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.
The explosive content of the weapon is indicated by
a yellow band around the forward end of the cargo
section.
The Mk 7 Mods 3,4, and 6 bomb dispensers differ
from the Mk 7 Mod 2, but the physical appearance of
the dispenser remains basically the same. The most
significant change incorporated on Mod 3 and later
Mods is 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 7 Mod 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 Mods 0 and 1 Mechanical Time Fuze
The purpose of the Mk 339 Mods 0 and 1
mechanical time fuze is to initiate the linear-shaped
charges located in the cargo section walls.
Mk 118 Mod 0 and Mod 1 Antitank Bomb
The antitank bomb Mk 118 Mod 0 (fig. 1-39)
consists of a Mk 1 Mod 0 fuzing system, a
shaped-charge warhead, and fixed stabilizing fins. It is
loaded in the Mk 20 Mods 2 and 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 Mods 4 and 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
Figure 1-39.—Antitank bomb Mk 118 Mod 0 and Mod 1.
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.
When the primary fuze arming wire is withdrawn
from the Mk 339 Mod 0 fuze, the fuze will function after
a 1.2-second (primary) or 4.0-second (option) delay,
depending upon which setting was set in the fuze during
weapon preparation. Functioning of the fuze initiates
the linear-shaped charges in the dispenser; they cut the
dispenser case in half, and disperse the bombs/bomblets.
If the MK 339 Mod 1 fuze is used and only the 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.
1-43
