Abstract: A thrust producing unit for producing thrust in a predetermined direction, comprising at least two rotor assemblies and a shrouding, each one of the at least two rotor assemblies, defining an associated rotor plane, wherein a first rotor assembly of the at least two rotor assemblies is provided for operating in a failure-free operating mode of the thrust producing unit and a second rotor assembly of the at least two rotor assemblies is provided for operating at least in case of a failure of the first rotor assembly, and wherein the shrouding accommodates at most one of the at least two rotor assemblies.

Abstract: A noise reduced and performance improved rotor blade (1) for a helicopter. The blade has three aerodynamic sections (5, 6, 7) along the blade span between a leading edge (8) and a trailing edge (9). An inner rectangular or tapered section (5) next to a blade root for said blade's connection to a rotor hub rotating about a rotor axis of said helicopter. A middle section (6) is adjacent to the inner section (5) and opposed to the blade root. The middle section (6) is forward swept over a distance along the span of the blade (1). An outer section (7) lies between the middle section (6) and the blade tip (11). The outer section (7) is back swept along a further part of the span of the blade (1). The outer section (7) includes a parabolic shape towards the free end of the blade tip (11).

Abstract: A noise reduced and performance improved rotor blade (1) for a helicopter. The blade has three aerodynamic sections (5, 6, 7) along the blade span between a leading edge (8) and a trailing edge (9). An inner rectangular or tapered section (5) next to a blade root for said blade's connection to a rotor hub rotating about a rotor axis of said helicopter. A middle section (6) is adjacent to the inner section (5) and opposed to the blade root. The middle section (6) is forward swept over a distance along the span of the blade (1). An outer section (7) lies between the middle section (6) and the blade tip (11). The outer section (7) is back swept along a further part of the span of the blade (1). The outer section (7) includes a parabolic shape towards the free end of the blade tip (11).