Which statement best describes the effect of increasing the collective pitch on rotor lift?

Which statement best describes the effect of increasing the collective pitch on rotor lift?

• A. Lift decreases.
• B. Lift remains the same.
• C. Lift increases.
• D. Lift fluctuates unpredictably

Answer: (C)

Increasing the collective pitch changes the angle of attack of all rotor blades at the same time. With a larger pitch, each blade generates more lift per revolution, so the overall rotor thrust climbs. In other words, raising the collective increases the rotor’s lift capacity at a given rotor speed and air density, causing the helicopter to rise or hold a higher altitude under the same weight. In practice, this lift rise comes from the whole rotor disk responding with higher aerodynamic force as blade pitch is increased. If power and rotor speed are managed (as with a governor and proper power available), the aircraft will climb smoothly; if power is limited, the increased demand can affect rotor speed, but the immediate effect of the change in pitch is to boost lift.

Increasing the collective pitch changes the angle of attack of all rotor blades at the same time. With a larger pitch, each blade generates more lift per revolution, so the overall rotor thrust climbs. In other words, raising the collective increases the rotor’s lift capacity at a given rotor speed and air density, causing the helicopter to rise or hold a higher altitude under the same weight. In practice, this lift rise comes from the whole rotor disk responding with higher aerodynamic force as blade pitch is increased. If power and rotor speed are managed (as with a governor and proper power available), the aircraft will climb smoothly; if power is limited, the increased demand can affect rotor speed, but the immediate effect of the change in pitch is to boost lift.