Ch. 6 Electrical Flashcards
The bus power control units provide electrical load management when the aircraft is operating on:
Any available electrical power source
if the permanent magnet generators are not available, the flight control electronics receive power from the:
28v DC system and main battery
what is the minimum number of external power sources required for an external power ONLY engine start?
Two (L fwd, R fwd)
the ground handling mode is powered when ____ if no other power sources source is available.
either FWD external power is connected (avail)
the generator drive may disconnect automatically ____
depending on the fault condition detected
how can the flight crew determine circuit breaker status?
check the CBIC display
what is the purpose of the permanent magnet generators (PMGs)
powers the flight control electronics
Towing power panel
when pressing the towing battery test switch, what do the following “battery state of charge indicators” mean?
high
medium
low
high: a minimum of 60 min remaining before battery charge is depleted
medium: a minimum of 30 min
low: 15 min
- minimum times assume steady state towing (no braking) before batteries are depleted. if heavy breaking occurs, actual time remaining may fall below the minimum times listed.
AOM 6.10.5
what does the b-787 electrical system power?
engine start pressurization wing ice protection stabilizer trim wheel brake systems
AOM 6.20.1
what are the electrical power sources?
4 variable frequency engine starter/generators
2 variable frequency APU starter/generators
3 external AC power receptacles
1 RAT
1 main battery
1 APU battery
3 flight control permanent magnet generators (PMG)
2 EEC permanent magnet alternators (PMA)
AOM 6.20.1
electrical power for APU start can be provided by…?
FWD external power
APU battery
engine generated power
- for APU starts with the APU battery as the power source, the right starter/generator is always used. either a left or right is for APU start when an engine is running or the FWD external power is selected ON.
AOM 6.20.2
When does the RAT deploy?
Both engines have failed
All 3 hydraulic system pressures are low
Loss of all electrical power to captain’s and first officer’s flight instruments
Loss of all 4 EMPs and faults in the flight control system occur on approach
AOM 6.20.3
What happens when the main and/or APU battery experiences a severe failure and overheats?
A sealed enclosure ensures the resulting heat and gases are contained so they pose no hazard to the airplane and it’s occupants.
if the heat and gases reach a level normally associated with a cell failure, a burst disk on the enclosure activates, venting gases directly overboard through a vent tube opening in the fuselage.
the main battery vent is located aft of the FWD E/E door, near the airplane centerline. A brief odor may be present in the flight deck just prior to the main battery disk activation.
The APU battery vent is located AFT E/E compartment.
AOM 6.20.5
What are the permanent magnet generators used for?
Primary source of power for the flight control electronics.
These power sources are independent from the main airplane electrical system, and are also independent from each other.
AOM 6.20.6
What’s the secondary source for flight controls?
The airplane’s 28 Vdc bus distribution system
Main battery
Dedicated batteries to assure positive flight control operation during temporary power interruptions
AOM 6.20.6
What do the Permanent Magnet Alternators power? (1 per engine)
Primary source of power for the EEC
AOM 6.20.6
What’s the secondary source of power for the EECs?
Secondary source of power is provided by the airplane’s 115v AC bus distribution system.
AOM 6.20.6
What are RPDU’s and how many does the B-787 have?
Remote power distribution units (the lower amperage (10 amps or less) loads are distributed by the RPDUs)
17
AOM 6.20.6
What happens when there is 1 FWD external power connected and you start the APU or an engine?
(concerning the 235 Vac 4 main buses)
The APU or engine automatically powers the 4 main 235 Vac buses, and external power transitions from ON to AVAIL
AOM 6.20.8
What powers the brakes?
the brakes are powered by 4 electrical power supply units.
they are powered by two separate 28Vdc inputs, 1 from the 28Vdc bus system, 1 from the main battery.
28Vdc bus system is primary
main battery is backup
AOM 6.20.9
what are PECS and when are they energized?
Power electronics cooling system
Energized when:
1 or both engines are running
APU running
FWD ext power is connected and selected on
AOM 6.20.9
The B-787 has several Electrical load management modes, what are they?
Towing power mode:
active when TOWING POWER switch is selected ON (with the main battery switch OFF)
Main and APU battery energize only the equipment essential for towing ops.
radio comes are not energized in towing mode.
On-ground battery mode only:
Battery switch connected ON and no other power sources connected.
this mode is to support the airplane power-up sequence.
Ground handling mode:
Active when first FWD ext power is connected but not selected ON.
Ground handling mode has priority over On-ground battery only mode, and initialized regardless of BATT switch position.
Ground service mode:
is active when the GROUND SERVICE switch on the master attendant switch panel is selected ON while in ground handling mode.
powers cabin systems and lighting etc.
External power on mode:
active when at least 1 FWD external power receptacle is connected and selected ON with the APU and engine GENs off.
more loads are energized when’s 2 FWD ext power sources are connected.
*packs and cargo heat are inop in this mode
In air RAT only mode (standby power)
active when all electrical power is lost to both captain’s and FO’s flight instruments. energizes captains flight instruments and other essential equipment.
In air battery only mode:
same as in air rat mode with the exception of center pitot heat.
AOM 6.20.13
The bus power control units provide electrical load management when the aircraft is operating on:
any available electrical power source.
If the permanent magnet generators are not available, the flight control electronics receive power from the:
28v DC system and main battery.
