LCAC And The Over-The-Horizon Amphibious Assault
CSC 1985
SUBJECT AREA Warfighting
EXECUTIVE SUMMARY
TITLE: LCAC AND THE OVER-THE-HORIZON AMPHIBIOUS ASSAULT
I. Purpose: To develop a concept for using the Landing
Craft Air Cushion (LCAC) to conduct an amphibious assault
from beyond the horizon.
II. Problem: Amphibious assault techniques must be devel-
oped to exploit the capabilities of the LCAC, reduce the
vulnerability of the amphibious task force to shore-based
weapons systems, and enable the landing force to achieve
tactical surprise and avoid enemy coastal defenses.
III. Data: The traditional amphibious assault, charac-
terized by ships stationed close to the coastline
discharging slow-moving landing craft and assault amphibian
vehicles (AAVs) toward easily predictable beaches, offers
little hope of achieving tactical surprise, and is
vulnerable to modern defensive weapons. The LCAC can
transport heavy equipment, including tanks and AAVs, at
speeds up to fifty knots directly to inland landing sites.
It is capable of negotiating about seventy-three percent of
the world's coastlines as compared to about seventeen
percent for displacement-type craft. The LCAC can be
carried by all well-deck ships. However, until current
shipbuilding programs are completed, some shortfalls will
exist in the number of LCACs that can be embarked to support
amphibious landings. Employment of the LCAC with existing
and programmed ships, craft, and vehicles to launch an
assault from an amphibious task force stationed beyond the
horizon will present a number of challenges. Naval gunfire
ships will be largely out of range to support the initial
assault. The build-up of combat power ashore will be slow
because the turn-around time for LCACs launched from beyond
the horizon is lengthy. Tank landing ships (LSTs) and
displacement-type landing craft organic to LKAs and MPS
ships must be integrated into the landing plan without
compromising the advantage gained by a high-speed surprise
LCAC assault. Finally, the question of what to do with the
AAVs must be addressed. Assault infantry units landed by
LCACs without AAVs will have limited mobility ashore and no
armored protection. If LCACs are used to land AAVs with the
assault infantry units, the availability of LCACs to land
TOWs, tanks, and artillery in scheduled and on-call waves
will be significantly reduced.
IV. Conclusions: Until the assault elements of the landing
force are established ashore, the amphibious task force must
remain beyond the horizon, not only for its own protection,
but to deceive the enemy as to the location of the attack.
The capability of the LCAC to cross heretofore unassailable
beaches at high speed must be exploited to avoid enemy
defenses and gain surprise. Assault infantry units must
have the necessary mobility ashore to seize deep objectives,
link-up with helicopterborne forces, and exploit the
advantage gained by a surprise landing. The momentum of the
attack must be maintained by accelerating the offloading of
ships, to include using displacement-type craft, to hasten
the build-up of combat power ashore.
V. Recommendations: Future amphibious assaults should be
launched from twenty to twenty-five miles offshore. Es-
corted by attack helicopters, LCACs should carry scheduled
and on-call waves of infantry mounted in AAVs, TOWs, tanks,
and artillery to inland landing sites. Once the leading
elements of the landing force are established ashore, the
amphibious task force should move closer to the coastline to
accelerate offloading by reducing LCAC turn-around time, and
open conventional beaches to accommodate displacement-type
landing craft.
LCAC AND THE OVER-THE-HORIZON
AMPHIBIOUS ASSAULT
OUTLINE
Thesis Statement: Future amphibious assaults will be
conducted by using LCACs launched from ships stationed well
beyond the horizon to carry scheduled and on-call waves of
infantry mounted in AAVs, TOWs, tanks, and artillery to
inland landing sites, whereupon the amphibious task force
will move closer to the coastline to accelerate offloading
by LCACs and, if necessary, open conventional beaches for
displacement-type landing craft.
