Subject J- Engine Electrical Sysytems

Question 1

How would you seat newly installed generator brushes to the commutator?

Answer 1

When new brushes are installed in a generator the face of the brushes must be shaped to provide an area of maximum contact with the commutator. To seat the brushes, use fine grain sandpaper placed around the commutator with the sanding surface facing outward. Turn the armature in a normal direction of rotation until the face of the brushes is properly contoured. Remove the sandpaper and blow out any residue with compressed air.

Question 2

When is is necessary to replace the brushes in a starter?

Answer 2

Once they reach half their original length.

Question 3

Where is the generator rating and performance data located?

Answer 3

On the data plate attached to the generator.

Question 4

What units make up a DC generator three unit regulator?

Answer 4

The voltage regulator, current limiter, and reverse current cutout.

Question 5

What method is used to control the voltage of an aircraft alternator?

Answer 5

The voltage regulator

Question 6

What determines the frequency of the voltage of an alternator?

Answer 6

The frequency depends upon the speed of rotation of the rotor and the number of poles.

Question 7

How is alternator frequency maintained?

Answer 7

Bu installing a constant speed drive unit between the. engine and the alternator.

Question 8

What are three basic types of DC motors?

Answer 8

Series motors, shunt motors, and compound motors.

Question 9

Name the parts of a DC motor?

Answer 9

The armature, brushes, commutator, and field frame.

Question 10

Whys is a starter-generator system, used on many turbine engines?

Answer 10

To save space and weight.

Question 11

Why should stranded wire be used in powerplant applications?

Answer 11

It is less likely to fatigue and break from vibrations.

Question 12

What is the American wire gauge system of designating electrical wire size?

Answer 12

A gauge number is assigned to the wire according to its cross-sectional area. The smaller the gauge number the larger the wire.

Question 13

What is open wiring?

Answer 13

Any wire, wire group, or wire bundle not enclosed in a conduit.

Question 14

What methods are used to control the voltage output of DC aircraft generator?

Answer 14

The vibrating type voltage regulator, three-unit regulator, and carbon pile. The only practical means of regulating voltage is controlling the strength of the magnetic field.

Question 15

What aircraft electrical system normally doesn’t have a fuse or circuit breaker?

Answer 15

The starter circuit.

Question 16

Why are protective covers places on some electrical switches.

Answer 16

To prevent the switch from accidentally being actuated.

Question 17

What are the causes of excessive arcing at the generator brushes?

Answer 17

Arcing can be caused by a commutator that is dirty, rough, or out of roundness. A common cause of arcing is worn binding brushes, or when a brush spring tension is too low.

Question 18

When installing single wires or wire bundles, how much slack is normally allowed between supports?

Answer 18

slack between supports should normally not exceed 1/2 inch.

Question 19

What precaution should be taken when running wires close to heating ducts or exhuast stacks?

Answer 19

The wires should be insulated with a high temperature resistant material.