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

2. Parts of a Helicopter Induced Flow Chord Line Rotational Velocity

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

4. 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

5. 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

6. 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).

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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.

16. 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

17. 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.

18. 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

19. 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

20. 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

21. 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

22. 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

23. 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

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