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Question 820077

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  • Question 820077

    During balanced level flight, the pitch angle of the main rotor blade:

    I believe the answer is: Remains constant on both sides
    Decreases on the advancing side, increases on the retreating side

    Because due to flap up on the advancing side and flap down on the retreating side, the angle of attack changes not the pitch and so giving equality of lift??

  • #2
    Re: Question 820077

    Hi Guy,
    The question could be slightly ambiguous, but I assume the examiner is thinking about a helicopter in forward flight. This needs a rotor disc that is tilted forward. Equal lift over the whole disc is not what we want, because that would keep the disc horizontal.
    To lower the disc in front of us, we must make the advancing blades flap down and, to raise the disc behind us, the retreating blades must flap up. We make this happen by varying the pitch angle throughout each rotation, or cycle.
    That is why the control we use to vary the disc angle is called the Cyclic. The pitch angle will reduce for half the cycle, and increase for the other half.
    The exact situation is confused by phase lag, but that is another story.

    Ben W (BGS Instructor)