Abstract: A high quality finished prototype fuselage structure of an aircraft is manufactured using a cured female tool and an automated composite layup machine, and then touched up by hand to meet a tolerance or other specification. The female tool is preferably made from a male mold, by depositing layers of composite material over the mold, curing the tool together at a first cure temperature, separating the tool from the mold, and then curing the tool at a second, higher temperature. The first cure temperature should be at or below an upper limit temperature no greater than 180° F. The second cure temperature is preferably in the range of 250° F. to 350° F. The step of hand touching up can comprise one or more of mechanically abrading and deforming a first portion of the fuselage structure to mate with a second portion of the fuselage structure.

Abstract: Rotor blades are pre-bent in at least one of a flap direction and a lag direction, wherein the pre-bent portion comprises at least 20-60% of the length of the blade. Preferred methods include analyzing the rotor dynamic behavior using computational methods, deciding on the operational case (rotor lift load, forward speed, etc.) in which the loads and vibration reductions are desired, and using the computed results to decide on an amount of pre-bending of the unloaded blade so that it comes closer to the feather axis under load. Another class of preferred methods models the bending of a first blade in flight loading conditions, and then designs a second blade having a pre-bend in approximately an equal in magnitude and opposite in direction to the bending. It is contemplated that such “pre-bent” blades can significantly reduce rotor loads and vibration levels of rotorcraft equipped with semi-rigid or rigid rotors.

Abstract: A rotorcraft having multiple rotors, and wings that provide lift in forward flight, has mechanical coupling between rotors that can be disengaged and optionally reengaged, during flight. The coupling can, which can prevent a failure of one rotor from interfering with rotation of the other rotor(s), can be accomplished using many different types of devices, including for example, dog clutches and friction clutches, and collapsible clutches. Disengagement can range from being completely under control of an operator, to partially under operator control, to completely automatic. Among many other benefits, designing, manufacturing, fitting, retrofitting or in some other manner providing an aircraft with a device that can disengage rotation of one of the rotors from that of another one of the rotors during flight can be used to improving survivability in an emergency situation.

Abstract: In rotorcraft having rotors on multiple masts, a controller causes opposing roll mast moments to be applied to the different rotors. In preferred embodiments, the opposing roll moment is the result of increasing the lift on the advancing blade and reducing the lift on the retreating blade on the second rotor. This can be accomplished in any suitable manner, such as by applying differential cyclic roll control to the two rotors by tilting the two Swashplates of the two rotors or by using Individual Blade Control (IBC).

Abstract: Blades for rotorcraft are designed and/or implemented with rotor blades having a swept portion that occupies at least 20-40% of a length of the blade. Forward and aft sweeps are contemplated, with up to 20° or more of sweep. The swept portion preferably has a thickness ration of at least 10-20% at R80, and can have a tapered planform with a relatively outboard section having a smaller chord than a relatively inboard section. Contemplated design methods include optimizing or otherwise designing the rotor blade planform and lift distribution along the blade for efficiency in various flight conditions without taking into account the detrimental effects of high Mach numbers, and then using sweep angle, airfoil thickness and transonic airfoil shaping to maintain the lift distribution, low drag and low noise level at real Mach numbers at the various blade stations at the various flight conditions.

Abstract: Rotorcraft wings disposed between tilt-rotor nacelles have particularly high aspect ratios for tilt-rotor rotorcraft, including for example at least 6, 7, 8, or higher. The increase in wing span and aspect ratio is possible because of the use of rigid and semi-rigid rotors, and/or higher modulus of elasticity materials allows increases the stiffness of the wings to the level required for avoiding whirl flutter. Tilt-rotor aircraft having high aspect ratio wings can advantageously further include a controller that provides reduced RPM in a forward flight relative to hover, and/or a controller that provides variable speed, (a so-called “Optimum Speed Tilt Rotor”) as set forth in U.S. Pat. No. 6,641,365 to Karem (November 2003).

Abstract: Tilt-rotor aircraft experience increased efficiency and fuel economy by including wing extensions outboard of the tilting nacelles. Stall and buffeting during conversion from rotor-born hover to wing-born forward flight are reduced to an acceptable level using wide chord flaps deflected upwards by at least 15-20°, preferably in combination with leading edge slats. The outboard wing or wing portion preferably has a span at least 25-40% of a span of the inboard section, and a total surface area at least 10-20% the total surface area of the corresponding inboard section.

