Helicopters

1. Helicopters How a helicopter is able to fly Click anywhere to Launch

2. Flight Controls Home Essence of Flight Main Rotors Tail Rotors Collective and Cyclic Controls Next

3. Essence of Flight Home www.google.com Back Next

4. Bernoulli's Principle Home 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 Back Next

5. Bernoulli's Principle Home 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. Back Next

6. Main Rotors Home 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. www.helis.com Back Next

7. Main Rotors Home 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. Back Next

8. Main Rotors Home Bell Helicopters Back Next

9. Tail Rotors Home 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. www.helis.com Back Next

10. Tail Rotors Home 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. Back Next

11. Tail Rotors Home Bell Helicopters Back Next

12. Collective/Cyclic Controls Home 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. Back Next

13. Collective/Cyclic Controls Home 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. Back Next

14. Collective/Cyclic Controls Home Back www.centennialofflight.gov Next

15. Collective/Cyclic Controls Home Bell Helicopters Back Next

16. Hovering Home Back Next

17. References • http://en.wikipedia.org/wiki/Bernoulli%27s_principle • http://www.helis.com/howflies/prflight.php • http://www.google.com/ • Bell Helicopters Training Brochures and Photos • www.centennialofflight.gov Home