Chapter 1 Bombs, Fuzes, and Associated Components

CHAPTER 1 BOMBS, FUZES, AND ASSOCIATED COMPONENTS 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. FUZE TERMINOLOGY AND BASIC FUZE THEORY LEARNING OBJECTIVE: Describe the operation of mechanical and electrical fuzes. Identify special safety features that are inherent in bomb fuzes. This chapter will introduce you to some of the common terms and acronyms associated with fuzes used in the Navy. Basic fuze theory, general classes of fuzes, and the various types of fuzes are also discussed in this chapter. FUZE TERMINOLOGY Some of the most common fuze terms that you should know are defined as follows: Arming time. The amount of time or vane revolutions needed for the firing train to be aligned after the bomb is released or from time of release until the bomb is fully armed. It is also known as safe separation time (SST). Delay. When the functioning time of a fuze is longer than 0.0005 second. External evidence of arming (EEA). A means by which a fuze is physically determined to be in a safe or armed condition. Functioning time. The time required for a fuze to detonate after impact or a preset time. Instantaneous. When the functioning time of a fuze is 0.0003 second or less. Nondelay. When the functioning time of a fuze is 0.0003 to 0.0005 second. Proximity (VT). The action that causes a fuze to detonate before impact when any substantial object is detected at a predetermined distance from the fuze. Safe air travel (SAT). The distance along the trajectory that a bomb travels from the releasing aircraft in an unarmed condition. BASIC FUZE THEORY Fuzes are normally divided into two general classes—mechanical and electrical. These classes only refer to the primary operating principles. They may be subdivided by their method of functioning or by the action that initiates the explosive train—impact, mechanical time, proximity, hydrostatic, or long delay. Another classification is their position in the bomb—nose, tail, side, or multi-positioned. Mechanical Fuzes In its simplest form, a mechanical fuze is like the hammer and primer used to fire a rifle or pistol. A mechanical force (in this case, the bomb impacting the target) drives a striker into a sensitive detonator. The detonator ignites a train of explosives, eventually firing the main or filler charge. A mechanical bomb fuze is more complicated than the simple hammer and primer. For safe, effective operation, any fuze (mechanical or electrical) must have the following design features: � It must remain safe in stowage, while it is handled in normal movement, and during loading and downloading evolutions. � It must remain safe while being carried aboard the aircraft. � It must remain safe until the bomb is released and is well clear of the delivery aircraft (arming delay or safe separation period). 1-1