Electrical System, Fire Protection And Detection System
The electrical system for an airliner is a very sensitive subject and a mechanic must ensure there are no possibilities for a fire occurring due to electrical wiring problems, as it can be catastrophic. The quiz below is designed to test out how much you know about wiring a Boeing 737. Give it a shot!
- 1.
What does the illumination of the “elec” light on the electrical panel indicate:
- A.
A fault has been detected in the AC or standby power system.
- B.
A fault has been detected in the DC or standby power system.
- C.
A fault has been detected in the DC and standby power system.
- D.
A fault has been detected in the AC and standby power system.
Correct Answer
B. A fault has been detected in the DC or standby power system.Explanation
The illumination of the "elec" light on the electrical panel indicates that a fault has been detected in the DC or standby power system. This means that there is an issue with either the DC power system or the standby power system, which could potentially cause a disruption in the electrical supply. It is important to address this fault promptly to ensure the proper functioning of the power system.Rate this question:
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- 2.
How is the main battery charger powered:
- A.
By the DC ground service bus 2
- B.
By the AC ground service bus 1
- C.
By the DC ground service bus 1
- D.
By the AC ground service bus 2
Correct Answer
D. By the AC ground service bus 2Explanation
The main battery charger is powered by the AC ground service bus 2.Rate this question:
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- 3.
With the standby power switch in the AUTO position, what will cause automatic switching to the Alternate power source:
- A.
AC transfer bus 1 or DC bus 2 loses power
- B.
AC transfer bus 1 or DC bus 1 loses power
- C.
DC transfer bus 1 or DC bus 2 loses power
- D.
DC transfer bus 1 or DC bus 1 loses power
Correct Answer
B. AC transfer bus 1 or DC bus 1 loses powerExplanation
When the standby power switch is in the AUTO position, the automatic switching to the alternate power source will occur if either AC transfer bus 1 or DC bus 1 loses power.Rate this question:
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- 4.
After a generator drive disconnect, can the drive be re-engaged:
- A.
Yes, in flight
- B.
Only on the ground (by maintanance)
- C.
Yes on ground (by flight crew)
- D.
No
Correct Answer
B. Only on the ground (by maintanance)Explanation
After a generator drive disconnect, the drive can only be re-engaged on the ground by maintenance. This means that the drive cannot be re-engaged while the aircraft is in flight. The maintenance crew is responsible for addressing any issues with the generator drive and ensuring that it is properly re-engaged before the aircraft can continue operating. The flight crew does not have the capability to re-engage the drive themselves.Rate this question:
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- 5.
What is the normal supply to the battery bus:
- A.
By the AC ground service bus 1
- B.
By the DC ground service bus 1
- C.
By the AC ground service bus 2
- D.
By the DC ground service bus 2
Correct Answer
A. By the AC ground service bus 1Explanation
The normal supply to the battery bus is provided by the AC ground service bus 1.Rate this question:
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- 6.
When will the switched hot battery bus be powered by a functional battery:
- A.
With APU running
- B.
When Ground Power is connected
- C.
Always
- D.
When the battery switch is selected to ON
Correct Answer
D. When the battery switch is selected to ONExplanation
The switched hot battery bus will be powered by a functional battery when the battery switch is selected to ON. This means that the battery is connected to the electrical system and is providing power to the switched hot battery bus.Rate this question:
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- 7.
What does illumination of the “GND Power Available” light indicate:
- A.
That DC ground power is connected
- B.
That AC ground power is connected and meets airplane power quality standards
- C.
That Ground power can be requested
- D.
That the power is 3 phased and grounded
Correct Answer
B. That AC ground power is connected and meets airplane power quality standardsExplanation
The illumination of the "GND Power Available" light indicates that AC ground power is connected and meets airplane power quality standards. This means that the aircraft is receiving a reliable and high-quality power supply from an external source.Rate this question:
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- 8.
In flight, what does illumination of the “TR UNIT” light indicate:
- A.
TRU1 or TRU2 and TRU3 have failed.
- B.
TRU1 Failed
- C.
TRU2 Failed
- D.
All TRU's Failed
Correct Answer
A. TRU1 or TRU2 and TRU3 have failed.Explanation
The illumination of the "TR UNIT" light indicates that either TRU1 or TRU2 and TRU3 have failed.Rate this question:
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- 9.
In flight, the output from no1 IDG fails. How is power AC transfer bus 1 restored:
- A.
Via power x-feed switch
- B.
Manually from AC transfer bus 2 via the AC tie bus.
- C.
Automatically from AC transfer bus 2 via the AC tie bus.
- D.
Automatically from the battery
Correct Answer
C. Automatically from AC transfer bus 2 via the AC tie bus.Explanation
When the output from no1 IDG fails during a flight, power AC transfer bus 1 is automatically restored by transferring power from AC transfer bus 2 via the AC tie bus. This is done automatically without any manual intervention or reliance on the battery.Rate this question:
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- 10.
