Helicopter General Aero Dynamics
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Questions and Answers

Which force opposes lift and is caused by the downward pull of gravity?

  • Weight (correct)
  • Drag
  • Lift
  • Thrust

    • What is the force that propels the helicopter through the air?

  • Lift
  • Thrust (correct)
  • Weight
  • Drag

    • What is drag?

  • The force that propels the helicopter through the air.
  • The force that opposes lift and is caused by the downward pull of gravity.
  • The retarding force created by development of lift and the movement of an object through the air. (correct)
  • The upward force created by the effect of airflow as it passes around an airfoil.

    • Which component of lift is responsible for induced drag?

    <p>The rearward inclination of the lift</p> Signup and view all the answers

    What happens to induced drag as airspeed increases?

    <p>It decreases</p> Signup and view all the answers

    What causes the formation of stronger vortices and an increase in induced drag?

    <p>An increase in angle of attack</p> Signup and view all the answers

    Which of the following is NOT a type of drag in a helicopter?

    <p>Thrust drag</p> Signup and view all the answers

    What is the load factor of a helicopter in steady-state flight?

    <p>1</p> Signup and view all the answers

    What is the solidity ratio of a rotor system?

    <p>The ratio of rotor blade area to rotor disc area</p> Signup and view all the answers

    What is the main factor that determines the majority of lift in a helicopter?

    <p>Decreased pressure above the rotor blade</p> Signup and view all the answers

    Which one of the following is true about the center of pressure on an airfoil?

    <p>The center of pressure is the point where the resultant of all aerodynamic forces are considered to be concentrated.</p> Signup and view all the answers

    What is the purpose of bending the trailing edge of an asymmetrical rotor blade?

    <p>To increase the stability of the rotor disc.</p> Signup and view all the answers

    What is the span of an airfoil?

    <p>The distance from the rotor hub to the blade tip.</p> Signup and view all the answers

    What is the chord line of an airfoil?

    <p>An imaginary straight line drawn from the leading to the trailing edge of the airfoil.</p> Signup and view all the answers

    Which of the following statements is true about the angle of attack?

    <p>Increasing the angle of attack beyond the critical angle of attack produces a decrease in lift.</p> Signup and view all the answers

    What is the Magnus Effect?

    <p>A lifting force produced when a rotating cylinder produces a pressure differential.</p> Signup and view all the answers

    What is Bernoulli's Principle?

    <p>The principle that air flowing over the top surface of an airfoil accelerates and creates a decrease in pressure.</p> Signup and view all the answers

    What is the relationship between the angle of attack and the production of lift?

    <p>Increasing the angle of attack increases the production of lift.</p> Signup and view all the answers

    Due to the downward deflection of the airstream near the rotor blade, the blade operates in an average relative wind that is inclined ______ and rearward near the blade.

    <p>downward</p> Signup and view all the answers

    The lift produced by the blade is perpendicular to the relative wind, therefore the lift is inclined ______ by the same amount.

    <p>aft</p> Signup and view all the answers

    The component of lift that is acting in a rearward direction is ______ drag.

    <p>induced</p> Signup and view all the answers

    As the air pressure differential increases with an increase in angle of attack, stronger vortices form, and ______ drag increases.

    <p>induced</p> Signup and view all the answers

    Induced drag is the major cause of drag at ______ airspeeds.

    <p>lower</p> Signup and view all the answers

    True or false: The downward deflection of the airstream near the rotor blade causes the blade to operate in an average relative wind that is inclined downward and rearward near the blade.

    <p>True</p> Signup and view all the answers

    True or false: As the air pressure differential increases with an increase in angle of attack, stronger vortices form, and induced drag decreases.

    <p>False</p> Signup and view all the answers

    True or false: Induced drag is the major cause of drag at higher airspeeds.

    <p>False</p> Signup and view all the answers

    Study Notes

    Forces in Helicopter Flight

    • Weight is the force opposing lift, caused by gravitational pull.
    • Thrust is the force that propels the helicopter through the air.

    Types of Drag

    • Drag is the aerodynamic resistance encountered by an object moving through air.
    • Induced Drag results from the lift force, specifically linked to the component of lift that generates this drag.
    • Induced drag increases with stronger air vortices created during flight.

    Airspeed and Drag

    • As airspeed increases, induced drag decreases.
    • Stronger vortices and increased induced drag occur at higher angles of attack.

    Helicopter Specifications

    • Load Factor in steady-state flight refers to the amount of lift compared to weight, typically around 1:1 during normal flight conditions.
    • Solidity Ratio describes the ratio of the total rotor blade area to the total rotor disk area.
    • Lift in helicopters is primarily determined by the rotor blades' angle of attack and design.

    Airfoil Characteristics

    • The center of pressure on an airfoil is the point where lift can be considered to act; it shifts with changes in the angle of attack.
    • Bending the trailing edge of an asymmetrical rotor blade helps optimize lift and control characteristics.
    • The span of an airfoil is its length from tip to tip, while the chord line is the straight line connecting the leading edge to the trailing edge of the airfoil.

    Aerodynamic Principles

    • The angle of attack significantly impacts lift production; it represents the angle between the airfoil’s chord line and the oncoming airflow.
    • The Magnus Effect describes the phenomenon where a rotating body in a fluid experiences a lift force perpendicular to the direction of motion and rotation.
    • Bernoulli's Principle explains that an increase in the speed of a fluid occurs simultaneously with a decrease in pressure.

    Summary of Lift and Drag Components

    • The downward deflection of the airstream results in the rotor blade operating at an average relative wind inclined downward and rearward.
    • Lift is produced perpendicular to the relative wind, thus also inclined similarly.
    • The rearward acting component of lift contributes to induced drag.
    • Increased air pressure differential with higher angle of attack causes larger vortices, thus elevating induced drag.

    True or False Statements

    • True: The downward deflection of the airstream aligns the blade's operation angle downward and rearward.
    • False: An increase in angle of attack results in increased induced drag, not a decrease.
    • False: Induced drag is less significant at higher airspeeds, being more dominant at lower speeds.

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    Description

    Test your knowledge on the effects of increasing the angle of attack on lift and stalling with this quiz. Learn about the critical angle of attack and how it determines lift production. Explore the progression of the separation point on an airfoil as the angle of attack is increased.

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