2A672 Volume 2 Frequency Converter Components

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| By Chorne1787

Chorne1787

Community Contributor

Quizzes Created: 4 | Total Attempts: 900

Questions: 76 | Attempts: 248 | Updated: Mar 21, 2023

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Volume URE for 2A672 Volume 2

Questions and Answers

1.

During operation of the EPU-6/E frequesncy converter it is determined that E and F pin voltage in not needed for the aircraft. The operator places the Loop/bypass/28 V to aircraft switch to what position?
- A.
  
  28 V to aircraft
- B.
  
  Neutral
- C.
  
  Bypass
- D.
  
  Loop
Correct Answer
C. Bypass

Explanation
During the operation of the EPU-6/E frequency converter, if it is determined that the E and F pin voltage is not needed for the aircraft, the operator should place the Loop/bypass/28 V to aircraft switch in the "Bypass" position.

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2.

Which of the following components provides 525 VAC to the control transformer of the EPU-6/E frequency converter?
- A.
  
  Input auto transformer
- B.
  
  Output auto transformer
- C.
  
  Input phase sequence transformer
- D.
  
  Output phase sequence transformer
Correct Answer
A. Input auto transformer

Explanation
The correct answer is Input auto transformer. The input auto transformer is responsible for providing the required voltage of 525 VAC to the control transformer of the EPU-6/E frequency converter. It is designed to step up or step down the voltage as needed to ensure proper functioning of the control transformer.

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3.

What EPU-6/E components receive potential directly from the input auto transformer?
- A.
  
  Analog board and alarm display
- B.
  
  Control transformer and voltage control
- C.
  
  Input circuit breakers and display power supply
- D.
  
  SCR voltage regulator and phase sequence transformer
Correct Answer
D. SCR voltage regulator and pHase sequence transformer

Explanation
The SCR voltage regulator and phase sequence transformer receive potential directly from the input auto transformer.

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4.

The control transformer perform on the EPU-6/E frequency converter provides
- A.
  
  28 VDC for the aircraft contactor
- B.
  
  240 VDC for the aircraft contactor
- C.
  
  120 VAC for the operation of E and F line 28 VDC power supply
- D.
  
  240 VAC for operation of E and F line 28 VDC power supply
Correct Answer
C. 120 VAC for the operation of E and F line 28 VDC power supply

Explanation
The control transformer on the EPU-6/E frequency converter provides 120 VAC for the operation of the E and F line 28 VDC power supply. This means that the control transformer converts the incoming voltage to 120 VAC, which is then used to power the E and F line 28 VDC power supply. This voltage is necessary for the proper functioning of the power supply, allowing it to provide the required 28 VDC power to the aircraft contactor.

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5.

What EPU-6/E frequency converter components must be inspected prior to use?
- A.
  
  Air inlets for blockage
- B.
  
  Wiring for secure mounting
- C.
  
  Maintenance panels for corrosion
- D.
  
  Interior air vents for secure mounting
Correct Answer
A. Air inlets for blockage

Explanation
Prior to using the EPU-6/E frequency converter, it is important to inspect the air inlets for blockage. This is necessary to ensure that the converter receives proper airflow for cooling. If the air inlets are blocked, it can lead to overheating and potential damage to the converter. Therefore, checking for blockage in the air inlets is crucial before using the EPU-6/E frequency converter.

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6.

During operation you determine that there is an undervoltage fault problem with the EPU-6/E frequency converter unit. What component could be malfunctioning?
- A.
  
  Analog board has failed
- B.
  
  Output trim potentiometer is centered
- C.
  
  Voltage control board potentiometer is shorted
- D.
  
  Audible alarm switch is in the silence position
Correct Answer
A. Analog board has failed

Explanation
The correct answer is that the analog board has failed. This means that the board responsible for converting analog signals into digital signals is not functioning properly. This could be causing the undervoltage fault problem with the EPU-6/E frequency converter unit.

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7.

During operation of the EPU-6/E frequency converter you determine that one phase voltage is lower than the other two phases. What could cause this malfunction?
- A.
  
  Malfunctioning transister
- B.
  
  Burnt control transformer fuse
- C.
  
  Improper SCR firing adjustment
- D.
  
