Powerplant V FINAL EXAM

Mod 1,2 and 3

Wire is manufactured in sizes according to a standard known as.....

the American Wire Gauge (AWG).

Which of the following is most correct?

The wire diameters become smaller as the gauge numbers become larger.

Which of the following are three factors affecting the selection of wire size in aircraft electrical installations?

Power Loss (PR loss) Voltage drop (IR drop) Current carrying ability of the conductor

For aviation, the two most generally used conductors are...

Copper and aluminum

A resistance measurement of ____________ ohms from ground point of the generator or battery to ground terminal of any electrical device is considered satisfactory.

.005

The voltage drop in the main power cables from the aircraft generation source or the battery to the bus should not exceed 2 percent of the regulated voltage when the generator is carrying rated  current or the battery is being discharged at a 5-minute rate.

1 Volt

Common insulation materials used extensively in aviation today are materials such as...

vinyl, cotton, nylon, Teflon, and Rockbestos.

A combination of letters and numbers that identify the wire, the circuit it belongs to, the gauge number, and other information necessary to relate the wire or cable to a wiring diagram is known as the _______________________________________.

Identification code

What is the standard procedure for marking and identifying wiring?

There is no standard procedure for marking and identifying wiring

Wires, generally from generators to main bus distribution points, that do not have protection, such as fuses, circuit breakers, or other current-limiting devices are known as... 

Electrically unprotected wiring

Slack between supports in single wires or wire bundles should normally not exceed...

1/2". However, this may be exceeded if the wire bundle is thin and the clamps are far apart.

All wires and wire groups should be routed and installed to protect them from:

Choose all that apply.

all the above except Ease of maintenance

Wire should never be routed below a/an...

Battery

All wires in the vicinity of a battery should be inspected...

frequently

When wiring must be routed parallel to combustible fluid or oxygen lines for short distances, as much separation as possible should be maintained. The wires should be on a level with, or _____________, the plumbing lines.

Above

T or F:

Tying wire bundles is the securing together of a group or bundle of wires by a continuous piece of cord forming loops at regular intervals around the group or bundle.

False

All wire groups or bundles should be tied where supports are more than ___________ inches apart.

12

Which type of wire requires extreme care when stripping due to its fragile strands?

Aluminum wire

What is the recommended precaution when using any type of wire stripper?

Hold the wire perpendicular to the cutting blades

What is the purpose of solderless terminal lugs and splices?

To terminate electric wires for easy connection and disconnection

What is the purpose of the self-locking ratchet on a hand crimping tool?

To prevent the tool from opening during crimping

How are wire sizes identified for each terminal lug size?

By using color coding

What are the disadvantages of using aluminum wire in?

1. Bending causes "work hardening", and aluminum oxide forms quickly with exposure to air.

What is the purpose of the inspection hole in aluminum terminal lugs?

To check the depth of wire insertion

What is the purpose of the petrolatum-zinc dust compound used inside the barrel of aluminum terminal lugs?

To remove the oxide film from the aluminum

What concept does this figure illustrate?

Terminal lugs locked against movement in the direction of loosening.

When used for bonding and grounding connections, how are nutplates typically attached to a structure?

Riveting

What two things should be ensured when bonding jumpers carry a substantial amount of ground return current?

Adequate current rating with negligible voltage drop.

Which of the following is not a consideration when selecting hardware used to make bonding or grounding connections?

Hardware manufacturer

When replacing connector assemblies, the _____________________________________ should be used on the half that is “ live” or “hot” after the
connector is disconnected to prevent unintentional grounding.

socket-type insert

What class of connector is used in areas where it is vital that the electric current is not interrupted, even though the connector may be exposed to continuous open flame?

Class K connector

Code _________ and ____________ are marked on the coupling ring or shell to identify a connector. This code provides all the information necessary to obtain the correct replacement for a defective or damaged part. [Figure 4-123]

Letters and numbers

What is the purpose of conduit in aircraft installations?

