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Fundamentals of Helicopter

Fundamentals of Helicopter. Outlines. Helicopter and Fixed-Wing Aircrafts Principles of Rotary Flight Rotor’s Configuration Flying the Helicopter Hover and Vertical motion Performance (Power Estimation). Helicopter and Fixed-Wing Aircrafts.

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Fundamentals of Helicopter

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  1. Fundamentals of Helicopter Outlines • Helicopter and Fixed-Wing Aircrafts • Principles of Rotary Flight • Rotor’s Configuration • Flying the Helicopter • Hover and Vertical motion Performance (Power Estimation)

  2. Helicopter and Fixed-Wing Aircrafts • Helicopters are the most versatile flying machines in existence today. • The amazing flexibility of helicopters means that they can fly almost anywhere (mountains, Foresests,Ships,…) • A helicopter can do three things that an airplane cannot Directions of motion of an airplane • A helicopter can fly backwards. • The entire aircraft can rotate in the air. • A helicopter can hover motionless in the air (No Forward Speed). Directions of motion of a Helicopter

  3. Helicopter Capabilities Hover and Rotate Fly backwards Pirouette (rotates 360 degrees while it travels down a straight line relative to the ground) stop in mid-air

  4. Principles of Rotary Flight The Main Rotor Thrust • 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. weight • The produced lift allows the helicopter to rise vertically or hover • Tilting the spinning rotor will cause flight in the direction of the tilt

  5. Principles of Rotary Flight • 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 ( TORQUE REACTION) • Several methods are developed to counter the reaction torque to hold the helicopter straight • One of the classical solution is using a small rotor at the end of a long boom (Tail-Rotor Configuration) to push the fuselage in the opposite direction of the torque force. Tail-Rotor Configuration

  6. Rotor 's Configuration Tandem • Because of the opposite rotation of the rotors, the torque of each single rotor will be neutralized. • It is able to lift heavy loads whose position relative to the helicopter’s center of gravity is less critical than the single rotor configuration • Used with big helicopters. • The construction of the control system is much more complicated, compared to a helicopter with a tail rotor. Side by Side • Allow a wide variation of CG position • This design was used for the biggest helicopter built but it was never very successful. • Extra drag is created caused by the supporting pylons

  7. Rotor 's Configuration Coaxial Rotor • This configuration is compact which explains why it is often seen on board ships • The control along the vertical axe occurs as a result of different lifts of the two rotor discs. • Depending on which rotor produces more lift, the helicopter will turn to the left or right. • For these helicopters it is not possible to reach a high cruising speed, because the drag is too large.

  8. Rotor 's Configuration No-Tail-Rotor (NOTAR) Helicopter • Jet thrust is used rather than blades to • Provide directional stability • Reduce noise, providing the world’s quiets helicopter • Counter the main rotor torque

  9. Flying the Helicopter Cyclic Control Stick • Moving it forward or back will point the nose of the helicopter up or down. It does this by varying the angle of the rotor blades as they go round, tilting the rotor back and forth. • When moved left or right the rotor tilts in that direction and the helicopter banks and rolls.

  10. Flying the Helicopter Rudder • The tail rotor pedals, on the floor, are used to control the angle of the tail-rotor. • For straight flight, the angle of the tail rotor is set to prevent the helicopter from turning to the right as the main rotor turns to the left. • The pilot pushes the left pedal to increase the angle of the tail rotor and turn to the left. • Pushing the right pedal decreases the angle of the tail rotor and turns the helicopter to the right. The blades of the tail rotor are only about 2 feet (61 cm) long

  11. References • http://travel.howstuffworks.com/helicopter.htm • http://www.ae.gatech.edu/~lsankar/AE6070.Spring2004/ • Helicopter History site, http://www.helis.com/ • Wyne Johnson, “Helicopter Theory”, Dover Pub., 1994 • Simon Newman, “The Foundations of Helicopter Flight”, John Wiley & Sons , 1994

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