I. The requirement for an over-the-horizon amphibious
assault capability
II. The Landing Craft Air Cushion (LCAC)
A. Introduction into the fleet
B. Operational characteristics
C. Payloads
D. Compatibility with ships
E. Limitations and vulnerabilities
III. The problems associated with an over-the-horizon
amphibious assault
A. Amphibious ready group configuration
B. Naval gunfire support
C. Ship-to-shore movement distance and time
D. Integration of LCACs, displacement-type landing
craft, and AAVs
1. Displacement-type landing craft
2. AAVs
IV. The concept for conducting an over-the-horizon
amphibious assault
A. Composition of scheduled and on-call waves
1. AAVs in LCACs
2. TOWs, tanks, and artillery in LCACs
B. Control of ship-to-shore movement
1. Approach and retirement routes
2. Landing sites
C. Movement inshore of amphibious task force
D. Opening of conventional beach
E. Concept of fire support
LCAC AND THE OVER-THE-HORIZON
AMPHIBIOUS ASSAULT
It is hard to envision, in 1985, an amphibious assault
against a defended beach. Sufficient naval gunfire ships to
obliterate fortifications and pound enemy defenders sense-
less no longer exist. Lumbering amphibious ships standing
three to five miles offshore are easy prey to modern,
precision-guided, shore-based weapons. Landing craft and
amphibious assault vehicles, remarkably similar to their
1942 predecessors, churning toward an easily predictable
beach at eight miles per hour are themselves vulnerable to
shore-based fires, and offer little hope of attaining
tactical surprise. To be sure, the helicopter permits the
rapid and unexpected landing of light infantry. However,
existing means for landing heavy combat support and combat
service support elements essential for the build-up of
credible combat power ashore have improved little since the
1940's, and arc restricted by reefs, tides, beach gradient
and beach trafficability. Any surprise achieved by heli-
copterborne assault is soon compromised by a ponderous
surface assault.
Because of the vulnerability of all types of ships,
craft, and amphibious vehicles to modern weapons systems,
the modern amphibious assault must be launched from beyond
the range of shore-based target acquisition systems.
Tactical surprise must be achieved to permit the rapid
landing of heavy combat and combat support elements across
undefended beaches before the enemy can react to the as-
sault. Until these parameters are met, many will doubt the
continued practicality of the amphibious assault.
The introduction of the Landing Craft Air Cushion
(LCAC) will make possible surprise landings across unde-
fended beaches, and will prove to be the most revolutionary
development in amphibious warfare since the advent of the
helicopter. In conjunction with helicopterborne assaults,
LCACs launched from twenty to twenty-five miles offshore
will cross undefended segments of coastline at high speed
and land infantry mounted in assault amphibian vehicles
(AAVs), TOWs, tanks, and artillery at sites up to one mile
inland. The ability of an LCAC-equipped amphibious task
force to paralyze enemy defenders by striking unexpectedly
with speed and power promises to rejuvenate the utility and
effectiveness of the amphibious assault.
The first production LCACs have already been delivered
to the fleet. By the summer of 1986, six LCACs will be
operational with Assault Craft Unit Five at Camp Pendleton,
California. During Fiscal Year 1987, Assault Craft Unit
Four, based at Little Creek, Virginia, will begin receiving
the LCAC. By 1992, a total of ninety LCACs will have been
delivered. Assault Craft Unit Five and Assault Craft Unit
Four will each be assigned forty-five LCACs.1 Ultimately,
most conventional landing craft will be replaced with
LCACs.2
The LCAC employs hovercraft technology to skim across
the ocean surface on a cushion of air. It has a range of
two hundred nautical miles.3 With a full payload, it will
exceed speeds of fifty knots in sea state two, and forty
knots in sea state three. Overloaded, it will still achieve
thirty knots in sea state two.4 Unconstrained by winds,
tides, reefs, underwater obstacles, mines, beach gradient
and beach trafficability,5 the LCAC can cross the shoreline
and proceed inland at speeds up to thirty-five knots.6
Ashore, it will cross twenty-foot ditches7 and five-foot
vertical obstacles,8 knock down small trees,9 and climb
gradients up to thirteen percent.10
The most significant operational characteristics of the
LCAC are its ability to cross beaches that heretofore have
been unassailable, and its speed. The LCAC will cross
approximately seventy-three percent of the world's coast-
lines, as compared to about seventeen percent for conven-
tional craft,11 enormously complicating a defender's task.
