Text 1. Aircraft Electrical System

ELECTRICAL SYSTEM

Exercise 1. Memorize the active vocabulary to text 1:

Electrical current – электрический ток

direct current (DC) – постоянный ток

alternating current (AC) – переменный ток

alternator – генератор переменного тока

master switch – главный выключатель

bus bar - электрошина

fuses - предохранитель

circuit breakers - автоматическая защита сети (АЗС)

voltage regulator - регулятор напряжения

ammeter - амперметр

electrical wiring - электропроводка

to supply - снабжать

engine rpm ()

ground power unit (GPU) источник наземного питания

receptacle – штепсельный разъем аэродромного питания (ШРАП)

ignition system – система зажигания

Exercise 2. Read and translate text 1:

Text 1. Aircraft Electrical System

Most aircraft are equipped with either a 14- or a 28-volt direct current electrical system. A basic aircraft electrical system consists of the following components:
- Alternator/generator

- Battery

- Master/battery switch

- Alternator/generator switch

- Bus bar, fuses, and circuit breakers

- Voltage regulator

- Ammeter/loadmeter

- Associated electrical wiring

Engine-driven alternators or generators supply electric current to the electrical system. They also maintain a sufficient electrical charge in the battery. Electrical energy stored in a battery provides a source of electrical power for starting the engine and a limited supply of electrical power for use in the event the alternator or generator fails.

Most direct-current generators will not produce a sufficient amount of electrical current at low engine rpm to operate the entire electrical system. During operations at low engine rpm, the electrical needs must be drawn from the battery, which can quickly be depleted.

Alternators have several advantages over generators. Alternators produce sufficient current to operate the entire electrical system, even at slower engine speeds, by producing alternating current, which is converted to direct current. The electrical output of an alternator is more constant throughout a wide range of engine speeds.

Some aircraft have receptacles to which an external ground power unit (GPU) may be connected to provide electrical energy for starting. These are very useful, especially during cold weather starting. Follow the manufacturer’s recommendations for engine starting using a GPU.

The electrical system is turned on or off with a master switch. Turning the master switch to the ON position provides electrical energy to all the electrical equipment circuits except the ignition system. Equipment that commonly uses the electrical system for its source of energy includes:

- Position lights

- Anticollision lights

- Landing lights

- Taxi lights

-Interior cabin lights

-Instrument lights

-Radio equipment

-Turn indicator

-Fuel gauges

-Electric fuel pump

-Stall warning system

-Pitot heat

-Starting motor

Many aircraft are equipped with a battery switch that controls the electrical power to the aircraft in a manner similar to the master switch. In addition, an alternator switch is installed which permits the pilot to exclude the alternator from the electrical system in the event of alternator failure.

With the alternator half of the switch in the OFF position, the entire electrical load is placed on the battery. All nonessential electrical equipment should be turned off to conserve battery power.

Exercise 3. Answer the question on text 1:

1. What current electrical system are most aircrafts equipped with?

2. What basic elements does the electrical system consist of?

3. Where does the electrical current occur?

4. What is the battery serve for?

5. What will supply the electric power in the case of alternator or generator failure?

6. Will be the amount of electrical current sufficient at low engine rpm?

7. What is considered to be better generator or alternator?

8. What advantage has the alternator?

9. What is the function of receptacles?

10. When is the use of receptacles preferable?

11. What is master switch used for?

12. What equipment needs the electrical system sources?

13. What is the function of battery switch?

14. By means of what the pilot can exclude the alternator in event of failure?

15. What is happened when the alternator half of switch in the OFF position?

Exercise 4. Match the definition and the term:

Circuit	a) a type of electrical current, in which the direction of the flow of electrons switches back and forth at regular intervals or cycles.
Generator	b) an electrical machine that generates an alternating current
Direct current	c) electromotive force or potential difference, usually expressed in volts
Alternating current	d) a flexible metallic conductor used to carry electric current in a circuit
Voltage	e) a complete path through which an electric current can flow
Alternator	f) a device containing an electric cell or a series of electric cells storing energy that can be converted into electrical power (usually in the form of direct current)
Wire	g) any device for converting mechanical energy into electrical energy by electromagnetic induction
Battery	h) a type of electrical current which flows consistently in one direction.

Exercise 5. Translate word combinations with the term “electrical”:

Electrical current, electrical sours, electrical force, electrical hazard, electrical safety, electrical power, electrical energy, electrical circuit, electrical relay, electrical battery, electrical heating, electrical grounding, electrical equipment, electrical power unit, electrical measuring instrument

Exercise 6. Find the equivalents to the following word combinations

Position lights, anticollision lights, landing lights, taxi lights, interior cabin lights, instrument lights, radio equipment, turn indicator, fuel gauges, electric fuel pump, stall warning system, pitot heat, starting motor

Exercise 7. Translate the following words used both as verbs and nouns and use them in own sentences (10 sentences):

(To) flow, (to) permit, (to) start, (to) store, (to) limit.

Exercise 8. Use the correct from of the verb to be.

1. Aircraft _____ equipped with electrical system. 2. The alternator must _____ switched off in the event of failure. 3. AC and DC _____ different kinds of electrical current. 4. Airplane may _____ connected to GPU. 5. Electrical current produced by generator will _____ (not) sufficient to operate electrical system. 6. Different lights, instruments and equipment _____ supplied by electrical system. 7. The electrical system _____ turned on and off with master switch.

Exercise 9. Change the following sentences from the Active Voice into the Passive Voice according to the model.

Model: - Fire detectors detect fire or overheat. - Fire or overheat is detected by fire detectors.

1. Alternator supplies electric current to electrical system. 2. Master switch turns electrical system on and off. 3. Manufacturers equip the airplane with receptacles. 4. The pilot excludes the alternator in the event of failure. 5. Battery provides a source of electrical power for starting the engine. 6. It limits supply of electrical power. 7. Electrical needs quickly deplete the battery. 8. Equipment use the electrical system for its source. 9. To start during cold weather the pilot uses GPU. 10. To conserve the battery power pilot may switch off all nonessential electrical equipment.

Exercise 10. Complete the following sentences.

Exercise 1. Make sure you remember the terms in fig. Write out new terms and memorize them

Exercise 18. Read and translate text 2:

Text 2

A bus bar is used as a terminal in the aircraft 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. Spare fuses of the proper amperage limit should be carried in the aircraft to replace defective or blown fuses. 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. Placards at the fuse or circuit breaker panel identify the circuit by name and show the amperage limit.

An ammeter is used to monitor the performance of the aircraft electrical system. The ammeter shows if the alternator/generator is producing an adequate supply of electrical power. It also indicates whether or not the battery is receiving an electrical charge.

Ammeters are designed with the zero point in the center of the face and a negative or positive indication on either side. [Figure 6-35] When the pointer of the ammeter is on the plus side, it shows the charging rate of the battery. A minus indication means more current is being drawn from the battery than is being replaced. A full-scale minus deflection indicates a malfunction of the alternator/generator. A full-scale positive deflection indicates a malfunction of the regulator. In either case, consult the AFM or POH for appropriate action to be taken.

Not all aircraft are equipped with an ammeter. Some have a warning light that, when lighted, indicates a discharge in the system as a generator/alternator malfunction. Refer to the AFM or POH for appropriate action to be taken.

A voltage regulator controls the rate of charge to the battery by stabilizing the generator or alternator electrical output. The generator/alternator voltage output should be higher than the battery voltage. For example, a 12-volt battery would be fed by a generator/alternator system of approximately 14 volts. The difference in voltage keeps the battery charged.