Helicopter Aerodynamics

Which force opposes lift in a helicopter?

What is the purpose of the antitorque rotor in a helicopter?

What is the function of the swash plate assembly in a helicopter?

How does a rigid rotor system absorb operating loads?

Which force opposes helicopter movement?

What is the major cause of drag at reduced airspeeds?

What is the relationship between thrust and torque in a helicopter?

What is the purpose of the tail rotor in a helicopter?

Which axis does a helicopter yaw around?

What is the purpose of the anti-torque system in a helicopter?

What is autorotation in a helicopter?

What causes the retreating blade stall in a helicopter?

Which one of the following statements about the span of a rotor blade is correct?

What does twisting a rotor blade cause?

What is the pitch angle?

What is the angle of attack?

Which of the following is true about ground effect in helicopter flight?

What is the maximum forward speed of a helicopter limited by?

What is the term for the difference in lift between the advancing and retreating blades of a helicopter rotor system?

What is the term for the oscillating tendency of a helicopter's main body when supported by the main rotor system at a single point?

Which component of a helicopter is typically considered its central component?

Which type of main rotor system allows the blades to move up and down, back and forth, and around the spanwise axis?

What is the movement called when the blades of a fully articulated rotor system rotate independently around the vertical hinge?

What type of rotor system uses two blades rigidly attached to the main rotor hub and allows the blades to flap together?

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

What is the pitch angle of a rotor blade?

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

What is the angle of attack of a rotor blade?

Which of the following is NOT a type of anti-torque system used in helicopters?

How is hovering at a constant altitude achieved in a helicopter?

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

What is disc loading in the context of helicopters?

Movement about the ______ axis is referred to as yaw.

In forward flight, moving the cyclic towards the left or right, as desired, tilts the rotor disc ______ and rolls the helicopter about the longitudinal axis.

What is autorotation in the context of helicopters?

What is the function of the swash plate assembly in a helicopter?

Which force opposes lift in a helicopter?

What is the purpose of the antitorque system in a helicopter?

Which of the following is a characteristic of a fully articulated rotor system in a helicopter?

What is the purpose of dampers in a fully articulated rotor system?

Which of the following is a characteristic of a semirigid rotor system in a helicopter?

Which one of the following statements about the solidity ratio is correct?

What is the purpose of the tip-path plane in a helicopter?

What is the relationship between the angle of attack and lift in a helicopter?

Which force opposes helicopter movement?

During hovering flight, the variable forces are directed to make the helicopter preform as needed. While hovering, the amount of main rotor thrust is changed to maintain the desired hover altitude. This is done by changing the angle of attack of the main rotor blades and by varying power, as needed. In this case, thrust acts in the same vertical direction as lift. To maintain a hover at a constant altitude, enough lift and thrust must be generated to equal the weight of the helicopter and the drag produced by the rotor blades. The weight that must be supported is the total weight of the helicopter and its occupants. If the amount of thrust is greater than the actual weight, the helicopter gains altitude; if thrust is less than weight; the helicopter loses altitude. The drag of a hovering helicopter is mainly induced drag incurred while the blades are producing lift. There is, however, some parasite drag on the blades as they rotate through the air. Throughout the rest of this discussion, the term “drag” will include both induced and parasite drag.

The amount of thrust produced by the tail rotor is varied in relation to the amount of torque produced by the engine. As the engine supplies more power, the tail rotor must produce more thrust. The tail rotor is designed to produce thrust in a direction opposite torque. The thrust produced by the tail rotor is sufficient to move the helicopter laterally. This is normally counteracted in the design of the helicopter by slightly tilting the rotor mast in the opposite direction of tail rotor thrust.

Which of the following is true about ground effect in helicopter flight?

What causes the retreating blade stall in a helicopter?

What is translational lift in helicopter flight?

Which of the following is true about the Coriolis effect in helicopter rotor blades?

What is the purpose of a freewheeling unit in a helicopter?

What causes the nose of a helicopter to pitch down in forward flight?

What is the function of the antitorque system in a helicopter?

True or false: The cyclic pitch control in a helicopter is primarily responsible for controlling the pitch attitude of the helicopter.

What is the purpose of the swash plate assembly in a helicopter?

True or false: The retreating blade stall in a helicopter is caused by a high angle of attack and slow relative wind speed.

True or false: The combined upward flapping of the advancing blade and downward flapping of the retreating blade equalizes lift in a helicopter.

True or false: A freewheeling unit in a helicopter allows the main rotor to continue turning even if the engine is not running.

True or false: The Coriolis effect causes the acceleration or deceleration of the rotor blade in a helicopter.