Electrical System

Electrical energy is required to operate navigation and communication radios, lights, id other airplane equipment.

Most airplanes are equipped with a direct-current (DC) electrical system and an alternating-current (AC) electrical system.

A basic airplane electrical system consists ofthe following components:

1. Generator.

2. Battery.

3. Master switch or battery switch.

4. Bus bar, fuses, and circuit breakers.

5. Voltage regulator.

6. Ammeter.

7. Starting motor.

8. Associated electrical wiring.

10. Accessories.

Engine-driven generators or alternators у electric current to the electrical system and also maintain a sufficient electrical charge inthe battery which is used primarily for starting.

Electrical energy stored in a battery provides a source of electricity for starting the engine and a limited supply of electricity for use in the event the generator fails.

Some airplanes are equipped with re­ceptacles to which external auxiliary power units (APU) can be connected to provide electrical energy for starting. These are very useful, especially during cold weather start­ing. Care must be exercised in starting engines using auxiliary power units when thebattery is dead. If this is done, electrical en­ergy will be forced into the dead battery, causing the battery to overheat and possibly explode, resulting in damage to the airplane.

A master switch is installed on air­planes to provide a means for the pilot to turn the electrical system "on" and "off." Turning the master switch "on" provides electrical energy to all the electrical equip­ment circuits with the exception of the ignition system.

Although additional electrical equipment may be found in some airplanes, the following lists the equipment most commonly found which uses the electrical system for its source of energy:

1. Position lights.

2. Landing lights.

3. Taxi lights.

4. Anticollision lights.

5. Interior cabin lights.

6. Instrument lights.

7. Radio equipment.

8. Turn indicator.

9. Fuel gauges.

10. Stall warning system.

11. Pitot heat.

Some airplanes are equipped with a bat­tery switch which controls the electrical power to the airplane in a manner similar to the mas­ter switch. In addition, a generator switch is installed which permits the pilot to exclude the generator from the electrical system in the event of generator failure. With the generator switch "off," the entire electrical load is placed on the battery. Therefore, all nonessential elec­trical equipment should be turned off to con­serve the energy stored in the battery.

A bus bar is used as a terminal in the air­plane electrical system to connect the main elec­trical system to the equipment using electricity as a source of power. This simplifies the wiring sys­tem and provides a common point from which voltage can be distributed throughout the system.

Fuses or circuit breakers are used in the electrical system to protect the circuits and equipment from electrical overload. Circuit breakers have the same function as a fuse but can be manually reset, rather than replaced, if an overload condition occurs in the electrical sys­tem.

An ammeter is an instrument used to monitor the performance of the airplane electri­cal system.

An ammeter shows if the generator is producing an adequate supply of electrical power to the system by measuring the amperes of electricity. This instrument also indicates whether the battery is receiving an electrical charge.

1. What is electrical energy required for?

2. What are the basic electrical system components?

3. Does electrical system remain operative in case of generator failure?

4. Describe the purpose of circuit breakers.

5. What is the function of a voltage regulator?