A propeller includes a blade free to rotate. A first stop is positioned to mechanically engage one or both of a first portion of the blade and a first structure coupled to the blade when the blade is in a first position at a first end of the rotational range of motion. A second stop is positioned to mechanically engage one or both of a second portion of the blade and a second structure coupled to the blade when the blade is in a second position at a second end of the defined rotational range. The blade rotates to the first position against the first stop when the propeller is rotated in a first direction and to the second position against the second stop when the propeller is rotated in a second direction.

A propeller includes a blade free to rotate. A first stop is positioned to mechanically engage one or both of a first portion of the blade and a first structure coupled to the blade when the blade is in a first position at a first end of the rotational range of motion. A second stop is positioned to mechanically engage one or both of a second portion of the blade and a second structure coupled to the blade when the blade is in a second position at a second end of the defined rotational range. The blade rotates to the first position against the first stop when the propeller is rotated in a first direction and to the second position against the second stop when the propeller is rotated in a second direction.

A profiled structure for an aircraft or turbomachine is elongated in a direction in which the structure has a length exposed to an airflow and includes serrations defined by successive teeth and depressions. The serrations may be transverse to a leading edge and/or a trailing edge of the profiled structure and in the direction of elongation. Along the profiled leading edge and/or profiled trailing edge, the successive teeth and depressions may extend only over a part of the length exposed to the flow. The amplitude and/or spacing of the teeth may vary monotonically except for the few teeth nearest each end of the part, with a remaining part of the length being smooth.

Rotor assemblies for aircraft are described that include a plurality of blades that are disposed vertically on a common axis along different horizontal planes. When the rotor assemblies are free-wheeling, the blades form a vertically stacked configuration, and when the rotor assembly is driven in rotation to generate lift, the blades bloom out from the vertically stacked configuration. At least one of the blades in the rotor assembly has a blade geometry that is different with respect to other blades such that when the blades are vertically stacked and free-wheeling, the collective shape of the blades is aerodynamic in shape, based on the different blade geometry, that reduces aerodynamic drag on the rotor assembly.

The blades of the propeller are characterized by a blade center axis which corresponds to a generator line of a cone to which the blade, or blade thrust surface, conforms. The propeller hub is fixed to the blade at the root, in line with the blade center axis, such that the hub axis and blade center axis lie in the same plane, and the leading edge of the blade is positioned forward (referring to the upstream direction of movement caused by the propeller) of the trailing edge of the blade.

The blades of the propeller are characterized by a blade center axis which corresponds to a generator line of a cone to which the blade, or blade thrust surface, conforms. The propeller hub is fixed to the blade at the root, in line with the blade center axis, such that the hub axis and blade center axis lie in the same plane, and the leading edge of the blade is positioned forward (referring to the upstream direction of movement caused by the propeller) of the trailing edge of the blade.

The invention relates to an aircraft turboprop engine having two unducted propellers, coaxial about a rotation axis (LL), respectively upstream (12) and downstream (14′), each propeller comprising an annular row of blades, the blades of the downstream propeller (14′) each having a truncated head and each comprising a leading edge (20′) and a trailing edge (22′), the radially external ends (A2, B1) of which are distant from each other and are connected by a terminal edge (21′), characterised in that the terminal edge (21′) of each blade of the downstream propeller (14′) has, at at least two points, tangents in a meridian plane having different slopes, the upstream end (A) of the terminal edge defining a maximum radial dimension (R2) of the blade and its downstream end (B1) defining a minimum radial dimension (R3) of the terminal edge.

The invention relates to an aircraft turboprop engine having two unducted propellers, coaxial about a rotation axis (LL), respectively upstream (12) and downstream (14′), each propeller comprising an annular row of blades, the blades of the downstream propeller (14′) each having a truncated head and each comprising a leading edge (20′) and a trailing edge (22′), the radially external ends (A2, B1) of which are distant from each other and are connected by a terminal edge (21′), characterised in that the terminal edge (21′) of each blade of the downstream propeller (14′) has, at at least two points, tangents in a meridian plane having different slopes, the upstream end (A) of the terminal edge defining a maximum radial dimension (R2) of the blade and its downstream end (B1) defining a minimum radial dimension (R3) of the terminal edge.

A structure adapted to traverse a fluid environment includes an elongate body having a root, a wingtip, a leading edge and a trailing edge; and a plurality of rigid projections each extending from a respective position along the leading edge and/or the trailing edge generally along the same plane as a front surface of the body.

A structure adapted to traverse a fluid environment includes an elongate body having a root, a wingtip, a leading edge and a trailing edge; and a plurality of rigid projections each extending from a respective position along the leading edge and/or the trailing edge generally along the same plane as a front surface of the body.