Description
The bomb BLU-7/B and bomb BLU-7A/B are impact fired, parachute stabilized, shaped charge bombs containing impact inertia fuzes. The fuzes are unnumbered and are an integral part of the bombs.
The BLU-7/B is used with the SUU-10/A dispenser (371 loaded). This combination is designated CBU-3/A.
The BLU-7A/B is used with the SUU-10A/A dispenser (352 loaded). This combination is designated CBU-3A/A.
The BLU-7/B consists of a cylindrical body with the tail end formed in a truncated cone. The body contains the shaped charge. The tail of the bomb contains the fuze assembly and parachute. The parachute which is attached to the base of the inertia cap, consists of three strip panels. A wind tab secures the retaining strap which holds the two-piece, clear plastic parachute protector in place. A safety clip fits through the firing pin sleeve and a slot in the threaded end of the safety thumb screw. The clip prevents movement of the thumb screw which, in turn, prevents movement of the firing pin. The safety clip and safety thumb screw are removed prior to installing the bomb in the dispenser.
The fuze mechanism incorporates an out-of-line detonator rotor, lead charge, delay fuze assembly (escapement mechanism), firing pin assembly, and an inertia cap. The detonator rotor is held in the out-of-line position by the firing pin.
The BLU-7A/B is similar in construction to the bomb BLU-7/B with the exception of the fuze assembly, parachute design, and parachute attachment. The fuze is fully enclosed in a plastic protector. The parachute consists of four triangular panels and is attached to the telescope pin by a swivel. A safety wire passes through the parachute protector, fuze body, and telescope pin. The safety wire prevents movement of the telescope pin which holds the firing pin against the compressed anti-creep spring and locks the detonator rotor in the out-of-line position. In addition, a detent wire also holds the telescope pin in the down position. The safety wire is removed prior to loading the bomb in the dispenser.
The fuze mechanism consists of a delay assembly (escapement mechanism), out-of-line detonator rotor, anti-creep spring, firing pin, telescope pin, and detent wire.
The BLU-7/B and BLU-7A/B bomb bodies are aluminum; the shaped-charge liner is copper; the parachute protector is clear plastic; and the wind tab, retaining strap, and fuze are steel.
The BLU-7/B and BLU-7A/B bomb bodies are anodized black. The parachute protector is clear plastic. Markings are in yellow. The fuzes are unpainted.
There is no external means of determining if a fuze has armed or misfired and whether the firing pin is embedded in the detonator.
Functioning
Functioning of the bombs BLU-7/B and BLU-7A/B is identical. As the bomb is released from the dispenser, the wind tab is stripped off by the airstream and unfastens the retaining strap. The parachute protector falls free allowing the parachute to be deployed.
Bomb BLU-7/B - Parachute drag causes the inertia cap to move upward. Upward movement of the inertia cap causes the actuating pin to move upward and pull the firing pin clear of the detonator rotor assembly. As the firing pin clears the rotor, the rotor spring forces the detonator into alignment with the firing pin and lead charge. The escapement mechanism slows down rotor movement providing a short delay. Upon impact, the inertia cup moves downward driving the firing pin into the detonator, initiating the explosive train.
Bomb BLU-7A/B - Parachute drag pulls the telescope pin free of the detent wire. The firing pin, no longer restrained by the telescope pin, is forced upward by the anti-creep spring. As the firing pin clears the rotor, the rotor spring forces the rotor to turn to the in-line position. Delay in arming is provided by the escapement mechanism slowing down the rotor movement. Upon impact, the firing pin overcomes the resistance of the anti-creep spring and strikes the detonator, initiating the explosive train.
Hazardous Components
Each bomb BLU-7/B and BLU-7A/B contains an M55 detonator, a booster (3.7 grams PBX), and a main charge of 0.6 pound (0.3 kg) of Comp B.
Physical Data
Height, overall (BLU-7/B) - 7.86 in, 199.6 mm
Height, overall (BLU-7A/B) - 8.28 in, 210.3 mm
Diameter - 2.75 in, 69.9 mm
Weight - 1.4 lbs, 0.64 kg
See Also
Dispenser, SUU-10A, SUU-10A/A
Source(s)
TM 9-1385-51, Ammunition (Conventional) for Explosive Ordnance Disposal (1967)