  Loose push-on connector on the output filter capacitor
Correct Answer
D. Loose push-on connector on the output filter capacitor

Explanation
A loose push-on connector on the output filter capacitor could cause one phase voltage to be lower than the other two phases. When the connector is loose, it may not provide a secure connection between the capacitor and the circuit, leading to a decrease in voltage. This can result in an imbalance between the phases, causing one phase voltage to be lower.

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8.

What -95 gas turbine compressor section supplies high-volume, low-pressure air for combustion, cooling, and bleed air output?
- A.
  
  Turbine section
- B.
  
  Accessory section
- C.
  
  Compressor section
- D.
  
  Air regulator section
Correct Answer
C. Compressor section

Explanation
The correct answer is the compressor section. In a gas turbine, the compressor section is responsible for supplying high-volume, low-pressure air for various purposes such as combustion, cooling, and bleed air output. It compresses the incoming air, increasing its pressure before it enters the combustion chamber. This section plays a crucial role in the overall functioning and efficiency of the gas turbine.

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9.

The function of the deswirl ring on the -95 gas turbine compressor is to
- A.
  
  Accelerate air
- B.
  
  Increase air pressure
- C.
  
  Decrease air velocity
- D.
  
  Smooth turbulent air flow
Correct Answer
D. Smooth turbulent air flow

Explanation
The deswirl ring on the -95 gas turbine compressor is designed to smooth turbulent air flow. Turbulent air flow can cause inefficiencies and disruptions in the compressor's operation. The deswirl ring helps to eliminate or reduce turbulence, ensuring that the air flows smoothly through the compressor. This allows for more efficient and effective compression of the air, leading to improved performance and overall operation of the gas turbine.

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10.

What -95 component isolates the second-stage air from the operation of the first-stage compressor?
- A.
  
  Interstage ducts
- B.
  
  Interstage seal
- C.
  
  Impellers
- D.
  
  Inducers
Correct Answer
B. Interstage seal

Explanation
The interstage seal is the component that isolates the second-stage air from the operation of the first-stage compressor. It acts as a barrier between the two stages, preventing any air leakage or mixing between them. This ensures that the second-stage air is not affected by the operation of the first-stage compressor, allowing for efficient and controlled air flow in the system.

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11.

What prevents overpressurization of the bearing cavity on a -95?
- A.
  
  Oil jet
- B.
  
  Oil cooler
- C.
  
  Scavenge pump
- D.
  
  Oil tank vent line
Correct Answer
D. Oil tank vent line

Explanation
The oil tank vent line prevents overpressurization of the bearing cavity on a -95. When the oil heats up and expands, excess pressure can build up inside the bearing cavity. The oil tank vent line allows this pressure to escape, preventing overpressurization and potential damage to the bearings.

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12.

What -95 chambers are pressurized when the butterfly valve is closed?
- A.
  
  1 and 3
- B.
  
  2 and 4
- C.
  
  1, 2, and 3
- D.
  
  1, 3, and 4
Correct Answer
D. 1, 3, and 4

Explanation
When the butterfly valve is closed, chambers 1, 3, and 4 are pressurized. The question is asking which chambers are pressurized in this specific scenario.

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13.

The -95's rate-metering valve prevents the butterfly valve from snapping open by bleeding air through the atmospheric bleed port from chamber
- A.
  
  1
- B.
  
  2
- C.
  
  3
- D.
  
  4
Correct Answer
B. 2

Explanation
The -95's rate-metering valve works by bleeding air through the atmospheric bleed port from the chamber. This prevents the butterfly valve from snapping open suddenly. The rate-metering valve regulates the flow of air, ensuring that it opens slowly and smoothly. This helps to prevent any sudden or abrupt movements of the butterfly valve, which could potentially cause damage or disruption.

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14.

What -95 component closes to complete the electrical circuit to the fuel solenoid and ignition unit?
- A.
  
  Load switch
- B.
  
  Oil pressure switch
- C.
  
  Turbine start switch
- D.
  
