Leading Cadet Training Principles of Flight Leading Cadet Training The Helicopter Lecture 8

Parts of a Helicopter Induced Flow Chord Line Rotational Velocity

Parts of a Helicopter Blades Tail Rotor Rotor Disc Rotor Head Rotor Blades Pitch Angle Rotor Head Plane of Rotation Rotor Shaft

How a helicopter produces lift A Rotor Blade has an aerofoil shape similar to an aircrafts wing. The engine rotates and makes the blades move through the air to generate Lift. To make the helicopter lift off the ground the blades have to rotate fast enough and have an angle of attack to the airflow. Chord Line Lift Leading Edge Trailing Edge

How a helicopter produces lift The blades are fitted into the rotor head so that they can be twisted That is, the angle between the chord line and its plane of rotation (‘pitch angle’) can be varied, which alters the angle of attack and allows the pilot to vary the amount of lift. Plane of Rotation Chord Line Angle of Attack  Lift

The helicopter has 4 Main Controls. Helicopter Controls The helicopter has 4 Main Controls. 1. The Hand Throttle. The Collective Pitch Lever. 3. The Cyclic Pitch Control. The Tail Rotor Control (Yaw Pedals).

Helicopter Controls 1. THE HAND THROTTLE Is a twist-grip on the end of the collective lever. The pilot controls the collective pitch and the throttle twist-grip control at the same time. The Hand Throttle

2. COLLECTIVE PITCH CONTROL Helicopter Controls 2. COLLECTIVE PITCH CONTROL Normally on the left. It controls VERTICAL movement by changing the pitch angle of all the rotor blades by the same amount at the same time. Collective Pitch Control

How a helicopter produces lift Decrease the AoA of the helicopter blades, and the helicopter descends When the pitch angle of each blade and the angles of attack of all the rotor blades are altered by the same amount and at the same time, it is known as a Collective Alteration of Pitch, or Collective Pitch. Increase the AoA of the helicopter blades, and the helicopter ascends Lift Lift α Relative Airflow Angle of Attack

3. THE CYCLIC PITCH CONTROL Helicopter Controls 3. THE CYCLIC PITCH CONTROL Is similar to an aircrafts control column and is normally operated by the pilots right hand. The cyclic pitch moves the helicopter horizontally by tilting the rotational disc of the main rotor. Cyclic Pitch Control

Horizontal Flight Each blade is hinged and can be made to rise and fall as it goes around the plane of rotation. To make the helicopter go forwards, each blade rises at the rear of the rotation disc, and descends as it reaches the front. So the disc is tilted forwards and there is horizontal thrust available. Hinge Blades Thrust

Horizontal Flight To make the helicopter go BACKWARDS, each blade is made to descend as it reaches the rear of the rotation disc, and to rise as it reaches the front. So the disc is tilted backwards and the horizontal thrust is reversed. Thrust

Horizontal Flight The helicopter could also move sideways by the same principle. Obviously, for the rotor disc to stay tilted in the required direction, the pitch of each blade must vary through 360° cycle. Thrust

Helicopter Controls 4. TAIL ROTOR CONTROL The pilot’s feet control the Tail Rotor. If the left pedal is pushed forwards, then the nose of the helicopter yaws to the left. If the right pedal is pushed forwards, then the nose of the helicopter yaws to the right. Tail Rotor Controls Rudder Pedals Rudder Pedals L R L R

Torque Reaction When the engine drives the rotor in its circular motion there is an Opposing Force – the Torque Reaction. The torque reaction tries to spin the fuselage the opposite way to the rotor blades.

Torque Reaction To prevent this on a single rotor helicopter a small rotor with a vertical rotational disc is fitted to the tail of the helicopter. Its horizontal thrust force opposes the fuselage torque reaction and permits balanced flight. Airflow Balancing Force

Torque Reaction Moving the Yaw Pedals will alter Blade Pitch equally on all the Tail Rotor Blades. and can also be used to turn (yaw) the helicopter around the Main Rotor.

Check of Understanding How does a helicopter generate lift? By spinning the main rotor faster By spinning the main rotor slower By increasing the angle of attack By decreasing the angle of attack

Check of Understanding What are the 3 controls a Helicopter uses to control the aircraft’s attitude? Collective, Cyclic, Yaw Pedals Ailerons, Elevators, Rudder Cyclic, Rudder, Yaw Pedals Collective, Cyclic, Thrust

Check of Understanding When a Helicopter rotor is driven in a circular motion there is an opposing force, what is this force called? Lift Reaction Torque Reaction Drag Reaction Cyclic Pitch Reaction

Check of Understanding When a helicopter pilot makes a large upwards movement of the collective lever, more power is required. How is this extra power obtained? An automatic cam arrangement opens the engine throttle The cyclic pitch is altered taking the load off the tail rotor The pilot turns the hand throttle to open it The yaw pedals are operated to increase the load on the engine

Check of Understanding How is horizontal flight achieved in a helicopter? Inclining the tail rotor Increasing the tail rotor speed Increasing the rotor speed Tilting the rotor disc

Check of Understanding The pitch angle of a helicopters rotor blades can be altered individually, as each blade traverses the plane of rotation. What is this called? Collective Pitch Pitching Cyclic Pitch Torque Reaction

Leading Cadet Training Principles of Flight Leading Cadet Training End of Presentation