Abstract: A replaceable web structure for an aircraft frame is described and includes a plurality of structural members fabricated from a first type of material, the replaceable web structure comprising a plurality of web members fabricated from thin sheets of a second type of material, wherein each of the web members is fastened to a web frame of one of the structural members to replace a web portion of the one of the structural members; wherein the second type of material is stronger than the first type of material such that one of the sheets of the second type of material is lighter weight than a sheet of equal strength of the first type of material.

Abstract: A ducted fan assembly has a central axis, a duct having an outer wall and an inner wall, a fan hub at least partially disposed on the central axis, a plurality of fan blades coupled to the fan hub, and a first stator. The first stator has a first end coupled to the inner wall, a second end coupled to the inner wall, and a hub interface disposed between the first end and the second end, wherein the hub interface is coupled to the fan hub.

Abstract: A duct for a ducted-rotor aircraft may include internal structural components such as a spindle that is supported by a fuselage of the aircraft, first and second annular spars that are attached to an end of the spindle, a central hub that supports a motor of the aircraft, a plurality of stators that extend from the central hub to the second spar, and a plurality of ribs that are attached to the first spar and the second spar at respective opposed ends. The spindle may include an attachment interface to which the first and second spars are attached. The attachment interface may be disposed at the second end of the spindle. The attachment interface may define first and second arc-shaped planar surfaces to which the first and second spars, respectively, are attached.

Abstract: A duct for a ducted-rotor aircraft may include an internal structure and an aerodynamic exterior skin that is adhesively bonded to the internal structure. The skin may include a leading-edge portion disposed at an inlet of the duct and an inner portion disposed along an interior of the duct. The inner portion of the skin may be bonded to the internal structure with a first bondline of adhesive and the leading-edge portion of the skin may be bonded to the inner portion of the skin with a second bondline of adhesive. One or both of the first and second bondlines of adhesive may be of non-uniform thickness to take up tolerance stackups between the inner portion of the skin, the leading-edge portion of the skin, and the internal structure.

Abstract: A ducted-rotor aircraft includes a fuselage, first and second ducts, and a spindle that is coupled to the fuselage. Each duct includes a rotor having a plurality of blades. The first and second ducts are coupled to opposed ends of the spindle. The spindle is rotatably coupled to the fuselage with first and second bearings. The first bearing is configured to react to radial loads and the second bearing is configured to react to both radial and axial loads. The spindle includes a shaft, first and second fittings secured to opposed ends of the shaft, and first and second attachment interfaces that are attachable to the first and second ducts. The attachment interfaces may be integral with the fittings. Alternatively, the fittings may be configured to be secured to the attachment interfaces with fasteners.

Abstract: A fitting for securing a rotor blade in pivotable engagement with a yoke that is coupled to a mast of an aircraft for rotation therewith about a mast axis has a body that extends from an inboard end to an outboard end. The body of the fitting has an opening that extends into the body from the outboard end and that is adapted to receive a root end of the blade. The body further has a first bearing race that is defined along an outer surface of the body and is located between the inboard and outboard ends. The body further has an array of apertures that is located between the inboard end and the first bearing race, each aperture adapted to receive a respective fastener for retaining the blade within the opening.

Abstract: A duct for a ducted-rotor aircraft includes a hub, a duct ring, and a plurality of stators that extend outward from the hub. The duct ring defines a trailing edge. The duct includes one or more fittings, such as a system of fittings. Each fitting has a body that defines a first attachment interface that is configured to couple to structure of the duct ring and a second attachment interface that is configured to couple to one of the plurality of stators. The first and second attachment interfaces are spaced from each other such that when the fittings are coupled to the duct ring and the plurality of stators, all or substantially all of each of the plurality of stators are located aft of the trailing edge of the duct ring.

Abstract: A bearing system includes an inboard bearing assembly and an outboard bearing assembly. The inboard bearing assembly includes an inboard fitting and an inboard race. The inboard fitting includes a plate with a convex mating surface and a first aperture formed through the plate for receiving a blade root of a rotor blade. The inboard race comprising a concave mating surface configured to receive the convex mating surface a second aperture formed the inboard race. The outboard bearing assembly includes an outboard bearing assembly comprising an outboard fitting having an aperture formed therethrough for receiving the blade root of the rotor blade.

Abstract: One embodiment is a rotor system comprising a duct ring; a hub disposed centrally to the duct ring; first and second stators each connected between the duct ring and the hub; first and second control vanes rotatably connected to the first and second stators, respectively; a structural hoop having a first end connected to the first control vane and a second end connected to the second control vane, the structural hoop for translating rotation of the first control vane about a vane axis to the second control vane; and a mechanism for restricting at least one of forward-aft movement and side-to-side movement of the structural hoop relative to the duct ring.

Abstract: A hub assembly for a ducted-rotor aircraft includes a plurality of stator supports, a first integral fitting that attaches to first ends of the stator supports, and a second integral fitting that attaches to second ends of the stator supports. The first fitting includes a plurality of motor attachment portions configured to locate and support a motor of the ducted-rotor aircraft, a plurality of fairing mounts configured to support attachment of an aerodynamic fairing to the hub assembly, and a plurality of stator locators configured to locate respective ones of the plurality of stator supports for attachment to the hub assembly. The first fitting has a body portion with an annular wall that supports the motor attachment portions, the fairing mounts, and the stator locators. The first fitting may be fabricated as a monolith that includes the body portion, motor attachment portions, fairing mounts, and stator locators.

