stabilized deck-coordinated system referenced to the
touchdown point on the flight deck.
3. Digital computer. This is a general-purpose
computer used to provide functions for radar data
stabilization, data filtering, and computations
required for control of the aircraft.
4. Data link monitor. This subsystem con-
tinuously checks data link transmissions for errors. If
the messages do no check properly, the monitor will
switch the system to either Mode II or Mode III, or
will generate a waveoff signal.
5. Control console. This console monitors and
controls the various functions of the landing system.
RADAR BEACON AN/APN-154B
The radar beacon is located on the aircraft and is
used to receive the Ka-band signal interrogations
from the LCC radar. The radar beacon then transmits
X-band replies to the carrier to provide
aircraft position data.
APPROACH POWER COMPENSATOR
The approach power compensator
automatically adjusts throttles to maintain the
angle-of-attack, and thus, the airspeed during aircraft
It can be used for all carrier
landings and is required for Mode I approaches. For
Mode II and Mode III approaches, the APC is
optional. Data from the angle-of-attack transducer,
normal accelerometer, and the stick/stabilizer position
are used to control an electromechanical servo
actuator. This servo actuator is coupled to the throttle
linkage on the engine fuel control.
ATTITUDE REFERENCE INDICATOR
The ID- 1791/A (VGI) is used to display the glide
path errors from either the data link or monitor link on
cross pointer needles. This indicator also determines
and displays backup pitch and roll attitude, as well as
displaying side-slip and turn rate.
DISCRETE MESSAGE INDICATOR
This indicator is located on the aircraft. It
displays nine status indications from the one-way link
system, autopilot, and the beacon radar.
WARNING INDEXER PANEL
Three warning lights on the warning indexer
panel informs the pilot of the status of the approach
power compensator, the status of the AFCS, and
whether a waveoff has been initiated. The three
indicators are the APC STBY, AFCS OUT, and the
WAVEOFF indicators. The APC STBY will
illuminate when the APC is in standby. The AFCS
OUT will illuminate when the autopilot system is not
The WAVEOFF indicator will
illuminate when a wave-off has been initiated. When
either the AFCS OUT or the WAVEOFF indicators
illuminate while in Mode I approach, the pilot is
required to immediately take over control of the
APPROACH INDEXER 1284V653-1
This unit is located on the aircraft. It provides an
additional angle-of-attack in the pilots field of view.
This unit is used when flying cross pointers on a
Mode II approach or when monitoring display on a
Mode I approach.
PRINCIPLES OF OPERATION
Learning Objective: Recognize the operating
principles of the automatic carrier landing
The all-weather combination AFCS/ACLS
provides automatic, semiautomatic, or manual
operation for aircraft carrier operations with
minimum use of airborne electronic subsystems. The
aircraft control commands are generated by shipboard
computers so that the necessary pitch and bank
signals can be received by the AFCS via the one-way
data link system. This closed-loop operation between
aircraft and carrier provides automatic control to
touchdown. This system provides a final approach
and landing for carrier-based aircraft during daylight
or darkness, with minimum interference for
conditions of severe weather and sea state, and no
limitation due to low ceiling and visibility.
There are three modes of operation of the ACLS
that can be selected by the pilotMode I, Mode II,
and Mode III. Mode I is a fully automatic approach
from entry point to touchdown on the flight deck.
Mode II requires manual control of the aircraft. In
this mode, the pilot controls the aircraft by observing