FLIGHT CONTROL SYSTEM
2.37 FLIGHT CONTROL SYSTEM.
The flight control system (fig 2-25) consists of hydrome-
chanical flight controls, augmented by digital automatic
stabilization equipment (DASE), and an automatically or
manually controlled stabilator. The flight control system
establishes vertical, longitudinal, lateral, and directional
flight of the helicopter. The flight controls provide a cyclic
stick, collective stick, and directional pedals in each crew
station, connected in tandem, to provide control inputs to
the main and tail rotor hydraulic servo actuators. A mixing
unit combines inputs from the servoactuators, and trans-
mits them to a non-rotating swashplate. The swashplate
changes the linear motion from the mixer unit to rotating
motion. The swashplate provides pitch changes for the
four main rotor blades. Pedal inputs are transmitted in a
similar manner to the tail rotor blades, except the mixer
unit is not required. Description and operation of the main
and tail rotor systems is in Section VIII.
Helicopters with operable BUCS have
shear pins installed in the SPADs in place of
steel pins. They also have servos equipped
for BUCS operation.
Each mechanical flight control linkage has a shear pin
actuated decoupler (SPAD) installed. The SPADs allow
backup control system (BUCS) engagement by means of
a microswitch inside each SPAD if a jam occurs in the me-
chanical flight controls. The shear pins in the pilot SPADs
shear at a force lower than those in the CPG SPADs. The
SPADs are continuously monitored by the FD/LS. A single
microswitch failure in one or more axes will cause a FD/LS
message to appear.
Do not move flight controls without
hydraulic power. You may damage or
shear pins in the SPADs.
Care shall be exercised in extending
or folding down the CPG cyclic stick
when the rotors are turning. Cyclic
control system inputs may occur. It is
recommended that the pilot hold his
cyclic stick steady while the CPG is
extending or folding his cyclic stick.
2.37.1 Cyclic Sticks.
The cyclic sticks, one in each
crew station, provide for helicopter movement about the
pitch and roll axes. The CPG stick has a lockpin release
mechanism at the base of the stick. This allows the CPG
to fold the stick down while viewing the heads-down dis-
play and provides greater ease for ingress/egress. The
cyclic stick remains functional in this position and is re-
turned to the extended position by pulling aft on a lever in
front of the stick grip. Both cyclic stick grips (fig 2-26) have
switches for weapons firing, DASE disengagement, trim
feel, radio and intercommunications, and flight modes
symbology. The pilot grip also has a remote transmitter
selector switch for radio selection. These switches will be
described in more detail with their associated systems.
2.37.2 Collective Sticks.
The collective sticks in both
crew stations (fig 2-26) provide the crew with a means of
adjusting pitch angle of the main rotor blades and fuel flow
metering requirements of the gas generator turbine. Each
collective stick has an engine chop collar just aft of the col-
lective stick switch box (see Section III) to permit both en-
gines to be reduced to idle without moving the PWR lev-
ers. A switch panel at the end of each collective stick
contains a searchlight (SRCH LT) switch, an extend-re-
tract (EXT-RET) momentary searchlight switch, a wing
stores jettison guarded button (ST JTSN), a NVS switch,
a BRSIT HMD/PLRT switch, and a radio frequency over-
ride (RF OVRD) switch. The RF OVRD switch is nonfunc-
tional. Both collective sticks have a BUCS select trigger
switch. The switch in the Pilot station is non functional.
The switch in the CPG station is utilized to select BUCS.
These switches will be discussed in more detail with their
respective systems. A twist-type friction adjustment is
installed on the collective assembly to prevent the collec-
tive stick from creeping during flight.
2.37.3 Directional Control Pedals.
control pedals, one set in each crew station, provide for
helicopter movement about the yaw axis. Both sets of
pedals are adjusted by applying foot pressure and moving
a pedal adjust quick-release lever. Pressing the upper
portion of either pedal actuates a master brake cylinder
which delivers hydraulic power to a brake disc at the re-
spective main landing gear wheel. Section I contains de-
scriptions of the main landing gear and brake system.