Bombs must be manufactured to withstand reasonable heat and be insensitive   to the shock of ordinary handling. They must also be capable of being dropped from an aircraft in a safe condition when in-flight emergencies occur. Bomb detonation is controlled by the action of a fuze. A fuze is a device that causes the detonation of an explosive charge at the proper time after certain conditions are met. A bomb fuze is a mechanical or an electrical device. It has the sensitive explosive elements (the primer and detonator) and the necessary mechanical/electrical action to detonate the main burster charge. A mechanical action or an electrical impulse, which causes the detonator to explode, fires the primer. The primer-detonator explosion is relayed to the main charge by a booster charge. This completes the explosive train.

Aircraft bombs are released over enemy targets to reduce and neutralize the enemy's war potential. This is done by destructive explosion, fire, nuclear reaction,  and war gases. Aircraft bomb ammunition is used personnel; and tactically in direct support of our land, sea, and air forces engaged in offensive or defensive operations. For safety reasons, some bomb ammunition is shipped and stowed without the fuzes or arming assemblies and associated components installed. This ammunition must be assembled before use. Other types, such as cluster bomb units (CBUs), are shipped  and stowed as complete assemblies, with fuzes or arming assemblies and associated components installed. Bombs are designed to be carried either in the bomb bay of aircraft or externally under the wings or fuselage. The general characteristics and basic principles of operation of bomb ammunition and its associated components are described in this chapter. 

Low-drag, general-purpose (LDGP) bombs are used in most bombing operations. Their cases (bomb body) are aerodynamically designed, relatively light, and approximately 45 percent of their weight are made of explosives. General-purpose bombs may use both nose and tail mechanical or electric fuzes and conical or Snakeye fins. The general-purpose bombs currently in use are the LDGP Mk 80 (series). The specifications for the individual bombs are listed below. The basic difference between the bombs listed below is their size and weight. The following description of the Mk 80 (series) bomb is applicable to all bombs within the Mk 80 (series) unless otherwise noted.

The bomb body is shipped with a plastic plug installed in the nose and tail fuze well to prevent damage to the internal threads and to keep out moisture. The aft end of the bomb body has a metal shipping cap installed. Plastic lug caps are installed in the suspension lug wells, and a plastic plug is installed in the fuze-charging receptacle well. Some bombs contain a hoisting lug packaged in the tail fuze well. Bombs are shipped on metal pallets. The number of bombs loaded on each pallet depends on the bomb size. For example, six Mk 82 bombs can be shipped on a pallet, three Mk 83 bombs can be shipped on a pallet, and twoMk 84 bombs can be shipped on a pallet. Refer to Airborne Weapons Packaging/Handling/Stowage, NAVAIR 11-120A-1.1 or appropriate MIL-STD for more information on shipping configurations. 

FUZE WELLS

The bomb body is designed with a nose and tail fuze well. These wells are internally threaded to receive either mechanical or electric fuzes. FUZE CHARGING CIRCUIT The forward and aft charging tubes are installed at the factory and contain the electric fuze wire harness. When electric fuzing is used, the wire harness provides a path for the charging current from the fuze-charging receptacle to the forward and aft fuze wells. 

SUSPENSION LUGS

There are two suspension lug wells for the installation of suspension lugs. The suspension lugs are spaced 14 or 30 inches apart, depending upon the size of the bomb. Suspension lugs are used to attach the weapon to the aircraft bomb racks. An internally threaded well for the installation of a hoisting lug is located between the suspension lugs, at the center-of-gravity (CG) position on the bomb. The hoisting lug is used for handling purposes only. 

There are two basic nose plugs used in general purpose bombs, the solid nose plug (MXU-735/B and MXU-735A/B) and the ogive nose plug. The ogive nose plug provides a pointed arch. A support cup is used in the nose well with the ogive nose plug to provide a solid structure to the bomb. The MXU-735 solid nose plug is designed to provide better penetration of hard targets, without the likelihood of nose plug shearing during oblique impact. The MXU-735 replaces the ogive nose plug and support cup.

