GONDOLA FOR AN AIRCRAFT ENGINE

Description

TECHNICAL FIELD

[0001] The present invention relates to a nacelle for an aircraft propulsion system comprising at least one movable cowling and an engine assembly arranged to move said at least one movable cowling and having a connecting rod-crank system, an aircraft propulsion system comprising such a nacelle and an aircraft comprising at least such a propulsion system. PREVIOUS STATE OF THE ART

[0002] There Fig. 5 shows a prior art propulsion system 500. This propulsion system 500 is fitted to an aircraft and it classically comprises a core 502 surrounded by a nacelle 504 which forms among other things an aerodynamic surface around the core 502 and the propulsion system is generally fixed under a wing of the aircraft by a mounting mast 503.

[0003] The nacelle 504 has hoods 506 which are hinged mounted on the towing mast by means of hinges 508 and which are locked in the closed position by a locking system which locks the hoods 506 to each other at the level of a lower spar 510 integrated into each hood 506.

[0004] For maintenance reasons, it is necessary to be able to open the hoods 506 by rotating them around the axes of the hinges 508. To open a hood 506, the technician unlocks the locking system and lifts the hood 506, the reverse maneuver allows the hood 506 to be closed.

[0005] A 512a-b cylinder is installed to assist in opening a 506 hood.

[0006] In some arrangements (on the left of the Fig. 5 ), the cylinder 512a is mounted between the hood 506 and a core structure 502.

[0007] In other arrangements (on the right of the Fig. 5 ), the cylinder 512b is mounted between the hood 506 and a structure of the attachment mast 503.

[0008] The use of jacks can limit the opening angle of the hoods and it is desirable to find an arrangement that allows for a greater opening of the hoods.

[0009] In addition, with the prior art arrangements, the 512b cylinders are potentially subjected to high temperatures and the change of the core may be hindered by the presence of the 512a cylinders.

[0010] It is therefore desirable to find an arrangement that provides improvements.

[0011] US patent 4399966A describes a self-contained device comprising a motor-driven pump for pumping hydraulic fluid from a reservoir mounted on the motor, via a control circuit. The control circuit selectively routes the fluid to actuators associated with each hood section to move those sections to their desired positions. The hydraulic control circuit preferably includes solenoid-operated valves associated with each actuator, which can be actuated to selectively allow fluid to flow into and out of the actuators, as required, to open and close the hood sections. DESCRIPTION OF THE INVENTION

[0012] An object of the present invention is to provide a nacelle for an aircraft propulsion system which includes at least one movable cowling and an engine assembly arranged to move said at least one movable cowling and having a connecting rod-crank system.

[0013] To this end, a nacelle is proposed for an aircraft propulsion system, said nacelle having a longitudinal axis and comprising: at least one hood mounted articulated between a closed position and an open position around a hinge axis, a motor assembly having for each of said at least one hood, a movable drive shaft rotating around an axis of rotation globally parallel to the longitudinal axis, and for each drive shaft, a connecting rod-crank system, where one end of the crank is fixed to said drive shaft and where one end of the connecting rod is mounted articulated on the associated hood.

[0014] With this arrangement, the hood opening angle is improved. Indeed, since the use of prior art cylinders is limited by the ratio of cylinder length between the open and closed positions, mounting a prior art cylinder between a hood and a mast support structure, considering the surrounding environment and the cylinder's size, would not easily allow achieving the desired hood opening angle according to the invention. Furthermore, when this arrangement is shared between the port and starboard hoods, it saves space, weight, and costs for the aircraft. In addition, this arrangement reduces the time required for maintenance of the aircraft's propulsion system.

[0015] Advantageously, the motor assembly is located in the upper part of the nacelle. With this arrangement, the opening and closing of the nacelle hoods is independent of the motorization system, simplifying the removal of the core with the hoods installed around it. Indeed, it is no longer necessary to disconnect a cylinder and replace it with a tool configured to hold the hoods in the open position.

[0016] Advantageously, said motor assembly comprises a motor with a motor shaft parallel to the axis of rotation and for each drive shaft, a gear system having an input pinion fixed to the motor shaft and an output pinion fixed to the drive shaft, where the gear ratio of the gear system is greater than 1.