Abstract: A vertical take off and landing (VTOL) aircraft is designed to be so efficient that it can be commercially competitive with runway dependent aircraft operating in a range of 100 to 1000 miles. Improvements include a high efficiency tilting rotor and wing design that enable both vertical takeoff and efficient high speed cruising, a high aspect ratio wing, and a variable speed propulsion system that is efficient in both hover and cruise flight. Preferred aircraft use thin inboard and outboard wings, thin rotor blades, and use efficient lightweight design to achieve unusually low empty weight fraction. Inventive methods include utilization of advanced design and analysis techniques, which allow for accurate prediction of an aircraft's physical behavior.

Abstract: A payload or cargo is delivered from a cargo hold of an aircraft during flight, by orienting the fuselage into a nose-up and tail-down position of at least 30 degrees off horizontal, and lowering the cargo from a cargo hold in the fuselage by means of one or more lines. Preferred vertical takeoff and landing (VTOL) aircraft include tilt-rotor or tilt-wing aircraft, and especially preferred aircraft are capable of generating control moments with their rotors to assist in orientating the fuselage of the aircraft into a nose-up and tail-down position.

Abstract: An electric linear actuator is disposed to pitch a blade of a hingeless, swashplateless rotor in rotary motion. This actuator can be equipped with an electric motor advantageously made fault tolerant by winding the motor for at least 4, 5, 6, 8, or even 12 phases. Rotational motion of the electric motor is preferably converted to a translatory linear actuator output motion using a planetary roller screw coupling the rotation of the motor with pitch of the blade. The output link of the actuator can be advantageously coupled to the planetary roller screw using an internal spherical joint providing an isolated load path through the actuator. It is contemplated that a preferred rotorcraft having an electric blade pitch actuator might also be equipped with a controller that could provide the vehicle with individual blade control, in which the pitch of any rotor blade can be controlled independently of the others.

Abstract: Substantial reduction in aircraft stowage space can be achieved by stacking aircraft using minimal or no folding of parts of the aircraft. This results in reduced complexity and reduced cost compared to other aircraft compact stowage schemes including for example fully folding an aircraft. Landing gear variable height, length, or orientation can be used to orient all or a portion of the aircraft for stowage. Alternately or in combination with such orientation by landing gear, other portions of the aircraft including tilting rotors and tilting nacelles can be oriented to achieve a geometric configuration conducive to compact stowage. In preferred embodiments, aircraft are moved relative to each other so that a portion of one aircraft is offset relative to a corresponding portion of the other. In especially preferred configurations, a portion of the first aircraft will overlap or lie on top of without touching a portion of the second aircraft.

Abstract: Systems and methods are provided in which an electrical control system independently effects acceleration of both driven and driving elements of a clutch to engage each other. In preferred embodiments the clutch is not a friction clutch, but a dog clutch, and forms part of a drive drain of a rotorcraft. A second clutch can be used, along with a mechanical interlock to prevent simultaneous engagement of the clutches. Speeds of the driven and driving elements can be sensed, and altered using at least one of a rotor, a brake, a generator, an electric motor, and a combustion motor.

Abstract: A rotorcraft is equipped with a rotor hub of large diameter in order to accommodate high loads from a hingeless rotor. In preferred embodiments, a rotorcraft has a rotor disposed on a mast with blades attached to a hub by means of a feather bearing that receives a shank of a blade. The hub is attached to non-rotating structure such as a tilting nacelle by means of a hub bearing. This facilitates the transfer of moments generated on the rotor to the airframe. The hub and feather bearings can be sized and arranged such that a feather bearing on a hub is disposed within an imaginary cylinder centered at a rotational axis of the hub and having a diameter no greater 1.2 times an inner diameter of the hub bearing. This can result in a large diameter hub and hub bearing capable of withstanding very large bending moments.

Abstract: Tilt-rotor aircraft experience increased efficiency and fuel economy by including wing extensions outboard of the tilting nacelles. Stall and buffeting during conversion from rotor-born hover to wing-born forward flight are reduced to an acceptable level using wide chord flaps deflected upwards by at least 15-20°, preferably in combination with leading edge slats. The outboard wing or wing portion is preferably has a span at least 25-40% of a span of the inboard section, and a total surface area at least 10-20% the total surface area of the corresponding inboard section.

