United 737 Electrical Flashcards
Minimum voltage for APU start___
23 Volts
When a source of power is connected to a bus system____ occurs?
It automatically disconnects an existing source
What does a GRD POWER AVAILABLE light do?
Provides flight deck indication that AC ground power is connected to the aircraft and meets aircraft power quality standards.
If the BUS TRANS switch is in the AUTO position and the source powering the transfer bus is disconnected or fails, what does the source powering the opposite transfer bus through the BTB’s do?
Automatically picks up the unpowered transfer bus
What do the 3 TRs do?
Conver 115 volt AC to 28 volt DC
Inflight, when does an amber TR UNIT light illuminate?
TR1 or TR2 AND TR3 has failed
How long does a fully charged battery have sufficient capacity to provide electrical power for? (Single battery config)
30 Minutes
When does an amber BAT DISCHARGE light illuminate?
Excessive battery discharge is detected
If one or more of the following buses are unpowered, _____ it is indicated by an illuminated STANDBY POWER PWR OFF light
All answers are correct
In flight or on the ground, with the STANDBY POWER SWITCH in AUTO (guarded position) in with the loss of all AC power, the AC standby bus is powered by_____ and the DC standby bus is powered by ____
the battery through static inverter; battery
The light on the overhead panel that illuminates if the APU is running and not supplying power to a bus is the ___
APU GEN OFF BUS
On the ground and inflight, the APU generator can supply power to ___
both transfer busses
The electrical system is designed to ____ during single generator operation
Shed electrical loads incrementally
When ___ oil is sensed in the IDG, the amber DRIVE caution light is illuminated
LOW
Which of the following can cause IDG low oil Pressure?
IDG Auto Disconnect due to HIGH OIL TEMPERATURE
IDG Disconnected through Generator Drive Disconnect Switch
An amber ___ light illuminates to indicate the DC system or standby system equipment has failed, while the aircraft is on the ground. The light is inhibited in flight.
ELEC
Primary electrical power is provided by ___ engine driven IDGs
2
During normal operation the guarded Standby Power Switch will be in ____ and the battery switch will be ___
AUTO; ON
Which switch can be used to remove power from the left and right recirc fans, forward and aft door area heaters, lav water heaters, ECS fan, all 115V AC galley busses, 115V AC shaver outlets logo light and potable compressor?
CAB/UTIL SWITCH
IFE/PASS SEAT SWITCH does what
removes power from 115V AC audio entertainment equip, video entertainment, airphone equipment, pax seat electronic unit
Moving ground power switch to on does what?
ALL answers are correct
What light on the overhead panel immuniates if the transfer bus is not being powered?
TRANSFER BUS OFF
What light on the overhead panel illuminates if the transfer bus is not powered by the source selected by the related generator switch?
SOURCE OFF
What light on the overhead illuminates if the IDG is not supplying power tot he related transfer bus?
GEN OFF BUS
Moving the Generator switch to ON connects ____ by disconnecting the previous power source and closing the generator circuit breaker.
IDG to the AC Transfer Bus
What light on the overhead panel illuminates if the APU is running and not supplying power to a BUS?
APU GEN OFF BUS
Which switch provides manual control of ground service busses enabling servicing of the aircraft using external power without activating AC transfer busses?
GROUND SERVICE switch on the FWD attendant panel