Abstract: A ducted-rotor aircraft includes a fuselage, one or more ducts, and a spindle that rotatably couples the one or more ducts to the fuselage. Each duct includes a hub that is configured to support a rotor, a plurality of stators that are coupled to the hub, a duct ring that is coupled to the plurality of stators, and a fitting that is coupled to a first stator of the plurality of stators. The fitting has a tubular collar that defines a first aperture that extends through the fitting. The collar is configured to receive a portion of the spindle. The first stator includes a rib that is spaced inward from the fitting and that defines a second aperture that is aligned with the first aperture and that is configured to receive an end of the spindle.

Abstract: A bearing system includes an inboard bearing assembly and an outboard bearing assembly. The inboard bearing assembly includes an inboard fitting and an inboard race. The inboard fitting includes a plate with a convex mating surface and a first aperture formed through the plate for receiving a blade root of a rotor blade. The inboard race comprising a concave mating surface configured to receive the convex mating surface a second aperture formed the inboard race. The outboard bearing assembly includes an outboard bearing assembly comprising an outboard fitting having an aperture formed therethrough for receiving the blade root of the rotor blade.

Abstract: A replaceable web structure for an aircraft frame is described and includes a plurality of structural members fabricated from a first type of material, the replaceable web structure comprising a plurality of web members fabricated from thin sheets of a second type of material, wherein each of the web members is fastened to a web frame of one of the structural members to replace a web portion of the one of the structural members; wherein the second type of material is lighter weight than the first type of material; and wherein the second type of material is more heat-resistant than the first material.

Abstract: One embodiment is a rotor system comprising a duct ring; a hub disposed centrally to the duct ring; first and second stators each connected between the duct ring and the hub; first and second control vanes rotatably connected to the first and second stators, respectively; a structural hoop having a first end connected to the first control vane and a second end connected to the second control vane, the structural hoop for translating rotation of the first control vane about a vane axis to the second control vane; and a mechanism for restricting at least one of forward-aft movement and side-to-side movement of the structural hoop relative to the duct ring.

Abstract: A ducted-rotor aircraft includes a fuselage, one or more ducts, and a spindle that rotatably couples the one or more ducts to the fuselage. Each duct includes a hub that is configured to support a rotor, a plurality of stators that are coupled to the hub, a duct ring that is coupled to the plurality of stators, and a fitting that is coupled to a first stator of the plurality of stators. The fitting has a tubular collar that defines a first aperture that extends through the fitting. The collar is configured to receive a portion of the spindle. The first stator includes a rib that is spaced inward from the fitting and that defines a second aperture that is aligned with the first aperture and that is configured to receive an end of the spindle.

Abstract: A duct for a ducted-rotor aircraft includes a hub, a duct ring, and a plurality of stators that extend outward from the hub. The duct ring defines a trailing edge. The duct includes one or more fittings, such as a system of fittings. Each fitting has a body that defines a first attachment interface that is configured to couple to structure of the duct ring and a second attachment interface that is configured to couple to one of the plurality of stators. The first and second attachment interfaces are spaced from each other such that when the fittings are coupled to the duct ring and the plurality of stators, all or substantially all of each of the plurality of stators are located aft of the trailing edge of the duct ring.

Abstract: A ducted-rotor aircraft includes a fuselage, first and second ducts, and a spindle that is coupled to the fuselage. Each duct includes a rotor having a plurality of blades. The first and second ducts are coupled to opposed ends of the spindle. The spindle is rotatably coupled to the fuselage with first and second bearings. The first bearing is configured to react to radial loads and the second bearing is configured to react to both radial and axial loads. The spindle includes a shaft, first and second fittings secured to opposed ends of the shaft, and first and second attachment interfaces that are attachable to the first and second ducts. The attachment interfaces may be integral with the fittings. Alternatively, the fittings may be configured to be secured to the attachment interfaces with fasteners.

Abstract: A duct for a ducted-rotor aircraft may include internal structural components such as a spindle that is supported by a fuselage of the aircraft, first and second annular spars that are attached to an end of the spindle, a central hub that supports a motor of the aircraft, a plurality of stators that extend from the central hub to the second spar, and a plurality of ribs that are attached to the first spar and the second spar at respective opposed ends. The spindle may include an attachment interface to which the first and second spars are attached. The attachment interface may be disposed at the second end of the spindle. The attachment interface may define first and second arc-shaped planar surfaces to which the first and second spars, respectively, are attached.

Abstract: A hub assembly for a ducted-rotor aircraft includes a plurality of stator supports, a first integral fitting that attaches to first ends of the stator supports, and a second integral fitting that attaches to second ends of the stator supports. The first fitting includes a plurality of motor attachment portions configured to locate and support a motor of the ducted-rotor aircraft, a plurality of fairing mounts configured to support attachment of an aerodynamic fairing to the hub assembly, and a plurality of stator locators configured to locate respective ones of the plurality of stator supports for attachment to the hub assembly. The first fitting has a body portion with an annular wall that supports the motor attachment portions, the fairing mounts, and the stator locators. The first fitting may be fabricated as a monolith that includes the body portion, motor attachment portions, fairing mounts, and stator locators.

Abstract: A duct for a ducted-rotor aircraft may include an internal structure and an aerodynamic exterior skin that is adhesively bonded to the internal structure. The skin may include a leading-edge portion disposed at an inlet of the duct and an inner portion disposed along an interior of the duct. The inner portion of the skin may be bonded to the internal structure with a first bondline of adhesive and the leading-edge portion of the skin may be bonded to the inner portion of the skin with a second bondline of adhesive. One or both of the first and second bondlines of adhesive may be of non-uniform thickness to take up tolerance stackups between the inner portion of the skin, the leading-edge portion of the skin, and the internal structure.