Chapter 7 Section D FAA Questions

7-97 AMA039

An electric motor used to raise and lower a landing gear would most likely be a

A— split field series wound motor.

B— shunt field series wound motor.

C— split field shunt wound motor.

7-97. Answer A. JSAT 7D, FGH

Because a motor to operate the landing gear needs to be able to reverse its direction of rotation, a split field series wound motor would be used. By using a single-pole, double-throw switch, it is possible to change the direction of current flow through the motor, and thereby change the direction of rotation.

7-98 AMA039

Some electric motors have two sets of field windings wound in opposite directions so that the

A— speed of the motor can be more closely controlled.

B— motor can be operated in either direction.

C— power output of the motor can be more closely controlled.

7-98. Answer B. JSAT 7D, FGH

One method for reversing the direction of rotation of electric motors is to employ two field windings wound in opposite directions on the same pole. A single-pole, double-throw switch makes it possible to direct current through either of the two windings.

7-99 AMA039

What is the principal advantage of the series wound DC motor?

A— Suitable for constant speed use.

B— High starting torque.

C— Low starting torque.

7-99. Answer B. JSAT 7D, FGH

If high starting torque is needed under heavy load conditions, the series wound motor is the best one to use.

7-100 AMA039

The starting current of a series wound DC motor, in passing through both the field and armature windings, produces a

A— low starting torque.

B— speed slightly higher when unloaded.

C— high starting torque.

7-100. Answer C. JSAT 7D, FGH

Because of the low resistance in the windings, the series motor is able to draw a large current in starting. This starting current, in passing through the field and armature windings, produces a high starting torque.

7-101 AMA039

Which motor would be most likely to have an armature brake?

A— Inverter drive motor.

B— Starter motor.

C— Landing light retraction motor.

7-101. Answer C. JSAT 7D

When a motor needs to have a precise point at which it will stop, an armature brake is utilized. A landing light retraction motor is an application where a precise stopping point is needed.

7-102 AMA039

How does the magnetic brake used to stop rotation of an electric motor armature operate?

A— A friction brake is applied by a spring and released by a magnet.

B— A friction brake is applied by a magnet and released by a spring.

C— Centrifugal force releases a rotating brake cog from a stationary notch when the armature reaches a certain speed and magnetic force reengages the cog when the electrical power is turned off.

7-102. Answer A. JSAT 7D

An armature magnetic brake consists of a drum mounted on the armature shaft and internal brake shoes, controlled by a magnetizing coil. The coil is placed inside the brake shoes, and when the motor current is turned off, the coil is de-energized and the brake shoes are forced against the drum by spring pressure. Conversely, when the power is turned on, the coil pulls the brake shoes away from the drum.

7-103 AMA039

A series wound DC electric motor will normally require

A— more current at high RPM than at low RPM.

B— approximately the same current throughout its operating range of speed.

C— more current at low RPM than at high RPM.

7-103. Answer C. JSAT 7D, FGH

The load on a series wound motor is highest when the motor is at low RPM. The high load at low RPM causes a high current flow.

7-104 AMA009

What is the color and orientation of the position lights for navigation on civil airplanes?

A— Left side - white, right side - green, rear aft - red.

B— Left side - red, right side - green, rear aft - white.

C— Left side - green, right side - red, rear aft - white.

7-104. Answer B. JSAT 7D, FAH

Navigation lights for civil airplanes are located on the forward tip of the left and right wing tips, and on the tail. The left wing has a red light, the right wing a green light, and the tail a white light

7-105 AMA041

When handling a high voltage capacitor in an electrical circuit, be sure it

A— is fully discharged before removing it from the circuit.

B— has at least a residual charge before removing it from the circuit.

C— has a full charge before removing it from the circuit.

7-105. Answer A. JSGT 3G

Capacitors store electricity in an electrostatic field. Large capacitors are capable of storing a charge large enough to injure or kill a person. They should be fully discharged prior to maintenance operations on these systems

7-106 AMA042

How can it be determined if a transformer winding has some of its turns shorted together?

A— The output voltage will be high.

B— The transformer will get hot in normal operation.

C— Measure the input voltage with an ohmmeter.

