Introduction

The main explosive charge of aircraft bombs is relatively insensitive. To effect deto-nation, a train of more sensitive explosives is normally used, which may be either of two types: the fuze-exploder-main-charge type, or the pistol detonator-exploder-main-charge type. The distinction between fuzes and pistols, as made in the introduction to Part 2, pointed out that fuzes have the initiating explosive charge in corporated in them, while pistols contain no explosive whatsoever, but merely act as a mechanical device to activate the initiating explosive in a detonator inserted separately in the bomb.

Detonators are of two types, the anvil type employed with pistols having a blunt stri-ker, and the sensitive type employed with pistols having a needle striker. Furthermore, they may be instantaneous in functioning or may have a delay of from 0.025 sec. to 11 sec. for the anvil type, or 0.01 to 25 - 30 sec. for the sensitive type.

The most sensitive explosive in the pistol detonator firing train is usually contained in the percussion cap of the detonator cap, and is fired by impact or friction. The flash from the cap composition fires a less sensitive composition known as the detonating composition, which in turn initiates a still less sensitive explosive called the exploder, whose explosion initiates the main charge. Sensitive-type detonators, however, have no percussion cap or anvil.

Detonators are filled with very sensitive high explosives which will explode if they are subjected to sudden shock or even a light blow or are subjected to heat. It is essential that all detonators be handled with great care. The cap composition usually used in Brit-ish detonators is A.S.A. mixture, composed of lead azide and lead syphnate. Fulminate of mercury is also used. Formerly, C.E. (tetryl) and TNT were used in the exploder, but the use of TNT is being disconected and C.E. alone is now being used.

Bombs employing a pistol-detonator combination are generally shipped with the pistol in place, but without the detonator, which is inserted prior to loading on the plane after first removing the pistol. In small bombs (500 lb. or under), the detonator generally fits into the exploder, whereas in larger bombs it is housed in a detonator holder, which threads into the exploder container and is threaded itself to receive the pistol.