Rotary blades
AssigneeWestland Helicopters Limited
InventorsFrederick J. Perry, Alan Brocklehurst
Life of this patent
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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.
Claims15
A helicopter rotary blade having a root end for attachment to a rotor hub and a tip end defining a blade span and in cross section being of aerofoil profile having a leading edge and a trailing edge defining a blade chord and joined by an upper surface and a lower surface, the blade in use being adapted for movement through a range of incidence angles with respect to an airflow, wherein the rotary blade includes a fixed boundary layer flow deflection device extending spanwise at or adjacent the lower surface trailing edge and adapted, when the blade is operating at high positive incidence angles to protrude through a boundary layer flow on the lower surface so as to deflect the boundary layer on the lower surface away from the trailing edge thereby improving the lift characteristics of the rotary blade and when the blade is operating at low or negative incidence angles to be immersed in a thicker boundary layer flow on the lower surface so as to have substantially no effect on the boundary layer flow.
Dependencies are inferred from the claim text.