Clevis Assembly With Frangible Shear for Tail Rotor Torque Fail-Safe

The frangible point is pre-positioned at a specific location on the shearing device with predetermined structural characteristics (reduced cross-section, material properties) that ensure it will fail first under excessive torque conditions. This preliminary design ensures that when torque exceeds safe levels, the failure occurs predictably at the frangible point rather than unpredictably elsewhere in the system.

The shearing device with its frangible point acts as a sacrificial component designed to fail deliberately. This disposable element protects more expensive and critical components (input linkages, feedback linkages, main rotor system) by absorbing the failure event. After the frangible point shears, the shearing device can be replaced while preserving the rest of the tail rotor system.

The shearing device with its frangible point serves as an intermediary element positioned between the torque source (tail rotor) and the vulnerable components (input linkages, feedback linkages). Under normal operating conditions, it transmits torque normally. Under excessive torque conditions, it mediates the failure by shearing at the frangible point, preventing the harmful torque from propagating to other components.

The design converts the potentially harmful effect of excessive torque into a beneficial protective mechanism. By deliberately creating a weak point (frangible point) that fails under excessive torque, the system transforms what would be a catastrophic unpredictable failure into a controlled, localized failure that protects the overall system. The harm of component failure is converted into the benefit of system protection.