CLUSTER
BOMBS
ANTITANK BOMB
CLUSTER MK 20, CBU-99, AND CBU-100
The antitank bomb
cluster is an air-launched, conventional
free-fall weapon. The Mk 20, CBU-99, and CBU-100
are used against armored vehicles. The CBUs are
delivered to the fleet as completely assembled
all-up-rounds (AURs). Fuzes, suspension lugs,
arming wires, wire extractors, and all other
necessary components are installed. The Mk 20
bomb cluster weighs 490 pounds and contains 247
Mk 118 antitank bombs. The information on
configuration, functional description, and
shipping and storage containers of the Mk 7 bomb
dispenser and its associated components can be
found in NAVAIR 11-5A-3, also information on
decanning, preparation for use, and recanning
procedures are found in NAVAIR 11-140-9. MK 20
MODS/CBU-99/CBU-100, BOMB CLUSTER CONFIGURATIONS
The configurations of the Mk 20 Mods/
CBU-99/CBU-100 are listed in the table below. Mk
7 and Mods Bomb Dispenser The cargo section of
the Mk 7 bomb dispenser is the main structure of
the weapon and contains the bombs/bomblets. A
nose fairing is attached to the forward end of
the cargo section for aerodynamics and fuze
installation. It has an observation window for
viewing the safe/arm indicator on the installed
fuze. The dispenser has two linear-shaped charges
secured longitudinally inside the walls. When
initiated, these shaped charges cut the dispenser
in half, from front to rear, and the
bombs/bomblets spread in free-fall trajectories.

To stabilize the
weapon after release from the aircraft, a tail
cone assembly is attached to the aft end of the
cargo section. The tail cone assembly houses
four, spring-actuated folding fins. The fins are
spring-loaded to the open position and secured in
the closed position during ground handling by a
fin release-band assembly. The fin release band
is secured in the closed position by a safety
cotter pin and by the fin release wire. A yellow
band around the forward end of the cargo section
indicates the explosive content of the weapon.
The Mk 7 Mods 3, 4, and 6 bomb dispensers have
the Mk 339 Mod 1 fuze, which provides the pilot
with in-flight selection of the fuze function
time. The Mk 7 Mod 4 bomb dispenser differs from
the Mk 7 Mod 3 by modifying the dispenser and
giving interface capabilities with a wider range
of military aircraft. The Mk 7Mod 6 bomb
dispenser is the same as the Mk 7 Mod 3 except
that the outside of the Mod 6 cargo section is
coated with a thermal protective coating and has
an additional yellow band around the forward end
of the cargo section. The addition of the thermal
coating increases the overall weight of the Mod 6
to 505 pounds.
Mk 339 Mod 1
Mechanical Time Fuze
The purpose of the
Mk 339 Mod 1 mechanical time fuze is to initiate
the linear-shaped charges located in the cargo
section walls. 1-35
Mk 118 Mod 0 and
Mod 1 Antitank Bomblets
The antitank
bomblets Mk 118 Mod 0 consists of a Mk 1 Mod 0
fuzing system, a shaped-charge warhead, and fixed
stabilizing fins. It is loaded in the Mk 20 Mod 3
bomb clusters only. In the antitank bomb Mk 118
Mod 1, the fuzing system is a Mk 1 Mod 1, and the
bombs are loaded in the Mk 20 Mod 6 bomb clusters
only.
FUNCTIONAL
DESCRIPTION
When the Mk 20
bomb cluster is released from the aircraft, the
arming wires (primary and/or optional arming) are
pulled sufficiently to arm the Mk 339 fuze and
release the fins. The positive armed fin release
arming wire frees the fin release band, and the
movable fins snap open by spring-force.
Functioning of the fuze initiates the
linear-shaped charges in the dispenser; that cut
the dispenser case in half, and disperses the
bombs/bomblets. When the Mk 339 Mod 1 primary
fuze arming wire is pulled, the fuze will
function 1.2 seconds after the arming wire has
been extracted. If the pilot selects the option
time (4.0 seconds), both the primary and option
arming wires must be pulled. If the pilot selects
the option time and the primary arming wire is
not pulled, the fuze will be a dud.
Mk 118 Mods 0 and
1 Antitank Bomb
When the Mk 118
bomb separates from the dispenser case, the base
fuze-arming vane rotates and the fuze is armed.
If the bomb strikes a hard target, such as
concrete or armor, the electric detonator ignites
the shaped-charge warhead immediately. If the
bomb strikes a soft target, such as earth or
sandbag, the bomb penetrates the targets until
deceleration lets the inertia firing pin strike
and initiate the stab detonator, causing warhead
denotation.
SHIPPING AND
STORAGE CONTAINERS
The Mk 427 Mod 0
and Mod 1 shipping and storage containers encase
one fully assembled Mk 20 bomb cluster. The
reusable containers consist of metal upper and
lower shell assemblies that are secured with
either 16 quick-release latches (Mod 0) or 18
"T" latches (Mod 1). A rubber gasket
provides an environmental seal when the upper and
lower shells are mated. External framemembers are
welded to each half of the container so the
containers can be stacked six high and provide
the necessary fittings for ground-handling
equipment. The reusable weapon cradle Mk 18 Mod 0
is used to ship and store two fully assembled Mk
20 bomb clusters. The cradle consists of plastic
upper and lower shell assemblies, which are
shock-mounted on a metal cradle assembly. The
weapon cradle has forklift guides, lifting eyes;
hand truck brackets, and lifts devices to permit
the use of handling equipment. Four supports are
provided on each cradle to aid in stacking the
cradle assemblies.

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