The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An aircraft is driven by several turbojet engines each housed in a nacelle. The nacelle has generally a tubular structure comprising an air inlet upstream of the turbojet engine, a middle section intended to surround a fan of the turbojet engine, a downstream section accommodating the thrust reverser means and intended to surround the combustion chamber of the turbojet engine and, usually ended by an ejection nozzle situated downstream of the turbojet engine.
This nacelle is intended to accommodate a double flow turbojet engine capable of generating through the blades of the rotating fan a hot air flow, coming from the combustion chamber of the turbojet engine, and a cold air flow which circulates outside the turbojet engine through an annular channel which is called bypass flow duct.
The thrust reverser device is, during the landing of the aircraft, intended to improve the braking ability thereof by redirecting forward at least a part of the thrust generated by the turbojet engine.
The structure of a thrust reverser comprises a reverser cowl displaceable between, on the one hand, a deployed position in which it opens a passage within the nacelle intended for the diverted air flow, and on the other hand, a retracted position in which it closes this passage.
At least two types of reverser cowl are known from the prior art.
The one-piece cowl, of an almost annular shape, is known, extending from one side to another of the pylon without interruption, and often referred to as “O-duct”, in allusion to the shell shape of such a cowl, as opposed to the “D-duct”, which in fact comprises two half-cowls each extending over half the circumference of the nacelle.
In a case like the other, it is the decline of the cowl by sliding along the rails integral with the pylon which allows to release the thrust reverser cascades, and thus to implement the thrust reverser function.
It is of course crucial that such sliding movement cannot occur in an unexpected manner: such opening would indeed be fatal in flight phase.
For these reasons, safety locks are provided at different locations of the thrust reverser to block the unwanted opening of the cowl.
In a “D-duct” thrust reverser, three safety locks for each half cowl are conventionally provided: two locks called primary directly acting on the two actuating cylinders of each half cowl, and a third lock called tertiary interposed between the beam said “6 hours” (that is to say disposed in the lower portion of the nacelle and on which the two half cowls are slidably mounted) and the half cowl concerned.
Independent power sources are provided for these locks so as to increase the reliability of the safety device.
The remote location of the third lock with respect to the two others also offers a gain of safety vis-à-vis a “duct burst” (explosion of a duct) or of a vane loss: in such a case, only one or two lock(s) could possibly be destroyed, but not all of them.
In an “O-duct” thrust reverser, there is by definition no 6 hours beam: So the implementation of a third lock as in a “D-duct” thrust reverser is not possible.
From the prior art, the French patent delivered and published under the number FR 2 952 908 is known, owned by the applicant, in which the protected present disclosure relates to means for locking the sliding of the thrust reverser “O-duct” cowl interposed between the pylon and said cowl.
FIGS. 1 and 2 illustrate such locking means according to the prior art.
An aircraft turbojet engine assembly comprises a pylon 1 to which a nacelle 3 is suspended, typically comprising an upstream fixed cowl 5 and a downstream movable cowl 7, the upstream and the downstream being understood with respect to the air flow flowing through the nacelle.
In the operating position of the nacelle, that is to say out of the maintenance operations on the turbojet engine, the downstream cowl 7 is slidably mounted between the position shown in FIG. 1, called “direct jet” position, and a position (not shown) slid towards the downstream of the nacelle, allowing to perform a thrust reverser function by rejection of a portion of the air passing through the nacelle upstream thereof.
The thrust reverser shown in FIG. 1 is of the “O-duct” type, that is to say the sliding cowl 7 forms a substantially annular one-piece part extending without discontinuity from a side 9a of the pylon 1 to the opposite side 9b of this pylon.
FIG. 2 relates to the area II of FIG. 1, the sliding cowl 7 having been removed for a better visibility.
The pylon 1 and, on the side 9a of this pylon, a short rail 11 and a long rail 13 can be seen.
The inner structure 15 surrounding the turbojet engine, defining bypass flow duct can also be seen.
The short rail 11 allows the sliding of the cascade vanes 17 of the air flow between a service position shown in FIG. 2, and a maintenance position wherein these cascades are slid to the rear end of the short rail 11, so as to allow the access to the turbojet engine.
The long rail 13 and its counterpart disposed in the other side of the pylon 1 allow the sliding of the cowl 7 between an operating position, comprising a direct jet position and a thrust reverser position in which it releases the cascade vanes 17, allowing the orientation of a portion of the air flow circulating in the bypass flow duct to the front of the nacelle, and a maintenance position (not shown).
A locking device 19 is mounted inside the pylon 1. This device allows providing the maintaining of the cowl in a closed position, that is to say corresponding to an operation of the nacelle in direct jet mode. A hatch 21 formed on the side 9a of the pylon 1 allows to have access to the locking device.
The locking device is, according to the state of the art, and as illustrated in FIGS. 1 and 2, enclosed inside a hatch made in the wall of the pylon to which the nacelle and turbojet engine are fastened.
Such an arrangement has several drawbacks.
First of all, the form of a hatch in the pylon requires to locally cut a portion of the flank of the pylon, which affects the structural strength of said pylon.
Then, during maintenance operations on the turbojet engine, the locking device must be inhibited in order to be able to have access to the turbojet engine. It is therefore obligatory to dismount this hatch for each maintenance operation, which greatly increases the time of access to the engine.
Thus, there is a need for disposing a tertiary lock for a one-piece cowl of thrust reverser, the inhibition of which can be manually accomplished by an operator from the outside the cowl, on the one hand without having to dismount any hatch, and on the other hand without affecting the structural strength of the pylon.