2-5-2. THRUST CONT Lever.
Either THRUST CONT lever 712 (fig. 2-5-1) or 714A
(fig. 2-5-1) is used to apply equal pitch simultaneously to
both rotors, thus controlling ascent and descent of the
helicopter. Raising the THRUST CONT lever increases
pitch. Lowering the THRUST CONT lever decreases
An integrated lower control actuator (ILCA) is installed
between the THRUST CONT lever and the mixing unit.
This actuator assists the pilot in moving the THRUST
CONT Lever. A cockpit control driver actuator (CCDA) is
also installed in the thrust control system. This actuator
responds to signals from the AFCS and increases or
decreases collective pitch on the blades to maintain a
constant altitude. In addition, a balance spring is installed
that counteracts the downward imbalance of the
THRUST CONT level.
If the THRUST CONT lever CCDA fails, the
THRUST CONT lever will slip when force be-
tween 7 and 23 pounds is applied.
A BRAKE TRIGGER switch under each THRUST CONT
grip controls the magnetic brake of the CCDA in the flight
control closet. Pressing the switch applies electrical pow-
er to release the magnetic brake in the THRUST CONT
lever CCDA. The THRUST CONT lever can then be free-
When barometric or radar altitude hold has been se-
lected, pressing the trigger will disengage altitude hold.
When the switch is released, power is applied through
the simplex clutch to the THRUST CONT lever CCDA
and the AFCS will hold the altitude. Power is supplied to
operate the THRUST CONT lever magnetic brake from
DC essential bus through the THRUST BRAKE circuit
breaker on the No. 1 PDP.
The 712 THRUST CONT lever is also electrically linked
to the power turbine actuator through the droop elimina-
tor system. An upward movement of the THRUST CONT
lever electrically increases the power turbine governor
speed setting to compensate for inherent engine droop
and maintain engine speed as rotor loads are increased.
A downward movement of the THRUST CONT lever
electrically decreases the power turbine governor speed
The 714A system includes both thrust lever position
compensation and thrust lever rate compensation.
A detent capsule establishes a ground operation detent
to reduce droop stop pounding. A viscous damper in the
thrust control system improves control feel. Mounted on
each THRUST CONT lever is an auxiliary switch bracket
containing a SEARCH LIGHT control switch, a SLT-FIL
(search light filament) switch, two ENGINE BEEP TRIM
switches, and a HUD control switch.
2-5-3. CYCLIC Stick.
Each cyclic stick (fig. 2-5-2) is used for lateral and longitu-
dinal control of the helicopter. Moving the cyclic stick to
the right tilts both rotors disks equally to the right and
causes the helicopter to roll to the right in flight. Moving
the cyclic stick to the left causes the opposite movement.
When moving the cyclic stick forward, the pitch of the fwd
rotor blades is decreased collectively, while the pitch of
the aft rotor blades is increased collectively, thus causing
a nose-down helicopter attitude in flight. Moving the cy-
clic stick aft causes the opposite movement resulting in
a nose-up attitude.
Two ILCAs, one for lateral control and one for longitudi-
nal control, are installed to assist the pilot in moving the
cyclic stick. In addition to these actuators, viscous damp-
ers are installed. One damper is for longitudinal control
and one for lateral control to improve control feel.
Located on the pilot and copilot cyclic stick grips are a
CENTERING DEVICE RELEASE switch, an AFCS
TRIM switch, a CARGO HOOK RELEASE switch, inter-
phonetransmitter TRIGGER switch, and a FLARE DISP
(dispenser) control switch.
2-5-4. CENTERING DEVICE RELEASE Switch.
The CENTERING DEVICE RELEASE switch (fig. 2-5-2)
is used to simultaneously release the force feel trim mag-
netic brakes for the lateral, longitudinal, and directional
flight controls. In addition, it disengages bank angle hold,
heading hold, and heading select functions when AFCS
is operating. Power is supplied to operate the magnetic
brakes from the DC switched battery bus through the
CONT CENTER circuit breaker on the No. 1 PDP.
A centering spring and magnetic brake for each control
provide a sense of force feel to hold the control in a trim
position. However, the pilot can override the force manu-
ally while maneuvering the helicopter. When the switch
is pressed, electrical power is applied to release the mag-
netic brakes. Each centering spring assumes a new trim
position where the control forces are nulled. Releasing
the switch removes electrical power and applies the
magnetic brakes. The centering springs are retained in
their new positions.