autopilot modes. Control panels are designed for
displacement. It then moves the control surfaces
the particular type and mission of the aircraft.
by an amount commanded by the sensor signal.
Some control panels are simple, while others are
complex. Figure 8-13 is an example of a AFCS
control panel. Here, the switches serve as
AFCS COMPONENTS
manually operated interlocks in setting up the
circuitry to engage the various AFCS modes of
The automatic flight control system (AFCS)
operation. This control panel has six switches.
consists of many controls, sensors, and electro-
They are labeled as follows: ACL/OFF/PDC,
mechanical components. To understand the entire
A L T / O F F / M A C H , HDG OFF/NORM/ROLL
system, you need to know what each component
CMD,
AUTO/STAB-AUG,
ON/OFF,
and
of the system does. In this section, you will
ATTITUDE REF.
read about the components that make up the
AFCS.
T h e ACL/OFF/PCD, ALT/OFF/MACH,
and HDG OFF/NORM/ROLL CMD switches
are solenoid-held toggle switches. Each has a
Electrical/Electronic Components
lever-lock toggle feature that prevents accidental
engagement in the operate position. The AUTO/
The electrical/electronic components make
STAB-AUG and ON/OFF switches are solenoid-
automatic flight control systems work. The
held, spring-loaded switches. When not engaged
control panel is used to program any pilot-desired
or with no power applied, the switches return to
maneuver that is within the capability of the
the STAB-AUG and OFF positions, respectively.
system. Originally, AFCS systems were very
The ATTITUDE REF switch is a miniature,
limited. They supplied only one-channel operation
positive-break, aircraft-type toggle switch.
to the ailerons to keep the wings level. Newer
aircraft receive signals from other aircraft systems.
Radar and barometric altimeter signals couple
AIR NAVIGATION COMPUTER (ANC). --
with the AFCS to maintain the aircraft at a
All operating functions of the automatic flight
constant altitude. Some aircraft use signals from
control systems channel through the air navigation
data-link systems to fly the aircraft during
computer. It is sometimes called the amplifier
approaches and landings. Some fighters have the
computer, and it is the heart of the entire system.
fire control system tied in so the aircraft can fly
The ANC modifies the combined signals
automatically to an enemy aircraft. Fighter
supplied by various sensors and command con-
bombers with a weapons control system tie-in can
trols to develop output signals. The output signals
fly automatically to the target and release their
control the aircraft's ailerons, rudder, and
weapons at the proper time. Long-range patrol
elevators. By use of these flight controls, the
aircraft have their ASW systems tied into their
AFCS. The AFCS operates the rudder, the
aircraft automatically maintains a reference
attitude, heading, and altitude. Also, it can
elevator, and the ailerons by using various sensors
maneuver in a coordinated manner in response
and electrically controlled hydraulic servos. Before
to turn and pitch control settings on the control
engagement, the AFCS is synchronized with the
flight control surfaces to prevent sudden or violent
panel.
maneuvers.
The system senses deviation from the reference
flight condition and causes the aileron control to
maintain either a reference bank angle or a
heading. It also causes the elevator control to
maintain either a reference pitch angle or an
altitude. Also, it makes the rudder control
coordinate turns and provides automatic yaw
damping.
CONTROL PANEL. --The AFCS control
panel contains all the switches and controls
Figure 8-13.-AFCS control panel.
necessary for the pilot to select/control the