To provide mechanical protection for wires and cables

(The following sentence is taken from the 8083-32B)

Many of the common conduit installation problems can be avoided by proper attention to the following details.

Question: Which of the following is not a means of proper attention to detail when installing conduit?

Use extra support clamps when installing in areas where conduit might be used as a handhold or a foot step.

When is it necessary to check wires, cables, and circuit-protection devices, such as fuses or circuit breakers, to determine that the electrical load does not exceed the rated limits.

Before any aircraft electrical load is increased.

What is the purpose of placards in an aircraft electrical system?

To inform crewmembers about safe combinations of loads

What is the purpose of circuit protection devices in an aircraft electrical system?

To protect conductors from damage

What is the appropriate derating factor for a 24 VDC motor circuit?

Derating Factor-3

What is the appropriate derating for a switch in a 12 VDC inductive circuit?

Derating Factor -2

What is the appropriate derating for switches in 24 VDC high rush-in circuits?

Derating Factor -8

According to AMT Handbook - Powerplant (FAA-H-8083-32B), What are two reasons for using relays as switching devices?

Weight reduction, and simplifying controls

What is the meaning of the acronym, "EMF"?

Voltage

As a magnetic field moves in relation to a conductor  a __________ will be generated.

Voltage

The armature is the rotating portion of a DC generator. As shown, the voltage being induced is ____________. [Figure 9-40] 

Choose the best answer to fill in the blank.

AC or alternating current

Alternating current is induced into the armature of the generator but is changed to DC by the _______________.

Commutator

What are the three types of DC generators?

• Series wound

• Parallel (shunt) wound

• Series-parallel (compound wound)

Mark all that apply.

The DC Generator...

Choose the incorrect answer from the following.

Brushes should always be changed at 1/2 of the original length.

In a DC alternator, the ________________ rotates and the ___________, (called the stator), is stationary.

Field winding , Armature winding

What is the function of the brushes in an alternator?

Brushes are used to send battery power to the rotating field.

T or F:

The output of a DC alternator is usually 2 phase.

False

Since the three-phase voltage produced by the alternator's armature is AC, it is not compatible with typical DC electrical loads and must be rectified (changed to DC).

How is this accomplished in a DC alternator?

The armature output current is sent through a rectifier assembly comprised of six diodes.

What is a Constant-Speed Drive, (CSD), used for?

A CSD is used to keep the frequency of the AC voltage within 10% of 400-Hz.

T or F:
The DC Alternator has a rotating field winding

True

T or F:

The alternator armature is known as a three phase armature

True

The DC alternator rectifier assembly is comprised of...

Six Diodes

Unlike a DC generator, a set of brushes in a DC alternator must be used to...

Send power to the rotating field.

T or F:

DC alternator output is controlled by varying the field current.

True

Regulators for most DC alternators are either the vibrating relay type or ___________________ regulators

solid-state

Solid-state regulators for modern light aircraft are often referred to as_______________

None of the answers are correct

(ACU)

At that predetermined voltage level, a Zener diode permits current flow with either polarity. This is known as the breakdown or_______________________________ voltage.

Zener

T or F:

AC power systems are normally found on light aircraft.

False

T or F:

An AC alternator produces three phase AC output and is rectified using the same diode circuitry used in a DC alternator.

False

T or F:

The modern AC alternator utilizes brushes and slip rings.

False

A unit called a constant-speed drive (CSD) is used to ensure the alternator rotates at the correct speed to ensure a ________________ frequency.

400-Hz

When the CSD and the alternator are contained within one unit, the assembly is known as a/an _________________

IDG

Matching the items with the correct description.

The basic requirements for reciprocating engine ignition systems are similar, regardless of the type of engine. All ignition systems must deliver...

Mark all that apply.

What are the two classifications for ignition systems used in modern reciprocating engine powered aircraft?

