Guide to aircraft electrical system

Aircraft electrical system performance

The satisfactory performance of any modern aircraft depends to a very great degree on the continuing reliability of electrical systems and subsystems. Improperly or carelessly installed or maintained wiring can be a source of both immediate and potential danger.

The continued proper performance of electrical systems depends on the knowledge and technique of the mechanic who installs, inspects, and maintains the electrical system wires and cables.

Aircraft Batteries

Aircraft batteries are used for many functions (e.g., ground power, emergency power, improving DC bus stability, and fault clearing). Most small private aircraft use lead acid batteries. Most commercial and corporate aircraft use nickel-cadmium (NiCd) batteries.

However, other lead acid types of batteries are becoming available, such as the valve-regulated lead acid (VRLA) batteries.

The battery best suited for a particular application depends on the relative importance of several characteristics, such as weight, cost, volume, service or shelf life, discharge rate, maintenance, and charging rate. Any change of battery type may be considered a major alteration.

Valve-Regulated Lead-Acid Batteries (VRLA) contain all electrolyte absorbed in glass-mat separators with no free electrolyte and are sometimes referred to as sealed batteries.

The electrochemical reactions for VRLA batteries are the same as flooded batteries, except for the gas recombination mechanism that is predominant in VRLA batteries. These types of battery are used in general aviation and turbine powered aircraft and are sometimes authorized replacements for NiCd batteries.