Pitch Controls

Pitch control link assemblies

Pitch control links are used to connect the swashplate with the blade in order for the pilot to command pitch input into the blade. Many different linkage or mechanism styles are used to make this connection, but a typical configuration is shown herewith.

Typical solutions

SKF manufactures two different types of pitch control links utilising either its self-lubricating technology or its laminated elastomeric technology. SKF can supply just the rod end or the entire link assembly.

The self-lubricating spherical plain bearing solutions would typically incorporate the SKF Extended Life technology (XL/XLHP/XLNT):
  • Spherical plain bearing
  • Rod end bearing assembly
  • Turnbuckle assembly (incorporating rod end assemblies)
SKF also offers laminated elastomeric technology for use in main rotor pitch control links.

Specific considerations

The design considerations for the self-lubricating spherical plain bearings are similar to the laminated elastomeric rod ends when it comes to envelope, loads and motions. Laminated elastomeric devices would also require knowledge of the desired spring rates.Size constraints or functionality will greatly dictate the bearing selection (elastomeric versus lined bearing). Information on the specific operating conditions is required to help determine the bearing size and technology choice.

Typical market constraints and customer preferences

The self-lubricating technology is more widely used as it is less expensive, more compact and consequently lighter. However, in certain highly demanding applications, laminated elastomeric rod ends are preferred in terms of durability. In general, the laminated elastomeric solution is more widely used on tail rotor pitch control links. Helicopter OEM’s have personal preferences for these technologies with significant deviations evident across the industry.
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