[0017] Advantageously, the motor is an electric motor.

[0018] Advantageously, the engine is a hydraulic engine.

[0019] Advantageously, for each drive shaft, the engine assembly includes a clutch system arranged between the drive shaft and the crank and capable of alternately taking a clutch position in which the clutch system secures the drive shaft and the crank and a disengagement position in which the clutch system disengages the drive shaft and the crank.

[0020] Advantageously, for each drive shaft, the motor assembly includes a position sensor arranged to detect the angular position of said drive shaft. Advantageously, for each drive shaft, the motor assembly includes stops limiting the rotational movement of the crank.

[0021] Advantageously, the engine assembly has for each of said at least one hood, a movable drive shaft rotating about an axis of rotation globally parallel to the longitudinal axis, and two connecting rod-crank systems, where one end of each crank is fixed to the drive shaft and where one end of each connecting rod is mounted articulated on the associated hood.

[0022] The invention also proposes a propulsion system for an aircraft comprising a core and a nacelle according to one of the previous variants surrounding the core.

[0023] The invention also proposes an aircraft comprising at least one propulsion system according to the previous variant.

[0024] Advantageously, the aircraft comprises at least one wing and one attachment mast, the propulsion system being attached to said wing by means of said attachment mast, and the engine and gear system are arranged in a protective box, said protective box being fixed under said attachment mast.

[0025] Advantageously, the aircraft comprises at least one wing and one mounting mast, the propulsion system being attached to said wing by means of said mounting mast, and the engine is arranged in said mounting mast. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The features of the invention mentioned above, as well as others, will become clearer upon reading the following description of an exemplary embodiment, said description being made in relation to the accompanying drawings, among which: there Fig. 1 is a side view of an aircraft comprising a nacelle according to the invention, the Fig. 2 is a schematic front view representation of a gondola according to the invention, the Fig. 3 is a perspective view of a motor assembly implemented in the nacelle according to the invention in the closed position for each hood, the Fig. 4 is a perspective view of the engine assembly of the Fig. 3 in the closed position for one of the hoods and in the partially open position for the other hood, the Fig. 5 is a schematic front view representation of a state-of-the-art gondola, the Fig. 6a is a schematic front view representation of a gondola according to another embodiment of the invention, the Fig. 6b is a schematic front view representation of a gondola according to another embodiment of the invention, the Fig. 6c is a schematic front view representation of a gondola according to another embodiment of the invention, the Fig. 7a is a schematic front view representation of a portion of a nacelle according to another embodiment of the invention, in the closed position for each hood, the Fig. 7b is a schematic front view representation of part of a gondola according to the Fig. 7a , in the open position for each hood, the Fig. 8a is a schematic front view representation of part of a nacelle according to another embodiment of the invention, in the closed position for the hood, the Fig. 8b is a schematic front view representation of part of a gondola according to the Fig. 8a , in the open position for the hood, and the Fig. 9 is a perspective view of a motor assembly of a gondola according to another embodiment of the invention. DETAILED EXPLANATION OF IMPLEMENTATION METHODS

[0027] In the following description, terms relating to a position are taken with reference to an aircraft in a forward position as depicted on the Fig. 1 , and where arrow F shows the direction of travel of the aircraft in flight.

[0028] There Fig. 1 shows an aircraft 10 comprising a fuselage 12 on either side of which is fixed a wing 14. Each wing 14 supports at least one propulsion system 50 by means of a mounting mast 16 fixed between a structure of the wing 14 and a structure of the mounting mast 16.

[0029] The motorization system 50 comprises a core 60 (shown in dotted lines on the Fig. 1 ) surrounded by a gondola 100 according to the invention.

[0030] In the following description, and by convention, X is called the longitudinal axis of the nacelle 100 which is parallel to the longitudinal axis of the aircraft 10 or roll axis, oriented positively in the direction of forward movement of the aircraft 10, Y is called the transverse axis which is parallel to the pitch axis of the aircraft 10 which is horizontal when the aircraft 10 is on the ground, and Z is called the vertical axis which is parallel to the yaw axis when the aircraft 10 is on the ground, these three directions X, Y and Z being orthogonal to each other.

