A method of blade fold for a tiltrotor aircraft includes configuring the tiltrotor aircraft in a flight ready position with a rotor system in an inverted-Y position, unlocking a first rotor blade of the rotor system to permit the first rotor blade to pivot relative to a yoke of the rotor system, restraining the first rotor blade to allow the first rotor blade to pivot relative to the yoke as the yoke is rotated, rotating the rotor system in a first direction so that the first rotor blade pivots closer to a second rotor blade, rotating the rotor system in a second direction to orient the rotor system into a modified inverted-Y position, unlocking a third rotor blade to allow the third rotor blade to pivot relative to the yoke as the yoke is rotated, and rotating the rotor system in the second direction so that the third rotor blade pivots closer to the second rotor blade.

A rotor blade attachment assembly for use with a rotor hub to which a rotor blade assembly is connected includes a hub extender having an inboard end and an outboard end. The inboard end of the hub extender is configured to form a connection with the rotor hub. A blade fold axis about which the rotor blade rotates relative to the rotor hub is defined at the connection. An inboard bearing is mounted within an interior of the hub extender adjacent the inboard end and an outboard hearing is mounted within the interior of the hub extender adjacent the outboard end. A tension torsion strap is operably coupled to the inboard bearing and the outboard bearing.

A rotor blade attachment assembly for use with a rotor hub to which a rotor blade assembly is connected includes a hub extender having an inboard end and an outboard end. The inboard end of the hub extender is configured to form a connection with the rotor hub. A blade fold axis about which the rotor blade rotates relative to the rotor hub is defined at the connection. An inboard bearing is mounted within an interior of the hub extender adjacent the inboard end and an outboard hearing is mounted within the interior of the hub extender adjacent the outboard end. A tension torsion strap is operably coupled to the inboard bearing and the outboard bearing.

A foldable rotor blade assembly includes a first section including a connector assembly including a plurality of through holes and a second section including a connector having a plurality of openings. The connector is receivable within a hollow interior of the first section. A plurality of fasteners insertable within the plurality of through holes and the plurality of openings. A fold assembly is operably coupled to both the first section and the second section. The fold assembly defines a blade fold axis about which the second section is rotatable to transform the rotor blade assembly between a normal configuration when the connector is received within the hollow interior of the first section, and a folded configuration when the connector has rotated outside of the hollow interior of the first section.

A foldable rotor blade assembly includes a first section including a connector assembly including a plurality of through holes and a second section including a connector having a plurality of openings. The connector is receivable within a hollow interior of the first section. A plurality of fasteners insertable within the plurality of through holes and the plurality of openings. A fold assembly is operably coupled to both the first section and the second section. The fold assembly defines a blade fold axis about which the second section is rotatable to transform the rotor blade assembly between a normal configuration when the connector is received within the hollow interior of the first section, and a folded configuration when the connector has rotated outside of the hollow interior of the first section.

A rotor blade assembly of an aircraft. The rotor blade assembly includes a blade attachment assembly rotatable with respect to a rotor hub assembly of the aircraft about a blade fold axis, and a pitch control assembly. The pitch control assembly includes a horn mount attachable to the rotor hub assembly, and a teeter bar hingedly attached to the horn mount at an interface, the interface defining a pitch control fold axis. The pitch control assembly is foldable about the pitch control fold axis when the pitch control fold axis is aligned with the blade fold axis.

A propulsion unit includes a motor rotor, propeller blades, and a pivot stop. The motor rotor spins about a central rotational axis. The propeller blades, including first and second propeller blades, each having a proximal base mounted to the motor rotor such that the propeller blades are rotatable about the central rotational axis. The second propeller blade is pivotally attached to the motor rotor to pivot about the central rotational axis independent of the motor rotor by a limited angle. The pivot stop mechanically limits an amount of pivoting of the second propeller blade relative to the first propeller blade.

A propulsion unit includes a motor rotor, propeller blades, and a pivot stop. The motor rotor spins about a central rotational axis. The propeller blades, including first and second propeller blades, each having a proximal base mounted to the motor rotor such that the propeller blades are rotatable about the central rotational axis. The second propeller blade is pivotally attached to the motor rotor to pivot about the central rotational axis independent of the motor rotor by a limited angle. The pivot stop mechanically limits an amount of pivoting of the second propeller blade relative to the first propeller blade.

A rotor blade for a rotary wing aircraft includes a rotor hub including a first flex-beam attachment member and a flex-beam assembly. The flex-beam assembly includes a flex-beam support member having an attachment end and a wrapping end. A first flex-beam includes a first end, a second end and an intermediate portion. The first end of the first flex-beam is connected at the first flex-beam attachment member and the second end of the first flex-beam being connected to the attachment end of the flex-beam support member. A second flex-beam includes first end portion, a second end portion and an intermediate section. The first end portion of the second flex-beam is connected at the first flex-beam attachment member, the second end portion of the second flex-beam being connected at the second flex-beam attachment member and the intermediate section extending about the wrapping end of the flex-beam support member.

An aircraft includes a closed wing, a fuselage at least partially disposed within a perimeter of the closed wing, and one or more spokes coupling the closed wing to the fuselage. A source of electric power is disposed within or attached to the closed wing, fuselage or one or more spokes. A plurality of electric motors are disposed within or attached to the one or more spokes in a distributed configuration. Each electric motor is connected to the source of electric power. A propeller is operably connected to each of the electric motors and proximate to a leading edge of the one or more spokes. One or more processors are communicably coupled to the plurality of electric motors. A longitudinal axis of the fuselage is substantially vertical in vertical takeoff and landing and stationary flight, and substantially in a direction of a forward flight in a forward flight mode.