Blade fold method and apparatus for a tilt rotor hub
A folding rotor blade assembly for an aircraft a yoke, an inboard beam coupled to the yoke, an inboard centrifugal force bearing coupled to the inboard beam, a grip coupled to the inboard beam, an outboard bearing housing coupled to the grip, and a rotor blade pivotally coupled to the grip by a blade fold bolt that is positioned outboard of the outboard bearing housing.
1. A folding rotor blade assembly for an aircraft, the folding rotor blade assembly comprising:
a yoke;
an inboard beam coupled to the yoke;
an inboard centrifugal force bearing coupled to the inboard beam;
a grip coupled to the inboard beam;
an outboard bearing housing coupled to the grip; and
a rotor blade pivotally coupled to the grip by a blade fold bolt that is positioned outboard of the outboard bearing housing.
2. The folding rotor blade assembly of claim 1 , comprising a blade fold support coupled to the grip by the blade fold bolt.
3. The folding rotor blade assembly of claim 2 , comprising a lock assembly coupled to the blade fold support and configured to lock the rotor blade in an extended position.
4. The folding rotor blade assembly of claim 3 , wherein:
the rotor blade comprises a blade tang that extends from an inboard end of the rotor blade toward the yoke; and
the lock assembly includes a tab that, in a first position, abuts the blade tang and prevents the rotor blade from rotating relative to the blade fold support and, in a second position, allows the rotor blade to rotate relative to the blade fold support.
5. The folding rotor blade assembly of claim 2 , wherein the blade fold bolt passes through the blade fold support, the rotor blade, and the grip.
6. The folding rotor blade assembly of claim 1 , comprising:
an inboard bearing assembly coupled between the inboard beam and the yoke;
a yoke flexure extending from the yoke and coupled to the outboard bearing housing; and
an outboard bearing assembly coupled between the outboard bearing housing and the yoke flexure.
7. The folding rotor blade assembly of claim 6 , wherein the yoke flexure and the outboard bearing assembly are coupled together by a spindle.
8. The folding rotor blade assembly of claim 6 , wherein the inboard bearing assembly comprises an inboard shear bearing and the inboard centrifugal force bearing.
9. The folding rotor blade assembly of claim 6 , wherein the outboard bearing assembly comprises an outboard shear bearing.
10. The folding rotor blade assembly of claim 8 , wherein the inboard shear bearing is coupled to the inboard centrifugal force bearing.
11. A folding rotor blade assembly for an aircraft, the folding rotor blade assembly comprising:
a yoke connected to and axially aligned with a hub spring assembly;
an inboard beam housing an inboard centrifugal force bearing, the inboard beam connected to the yoke;
a grip connected at a first end to the inboard beam;
an outboard bearing housing connected to a second end of the grip;
an outboard bearing assembly coupled between the outboard bearing housing and the second end of the grip;
a blade fold support connected to the grip and the outboard bearing housing; and
a rotor blade connected to the grip at a pivotal connection positioned outboard of the outboard bearing assembly.
12. The folding rotor blade assembly of claim 11 , wherein the pivotal connection comprises a blade fold bolt that passes through the rotor blade and the grip.
13. The folding rotor blade assembly of claim 12 , comprising a lock assembly coupled to the blade fold support and configured to lock the rotor blade in an extended position.
14. The folding rotor blade assembly of claim 13 , wherein:
the rotor blade comprises a blade tang that extends from an inboard end of the rotor blade toward the yoke; and
the lock assembly includes a tab that in a first position abuts the blade tang and prevents the rotor blade from rotating relative to the blade fold support and in a second position allows the rotor blade to rotate relative to the blade fold support.
15. The folding rotor blade assembly of claim 13 , comprising:
an inboard bearing assembly coupled between the inboard beam and the yoke;
a yoke flexure extending from the yoke and coupled to the outboard bearing housing; and
an outboard bearing assembly coupled between the outboard bearing housing and the yoke flexure.
16. A method comprising:
pitching a first rotor blade of a rotor blade assembly, the rotor blade assembly comprising:
an inboard bearing assembly comprising an inboard centrifugal force bearing and connected to a yoke and a grip;
an outboard bearing assembly connected to the yoke and the grip;
a blade fold support connected to the grip; and
wherein the first rotor blade is pivotally connected to the blade fold support via a blade fold bolt, the blade fold support configured to prevent a pivoting rotation of the first rotor blade relative to the yoke when the blade fold support is in a locked configuration, the blade fold bolt providing a pivot axis outboard of the outboard bearing assembly;
unlocking the first rotor blade to allow the first rotor blade to pivot relative to the yoke; and
rotating the first rotor blade about the pivot axis.
17. The method of claim 16 , wherein the rotor blade assembly further comprises a lock assembly attached to the blade fold support.
18. The method of claim 17 , wherein the unlocking comprises moving a tab of the lock assembly to allow the first rotor blade to pivot relative to the yoke.
19. The method of claim 16 , comprising pitching and unlocking a second rotor blade.
20. The method of claim 19 , wherein the first and second rotor blades are rotated to be generally parallel with each other and a third rotor blade.