[0031] The nacelle 100 has a vertical median plane P of symmetry which coincides with the vertical plane XZ and, in the embodiment of the invention presented in the Fig. 2 , the nacelle 100 has on either side of the vertical median plane P, a hood 102.

[0032] Each hood 102 takes the form of a half-cylinder so as to together form a cylinder surrounding the core 60.

[0033] The core 60, for example, takes the form of a turbofan engine with a fan at the front. The cowling 102 can then serve as the fan cowling or the cowling for the thrust reverser system.

[0034] Each hood 102 is hinged on a structure which can be either a structure of the drive system 50 or the mounting mast 16. The articulation of each hood 102 occurs around a front hinge axis 103 and it is movable between a closed position in which the hood 102 is tightened around the core 60 and an open position in which the hood 102 is moved away from the core 60. On the Fig. 2 , the port side hatch 102 is in the open position and the starboard side hatch 102 is in the closed position.

[0035] In the closed position, the two hoods 102 come together against each other, at the level of a lower spar 62 of each hood 102. Each hood 102 thus comes into contact with the lower spar 62 of the other hood 102, at the level of its own lower spar 62, which is, in the closed position, arranged at the level of the lower part of the nacelle 100, at 6 o'clock.

[0036] The hinge axes 103 are arranged in the upper part of each hood 102 and the hoods 102 are mounted hinged on the mounting mast 16 around the associated hinge axis 103.

[0037] To lock each hood 102 in the closed position, the platform 100 is equipped with locking systems accessible from outside the platform by a technician. Each locking system can take any form known to those skilled in the art and alternately assumes a locked position, in which it locks the associated hood 102 in the closed position, or an unlocked position, in which it does not lock the associated hood 102, which is then free to move from the closed position to the open position and vice versa. For redundancy, each hood 102 is equipped with at least two separate locking systems.

[0038] In the embodiment of the invention presented to the Fig. 2 There is a common engine assembly 104 for both hoods 102. Similarly, the Figs. 3 And 4show a motor assembly 104 allowing the two hoods 102 to be operated which are arranged on either side of the median plane P. A motor assembly 104 is arranged at a distance from the hinge axes 103 of the hood 102.

[0039] Of course, it is also possible to predict that there is one engine assembly 104 per hood 102. The Fig. 3 shows the engine assembly 104 in the closed position of the two cowlings 102 and the Fig. 4 shows the engine assembly 104 in the closed position for the hood 102 on the starboard side and in the open position for the hood 102 on the port side.

[0040] In general, the nacelle 100 comprises at least one hood 102 and an engine assembly 104, each of which has at least one hood 102, an actuator shaft 106 that is movable in rotation around an axis of rotation X' that is globally parallel to the longitudinal axis X, that is to say, within construction tolerances.

[0041] Thus, depending on the case, there is only one drive shaft 106 when there is only one hood 102 operated by the motor assembly 104 or two drive shafts 106 when there are two hoods 102 operated by the motor assembly 104, which is the case here.

[0042] Each motor assembly 104 is arranged to rotate each drive shaft 106 alternately in an opening direction to move the associated hood 102 from the closed position to the open position, and in a closing direction to move the associated hood 102 from the open position to the closed position. The opening direction is the opposite of the closing direction.

[0043] In the embodiment of the invention presented to the Fig. 3 For the port hatch, the opening direction is indicated by the '+' arrow and the closing direction by the '-' arrow. For the two actuating shafts 106, the directions are reversed.

[0044] To operate the motor assembly, a control unit is provided to control the rotation in one direction or the other and to stop rotation as needed. The control unit takes the form, for example, of a processor which may be supplemented by RAM (Random Access Memory), ROM (Read Only Memory) or Flash memory, a storage unit or a storage media reader ("STCK"), such as an SD card reader (Secure Digital) or an HDD (Hard Disk Drive), and a communication interface to communicate with the motor assembly 104.

