What is the function of rotor blades in a helicopter rotor system?

• A. Stationary blades that convert velocity into pressure
• B. They reduce engine power requirements
• C. Rotating blades that add velocity
• D. They provide lift by changing blade pitch

Answer: (C)

Rotor blades are the rotating airfoils that push air as the rotor turns. As they sweep through the air, each blade accelerates air downward, increasing its velocity. That momentum imparted to the air creates an upward reaction on the blades, which is the lift that supports the helicopter’s weight. The amount of lift is then controlled by changing the blade pitch, which adjusts how much air is accelerated for a given rotation. This is why rotating blades that add velocity to the air is the best description of their function. The other ideas don’t capture the fundamental action: stationary blades can’t generate lift, reducing engine power isn’t the blade’s job, and although pitch changes control lift, the core function is the rotation and acceleration of air.