  35 percent centrifugal speed switch
Correct Answer
B. Oil pressure switch

Explanation
The oil pressure switch is the component that closes to complete the electrical circuit to the fuel solenoid and ignition unit. This switch is designed to monitor the oil pressure in the engine and when the pressure reaches a certain level, it closes the circuit to allow fuel to flow to the solenoid and ignition unit. This ensures that the engine has sufficient oil pressure before allowing the fuel to ignite, thereby protecting the engine from damage. The other options, such as the load switch, turbine start switch, and centrifugal speed switch, are not directly related to completing the electrical circuit for the fuel solenoid and ignition unit.

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15.

What preliminary set-up step, if skipped, prevents the -95 from starting?
- A.
  
  Set-up controls
- B.
  
  Set parking brakes
- C.
  
  Open and secure the exhaust door
- D.
  
  Ensure the turbine air inlet and exhaust doors are free of obstructions
Correct Answer
C. Open and secure the exhaust door

Explanation
If the exhaust door is not opened and secured, it will prevent the -95 from starting. This is because the exhaust door needs to be open to allow the exhaust gases to escape from the turbine. If the door is closed or not properly secured, it will block the exhaust and prevent the turbine from starting. Therefore, it is crucial to open and secure the exhaust door as a preliminary set-up step before starting the -95.

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16.

On the -95, discharge air pressure at 100 percent engine speed should indicate
- A.
  
  55 +2 psig
- B.
  
  45 +2 psig
- C.
  
  35 +2 psig
- D.
  
  25 +2 psig
Correct Answer
C. 35 +2 psig

Explanation
At -95, discharge air pressure at 100 percent engine speed should indicate 35 +2 psig.

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17.

The -95 does not shut down when the charging rate decreases to 12 amperes. What is the probable cause of this trouble?
- A.
  
  Air load switch
- B.
  
  Fuel level relay K5
- C.
  
  2 speed solenoid SV4
- D.
  
  Battery charging module
Correct Answer
D. Battery charging module

Explanation
The probable cause of the trouble is the battery charging module. This module is responsible for charging the battery, and if it is not functioning properly, the battery may not receive enough charge to stay powered when the charging rate decreases to 12 amperes.

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18.

When heat is applied to an ice cube and the ice starts to melt, it is
- A.
  
  Super heat
- B.
  
  Latent heat
- C.
  
  Sensible heat
- D.
  
  Convection heat
Correct Answer
B. Latent heat

Explanation
When heat is applied to an ice cube and it starts to melt, the process is known as latent heat. Latent heat refers to the heat energy absorbed or released during a phase change, such as the solid ice turning into liquid water. In this case, the heat energy is used to break the bonds between the water molecules in the ice, allowing them to move more freely and transition into a liquid state. Therefore, latent heat is the correct answer in this context.

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19.

The three methods of heat transfer are
- A.
  
  Sensible, latent, and super heat
- B.
  
  Sensible, convection, and conduction
- C.
  
  Conduction, convection, and radiation
- D.
  
  Conduction, convection, and super heat
Correct Answer
C. Conduction, convection, and radiation

Explanation
The correct answer is conduction, convection, and radiation. Conduction is the transfer of heat through direct contact between objects or substances. Convection is the transfer of heat through the movement of a fluid, such as air or water. Radiation is the transfer of heat through electromagnetic waves, without the need for a medium. These three methods of heat transfer are fundamental in understanding how heat moves from one object to another.

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20.

The air flowing through an air conditioner is also called
- A.
  
  Heat
- B.
  
  Heat load
- C.
  
  Pounds per minute (ppm)
- D.
  
  Cubic feet per minute (cfm)
Correct Answer
B. Heat load

Explanation
The air flowing through an air conditioner is referred to as "heat load" because it carries the thermal energy that needs to be removed or transferred by the air conditioner. Heat load represents the amount of heat that the air conditioner needs to handle in order to maintain the desired temperature in a space. It is a measure of the heat energy that is being added or removed from the air as it passes through the air conditioning system.

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21.

While you are doing an ops check of an air conditioner, you notice the unit is short cycling. What do you do to correct this trouble?
- A.
  
  Increase the heat load
- B.
  
  Lower the refrigerant charge
- C.
  
  Check the receiver outlet valve
- D.
  
