What is the name of the angle between the chord line of the rotor blade and the reference plane of the main rotor hub or rotor plane of rotation?

• A. Pitch Angle
• B. Bank Angle
• C. Attitude
• D. Angle of Attack

Answer: (A)

Pitch angle is the angle the rotor blade’s chord line makes with the plane of rotation, or the rotor disk. This angle is what you change with the collective to control how much lift each blade produces. A larger pitch angle increases the blade’s angle relative to the rotor plane, raising lift; a smaller pitch angle reduces lift. Bank and attitude describe the helicopter’s orientation in space, not the blade’s geometry, so they aren’t what this angle refers to. Angle of attack is the angle between the blade’s chord line and the oncoming air (relative wind); while blade pitch affects this, they are different angles—the pitch angle is specifically referenced to the rotor plane, not the wind.