[0045] For each drive shaft 106, i.e. for each hood 102 associated with the engine assembly 104, the nacelle 100 includes a connecting rod-crank system 108, with a crank 108a which is mounted on the drive shaft 106 and rotates with it around the axis of rotation X' and a connecting rod 108b.

[0046] The crank 108a has a proximal end 109a and a distal end 109b. The proximal end 109a of the crank 108a is fixed to the drive shaft 106. The connecting rod 108b has a proximal end 111a and a distal end 111b. The distal end of the connecting rod 108b is articulated on the cover 102 associated with the drive shaft 106, for example by a ball joint.

[0047] The distal end 109b of the crank 108a and the proximal end 111a of the connecting rod 108b are mounted articulated to each other, in particular by a pivot joint around an axis globally parallel to the longitudinal axis X.

[0048] The rotation of the crank 108a will thus cause a translational displacement of the connecting rod 108b and therefore a rotation of the associated hood 102 in one direction or the other.

[0049] With such an arrangement, it is therefore sufficient to control the motor assembly 104 to rotate the actuating shaft(s) 106 to open or close each hood 102 associated with a simple system and presenting a large opening angle.

[0050] In addition, the engine assembly or each engine assembly 104 is located in the upper part of the nacelle 100, i.e. at 12.00 o'clock and in the vicinity of the towing mast 16, i.e. at a distance from any possible thermal radiation from the core 60. The engine assembly is fixed directly to the towing mast 16, or to a structure itself fixed to the towing mast 16.

[0051] The motor assembly 104 here comprises an assembly 104a including an electric motor with a drive shaft parallel to the axis of rotation X' and a first gearbox, as well as a second gearbox 104b. The first gearbox is compact and has a high degree of meshing, and includes, for example, a gear system comprising planetary gear trains arranged in series. The second gearbox 104b includes, for each drive shaft 106 associated with the motor assembly 104, a gear system having an input pinion fixed to the first gearbox and an output pinion fixed to the drive shaft 106. The second gearbox may include a clutch or disengagement system arranged around the drive shafts 106. The electric motor of the assembly 104a is electrically powered by an electrical source and its rotation is controlled by the control unit.

[0052] To facilitate the movement of the hood 102, the gear ratio of the gear system of the first gearbox is greater than 1. The implementation of a gear system where the gear ratio is higher makes it possible to reduce the torque required to open and close the hood 102.

[0053] When there are two drive shafts 106 for a single electric motor, the gear system (of the second gearbox 104b) associated with each drive shaft 106 (via the second gearbox 104b) must be such that the rotation of the motor shaft in one direction corresponds to the opening direction for each drive shaft 106 and each hood 102 and such that the rotation of the motor shaft in the opposite direction corresponds to the closing direction for each drive shaft 106 and each hood 102.

[0054] The electric motor is thus positioned parallel to the longitudinal X axis to save space and, as shown on the Fig. 6a The electric motor can be placed in the 16-foot mounting mast for better protection, especially against heat.

[0055] As depicted on the Fig. 6b The electric motor can be positioned just below the hanging mast 16 and in this case, it can then be enclosed in a protective box 105 with the gear system to be better protected from the thermal radiation coming from the core 60. The protective box is here fixed under the hanging mast 16.

[0056] The protective box 105 can be an airtight enclosure to prevent thermal radiation from the core 60 from heating the electric motor or gear system. The protective box 105, encompassing the motor assembly 104, can be made of a flame-retardant material or a high-temperature resistant material, for example, titanium, and may also include a thermal protection layer arranged around the motor assembly 104. The protective box 105 advantageously extends the service life of the motor assembly, reduces the risk of potential failures within said motor assembly, and reduces the manufacturing costs and weight of said motor assembly, since it then becomes possible to use materials requiring lower temperature resistance than without the protective box 105.

[0057] As depicted on the Fig. 6c The motor assembly 104, i.e. the electric motor and the gear system, can be arranged in the attachment mast 16, the latter being, for example, extended downwards.

[0058] Depending on the position of the electric motor of assembly 104a relative to the first gearbox of assembly 104a, a mechanical offset system, such as a flexible shaft, can be put in place between the motor shaft and the input pinion which is then fixed to the motor shaft through this mechanical offset system.

