What is a primary function of the freewheeling unit in a helicopter?

The primary function of the freewheeling unit in a helicopter is to automatically disengage the rotor from the engine in the event of a failure. This feature is crucial for safety, as it allows the rotor blades to continue spinning freely, which can help maintain lift and control of the helicopter in situations where the engine has lost power. By decoupling the rotor from the engine, the freewheeling unit helps prevent a sudden loss of rotor speed that could lead to a loss of control or an uncontrollable descent. The ability to continue to glide and control descent is vital for the pilot to execute emergency landing procedures safely.

In contrast, increasing engine power during flight, engaging the rotor with the engine during ascent, or regulating rotor speed during landing are functions typically handled by different components of the helicopter’s systems and are not the primary roles of the freewheeling unit.