Helicopter Aerodynamics Mixed Test
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Questions and Answers

Match the following helicopter movements with their corresponding actions:

Yaw = Rotation around the vertical axis Pitch = Rotation around the lateral axis Roll = Rotation around the longitudinal axis Autorotation = State of flight where the main rotor system is being turned by the action of the relative wind passing up through the disc, rather than engine power

Match the following helicopter components with their corresponding functions:

Main rotor disc = Tilts to control the helicopter's pitch attitude Anti-torque system = Controls the yawing movement around the vertical axis Vertical hinge, also called the drag hinge = Accommodates blade acceleration/deceleration Freewheeling unit = Allows the main rotor to continue turning even if the engine is not running

Match the following rotor blade movements with their corresponding effects:

Blade flaps up = Centers of mass move closer to the axis of rotation, causing the blade to accelerate Blade flaps down = Decelerates until it reaches the neutral, or level position Blade flaps up and down = Equalizes lift Retreating blade at high forward speed = Stalls because of a high angle of attack and slow relative wind speed

Which of the following is the correct definition of autorotation?

<p>Autorotation is the state of flight where the main rotor system is being turned by the action of the relative wind passing up through the disc, rather than engine power.</p> Signup and view all the answers

Which axis does a helicopter yaw around?

<p>Vertical axis</p> Signup and view all the answers

What is the primary function of the cyclic pitch control in a helicopter?

<p>To control the pitch movement of the helicopter</p> Signup and view all the answers

True or false: The combination of blade flapping and slow relative wind acting on the retreating blade normally limits the maximum forward speed of a helicopter.

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

True or false: Coriolis effect causes the acceleration or deceleration of the rotor blade as a result of the blade's centre of mass moving closer to or further from the axis of rotation.

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

True or false: Autorotation is the state of flight where the main rotor system is being turned by the action of the relative wind passing up through the disc, rather than engine power.

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

Which of the following statements about blade flapping in a helicopter is true?

<p>Blade flapping increases the angle of attack and associated lift</p> Signup and view all the answers

What is the term for the situation when the retreating blade of a helicopter stalls due to a high angle of attack and slow relative wind speed?

<p>Retreating blade stall</p> Signup and view all the answers

What is the purpose of the vertical hinge, or drag hinge, in a fully articulated rotor system?

<p>To accommodate blade acceleration and deceleration</p> Signup and view all the answers

What is the term for the state of flight where the main rotor system is being turned by the action of the relative wind passing up through the disc, rather than engine power?

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

Which axis does a helicopter pitch around?

<p>Lateral axis</p> Signup and view all the answers

What is the primary function of the cyclic pitch control in a helicopter?

<p>To tilt the main rotor disc forward or backward</p> Signup and view all the answers

What causes the acceleration or deceleration of the rotor blade in a helicopter as a result of the blade's center of mass moving closer to or further from the axis of rotation?

<p>Coriolis effect</p> Signup and view all the answers

True or false: The combination of blade flapping and slow relative wind acting on the retreating blade normally limits the maximum forward speed of a helicopter.

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

True or false: In autorotation, the main rotor blades rotate at a higher speed compared to normal powered flight.

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

What controls the rotation around the vertical axis in a helicopter?

<p>Anti-torque system</p> Signup and view all the answers

True or false: The retreating blade stalls in a helicopter due to a high angle of attack and slow relative wind speed.

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

True or false: The pitch angle of the main rotor blades must be reduced during autorotation by lowering the collective pitch.

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

True or false: The anti-torque system controls the pitching movement of a helicopter around the lateral axis.

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

Which of the following statements about blade flapping in a helicopter is true?

<p>Blade flapping increases the angle of attack and associated lift.</p> Signup and view all the answers

Which of the following best describes the retreating blade stall in a helicopter?

<p>The retreating blade stalls due to a high angle of attack and slow relative wind speed.</p> Signup and view all the answers

Which of the following is the correct definition of autorotation?

<p>Autorotation is the state of flight where the main rotor system is being turned by the action of the relative wind passing up through the disc, rather than engine power.</p> Signup and view all the answers

Which of the following best describes the Coriolis effect in a helicopter?

<p>The Coriolis effect causes the acceleration or deceleration of the rotor blade as a result of the blade's center of mass moving closer to or further from the axis of rotation.</p> Signup and view all the answers

Which of the following best describes the primary function of the cyclic pitch control in a helicopter?

<p>The cyclic pitch control is used to control the pitch attitude of the helicopter by tilting the main rotor disc.</p> Signup and view all the answers

During autorotation, airflow enters the rotor disc from ______ as the helicopter descends.

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

To successfully change the downward flow of air to an upward flow during autorotation, the pitch angle of the main rotor blades must be reduced by lowering the ______.

<p>collective pitch</p> Signup and view all the answers

A helicopter yaws around the ______ axis, pitches around the lateral axis, and rotates around the longitudinal axis.

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

Study Notes

Helicopter Movements and Functions

  • Helicopter yaw occurs around the vertical axis.
  • Pitching movement happens around the lateral axis, while the helicopter rotates around the longitudinal axis.
  • The cyclic pitch control is primarily responsible for changing the helicopter's pitch and roll attitudes.

Autorotation Definition

  • Autorotation is defined as the state of flight where the main rotor system turns due to relative wind passing upwards through the rotor disc, rather than being powered by the engine.

Rotor Blade Movements and Effects

  • Blade flapping, influenced by the combination of airflow and load changes, is essential for maintaining stability and control during flight.
  • The retreating blade stall occurs when the retreating blade experiences a high angle of attack and slow relative wind speed.

Force and Motion Dynamics

  • Coriolis effect causes the acceleration or deceleration of rotor blades based on the blade's center of mass moving towards or away from the axis of rotation.
  • During autorotation, the main rotor blades rotate at a higher speed compared to normal powered flight due to increased relative wind.

Collective and Pitch Control

  • Lowering the collective pitch reduces the pitch angle of the main rotor blades during autorotation, which is crucial for transitioning to an upward airflow.
  • The anti-torque system does not control pitching movement; it primarily manages yaw to counteract torque from the main rotor.

Blade Stall and Performance

  • The combination of blade flapping and a slow relative wind on the retreating blade can limit a helicopter's maximum forward speed.
  • In a fully articulated rotor system, the vertical hinge (drag hinge) allows for controlled flapping and movement of the blades under varying aerodynamic loads.

Summary of Key True/False Statements

  • True: The combination of flapping and slow wind limits forward speed.
  • True: The retreating blade stalls due to high angle of attack and slow wind.
  • False: The anti-torque system controls pitching movements.
  • False: The pitch angle must be reduced during autorotation.
  • False: Retreating blade stall refers to stable conditions.

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Description

Test your knowledge on helicopter rotor systems and their role in generating lift. Learn about the effects of coning and blade bending in a semirigid rotor system, as well as the significance of weight in helicopter operations.

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