[0059] In the embodiment of the invention described above, it has been assumed that both hoods 102 are moved simultaneously, but it may be necessary to operate only one of them. To this end, for each drive shaft 106, the motor assembly 104 includes a clutch system 110 arranged between the drive shaft 106 and the crank 108a. This clutch system 110 is controlled by the control unit and allows the drive shaft 106 and the crank 108a to be engaged or disengaged. The clutch system 110 may be electrically switched. This clutch system 110 can thus take alternately a clutch position in which the clutch system 110 connects the drive shaft 106 and the crank 108a and a disengagement position in which the clutch system 110 disconnects the drive shaft 106 and the crank 108a.

[0060] This clutch system 110 can also alternately assume four distinct positions: a first position where only one hood 102 is selected (for example, the port hood), a second neutral position where no hood 102 is selected, a third position where both hoods 102 are selected, and a final position where only the second hood 102 is selected (for example, the starboard hood). This advantageously reduces the number of motor assemblies 104 required to actuate each hood 102, and therefore the weight of such an actuation system.

[0061] Depending on one configuration, the clutch system 110 can be removed, and the motor assembly 104 is then configured to open and close the port and starboard hoods 102 simultaneously.

[0062] In the embodiment of the invention presented here, the clutch system 110 is mounted around the actuating shaft 106, but it could take another form. For example, the proximal end 111a of the connecting rod 108b may have an oblong through-hole configured so that, when the disengagement function is activated, the connecting rod 108b does not drive the cover 102, but the shaft passing through the oblong through-hole of the end 111a slides in said oblong through-hole, and when the clutch function is activated, the oblong through-hole closes to drive the cover 102. According to another example, the cover 102 may have an oblong through-hole in which a shaft connected to the connecting rod 108b is configured to slide in order to perform the disengagement function.

[0063] To know the position of each hood 102, and thus be able to stop the motor assembly 104 when necessary, for each drive shaft 106, the motor assembly 104 includes a position sensor which is arranged to detect the angular position of said drive shaft 106 and therefore of said associated hood 102.

[0064] For safety reasons and to prevent the cover 102 from moving below the closed position or beyond the open position, for each drive shaft 106, the motor assembly 104 includes stops 112a-b that limit the rotational movement of the crank 108a. There is a stop 112a that stops the crank 108a when it reaches the position corresponding to the closed position of the cover 102, and a stop 112b that stops the crank 108a when it reaches the position corresponding to the open position of the cover 102. The stops 112a and 112b are shown in the diagrams. Figs. 3 And 4as not related to elements present in the figures, for the sake of clarity of the drawings only.

[0065] The motor assembly 104 may also include braking means (not shown) for holding the cover 102 in the open position, or for preventing the cover 102 from closing, particularly in the event of a loss of power to the electric motor. These braking means can thus serve to hold the covers 102 in their open position, and / or to secure the covers in the event of a system failure. The invention has been described above for covers 102 surrounding the core 60 of the motor system 50. The invention can also be applied to other types of covers, and in particular to maintenance covers.

[0066] THE Figs. 7a et 7b represent a portion of a nacelle 100 comprising, on either side of the vertical median plane P of symmetry, a hood 102 as described previously, and a maintenance hood 202. The maintenance hood 202 is arranged around the lifting mast 16 and, in the open position, provides access to the lifting mast 16 for maintenance of the systems integrated therein. On the Fig. 7a , hood 102 and maintenance hood 202 are in the closed position, and on the Fig. 7b The cover 102 and the maintenance cover 202 are in the open position. For each maintenance cover 202, a motor assembly operates the opening or closing of the maintenance cover 202 and includes, among other things, an electric motor 204a, a gearbox, and a crank-connecting rod system 208, 208a, 208b. The electric motor 204a is here fixed to the mounting mast 16, and in particular to a side wall 16a of said mounting mast 16. Of course, other positions of the electric motor 204a are possible, and in particular said electric motor 204a can be arranged within the mounting mast 16, to save space. For the maintenance hood 202 engine assembly, it is possible to do without a protective box, since the maintenance hood engine assembly is subjected to lower heat fluxes than those that can come from the core 60.

