Passive hub flapping lock

1. A passive hub flapping lock comprising:

one or more stop wedges;

one or more frames coupled to the one or more stop wedges;

one or more rods coupled to the one or more frames, and each rod comprising a bracket;

one or more lever arms, each lever arm rotatably coupled to a pivot and coupled at a first lever arm end to one of the one or more rods at the bracket of the rod;

one or more weight sets, each weight set coupled to a second lever arm end; and

one or more pivot torsion springs, each pivot torsion spring positioned at a pivot and biased to hold the flapping lock in an engaged position when stationary or at a rotational speed below a specified rotational speed;

wherein the flapping lock is in an engaged position when stationary or at a rotational speed below the specified rotational speed and wherein the flapping lock is in a disengaged position when at a rotational speed above the specified rotational speed and the one or more weight sets move outward, rotating the one or more lever arms.

2. The flapping lock of claim 1 , wherein the one or more stop wedges comprise an elastomeric material, a foam, a soft metal, or a combination of two or more of those materials.

3. The flapping lock of claim 1 , wherein the one or more rods are held in place or stabilized by one or more rod sleeves.

4. The flapping lock of claim 3 , wherein at least a portion of each of the one or more rod sleeves adjacent to a mast sleeve or a mast is coated with one or more substances to reduce a friction of a motion of the one or more rod sleeves against the mast sleeve or the mast.

5. The flapping lock of claim 3 , wherein the rod sleeves comprise linear ball bearings.

6. The flapping lock of claim 1 , wherein each of the one or more lever arms is coupled to one of the one or more rods with a roller bearing directly or with a link.

7. The flapping lock of claim 1 , wherein each of the one or more weight sets is adjustable to set the specified rotational speed.

8. The flapping lock of claim 1 , wherein at least a portion of a mast sleeve, a mast, or each frame is coated with one or more substances to reduce a friction of a motion of the one or more frames against the mast sleeve or the mast.

9. A method of preventing hub flapping comprising:

providing one or more stop wedges mounted on one or more frames to be inserted into a space between a mast sleeve or a mast and a rotor yoke to prevent hub flapping;

lowering the one or more stop wedges into the space when stationary or at a rotational speed below a specified rotational speed;

raising the one or more stop wedges out of the space at the specified rotational speed;

keeping the one or more stop wedges out of the space when above the specified rotational speed; and

controlling a position of the one or more stop wedges with one or more weight sets coupled to one or more lever arms that are coupled to the one or more stop wedges, wherein the one or more weight sets move outward at the specified rotational speed, moving the lever arms such that the one or more stop wedges are raised from the space.

10. The method of claim 9 , wherein the one or more stop wedges comprise an elastomeric material, a foam, a soft metal, or a combination of two or more of those materials.

11. The method of claim 9 , wherein one or more rods couple the one or more stop wedges with the one or more lever arms.

12. The method of claim 11 , wherein each of the one or more lever arms is coupled to one of the one or more rods with a roller bearing directly or with a link.

13. The method of claim 11 , wherein the one or more rods are held in place or stabilized by one or more rod sleeves.

14. The method of claim 13 , wherein at least a portion of each of the one or more rod sleeves adjacent to the mast sleeve or the mast is coated with one or more substances to reduce a friction of a motion of the one or more rod sleeves against the mast sleeve or the mast.

15. The method of claim 13 , wherein the one or more rod sleeves comprise linear ball bearings.

16. The method of claim 9 , wherein each of the one or more weight sets is adjustable to set the specified rotational speed.

17. The method of claim 9 , wherein at least a portion of the mast sleeve, the mast, or each frame is coated with one or more substances to reduce a friction of a motion of the one or more frames against the mast sleeve or the mast.

18. A rotorcraft comprising:

a fuselage;

one or more engines coupled to the fuselage;

one or more rotor assemblies coupled to the one or more engines; and

each of the one or more rotor assemblies comprising a flapping lock, the flapping lock comprising:

one or more stop wedges;

one or more frames coupled to the one or more stop wedges;

one or more rods coupled to the one or more frames, and each rod comprising a bracket;

one or more lever arms, each lever arm rotatably coupled to a pivot and coupled at a first lever arm end to one of the one or more rods at the bracket of the rod;

one or more weight sets, each weight set coupled to a second lever arm end; and

one or more pivot torsion springs, each pivot torsion spring positioned at a pivot and biased to hold the flapping lock in an engaged position when stationary or at a rotational speed below a specified rotational speed;

wherein the flapping lock is in an engaged position when stationary or at a rotational speed below the specified rotational speed and in a disengaged position when at a rotational speed above the specified rotational speed and the one or more weight sets move outward, rotating the one or more lever arms.