Boeing 777 Electrics
1 / 15
During autoland, the busses isolate to allow three independent sources to power the three autopilots.
The left IDG powers the left AC transfer bus, the left main DC bus, and the captain’s flight instrument bus The right IDG powers the battery bus and AC standby bus through the main battery charger The backup system powers the right AC transfer bus, the right DC bus, and the first officer’s flight instrument bus.
2 / 15
How many main AC power sources are required to maintain the entire plane AC electrical load?
3 / 15
If the RAT is unable to maintain RPM, the RAT generator electrical load is shed until RPM is satisfactory. Power for standby electrical loads is provided by the main battery during deployment of the RAT and when RAT generator loads are shed.
The RAT is deployed automatically if both AC transfer busses lose power in flight. The RAT can be manually deployed by pushing the RAM AIR TURBINE switch on the overhead panel.
4 / 15
Which one of the following is not true about the APU generator?
5 / 15
What is the secondary source of power for 'fly-by-wire' if one or more PMGs are unpowered?
6 / 15
Primary power for the flight control DC electrical system comes from permanent magnet generators (PMGs) housed within each backup generator. Variable frequency PMG AC power is used by individual power supply assemblies (PSAs) to provide DC power to the three flight control DC busses. To ensure a high level of system reliability, each PSA also has multiple AC power sources.
To ensure a high level of system reliability, each PSA also has multiple DC power sources (No AC power!). If primary PMG AC power is not available, secondary power for the left and right PSAs is provided by the related main DC bus. Secondary power for the center PSA is provided by the captain’s flight instrument bus. The hot battery bus provides additional backup power for the left and center PSAs only. Each PSA also uses a dedicated battery to prevent power interruptions to the related flight control DC bus. The batteries have limited capacity and are incorporated to supply power for brief periods during PSA power source transfers.
7 / 15
Backup power is provided by one variable speed, variable frequency generator mounted on each engine. A frequency converter converts the generator frequency to a constant 400 Hz. Only one backup generator can power the converter at a time.
8 / 15
What provides DC power on the B777?
9 / 15
Which one of the following is not true about the Primary External Power?
10 / 15
Which bus operates only on the ground?
11 / 15
Which one of the following is not true about the standby inverter?
12 / 15
Which bus powers the main battery charger and the APU battery charger?
13 / 15
How are the busses powered if the right engine is started with the APU powering the left bus system and external power powering the right bus system?
14 / 15
The Electrical Load Management System (ELMS), manages load shed priority (galley first, utility bus second, then selected AC components).
15 / 15
Will the IDG disconnect automatically for high temperature?
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