  Decrease the setting of the LPCO
Correct Answer
C. Check the receiver outlet valve

Explanation
To correct the problem of short cycling in an air conditioner, checking the receiver outlet valve is the appropriate step. The receiver outlet valve regulates the flow of refrigerant from the receiver to the evaporator. If the valve is faulty or not functioning properly, it can cause the unit to short cycle. By checking the receiver outlet valve, any issues or blockages can be identified and resolved, allowing the air conditioner to operate efficiently and prevent short cycling.

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22.

Bubbles in an air conditioner refrigeration system sight glass probably indicate
- A.
  
  Refrigerant overcharge
- B.
  
  A low refrigerant charge
- C.
  
  High discharge temperature
- D.
  
  Low discharge air temperature
Correct Answer
B. A low refrigerant charge

Explanation
Bubbles in an air conditioner refrigeration system sight glass probably indicate a low refrigerant charge. When there is a low refrigerant charge, the system does not have enough refrigerant to properly cool the air. This causes the refrigerant to evaporate quickly, leading to the formation of bubbles in the sight glass.

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23.

What MA-3D air conditioner component controls refrigerant flow into the evaporator?
- A.
  
  Quench valve
- B.
  
  TXV solenoid valve
- C.
  
  Hot gas bypass circuit
- D.
  
  Electric expansion valve
Correct Answer
D. Electric expansion valve

Explanation
The electric expansion valve controls the flow of refrigerant into the evaporator in an MA-3D air conditioner. It is responsible for regulating the amount of refrigerant that enters the evaporator coil, ensuring efficient cooling. By opening and closing the valve, it can adjust the flow rate of refrigerant based on the cooling demand, maintaining the desired temperature in the space being cooled.

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24.

The temperature controller on an MA-3D air conditioner opens the hot gas bypass valve if the
- A.
  
  Air pressure is too low so the boiling point of the R134a must be increased
- B.
  
  Suction air pressure is too high so the boiling point of the refrigerant can be decreased
- C.
  
  Suction pressure is too low so the boiling point of the refrigerant must be increased to increase the output air temperature
- D.
  
  Suction pressure is too high so the boiling point of the refrigerant must be decreased to decrease the output air temperature
Correct Answer
C. Suction pressure is too low so the boiling point of the refrigerant must be increased to increase the output air temperature

Explanation
The correct answer is that if the suction pressure is too low, the boiling point of the refrigerant must be increased to increase the output air temperature. This is because the suction pressure in an air conditioner is directly related to the boiling point of the refrigerant. If the suction pressure is too low, it means that the refrigerant is not evaporating properly, resulting in a lower output air temperature. By increasing the boiling point of the refrigerant, the temperature controller opens the hot gas bypass valve to allow more refrigerant to flow into the evaporator and increase the output air temperature.

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25.

You place the MA-3D air conditioner SW1 in the START position, but the engine does not operate. What is the probable cause of this trouble?
- A.
  
  K7 contacts are closed
- B.
  
  Overspeed switch is closed
- C.
  
  Oil pressure switch is closed
- D.
  
  Override switch is not closed
Correct Answer
D. Override switch is not closed

Explanation
The probable cause of the engine not operating when the MA-3D air conditioner SW1 is in the START position is that the override switch is not closed.

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26.

The engine on the MA-3D air conditioner is operating at 1,250 rpm, but the blower clutch does not engage. What do you do?
- A.
  
  Replace SW2
- B.
  
  Replace the engine speed control
- C.
  
  Nothing, this is normal operation; the blower clutch energizes at governed speed
- D.
  
  Check the MPU to make sure it's sending the proper signal to the engine speed control
Correct Answer
C. Nothing, this is normal operation; the blower clutch energizes at governed speed

Explanation
In this scenario, the correct answer is "nothing, this is normal operation; the blower clutch energizes at governed speed." This means that there is no need to take any action because the blower clutch will engage automatically once the engine reaches its governed speed. The blower clutch is designed to engage at a specific speed, and in this case, it will engage when the engine reaches its governed speed of 1,250 rpm. Therefore, there is no need to replace any parts or check any signals; the blower clutch will engage as intended.

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27.

What MA-3D air conditioner component provides 24 VAC for operation of the temperature controller?
- A.
  
