ELECTRICAL Flashcards
What happens to the APU and RAT when both transfer busses are lost in flight?
The APU automatically starts and the RAT automatically deploys
What are the components of the standby electrical system?
The Main battery, Standby inverter, RAT generator, and the C1 and C2 TRUs
What causes the IDG drive to automatically disconnect from the engine?
High generator drive temperature
The engine airplane AC/DC electrical load is supplied by ______.
any two main AC power sources
Secondary external power can power the ______.
left and right main busses
What does the illumination of a generator DRIVE light indicate?
Low IDG oil pressure
The primary external AVAIL light illuminates when the ______.
primary power source voltage and frequency are within limits
The external AVAIL light means power is plugged in and ______.
voltage and frequencies are within limits but not yet selected/connected
The BACKUP GEN OFF Light illuminated indicates _______.
a backup generator failure, a circuit fault, or the switch is off
Pushing the IFE/PASS SEATS power switch to OFF removes power from what?
All inflight entertainment components
Once one engine is started, with no other electrical source providing power and the BUS TIE switches
are in AUTO, the ______ powers both main busses.
IDG
The primary power source for the flight control DC electrical system are the _______ backup generator
PMGs.
left and right
If demand from the RAT exceeds capacity to provide hydraulic and electrical power, which has priority?
Hydraulic power - electrical load is shed until satisfactory hydraulic pressure can be
maintained
What does the main DC electrical system use to produce DC power?
TRUs
Several events can cause the backup AC electrical system to operate automatically, one of these events
is when _____.
power to one or both main AC busses is lost
The ground service bus is normally powered by the right main bus. The ______ and ______ are alternate
sources of power.
APU generator, primary external power
When the GEN CTRL switches are ON, the generator breaker is armed to close automatically when
generator power is ______.
available
The main battery provides standby power to the ______.
hot battery bus, battery bus, and standby inverter
When AC power is removed from the airplane with the BATTERY switch ON, the PA system remains
powered ______.
in flight or on the ground
The backup generator system automatically powers the right transfer bus when _____.
approach mode (APP) is selected
The main battery charger, when powered, will power the ______.
hot battery bus
The ______ normally supply power to the flight control DC electrical system.
PMGs
What is the maximum altitude for APU start?
43,100 feet
Each engine-mounted backup generator contains _____ permanent magnet generator(s) (PMG).
2
Inflight, when both BUS TIE switches are set to AUTO, the priority for powering the left and right main
busses is the ______.
respective IDG, APU generator, opposite IDG
The ______ powers the AC standby bus if the left transfer bus is not powered
standby inverter
Several items are powered by the ground handling bus, item(s) include the _____.
forward and aft cargo doors
During power source transfers (such as switching from the APU generator to an engine generator)
operating sources are momentarily paralleled to prevent power interruption _____.
on the ground
While on the ground, normally the IDG can be electrically disconnected from the main busses by
selecting an external electrical power source or ______
by selecting the GEN CTRL switch to OFF
On the ground, power transfers are made without interruption, except when ______.
switching between primary and secondary external power sources
Pushing the CABIN/UTILITY power switch to OFF removes power from the ______.
ground service bus
If primary external power is powering one or both main busses, and then the APU is started, the APU
automatically connects to _______ after reaching operating speed.
the left main bus
Which of the following is NOT powered by the ground service bus?
Refueling panel
If the electrical loads exceed power available (airplane or external), ELMS ______.
automatically sheds nonessential systems
Can you turn the battery off in flight?
No, the switch is inhibited
How does the APU generator compare to the IDGs?
It is electrically identical to the IDGs
What does the main DC electrical system use to produce DC power?
TRUs
If an IDG is manually disconnected in flight with the DRIVE DISC switch, can the pilots reconnect it?
No, maintenance action is required on the ground
