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