UH-72A rotor system type?

• A. Fully articulated
• B. Semi-rigid
• C. Rigid
• D. Flexible

Answer: (C)

A rigid rotor system is being tested here. In a rigid rotor, there are no hinges at the main rotor hub, so the blades and hub are connected in a stiff way. The rotor loads are absorbed by the blades bending and by aerodynamic forces, rather than by moving hinges that let each blade flap or lag independently. This design gives a smooth, stable feel and reduces the number of moving parts you have to maintain.

The UH-72A Lakota uses this kind of rotor setup, which is described as a rigid (bearingless) rotor system. That’s why the best choice is the rigid option.

Fully articulated rotors have hinges that let each blade flap and lead-lag independently, which is more complex and offers different control characteristics. Semi-rigid rotors rely on a teetering hub that allows mainly one motion (teetering). Flexible isn’t a standard way to classify rotor systems in this context.