SKF solutions for helicopter applications

SKF only uses SKF proprietary silicone rubber to manufacture viscoelastic shock absorbers. These shock absorbers are usually configured in two ways; Create linear dampers (tank construction) or shear dampers (shear pads) based on the rotor system.

Main propeller

The main propeller system has three structures - fully articulated, semi-rigid, and rigid. These describe the relative degrees of freedom between the blades and the rotor hub.

A rigid rotor system is a simple construction in which the blades have effective rigidity relative to the center of rotation. The semi-rigid rotor system has blades that are fixed relative to the "lead/lag", but still allow the blades to "swing". The terms defined below are related to complete articulation.

A fully articulated rotor system allows the blades to have Z-high degrees of freedom relative to the center of rotation. The pitch degree of freedom allows the blade to rotate along its axis. Free 'swinging' allows the blades to move perpendicular to the rotor disk. The degrees of freedom of leading/lagging allow the blades to move within the plane of the turntable during one cycle of rotation.

Lead lag shock absorber

Typical solutions

Typical market restrictions and customer preferences

 The type of technology used for lead lag shock absorbers is a function of rotor system design, as each technology is limited by certain attributes.

For SKF products, the limiting factors are available damping and Z-large stroke (which is a factor in the handling of strain by elastomers, resulting in very large shock absorbers for a certain length of stroke).

Lessons Learned/Z Best Practices

SKF's silicone blend is a top ranked product in the industry in terms of its damping capacity. Therefore, SKF products can provide damping safety margins compared to competitors of the same size, or offer customers smaller and lighter solutions.

Designing shock absorbers requires close consultation with customers, as the dynamic performance and stability of the rotor system are affected by any changes in the static and dynamic stiffness of the shock absorbers.

The qualification review of these products is usually completed by SKF in terms of performance and lifespan, but flight testing is always necessary to demonstrate sufficient aircraft stability under all extreme conditions.