Conventional landing craft and vehicles travel at speeds of
eight to eleven knots, and must be launched from three to
five miles offshore. The fifty-knot speed of the LCAC
permits the amphibious task force to remain over the hori-
zon, beyond the reach of shore-based target acquisition
systems. The vulnerability of the amphibious task force is
reduced, and the specific location of the landing is not
disclosed by the presence of ships close offshore.
The capabilities of the LCAC facilitate tactical
deception to achieve surprise and project forces across an
undefended beach. To illustrate, an LCAC-equipped amphi-
bious force approaching Norfolk, Virginia, at dusk, can
launch a dawn assault anywhere between Long Island, New
York, and Myrtle Beach, South Carolina!12 Put another way,
with a ship-to-shore transit time of under fifty minutes, an
amphibious task force twenty miles offshore can project
forces ashore anywhere across a forty-mile front!
The LCAC carries a standard sixty-ton payload or an
overload seventy-five ton payload on a sixty-six foot by
twenty-six foot four inch rectangular cargo deck. It is
equipped with bow and stern ramps that will permit drive-
through loading and off-loading of any vehicle organic to
the landing force.13 Typical LCAC loads are shown in Figure
1.
TYPICAL LCAC LOADS
4600 Cubic feet cargo
250 Combat-equipped Marines
3 Assualt amphibian vehicles (AAVs)
4 Light Armored Vehicles (LAVs)
1 Tank and 1 LAV
2 M198 howitzers with prime movers
12 High mobility multipurpose wheeled
Vehicles (HMMWV)
Figure 1*
The LCAC is designed to operate from the well decks of
amphibious ships. On its air cushion it measures eighty-six
feet nine inches in length, forty-seven feet in width, and
twenty-three feet six inches in height.15 It can enter or
depart the flooded or dry well deck of all existing well-
deck ships while the ship is underway or at anchor.16 Newer
classes of amphibious ships, such as the LSD-41 and the LHD,
are being designed specifically to accommodate the LCAC.
Ships capable of carrying LCACs are shown in Figure 2.
LSD-class ships will normally carry one LCAC less than
capacity to provide room for shipboard maintenance.17
Because of the height of the LCAC, LSDs with mezzanine decks
installed will be further limited in the number of LCACs
they can carry.
*Footnote 14.
SHIPS CAPABLE OF CARRYING LCACs
LHD 3 LCACs
LHA 1 LCAC
LSD-28 class 3 LCACs
LSD-36 class 4 LCACs
LSD-41 class 5 LCACs
LPD 2 LCACs
Figure 2*
If current shipbuilding programs are continued, the
amphibious force will be able to lift all ninety programmed
LCACs by the mid-1990's.19 Until then, shortfalls will
occur. Studies have shown that sixty-nine to eighty-three
LCACs will be required to support a Marine Amphibious Force
(MAF) amphibious assault.20 The amphibious force of 1986
will be capable of lifting just sixty-four LCACs.21
Thirty-five to forty-two LCACs will be required to support a
Marine Amphibious Brigade (MAB).22 A representative mix of
ships available to embark a MAB might include three LHAs,
seven LPDs, one LSD-41 class ship, three LSD-36
class ships, and one LSD-28 class ship, with a total capa-
city to lift only thirty-three LCACs. Six to nine LCACs
will be required to support a Marine Amphibious Unit
(MAU).23 Typical amphibious ready groups (ARGs) used to
deploy MAUs are configured with one LHA, one LKA, and one
*Footnote 18
LST, with a total capacity of one LCAC; or one LHA, one LPD,
and one LST, with a total capacity of three LCACs; or one
LPH, one LPD, one LSD, and two LSTs, with a total capacity
of five or six LCACs, depending on the class of LSD.
Like any other vehicle, the LCAC has limitations and
vulnerabilities that must be recognized prior to considering
its employment. It is a big, noisy craft that displays a
characteristic "rooster tail" of sea spray or dust.24
Although tests have shown that it can sustain considerable
damage and continue to operate,25 it is nonetheless an
unarmored craft.26 Essentially a flatland vehicle, its
speed and maneuverability ashore is constrained. It is
particularly difficult to maneuver in reverse.27 Finally,
the LCAC weighs eighty-seven and one-half tons, empty.28 If
disabled ashore, it will be extremely difficult to extract.
