CHAPTER 7 AIRCRAFT AVIONICS INTRODUCTION Modern   naval   aircraft   have   a   wide   variety   of missions. The electronic equipment these aircraft carry enables them to perform these missions. We refer to this equipment    as    aviation    electronics    (avionics).    The purpose  of  this  chapter  is  to  familiarize  you  with  the most widely used avionics in the Navy. Aircraft   have   two   primary   sources   of   electrical energy.   The   first   is   the   generator,   which   converts mechanical energy into electrical energy. The second is the    battery,    which    converts    chemical    energy    into electrical energy. The generator is the main source and the    battery    is    the    auxiliary    source.    The    Aviation Electrician's    Mate    (AE)    rating    maintains    aircraft electrical systems. AIRCRAFT STORAGE BATTERIES LEARNING OBJECTIVE: Identify the basic operating principles and safety precautions for working around aircraft batteries. The   aircraft   storage   battery   provides   a   reserve source    of    electrical    power    for    selected    electrical systems. During normal aircraft operation, the generator maintains the battery in a charged state. Batteries can be dangerous; therefore, you need to use extreme care when working around them. Maintain the   batteries   in   perfect   condition.   Batteries   are   the emergency power source for the aircraft. Do not use the batteries for starting engines or servicing equipment if another   source   of   power   is   available.   Unnecessary usage  will  shorten  the  battery  life  and  decrease  the power available for emergency operation. Batteries also require  a  great  deal  of  care  because  of  the  unusual conditions    under    which    they    operate.    Therefore, batteries  are  usually  shielded  by  enclosing  them  in  a grounded,  metal-covered  housing,  as  shown  in  figure 7-1. Most    aircraft    batteries    use    a    quick-disconnect receptacle and plug, as shown in figure 7-1. This unit is a  heavy-duty  connector  with  a  handle  attached  to  a threaded  post.  You  can  disconnect  the  battery  cables from the battery posts simply by turning the handle and pulling the quick-disconnect unit. LEAD-ACID BATTERY Fundamentally, there is no difference between the lead-acid aircraft battery and the lead-acid automobile battery. Both have lead plates in a solution of sulfuric acid and water (electrolyte). Both operate on the same basic principles. The lead-acid battery consists of cells connected in series. Each cell contains positive plates of lead peroxide and negative plates of spongy lead. NICKEL-CADMIUM BATTERY The nickel-cadmium battery gets its name from the composition of its plates: nickel oxide on the positive plate and metallic cadmium on the negative plates. The electrolyte consists of potassium hydroxide and water. The  fundamental  unit  of  the  nickel-cadmium  aircraft storage battery is the cell. The sintered-plate 7-1 1 3 2 7 9 12 8 10 11 13 14 4 6 5 ANF0701 1.     Metal cover 2.     Fillercap and vent plug 3.     Cell connectors 4.     Metal container 5.     Vent 6.     Quick-disconnect receptacle and plug 7.     Vent 8.     Cell container 9.     Positive plate group strap 10.    Plate 11.     Plate supports 12.    Negative plate group strap 13.    Separators 14.    Cells Figure 7-1.—Typical aircraft lead-acid storage battery.