while engaged, the barometric altitude hold
the following conditions are maintained for 2
automatically engages. Integrated vertical
seconds:
acceleration provides short-term radar altitude
corrections, and rate information from the radar
Aircraft roll attitude is within 2 degrees of
altimeter altitude signal provides long-term
wings level.
updates.
less than 2 degrees per
Yaw rate is
HOVER AUGMENTATION/GUST ALLE-
second.
V I A T I O N . --An additional feature of the
SAS, provided only through SAS 2, is hover
The heading hold is disengaged by the weight-
a u g m e n t a t i o n / g u s t alleviation. It further
improves aircraft stability at low airspeed using
on-wheels switch when the aircraft is on the
ground.
attitude retention and longitudinal and lateral
acceleration to eliminate drift.
ALTITUDE HOLD. --Either barometric or
TURN COORDINATION. --Automatic turn
radar altitude hold is selectable from the AFCS
coordination is provided at airspeeds greater than
CONTROL panel. With the altitude hold mode
50 knots. Turn coordination lets the pilot fly a
on, the DAFCS computer uses a reference
coordinated turn with directional control provided
altitude. The reference altitude comes from either
by the AFCS. The AFCS uses lateral acceleration
the air data transducer or the radar altimeter,
depending on whether barometric altitude hold
and roll rate to determine if the aircraft is out of
or radar altitude hold is selected. The DAFCS
balanced flight. It also provides the yaw SAS and
computer uses altitude and rate from the
yaw trim with the inputs necessary to maintain
an automatic coordinated turn. Automatic turn
barometric or radar altitude systems (depending
coordination is engaged and heading hold
on which hold mode is selected) and vertical
disengaged when roll attitude is greater than 1
acceleration to command the collective SAS and
degree, and any of the following conditions
trim actuators. The computer also monitors
exist:
engine torque to prevent dual engine torque from
exceeding 116 percent whenever the collective trim
is positioning the collective. Barometric altitude
Lateral cyclic force is greater than 3.0
hold is engaged at any altitude and airspeed by
percent stick displacement.
depressing the BAR ALT PBS with SAS 2 and
autopilot engaged. Depressing the collective
Cyclic trim release is pressed.
trim release button temporarily disengages
the mode. Upon release of the trim switch,
barometer altitude hold automatically re-engages
Roll attitude is beeped beyond 2.5 degrees
and maintains the altitude at the time of
of bank angle.
re-engagement. Radar altitude hold is engaged at
any altitude from 0 to 5,000 feet AGL and at any
Actuation of the collective-mounted heading
airspeed by depressing the RDR ALT PBS with
slew for greater than 1 second provides a 1 percent
SAS 2 and autopilot engaged.
per second coordinated trim.
When in the hover coupler mode, altitude hold
MANEUVERING STABILITY. --Pitch
is referenced to the altitude selected on the AFCS
control forces are increased to increase pilot effort
CONTROL panel HVR ALT potentiometer.
required for a given pitch rate at bank angles
Depressing collective trim release temporarily
greater than 30 degrees. The higher pitch control
disengages the mode. Upon release of the
forces help alert the pilot to g loading during
trim switch, radar altitude hold automatically
maneuvering flight, and are provided through the
re-engages to the altitude selected on the AFCS
longitudinal trim actuator. A linear longitudinal
CONTROL panel HVR ALT potentiometer.
When in the hover coupler mode, transition
stick force gradient is provided by trimming 1
percent forward stick for each 1.5 degrees angle
from one altitude to another is made with
of bank between 30 degrees and 75 degrees. At
the HVR ALT knob on the AFCS CONTROL
75 degrees angle of bank, the longitudinal stick
panel. If the radar altitude mode should fail
8-34