The high-explosive filler of the bomb (H-6) is identified by the yellow stenciled nomenclature on the bomb body and yellow band(s) around the nose. The lot number is stenciled in white ink on the forward end of the bomb. All Mk 80 (series) general-purpose bombs currently being used aboard ships are required to be thermally protected. Thermally protected Mk 80 series bombs can be identified by the words THERMALLY PROTECTED in the identification legend, a bumpy exterior surface, and two yellowbands around the nose.

Arming wire assemblies are used for arming procedures during ordnance evolutions. The primary function of arming wire assemblies is to maintain ordnance components in a safe condition until actual release of the bomb from the aircraft. Normally, the wires consist of one or two brass or steel metal strands attached to a swivel loop. Safety Fahnstock clips  or safety clips, MAU 166, are attached to the ends of the arming wires after installation. They prevent premature or accidental withdrawal of the arming wires from the component. 

NOTE: Safety clips are used vice Fahnstock clips unless otherwise specified. Normally, arming wire assemblies are shipped in spiral-wound fiber tubes, over packed in a wooden box. Generally, the safety Fahnstock clips are packed in the tubes with the arming wires. The most commonly used arming wire assemblies are listed in table below. Arming wire installation procedures are discussed in the TRAMAN where the use of arming wire assemblies is required.

Fin assemblies, used with the Mk 80 (series) LDGP bombs, provide stability to the bomb. They cause the bomb to fall in a smooth, definite curve to the target, instead of tumbling through the air. The fin assemblies, except the MAU-91A/B, are shipped on metal pallets. Each individual fin is crated in a lightweight, disposable metal crate. Some fin assemblies are shipped with bomb lugs attached to the shipping crate, depending upon the particular Navy Ammunition Logistics Code (NALC). Two types of fins are described in this part of the TRAMAN—conical and Snakeye. The conical fin is used for the unretarded mode of delivery, and the Snakeye fin assembly can be used for either the unretarded or retarded mode of delivery.(

The typical BSU-33 conical fin assembly is steel, conical in shape, and has four fins to provide stability. Access covers, attached by quick-release screws, are located on the sides of the fin body, providing access for dearming and inspections. There is a drilled or punched hole at the top and bottom of the forward end of the fin body. This hole is used to install an arming wire when the bomb is being configured for electric tail fuzing. The fin is attached to the aft end of the bomb, and is secured in place by tightening the fin setscrews into the V-groove of the bomb. The conical fin may be used with all Mk 80 (series) bombs. The basic difference between the types of conical fins is their physical size, the larger the bomb, and the larger the fin. 

Snakeye Fin Assemblies

Snakeye fin assemblies are used with the Mk 82 LDGP bombs. They are capable of delivering bombs at high speed and low altitude without the danger of damaging the aircraft from ricocheting bombs or fragments. A physical description of both fin assemblies and the principles of operation are discussed in the following paragraphs.

MK 15 AND MODS SNAKEYE FIN ASSEMBLY.

—The Mk 15 bomb fin assembly is a retarding fin. It is used with the 500-pound LDGP, Mk 82 bombs. The fin assembly presents a low-drag configuration when dropped in the unretarded position and a high-drag configuration when in the retarded position. 

The fin support tube is the main structure of the fin. It provides a means of attaching the fin assembly to the bomb. Eight setscrews attach the fin. The crushing of a convoluted steel tube absorbs the shock. The fin support tube has a fuze-mounting ring for attaching the tail drive of a mechanical tail fuze. The fins are spring-loaded and secured in the closed position by a spring-loaded release band. The release band lever is prevented from opening by a cotter pin, which stays installed until an arming wire is installed. The fin assemblies have drilled holes at the top and bottom of the forward end for installation of arming wires when the weapon is being configured for electric tail fuzing.

MAU-91A/B FIN ASSEMBLY.—The MAU-91A/B fin assembly is a retarded tail fin used with the 1,000-pound LDGP bomb Mk 83 and Mods. This fin assembly can be dropped in either the retarded or unretarded position.

