Systems and methods include providing an aircraft with a vertical stabilizer system having a vertical stabilizer operatively coupled to a tail boom, tail rotor gearbox, or other component of the aircraft at a forward attachment and an aft attachment. The vertical stabilizer is selectively rotatable to adjust an angle of attack of the vertical stabilizer with respect to a forward flight direction of the aircraft. The vertical stabilizer is rotatable between a forward flight position having a substantially small degree angle of attack and a hover or lateral movement position having a substantially ninety degree angle of attack.

An aircraft is provided including an airframe, an extending tail, and a counter rotating, coaxial main rotor assembly including an upper rotor assembly with an upper blade and a lower rotor assembly with a lower blade. A first antenna in one of upper blade and the lower blade, and a second antenna in the other of the upper blade and the lower blade. An oscillator to apply an excitation signal to the first antenna. A blade proximity monitor to monitor a magnitude of the excitation signal and an output signal from the second antenna to determine a distance between the upper blade and the lower blade.

A strake may extend along a portion of an approaching side of a tail boom of a helicopter. A number of vortex generators (VGs) may extend along a portion of a retreating side of the tail boom. For tail booms with circular cross sections, the strake and the VGs are positioned between approximately 5 and 15 degrees below a horizontal plane of the tail boom when viewed end on, on respective sides of the tail boom. For tail booms with non-circular cross sections, the strake and the VGs is positioned between approximately 5 and 15 degrees above a location where a change in curvature is greatest (e.g., where flow separation would otherwise occur) on a bottom half of the tail boom when viewed end on, on respective sides of the tail boom. A fairing may be located on the retreating side on the upper half of the tail boom, to create an asymmetric profile.

A strake may extend along a portion of an approaching side of a tail boom of a helicopter. A number of vortex generators (VGs) may extend along a portion of a retreating side of the tail boom. For tail booms with circular cross sections, the strake and the VGs are positioned between approximately 5 and 15 degrees below a horizontal plane of the tail boom when viewed end on, on respective sides of the tail boom. For tail booms with non-circular cross sections, the strake and the VGs is positioned between approximately 5 and 15 degrees above a location where a change in curvature is greatest (e.g., where flow separation would otherwise occur) on a bottom half of the tail boom when viewed end on, on respective sides of the tail boom. A fairing may be located on the retreating side on the upper half of the tail boom, to create an asymmetric profile.

A vertical tail of a helicopter has a leading edge and a trailing edge concave toward the leading edge. The helicopter includes a main rotor and a tail rotor for generating anti-torque to cancel torque generated by rotation of the main rotor. The trailing edge is concave within a range within which the vertical tail overlaps a circular region, formed as a rotation range of the tail rotor, in a rotation axis direction of the tail rotor.

An aircraft includes an airframe having an empennage, a counter rotating, coaxial main rotor assembly located at the airframe including an upper rotor assembly and a lower rotor assembly, and a translational thrust system positioned at the empennage and providing translational thrust to the airframe. At least two control surfaces located at the empennage are independently operable via commands from one or more flight control computers. A method of operating an aircraft includes transmitting a first signal from one or more flight control computers to a first control surface located at a first lateral side of a translational thrust system, and actuating the first control surface to a first position via the first signal. A second signal is transmitted to a second control surface located at a second lateral side opposite the first lateral side, and the second control surface is actuated to a second position via the second signal.

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.

An aircraft assembly is provided and includes a first member extending from an aircraft airframe, a propeller, which is drivable to rotate and a secondary member on which the propeller is supportable and which is aerodynamically pivotable with respect to the first member.

A compound rotorcraft with a fuselage and at least one main rotor, the fuselage comprising a lower side and an upper side that is opposed to the lower side, the at least one main rotor being arranged at the upper side, wherein at least one propeller is provided and mounted to a fixed wing arrangement that is laterally attached to the fuselage, the fixed wing arrangement comprising at least one upper wing that is arranged at an upper wing root joint area provided at the upper side of the fuselage and at least one lower wing that is arranged at a lower wing root joint area provided at the lower side of the fuselage, the upper and lower wings being at least interconnected at an associated interconnection region.

In one embodiment, a vertical stabilizer comprises an airfoil structure configured to be mounted to an aircraft at a vertical orientation. The airfoil structure comprises a leading edge and a trailing edge, wherein the trailing edge is configured to form a blunt shaped edge. The airfoil structure further comprises a root end and a tip end, wherein the airfoil structure is tapered from the root end to the tip end. The airfoil structure is also cambered. Finally, the airfoil structure is further configured to be mounted with a rotor, and is also further configured to house one or more internal components associated with the aircraft.