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 helicopter rotor blade includes a rearwardly swept tip portion having a leading edge of aerofoil profile located forward of the leading edge of a central portion of the blade, and blended with a sharp tip edge of higher sweep magnitude than the leading edge and extending rearwardly to an extreme tip of the blade. A rearwardly swept trailing edge extends from a junction with the trailing edge of the central portion to the extreme tip so that the tip portion has a chord dimension greater than that of the central portion of the blade.In operation, the rotor blade utilizes a stable vortex dominated flow field created over the tip portion to provide operational advantages in respect of both a retreating and an advancing blade.