7-106. Answer B. JSGT 3G

It is often difficult to find a shorted transformer winding by measuring its resistance. It is easier to determine whether or not any coils are shorted by feeling the transformer after it has been operating for a while. If any of the windings are shorted, the transformer will be hot.

7-107 AMA039

Which of the following are the major parts of a DC motor?

1. Armature assembly.

2. Field assembly.

3. Brush assembly.

4. Commutator.

5. Pole piece.

6. Rheostat.

7. End frame.

A— 2, 3, 4, and 5.

B— 3, 5, 6, and 7.

C— 1, 2, 3, and 7.

7-107. Answer C. JSAT 7D, FGH

The major parts in a practical motor are the armature assembly, field assembly, brush assembly and end frame.

7-108 AMA039

1. There are three basic types of DC motors; series, shunt, and compound.

2. In the series motor, the field windings, consisting of relatively few turns of heavy wire, are connected in series with the armature winding.

Regarding the above statements,

A— only No. 2 is true.

B— both No. 1 and No. 2 are true.

C— only No. 1 is true.

7-108. Answer B. JSAT 7D, FGH

The three basic types of DC motors are series motors, shunt motors, and compound motors. The basic series motor has field windings consisting of a relatively few turns of heavy wire, connected in series with the armature winding.

7-109 AMA041

Aircraft fuse capacity is rated in

A— volts.

B— amperes.

C— ohms.

7-109. Answer B. JSAT 7D, FGH

Fuses are designed to break the connection to a circuit if the current flow is too great. For this reason, fuse capacity is rated in amps.

7-110 AMA015

When adding a rheostat to a light circuit to control the light intensity, it should be connected in

A— parallel with the light.

B— series parallel with the light switch.

C— series with the light.

7-110. Answer C. JSGT 3A, FGH

A rheostat is a variable resistor used to vary the amount of current flowing in a circuit. In order to control brightness of a light, it would need to be connected in series with the light.

7-111 AMA041

Circuits that must be operated only in an emergency or whose inadvertent activation could endanger a system frequently employ

A— guarded switches.

B— push-pull-type circuit breakers only (no switches).

C— spring-loaded to off toggle or rocker switches.

7-111. Answer A. JSAT 7D, AC 43.13-1B, FAH

One way to prevent a switch from being accidentally turned on or off is to install a guard over it. This forces the operator to move the guard before being able to turn the switch on or off, which would ensure that it is not done accidentally.

7-112 AMA009

If one switch is used to control all navigation lights, the lights are most likely connected

A— parallel to each other and in series with the switch.

B— in series with each other and in series with the switch.

C— in series with each other and parallel to the switch.

7-112. Answer A. JSAT 7D, FAH

Lights in a circuit are connected parallel to each other, so if voltage available to each light will be the same. If one switch is going to control all the lights in the circuit, the switch will need to be in series with the parallel circuit of the lights.

7-113 AMA041

The nominal rating of electrical switches refers to continuous

A— current rating with the contacts closed.

B— current rating with the contacts open.

C— voltage rating with the contacts closed.

7-113. Answer A. JSAT 7D, AC 43.13-1B, FAH

The nominal current rating of the conventional aircraft switch is usually stamped on the switch housing and represents the continuous current rating with the contacts closed.

Section D — Electrical System Components

7-114 AMA009

The navigation lights of some aircraft consist of a single circuit controlled by a single switch which has an ON position and an OFF position, with no additional positions possible. This switch is referred to as a

A— single pole, single throw (SPST), two position switch.

B— double pole, single throw (DPST), two position switch.

C— single pole, double throw (SPDT), two position switch.

7-114. Answer A. JSAT 7D, FGH

Electric switches which control a single circuit, and have only an ON and an OFF position, are referred to as single-pole, single-throw, two-position switches. Single-pole means that the switch has only one pole or circuit energized when it is moved to the ON position. Single-throw means that from any position, the switch has only one throw or change of position available to it. Two-position means that the switch has two stopping points—it is either on or off.

7-115 AMA041

Electric circuits are protected from over-heating by means of

A— thermocouples.

B— shunts.

C— fuses.

