FREE A&P Aircraft Electrical Systems Questions and Answers

Question 1

In a typical aircraft AC electrical system, what is the primary function of a Constant Speed Drive (CSD) unit?

Accepted Answer

To maintain a constant frequency output from the AC generator regardless of engine RPM changes.

Answer

To convert DC power to AC power for the main generator.

Answer

To regulate the voltage output of the generator by controlling the field current.

Answer

To act as a circuit breaker in the event of a generator over-speed condition.

Question 2

A technician is troubleshooting a nickel-cadmium (Ni-Cd) battery that has experienced thermal runaway. Which of the following conditions is a primary contributor to this phenomenon?

Accepted Answer

High charging current combined with high battery temperature.

Answer

Low electrolyte level causing increased internal resistance.

Answer

Excessively low charging voltage from the aircraft's bus.

Answer

A short circuit between two adjacent cells within the battery case.

Question 3

What is the function of a static inverter in an aircraft electrical system?

Accepted Answer

To convert DC power from a battery or DC bus into AC power.

Answer

To convert AC power to DC power for charging the battery.

Answer

To step up DC voltage to a higher DC voltage.

Answer

To rectify the output of the main AC generators.

Question 4

An aircraft's electrical schematic shows several components, including generators, batteries, and various avionics, all connected to a central conductor. What is this primary distribution point called?

Accepted Answer

A bus bar

Answer

A junction box

Answer

A terminal strip

Answer

A relay panel

Question 5

When comparing circuit protection devices in an aircraft, what is a key advantage of a circuit breaker over a fuse?

Accepted Answer

Circuit breakers can be reset after tripping, while a fuse must be replaced.

Answer

Circuit breakers are lighter and less complex than fuses.

Answer

Circuit breakers react faster to overcurrent conditions than fuses.

Answer

Circuit breakers are not susceptible to failure from vibration.

Question 6

During a pre-flight inspection on an aircraft with a DC electrical system, a pilot notices that the ammeter shows a large, momentary positive charge immediately after engine start, which then reduces to a smaller positive value. This indicates:

Accepted Answer

The battery is being properly recharged by the generator after supplying starting power.

Answer

A faulty voltage regulator.

Answer

A short circuit in the battery relay.

Answer

The generator is failing to produce sufficient output.