Abstract: An aircraft is equipped with a spinnion coupling an inboard wing to a tilting nacelle. The spinnion is advantageously configured to extend across the nacelle from an inboard junction to an outboard junction, and terminates inside the inboard wing. This provides an efficient lightweight structure to support a nacelle and facilitate tilting of the nacelle. The spinnion, which can be configured to be at least partially disposed within the inboard wing, is advantageously concentric with the tilting axis in order to facilitate tilting of a nacelle. A cross-wing driveshaft can be included, disposed at least partly within the inboard wing, and can advantageously be configured to terminate inside the spinnion at a junction with a miter gearbox. The miter gearbox can be disposed at least partly within the spinnion but more preferably lies entirely within the spinnion, and functions to transfer power from an input shaft to the cross-wing driveshaft.

Abstract: An aircraft is equipped with hingeless rotors on tilting nacelles, and the tilt angles of the nacelles are controlled using either or both of an actuator and a mast moment generated by a hingeless rotor. An aircraft with two or more rotors on tilting nacelles can achieve control of yaw orientation by differential tilt of its nacelles or masts. Hingeless rotors can be manipulated to control a tilt angle of a mast by changing the rotor blade pitch to produce a mast moment. The rotor and nacelle tilt of a tiltrotor rotorcraft can be controlled and effected in order to manipulate the yaw orientation and flight mode of a rotorcraft such as a tiltrotor. The use of mast moment to control nacelle tilt angle can reduce tilt actuator loads and allows for the control of nacelle tilt even in the event of an actuator failure.

Abstract: A spar of a rotor blade having moderate depth transitions to a relatively much deeper shank over a relatively short distance. This rapid transition enables a low-weight blade root that is structurally efficient, offers a high moment capability, and enables high Mach number axial flow. A transition could advantageously reduce section depth by at least 15%, 20%, 30%, or even 40% over at most 5%, 6%, 10%, or 12% of a total length of the rotor blade. Such a transition could advantageously be accomplished using a cuff, which has interfaces with each of the spar and the shank. The rotor blade shank has a generally circular cross-section which allows for a rotary attachment to a hub, where the attachment may advantageously comprise a mechanical or elastomeric bearing. Preferred embodiments have a spar with a generally rectangular cross-section.

Abstract: Systems and methods are provided in which an electrical control system independently effects acceleration of both driven and driving elements of a clutch to engage each other. In preferred embodiments the clutch is not a friction clutch, but a dog clutch, and forms part of a drive drain of a rotorcraft. A second clutch can be used, along with a mechanical interlock to prevent simultaneous engagement of the clutches. Speeds of the driven and driving elements can be sensed, and altered using at least one of a rotor, a brake, a generator, an electric motor, and a combustion motor.

Abstract: Substantial reduction in aircraft stowage space can be achieved by stacking aircraft using minimal or no folding of parts of the aircraft. This results in reduced complexity and reduced cost compared to other aircraft compact stowage schemes including for example fully folding an aircraft. Landing gear variable height, length, or orientation can be used to orient all or a portion of the aircraft for stowage. Alternately or in combination with such orientation by landing gear, other portions of the aircraft including tilting rotors and tilting nacelles can be oriented to achieve a geometric configuration conducive to compact stowage. In preferred embodiments, aircraft are moved relative to each other so that a portion of one aircraft is offset relative to a corresponding portion of the other. In especially preferred configurations, a portion of the first aircraft will overlap or lie on top of without touching a portion of the second aircraft.

Abstract: Tapered layers of pre-cured composite material are integrated into a tapered, highly stressed laminate structure in order to provide improved compressive strength. The pre-cured composite material can advantageously be cured under tension as pultruded material, to further augment compressive strength. The thickness of composite layers can be tapered on their termination edges by mechanically abrading, chemical abrading, or other methods. Especially preferred embodiments include aircraft structural components such as wings, wing spars, wing skins, fuselage skins, rotor blades, propellers, and propeller blades. Preferred laminates can be constructed to have at least 6, 10, 30, 50, or 100 layers of material, and can have a maximum thickness of at least 0.15, 0.25, 0.5, 1.0, or 5.0 inches.