Boeing 777 Electrics
1 / 15
What does the green EXTERNAL POWER AVAIL light indicate?
2 / 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.
3 / 15
What is the primary source of power for the transfer busses?
4 / 15
On ground no power connected to the airplane. Which items will be powered if you push the BATTERY switch ON?
5 / 15
The standby inverter converts DC power to AC power. The inverter powers the AC standby bus if the right transfer bus is not powered.
The standby inverter converts DC power to AC power. The inverter powers the AC standby bus if the left transfer bus is not powered.
6 / 15
What is the primary source of standby power if all normal AC and DC power source fail?
7 / 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.
8 / 15
What is the primary power source for 'fly-by-wire'?
9 / 15
Bus tie relays, controlled by BUS TIE switches, isolate or parallel the right and left main busses. When both BUS TIE switches are set to AUTO, the bus tie system operates automatically to maintain power to both main busses.
10 / 15
What is the primary source of DC power during normal flight?
11 / 15
Which one of the following is not true about the standby inverter?
12 / 15
Which items below are de-powered if you position the BATTERY switch to OFF during power down?
13 / 15
Which one of the following is not true about the Secondary External Power?
14 / 15
You have a cold airplane (no power connected). Which items will be powered if you push the BATTERY switch ON?
15 / 15
The standby electrical system consists of:
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