Rotor Assembly with High Lock-Number Blades

• US 20170320567A1
• Filed: 02/14/2017
• Published: 11/09/2017
• Est. Priority Date: 02/16/2016
• Status: Active Grant

• Current Assignee: Bell Helicopter Textron Incorporated (Textron Inc)
• Original Assignee: Bell Helicopter Textron Incorporated (Textron Inc)
• Inventors: Miller, Gary, Stamps, Frank B., Choi, Jouyoung Jason, Parham, JR., Thomas C., Ewing, Alan, Rauber, Richard E.
• Granted Patent: US 10,472,057 B2
• Time in Patent Office: Days
• CPC Class Codes: B64C 2027/7255 using one or more swash plates
• CPC Class Codes: B64C 27/33 having flexing arms
• CPC Class Codes: B64C 27/605 including swash plate, spider or cam mechanisms
• CPC Class Codes: B64C 27/635 specially for controlling lag-lead movements of blades
• CPC Class Codes: B64C 27/72 Means acting on blades
• CPC Class Codes: B64C 29/0033 the propellers being tiltable relative to the fuselage

Abstract

An aircraft rotor assembly has a central hub and a plurality of rotor blades coupled to the hub for rotation with the hub about an axis, each blade having a Lock number of approximately 5 or greater. A lead-lag pivot for each blade is formed by a flexure coupling the associated blade to the hub. Each pivot is a radial distance from the axis and allows for in-plane lead-lag motion of the associated blade relative to the hub, each pivot allowing for in-plane motion from a neutral position of at least 1 degree in each of the lead and lag directions. Elastic deformation of the flexure produces a biasing force for biasing the associated blade toward the neutral position, and the biasing force is selected to achieve a first in-plane frequency of greater than 1/rev for each blade.

Claims

1. An aircraft rotor assembly, comprising:

a central hub;

a plurality of rotor blades coupled to the hub for rotation with the hub about an axis, each blade having a Lock number of approximately 5 or greater; and

a lead-lag pivot for each blade formed by a flexure coupling the associated blade to the hub, each pivot being a radial distance from the axis and allowing for in-plane lead-lag motion of the associated blade relative to the hub, each pivot allowing for in-plane motion from a neutral position of at least 1 degree in each of the lead and lag directions;

wherein elastic deformation of the flexure produces a biasing force for biasing the associated blade toward the neutral position,

wherein the biasing force is selected to achieve a first in-plane frequency of greater than 1/rev for each blade.

2. The assembly of claim 1, wherein, for each flexure, an out-of-plane bending stiffness is greater that an in-plane bending stiffness.

3. The assembly of claim 1, further comprising:

a discrete flap hinge for each blade.

4. The assembly of claim 1, further comprising:

a gimbal configured to allow pivoting of the hub relative to the axis about flap axes perpendicular to the axis.

5. The assembly of claim 1, further comprising:

a control system for collective and cyclic control of the pitch of each of the blades.

6. The assembly of claim 1, wherein the flexure comprises an inboard section and an outboard section, the outboard section having a smaller chordwise thickness than the inboard section.

7. The assembly of claim 1, wherein the flexure is beam having a generally rectangular cross section.

8. The assembly of claim 1, wherein the blades are capable of folding through selective rotation relative to the flexure when the assembly is not in operation.

9. An aircraft rotor assembly, comprising:

a central hub;

a plurality of rotor blades coupled to the hub for rotation with the hub about an axis, each blade having a Lock number of approximately 5 or greater;

a lead-lag pivot for each blade formed by a flexure coupling the associated blade to the hub, each pivot being a radial distance from the axis and allowing for in-plane lead-lag motion of the associated blade relative to the hub, each pivot allowing for in-plane motion from a neutral position of at least 1 degree in each of the lead and lag directions; and

a discrete flap hinge for each blade;

wherein elastic deformation of the flexure produces a biasing force for biasing the associated blade toward the neutral position,

wherein the biasing force is selected to achieve a first in-plane frequency of greater than 1/rev for each blade.

10. The assembly of claim 9, wherein, for each flexure, an out-of-plane bending stiffness is greater that an in-plane bending stiffness.

11. The assembly of claim 9, further comprising:

a control system for collective and cyclic control of the pitch of each of the blades.

12. The assembly of claim 9, wherein the flexure comprises an inboard section and an outboard section, the outboard section having a smaller chordwise thickness than the inboard section.

13. The assembly of claim 9, wherein the flexure is beam having a generally rectangular cross section.

14. The assembly of claim 9, wherein the blades are capable of folding through selective rotation relative to the flexure when the assembly is not in operation.

15. An aircraft rotor assembly, comprising:

a central hub;

a plurality of rotor blades coupled to the hub for rotation with the hub about an axis, each blade having a Lock number of approximately 5 or greater;

a lead-lag pivot for each blade formed by a flexure coupling the associated blade to the hub, each pivot being a radial distance from the axis and allowing for in-plane lead-lag motion of the associated blade relative to the hub, each pivot allowing for in-plane motion from a neutral position of at least 1 degree in each of the lead and lag directions; and

a gimbal configured to allow pivoting of the hub relative to the axis about flap axes perpendicular to the axis;

wherein elastic deformation of the flexure produces a biasing force for biasing the associated blade toward the neutral position,

wherein the biasing force is selected to achieve a first in-plane frequency of greater than 1/rev for each blade.

16. The assembly of claim 15, wherein, for each flexure, an out-of-plane bending stiffness is greater that an in-plane bending stiffness.

17. The assembly of claim 15, further comprising:

a control system for collective and cyclic control of the pitch of each of the blades.

18. The assembly of claim 15, wherein the flexure comprises an inboard section and an outboard section, the outboard section having a smaller chordwise thickness than the inboard section.

19. The assembly of claim 15, wherein the flexure is beam having a generally rectangular cross section.

20. The assembly of claim 15, wherein the blades are capable of folding through selective rotation relative to the flexure when the assembly is not in operation.