proficiency - AVS

Parts

Fuselage

The fuselage generally contains the cockpit and cabin, guns, fuel tanks, transmission gearbox and engine/s, landing gear or skids. There may be a cargo hook for carrying external loads.

Tailboom

The tailboom is similar in construction to the fuselage, and incorporates a fin structure at the rear.

Landing Gear

Helicopter landing gear consists of either:

• Wheeled Undercarriage

• Fixed skids

There are two types of rotors on a conventional helicopter. These are:

• Main Rotor

• Tail Rotor

Main Rotor

The function of engine driven horizontal rotors is to provide both the lift and the propelling force.

Tail Rotor

A helicopter with a single driven rotor requires some device to prevent the rest of the aircraft from rotating in the opposite direction to its rotor – The tail rotor counteracts the torque produced by the main rotor.

The engine transmits its power to the Main Gearbox and from there drive is transmitted to both the main and tail rotors.

Helicopter controls

There are three main flight controls required to be able to fly a helicopter. These are:

• Collective Pitch

• Cyclic Control

• Tail Rotor Control

Collective Pitch is the application of pitch to all blades equally and simultaneously.

The functions of the collective control system are:

• Primary altitude control

• Primary power control

The Twist grip provides primary power control.

The Collective pitch lever is located on the left hand side of the Pilots seat and moves up and down.

Cyclic Control is the application of pitch to the blades individually during a 3600 cycle.

It controls the direction and velocity of horizontal flight

The Swashplate is the component in the cyclic system that converts linear motion into rotary linear motion.

The Pitch angle of each blade changes constantly during each revolution and this enables the rotor disk to remain tilted in the desired direction.

The primary function of the Tail Rotor is to:

• Counteract the torque of the Main Rotor

Secondary functions of the Tail Rotor are to:

• Balance transmission friction during autorotation

• Alter fuselage heading

Offset Fin

An offset fin is fitted to most helicopters and assists in counteracting main rotor torque when the helicopter is in forward flight. The fin is shaped like an aerofoil, but mounted vertically and therefore produces a sideways thrust when there is sufficient airflow over it

NOTAR (No Tail Rotor)

NOTAR uses a variable pitch fan mounted in the tailboom to provide air for the production of the Coanda effect (this turns the tailboom into an aerofoil) and for the adjustable nozzle at the end of the tailboom to counteract the main rotor torque.

Its major advantage is that it is a lot safer for people working around the helicopter, as there are no tail rotor blades.

Fenestron Tail Rotor

The Fenestron Tail Rotor works the same as a normal tail rotor, but it is made up of a multiple bladed fan mounted within the vertical fin on the tailboom. Again its major advantage is safety.

Contra Rotating Rotors

Contra rotating rotors do away with the need for a tail rotor altogether as having each rotor rotating in opposite directions cancels out the torque effect.

Autorotation

Autorotation is the process of producing lift with the rotor blades as they rotate freely as a result of the airflow passing up through the rotor.

This is the opposite to normal flight when the airflow is induced downwards through the rotors as a result of the rotors being driven by the engine.

Autorotation is the means by which a helicopter may land safely after experiencing an engine failure.