CYCLIC PITCH CONTROL SYSTEM
operation, the collective pitch operation controls
through the auxiliary servo cylinder.
The cyclic pitch control system provides the means
of controlling the forward, aft, and lateral movements
ROTARY RUDDER CONTROL SYSTEM
of the helicopter. Movement of the pilot's or copilot's
The rotary rudder control system controls the pitch
cyclic stick transmits through control rods and bell
cranks. This movement is sent to the auxiliary servo
of the rotary rudder blades. The blades control the
cylinders, the mixing unit, and three primary servo
heading of the helicopter. The pedals control the
cylinders. These primary servo cylinders control
system through a series of control rods and bell cranks.
movement of the rotary-wing blades.
These units connect to the directional bank of the
auxiliary servo cylinder and the mixing unit. See
The cyclic system has a stick trim system that
figure 17-6. At the mixing unit, a control rod operates
hydraulically operates the controls for automatic
the forward quadrant. This quadrant connects by cable
flight. During automatic flight, trim movements are
to the aft quadrant. A control rod from the rear
controlled manually by the cyclic stick grip switch.
The switch is overridden for major control changes by
quadrant connects to the control rods, bell crank, and
stick movement.
pitch control shaft. These parts are found in the rotary
rudder tail gearbox. A hydraulic pedal damper is
Moving the cyclic stick forward extends the aft
l o c a t e d i n t h e a u x i l i a r y s e r vo cy l i n d e r b a n k
primary servo cylinder and retracts the forward
(directional). Its purpose is to prevent sudden
primary servo cylinder. Aft movement of the cyclic
movements of the control pedals. The damper prevents
stick extends the forward primary servo cylinder and
rapid changes in blade pitch, which might cause
retracts the aft primary servo cylinder. In both cases,
the helicopter will advance in the direction of stick
damage to the helicopter. As on conventional aircraft,
movement. Movement of the stick laterally will move
the rudder pedals are adjustable for different leg
the helicopter right or left, corresponding with stick
lengths. The rotary rudder system operates by manual
movement. This movement occurs by retracting and
input or automatically by input from the ASE.
extending the left and right lateral primary servo
The negative force gradient spring cancels
cylinders.
feedback loads exerted by the rotary rudder during
flight. It also cancels feedback loads when the
COLLECTIVE PITCH CONTROL SYSTEM
auxiliary hydraulic system is off. When the rotary
The collective pitch control system provides
rudder is stationary, an initial force is required to move
vertical control of the helicopter. Movement of the
either pedal from its extreme position. With the
collective pitch control stick is sent through control
auxiliary hydraulic system on, the effect of the
rods and bell cranks to the appropriate auxiliary servo
negative force gradient spring is zero.
cylinder. Movement is sent from the servo cylinder to
the mixing unit. At the mixing unit, all vertical
movements of the collective sticks are sent to the
WARNING
p r i m a r y s e r vo cy l i n d e r s a n d t h e r o t a r y - w i n g
swashplate. At this point, the pitch of all blades
The negative force gradient spring is preloaded
increases or decreases equally and simultaneously. A
to 600 pounds. To prevent injury to personnel or
balancing spring attaches to the control rods to help
damage to flight controls, carefully follow the
balance the weight of the collective stick. A friction
maintenance instructions provided in the MIM.
lock on the pilot's collective stick applies the desired
amount of friction to the tube of the collective stick.
The lock prevents creeping during flight. It also
FLIGHT CONTROL SYSTEMS
provides feel for the pilot when operating the controls.
COMPONENTS
The friction is applied by rotating the serrated handgrip
on the collective stick to its stop.
The basic components of the helicopter flight
control systems are the auxiliary servo cylinder, the
The grip of each collective stick contains several
mixing unit, the primary servo cylinders, and the
switches that are labeled for the function they control.
swashplate.
In the automatic stabilization equipment (ASE) mode
17-7