The MAU-91 fin consists of four folding drag plates with links, a support flange, and a support tube. An energy absorber, made of aluminum honeycomb tubing, is located on the support tube between the stationary collar and the sliding collar. The sliding collar is driven against the energy absorber, causing it to compress and deform. A channel located on the top drag plate holds the fin release wire until it is pulled out at bomb release. The drag plates are held in the closed position by a release band that is secured by a fin release wire pin located in the latch of the release band. The band tabs fit into slots located near the end of each drag plate. The band is securely attached to the bottom drag plate by a stainless steel clamp, which prevents damage from the band striking the aircraft after release. Fin adapter ADU-320/B attaches the MAU-91 fins to the Mk 83 bomb. The adapter is secured to the aft end of the bomb by eight setscrews. The fin support flange has eight teeth that mate to ears on the fin adapter. A garter spring is forced into the gap between the flange teeth and the adapter, making sure that the teeth fit tightly against the ears. Two locking pins, which fit through matching holes in the flange and adapter, prevent rotation of the fin. The MAU-91 fin assembly is shipped in a wooden shipping and storage container. Included in the container are eight suspension lugs, one spare garter spring, and a spare locking pin.

There are three modes of delivery available for the Snakeye fin assembly. They are retarded, unretarded, and in-flight selection (pilot option) of either mode.

RETARDED MODE.—In the retarded mode of delivery, the fins open to retard or slowdown the weapon. Since the aircraft and the weapon are traveling at the same speed when the weapon is released, the weapon and the aircraft arrive at the target at the same time. During low-level bombing, the aircraft could be damaged; therefore, the retarded mode of delivery is used during low-level bombing. The fin assembly is positively armed in the retarded configuration. In this configuration, the fin release arming wire is looped over a permanent structure on the bomb rack. As the weapon is released from the aircraft, the arming wire is pulled from the fin release band, and the spring-loaded fins pop open. The fins are forced to the full-open position by the air stream, which causes the weapon to rapidly decelerate and allows the releasing aircraft sufficient time to safely clear the target area.

UNRETARDED MODE.—In the unretarded mode of delivery, the weapon is released from the aircraft, and the fins remain in the closed position. The weapon free falls to the target. In the unretarded mode of delivery (without pilot option), the cotter/safety pin installed in the fin release band is not removed or replaced with an arming wire. However, the safety tag that reads REMOVE BEFORE FLIGHT is removed.

IN-FLIGHT SELECTION.—The most frequently used mode for delivery is the in-flight selection (pilot option) mode. The pilot can drop the weapon in the retarded or unretarded mode. This is possible by connecting the swivel loop of the fin release arming wire to the tail arming solenoid of the bomb rack. If the pilot energizes the arming solenoid upon weapon release, the arming wire remains connected to the arming solenoid and is pulled from the fin release band at weapon release, which allows the fins to pop open and results in a retarded delivery. If the pilot does not energize the arming solenoid upon weapon release, the arming wire is pulled free of the arming solenoid. This allows it to remain in the fin release band, preventing the fins from opening, which results in an unretarded delivery.

The BSU-85/B bomb fin attaches to the Mk 83 general-purpose bomb. It is an air-inflatable retarder designed for very low altitudes. It can be dropped in eith r high-drag (retarded) or low-drag (unretarded) mode. The BSU-85/B fin attaches to the bomb body by eight setscrews. It is a self-contained unit that consists of a stabilizer assembly (canister housing) with four fixed fins (X-shaped) and a lanyard assembly. The four fixed fins provide low-drag aerodynamic stability. The wedges installed on the trailing edges provide stabilizing spin during a low-drag and high-drag release. When stored in its original shipping/storage container, its shelf life is 10 years.

The BSU-86/B bomb fin is used with general-purpose bombs, Mk 82 Mods, or the practice bomb BDU-45/B. The fin provides a retarded (high-drag) or unretarded (low-drag) bomb delivery capability for the aircraft. The BSU-86/B fin is attached to the Mk 82 or BDU-45/B bomb by eight setscrews. A 25-degree wedge is located at the tips of each fin to impart spin. The air stream drives the fin open rapidly, when theMAU-199/B spring arming wire (SAW) is activated. The spring load under each fin blade initiates fin opening. 

Adapter Boosters
Fuzes
Practice Bombs
MK 43 MOD 0 TDD
MK 122 S&A
Destructors