7-115. Answer C. JSAT 7D, FGH

Fuses are current sensitive devices. If the current in a circuit becomes too great, the fuse protecting the circuit will be subjected to the excessive current and it will blow. With excessive current comes excessive heat. When a fuse flows, what it actually does is melt because of the heat.

7-116 AMA041

What kind of switch should you install in a single wire circuit that required the switch to be manually held in the ON position?

A— Single pole, single throw (SPST), two position normally open (NO).

B— Single pole, single throw (SPST), single-position.

C— Single pole, double throw (SPDT), single-position normally open (NO).

7-116. Answer A. JSAT 7D, FGH

A switch installed in a single wire circuit that must be held in the ON position would be a single-pole, single-throw, two-position normally open switch. A switch which stays off, except when held in the ON position, is a normally open switch..

7-117 AMA041

A circuit breaker is installed in an aircraft electrical system primarily to protect the

A— circuit and should be located as close to the source as possible.

B— electrical unit in the circuit and should be located as close to the source as possible.

C— circuit and should be located as close to the unit as possible.

7-117. Answer A. JSAT 7D, FAH
Conductors should be protected with circuit breakers or fuses located as close to the electrical power source bus as possible. Normally, the manufacturer of the electrical equipment specifies the fuse or circuit breaker to be used when installing equipment.

7-118 AMA041

A circuit protection device called a current limiter is essentially a slow-blow fuse and is designed to be used in

A— starter-generator circuits.

B— heavy power circuits.

C— 400 cycle AC circuits.

7-118. Answer B. JSAT 7D, AC 43.13-1B

Though a current limiter is often a fuse that is only replaced by maintenance on the ground, it can also be a “slow-blow” fuse that is used in high power circuits and allows momentary overloads.

7-119 AMA041

The three kinds of circuit-protection devices used most commonly in aircraft circuits are

A— circuit breakers, fuses, and current limiters.

B— circuit breakers, resistors, and current limiters.

C— circuit breakers, capacitors, and current limiter plug-ins mechanical reset types.

7-119. Answer A. JSAT 7D, FGH

Circuit breakers, fuses, and a type of fuse for large power circuits (current limiter) are used in aircraft.

7-120 AMA042

What is the purpose of the selection of derated switches for known continuous load current applications?

A— To calculate the voltage drop across the circuit.

B— To prevent short circuits in the motor field windings.

C— To obtain reasonable switch efficiency and service life.

7-120. Answer C. JSAT 7D, FAH

Although a switch might be rated for a continuous current load of 15 amps, if the switch is derated and used in a circuit with a current load of only 10 amps, the switch efficiency and service life will be increased.

7-121 AMA042

What is the advantage of a circuit breaker when compared to a fuse?

A— Always eliminates the need for a switch.

B— Never needs replacing.

C— Resettable and reusable.

7-121. Answer C. JSAT 7D, FGH

When a fuse being used to protect an electrical circuit blows, the fuse must be replaced. A big advantage of using circuit breakers instead of fuses is the breaker's ability to be reset and reused. The circuit breaker is, however, considerably more expensive than the fuse.

7-122 AMA041

What is the advantage of a current limiter?

A— It can be reset easily.

B— It breaks circuit quickly.

C— It will take overload for a short period.

7-122. Answer C. JSAT 7D, FGH

Most fuses have a strip of metal (which is designed to melt at a set temperature) made of a tin alloy and bismuth. Some fuses have a metal strip which is made of copper, and they are referred to as current limiters. Current limiters will stand a considerable overload for a short period of time before they will blow.

7-123 AMA041

In aircraft electrical systems, automatic reset circuit breakers

A— should not be used as circuit protective devices.

B— must be used in all circuits essential to safe operation of the aircraft.

C— are useful where only temporary overloads are normally encountered.

7-123. Answer A. JSAT 7D, AC 43.13-1B

In an aircraft electrical system, automatic reset circuit breakers should not be used. If a fault exists in a circuit which causes a circuit breaker to trip, the fault needs to be identified before the circuit is powered again. To have a circuit breaker which would continue to reset and then trip could cause serious problems.

