Boeing B777 - Electrical
What is the source of standby electrical power if the RAT sheds electrical power because of low hydraulic pressure?
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.
Will the IDG disconnect automatically for high temperature?
How can you power the ground handling bus before shutdown if no external power is available?
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.
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.
When will the RAT auto-deploy?
Which one of the following is not true about the Primary External Power?
What is the secondary source of power for 'fly-by-wire' if one or more PMGs are unpowered?
During autoland, the busses isolate to allow three independent sources to power the three autopilot. In this case which one of the following is the power source for the right AC transfer bus, the right DC bus, and the first officer's flight instrument bus?
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What is the primary source of power for the transfer busses?
What is the primary power source for 'fly-by-wire'?
What is the electrical configuration during autoland?
Which one of the following is not a reason for the backup electrical system to automatically power one or both transfer busses?
Which of the following is not a main AC electrical power source?
Which one of the following is not true about the standby inverter?
On ground no power connected to the airplane. Which items will be powered if you push the BATTERY switch ON?
Which one of the following is not true about the APU generator?
When does the right transfer bus isolate from the right main bus?
How many total AC sources of power does the B777 accommodate?
Seven (2 IDG, APU, PRI and SEC external power, 2 BUG).
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What automatic switching will occur if you start the APU with external power on the BUS TIE system?
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.
Which condition(s) cause the ELEC GEN DRIVE L EICAS message to display?
Which one of the following is not true about the backup electrical system?
How can you power the ground handling bus before shutdown if no external power is available?
Which one of the following is not true about the Secondary External Power?
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.
The Electrical Load Management System (ELMS), manages load shed priority (galley first, utility bus second, then selected AC components).
What is the primary source of DC power during normal flight?
Which one of the following is not true about the DC electrical system?
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What provides DC power on the B777?
Which items below are de-powered if you position the BATTERY switch to OFF during power down?
What is the primary source of standby power if all normal AC and DC power source fail?
Which one of the following is not true about the ram air turbine (RAT) generator?
What is the correct source order for powering left and right main busses in flight?
Which bus powers the main battery charger and the APU battery charger?
Which one of the following is not true about the flight control DC electrical system?
How many main AC power sources are required to maintain the entire plane AC electrical load?
Does electric power has priority over hydraulic power from the RAT?
Hydraulic has priority, and if electric is shed, only the CA instrument bus is powered through the main battery
Which bus operates only on the ground?
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Which one of the following is not true about Electrical Load Management System (ELMS)?
What does the green EXTERNAL POWER AVAIL light indicate?
What is the correct electrical panel configuration for normal flight?
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.