Chapter 22 - The Electrical System

Question 1

For what kind of things would an aircraft need an electrical system for?

Answer 1

Lights, motors, flaps, radios, gear, instrumentation, etc.

Question 2

Does a typical light aircraft have a DC or an AC electrical system?

Answer 2

DC (direct current)

Question 3

What is a bus bar?

Answer 3

A distribution centre for the electrical system

Question 4

What type of battery is normally fitted to a light aircraft?

Answer 4

Lead-acid

Question 5

What is the typical voltage of a light aircraft battery?

Answer 5

12 or 24 volts

Question 6

What does a light aircraft battery typically supply power for?

Answer 6

Engine start and emergency situations

Question 7

If you connect two 12V 60AMP-hour batteries IN SERIES, what is the resultant voltage and amp hours?

Answer 7

24 Volts, 60 AMP-hours

Question 8

If you connect two 12V 60AMP-hour batteries IN PARALLEL, what is the resultant voltage and amp hours?

Answer 8

12 Volts, 120 AMP-hours

Question 9

What supplies electrical power to the aircraft during normal flight?

Answer 9

The alternator

Question 10

How is the alternator driven?

Answer 10

Belt-driven by the engine

Question 11

What is a generator?

Answer 11

A self sufficient, electricity-generating device with it’s own permanent electrical field

Question 12

Does a generator supply DC or AC power?

Answer 12

AC power

Question 13

Does an alternator supply DC or AC power?

Answer 13

AC power

Question 14

What device converts AC power into DC power?

Answer 14

A rectifier (transfer rectifier unit-TRU-)

Question 15

What are the advantages of using an alternator over a generator?

Answer 15

• Lighter
• Produce a more constant voltage
• Easier and cheaper to maintain

Question 16

What is the main disadvantage of an alternator?

Answer 16

An alternator requieres an initial ‘excitement’ to function, it can’t start itself. We use the battery to provide this initial excitement

Question 17

What does the ammeter tell the pilot?

Answer 17

If electricity is flowing TO or FROM the charging unit (positive means battery is gaining energy-being charged-negative means the battery is losing energy)

Question 18

What is the typical reading of the ammeter when the master is ON but the engine is not running?

Answer 18

A negative indication (battery being depleated

Question 19

What is the typical reading of the ammeter after the engine has been started and the alternator has been connected?

Answer 19

A positive indication (battery charging)

Question 20

What does the master switch do?

Answer 20

Basically, switches the battery on

Question 21

What is the difference between a fuse and a circuit breaker?

Answer 21

If a fuse burns out, it has to be replaced. A circuit breaker can be reset (pushed back in)