Helicopter Lift-off Mechanism: Understanding Collective Pitch Control

Which of the following statements are correct?

A) When the cyclic pitch control lever is raised, the blade angle of all the rotor blades increases uniformly and they create the lift that allows the helicopter to take off vertically.

B) When the collective pitch control lever is raised, the blade angle of all the rotor blades increases uniformly and they create the lift that allows the helicopter to take off vertically.

C) When the collective pitch control lever is raised, the blade angle of the aft rotor blades decreases uniformly and they create the lift that allows the helicopter to take off vertically.

Answer:

Statement B is correct. The collective pitch control lever when raised increases the blade angle of all rotor blades uniformly, creating lift, allowing the helicopter to take off vertically.

The statement that is correct is statement B) When the collective pitch control lever is raised, the blade angle of all the rotor blades increases uniformly and they create the lift that allows the helicopter to take off vertically. The collective pitch control refers to the control of the angle of all the rotor blades simultaneously.

Raising the collective pitch control lever leads to an increase in angle of attack of all the blades uniformly, thus creating more lift, allowing the helicopter to take off vertically.

Statement A) is incorrect because the cyclic pitch control lever changes the blade angle cyclically, not uniformly.

Statement C) is also incorrect as raising the collective pitch control lever does not decrease the blade angle of the aft rotor blades uniformly.