  Generator (G1)
- B.
  
  Alternator (G2)
- C.
  
  Power monitor relay (PMR)
- D.
  
  Transformer rectifier (TR1)
Correct Answer
C. Power monitor relay (PMR)

Explanation
The power monitor relay (PMR) is the MA-3D air conditioner component that provides 24 VAC for operation of the temperature controller. The PMR is responsible for monitoring the power supply and ensuring that the voltage is within the specified range. It regulates the voltage and provides a stable 24 VAC output, which is necessary for the temperature controller to function properly. The generator (G1), alternator (G2), and transformer rectifier (TR1) are not designed to provide the specific voltage required for the temperature controller, making them incorrect choices.

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28.

The MA-3D air conditioner radiator fan stops operating. Where do you start troubleshooting?
- A.
  
  K2
- B.
  
  K4
- C.
  
  G2
- D.
  
  CB2
Correct Answer
B. K4

Explanation
The correct answer is K4. When the MA-3D air conditioner radiator fan stops operating, troubleshooting should start at K4. This suggests that there may be an issue with the fan relay or the wiring connected to it. By checking and potentially replacing the relay or repairing any faulty wiring, the radiator fan should be able to operate again.

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29.

While you are operating on MA-3D air conditioner, the output air temperature is too high, so you set the temperature control to maximum cooling. The temperature controller sends a signal to
- A.
  
  B7 which steps closed to meter R143a into the evaporator
- B.
  
  B7 which steps open to meter R134a into the evaporator
- C.
  
  The quench valve which opens to aid in cooling
- D.
  
  S1 and S2 which open to aid in cooling
Correct Answer
B. B7 which steps open to meter R134a into the evaporator
30.

What MA-3D air conditioner safety component de-energizes the compressor clutch?
- A.
  
  Low-pressure cutout (LOTO) closing
- B.
  
  Oil pressure cutout (OPCO) closing
- C.
  
  Temperature controller (TC) breaking the circuit to K2
- D.
  
  Suction pressure rising to 5 psi
Correct Answer
C. Temperature controller (TC) breaking the circuit to K2

Explanation
The temperature controller (TC) is responsible for monitoring the temperature and ensuring that it remains within a safe range. When the temperature exceeds the set limit, the TC breaks the circuit to K2, which de-energizes the compressor clutch. This action prevents the compressor from running and potentially causing damage or overheating. Therefore, the TC breaking the circuit to K2 is the correct answer as it is the safety component that de-energizes the compressor clutch.

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31.

What type of refrigeration system leak occurs when the pressure within the system is less than atmospheric pressure?
- A.
  
  Vacuum leaks
- B.
  
  Inward leaks
- C.
  
  Outward leaks
- D.
  
  Pressure leaks
Correct Answer
B. Inward leaks

Explanation
Inward leaks occur in a refrigeration system when the pressure within the system is less than atmospheric pressure. This means that air or other gases from the outside are being drawn into the system, causing a decrease in pressure. These leaks can be problematic as they can introduce contaminants or affect the efficiency of the system.

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32.

What type of engine starter does the ACE 802S air conditioner use?
- A.
  
  Air
- B.
  
  Manual
- C.
  
  Electric
- D.
  
  Hydraulic
Correct Answer
A. Air

Explanation
The ACE 802S air conditioner uses an air engine starter.

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33.

What medium is used to lubricate the engine starter on the ACE 802S air conditioner?
- A.
  
  Air
- B.
  
  Oil
- C.
  
  Fuel
- D.
  
  Coolant
Correct Answer
C. Fuel

Explanation
The medium used to lubricate the engine starter on the ACE 802S air conditioner is fuel. This is because fuel acts as a lubricant for the engine parts, including the starter, ensuring smooth operation and reducing friction. Oil is typically used for lubricating other engine components, while coolant is used for regulating engine temperature.

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34.

The compressor switch on the ACE 802S must be held in the HOLD position when engaging the compressor in order to
- A.
  
  Build up oil pressure
- B.
  
  Defrost the evaporator
- C.
  
  Allow the oil and discharge pressures to stabilize
- D.
  
