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Chapter 1 Bombs, Fuzes, and Associated Components - 14313_11
M904E2/E3/E4 MECHANICAL IMPACT NOSE FUZE

Aviation Ordinanceman - Aviation theories and other practices
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  Depending upon the type of target, the fuze may be required to delay the detonation of the bomb after impact for a preset time (functioning delay). Functioning delay may vary from a few milliseconds to many hours.   It  should  not  detonate  the  bomb  if  the  bomb  is accidentally released or if the bomb is jettisoned in a safe condition from the aircraft. To  provide  these  qualities,  a  number  of  design features  are  used.  Most  features  are  common  to  all types of fuzes. Electrical Fuzes Electrical   fuzes   have   many   characteristics   of mechanical  fuzes.  They  differ  in  fuze  initiation.  An electrical impulse is used to initiate the electrical fuze rather   than   the   mechanical   action   of   arming   vane rotation. An   electrical   pulse   from   the   delivery   aircraft charges capacitors in the fuze as the bomb is released from  the  aircraft.  Arming  and  functioning  delays  are produced  by  a  series  of  resistor/capacitor  networks  in the fuze. The functioning delay is electromechanically initiated, with the necessary circuits closed by means of shock-sensitive switches. The  electric  bomb  fuze  remains  safe  until  it  is energized  by  the  electrical  charging  system  carried  in the  aircraft.  Because  of  the  interlocks  provided  in  the release  equipment,  electrical  charging  can  occur  only after the bomb is released from the rack or shackle and has begun its separation from the aircraft; however, it is still connected electrically to the aircraft's bomb arming unit.   At   this   time,   the   fuze   receives   an   energizing charge required for selection of the desired arming and impact times. SPECIAL SAFETY FEATURES Some fuzes incorporate special safety features. The most important safety features are detonator safe, shear safe, and delay arming. Detonator  safe  fuzes  do  not  have  the  elements  of their  firing  train  in  the  proper  position  for  firing  until the  fuze  is  fully  armed.  The  elements  remain  firmly fixed and out of alignment in the fuze body while the fuze is unarmed. This increases safety during shipping, stowing, and handling of the fuze. The arming action of the fuze aligns the firing train. A  shear-safe  fuze  does  not  become  armed  if  its arming mechanism is damaged or completely severed from the fuze body. The arming mechanism of the fuze protrudes from the bomb, and it might be severed from the  fuze  body  if  the  bomb  is  accidentally  dropped. Shear-safe  fuzes  give  additional  security  for  carrier operations and for externally mounted bombs. Delay  arming  mechanically  or  electrically  slows the  arming  of  the  fuze.  It  keeps  a  fuze  in  the  safe condition until the bomb falls far enough away from or long enough from the aircraft to minimize the effects of a  premature  explosion.  Delay  arming  helps  to  make carrier  operations  safe  because  a  bomb  accidentally released  during  landing  or  takeoff  ordinarily  will  not have sufficient air travel, velocity, or time to fully arm the fuze. REVIEW NUMBER 1 Q1. Name  the  device  that  controls  bomb detonation. Q2. The time or number of vane revolutions needed for the firing train to align after a bomb is released is the _______. Q3. Describe the functioning time of a fuze. Q4. The distance along the trajectory that a bomb travels   from   the   releasing   aircraft   in   an unarmed condition is the ____________. Q5. List the two basic classes of fuzes. Q6. Describe the basic principle of the mechanical fuze. Q7. What  means  is  used  to  initiate  an  electrical fuze? Q8. List  the  three  special  safety  features  incor- porated into fuzes. MECHANICAL FUZES LEARNING OBJECTIVE: Identify the various  types  of  mechanical  fuzes  to  include their    physical    description    and    functional operation. There  are  many  fuzes  in  use  by  the  Navy  today. Some of the commonly used fuzes are discussed in this TRAMAN. To keep up with current fuzes, you should refer    to    Aircraft    Bombs,    Fuzes,    and    Associated Components, NAVAIR 11-5A-17, and Airborne Bomb and Rocket Fuze Manual, NAVAIR 11-1F-2. 1-2







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