 

Magneto-ignition systems or electronic systems for reciprocating engines

Ignition systems can be subclassified as either single or dual magneto-ignition systems.

What is the difference between the two?

 

Single magnetos consist of two separate magnetos and the necessary wiring. Dual magnetos generally use one rotating magnet that feeds two complete magnetos in one magneto housing.

Which type of magneto-ignition system is still the most widely used in aircraft?

 

High-tension

The high-tension magneto system can be divided, for purposes of discussion, into three distinct circuits.

What are they?

Choose the answer that is the most correct.

 

Magnetic, primary electrical, and secondary electrical circuits.

The magnetic circuit consists of...

 

A permanent multi-pole rotating magnet, a soft iron core, and pole shoes.

What are the components of a primary electrical circuit?

 

A set of breaker contact points, a condenser, and an insulated coil.

The secondary magneto circuit contains... 

 

The secondary windings of the coil, distributor rotor, distributor cap, ignition lead, and spark plug.

What are the two things that the condenser (capacitor) does in the primary circuit?

 

The condenser prevents arcing at the points when the circuit is opened and hastens the collapse of the magnetic field about the primary coil.

What is Lenz's Law and how does it relate to the primary electrical circuit?

 

Lenz's Law states that an induced current always flows in such a direction that its magnetism opposes the motion or change that induced it.

What is the meaning of the term E-gap position? (E stands for efficiency).

 

The rotating magnet is in a position a few degrees past neutral, This position is called the E-gap position (E stands for efficiency).

What are the necessary conditions for firing a spark plug when it's piston is in the prescribed position?

 

The magneto must be in the E-gap position, the breaker points must be open, and the distributor must be aligned correctly.

What is the purpose of a breaker cam in a magneto?

 

To open and close the breaker points

What is a cam follower and what does it do?

 

A Micarta block or similar material that rides on the cam and allows the cam to force the breaker points to separate.

On what type of engine would you find a "Compensated Cam"?

 

A large radial engine

The cam lobes of a compensated cam are machine ground at unequal intervals to compensate for the elliptical path of the...

 

Articulated connecting rods.

What is the purpose of the distributor rotor in a secondary electrical circuit?

 

To direct high-voltage to the spark plugs

How Fast does the distributer rotate in relation to the crankshaft in all four-stroke cycle engines?

 

One-half crankshaft speed

What situations increase the possibility for flashover in a magneto?

Mark all that apply.

T or F:

Ignition leads direct the electrical energy from the sparkplug to the magneto.

False

What is the purpose of the ignition switch in an aircraft ignition system?

 

To control all units in an aircraft ignition system.

How many ways are there to complete the primary circuit in an aircraft ignition system?

Two

What is the main difference between a Single Magneto and a Dual Magneto?

 

Dual Magnetos share a single rotating magnet and cam.

What is the main disadvantage of using a base-mounted magneto?

 

Limited range for timing adjustments.

Choose items from the list that best describe a high tension magneto system.

Mark all that apply

Has problems with flashover at high altitude.

Primary and secondary coils are contained in the magneto case.

Uses harness leads that carry high tension voltage from the magneto to the sparkplug.

Are more widely used in modern aircraft.

Ignition wires enclosed in shielding.

What is the function of a spark plug in an ignition system?

 

Provides an air gap for the high-voltage spark to ignite the air-fuel charge

What are the three main components of a sparkplug?

 

Electrode, insulator, and outer shell

What is meant by the term," all-weather plug"?

 

The seal between the lead and the spark plug is water proof

What is the purpose of the insulator in a spark plug?

 

To provide a protective core around the electrode

Which material is used to make the insulator in a spark plug?

 

Aluminum oxide ceramic

What three positive attributes are provided by the aluminum oxide insulator?

 

Dielectric strength, high mechanical strength, and thermal conductivity

What are three advantages of using a spark plug with a fine wire electrode?

 

Fine wire electrodes have a longer service life, allow for a larger spark gap, and increased performance