What is a potential issue with a Semi-Rigid Rotor System?

A Semi-Rigid Rotor System is characterized by the ability of the blades to flap and feather, while being supported on a single teetering hinge. A potential issue associated with this type of rotor system is mass bumping. This phenomenon occurs when the rotor blades experience different amounts of lift, particularly in conditions of turbulence or asymmetrical loading. If one blade experiences more lift than the other, it can cause the rotor hub to tilt, leading the blades to move out of their designed path. The resulting inertia can cause significant oscillations or vibrations, known as mass bumping, which can negatively impact the helicopter's stability and performance.

In this context, while ground resonance primarily affects fully articulated rotor systems, and excessive rigidity and flapping are more commonly associated with other types of rotor systems, mass bumping specifically highlights the challenges faced by semi-rigid systems under certain operational conditions. Understanding this helps pilots recognize the potential for mechanical failure or compromised control when flying helicopters equipped with a Semi-Rigid Rotor System, emphasizing the importance of proper handling and situational awareness.