aforementioned 
French Patent 1,482,538. 
The thrust reverser disclosed in U.S. Pat. No. 3,605,411 has a forward 
deflector which enables the inner surface of the thrust reverser door to 
provide continuity to the outer boundary of the airflow duct when the 
thrust reverser is in the forward thrust position. As is also disclosed in 
French Patent 2,618,853, the deflector is masked to optimize engine 
performance when the thrust reverser is in the forward thrust mode. 
As disclosed in French Patent 2,680,547, the deflectors may be configured 
to orient the flow of the reverse thrust gases, such control being also in 
conjunction with the shape of deflection edges on the opening through the 
cowling through which the reverse thrust gases flow. 
In all of the above mentioned thrust reversers, the thrust reverser doors 
comprise an integral structure with the portion forming the external 
surface of the thrust reverser door (when in the forward thrust position) 
integrally joined to an inner structure. Seals are typically located at 
the juncture of these two structures. While generally satisfactory, such 
integral thrust reverser doors may create problems during aircraft flight 
since the pressure within the gas flow duct 15 is higher than the ambient 
air pressure surrounding the cowling. As a result of this pressure 
differential, the thrust reverser door is stressed and may undergo 
geometric deformations. Such deformations may cause gaps between the 
exterior surface of the integral thrust reverser door and the cowling 
edges defining the reverse thrust opening that seriously degrade 
aerodynamic performance of the cowling. 
SUMMARY OF THE INVENTION 
A thrust reverser is disclosed for an aircraft jet engine having a cowling 
with an outer surface and at least one reverse thrust opening, the thrust 
reverser including a thrust reverser door assembly movable with respect to 
the cowling between a forward thrust position, in which the thrust 
reverser door assembly covers the reverse thrust opening, and a reverse 
thrust position in which the reverse thrust opening is uncovered. The 
thrust reverser door assembly includes an inner structure, an external 
panel movably connected to the inner structure and one or more resilient 
devices acting on the inner structure and the external panel to bias the 
external panel toward the inner structure such that, when the thrust 
reverser door is in the forward thrust position the external panel is 
displaced away from the inner structure by contact with the cowling such 
that an outer surface of the external panel is substantially flush with 
the outer surface of the cowling. 
A seal is interposed solely between the inner structure and the surrounding 
cowling such that pressure differential forces act only on the inner 
structure which is allowed to deflect and deform relative to the external 
panel without causing the external panel to be displaced from the cowling, 
thereby avoiding the formation of gaps between the external panel and the 
cowling. Since the external surface of the external panel is substantially 
flush with the external surface of the cowling, such stresses acting on 
the inner door structure do not degrade the aerodynamic performance of the 
cowling. 
The resilient device connecting the separate and distinct external panel 
and inner structure may be a compression or tension coil spring, a leaf 
spring, or other known resilient devices.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 3 and 4 illustrate a first embodiment of the thrust reverser door 
according to the present invention. The thrust reverser door 7 comprises 
inner structure 22, external panel 23 and resilient devices 26. Although a 
plurality of resilient devices are illustrated, it is to be understood 
that, depending upon the particular design characteristics of each 
application, a single resilient device may be utilized without exceeding 
the scope of this invention. The resilient device interposed between the 
external panel 23 and the inner structure 22 isolates the external panel 
23 from the stresses exerted on the inner structure 22 by the pressure 
differential of the gases within duct 15 and the ambient atmospheric 
pressure. A seal 5 is attached solely to the inner structure 22 and bears 
against an adjacent portions of the cowling when the thrust reverser door 
7 is in the forward thrust portion, as illustrated in FIG. 3. 
In this embodiment, the resilient devices each comprise a compression coil 
spring 26 through which extends a guide stem 25 extending from an inner 
surface of the external panel 23. Each guide stem has an enlarged headed 
portion against which one end of the compression coil spring 26 bears, 
with the opposite end of the compression coil spring bearing against a 
portion of the inner structure 22. Resilient coil springs 26 bias the 
external panel 23 toward the inner structure 22. However, contact between 
a portion of the external panel 23 and a contact surface 27 formed on the 
cowling displaces the external panel 23 from the inner structure 22 when 
the thrust reverser door 7 is in the forward thrust position to create 
space 24. In this position, an external surface of the external panel 23 
is substantially aligned and flush (i.e. faired) with the external surface 
of the cowling 1 so as to form a faired aerodynamic outer surface 
therewith. Since the external panel 23 is displaced from the inner 
structure 22, deformation of the inner structure 22 caused by the pressure 
differential between ambient atmosphere and the gas pressure within duct 
15 will not cause displacement of the external panel 23 from its flush 
(i.e. faired) aerodynamic relationship with the external surface of the 
cowling 1. Since seal 5 is interposed between the inner structure 22 and 
the cowling 1, the pressure within the gas flow duct 15 does not act on 
the external panel 23. 