In fact, no landing force vehicle is capable of towing it.29
Employment of the LCAC with existing and programmed
amphibious ships, craft, and vehicles to conduct an amphib-
ious assault from beyond the horizon will present a number
of challenges. Configuration of amphibious ready groups
(ARGs), naval gunfire support, time-distance factors
affecting the ship-to-shore movement, and the integration of
LCACs and displacement-type craft are issues which must be
addressed.
As shown above, amphibious ships likely to be available
in the near term to embark the assault echelons of a MAF or
MAB have the capacity to carry a significant number of
LCACs, although slightly fewer than desired. Configuration
of ARGs used to forward-deploy MAUs will have to be
specifically tailored with the capacity to carry the minimum
six LCACs determined to be adequate to support a MAU land-
ing. Of the three ARG configurations in use today (LHA,
LKA, LST; LHA, LPD, LST; and LPH, LPD, LSD, LST, LST), only
the LPH, LPD, LSD, LST, LST configuration will carry six
LCACs, and then only if the LSD is an LSD-41 class.
Introduction of the LHD, capable of carrying three LCACs, to
replace the LPH will significantly improve the situation, as
will the continued production of the LSD-41 class. However,
programmed LCAC deliveries will be completed long before the
last LPH or LSD-36 class ship is retired. In the interim,
LCAC-equipped ARGs will have to be configured with an LPH,
LPD, and an LSD-41 class ship, or with an LHA, LPD, and an
LSD-36 or LSD-41 class ship.
The traditional concept of using naval gunfire for
preparatory fires and to support the amphibious assault
until landing force artillery is ashore will not work for an
assault launched from twenty to twenty-five miles offshore.
Ships armed wish 5"/54 caliber guns will not be able to
reach targets without moving to within visual range of the
coastline, and by doing so will compromise the surprise
achieved by retaining the amphibious task force beyond the
horizon. Even the battleship, with its sixteen-inch guns
effective to twenty-four miles, will have limited utility if
stationed beyond the horizon. The LCAC-borne amphibious
assault launched from beyond the horizon will have to be
supported by alternative means, because naval gunfire ships
will be largely out of range.
Once launched, it is essential that the momentum of an
amphibious assault be maintained by the rapid and continuing
build-up of combat power ashore. Sufficient landing craft
will never be available to land all desired combat, combat
support, and combat service support elements in one lift.
Each craft must make many trips to the beach. This will
remain true with the LCAC. Additional consideration,
however, must be given to the distance the LCAC must transit
in the ship-to-shore movement, and the relatively limited
endurance of the craft as applies to maintaining the momen-
tum of the assault.
Launched from twenty miles offshore, LCAC transit time
to the beach will be about thirty minutes. Ten minutes will
be required to offload in the landing site. Thirty minutes
transit time back to the ship, twenty minutes to enter the
well deck, load, and depart the well deck, and thirty more
minutes transit time back to the beach, all works out to an
hour and a half between the time an LCAC makes its initial
landing and returns with a second load! Turn-around time
for a third trip to the beach will be further increased
because the LCAC must be refuelled after every second trip
ashore!30
Undoubtedly the biggest dilemma facing the amphibious
planner is the integration of fifty-knot LCACs with nine-knot
displacement-type landing craft and eight-knot AAVs into the
ship-to-shore movement plan. The LCAC is designed to
replace the venerable Landing Craft, Utility (LCU), and
Landing Craft, Mechanized (LCM-8). However, LKAs carry
organic LCM-8s, and MPS ships will carry organic LCM-8s, and
causeways.31 The LST is designed to beach itself, or
offload by causeway. These type ships will remain in the
fleet long after the introduction of the LCAC and will
almost assuredly be found in any amphibious task force.
Ship-to-shore movement plans must be designed to capitalize
on the speed and range of the LCAC, yet still provide for
the landing of considerable quantities of supplies and
equipment by displacement-type craft across conventional
beaches.
The assault amphibian vehicle (AAV) is designed to
provide armored protection to the assault elements of the
landing force during the ship-to-shore movement. It pro-
vides mobility ashore, which is particularly critical during
the initial stages of an assault when surface-landed ele-
ments seek to achieve a rapid link-up with helicopterborne