MAIN ROTOR CONTROLS SYSTEM – GENERAL
The main rotor controls system includes
• the collective control
• the cyclic control
The two controls are mixed, before to be sent to the main rotor servo
actuators, to obtain the desired attitude and altitude.
COLLECTIVE CONTROL – GENERAL
The collective control is a conventional metallic rod and bellcrank type. The
control is composed of a lever for pilot and copilot that make a common
input to a mixing unit. The collective control sticks are made of aluminium
with a control grip at the top. The levers are connected together by a torque
tube.
An adjustable friction is installed at the right end of the Collective torsion
tube: it used to increase the collective control mechanical resistance; such
resistance can be as high as to hold the stick during manual flight.
Two Linear Variable Differential Transformer (LVDT) are installed at the left
end of the Collective torsion tube: they provide position of the Collective
lever to the engines for power change anticipation.
From the control tube a rod extends vertically to the roof and them, through
another torsion tube inputs, to the mixing unit.
COLLECTIVE TRIM ACTUATOR
A collective trim actuator is installed in parallel with the torque tube. It has
the same control travel authority as the pilot but with a low-limited rate of
control for safety in case of a malfunction occurs. The trim actuator can be
overridden by pilot commands via a spring-clutch.
COLLECTIVE CONTROL – PRINCIPLE OF OPERATION
The pilot and copilot collective levers are connected together to give a
common input to the mixing unit.
The mixing unit, in turn, gives a common output towards the three hydraulic
main rotor servo actuators which change the pitch angle of the main rotor
blades to obtain the desiderated change of attitude and altitude.
An electrical trim actuator connected to pilot and copilot collective provides
an automatic input towards the AFCS.