7-124 AMA041

A certain switch is described as a single pole, double throw switch (SPDT). The throw of a switch indicates the number of

A— circuits each pole can complete through the switch.

B— terminals at which current can enter or leave the switch.

C— places at which the operating device (toggle, plunger, etc.) will come to rest and at the same time open or close a circuit.

7-124. Answer A. JSAT 7D, FGH

When a switch is described as being a double-throw switch, what is being identified is the number of circuits which can be completed through the switch.

7-125 AMA015

The circuit breaker in the instrument lighting system protects the

A— wiring from too much current.

B— wiring from too much voltage.

C— lights from too much current.

7-125. Answer A. JSAT 7D, FGH

Circuit breakers are designed to protect an electrical system from too much current flow. In an instrument lighting system, it is the wiring which is protected from excessive current.

7-126 AMA041

Why are the iron cores of most induction coils laminated?

A— To reduce the effects of eddy currents.

B— To increase the core permeability.

C— To reduce the core reluctance.

7-126. Answer A. JSGT 4C

The primary windings of an induction coil consist of relatively few turns of large wire and will carry sufficient current to set up a strong magnetic field through the soft iron core. The core consists of thin iron laminations or insulated iron wires bound together in the shape and size desired. This type of construction reduces the effects of the eddy currents induced in the core.

7-127 AMA041

The voltage in an AC transformer secondary that contains twice as many loops as the primary will be

A— greater and the amperage less than in the primary.

B— less and the amperage greater than in the primary.

C— greater and the amperage greater than in the primary.

7-127. Answer A. JSGT 3D, FGH

Transformers, whether AC or DC, cannot produce power. Their output power, if they are 100% efficient, will be the same as the input power. Since power is the product of the voltage and the current, if a transformer is stepping up the voltage, it is stepping down the current. A transformer secondary with more loops than the primary steps up the voltage, and steps down the current.

7-128 AMA039

How can the direction of rotation of a DC electric motor be changed?

A— Interchange the wires which connect the motor to the external power source.

B— Reverse the electrical connections to either the field or armature windings.

C— Rotate the positive brush one commutator segment.

7-128. Answer B. JSAT 7D, FGH

The direction a motor will turn is determined by the direction of current flow in either the armature or the field windings. By reversing either of these current flows, the direction of rotation will be reversed.

7-129 AMA009

During inspection of an anticollision light installation for condition and proper operation, it should be determined that

A— electrical or mechanical interconnections are provided so that the anticollision light will operate at all times that the position light switch is in the ON position.

B— an appropriately rated fuse is in position at the light to protect the connecting wiring against electrical faults.

C— the anticollision light can be operated independently of the position lights.

7-129. Answer C. AC 43.13-2A

According to AC 43.13-2A, when an anticollision light is installed, a switch needs to be used which is independent of the position light system switch.

7-130 AMA041

A relay is

A— a magnetically operated switch.

B— any conductor which receives electrical energy and passes it on with little or no resistance.

C— a device which converts electrical energy to kinetic energy.

7-130. Answer A. JSAT 7D, FGH

A relay switch consists of a coil, or solenoid, an iron core, and both fixed and movable contacts. When the solenoid is energized (powered), it creates a magnetic force which pulls the movable contact down until it touches the fixed contact, which completes the circuit.

7-131 AMA041

Microswitches are used primarily as limit switches to

A— prevent overcharging of a battery.

B— control electrical units automatically.

C— limit generator output.

7-131. Answer B. JSAT 7D, FGH

Microswitches are used primarily as limit switches to provide automatic control of electrical units. They are used to limit the movement of a mechanism.

7-132 AMA041

What is the ratio of turns between the primary coil winding and the secondary coil winding of a transformer designed to triple its input voltage?

A— Primary will have twice as many turns as its secondary.

B— Primary will have one third as many turns as its secondary.

C— Primary will have three times as many turns as its secondary.

7-132. Answer B. JSGT 3D, FGH

In a transformer, the ratio between the number of turns in the primary and the voltage in the primary is directly proportional to the ratio between the number of turns in the secondary and voltage in the secondary. If the secondary has three times as much voltage as the primary it will have three times as many turns.