7/31/2019 Aircraft Electrical Systems Card

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1. . How is a wire bundle

protected from

chafing where the

bundle goes through a

hole in a fuselage

frame or bulkhead?

The edges of the hole are covered

with a flexible grommet, and the

bundle is secured to the structure

with a cushioned clamp.

2. Does an aircraft

engine electric starter

use a series or a

parallel motor?

A series-wound motor.

3. How can the direction

of rotation of the

armature of a DC

shunt-wound electric

motor be reversed?

By reversing the connections to the

shunt field coil with reference to the

armature.

4. On which wing is the

red navigation light?

On the left wing.

5. What is meant byflashing the field of a

generator?

Restoring the residual magnetismto the frame of the generator. This

is done by passing battery current

through the field coils in the

direction it normally flows when

the generator is operating

6. What is the main

disadvantage of

aluminum wire over

copper wire for use in

an aircraft electrical

system?

Aluminum wire is more brittle than

copper. It is more subject to

breakage when it is nicked or when

it is subjected to vibration.

7. What is the maximum

number of wires that

should be connected

to any single stud in a

terminal strip?

Four

8. What is the smallest

size aluminum wire

that is approved for

use in aircraft

electrical systems?

Six-gage.

9. What kind of clamp is

used to secure a wirebundle to the aircraft

structure?

A cushioned clamp.

10.What kind of fault can

be found in a

generator armature

with a growler?

Shorted coils.

11.What kind of

instrument would you

use to measure very

high resistance?

A megohmmeter. Megger is the

registered trade name of such an

instrument.

12.What kind of rectifier

is used in the small DC

alternators installed in

most light aircraft?

Six silicon diodes arranged in a

three-phase, full-wave rectifier

13.What size aluminum

wire would be proper

to replace a piece of

four-gage copper wire?

Two-gage. When you substitute

aluminum wire for copper wire,

use a wire that is two gage

numbers larger.

14.What size generator

must be used in an

aircraft electrical

system if the connected

electrical load is 30

amps, and there is no

way of monitoring the

generator output?

When monitoring is not practical,

the total continuously connected

electrical load must be no more

than 80% of the rated generator

output. This would require a

generator with a rating of 37.5

amps. Practically, a 40-amp

generator would be installed.

15.What three things

must be synchronizedbefore an aircraft AC

generator is placed on

the same bus with

another AC generator?

The voltage, the frequency, and

the phase rotation.

16.What two things must

you take into

consideration when

selecting the wire size

to use in an aircraft

electrical system

installation?

The current carrying capability of

the wire and the voltage drop

caused by the current flowing

through the wire.

17.When is it importantthat aircraft electrical

system wire bundles be

enclosed in some type

of conduit?

Any time a wire bundle is routed inan area where it is subject to

abrasion or rough handling, it

should be enclosed in a conduit.

18.Why are solderless

splices usually better

than soldered splices

in the wiring of an

aircraft electrical

system?

Soldered joints are usually stiff,

and vibration can harden the wire

and cause it to break. Solderless

splices are designed to keep the

joint flexible so vibration cannot

cause the wire to break.

19.Why must a switch be

derated if it is used in

a circuit that supplies

incandescent lamps?

The high inrush current caused by

the low resistance of the cold

filaments requires that the

switches be derated.

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