Abstract: A compound rotorcraft comprises a fuselage, a rotor coupled to the fuselage and a wing mounted to the fuselage. The rotorcraft further comprising a first outboard propeller, a first inboard propeller, a second outboard propeller, and a second inboard propeller. The first outboard propeller having a propeller body and propeller blades, the body mounted to a first wing-half at a first incidence angle. The first inboard propeller having a propeller body and propeller blades, the body mounted to the first wing-half between the first outboard propeller and the fuselage at a second incidence angle. The second outboard propeller having a propeller body and propeller blades, the body mounted to a second wing-half at a third incidence angle. The second inboard propeller comprising a propeller body and propeller blades, the body mounted to a second wing-half between the second outboard propeller in the fuselage at a fourth incidence angle.

Abstract: A system to prevent or limit resonance in a rotocraft. The system comprises an airframe, a rotor system having a natural frequency and including a rotor and a mast attached to the airframe, and a non-linear spring positioned between the rotor system and the airframe. The rotor system and the airframe are operable to move relative to each other as the rotor system begins to oscillate. The non-linear spring is configured to be deformed when the rotor system and the airframe move relative to each other such that the deformation of the non-linear spring causes the natural frequency of the rotor system to change. Also disclosed is a related method for preventing or limiting resonance in a rotorcraft.

Abstract: A compound rotorcraft comprises a fuselage, a rotor coupled to the fuselage and a wing mounted to the fuselage. The rotorcraft further comprising a first outboard propeller, a first inboard propeller, a second outboard propeller, and a second inboard propeller. The first outboard propeller having a propeller body and propeller blades, the body mounted to a first wing-half at a first incidence angle. The first inboard propeller having a propeller body and propeller blades, the body mounted to the first wing-half between the first outboard propeller and the fuselage at a second incidence angle. The second outboard propeller having a propeller body and propeller blades, the body mounted to a second wing-half at a third incidence angle. The second inboard propeller comprising a propeller body and propeller blades, the body mounted to a second wing-half between the second outboard propeller in the fuselage at a fourth incidence angle.

Abstract: A compound rotorcraft comprises a fuselage, a rotor coupled to the fuselage and a wing mounted to the fuselage. The rotorcraft further comprising a first outboard propeller, a first inboard propeller, a second outboard propeller, and a second inboard propeller. The first outboard propeller having a propeller body and propeller blades, the body mounted to a first wing-half at a first incidence angle. The first inboard propeller having a propeller body and propeller blades, the body mounted to the first wing-half between the first outboard propeller and the fuselage at a second incidence angle. The second outboard propeller having a propeller body and propeller blades, the body mounted to a second wing-half at a third incidence angle. The second inboard propeller comprising a propeller body and propeller blades, the body mounted to a second wing-half between the second outboard propeller in the fuselage at a fourth incidence angle.

Abstract: A compound rotorcraft comprises a fuselage, a rotor coupled to the fuselage and a wing mounted to the fuselage. The rotorcraft further comprising a first outboard propeller, a first inboard propeller, a second outboard propeller, and a second inboard propeller. The first outboard propeller having a propeller body and propeller blades, the body mounted to a first wing-half at a first incidence angle. The first inboard propeller having a propeller body and propeller blades, the body mounted to the first wing-half between the first outboard propeller and the fuselage at a second incidence angle. The second outboard propeller having a propeller body and propeller blades, the body mounted to a second wing-half at a third incidence angle. The second inboard propeller comprising a propeller body and propeller blades, the body mounted to a second wing-half between the second outboard propeller in the fuselage at a fourth incidence angle.

Abstract: An embodiment includes a system for controlling blade pitch in a rotorcraft having an engine; a drive shaft with a first end and a second end and connected at the first end to the engine; a rotor with two or more blades connected to the second end of the drive shaft; and one or more actuators positioned adjacent to the rotor blades operable to change a blade pitch of the rotor blades.

Abstract: Apparatus and methods for eliminating back drive in a push pull type control system, are provided. An exemplary apparatus includes a control rod including a pair of spaced apart piston displacement members each configured to carry a check valve. The apparatus also includes a pair of opposite-face check valves each configured to seal against respective opposing face of a piston head to form a hydraulic lock, preventing back drive in the control system.

Abstract: Apparatus and methods for eliminating back drive in a push pull type control system, are provided. An exemplary apparatus includes a control rod including a pair of spaced apart piston displacement members each configured to carry a check valve. The apparatus also includes a pair of opposite-face check valves each configured to seal against respective opposing face of a piston head to form a hydraulic lock, preventing back drive in the control system.

Abstract: A rotor aircraft has an engine having an output shaft. At least one propeller is driven by the engine to provide forward thrust to the aircraft. Wings provide lift while in forward flight. A rotor is driven by rotor drive mechanism, which selectively provides torque to the rotor drive shaft from the engine while in a first mode. The rotor drive mechanism selectively provides torque to the rotor drive shaft to rotate at a speed independent of a speed of the output shaft of the engine while in a second mode. In one embodiment, the rotor drive mechanism is a variable speed transmission powered by the engine. In another embodiment, the rotor drive mechanism is an electric motor.

Abstract: A rotor aircraft has an engine, a propeller, wings, and a rotor. An electric motor is coupled to the rotor drive shaft for applying torque to the rotor drive shaft. The electric motor is sized to supply all of the torque to pre-rotate the rotor to a selected speed prior to liftoff of the aircraft. The wings are capable of providing substantially all of the lift required during forward flight at a cruise speed. The rotor being is capable of being trimmed to provide substantially zero lift and auto-rotate at cruise speed. Sensors sense flight conditions of the aircraft and provide signals to a controller that selectively causes the electric motor to cease applying torque to the rotor drive shaft during autorotation at cruise speed. The controller also causes the electric motor to apply torque to the rotor drive shaft if the sensors indicate additional rotor speed is needed.

