Hinged rotor blade to provide passive variable pitch

A propeller for an aircraft, comprising:

• a hub;
• a blade connected to the hub via a hinge having a single pivotal link, wherein the blade has a longitudinal axis extending through a center of the blade and running from a root of the blade to a tip of the blade, and wherein the hinge has an axis of hinge rotation that is oriented at a non-zero angle to a tangent line tangent to the hub, the tangent line intersecting said longitudinal axis;
• and
• a neck portion coupling the blade and the hub, wherein the neck portion is angled away from a plane of rotation of the hub to vary pitch of the blade as the hinge rotates about the axis of hinge rotation;
• wherein:
• the aircraft is configured to transition between a forward flight mode and a vertical flight mode,
• for a same rotational speed, the propeller passively decreases pitch in the vertical flight mode relative to the forward flight mode at the same rotational speed,
• in the forward flight mode, the hinge responds to a first combination of centrifugal force and thrust force by causing the blade to move outward from a central axis of the hub to sweep outward from the plane of rotation of the hub to a first threshold point, and
• in the vertical flight mode, the hinge responds to a second combination of centrifugal force and thrust force by causing the blade to move outward from the central axis of the hub to sweep upward from the plane of rotation of the hub to a second threshold point, the second threshold point being farther from the plane of rotation of the hub than the first threshold point.