A helicopter comprising: - a rotor, said rotor in turn comprising a drive shaft; - a fuselage; - a drive transmission unit operatively connected to said drive shaft; - a support body, which supports said transmission unit, and which further supports said drive shaft in a rotary manner about a first axis; and - constraining means interposed between said support body and said fuselage; said constraining means in turn comprising a crosspiece connected in a fixed manner with respect to said support body and having a first lying plane; said crosspiece being formed in part by a metallic material and in part by a visco-elastic material; said crosspiece being delimited by lateral sides extending transversely to said first plane; said crosspiece comprising, in turn,: - a flange connected to said support body and having an opening having a second axis orthogonal to said plane and through which said axis can pass; and - a pair of end appendages (23, 24), which are arranged on respective opposite sides to each other of said second axis and are connected, in a fixed and rigid manner, to said fuselage; said appendages (23, 24) projecting sideways from respective portions of said flange located on opposite sides with respect to said second axis; characterized in that said flange and appendages (23, 24) are made of a multi-layer material, which comprises at least one first layer of a metallic material and at least one second layer of a visco-elastic material; said first layer and second layer being superimposed on each other; said first layer and second layer extending over the entire width of said crosspiece on respective second planes parallel to said first plane, so as to partly define said sides. - a rotor, said rotor in turn comprising a drive shaft; - a fuselage; - a drive transmission unit operatively connected to said drive shaft; - a support body, which supports said transmission unit, and which further supports said drive shaft in a rotary manner about a first axis; and - constraining means interposed between said support body and said fuselage; said constraining means in turn comprising a crosspiece connected in a fixed manner with respect to said support body and having a first lying plane; said crosspiece being formed in part by a metallic material and in part by a visco-elastic material; said crosspiece being delimited by lateral sides extending transversely to said first plane; said crosspiece comprising, in turn,: - a flange connected to said support body and having an opening having a second axis orthogonal to said plane and through which said axis can pass; and - a pair of end appendages (23, 24), which are arranged on respective opposite sides to each other of said second axis and are connected, in a fixed and rigid manner, to said fuselage; said appendages (23, 24) projecting sideways from respective portions of said flange located on opposite sides with respect to said second axis; characterized in that said flange and appendages (23, 24) are made of a multi-layer material, which comprises at least one first layer of a metallic material and at least one second layer of a visco-elastic material; said first layer and second layer being superimposed on each other; said first layer and second layer extending over the entire width of said crosspiece on respective second planes parallel to said first plane, so as to partly define said sides. - a flange connected to said support body and having an opening having a second axis orthogonal to said plane and through which said axis can pass; and - a pair of end appendages (23, 24), which are arranged on respective opposite sides to each other of said second axis and are connected, in a fixed and rigid manner, to said fuselage; said appendages (23, 24) projecting sideways from respective portions of said flange located on opposite sides with respect to said second axis; characterized in that said flange and appendages (23, 24) are made of a multi-layer material, which comprises at least one first layer of a metallic material and at least one second layer of a visco-elastic material; said first layer and second layer being superimposed on each other; said first layer and second layer extending over the entire width of said crosspiece on respective second planes parallel to said first plane, so as to partly define said sides.