[0067] For reasons of redundancy, the nacelle 100 can also be equipped, in addition to the motor assembly 104, for each hood 102, with a retaining system 304 fixed between the attachment mast 16 and the hood 102, and more precisely fixed under the attachment mast 16. The retaining system 304 shown in the Figs. 8a et 8b It takes the form of a retaining rod, also called a support rod or support arm. This retaining system 304 can be actuated between two states: a first state of closure of the hood 102, and a second state of opening the hood 102. Figs. 8a et 8b represent a nacelle 100 equipped with a support system 304, as well as an engine assembly 104, the hood 102 being in the closed position on the Fig. 8a and in an open position on the Fig. 8b This retaining system 304 is self-locking, meaning it automatically locks in its second state to secure the open position of the cover 102. This retaining system 304 is equipped with a means for unlocking its second state, which is located away from the mounting mast 16 and is therefore accessible to an operator. The unlocking means for the retaining system 304 can take the form of a locking handle (not shown in the figures) via a mechanical linkage to the lock on the retaining system 304.

[0068] During operation, the motor assembly 104 allows the hood 102 to be opened, which causes the holding system 304 to be deployed. The holding system 304 automatically locks in the open position of the hood 102, which allows the motor assembly 104 to be unloaded. An operator can then perform the necessary maintenance operations, the holding system 304 allowing the hood 102 to be held in its open position. For reasons of redundancy, for each hood 102, the connecting rod-crank system can be doubled and thus the engine assembly 104 has for each hood 102, a drive shaft 106 mobile in rotation around an axis of rotation X' globally parallel to the longitudinal axis X, and two connecting rod-crank systems 108, 308, where one end of each crank 108a is fixed to the drive shaft 106 and where one end of each connecting rod 108b, 308b is mounted articulated on the associated hood 102.

[0069] More specifically, as illustrated on the Fig. 9There is a motor assembly 104, which includes an assembly 104a consisting of an electric motor with a drive shaft and a first gearbox with a first input gear fixed to the drive shaft, and a first output gear. The motor assembly 104 also includes a second gearbox 104b with a second input gear fixed to the first output gear of the first gearbox, and a second output gear fixed to a central gear, which is fixed to and traversed by a drive shaft 106. For each hood 102, there is a single drive shaft 106, which passes through the second gearbox 104b, and a single gear system per drive shaft 106. The second gearbox 104b is arranged below the assembly 104a, but this arrangement is not restrictive and depends on the available space.The drive shaft 106 extends on either side of the second gearbox 104b, along the longitudinal axis X, so as to allow the opening or closing of the hood 102 to be actuated at two points located (along the longitudinal axis X) from the hood 102. The motor assembly 104 thus comprises a single electric motor, a single first gearbox, and a single second gearbox 104b configured to drive the actuating, for each hood 102, of two connecting rod-crank systems 108, 308 simultaneously. The motor assembly 104, which is common to both hoods 102, includes a clutch / disengagement system in the second gearbox 104b for each gear system of the drive shaft 106, that is, for each of the two gear systems of the two drive shafts 106.In other words, the electric motor and the first and second gearboxes drive two drive shafts 106 which can be decoupled from each other and disengaged independently of each other, in order to decouple the opening and closing of the hoods 102. Each drive shaft 106 is connected to two crank-connecting rod systems 108, 308, which allows only four crank-connecting rods for the nacelle 100.

[0070] The ends of each connecting rod 108b, 308b are hinged to the same associated hood 102, spaced apart along the longitudinal axis X. For example, the end of connecting rod 108b is attached to the hood 102 at a front point, while the end of connecting rod 308b is attached to the hood 102 at a rear point. Each hood 102 is thus hinged to the mounting mast 16 at two distinct points, meaning that the forces associated with the hinge of the hood 102 are carried by two separate load paths. With this configuration, there are at least two connecting rod-crank systems per hood, or four connecting rod-crank systems per nacelle.