  Ensure the engine is at governed speed before engaging compressor
Correct Answer
C. Allow the oil and discharge pressures to stabilize

Explanation
When engaging the compressor on the ACE 802S, holding the compressor switch in the HOLD position allows the oil and discharge pressures to stabilize. This is important because the compressor needs stable oil and discharge pressures to operate efficiently and effectively. By stabilizing these pressures, the compressor can function properly and avoid any potential damage or malfunctions.

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35.

When the ACE 802S compressor is in the HOLD position, what is the compressor displacement?
- A.
  
  Errratic
- B.
  
  Constant
- C.
  
  Minimum
- D.
  
  Maximum
Correct Answer
B. Constant

Explanation
When the ACE 802S compressor is in the HOLD position, the compressor displacement remains constant. This means that the volume of air being compressed and delivered by the compressor does not change. Regardless of any fluctuations or changes in the system, the compressor displacement remains steady and consistent.

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36.

What does the heat boost system on the ACE802S air conditioner use to trim output air temperature?
- A.
  
  Air
- B.
  
  Refrigerant
- C.
  
  Engine coolant
- D.
  
  Electric heater
Correct Answer
C. Engine coolant

Explanation
The heat boost system on the ACE802S air conditioner uses engine coolant to trim the output air temperature. Engine coolant is a liquid that circulates through the engine to absorb heat and prevent overheating. By utilizing the engine coolant, the air conditioner can regulate and adjust the temperature of the air it produces, providing a comfortable environment for the user.

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37.

What ACE 802S air conditioner components divide the refrigerant system high-pressure side from the low-pressure side?
- A.
  
  Compressor and expansion valve
- B.
  
  Condenser and expansion valve
- C.
  
  Compressor and condenser
- D.
  
  Condenser and evaporator
Correct Answer
A. Compressor and expansion valve

Explanation
The correct answer is compressor and expansion valve. The compressor is responsible for compressing the refrigerant gas, which increases its pressure and temperature. The expansion valve, on the other hand, regulates the flow of the refrigerant into the evaporator, where it undergoes a phase change and absorbs heat from the surrounding air. These two components work together to separate the high-pressure side, where the refrigerant is in a gaseous state, from the low-pressure side, where it is in a liquid state.

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38.

What ACE 802S air conditioner system "supercharges" the compressor?
- A.
  
  Defrost
- B.
  
  Heat boost
- C.
  
  Vapor injection
- D.
  
  Liquid injection
Correct Answer
C. Vapor injection

Explanation
Vapor injection is the ACE 802S air conditioner system feature that "supercharges" the compressor. This means that vapor injection enhances the performance of the compressor by injecting additional vapor into the system, increasing its efficiency and cooling capacity. This feature allows the air conditioner to provide more effective cooling and better energy efficiency compared to systems without vapor injection.

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39.

What valve must be opened prior to starting the engine on the ACE 802S air conditioner system?
- A.
  
  Air shutoff
- B.
  
  Fuel shutoff
- C.
  
  Coolant control
- D.
  
  Refrigerant control
Correct Answer
A. Air shutoff

Explanation
The valve that must be opened prior to starting the engine on the ACE 802S air conditioner system is the air shutoff valve. This valve allows air to flow into the system, which is necessary for the engine to start and run properly. By opening the air shutoff valve, the necessary air supply is provided to the engine, allowing it to function effectively.

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40.

What is the first troubleshooting step that must be accomplished when a unit comes in with a write-up in the forms?
- A.
  
  Perform a service inspection
- B.
  
  Perform an operational check
- C.
  
  Verify the problem actually exists
- D.
  
  Recognize the write-up as a malfunction
Correct Answer
D. Recognize the write-up as a malfunction

Explanation
The first troubleshooting step that must be accomplished when a unit comes in with a write-up in the forms is to recognize the write-up as a malfunction. This means acknowledging that there is a reported issue or problem with the unit. By recognizing the write-up as a malfunction, the technician can then proceed with further troubleshooting steps to identify and resolve the problem. It is important to first acknowledge the existence of the reported issue before moving on to other troubleshooting tasks.

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41.

What power source operates the heater/combustion section of the new generation heater (NGH)?
- A.
  
