A rotor blade of a rotary wing aircraft includes a core defining a trailing edge of the rotor blade and a skin extending from the trailing edge defining an opening including the core. The skin defines an aerodynamic surface of the rotor blade. The rotor blade additionally includes at least one trim tab assembly including a trim portion extending from the core beyond the trailing edge of the rotor blade and an actuation system including at least one actuator disposed within the core. The actuation system is operable to adjust an angle of the trim portion relative to the rotor blade.

A double-blade tandem helicopter comprising a fuselage (10), a power system, a control system, and two rotor assemblies (30, 50). The rotor assemblies are longitudinally disposed relative to the fuselage. Each rotor assembly comprises a rotor shaft (31, 51), a rotor head (33, 53), and two blades (35, 37, 55, 57). The rotor shaft is connected to the power system, the rotor head is fixed to the rotor shaft, and the blades are attached to the rotor head. The double-blade tandem helicopter has a larger rotor disk area than that of a single-rotor helicopter while has a fuselage weight approaching that of the single-rotor helicopter, and thus has a take off weight approximately twice or more times of the single-rotor helicopter, and meanwhile has characteristics such as small volume, simple structure and high aerodynamic efficiency.

A double-blade tandem helicopter comprising a fuselage (10), a power system, a control system, and two rotor assemblies (30, 50). The rotor assemblies are longitudinally disposed relative to the fuselage. Each rotor assembly comprises a rotor shaft (31, 51), a rotor head (33, 53), and two blades (35, 37, 55, 57). The rotor shaft is connected to the power system, the rotor head is fixed to the rotor shaft, and the blades are attached to the rotor head. The double-blade tandem helicopter has a larger rotor disk area than that of a single-rotor helicopter while has a fuselage weight approaching that of the single-rotor helicopter, and thus has a take off weight approximately twice or more times of the single-rotor helicopter, and meanwhile has characteristics such as small volume, simple structure and high aerodynamic efficiency.

A blade for an open rotor includes a pressure side and a suction side, the pressure side and the suction side intersecting at a leading edge and a trailing edge, wherein for at least 30% of a span of the blade, the meanline of the airfoil section is shaped such that a relative curvature parameter is greater than 1.2 in a first region, less than 0.75 in a second region, and greater than 0.9 in a third region, wherein the relative curvature parameter of a region is defined by Δζ.sub.n/Δζ.sub.tot/Δ(x/c).sub.n wherein ζ corresponds to the inverse tangent of the slope of a meanline curve, subscript n indicates the region, and x/c is a chordwise location normalized by the chord and wherein the first region comprises at least x/c=0.0 to 0.15 and the third region comprises at least x/c=0.80 to 1.0.

A blade for an open rotor includes a pressure side and a suction side, the pressure side and the suction side intersecting at a leading edge and a trailing edge, wherein for at least 30% of a span of the blade, the meanline of the airfoil section is shaped such that a relative curvature parameter is greater than 1.2 in a first region, less than 0.75 in a second region, and greater than 0.9 in a third region, wherein the relative curvature parameter of a region is defined by Δζ.sub.n/Δζ.sub.tot/Δ(x/c).sub.n wherein ζ corresponds to the inverse tangent of the slope of a meanline curve, subscript n indicates the region, and x/c is a chordwise location normalized by the chord and wherein the first region comprises at least x/c=0.0 to 0.15 and the third region comprises at least x/c=0.80 to 1.0.

A yaw control system for a helicopter having an airframe that includes a tailboom includes one or more tail rotors rotatably coupled to the tailboom and a flight control computer implementing an airframe protection module. The airframe protection module includes an airframe protection monitoring module configured to monitor one or more flight parameters of the helicopter and an airframe protection command module configured to modify one or more operating parameters of the one or more tail rotors based on the one or more flight parameters of the helicopter, thereby protecting the airframe of the helicopter.

A method for using a rotorcraft main blades or airframe propeller whereby by using a convergent-divergent nozzle with a choked nozzle. The said main nozzle being a component of the said main blades having a rotation system. The said nozzle airflow transmits power giving movement by the said blades through the said propeller rotational movement with maximum thrust and efficiency. The said convergent-divergent nozzle achieves maximum thrust efficiency increasing kinetic energy output.

A method for using a rotorcraft main blades or airframe propeller whereby by using a convergent-divergent nozzle with a choked nozzle. The said main nozzle being a component of the said main blades having a rotation system. The said nozzle airflow transmits power giving movement by the said blades through the said propeller rotational movement with maximum thrust and efficiency. The said convergent-divergent nozzle achieves maximum thrust efficiency increasing kinetic energy output.

A rotor blade assembly includes a rotor blade having inboard and outboard regions, a blade body, and an internal spar, the blade body defining leading and trailing edges. A trailing edge assembly extends from and is connected to the trailing edge, and has a trailing edge flap and an actuator configured to deploy the trailing edge flap between first and second positions. In one of the first and second positions, an upper surface of the trailing edge flap conforms in profile to an upper surface of the rotor blade, and in the other, the trailing edge flap is inclined relative to the blade. During hovering flight, at least one trailing edge flap segment is deflected to enhance hover performance. During forward flight, at least one trailing edge flap segment is either not deflected for reduced effect on forward flight or is deflected for additional thrust.

A rotor blade assembly includes a rotor blade having inboard and outboard regions, a blade body, and an internal spar, the blade body defining leading and trailing edges. A trailing edge assembly extends from and is connected to the trailing edge, and has a trailing edge flap and an actuator configured to deploy the trailing edge flap between first and second positions. In one of the first and second positions, an upper surface of the trailing edge flap conforms in profile to an upper surface of the rotor blade, and in the other, the trailing edge flap is inclined relative to the blade. During hovering flight, at least one trailing edge flap segment is deflected to enhance hover performance. During forward flight, at least one trailing edge flap segment is either not deflected for reduced effect on forward flight or is deflected for additional thrust.