When the thrust reverser door is displaced toward the reverse thrust 
position, as illustrated in FIG. 4, the space 24 between the external 
panel 23 and the inner structure 22 is reduced, or eliminated, by the 
expansion of compression springs 26. Although springs are specifically 
disclosed in this embodiment, and in the remaining illustrated 
embodiments, it is to be understood that a vulcanized elastomer may be 
applied between the relatively moveable external panel 23 and the inner 
structure 22 to provide the same biasing forces as the disclosed springs. 
The external panel 23 may cover all of the outer surface of the thrust 
reverser door 7, or may form only a portion of the outer surface of the 
thrust reverser door 7. Also, the external panel 23 may be formed as an 
integral, one-piece element, or may be formed from several parts. The 
forward edge portion (towards the left as viewed in FIGS. 3 and 4) engages 
contact surface 27 formed on the cowling 1, in this particular instance 
the front frame 6. The contact surface may extend only adjacent to the 
portion of the cowling forming the front edge of the thrust reverse 
opening, may extend along opposite sides of the reverse thrust opening, or 
a combination of both. 
The external panel 23 may be fabricated from any type of material known to 
be suitable for aeronautical usage, such as, but not limited to, aluminum, 
titanium, thermoplastic, or composite material. 
Contact surface 27 may extend continuously along the portions of the 
cowling forming front and sides of the reverse thrust opening, or may 
comprise a plurality of individual contact spots. 
A second embodiment of the present invention is illustrated in FIGS. 5 and 
6. The structures and functions of the elements in this embodiment are 
identical with those of the previously described embodiment, except that 
leaf springs 30 are substituted for the compression coil springs 26. As 
can be seen, leaf springs 30 may be directly interposed between a lower 
surface of the external panel 23 and an outer surface 28 of the inner 
structure 22. Leaf springs 30 will bias the external panel 23 toward the 
inner structure 22 as in the previously described embodiment. Again, 
contact of the external panel 23 with the contact surface 27 will cause 
displacement of the external panel 23 away from the inner structure 22 
creating space 24 therebetween. External panel 23 is isolated from the 
pressures within the gas flow duct 15 by seals 5, as in the previously 
described embodiment. The present invention also encompasses the use of a 
single leaf spring. 
In the embodiment illustrated in FIG. 7, the external panel 23 is pivotally 
attached to the inner structure 22 at pivot 127, located, in this 
particular instance at rear portions of these elements. The pivot 127 may 
be centrally located across the transverse dimension of external panel 23 
and the inner structure 22, or a plurality of pivots 127 may be utilized 
spaced across these respective elements. The resilient device comprises a 
tension spring 26 connected between the external panel 23 and the inner 
structure 22 which biases the forward portion of the external panel 23 
toward the inner structure 22. In this embodiment, as in the previously 
described embodiments, as the external panel 23 contacts the contact 
surface 27, it will be displaced away from the inner structure 22 as the 
door 7 reaches its forward thrust position, to create space 24 
therebetween. Although a single tension spring 26 is illustrated, it is to 
be understood that a plurality of such springs may be utilized without 
exceeding the scope of this invention. 
FIG. 8 illustrates a positioning device that may be utilized with any of 
the previously described embodiments. To accurately position the external 
panel 23 relative to the cowling 1, a positioning protrusion 35 may extend 
from an inner surface of the external panel which engages a corresponding 
positioning hole formed in contact portion 36 of front frame 6. The 
engagement of the positioning protrusion with the positioning hole permits 
accurate placement of the external panel 23 relative to the cowling 1 and 
prevents any spurious displacement of the panel. 
The foregoing descriptions are provided for illustrative purposes only and 
should be construed as in any way limiting this invention, the scope of 
which is defined solely by the appended claims.