CHAPTER 9
AUTOMATIC CARRIER LANDING SYSTEM
The most demanding task facing a pilot is the
landing of the aircraft on an aircraft carrier in rough
seas. Landing an aircraft on a stationary land airstrip
is hard enough. Add to that task the motion of the
carrier in the water, the wave action, and the vortex of
air caused by the island, and you can see the problems
facing the pilot.
With the electronic technology of today, the
carrier landing is made easier for the pilot. The
automatic carrier landing system (ACLS) is a great
aid to the pilot. This system, once engaged, provides
the aircraft with the following capabilities:
Data link roll commands are used to intercept
and lock onto the landing pattern.
Data link pitch commands establish the proper
glide path.
The autopilot provides warnings if the
automatic carrier landing mode becomes
uncoupled or is degraded.
This system does not guarantee a perfect landing,
nothing can do that. What this system does do is to
ensure that the pilot and aircraft have the best and
safest possible approach and descent to the carrier
deck and touchdown.
AUTOMATIC CARRIER LANDING
SYSTEM COMPONENTS
Learning Objective: Recognize systems,
subsystems, and components used in the
automatic carrier landing system.
Although this system is used on the aircraft, some
of the subsystems are located on the aircraft carrier.
There is no ACLS “box” on the aircraft. This system
uses parts of other systems already onboard the
aircraft. Figure 9-1 shows how the ACLS com-
ponents interface and the signal data.
AUTOMATIC FLIGHT CONTROL
SYSTEM AN/ASW-42
The automatic flight control system (AFCS or
autopilot) is located on the aircraft. This system
provides the interface between the data link and the
aircraft flight control surfaces. It is the system the
pilot uses to select ACLS. The AFCS provides
switching and signal conditioning, engage logic,
command signal limiting, and failsafe interlocks. The
failsafe interlocks are required to couple and process
data link signals to the pitch and bank channels of the
AFCS. Automatic synchronization is provided in all
three axes.
DIGITAL DATA COMMUNICATION SET
AN/ASW-25B
The digital data communication set (DDCS)
receives the data link messages and signals, screens
out invalid messages, and then sends the signals to the
AFCS. The DDCS is located in the aircraft.
RECEIVING-DECODING GROUP
AN/ARA-63
The receiving-decoding group (R-DG)
determines the glide-path errors from the carrier’s
instrument landing system radar. It also converts the
data into signals for the pilot’s flight path cross
pointers. The R-DG is used for airborne monitoring
of Mode I approaches and for Mode II. All three
modes (Mode I, Mode II, and Mode III) will be
discussed later in this chapter.
INSTRUMENT LANDING SYSTEM
AN/SPN-41
The instrument landing system (ILS radar)
transmits the glide path pulse-coded Ku-band
information from the carrier to the aircraft. This
system is located on the carrier and uses two antennas.
One antenna is used to transmit azimuth information,
and the other transmits elevation information. Both
signals are processed by the R-DG on the aircraft.
9-1
