4.5-in. Photoflash Bomb Mks I and II, and 4.5-in Heavy Photoflash Bomb (Service)

Description: The Photflash Bombs Mk I and Mk II are similarly constructed, the only difference being that the Mk II has narrower tail fins. Each flash has a tubular body, clo-sed at the tail by a closing dome and at the nose by a front diaphragm having a bush in-to which is screwed the nose fuze. The four tail fins are located at the after end. A quantity of flash composition is contained in the body between a front and rear dia-phragm. The filling hole is closed by a press-cap and overseal. A central tube, closed at each end, extends between the front and rear diaphragm and is filled with gunpowder. A socket secured to the fron diaphragm houses a perforated disc, and a muslin disc, which closes the nose end of the central tube. The perforated disc is held in position by a soc-ket plug having a flash hole covered by a disc, which, in earlier issues, is made of brass, but in later issues is paper.

Functioning: When the fuzed bomb is released from an aircraft, its fuze is set in ope-ration and the flash falls until the magazine charge of the fuze explodes. The flash from the magazine charge passes through the perforated disc and ignites the gunpowder in the central tube. The gunpowder explodes, burst the body of the photographic flash, and simultaneously ignites the flash composition.

Suspension: The bomb is suspended by means of a suspension band to which are se-cured two suspension lugs, one for attaching to a Light Series bomb carrier, and the other for attaching to a Universal bomb carrier.

Remarks: These flash bomb are intended to proivide illumination for night photogra-phy, and when activated they explode with a loud report and a vivid white flash. It is im-portant to distinguish between flares and photoflash bombs. They may be distinguished by the following characteristics. FLASH is stencilled on the nose of all photoflash bombs, and the tail of the bomb is red. Eight rivets are visible around the body at the junction of the red and black parts of the bomb. On removal of the tail dome of a flash bomb, there is no parachute or shackle visible.

Externally, the 4.5-in. Heavy Photoflash Bomb is the same as the ordinary 4.5-in. photoflash. Internally, the construction is slightly modified, as the rear diaphragm is mo-ved to a position near the closing dome, consequently increasing the length of the cen-tral tube. A retaining diaphragm is positioned in the body 5½ in. from the front dia-phragm. A cast-iron weight is located between the front and retaining diaphragm, the flash composition being housed between the rear and retaining diaphragms. The fuze is a U.S. Mechanical Time Fuze M111, which has a fuze adapter in order to fit it into Britsh bomb. When it is loaded, the arming wire is fitted through the second hole in the arming pin and passes through the arming vane block. The delay may be from 5 seconds to 93 seconds. The heavy bomb weighs 40 lb.

Figure 87 – 4.5-in. Photoflash Bomb