stick position. Both signals are used by the
stabilator to counteract tail rotor downwash on
DAFCS computer for signal level comparison and
its upper wing surface. No. 1 and No. 2 filtered
for software generation of collective-to-yaw pedal
lateral acceleration is used by the DAFCS
coupling.
computer for signal quality comparison and
software generation. No. 1 filtered lateral
STABILATOR AMPLIFIER. --Processing of
acceleration is also used in analog SAS for slip
airspeed, lateral acceleration, collective stick
or skid correction above 50 knots.
position, and pitch rate is accomplished within
each stabilator amplifier. The amplifiers contain
STABILATOR POSITION INDICATOR. --
a power supply, processing and feedback circuits,
Stabilator position is displayed by an indicator on
and a fault monitor circuit. Sensor inputs are
the center of the cockpit instrument panel. This
processed, summed, and applied to a motor driver
indicator is a synchro-type device driven by a
circuit. The motor driver circuit output is applied,
synchro transmitter mounted in the stabilator
through contacts of relays, to the respective
position transmitter and limit switch assembly in
stabilator actuators. Any difference of actuator
the tail pylon.
position is sensed by the fault monitor circuit in
STABILATOR CONTROL PANEL. --Con-
either or both amplifiers, causing an automatic
mode disengagement.
trol functions for the system are provided by the
stabilator control panel. The panel consists
ACTUATORS. --Two actuators position the
of an AUTO CONTROL PUSH TO RESET
stabilator. Each actuator contains an electric
push-button switch, a TEST push button, and a
motor (geared to a jackscrew), limit switches, and
MAN SLEW UP/DOWN switch. Engagement of
a feedback potentiometer. The potentiometer
the system is automatic, upon application of
provides actuator position feedback to each
helicopter ac and dc power, provided all interlocks
amplifier. The actuators extend or retract, as
are in their proper condition.
necessary, to position the stabilator.
TEST Push Button. --A TEST push button,
PITCH RATE GYROS. --There are two pitch
operational below 50 knots, provides a check of
rate gyros--No. 1 and No. 2. Each rate gyro
the system fault monitors by inserting an airspeed
produces a dc output signal relative to the pitch
derived test signal into the No. 1 system. This
rate of the aircraft. Each rate gyro signal goes to
signal drives only the No. 1 stabilator actuator,
which produces a difference between the two
its respective stabilator amplifier, where it is
actuators. The fault monitor circuit in either the
conditioned. The stabilator system uses the
filtered pitch rate signal to enhance the AFCS
No. 1 or No. 2 amplifier, or both, should
disengage the automatic mode of operation when
systems ability to correct short-term pitch
the programmed threadhold trips.
disturbances. The DAFCS computer uses No. 1
and No. 2 filtered pitch rate signals for signal
MAN SLEW UP/DOWN Switch. --If the
quality comparison and software generation. The
No. 1 filtered pitch rate signal is also used in
automatic mode disengages, and cannot be reset
due to a malfunction, the MAN SLEW switch is
analog SAS for short-term pitch correction of the
used to manually position the stabilator. Relays
rotor head.
in the No. 1 and No. 2 stabilator amplifiers are
Digital Automatic Flight Control System
operated by dc power from the switch, when it
(DAFCS)
is placed to UP or DOWN. Using the switch,
when the automatic mode is engaged, will
disengage the automatic mode. As a result, the
The central component of the DAFCS is the
STABILATOR caution light will go on, and a
digital computer. The computer commands the
pitch bias actuator (PBA), the inner-loop SAS
beeping tone will be heard in the ICS.
actuators, and the outer-loop trim actuators in all
COLLECTIVE STICK POSITION SENSORS.
four control channels. The computer also provides
Collective stick position also affects the stabilator
self-monitoring, fault isolation, and failure
position schedule. Stick position is sensed by two
advisory.
collective stick position sensors. No. 1 and No.
The DAFCS uses two types of control
2 collective stick position sensors each produces
identified as inner loop and outer loop. The
inner loop (SAS) uses rate damping to improve
a dc output signal proportional to the collective
