Electrical Flashcards
Describe the function of the GROUND SERVICE switch on the Forward F/A panel
Provides manual control of ground service busses. Enables servicing of airplane using external power without activating AC transfer busses
ON - connects external power to ground service bus
OFF - disconnects external power from ground service bus
VOL 2 / 6.1.5
Explain the meaning of the blue GRD POWER AVAILABLE light
Illuminated blue - ground power is connected and meets airplane power quality standards
Note: doesn’t follow dim blue/bright blue logic. If it’s on - it’s available
VOL 2 / 6.1.4
Explain the meaning of the blue APU GEN OFF BUS light
Illuminated blue - APU is running and not powering a bus (it’s available for use)
VOL 2 / 6.1.4
Explain the meaning of the GEN OFF BUS
Illuminated blue - IDG is not supplying power to the related transfer bus
VOL 2 / 6.1.4
Recall where to read voltage, frequency and amps
AC and DC metering panel on the forward overhead panel
VOL 2 / 6.1.2
Explain the meaning of the amber DRIVE light
Illuminated (amber) - integrated drive generator (IDG) low oil pressure
VOL 2 / 6.1.3
Explain the meaning of the amber TRANSFER BUS OFF light
Illuminated (amber) - Related transfer bus is NOT powered
Extinguished - Related transfer bus IS powered
VOL 2 / 6.1.4
Explain the meaning of the amber SOURCE OFF light
Illuminated (amber) - No source has been manually selected to power the related transfer bus, or the manually selected course has been disconnected
Note: SOURCE OFF light triggers ELEC light and Master Caution to alert crew of change to source of power to associated Transfer Bus
VOL 2 / 6.1.4
Explain the meaning of the amber BAT DISCHARGE light
Illuminated (amber) - with BAT switch ON, excessive battery discharge detected
VOL 2 / 6.1.2
Explain the meaning of the amber TR UNIT light
Illuminated (amber) - TR failure
TR = Transformer Rectifier
VOL 2 / 6.1.2
Explain the meaning of the amber ELEC light
Illuminated (amber) - fault exists in DC power system or standby power system
Note: operates only with airplane on the ground
VOL 2 / 6.1.2
Explain the meaning of the amber STANDBY PWR OFF light
Illuminated (amber) - one or more of the following busses are unpowered:
- AC standby bus
- DC standby bus
- Battery bus
VOL 2 / 6.1.3
Recall the number of minutes available on standby power with two fully charged batteries
60 minutes
VOL 2 / 6.2.5.2.2
Recall the function of the Ground Power (GRD PWR) switch
Three position switch, spring loaded to neutral
OFF - disconnects ground power from AC transfer busses
ON - if momentarily moved to ON position and ground power is available:
- removes previously connected power from AC transfer busses
- connects ground power to AC transfer busses when power quality is correct
VOL 2 / 6.1.4
Recall that it is not possible to use APU power and GRD power at the same time.
There are two basic principles of operation for the 737 electrical system:
- No paralleling of AC sources of power
- The source of power being connected to a transfer bus automatically disconnects the existing source
VOL 2 / 6.2.1.2
Recall the function of positioning the APU Generator (GEN) switches to ON
Three position switch, spring loaded to neutral.
Neither AC transfer by powered by an IDG:
Moving an APU GEN switch to ON:
- Powers both AC transfer busses from the APU generator
- Disconnects external power, if connected
- Opposite SOURCE OFF light illuminates until the APU GEN switch is moved ON
Both AC transfer busses powered by IDGs:
Moving an APU GEN switch to ON:
- Powers the related AC transfer bus from the APU generator
- Other AC transfer bus continues to receive power from the IDG
VOL 2 / 6.1.4
Recall the components powered by the ground service bus
- Utility outlets
- Cabin lighting
- Battery chargers
Memory Aid:
CUB
VOL 2 / 6.2.2.4