  12 VDC
- B.
  
  120 VAC
- C.
  
  Hydraulic motor
- D.
  
  Diesel engine only
Correct Answer
B. 120 VAC

Explanation
The correct answer is 120 VAC. This means that the heater/combustion section of the new generation heater operates using a 120-volt alternating current power source. This suggests that the heater is likely designed for use in electrical systems that provide this voltage, such as residential or commercial buildings. It may require a standard electrical outlet or connection to function properly.

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42.

How does the new generation heater (NGH) keep output air temperature within programmed limits?
- A.
  
  Burner control unit (BCU) uses outlet air sensors to compare air temperature with programmed value, cycling the fuel burner on and off to maintain temperature
- B.
  
  Heater control unit (HCU) uses outlet air sensors to compare air temperature with programmed value, cycling the fuel burner on and off to maintain temperature
- C.
  
  A photocell monitors combustion and activates the BCU to cycle the fuel burner on and off to maintain temperature
- D.
  
  An electronic thermostat cycles the main air fan on and off to maintain temperature
Correct Answer
B. Heater control unit (HCU) uses outlet air sensors to compare air temperature with programmed value, cycling the fuel burner on and off to maintain temperature

Explanation
The correct answer is the heater control unit (HCU) uses outlet air sensors to compare air temperature with programmed value, cycling the fuel burner on and off to maintain temperature. The HCU monitors the outlet air temperature using sensors and compares it to the desired programmed value. If the temperature is too low, the HCU activates the fuel burner to increase the temperature, and if the temperature is too high, it turns off the burner to decrease the temperature. By continuously cycling the burner on and off, the HCU ensures that the output air temperature remains within the programmed limits.

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43.

What adjustment on the new generation heater (NGH) prevents coking in the combustion section?
- A.
  
  Fuel pressure
- B.
  
  Air/fuel ratio
- C.
  
  Igniter timing
- D.
  
  Fuel spray pattern
Correct Answer
B. Air/fuel ratio

Explanation
The air/fuel ratio is the correct answer because it refers to the balance between the amount of air and fuel being supplied to the combustion section of the new generation heater (NGH). Maintaining the correct air/fuel ratio is crucial in preventing coking, which is the buildup of carbon deposits that can occur when there is an imbalance in the combustion process. By ensuring the proper mixture of air and fuel, the NGH can operate efficiently and prevent coking from occurring.

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44.

How does the photocell on the new generation heater (NGH) verify the flame in the burner tube?
- A.
  
  The photocell's thermal contacts open when heat increases
- B.
  
  The photocell's thermal contacts close when heat increases
- C.
  
  The photocell's resistance decreases in the presence of light
- D.
  
  The photocell's resistance increases in the presence of light
Correct Answer
C. The pHotocell's resistance decreases in the presence of light

Explanation
The photocell's resistance decreases in the presence of light. This means that when the flame in the burner tube is present and emitting light, the photocell's resistance will decrease. This change in resistance is used by the NGH to verify the presence of the flame.

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45.

When troubleshooting a defective new generation heater (NGH) charging system, what component do you check first?
- A.
  
  Charge coil
- B.
  
  Alternator G1
- C.
  
  Ignition switch
- D.
  
  Charge regulator
Correct Answer
C. Ignition switch

Explanation
When troubleshooting a defective new generation heater (NGH) charging system, the first component to check is the ignition switch. The ignition switch controls the flow of electricity to various components in the charging system, including the charge coil, alternator G1, and charge regulator. If the ignition switch is faulty or not functioning properly, it can disrupt the flow of electricity and prevent the charging system from working correctly. Therefore, checking the ignition switch is the logical first step in troubleshooting the NGH charging system.

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46.

What condition causes erratic operation of the MJ-2A-1 hydraulic test stand?
- A.
  
  Air in the system
- B.
  
  Fill relief valve set too low
- C.
  
  Thermal relief valve set too high
- D.
  
  Overserviced hydraulic reservoir
Correct Answer
A. Air in the system

Explanation
Air in the hydraulic system can cause erratic operation of the MJ-2A-1 hydraulic test stand. When air enters the system, it can create air pockets or bubbles that interfere with the proper flow of hydraulic fluid. This can lead to inconsistent performance, reduced efficiency, and potential damage to the components of the test stand. To resolve this issue, it is important to bleed the air out of the system and ensure that it is properly filled with hydraulic fluid.

