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.