A rotary wing aircraft includes an airframe, one or more engines supported by the airframe, and a plurality of rotor blades operatively connected to the one or more engines. Each of the plurality of rotor blades includes a rotor lift-to-drag (L/De) ratio greater than 9 at airspeeds between about 150 KTAS and about 210 KTAS, and the rotary wing aircraft includes an aircraft lift-to drag (L/D) ratio of greater than about 4 between about 99 KTAS and about 210 KTAS.

A flight control system for a rotorcraft includes a controller configured to receive input indicative of ambient conditions, determine a threshold rotor blade tip speed based on the input, and to output rotor control commands to prevent rotor blade tips from exceeding the threshold speed. An aircraft includes an airframe, a main rotor assembly operatively connected to the airframe, and a flight control system as described above. The flight control system is operatively connected to control the main rotor assembly. It is contemplated that the main rotor assembly can be a counter rotating coaxial main rotor assembly including an upper rotor assembly with a plurality of blades and a lower rotor assembly having a plurality of blades, wherein the flight control system is operatively connected to control both upper and lower rotor assemblies to prevent any blade tips of the upper and lower rotor assemblies from exceeding the threshold speed.

An aircraft includes an airframe having an extending tail and a counter rotating, coaxial main rotor assembly disposed at the airframe including an upper rotor assembly and a lower rotor assembly. A translational thrust system is positioned at the extending tail and provides translational thrust to the airframe. An airframe parasitic drag of the airframe is greater than a main rotor assembly drag of the main rotor assembly. An aircraft includes an airframe having an extending tail and a counter rotating, coaxial main rotor assembly disposed at the airframe including an upper rotor assembly and a lower rotor assembly. A translational thrust system is positioned at the extending tail and provides translational thrust to the airframe. A main rotor assembly drag is at or between about 25% and 40% of a total aircraft drag.

An aircraft is provided including an airframe, an extending tail, and a counter rotating, coaxial main rotor assembly including an upper rotor assembly and a lower rotor assembly. A translational thrust system positioned at the extending tail, the translational thrust system providing translational thrust to the airframe. A horizontal stabilizer with a left elevator and right elevator positioned at the extending tail. A flight control computer to independently control one or more of the main rotor assembly and the elevator through a fly-by-wire control system. The flight control computer is configured to mix a collective pitch of the main rotor assembly and a deflection of the elevator.

An aircraft is provided including an airframe, an extending tail, one or more engines supported by the airframe, and a counter rotating, coaxial main rotor assembly including an upper rotor assembly and a lower rotor assembly. A translational thrust system positioned at the extending tail. The translational thrust system providing translational thrust to the airframe. A gearbox configured to transfer power from the engine to the main rotor assembly. A flight control computer to independently control one or more of the engine, the upper rotor assembly, the lower rotor assembly, and the translational thrust system. The flight control computer, in response to at least one control command, engages or disengages the translational thrust system, while maintaining controlled powered flight.

An aircraft includes an airframe having an extending tail, a counter rotating, coaxial main rotor assembly disposed at the airframe including an upper rotor assembly and a lower rotor assembly and a translational thrust system positioned at the extending tail and providing translational thrust to the airframe. A flight control computer is configured to control a main rotor rotational speed of the upper and the lower rotor assemblies of the main rotor assembly as a function of airspeed of the aircraft. A method of operating an aircraft includes retrieving a threshold main rotor rotational speed of the dual coaxial main rotor assembly and calculating an actual main rotor rotational speed according to an environment of the aircraft. The actual main rotor rotational speed is maintained to remain at or below the threshold main rotor speed according to an airspeed of the aircraft.

A differential pre-cone rotary wing arrangement includes a first rotor assembly having a first set of rotor blades rotatable about an axis, the first set of rotor blades having a first pre-cone angle, and a second rotor assembly having a second set of rotor blades rotatable about the axis, the second set of rotor blades having a second pre-cone angle, the second pre-cone angle is different than the first pre-cone angle.

An aircraft is provided including an airframe, an extending tail, and a counter rotating, coaxial main rotor assembly including an upper rotor assembly and a lower rotor assembly. A translational thrust system positioned at the extending tail, the translational thrust system providing translational thrust to the airframe. A cockpit in the airframe, the cockpit including two seats and a single collective control input positioned between the two seats.

An aircraft composed of an airframe, an extending tail, a counter rotating, coaxial main rotor assembly including an upper rotor assembly and a lower rotor assembly, and a translational thrust system positioned at the extending tail. The translational thrust system provides translational thrust to the airframe. The aircraft also includes a rotor hover figure of merit greater than about 0.79 for a C.sub.T/ between about 0.085 and about 0.125.

An aircraft is provided including an airframe, an extending tail, a counter-rotating, coaxial main rotor assembly having an upper rotor assembly and a lower rotor assembly, and a translational thrust system including a propeller positioned at the extending tail. The translational thrust system is configured to provide translational thrust to the airframe when the aircraft is in a non-autorotation state and to generate power when in an autorotation state. A gearbox interconnects the propeller and the main rotor assembly to drive the main rotor assembly and the translational thrust system in the non-autorotation state. When the aircraft is in autorotation, the power generated by the propeller drives rotation of the main rotor assembly via the gearbox.