An
armoured vehicle-launched bridge
(
AVLB) is a combat support vehicle, sometimes
regarded as a subtype of
combat engineering vehicle,
designed to assist militaries in rapidly deploying
tanks and other
armoured fighting vehicles across
rivers. The AVLB, usually built from a converted tank chassis (and
hence a tracked vehicle), carries a folding metal bridge atop its
chassis, the bridge itself may be in 3 sections. The AVLB's job is
to allow armoured or infantry units to cross water, when a river
too deep for vehicles to wade through is reached, and no bridge is
conveniently located (or sufficiently sturdy, a substantial concern
when moving 60-ton tanks). The bridge-layer unfolds and launches
its cargo providing a ready made bridge across the obstacle, a
process that takes only minutes. Once the span has been put in
place, the AVLB detaches itself from the bridge, and moves aside to
allow traffic to pass. Once all of the vehicles have moved over, it
crosses the bridge itself and reattaches to the bridge on the other
side. It then retracts the span ready to move off again. A similar
procedure can be employed to allow crossings of small chasms or
similar obstructions. AVLBs can carry bridges of 60 feet (19
meters) or greater in length. By using a tank chassis, the
bridge-layer is able to cover the same terrain as
main battle tanks, and the provision of
armour allows them to operate even in the face of enemy fire.
However, this is not a universal attribute: some exceptionally
sturdy 6x6 or 8x8 truck chassis have lent themselves to
bridge-layer applications.
Origins
The roots of the modern AVLB can be found in
World War I, at the dawn of
tank warfare.
Having developed
tanks, the British
and French
were
confronted with the problem of mounting tank advances in the face
of the trenches that dominated the
battlefields. Early engagements, such as at
Cambrai demonstrated the tank's
utility, but also highlighted its vulnerability to battlefield
geography -- many early tanks found themselves ignominiously stuck
in the trenches, having insufficiently long tracks to cross them
(as at right). To counter this disadvantage, tanks (especially the
common British
Mark series) began to
go into battle with
fascines hanging over
their bows, sometimes as simple as a bundle of heavy sticks. By
dropping these into the trenches, they were able to create a wedge
over which the tank could drive. Later, some tanks began to carry
rails on their decks -- the first AVLBs.
World War II & subsequent use
It was in the
World War II era that
that the importance of armoured bridge-layers, as well as
combat engineering vehicles and
armoured recovery
vehicles, became fully clear. With the advent of
Blitzkrieg warfare, whole divisions had to
advance along with tanks, which were suddenly far out-pacing the
speed of infantry soldiers. Besides leading to the advent of
self-propelled
artillery/
assault guns,
mobile anti-aircraft and
armoured personnel
carriers/
cars, it became
clear that functions like vehicle repair, mine-clearing, and the
like would have to be carried out by armoured vehicles advancing
along with tanks. Moreover, these forces would have to be able to
cross all forms of terrain without losing speed, and without having
to concentrate their thrusts over certain bridges (and the rising
weight of armoured vehicles meant that fewer and fewer bridges
could support these massed crossings). The only feasible solution
to the dilemma posed by the mobility of all-mechanised armed forces
was a dedicated platform that could improvise river and obstacle
crossings at short notice and in otherwise inconvenient locations.
Tracked and armoured, it was capable of operating right alongside
combat units, crossing rough terrain and advancing in the face of
light fire. To maximize on common parts and ease maintenance
complications, they were usually based on existing tank
chassis.
One of the earliest series-produced examples is the
Brückenleger IV, a German
AVLB, which entered
Wehrmacht service in
1940; 20 were built. Problems of excessive weight limited the
vehicle's effectiveness, and eventually all 20 were converted back
to tanks. A new scissors bridge design was brought out by the
British in response to the war, sufficient to support a 24 ton load
over 30 ft.
This was developed for the Covenanter tank but developed into a 30 ton
capacity it was carried by a turretless Valentine tank and used in Italy, North West
Europe and Burma
.
The
Allies developed similar equipment,
mostly based on the ubiquitous
Churchill (carrying the
Small Box Girder) and
Sherman medium tanks
of the
British and
U.S. armies, respectively. In some early
designs, bridge-layers could emplace bridges, but not retract them.
Other vehicles were integral to the bridge themselves (such as the
Churchill Ark), wading to the middle of a river or driving up
against an obstacle and extending simple ramps in both directions
); following vehicles would drive directly over the
bridge-layer.
Having proven their utility in the war, and being especially useful
for amphibious operations, many major tank operators (at least,
those with rivers or similar obstacles to cross) employ some number
of bridgelayers, usually converted from existing tank designs
(sometimes using old tank designs no longer useful for front-line
combat service, as in the M60A1 AVLB. A number of designs,
including the French
PTA 2, now use 6x6- or
8x8-wheel trucks as their base instead of tracked chassis.
Notable AVLBs in service
Image:PSB 2 with bridge.jpg|
PSB 2 with
bridge of the
German Army.
References
: Panzerschnellbrücke 2,
based on the Leopard 2 MBT.
: MTU-72 AVLB, based on the T-72 MBT.
: M60A1 AVLB,
based on the M60 MBT. Now supplanted by the M104 Wolverine, based on the M1 Abrams MBT.
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