Direct lift for an aircraft is provided by means of two or more fans mounted for rotation about a common axis parallel to the axis of yaw and adapted to be driven in opposite or alternate directions. As shown in FIG. 1, part or whole of the exhaust gases of the gas turbine engines 2, 3 may be diverted by means of valves 21–24 into volutes 12 and 15 and used to drive the fans. Referring to FIG. 2, the gases from the volutes discharge through nozzles 113 on to turbine blades 13 mounted on the outside of a peripheral ring carried on the fan blades 6; the gases then pass through fixed guide vanes 19 to the turbine blades 18 mounted on the fan blades 7. By appropriately relating the angles of the blades 6 and 13 on the upper fan and turbine assembly to the angles of the blades 7 and 18 of the lower assembly, an aerodynamic meshing effect is obtained which causes the fans to contra‐rotate at the required rotational speeds without the aid of any mechanical gearing between them. Controllable louvres (not shown) may be provided in the upper and lower surfaces of the ring or fuse‐lage containing the fan assembly and hinged so that they can be closed to fair into the wing or fuselage contours when the fans are not in use.
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