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47.

The system selector valve on the MJ-2A-1 hydraulic test stand must be placed in the AIRCRAFT position during fill-and-bleed operation in order to
- A.
  
  Relieve pressure from the system
- B.
  
  Force fluid to flow into the reservoir
- C.
  
  Bypass fluid around the gear-type boost pump
- D.
  
  Force fluid to flow into the low-pressure system
Correct Answer
D. Force fluid to flow into the low-pressure system

Explanation
During the fill-and-bleed operation, the system selector valve on the MJ-2A-1 hydraulic test stand needs to be placed in the AIRCRAFT position in order to force fluid to flow into the low-pressure system. This position allows the fluid to be directed specifically into the low-pressure system, ensuring that it is properly filled and bled. Placing the valve in any other position would not achieve this desired outcome.

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48.

What MJ-2A-1 hydraulic test stand component prevents thermal expansion of the hydraulic fluid from rupturing a hydraulic line?
- A.
  
  Heat exchanger
- B.
  
  Temperature switch
- C.
  
  Thermal relief valve
- D.
  
  Low-pressure check/relief valve
Correct Answer
C. Thermal relief valve

Explanation
The thermal relief valve is the component that prevents thermal expansion of the hydraulic fluid from rupturing a hydraulic line. When the temperature of the fluid exceeds a certain threshold, the thermal relief valve opens to release excess pressure and prevent damage to the hydraulic line. This valve helps maintain the integrity and safety of the hydraulic system by regulating pressure caused by thermal expansion.

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49.

When fluid temperature is below 70 degrees F, what must be accomplished to prevent rupturing the filters on the MJ-2A-1 hydraulic test stand?
- A.
  
  Fill-and-bleed the system
- B.
  
  Adjust the thermal relief valve
- C.
  
  Open the heat exchanger bypass valve
- D.
  
  Close the heat exchanger bypass valve
Correct Answer
C. Open the heat exchanger bypass valve

Explanation
When the fluid temperature is below 70 degrees F, opening the heat exchanger bypass valve is necessary to prevent rupturing the filters on the MJ-2A-1 hydraulic test stand. This valve allows the fluid to bypass the heat exchanger, which helps to maintain the temperature of the fluid within a safe range. By opening the bypass valve, the fluid can flow without passing through the heat exchanger, preventing any potential damage to the filters caused by low temperatures.

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50.

What MJ-2A-1 test stand component must be readjusted any time the high-pressure pump compensator setting is changed?
- A.
  
  High-pressure pump volume control
- B.
  
  High-pressure relief valve
- C.
  
  Thermal relief valve
- D.
  
  Bypass valve
Correct Answer
B. High-pressure relief valve

Explanation
The high-pressure relief valve must be readjusted any time the high-pressure pump compensator setting is changed. The high-pressure relief valve is responsible for releasing excess pressure from the system to prevent damage to the components. When the compensator setting is changed, it affects the pressure in the system, and therefore the relief valve needs to be readjusted to ensure that it is still set to the correct pressure threshold for releasing excess pressure.

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Current Version
Mar 21, 2023

Quiz Edited by
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Dec 15, 2013

Quiz Created by
Chorne1787

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What adjustment on the new generation heater (NGH) prevents coking in the combustion section?

How does the photocell on the new generation heater (NGH) verify the flame in the burner tube?

When troubleshooting a defective new generation heater (NGH) charging system, what component do you check first?

What condition causes erratic operation of the MJ-2A-1 hydraulic test stand?

The system selector valve on the MJ-2A-1 hydraulic test stand must be placed in the AIRCRAFT position during fill-and-bleed operation in order to

What MJ-2A-1 hydraulic test stand component prevents thermal expansion of the hydraulic fluid from rupturing a hydraulic line?

When fluid temperature is below 70 degrees F, what must be accomplished to prevent rupturing the filters on the MJ-2A-1 hydraulic test stand?

What MJ-2A-1 test stand component must be readjusted any time the high-pressure pump compensator setting is changed?