Month in the Patent Office

A helicopter rotor wherein each blade 3 carries a tip propulsion‐jet unit 4 has each unit constructed to reduce the velocity and noise level of the propulsive jets. Each unit 4 consists of an outer casing formed into a double wall at its forward end to provide an annular duct 12 which communicates through an aperture 20 with a conduit which extends through each blade from a gas producing plant 22, consisting of a gas turbine engine or engines or a separate compressor driven by such engine(s). Arms 10 secured radially on the forward end of the fairing support a central faired body 9 which is connected at its rear end to the fairing by stator blades 18 mounted ahead of a bladed rotor 5 secured in body 9 by a bearing 11. Blades 6 of rotor 5 carry a shroud ring formed on its periphery with turbine blades 8. Further stator blades 14, 15 connect the casing 4 to a tail fairing cone 16 and stator blades 13 bridge the duct 12. In operation gas flow from the blade conduit passes into duct 12 to be directed over blades 8 to drive rotor 5 which draws air through the unit to mix with the gases from gas producing plant 22 with a consequent reduction in jet velocity and noise. Any one of the rows of fan rotor and stator blades may be angularly adjustable to control the rotor speed. Alternatively, the turbine rotor blades 8 may be of the impulse type and a variable area admission nozzle used.