Hinged rotor blade to provide passive variable pitch

1. A propeller for an aircraft, comprising:

a hub;

a blade including a neck portion angled away from a plane of rotation of the hub, wherein the blade has a longitudinal axis extending through a center of the blade and running from a tip of the blade to an end of the neck portion; and

a hinge including a pivotal link, the hinge connecting the blade to the hub, wherein:

the hinge has an axis of hinge rotation that is offset from a line perpendicular to the longitudinal axis of the blade; and

the hinge responds to forces acting on the blade to vary a pitch of the blade including causing the blade to be at a lower pitch and higher dihedral angle in a vertical flight mode relative to a forward flight mode, the dihedral angle being an angle of the blade relative to the plane of rotation of the hub.

2. The propeller of claim 1 , wherein said hinge comprises a single pivotal link.

3. The propeller of claim 1 , wherein said hinge comprises a pin positioned on said axis of hinge rotation.

4. The propeller of claim 1 , wherein said hinge permits the blade to fold back towards a central axis of the hub if no force is being applied to rotate the propeller.

5. The propeller of claim 1 , wherein said hinge is integrated with a structure mounted fixedly to said hub.

6. The propeller of claim 5 , wherein said structure mounted fixedly to said hub includes at least one tab portion.

7. The propeller of claim 6 , wherein said hinge comprises a pin positioned on said axis of hinge rotation and said pin runs through a transverse hole in an end of the blade nearest to the hub and at least one hole on said at least one tab portion.

8. The propeller of claim 1 , wherein said hub comprises a nose cone.

9. The propeller of claim 1 , wherein said hub comprises a nose structure.

10. The propeller of claim 1 , wherein the hinge is oriented in a plane that is in the plane of rotation of the hub.

11. The propeller of claim 1 , wherein the hinge comprises a forward end associated with a leading edge of the blade and a rearward end associated with a trailing edge of the blade, and wherein the forward end lies further from a geometric center of the hub than the rearward end.

12. The propeller of claim 1 , wherein the neck portion has a neck portion longitudinal axis that is substantially orthogonal to the axis of hinge rotation and wherein a substantial part of the blade is coupled to the hub by the neck portion.

13. The propeller of claim 1 , wherein a substantial part of the blade comprises a primary airfoil portion of the blade.

14. The propeller of claim 13 , wherein the neck portion is positioned between the primary airfoil portion and the hinge.

15. The propeller of claim 1 , wherein in a first propeller orientation associated with a first mode of flight, the blade deploys to a first stable position associated with a first pitch, and in a second propeller orientation associated with a second mode of flight the blade rotates about the axis of hinge rotation to a second stable position associated with a second pitch.

16. The propeller of claim 15 , wherein the first propeller orientation comprises a substantially horizontal plane of rotation.

17. The propeller of claim 15 , wherein the second propeller orientation comprises a substantially vertical plane of rotation.

18. The propeller of claim 15 , wherein the first mode of flight corresponds to the vertical flight mode.

19. The propeller of claim 15 , wherein the second mode of flight corresponds to the forward flight mode.

20. The propeller of claim 1 , further comprising a stop that prevents the blade from moving beyond a point associated with the stop.