|Flight Direction Control|
( page 1 )
Helicopter, Lift is obtained by means of one or more power driven horizontal propellers which called
Rotors. When the rotors of helicopter turns it produces lift and reaction torque, reaction torque which tends to make helicopter spin. on most
helicopters a small rotor near the tail which called tail rotor compensates for this torque. On twin rotor helicopter the rotors rotate in opposite directions, their reactions
cancel each other. The direction of helicopter is controlled by inclining the axis of the main rotor path in that direction.
|Function of Controls|
There are three major controls in the helicopter that the pilot must use during flight. They are : ( 1 ) Collective pitch control.
( 2 ) Anti Torque Pedals or Tail Rotor Control. ( 3 ) Cyclic Stick Control.
The collective pitch lever or stick is located by the left side of the pilot's seat and is operated with the left hand.
The collective is used to increase main rotor pitch at all points of the rotor blade rotation. It increases or decreases total rotor thrust.
The collective lever is connected to the swash plate by a series of bush pull tubes. Raising the collective lever increases the pitch on the
main rotor blade, lowering the collective lever decreases the main rotor blade pitch. The amount of movement of th elever determines
the amount of blade pitch change. As the angle of attack increase, drag increases and Rotor RPM and Engine RPM
tend to decrease . As the angle of attack decreases, drag decreases and the RPM tend to increase.Since it is essential that the
RPM remain constant, there must be some means of making a proportionate change in power to compensate for the change in drag.
This coordination of power change with blade pitch angle change is controlled through a collective pitch lever- trottle control cam
linkage which automatically increases power when the collective pitch lever is raised and decreases power when the lever is lowered.
The picture above is the typical collective lever but the detail of control may varies depend on each
munufacturer .The main functions are still the same for all helicopters.
Collective Lever is connected to the rotor system via push pull tubes. It also has droop com pensation devics which sense change in
the collective pitch lever and increases or decreases fuel to the engine automatically somewhat in anticipated of a change in power required.
This helps to minimize the RPM fluctuations during collective pitch change.
Engine Control (Emergency) is the throttle twist grip. During emergency condition, between flight and flight idle positions. This is useful during
any event which would cause engine or rotor RPM to go too high or while landing after a tail rotor failure.
Idle Release Button, when the throttle is rolled from " off " to " idle " the idle release button snaps into a detent
which prevents the throttle from being rolled back to " off "
Starter Button : Pushing this button will cause the starter / generator to act as a starter motor ( Starter / Generator is a component that funtion
in either mode as a starter or generator ) , turning over the engine.
Landing Light Switch has a three position which are " off " , " forward " and "both " . In forward , only the
forward light is activated. In both, the forward and downward lights are activated .
Power Trim Switch ,by holding it in " increase " or " decrease " the pilot can set the RPM that the pilot attempt
next : flight control page 2