Following the loss of an IDG, with a single generator operating, which loads are initially shed:
- A.
Galley A
- B.
Galley B
- C.
Galley bus A + B (shed from transfer bus 1)
- D.
Galley bus A + B (shed from transfer bus 2)
Correct Answer
D. Galley bus A + B (shed from transfer bus 2)Explanation
When an Integrated Drive Generator (IDG) is lost and only one generator is operating, the loads that are initially shed include Galley bus A + B (shed from transfer bus 2). This means that the power supply to Galley bus A and Galley bus B is disconnected from transfer bus 2. This shedding of loads is necessary to balance the power supply and demand in the system and prevent overloading of the remaining generator.Rate this question:
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- 11.
What are the normal AC volts and frequancy for the 2 engine driven generators and the APU generator:
- A.
115 v (+/- 5 v) and 400Hz (+/- 10 Hz)
- B.
220 v (+/- 5 v) and 400Hz (+/- 10 Hz)
- C.
115 v (+/- 5 v) and 600Hz (+/- 10 Hz)
- D.
220 v (+/- 5 v) and 600Hz (+/- 10 Hz)
Correct Answer
A. 115 v (+/- 5 v) and 400Hz (+/- 10 Hz)Explanation
The normal AC volts and frequency for the 2 engine driven generators and the APU generator are 115 v (+/- 5 v) and 400Hz (+/- 10 Hz).Rate this question:
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- 12.
What is the battery voltage:
- A.
24 volts DC. Range is 22 to 30 volts and supplies standby power for 30 minutes (single battery)
- B.
24 volts DC. Range is 22 to 30 volts and supplies standby power for 60 minutes (single battery)
- C.
28 volts DC. Range is 22 to 30 volts and supplies standby power for 30 minutes (single battery)
- D.
28 volts DC. Range is 22 to 30 volts and supplies standby power for 60 minutes (single battery)
Correct Answer
A. 24 volts DC. Range is 22 to 30 volts and supplies standby power for 30 minutes (single battery)Explanation
The correct answer is 24 volts DC. This is because the given information states that the battery voltage is 24 volts DC. Additionally, the range is specified as 22 to 30 volts, which falls within the given voltage. Lastly, it is mentioned that the battery supplies standby power for 30 minutes, which matches the information provided.Rate this question:
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- 13.
DC power is supplied by 3 TR units. What is the output Voltage:
- A.
28 volts DC.
- B.
24 volts DC
- C.
24 volts AC
- D.
28 volts AC
Correct Answer
A. 28 volts DC.Explanation
The correct answer is 28 volts DC. This is because the question states that DC power is supplied by 3 TR units. DC stands for direct current, which means that the voltage is constant and flows in one direction. Therefore, the output voltage would also be DC. The given answer of 28 volts DC aligns with the information provided in the question.Rate this question:
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- 14.
Where does TRU no 2 receive its AC power from:
- A.
AC transfer bus 2
- B.
AC transfer bus 1
- C.
From hot battery bus
- D.
From battery bus
Correct Answer
A. AC transfer bus 2Explanation
TRU no 2 receives its AC power from AC transfer bus 2. This means that the power is transferred from the AC transfer bus 2 to TRU no 2 for its operation.Rate this question:
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- 15.
The aircraft is on the ground on stand, with engines running, and both generators on line. External power is available. What will positioning the ground power switch to ON do:
- A.
Trip both engine generators and APU
- B.
Connect external power and keep generators running.
- C.
Trip both engine generators and connect external power and connect external power to the transfer busses.
- D.
Ground power can not be connected with engines running.
Correct Answer
C. Trip both engine generators and connect external power and connect external power to the transfer busses.Explanation
Positioning the ground power switch to ON in this scenario will trip both engine generators and connect external power to the transfer buses. This means that the aircraft will be disconnected from its own generators and rely solely on the external power source. Additionally, the external power will be connected to the transfer buses, allowing it to power the necessary systems and equipment on the aircraft.Rate this question:
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- 16.
With AC power on the bus bars, no system faults, and OVHT DET switches in NORMAL, selecting OVHT/FIRE on the test switch will illuminate wich lights:
- A.
Master FIRE WARNING lights
- B.
Master caution lights
- C.
Master FIRE WARNING lights, ENG1+ENG2 and APU fire switch lights, and WHEEL WELL FIRE light, Plus the MASTER caution lights, OVHT/DET annunciator and the ENG+ENG OVERHEAT lights.
- D.
OVHT/DET Lights
Correct Answer
C. Master FIRE WARNING lights, ENG1+ENG2 and APU fire switch lights, and WHEEL WELL FIRE light, Plus the MASTER caution lights, OVHT/DET annunciator and the ENG+ENG OVERHEAT lights.Explanation
When the AC power is on the bus bars, there are no system faults, and the OVHT DET switches are in NORMAL, selecting OVHT/FIRE on the test switch will illuminate several lights. These include the Master FIRE WARNING lights, ENG1+ENG2 and APU fire switch lights, and WHEEL WELL FIRE light. Additionally, the MASTER caution lights, OVHT/DET annunciator, and the ENG+ENG OVERHEAT lights will also be illuminated.Rate this question:
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- 17.
