ELECTRICAL Flashcards
What does the “AVAIL” light indicate on the External and APU PWR switches?
• The APU generator power quality is acceptable, and
• The related External power is plugged in, and the
power quality is acceptable.
FCOM VOL 2; 6.10.4/5
What bus is powered on the ground when APU generator 1 or external power 1 is available?
• Ground handling bus.
FCOM, VOL 2; 6.20.5
When is the MAIN DECK CARGO HANDLING bus powered?
• When the “AVAIL” light is displayed on the APU 2 or EXT 2
switches. EXT 2 has priority.
FCOM, VOL 2; 6.10.8
What electrical power source would you select if cargo handling is required?
• By selecting the number one auxiliary or external power ON,
Ensures the Main Deck Cargo Handling Bus is powered.
FCOM, VOL 2, 6.20.8 (note)
When is the ground service bus powered?
• When A/C bus 1 is powered, either on the ground or in flight.
FCOM, VOL 2; 6.20.5
What is the function of the Standby Power Switch in the Auto Position?
• Allows the main and APU standby busses to be powered from
available sources.
FCOM, VOL 2, 6.10.2
Where would you find the Electrical Power-up procedure?
• Refer to the FCOM, Vol. 1, Supplemental Procedures SP 6.1.
What does a Bus Isolation (ISLN) light illuminated indicate?
- BTB open
- AC bus isolated from synchronous bus.FCOM, VOL 2; 6.10.6
What happens when you push a Generator Drive Disconnect (DRIVE DISC) switch?
- Disconnects IDG from engine when above idle speed
- Opens related Generator Control Breaker (GCB)FCOM, VOL 2; 6.10.6
What condition would automatically disconnect the IDG if not manually disconnected by the flight crew?
• Excessively high drive oil temperature.
FCOM, VOL 2; 6.20.3 (top)
How do you reconnect an IDG that has been disconnected?
- Maintenance action is required
- The IDG cannot be restored by flight crew action (6.20.3)FCOM, VOL 2; 6.10.6
What does a Generator DRIVE light indicate?
- IDG oil pressure low, or
- IDG oil temperature high, or
- GCB open due to uncorrectable generator frequency fault.FCOM, VOL 2; 6.10.7; 6.20.3
What are some of the equipment items powered by the Utility busses?
- Forward main pumps 2 and 3
- Forward override/jettison pumps 2 and 3
- CWT L override/jettison pump
- Galley equipment (freighter)FCOM, VOL 2; 6.20.7
Describe the electrical load shedding process?
• Utility bus loads are shed one at a time through ELCUs in a
programmed priority order, until the overload condition is relieved.
FCOM, VOL 2; 6.20.1
What is the purpose of the electrical system overload protection?
• To ensure power is available to critical and essential equipment.
FCOM, VOL 2; 6.20.1
During load shedding, would you expect to see an EICAS Advisory message ELEC UTIL BUS L, R?
• No, this message is inhibited during load shedding.
FCOM, VOL 2; 6.20.1
What are the main AC electrical power sources?
- Four IDGs
- Two auxiliary power sources (APU generators)
- Two external power sourcesFCOM, VOL 2, 6.20.2
Describe the function of the Split System Breaker (SSB).
• Divides the synchronous bus, allowing each side of the AC
electrical system to be powered by separate auxiliary or external
power sources.
FCOM, VOL 2; 6.20.2
Describe the electrical system sequence of events during engine start with the SSB open?
• The IDG powers its side of the synchronous bus when voltage and
frequency are acceptable.
• The previous power source is disconnected.
FCOM, VOL 2; 6.20.2
Describe the electrical system sequence of events with a single power source powering the synchronous bus, when an engine is starting with the SSB closed.
• The IDG powers the entire synchronous bus when voltage and
frequency are acceptable.
• The SSB remains closed and the original power source is disconnected
FCOM, VOL 2; 6.20.2
Which bus powers the Captain’s transfer bus and the main standby bus?
• AC bus 3
FCOM, VOL 2; 6.20.4
Which bus powers the First Officer’s transfer bus?
• AC bus 2
FCOM, VOL 2; 6.20.4
Which bus provides backup power for both transfer busses?
• AC bus 1
FCOM, VOL 2; 6.20.6
What are some of the equipment items powered by the ground service bus?
- Main and APU battery chargers
- Fuel pumps for APU start
- Flight deck flood, navigation, and service lights
- Miscellaneous service outlets and equipmentFCOM, VOL 2; 6.20.5
