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30 Cards in this Set
- Front
- Back
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What is the major difference between a fixed wing aircraft's airfoil from a rotary wing airfoil?
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The fixed wing airfoil is unsymmetrical, the rotary wing airfoil is symmetrical.
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What theories explain rotor lift?
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Newton's law of momentum:
Lift results from accelerating amass of air downward (lift only). Blade Element Theory: Airflow over an airfoil section of the rotor blade acts the same as it does on a fixed wing aircraft (lift & drag). |
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What causes lift to change?
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Incrasing the angle of attack (pitch) of the rotor blades.
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What is blade flapping?
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The ability for rotor blades to move vertically to compensate for dissymmetry of lift.
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What component offsets the vibrations caused by blade flapping?
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A drag hinge, allowing the blade to move back and forth in a horizontal plane.
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What is gyroscopic precession?
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The 90 degree offset in cyclic pitch change.
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What is ground effect?
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The cushion of air produced downward from the main rotor when close to the surface.
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What is transitional lift?
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The transition from hover to forward flight, where the helicopter moves from the cushion of air & lift briefly less abundant.
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What is autorotation?
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It occurs when the main rotor rotates by air passing up through the rotor instead of by the engine.
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What is power settling?
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An occurance at low-speed flight in which the helicopter experiences uncontrollable loss in altitude. Caused by downwash from the rotor recirculating at high velocity.
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Three basic flight control systems of rotary wing aircraft.
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Cyclic & collective pitch and the rotary rudder control.
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What controls forward, aft and lateral movements of the helicopter?
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Cyclic pitch.
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Movement of the pilots cyclic stick transmit through control rods nd bell cranks to what components?
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Auxiliary servo cylinders, the mixing unit, and three primary servo cylinders.
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What do the primary servo cylinders control?
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Movement of the rotary-wing blades.
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What vertically controls movement of the helicopter?
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Collective pitch.
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Movement of the collective pitch stick is sent through control rods and bell cranks to what components?
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Auxiliary servo cylinders, mixing unit, primary servo cylinders, and the rotary wing swashplate.
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T or F: Collective pitch control increases/decreases the pitch of the rotar blades simultaneously?
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True
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What component balances the weight of the collective stick?
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Balancing spring attached to the control rods.
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What system controls the pitch of the rotary rudder blades?
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The rotary rudder control system.
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What component prevents sudden movements of the rudder control pedals?
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Hydraulic pedal damper located in the auxiliary servo cylinder bank.
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What does the negative force gradient spring do?
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It cancels feedback loads exerted by the rotary rudder during flight, and when the hydraulic system is off.
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The negative force gradient spring is preloaded to ______ pounds.
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600.
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What are the four basic components of the helicopter flight control system?
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Auxiliary servo cylinder, mixing unit, primary servo cylinder, and the swashplate.
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How many psi does the auxiliary servo cylinder operate at?
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1500 psi.
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What is the purpose of the mixing unit?
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The unit coordinates and transfers independent movements of the lateral, forward, aft and directional controls. Causes the controls to move the 3 primary servo cylinders simultaneously in the same direction. Cahnges pitch on the rotary rudder blades to compensate for the change in pitch of the rotary-wing blades.
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What is the purpose of the Primary Servo Cylinders?
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To send flight control movements to the stationary swashplate of the rotary-wing head.
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What is the purpose of the Swashplate Assembly?
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To send movement of the flight controls to the rotary-wing blades.
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What allows the swashplate assembly to tilt off its horizontal plane and move on its vertical axis?
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A ball ring socket.
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The assembly consists of a __________ swashplate, connected to the rotary-wing ______ by the rotating _________ and adjustable pitch control ________.
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rotating
hub scissors rods |
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The stationary swashplate connects to the main gearbod by what 2 components?
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Stationary scissors & Primary Servo Cylinders.
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