With the OVHT/DET switch in the normal position, and both loobs servicable, when will engine fire warning be activated:
- A.
If one loop detects a fire or a overheat condition.
- B.
When both loops detect a fire condition.
- C.
When both loops detect a overhead condition
- D.
When both loops detect a fire condition or an overheat condition
Correct Answer
B. When both loops detect a fire condition.Explanation
When both loops detect a fire condition, the engine fire warning will be activated. This means that both fire detection loops must independently detect a fire in order for the warning to be triggered. If only one loop detects a fire or an overheat condition, the warning will not be activated. Similarly, if both loops detect an overheat condition without a fire, the warning will not be activated.Rate this question:
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- 18.
Illumination of the FAULT light on the Overheat/Fire detection panel indicates what:
- A.
With the Overheat Detector in the NORMAL position, one loop has failed
- B.
With the Overheat Detector in the NORMAL position, Both loops have failed.
- C.
With the Overheat Detector in the AUTO position, Both loops have failed.
- D.
With the Overheat Detector in the AUTO position, one loop has failed.
Correct Answer
B. With the Overheat Detector in the NORMAL position, Both loops have failed. -
- 19.
If a malfunction in one fire loop occurs, with the OVHT DET switch in the normal position, do you still have detection availiable:
- A.
No, if a malfunction occurs, system is not availiable for the rest of the flight.
- B.
Yes. The defective loop is removed, and the remaining loop continues functioning as a single loop detector.
- C.
Yes, but the switch must be put in ALTN selection
- D.
Yes, but a amber OVHT light wil illuminate for the rest of the flight.
Correct Answer
B. Yes. The defective loop is removed, and the remaining loop continues functioning as a single loop detector.Explanation
If a malfunction occurs in one fire loop with the OVHT DET switch in the normal position, the system is still available for the rest of the flight. This is because the defective loop is automatically removed from the system, and the remaining loop continues to function as a single loop detector.Rate this question:
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- 20.
The power source for the APU fire extinguishing system is the:
- A.
DC transfer bus 2
- B.
The hot battery bus (28v DC)
- C.
Ground power
- D.
DC transfer bus 1
Correct Answer
B. The hot battery bus (28v DC)Explanation
The correct answer is the hot battery bus (28v DC). The hot battery bus is a direct current (DC) power source that provides electrical power to various systems on the aircraft. The APU fire extinguishing system is one of these systems and it relies on the hot battery bus to supply power for its operation. This ensures that the APU fire extinguishing system has a reliable power source to effectively extinguish any fires that may occur in the APU.Rate this question:
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- 21.
The power source for the ENG Overheat and Fire Protection detection system is:
- A.
Battery bus (28v DC)
- B.
Hot battery bus
- C.
Transfer bus 1
- D.
Transfer bus 2
Correct Answer
A. Battery bus (28v DC)Explanation
The power source for the ENG Overheat and Fire Protection detection system is the Battery bus (28v DC). This means that the system is powered by the aircraft's battery, which provides a direct current of 28 volts. The battery bus is a common source of power for various systems in an aircraft, including critical systems like fire detection and protection. It ensures that the detection system has a reliable and independent power source to operate effectively in case of an engine overheat or fire situation.Rate this question:
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- 22.
When the extinguisher test switch is held in the 1 or 2 position, 3 green lights should illuminate. What does this indicate:
- A.
The associated bottle discharge circuits for all 3 extinguisher bottles are normal.
- B.
That wheel extinguishers are tested and ok
- C.
The bottles are armed and have surficient contense
- D.
The three wheel well areas are tested for overheat.
Correct Answer
A. The associated bottle discharge circuits for all 3 extinguisher bottles are normal.Explanation
The correct answer indicates that when the extinguisher test switch is held in the 1 or 2 position, 3 green lights illuminate, indicating that the associated bottle discharge circuits for all 3 extinguisher bottles are normal. This means that the circuits are functioning properly and there are no issues with the discharge of the extinguisher bottles.Rate this question:
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- 23.
The engine fire warning switch lock mechanism is automatically unlocked when:
- A.
It is put in AUTO mode.
- B.
Either the fire warning or overheat light illuminates.
- C.
When aircraft is in flight.
- D.
Engine ignition key is put in
Correct Answer
B. Either the fire warning or overheat light illuminates.Explanation
When either the fire warning or overheat light illuminates, it indicates a potential issue with the engine. In such a situation, the engine fire warning switch lock mechanism is automatically unlocked to allow the pilot to take immediate action and address the problem. This ensures that the pilot has the ability to respond quickly and effectively to any engine-related emergencies while in flight.Rate this question:
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