Undercarriage with anticrash and antiresonance skids for a rotary wing aircraft, and an aircraft

1. An undercarriage for a rotary wing aircraft having a carriage with a force take-up structure, the undercarriage comprising:

two landing skids extending in a longitudinal direction below the carriage and spaced apart laterally from a midplane of the carriage, each skid adapted to absorb a fraction of energy that is applied thereto during a landing under normal conditions by deforming elastically;

a pair of transverse elements connecting the two landing skids and disposed in a plane perpendicular to the longitudinal direction of the undercarriage and adapted to absorb energy that is applied thereto during a landing under normal conditions by deforming elastically, the pair of transverse elements including a front transverse element and a rear transverse element spaced apart from each other in the longitudinal direction;

a connection system connecting the undercarriage to the force take-up structure of the aircraft and absorbing energy that is applied thereto during a crash by deforming plastically in a controlled manner, the connection system including a pair of front buckling struts and a pair of rear buckling struts, each strut of the pair of front buckling struts, and the pair of rear buckling struts being plastically deformable in a crash, each of the buckling struts being coupled to each of the transverse members with a bottom hinge; and

assembly means providing statically-redundant coupling between the force take-up structure of the aircraft and the pair of transverse elements, the assembly means located along the pair of transverse elements between each of the front pair of buckling struts and between each of the rear pair of buckling struts, the assembly means having at least one statically-redundant fastener member,

wherein each of the of transverse elements includes an endpiece section that extends transversely on either side of the undercarriage an offset distance outwards transversely and downwards from the bottom hinge of the pair of buckling struts.

2. The undercarriage according to claim 1 , wherein:

the pair of rear buckling struts and the pair of front buckling struts are provided with bottom and top hinges forming part of the assembly means, said bottom and top hinges being disposed with a predetermined amount of overhang outwards transversely and downwards relative to the statically-redundant assembly means.

3. The undercarriage according to claim 1 , wherein:

each skid is adapted to absorb a fraction of the energy which is applied thereto during a landing under normal conditions by deforming elastically essentially or completely in twisting; and

at least one of the front and rear transverse elements absorbing the energy which is applied thereto during a landing under normal conditions by deforming elastically or completely in bending.

4. The undercarriage according to claim 1 , wherein said pair of rear buckling struts includes a ball joint assembly and the assembly means comprises at least one front statically-redundant fastener member.

5. The undercarriage according to claim 1 , wherein the said front buckling struts include a ball joint assembly and the assembly means comprises at least one rear statically-redundant fastener member.

6. An undercarriage according to claim 1 , wherein the pair of rear buckling struts and the pair of front buckling struts of the connection system are arranged in such a manner as to deform in the plastic range by buckling at constant force.

7. The undercarriage according to claim 1 , wherein at least one of a pair of rear and front buckling struts of the connection system is arranged in such a manner as to deform in the plastic range by buckling in the event of the forces becoming greater than a predetermined threshold corresponding to a hard landing or a crash landing, with said pair of struts being arranged so that the deformation remains elastic and is free from buckling or non-existent so long as the forces remain below said predetermined threshold.

8. The undercarriage according to claim 1 , wherein each of the buckling struts of at least one of said front and rear pair of said buckling struts has a deformable body, and a section that is polygonal.

9. The undercarriage according to claim 1 , wherein a buckling strut deformable body in at least one of said front and rear pair of said buckling struts is made essentially of steel or of a composite material including glass or carbon fibers.

10. The undercarriage according to claim 1 , wherein the at least one pair of said front and rear buckling struts is provided with bottom and top hinges, wherein at least one of the hinges comprises a ball joint.

11. The undercarriage according to claim 10 , wherein at least one ball joint of a buckling strut hinge presents has a pivot center that is off-center transversely from an axis of the corresponding buckling strut.

12. The undercarriage according to claim 1 , wherein the undercarriage possesses said two landing skids united by the front transverse element, thus forming “mustache” configuration.

13. The undercarriage according to claim 1 , wherein the undercarriage is arranged so that energy absorption during a normal landing, a hard landing, or a crash landing is absorbed solely by the transverse elements, the friction skids, and the buckling struts by deformation that is elastic or plastic, and without involving adjoining shock absorbers and side braces.

14. The undercarriage according to claim 1 , wherein the undercarriage is of a subcritical type.

15. The undercarriage according to claim 1 , wherein the undercarriage is of a subcritical type.

16. The undercarriage according to claim 1 , wherein the assembly means includes a rear fastener member and a front fastener member members disposed transversely to at least one of the longitudinal midplane of the aircraft and longitudinally on either side of a center of gravity of said aircraft.

17. An undercarriage for a rotary wing aircraft having a carriage with a force take-up structure, the undercarriage comprising:

two landing skids extending in a longitudinal direction below the carriage and spaced apart laterally from a longitudinal midplane of the carriage, each skid adapted to absorb a portion of energy that is applied thereto during a normal landing by deforming elastically;

a pair of transverse elements connecting the two landing skids and adapted to absorb energy that is applied thereto during a normal landing by deforming elastically, the pair of transverse elements including a front transverse element and a rear transverse element spaced apart from each other in the longitudinal direction;

a connection system connecting the transverse elements to the force take-up structure of the aircraft and absorbing the energy that is applied thereto during a crash by deforming plastically in a controlled manner, the connection system including at least one pair of buckling struts, each strut of the at least one pair of buckling struts coupled to each of the transverse members with a bottom connection wherein the connection system includes at least one front pair of buckling struts and at least one rear pair of buckling struts; and

a fastening assembly providing statically-redundant coupling between the force take-up structure of the aircraft and the transverse elements, the fastening assembly located between the at least one pair of buckling struts,

wherein each of the transverse elements includes an endpiece section that extends transversely on either side of the undercarriage an offset distance outwards transversely and downwards from the bottom connection of the pair of buckling struts.

18. An undercarriage for a rotary wing aircraft having a carriage with a force take-up structure, the undercarriage comprising:

two landing skids extending in a longitudinal direction below the carriage and spaced apart laterally from a longitudinal midplane of the carriage, each skid being adapted to absorb a portion of energy that is applied thereto during a normal landing by deforming elastically;

a pair of transverse elements connecting the two landing skids and adapted to absorb energy that is applied thereto during a normal landing by deforming elastically, the pair of transverse elements including a front transverse element and a rear transverse element spaced apart from each other in the longitudinal direction;

a connection system connecting the transverse elements to the force take-up structure of the aircraft and absorbing the energy that is applied thereto during a crash by deforming plastically in a controlled manner, the connection system including at least one pair of buckling struts, each strut of the at least one pair of buckling struts being coupled to each of the transverse members with a bottom connection; and

a fastening assembly providing statically-redundant coupling between the force take-up structure of the aircraft and the transverse elements, the fastening assembly being located between the at least one pair of buckling struts,

wherein each of the transverse elements includes an endpiece section that extends transversely on either side of the undercarriage an offset distance outwards transversely and downwards from the bottom connection.

19. The undercarriage according to claim 18 , wherein the at least one pair of buckling struts includes a pair of rear buckling struts and a pair of front buckling struts, each of the buckling struts being provided with a bottom hinge and a top hinge.

20. The undercarriage according to claim 18 , wherein the fastening assembly includes a rear fastener member connected to the rear transverse member and a front fastener member connected to the front transverse member, the rear transverse member and the front transverse member being located transversely to at least one of the longitudinal midplane of the aircraft and longitudinally on either side of a center of gravity of said aircraft.