1. How a helicopter is able to fly
Helicopters
How a helicopter is able to fly
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2. Collective and Cyclic Controls
Flight Controls
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Essence of Flight
Main Rotors
Tail Rotors
Collective and Cyclic Controls
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3. Essence of Flight
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4. Bernoulli's Principle
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In fluid dynamics, Bernoulli's principle states that for an inviscid flow, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy.
wikipedia.org
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5. Bernoulli's Principle
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To sum up Bernoulli’s Principle, an airfoil provides lift due to the air traveling over the top of the surface is traveling at a higher rate of speed than the lower surface due to the shape of the airfoil. Since the air speed is higher on the top there is less air pressure, therefore the lower surface has higher air pressure and forces the airfoil upwards.
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6. Main Rotors
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The lifting force is produced by the rotors. As they spin they cut into the air and produce lift. Each blade produces an equal share of the lifting force. Spinning the rotor against the air causes lift, allowing the helicopter to rise vertically or hover.
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7. Main Rotors
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Main rotor blades are driven thru a transmission/gearbox which is attached to the engine. The blades are controlled thru inputs made by the pilot using the collective, cyclic, and throttle positions.
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8. Main Rotors
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Bell Helicopters
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9. Tail Rotors
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The tail rotor is very important. If you spin a rotor using an engine, the rotor will rotate, but the engine and the helicopter will try to rotate in the opposite direction. This is called TORQUE REACTION. The tail rotor is used like a small propeller, to pull against torque reaction and hold the helicopter straight.
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10. Tail Rotors
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Tail rotors are controlled by foot pedals in the cockpit and are referred to as anti-torque pedals. By depressing associated pedal, the direction of the nose of the aircraft is changed because the pedals change the “pitch” of the tail rotor blades. This is to counteract the effects of the torque produced from the main rotor blades.
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11. Tail Rotors
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Bell Helicopters
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12. Collective/Cyclic Controls
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The collective controls for the main rotor blades are manipulated by a lever that the pilot adjusts to change the “pitch” or angle of attack of the main rotor blades. This lever make changes for all of the main rotor blades at the same time. This change in pitch is what creates left by modifying the position of the blade with reference to the plane of rotation of the blades.
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13. Collective/Cyclic Controls
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Cyclic controls allow the pilot to make adjustments to the rotor head to allow the blades to have rotor blades with independent angles of attack. This control allows the blades to provide different amounts of lift which results in the plane the blades rotate thru change with reference to the aircraft fuselage. This adjustment is what allows the aircraft to move forward/backward or side-to-side.
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14. Collective/Cyclic Controls
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15. Collective/Cyclic Controls
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Bell Helicopters
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16. Hovering
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17. References http://en.wikipedia.org/wiki/Bernoulli%27s_principle
Bell Helicopters Training Brochures and Photos
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