These ships use new and improved radar, sonar,
electronic countermeasures, and communications
systems to enhance their detection capabilities.
Another major surface unit is the aircraft
carrier, with ASW aircraft embarked. A carrier
can monitor midocean areas beyond the effective
range of land-based patrol aircraft.
Aircraft have the ability to investigate distant
contacts rapidly and are relatively invulnerable
to submerged submarines. They also have the
advantages of speed, relatively long range, and
weapons-carrying capability. Therefore, they may
fulfill the antisubmarine mission independently
or in coordination with other types of anti-
The three basic antisubmarine warfare aircraft
are long-range patrol aircraft, medium-range
carrier-based aircraft, and helicopters. We
described some of these aircraft, primarily the
P-3C Orion, the S-3A Viking, and the LAMPS
III helicopters, earlier in this chapter. These
aircraft use a wide variety of electronic devices
to detect submarines.
The magnetic anomaly detection (MAD)
device is used mainly for submarine classification
purposes. Depending on the height of the aircraft
and other variables, it can detect a submarine by
variations in the earths magnetic lines of force.
Because of its limited range, MAD is unsuitable
as a device for open area searches. However, it
is effective when used in geographically or
tactically defined or restricted small areas.
Aircraft normally use the MAD device to detect
the specific location of a submarine before they
Expendable sonobuoys, used with measured
success against submarines of the last war, are
very useful against submarines in a variety of
tactical situations. Sonobuoys are tubes containing
a hydrophore and radio transmitter. As aircraft
drop them into the water, the hydrophores pick
up sounds and broadcast them to surface craft
or aircraft. Each sonobuoy is on a slightly
different frequency. An active buoy is also used
that emits a sound signal and listens for the return
Since helicopters are capable of hovering, they
use a different piece of equipment. The aircraft,
by means of a long cable, lowers a cylindrical
sonar transducer into the water while hovering
over the suspected contact area. With this gear
the helicopter can listen or echo-range (determine
the location of a submarine).
Other methods of detection include infrared
detection and explosive echo ranging using
In all types of airborne electronic ASW
devices, proper training of both operating and
maintenance personnel is paramount to successful
application of the equipment. Certain applications
require special techniques for effective use of
sonobuoys and other sonic devices. Proper and
accurate sound identification and spotting of
snorkel targets on radarscopes are examples.
The submarine itself is perhaps the most
effective antisubmarine vehicle. It operates in the
same medium as the target and shares the targets
advantages of concealment and passive detection.
(Passive sonar depends entirely on the targets
noise as the sound source rather than the returned
echoes of a transmitted signal.) The submarine
can detect enemy submarines while working with
other ASW forces or while working independently.
Submarines can precede carrier strike forces into
enemy waters, function as ASW screens, and operate
as minelayers. Fleet ballistic missile submarines are
used to destroy enemy targets when ordered by the
President of the United States.
SOUND NAVIGATION AND
The use of sonar (sound navigation and ranging)
is the principal method of submarine detection. We
have two types of sonarpassive and active. Sonar
is an electronic device that either detects underwater
sounds or transmits them. Passive sonar detects
sounds originating under water. Active sonar is an
electronic device that can transmit (through the
depths) a sound wave which, upon striking an
object, will reflect. Submarines use passive sonar
to enable them to detect noise-making objects
without transmitting a telltale ping themselves.
To understand how sonar works, you must first
understand sound. Sound is the physical energy that
causes the sensation of hearing. It travels in the form
of waves away from the point of origin, as ripples
travel out in all directions from a pebble tossed
into a pond. Echoes are created when sound waves
strike objects through which they cannot travel and
therefore bounce back to the source.