EP-4739577-A1 - ROTOR DAMPING MECHANISM

Abstract

A helicopter rotor head (100) is disclosed. The helicopter rotor head comprises a rotor blade (202) comprising a first end region; a blade grip (101) comprising an opening, wherein the first end region of the rotor blade is pivotably held in the opening; a damping arrangement comprising a rigid connection (201, 203) to the rotor blade, a pivotable connection (103, 104, 117, 142) to the blade grip, and a rigid element (112) arranged to pivot with pivoting movement of the rotor blade. The damping arrangement is configured to resist the pivoting movement within a selected range and to prevent the pivoting movement beyond the selected range.

Inventors

• MANLEY, ROBERT
• EMPTAGE, Michael

Assignees

• Certo Aerospace Limited

Dates

Publication Date

20260513

Application Date

20240708

Claims (13)

1. 1. A helicopter rotor head comprising: a rotor blade comprising a first end region; a blade grip comprising an opening, wherein the first end region of the rotor blade is pivotably held in the opening; a damping arrangement comprising a rigid connection to the rotor blade, a pivotable connection to the blade grip, and a rigid element arranged to pivot with pivoting movement of the rotor blade; wherein the damping arrangement is configured to resist the pivoting movement within a selected range and to prevent the pivoting movement beyond the selected range.
2. 2. The helicopter rotor head of claim 1 , wherein the rigid connection to the rotor blade is selectively releasable to allow the pivoting movement of the blade to beyond the selected range.
3. 3. A helicopter rotor head comprising: a rotor blade comprising a first end region; a blade grip comprising an opening, wherein the first end region of the rotor blade is pivotably held in the opening; a damping arrangement comprising a rigid connection to the rotor blade, a pivotable connection to the blade grip, and a rigid element arranged to pivot with pivoting movement of the rotor blade; wherein the damping arrangement is configured to prevent pivoting movement of the blade beyond a selected range; wherein the rigid connection to the rotor blade is selectively releasable to allow the pivoting movement of the blade to beyond the selected range.
4. 4. The helicopter rotor head of claim 3, wherein the damping arrangement is configured to resist the pivoting movement within the selected range.
5. 5. The helicopter rotor head of any preceding claim, wherein the damping arrangement comprises at least one damping element urged against the rigid element to resist the pivoting movement.
6. 6. The helicopter rotor head of claim 5, wherein the rigid element is sandwiched between two of said damping elements.
7. 7. The helicopter rotor head of any preceding claim, wherein the pivotable connection is provided by a pin which extends into the blade grip and into at least one of the rigid element and the rotor blade.
8. 8. The helicopter rotor head of claim 7, wherein the rigid element comprises a hole for receiving the pin.
9. 9. The helicopter rotor head of any preceding claim, wherein the rigid connection is provided by a sprung pin.
10. 10. The helicopter rotor head of any preceding claim wherein the damping arrangement further comprises a slot in a surface of the blade grip, wherein said slot is sized to allow the pivoting movement of the rigid element within the selected range.
11. 11. The helicopter rotor head of claim 10 wherein a rigid element comprises a tang portion, and the tang portion is arranged in the slot.
12. 12. The helicopter rotor head of any preceding claim, wherein the rigid connection is arranged radially outwardly of the pivotable connection.
13. 13. The helicopter rotor head of any preceding claim, wherein the end face of the end portion of the has a curved surface.

Description

Rotor Damping Mechanism Technical Field The present invention relates to rotor heads for helicopters, and more particularly to rotor head damping mechanisms. Background Helicopters typically include a plurality of rotor blades connected to a rotor head, which is driven to cause rotation of the blades and thereby provide lift to the aircraft. However, as the rotor blades spin, they undergo other types of motion relative to the rotor head which need to be accounted for. During flight, the angle of attack of each rotor blade may vary. For example, over each rotation each blade may flap up and down to offset dissymmetry of lift between the advancing and retreating halves of the rotor disk. Such motion may cause the blades to skip forwards and backwards in their path of rotation each cycle, due to the principle of conservation of angular momentum. When rotor blades rise out of their plane of rotation, their centre on mass moves closer to the rotational axis, causing the moment of inertia of the blade to decrease. Therefore, to conserve angular momentum, the blade speeds up, causing it to skip ahead in its path. This effect causes a slight deformation of the blade, and the restoring force from the deformation causes the blade to oscillate back and forth, known as lead-lag. The rotor head therefore needs to be configured to allow for this relative motion. However, over time these oscillations may cause damage to the blade and/or the rotor head and may inhibit proper functioning of the aircraft. Summary of Invention Embodiments of the present invention aim to address the above problems and others. Aspects of the disclosure are set out in the independent claims and optional features are set out in the dependent claims. Aspects of the disclosure may be provided in conjunction with each other, and features of one aspect may be applied to other aspects. In an aspect, there is provided a helicopter rotor head comprising: a rotor blade comprising a first end region, a blade grip comprising an opening, wherein the first end region of the rotor blade is pivotably held in the opening, a damping arrangement comprising a rigid connection to the rotor blade, a pivotable connection to the blade grip, and a rigid element arranged to pivot with pivoting movement of the rotor blade, wherein the damping arrangement is configured to resist the pivoting movement within a selected range. The rigid connection to the rotor blade may be selectively releasable to allow the pivoting movement of the blade beyond the selected range. In another aspect, there is provided a helicopter rotor head comprising a rotor blade comprising a first end region, a blade grip comprising an opening wherein the first end region of the rotor blade is pivotably held in the opening, a damping arrangement comprising a rigid connection to the rotor blade, a pivotable connection to the blade grip, and a rigid element arranged to pivot with pivoting movement of the rotor blade, wherein the damping arrangement is configured to prevent pivoting movement of the blade beyond a selected range, wherein the rigid connection to the rotor blade is selectively releasable to allow the pivoting movement of the blade to beyond the selected range. The rigid connection may be provided between the rigid element and the rotor blade. The helicopter may comprise a plurality of said rotor blades, e.g. three, and a corresponding plurality of blade grips and damping arrangements. The damping arrangement may be configured to resist the pivoting movement within the selected range. The damping arrangement may comprise at least one damping element urged against the rigid element to resist the pivoting movement. The rigid element may be arranged between, e.g. sandwiched between two of said damping elements. For example, two opposing surfaces of the rigid element may each contact one of the two damping elements. Each of the damping elements may be sandwiched between the rigid element and a corresponding static and/or rigid plate, e.g. two static plates arranged on opposing sides of the rigid element. The damping element(s) may be a sacrificial element. For example the sacrificial element may gradually wear away over repeated operation of the helicopter. The damping elements may induce a frictional force on the rigid element e.g. acting against its pivoting movement. The damping elements may comprise rough surfaces for inducing the frictional force. The rotor head may comprise a biasing means for biasing/urging the damping element(s) against the rigid element. The damping elements may be in the form of a friction washer. The pivotable connection may be provided by a pin or bolt which extends into the blade grip and into at least one of: the rigid element and the rotor blade. The rigid element may comprise a hole for receiving said pin or bolt. Each of the damping elements and/or plates may comprise a hole for receiving said pin or bolt. The damping arrangement may further comprise a slot an