Abstract: Apparatus and methods for eliminating back drive in a push pull type control system, are provided. An exemplary apparatus includes a control rod including a pair of spaced apart piston displacement members each configured to carry a check valve. The apparatus also includes a pair of opposite-face check valves each configured to seal against respective opposing face of a piston head to form a hydraulic lock, preventing back drive in the control system.

Abstract: A rotary aircraft has a fuselage with wings and a rotor. The blades of the rotor are twistable about a pitch axis to vary collective pitch. A collective pitch shaft moves in an advancing direction to increase the collective pitch. Weights are mounted to the blades for outward movement along the blades in response to an increase in rotational speed of the blades. A linkage between each of the weights and the collective pitch shaft moves the collective pitch shaft in the advancing direction in response to an increase in rotational speed. A spring acting through a cam mechanism exerts a non linear force in opposition to the outward movement of the blades.

Abstract: A rotor aircraft has a tilting hub for cyclic control operated by either a tilting spindle or swash plate mounted to the upper end of the drive shaft. A spinner housing with two separate half portions encloses the hub. The blades of the rotor have root portions that are integrally joined to the separate half portions. During a collective pitch change, the half portions rotate relative to each other, but at advance ratios greater than about 0.7, when the collective can be held constant, the spinner half portions can be in perfect alignment. Concentric control sleeves surround the drive shaft for changing collective pitch as well as cyclic pitch.

Abstract: A rotor aircraft has a fuselage with a rotor mounted above by a rotor shaft. An arm is pivotally engaged with a lower portion of the rotor shaft and pivotally engaged with the fuselage, enabling the rotor to move with little restriction vertically and horizontal in all directions relative to the fuselage as the rotor rotates in order to isolate rotor oscillations. An infinitely variable air spring is used to counter vertical and fore and aft loads. Damping in the form of elastomeric materials, piston seal friction, and fluid flow through an orifice may be added as required.

Abstract: A method of operating a rotor aircraft involves measuring an airspeed of the aircraft and a rotational speed of the rotor. A controller determines a Mu of the rotor based on the airspeed of the aircraft and the rotational speed of the rotor. The controller varies the collective pitch of the rotor blades in relationship to the Mu, from an inertia powered jump takeoff, through high speed high advance ratio flight, through a low speed landing approach, to a zero or short roll flare landing. In addition as the rotor is unloaded and the rotor slows down, the controller maintains a minimum rotor RPM with the use of a tilting mast.

Abstract: A rotor for rotary wing aircraft includes a number of features that reduce the collective forces required to control the pitch of the rotor. The spar caps of the spar become joined to one another at the same point where bonding begins between the blade and the spar. The tendency of blade to want to flatten out is minimized since the centrifugal force acting on the spar is located at or near the pitch change axis. Tip weights are located at or near the pitch change axis as well. In a preferred embodiment, the tip weights are located evenly in front of and behind the structural center of the inboard section of the spar. The blade of the rotor and the tip are not swept back.

Abstract: A variable pitch aircraft propeller control uses a two-speed planetary gearbox between a turbine engine and an adjustable pitch propeller. For maximum efficiency, the rotation rate of the propeller is high at aircraft take-off to generate maximum static thrust. However, when at high altitude and at high speed, the propeller rotation rate is reduced to hold the vector sum of the aircraft forward speed and the propeller rotational tip speed at the speed that results in the highest efficiency for the propeller. The two-speed transmission supplies these two gear ratios. At takeoff and low altitude flight, a low gear ratio is used. At high altitude, a high gear ratio is used. The gear ratio maybe manually selected by the pilot, or automatically changed by the propeller controller to obtain the best combined efficiency for the engine and the propeller.

Abstract: A fixed wing rotorcraft uses differential thrust between wing mounted propellers to provide counter torque when the rotor is being powered by a power source. The rotorcraft is comprised of a fuselage to which fixed wings are attached. A rotor is attached on an upper side of the fuselage and provides lift at low speeds while the wings provide a majority of the lift at high speeds. When at high speeds the rotor may be slowed to reduce advancing tip speed and retreating blade stall. Forward thrust and counter torque is provided by propellers mounted on either side of the fuselage or even on the wings.

Abstract: An aircraft landing gear includes a sealed cylinder divided by a cylinder head to define an upper chamber and a lower chamber. The lower chamber is further divided by a piston having a piston rod passing in a sealed manner through the lower cylinder end. The cylinder head includes one or more orifices, the opening of each containing an electromagnetic coil configured to control the viscosity of the magneto-rheological oil passing therethrough. The electrical current through the electromagnetic coil is continually controlled by a microcomputer with attached sensors for piston position and pressure between the desired piston and the cylinder head, such that the pressure between the piston and the cylinder head decelerates the aircraft evenly throughout the desired piston stroke. The pressure also is limited to a desired maximum level so that, in a severe crash, the shock absorber will absorb significant energy before it fails structurally.

Abstract: An improved method of operating rotorcraft capable of achieving high speeds such that stability is maintained as the craft speed exceeds 0.75 times the rotor tip speed. These high speeds are achieved by varying collective pitch, including to negative values, to maintain acceptable levels of flapping at high aircraft forward speeds and low rotor rotation rates, or adjusting or maintaining the rotor rotation rate by automatically controlling the tilt of the rotor disk relative to the airstream or aircraft, or a combination of these techniques. More specifically, by utilizing these techniques the forward aircraft speeds can be high enough, and the rotor rotation rates low enough, that an advance ratio, Mu, greater than 0.75 can be achieved while maintaining rotor stability.