Mk 7 and Mods Bomb Dispenser

The cargo section of the Mk 7 Mod 2 bomb dispenser (fig. 1-38) 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 mechanical time fuze Mk 339 Mod 0 is installed in the nose fairing and is protected during ground handling by the fuze cover assembly. 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.

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.