Electrical Flashcards
Explain the meaning of the blue GRD POWER AVAILABLE light.
Ground power is connected and meets airplane power quality standards.
Describe the function of the GROUND SERVICE switch on the Forward F/A panel.
ON
OFF
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.
Explain the meaning of the blue APU GEN OFF BUS light.
APU is running and not powering a bus.
Explain the meaning of the blue GEN OFF BUS light.
IDG is not supplying power to the related transfer bus.
Recall where to read voltage, frequency and amps.
AC and DC Metering panel on the Forward Overhead panel.
Explain the meaning of the amber DRIVE light.
Integrated Drive Generator (IDG) low oil pressure.
Explain the meaning of the amber TRANSFER BUS OFF light.
Illuminated
Extinguished
Illuminated- Related Transfer Bus is not powered.
Extinguished- Related Transfer Bus is powered
Explain the meaning of the amber SOURCE OFF light.
No source has been manually selected to power the related transfer bus, or the manually selected source has been disconnected.
Explain the meaning of the amber BAT DISCHARGE light.
With BAT switch ON, excessive battery discharge detected.
Explain the meaning of the amber TR UNIT light.
Illuminated (amber) – TR failure.
Explain the meaning of the amber ELEC light.
A fault exists in DC power system or standby power system.
Note: Operates only with airplane on ground.
Explain the meaning of the amber STANDBY PWR OFF light.
3
One or more of the following busses are unpowered:
- AC standby bus.
- DC standby bus.
- Battery bus.
Recall the number of minutes available on standby power with two fully charged batteries.
-60 minutes.
Recall the function of the Ground Power (GRD PWR) Switch
OFF
neutral
ON
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 and connects ground power to AC transfer busses when power quality is correct.
Recall that it is not possible to use APU power and GRD power at the same time.
(2)
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.