3B-25. AUTOMATIC FLIGHT CONTROL SYSTEM.
a. Description. The Automatic Flight Control
System is a completely integrated autopilot/flight
director/air data system that has a full complement of
horizontal and vertical flight guidance modes. These
include all radio guidance modes and air data oriented
When engaged and coupled to the Flight
Director (FD) commands, the system will control the
aircraft using the same commands displayed on the
attitude director indicator. When engaged and
uncoupled from the flight director commands, manual
pitch and roll commands may be inserted using the
Touch Control Steering (TCS ) or the pitch wheel and
When the autopilot is coupled, the flight director
performance of the autopilot. When the autopilot is not
engaged, the same modes of operation are available
for flight director only. The pilot maneuvers the aircraft
to satisfy the flight director commands, as does the
autopilot when it is engaged.
b. Air Data Computer. A digital air data
compartment, provides the altitude information for the
pilot's encoding altimeter, altitude alerter, flight data
recorder, and transponder. The computer also
provides altitude and airspeed hold function data to the
flight control computers. The air data computer
receives 28 Vdc power through, and is protected by, a
2-ampere circuit breaker, placarded AIR DATA
ENCDR, located in the AVIONICS section of the
overhead circuit breaker panel, Figure 2-16, Sheet 3.
All air data computer functions are automatic in nature
and require no flight crew action.
c. Autopilot Flight Director Transfer Switch.
An alternate action autopilot and flight director transfer
switch, placarded AP FD 1 and AP FD 2, is located on
the pilot's instrument panel directly below the glare
shield. Refer to Figure 2-17, Sheet 2. This switch is
used to select which autopilot flight director computer
controls the aircraft flight servos. If AP FD 2 is
selected, the annunciator, placarded AP FLT DIR NO.
2, located on the copilot's instrument panel directly
below the glare shield, will illuminate to alert the pilot
that the No. 2 autopilot flight director computer is
controlling the aircraft.
transferring between the pilot and copilot
d. Flight Director/Mode Selector. The flight
director/mode selector located on the pedestal, Figure
2-9, Sheet 1, provides for selection of all modes,
except go-around that is initiated by remote switches
located on the left power lever and on the copilot's
control wheel, for the flight director. The top row of split
light annunciated push buttons contains the lateral
modes and the bottom row contains the vertical
modes. The mode buttons will illuminate when
manually selected or automatically selected through
other modes. Refer to Figure 3B -16.
illuminate amber for armed conditions and green for
captured. When more than one lateral or vertical
automatically arms and captures the submode. Mode
annunciation is also presented on remote annunciator
blocks, located above both (pilot and copilot) Attitude
Director Indicators (ADI's), and on the pilot's ADI.
e. Autopilot Modes of Operation.
(1) Heading Mode Selector (HDG). The
heading select mode is selected by pressing the HDG
button on the mode selector. In the HDG mode, the
flight director computer provides inputs to the
command cue to command a turn to the heading
indicated by the heading bug on the HSI. The heading
select signal is gain programmed as a function of
airspeed. When HDG is selected, it overrides the
NAV, BC APR and VOR APR modes. In the event of
a loss of valid signal from the VG or compass, the
command cue on the ADI is biased out of view.
(2) Navigation Mode Selector (NAV). The
navigation mode represents a family of modes for
various navigation systems including VOR, localizer,
TACAN and VLF.