Suspension system for a rotary wing aircraft engine

1. A system for suspending a rotor drive engine ( 21 ) to an aircraft airframe ( 26 ), the system comprising:

at least one device ( 10 ) for suspending the engine to the airframe, each device ( 10 ) including i) two attachment portions ( 13 , 17 ), a first of the two attachment portions for connecting the device to the engine and a second of the two attachment portions for connecting the device to the airframe, and ii) a deformable structure ( 20 ) lying between the two attachment portions ( 13 , 17 ), wherein,

the deformable structure ( 20 ) comprises a plurality of blades ( 37 , 38 ),

each suspension device further has a compression abutment ( 43 , 44 ) configured to limit an extent to which the suspension device can be shortened by a deformation of the deformable structure ( 20 ), and

each suspension device has a first extension abutment configured to limit an elongation of the device, the elongation by deformation of the deformable structure, to a first elongation value, and a second extension abutment configured to limit the elongation to a second elongation value,

wherein the second elongation value is greater than the first elongation value.

2. A system according to claim 1 , wherein each of the blades of the deformable structure ( 20 ) comprises at least one tuning-fork or U-shaped portion configured to be pinched under the action of compression forces thereby shortening the device.

3. A system according to claim 1 , in which the blades of the deformable structure form an elongate ring extending transversely relative to a longitudinal axis ( 12 ) of the device, and

the two attachment portions are mutually spaced apart along the longitudinal axis.

4. A system according to claim 1 , in which the deformable structure ( 20 ) has a longitudinal stiffness less than or equal to 1500 newtons per millimeter, and

the deformable structure ( 20 ) is essentially made of metal.

5. A system according to claim 1 , in which each suspension device further includes a pivot ( 15 , 18 ) in each of the two attachment portions, and

in which the two attachment portions are rigid.

6. A system according to claim 5 , in which each pivot ( 15 , 18 ) has the form of a spherical joint.

7. A system according to claim 6 , in which axes ( 60 , 61 ) of the spherical joints are orthogonal to a longitudinal axis ( 12 ) of the device which the axes ( 60 , 61 ) intersect, and

the axes ( 60 , 61 ) are orthogonal to a transverse axis ( 19 ) along which the blades ( 37 , 38 ) of the elastically-deformable structure extend.

8. A system according to claim 1 , in which the deformable structure interconnects the two attachment portions ( 13 , 17 ), and

said device further comprises means ( 45 , 46 ) for mutually guiding the two attachment portions in displacement along a longitudinal axis ( 12 ) of the device.

9. A system according to claim 8 , in which said mutual guidance means comprises i) a shaft or guide ( 46 ) and ii) an orifice or bore ( 45 ) slidably receiving the shaft or guide along the longitudinal axis ( 12 ).

10. A system according to claim 1 , in which each suspension device further includes a fusible structure ( 51 ) having a zone of weakness configured to enable activation of the second extension abutment ( 45 , 43 ).

11. A system according to claim 1 , comprising two devices ( 10 ) for suspending the engine to the airframe, and further comprising a hinged connection ( 25 , 27 ) with a gearbox ( 24 ) driven by the engine.

12. A system according to claim 1 ,

wherein each device has a first spherical joint ( 15 ) in the first attachment portion and a second spherical joint ( 18 ) in the second attachment portion, each device being fastened to the engine via the first spherical joint ( 15 ) in one of i) a vertical plane ( 30 ) containing the center of gravity ( 23 ) of the engine, and ii) the immediate proximity of said plane, and

wherein the device is fastened to the airframe via the second spherical joint ( 18 ) at a point such that a longitudinal axis ( 12 ) of the device can take up two slightly sloping positions disposed on opposite sides of said vertical plane.

13. A system according to claim 1 , wherein the extent to which the device is shortened extends in a direction along a longitudinal axis ( 12 ) of the device, and the elongation of the deformable structure extends in the direction along the longitudinal axis ( 12 ).

14. A system for suspending a rotor drive engine ( 21 ) to a rotary wing aircraft airframe ( 26 ), the system comprising:

at least one device ( 10 ) for suspending the engine to the airframe, each device ( 10 ) including a deformable structure ( 20 ) interconnecting two attachment zones ( 13 , 17 ) of the device, each attachment zone including a first pivot ( 15 ) for connecting the device to the engine and a second pivot for connecting the device to the airframe, and the structure ( 20 ) comprising two tuning-fork or U-shaped blades ( 37 , 33 ) configured to be pinched under the action of longitudinal compression forces thereby shortening the device, wherein,

the deformable structure ( 20 ) has a longitudinal stiffness that is less than or equal to 1500 newtons per millimeters, and

each suspension device includes a first extension abutment limiting an elongation of the device, the elongation by deformation of the deformable structure, to a first elongation value, and a second elongation device limiting the elongation to a second elongation value, the second elongation value being greater than the first elongation value.

15. A system according to claim 14 , in which the deformable structure ( 20 ) has a longitudinal stiffness that is less than or equal to 1500 newtons per millimeter.

16. A device ( 10 ) for suspending a rotor drive engine ( 21 ) to a rotary wing aircraft airframe ( 26 ), the device comprising:

first connecting means ( 15 ) for connection to the engine;

second connecting means ( 18 ) for connection to the airframe; and

a body ( 11 ) having a longitudinal axis ( 12 ) and a transverse axis ( 19 ), the body comprising:

a first rigid end portion ( 13 ) receiving the first connecting means,

a second rigid end portion ( 17 ) receiving the second connecting means,

a middle portion extending between the two end portions,

guiding means for mutually guiding the first and second rigid end portions in relative displacement in translation along the longitudinal axis, wherein,

the middle portion comprises i) an elastically deformable structure ( 20 ) extending along the transverse axis ( 19 ) and comprising two U-shaped blades ( 37 , 38 ) configured to be pinched to shorten the device along said longitudinal axis, ii) abutment means for limiting an amplitude of deformation of the deformable structure ( 20 ), and iii) energy absorbing means for absorbing energy by plastic deformation of a part of the middle portion,

the abutment means includes a first extension abutment and a second extension abutment, the first extension abutment limiting an elongation of the device along the longitudinal axis to a first elongation value, and a second extension abutment limiting the elongation of the device along the longitudinal axis to a second elongation value, the second elongation value being greater than the first elongation value, and

the energy absorbing means includes a fusible structure ( 51 ), having a zone of weakness and configured to enable activation of the second extension abutment ( 45 , 43 )

17. A device according to claim 16 ,

wherein, the first rigid end portion is of annular shape and surrounds a first spherical joint ( 15 ) for connecting the device to the engine, and

the second rigid end portion is of annular shape and surrounds a second spherical joint ( 18 ) for connecting the device to the airframe.