released, the hold mode (airspeed or altitude)
Actuator failure--power removed from
associated with that control axis is engaged. The
actuator.
aircraft continues to follow the depart profile for
the other axis until the final cruise condition for
If the system malfunctions, the BIAS Fail
that axis is met.
Advisory light on the AFCS CONTROL panel
The automatic depart mode is an outer-loop
will go on, and, in some cases, remove power
function operating through the pitch, roll, and
from the actuator. If the malfunction that caused
collective trim actuators. As in the automatic
the shutdown was of an intermittent nature, the
approach mode, above 60 KIAS, roll attitude is
actuator operation can be reset by pressing the
maintained, and below 60 KIAS, the DAFCS
appropriate MODE RESET button.
commands roll to eliminate lateral drift.
CREW HOVER. --The crew hover feature lets
the crewman position the helicopter during hoist
and rescue operations. The crewman controls the
REVIEW SUBSET NUMBER 4
aircraft from the crew hover-trim panel. The crew
hover controller has a control authority of 5
knots. This authority is laterally and longi-
tudinally about the reference values selected on
the AFCS CONTROL panel plus the speeds
beeped from the cyclic trim beep switch, The crew
hover feature is activated from the AFCS
CONTROL panel by depressing the CREW HVR
button. It can only be activated if the hover
coupler mode is already engaged.
PITCH BIAS ACTUATOR (PBA). --The
PBA provides longitudinal cyclic displacement
proportional to airspeed. The DAFCS commands
the PBA as a function of pitch attitude, pitch rate,
and airspeed. The PBA is an electromechanical
series actuator with 15 percent control authority
and 3 percent per second rate limit. The PBA
functions automatically upon application of
power to the DAFCS computer, and it isn't
selectable on the AFCS control panel. The
DAFCS computer monitors the PBA position to
confirm correct response to the input commands.
If the PBA fails, the DAFCS lights the BIAS
advisory light and flashes the AFCS DEGRADED
light. Also, the DAFCS commands the PBA to
a predetermined position, depending on the type
of failure. The PBA is driven by the DAFCS
computer as a function of airspeed, pitch rate,
and pitch attitude. PBA failure modes are as
follows:
Attitude failure--bias actuator centered
Pitch rate failure--faded out pitch rate
component
A i r s p e e d failure--actuator goes to
120-knot position and attitude and rate
continues to function.