[0071] Advantageously, this arrangement does not require a holding system (such as the 304 holding system). Advantageously, this arrangement is fully automatic and does not require manual unlocking, including locking means for a holding system. Furthermore, the two load paths (the two connecting rod-crank systems) are automatically synchronized for opening or closing the hoods.

[0072] Depending on one configuration, the electric motor of the assembly 104a is powered by electrical energy from the aircraft's electrical network (itself connected to a local ground electrical network), or by a battery, for example, which can be located remotely from the mounting mast 16, said battery being either in the aircraft or on the ground.

[0073] As an alternative to the electric motor as described above, the motor assembly 104 may include a hydraulic motor powered by hydraulic energy from an aircraft cooling system, such as an air conditioning system, or by an external hydraulic energy source, which may be located away from the towing mast 16.

Claims

1. Nacelle (100) for a propulsion system (50) of an aircraft (10), said nacelle (100) having a longitudinal axis (X) and including: - at least one cowl (102) pivotally mounted between a closed position and an open position about a hinge axis (103), - a motor assembly (104) having, for each of said at least one cowl (102), an actuating shaft (106) moveable in rotation about a rotation axis (X') substantially parallel to the longitudinal axis (X), and - for each actuating shaft (106), a crank-and-connecting rod system (108), in which one of the ends of the crank (108a) is secured to said actuating shaft (106) and in which one of the ends of the connecting rod (108b) is pivotally mounted on the associated cowl (102).

2. Nacelle (100) according to Claim 1, wherein said motor assembly (104) is arranged at the top of the nacelle (100).

3. Nacelle (100) according to either of Claims 1 and 2, wherein said motor assembly (104) includes a motor with a drive shaft parallel to the rotation axis (X') and, for each actuating shaft (106), a gear system having an input pinion secured to the drive shaft and an output pinion secured to the actuating shaft (106), in which the gear ratio of the gear system is greater than 1.

4. Nacelle (100) according to Claim 3, wherein said motor is an electric motor.

5. Nacelle (100) according to Claim 3, wherein said motor is a hydraulic motor.

6. Nacelle (100) according to one of Claims 1 to 5, wherein, for each actuating shaft (106), the motor assembly (104) includes a clutch system (110) which is arranged between the actuating shaft (106) and the crank (108a) and can alternately assume an engaged position in which the clutch system (110) couples the actuating shaft (106) and the crank (108a) and a disengaged position in which the clutch system (110) decouples the actuating shaft (106) and the crank (108a).

7. Nacelle (100) according to one of Claims 1 to 6, wherein, for each actuating shaft (106), the motor assembly (104) includes a position sensor arranged to detect the angular position of said actuating shaft (106).

8. Nacelle (100) according to one of Claims 1 to 7, wherein, for each actuating shaft (106), the motor assembly (104) includes stops (112a-b) limiting the rotational movement of the crank (108a).

9. Nacelle (100) according to one of Claims 1 to 8, wherein the motor assembly (104) has, for each of said at least one cowl (102), an actuating shaft (106) which is moveable in rotation about a rotation axis (X') substantially parallel to the longitudinal axis (X), and two crank-and-connecting rod systems (108, 308), in which one of the ends of each crank (108a) is secured to the actuating shaft (106) and in which one of the ends of each connecting rod (108b, 308b) is pivotally mounted on the associated cowl (102).

10. Propulsion system (50) for an aircraft (10) including a core (60) and a nacelle (100) according to one of Claims 1 to 9 surrounding the core (60).

11. Aircraft (10) including at least one propulsion system (50) according to Claim 10.

12. Aircraft (10) according to Claim 11, when Claim 10 is dependent on at least Claim 3, including at least one wing (14) and a mounting pylon (16), the propulsion system (50) being fastened to said wing (14) by means of said mounting pylon (16), wherein the motor and the gear system are arranged in a protective housing, said protective housing being fastened under said mounting pylon (16).

13. Aircraft (10) according to Claim 11, when Claim 10 is dependent on at least Claim 3, including at least one wing (14) and a mounting pylon (16), the propulsion system (50) being fastened to said wing (14) by means of said mounting pylon (16), wherein the motor is arranged in said mounting pylon (16).