Abstract: An aerofoil has a main portion of aerofoil cross section, an inner spanwise root end where the aerofoil is in use secured to a supporting structure, and at an outermost spanwise end outboard of the main portion, beyond a tip station, a tip region which includes a tip edge. The planform configuration of the tip edge lies on a first Bezier curve constructed from at least four control points, P1, P2, P3 and P4, each lying on the periphery of a polygon which bounds the tip region. Control point P1 is located on a leading edge of the aerofoil. Control point P2 is located on the second side of the polygon. Control point P3 is located on the third side of the polygon, and control point P4 is located at the outermost tip edge point at a trailing edge of the aerofoil.

Abstract: An aerofoil has a main portion of aerofoil cross section, an inner spanwise root end where the aerofoil is in use secured to a supporting structure, and at an outermost spanwise end outboard of the main portion, beyond a tip station, a tip region which includes a tip edge. The planform configuration of the tip edge lies on a first Bezier curve constructed from at least four control points, P1, P2, P3 and P4, each lying on the periphery of a polygon which bounds the tip region. Control point P1 is located on a leading edge of the aerofoil. Control point P2 is located on the second side of the polygon. Control point P3 is located on the third side of the polygon, and control point P4 is located at the outermost tip edge point at a trailing edge of the aerofoil.

Abstract: A blade for an antitorque tail rotor of a helicopter, having a leading edge and a trailing edge opposite each other and elongated along a longitudinal axis of the blade; the trailing edge, in use, interacts with the air current after the leading edge; the blade also has an end portion extending between a reference section and a radially outer end of the blade with respect to a rotation axis of the blade; the rotation axis is outside the blade and crosswise with respect to the longitudinal axis; the length of the chord at the end portion decreases from the reference section to the radially outer end; and the leading and trailing edges are joined at the radially outer end.

Abstract: A blade for an antitorque tail rotor of a helicopter, having a leading edge and a trailing edge opposite each other and elongated along a longitudinal axis of the blade; the trailing edge, in use, interacts with the air current after the leading edge; the blade also has two opposite surfaces extending between the leading edge and the trailing edge, and a root portion extending from a radially inner first end, with respect to a rotation axis of the blade, towards a second end opposite the first end; and the root portion, when sectioned in a plane perpendicular to the leading edge and trailing edge, has a profile asymmetrical with respect to a chord joining the leading edge and trailing edge.

Abstract: A blade for an antitorque tail rotor of a helicopter, having a leading edge and a trailing edge opposite each other and elongated along a longitudinal axis of the blade; the trailing edge, in use, interacts with the air current after the leading edge; the blade also has an end portion extending between a reference section and a radially outer end of the blade with respect to a rotation axis of the blade; the rotation axis is outside the blade and crosswise with respect to the longitudinal axis; the length of the chord at the end portion decreases from the reference section to the radially outer end; and the leading and trailing edges are joined at the radially outer end.

Abstract: A blade for an antitorque tail rotor of a helicopter, having a leading edge and a trailing edge opposite each other and elongated along a longitudinal axis of the blade; the trailing edge, in use, interacts with the air current after the leading edge; the blade also has two opposite surfaces extending between the leading edge and the trailing edge, and a root portion extending from a radially inner first end, with respect to a rotation axis of the blade, towards a second end opposite the first end; and the root portion, when sectioned in a plane perpendicular to the leading edge and trailing edge, has a profile asymmetrical with respect to a chord joining the leading edge and trailing edge.

Abstract: An aerofoil comprises a leading edge and a trailing edge which define a mean chord length, and the aerofoil having an inner or root end adapted for attachment to an aircraft, and an outer end which includes a tip which is adapted in use to divide the airflow into two generally equal vortices one being an inner vortex and the other being an outer vortex the inner vortex being arranged to trail from an outer edge of a forward region of the tip and pass over a rear region of the tip.

Abstract: A propeller (10a) comprising a plurality of propeller blades (9a) each having a root end (11a) attached to the central propeller disc or hub (12a), an intermediate portion (13a) extending from the root end (11a) and having a generally aerofoil cross section extending chordwise between a leading edge (14a) and a trailing edge (15a), and the blade (9a) having a tip (19) at an end of the intermediate portion (13a) remote from the root end (11a), the tip (19) having a leading edge portion (20) extending forwardly from a junction (21) with the leading edge (14a) of the intermediate portion (13a) thus to provide a discontinuity or notch (25) in the leading edge (14a) of the blade (9a) at the junction (21).

Abstract: A method and apparatus for determining the airspeed of a rotary wing aircraft having a sustaining rotor with a plurality of radially extending rotor blades for rotation about a substantially vertical axis comprises the steps of measuring an airflow sideslip angle established during rotation of each rotor blade by the vector of a radial flow component due to the relative wind vector and the rotational velocity perpendicular to a blade feathering axis, producing a signal representative of the sideslip angle, comparing the signal in a processor containing information on a known relationship between the sideslip angle and airspeed, providing an output signal representative of the airspeed and wind direction to a display which may display both the airspeed and wind direction.

Abstract: A rotary blade includes a fixed boundary layer control device extending spanwise on a lower surface adjacent the trailing edge to improve the lift/thrust characteristics of the blade especially at positive incidence angles. It was discovered that expected detrimental effects at zero/negative incidence did not materialize and the reasons are identified. Such blades are particularly useful for helicopter sustaining and anti-torque rotors.

Abstract: Flow separation behind the notch region of a swept tip of a helicopter rotor blade is reduced by a plurality of boundary layer control vanes located adjacent a forwardly swept leading edge portion forming the notch region.

Abstract: A helicoper rotor blade includes at its outer end a tip vane having a mean chord length greater than fifty percent of a chord length of a blade central portion and a span length greater than fifty percent of the blade chord which in operation generates two approximately equal strength tip vortices to reduce an acoustic impulse and a resulting noise known as blade slap.

Abstract: Flow separation behind the notch region of a swept tip of a helicopter rotor blade is reduced by features of the geometry and aerodynamic characteristics of the notch region itself. In particular it has been found beneficial for a forwardly swept leading edge portion to extend at an angle between 30 degrees and 55 degrees from a reference line parallel to a blade pitch change axis and the leading edge of the aerofoil in the notch region incorporates blade droop.