Systems - Electrics Flashcards
On an unpowered airplane, what instruments are powered when the Battery switch is turned on?
- Captain PFD
- Captain ND
- IFSD
- left CDU
- captain radio stack
- PA
How many batteries are on the 777?
2
- Main
- APU
Can the battery switch be turned off:
- in flight?
- on the ground?
- Inflight system logic prevents it from being turned off
- On the ground it will turn off
How long should the Main battery power the STBY system?
At least 10 minutes
You enter a cold dark airplane and find the EXT PWR AVAIL lights on. What must be done before selecting external power ON?
Interior safety inspection
When you arrive at the airplane, primary and secondary external power are both connected and selected on. As part of your preflight duties you start the APU. What bus does it automatically connect to?
Left main bus
What should you check before disconnecting external power?
APU running
When does the APU shut down automatically?
- In unattended mode for any parameter exceedance, no cool down period
- In attended mode for fire, overspeed/loss of overspeed protection/speed droop, APU controller failure, also for high EGT/oil temp or low oil press. No cool down period
When will the APU fire bottle discharge automatically?
In unattended mode fire bottle discharges for fire signal from either detector loop.
What does the APU fault light indicate during and after APU start?
-During a start an APU controller is doing a self test
-After a start an automatic shutdown occurred due to fault or fire
When does the APU start automatically?
Loss of both transfer busses
What is the altitude limit for APU start?
43,100
What is the purpose of the back-up generators?
- To house the PMGs
- To power one or both transfer busses when respective AC power is lost
- To provide redundancy for the AUTOLAND system
What is the STBY bus normally connected to:
- directly?
- abnormally?
- L XFR bus normally
- CA INST bus via inverter abnormally
What is the main purpose of the XFR buses?
To power essential Loads/Equipment
What causes the generator drive light to illuminate?
Low oil pressure
What causes the generator drive to disconnect?
High drive temp
How does the IDG provide constant level of output through the varying engine speed range?
Through a Constant Speed Drive
What is the source of DC power in normal flight?
Through the TRUs whenever the transfer busses are powered by their respective main AC busses.