# US 2013/0156575 A1 · Blade-Pitch Control System with Feedback Lever

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 2013/0156575 A1
- Document ID: US20130156575A1
- Status: Published application
- Kind: A1
- Application number: 13/325,679
- Filed: 2011-12-14
- Published: 2013-06-20
- Earliest claimed: 2011-12-14
- Assignees: Bell Helicopter Textron Inc.
- Inventors: Frank B. Stamps
- Web page: https://patentgrep.com/patent/US20130156575A1

## CPC

- B64C 27/605: including swash plate, spider or cam mechanisms
- B64C: AEROPLANES; HELICOPTERS

## Abstract

The present application includes a blade-pitch control system for controlling a pitch angle of each of a plurality of blades on an aircraft rotor. A feedback lever associated with each blade is pivotally mounted to the rotating portion of a swashplate assembly. A pitch link connects an output arm of a lever to a pitch horn of a corresponding blade, and a feedback link connects the input arm of the lever to a yoke. Flapping motion of the yoke causes motion of the feedback link, and this motion causes corresponding rotation of the lever. Rotation of the lever causes motion of the pitch link, which changes the pitch angle of the attached blade. This provides for selected pitch-flap coupling between flapping motion of the yoke and pitch motion of the blades.

## Claims

### Claim 1

A blade-pitch control system for controlling a pitch angle of each of a plurality of blades on an aircraft rotor, the blades being rotatably connected to a yoke for rotation with a rotor mast, the control system comprising:
a swashplate assembly having a non-rotating portion and a rotating portion;
a feedback lever associated with each blade, each lever being pivotally mounted to the rotating portion of the swashplate assembly, an input arm and an output arm extending from opposing sides of a pivot axis of the lever, the arms moving in opposite directions when the lever is pivoted relative to the rotation portion;
a pitch link connecting the output arm to a pitch horn of a corresponding blade;
a feedback link connecting the input arm to the yoke;
wherein flapping motion of the yoke causes motion of the feedback link, and this motion causes corresponding rotation of the lever and motion of the pitch link, providing for selected pitch-flap coupling between flapping motion of the yoke and pitch motion of the blades.

### Claim 2 (depends on 1)

The blade-pitch control system of claim 1, wherein the feedback link is connected to the yoke through a portion of a gimbal connecting the yoke to the mast.

### Claim 3 (depends on 1)

The blade-pitch control system of claim 1, further comprising:
a pivot shaft for pivotal mounting of each lever, each pivot shaft extending radially outward from the rotating portion of the swashplate assembly.

### Claim 4 (depends on 1)

The blade-pitch control system of claim 1, wherein each lever has arms of approximately equal length.

### Claim 5 (depends on 1)

The blade-pitch control system of claim 1, wherein each lever has arms of unequal length.

### Claim 6

A method of controlling a pitch angle of each of a plurality of blades on an aircraft rotor, the blades being rotatably connected to a yoke for rotation with a rotor mast, the method comprising:
(a) pivotally connecting a feedback lever associated with each blade to a rotating portion of a swashplate assembly, an input arm and an output arm extending from opposing sides of a pivot axis of the lever, the arms moving in opposite directions when the lever is pivoted relative to the rotation portion;
(b) connecting the output arm to a pitch horn of a corresponding blade with a pitch link;
(c) connecting the input arm to the yoke with a feedback link; and
(d) changing a pitch angle of a blade by introducing feedback due to flapping motion of the yoke and the corresponding motion of the lever and the pitch link.

### Claim 7 (depends on 6)

The method of claim 6, wherein step (c) comprises connecting the input arm to the yoke through a portion of a gimbal connecting the yoke to the mast.

### Claim 8 (depends on 6)

The method of claim 6, wherein step (a) comprises providing a pivot shaft for pivotal mounting of each lever, each pivot shaft extending radially outward from the rotating portion of the swashplate assembly.

### Claim 9 (depends on 6)

The method of claim 6, wherein step (a) comprises configuring each lever to have arms of approximately equal length.

### Claim 10 (depends on 6)

The method of claim 6, wherein step (a) comprises configuring each lever to have arms of unequal length.

### Claim 11

An aircraft having a blade-pitch control system for controlling a pitch angle of each of a plurality of blades on an aircraft rotor, the blades being rotatably connected to a yoke for rotation with a rotor mast, the control system comprising:
a swashplate assembly having a non-rotating portion and a rotating portion;
a feedback lever associated with each blade, each lever being pivotally mounted to the rotating portion of the swashplate assembly, an input arm and an output arm extending from opposing sides of a pivot axis of the lever, the arms moving in opposite directions when the lever is pivoted relative to the rotation portion;
a pitch link connecting the output arm to a pitch horn of a corresponding blade;
a feedback link connecting the input arm to the yoke;
wherein flapping motion of the yoke causes motion of the feedback link, and this motion causes corresponding rotation of the lever and motion of the pitch link, providing for selected pitch-flap coupling between flapping motion of the yoke and pitch motion of the blades.

### Claim 12 (depends on 11)

The aircraft of claim 11, wherein the feedback link is connected to the yoke through a portion of a gimbal connecting the yoke to the mast.

### Claim 13 (depends on 11)

The aircraft of claim 11, further comprising:
a pivot shaft for pivotal mounting of each lever, each pivot shaft extending radially outward from the rotating portion of the swashplate assembly.

### Claim 14 (depends on 11)

The aircraft of claim 11, wherein each lever has arms of approximately equal length.

### Claim 15 (depends on 11)

The aircraft of claim 11, wherein each lever has arms of unequal length.