Electrical Flashcards
Electrical
What is the purpose of ELMS?
ELMS (Electric Load Management System) provides load management and protection to ensure power AVBL to essential equipment.
What loads can be shed by ELMS?
Galleys first, the utility busses, then individual equipment items powered by main AC busses.
What indication is there of ELMS load shedding?
LOAD SHED message displays on electrical synoptic.
List the main electrical sources?
• L & R IDGs. • APU generator. • Primary & secondary external power.
(ACFT also has BUGs [back up generators], RAT [Ram Air Turbine] and battery).
What will cause illumination of the DRIVE light?
IDG low oil pressure.
What causes an automatic disconnection of the IDG?
IDG high oil temperature.
When will the APU start automatically?
When no other source of power becomes AVBL when the APU generator becomes AVBL (both transfer busses are unpowered).
When does the external power AVAIL light illuminate?
When external power source voltage & FREQ is connected and W/in limits.
What is the generator priority for the main busses?
Respective IDG à APU generator à opposite IDG.
What is the normal source for the Ground Service Bus?
R main AC bus.
How is the Ground Service Bus powered without supplying the main busses?
• APU generator. • Primary external power.
CX ACFT have a Ground Service switch at in the cabin at door L1
What loads are supplied by the Ground Service Bus?
• Main battery charger. • APU battery charger. • Miscellaneous cabin & system loads.
When is the Ground Handling Bus powered?
On GND only.
. What loads are supplied by the Ground Handling Bus?
• Cargo handling & lighting. • Refuelling/defuelling operations. • Other equipment energised only during GND operations.
What is supplied by the backup AC electrical system?
• R AC transfer bus. • R DC bus. • F/O’s FLT instrument bus.
What unit converts the back up generator frequency?
FREQ converter.
How many backup generators can be used at a time?
1 (since BUGs have same input).
What are the PMGs in the backup generator used for?
To supply DC power to FLT control power supply assemblies (FCDCs).
Which AC busses supply the TRUs?
L & R AC transfer busses.
What normally powers the hot battery bus?
Main battery charger.
What is the purpose of the APU battery?
Provides power to APU electrical starter (used when insufficient bleed air for APU turbine starter). .
What is the secondary power source for the C FCDC PSA?
Captain’s FLT instrument bus.
Which FCDC PSAs can be powered by the hot battery bus?
L & C PSAs only.
What is the purpose of the dedicated PSA battery?
To avoid power interruptions to the related FLT control DC bus
What type of power is provided by the standby electrical system?
DC & AC power.
What does the standby electrical system supply?
• FLT instruments. • Communication & navigation equipment.
When does the standby inverter supply the AC standby bus?
When L transfer bus is not powered.
What does the RAT generator supply?
STBY power to C1 & C2 TRUs.
What are the altitude and airspeed limitations of the RAT generator?
None (operates at all ALTs & airspeeds)
What supplies power until the RAT RPM is sufficient?
Main battery.
What will cause automatic deployment of the RAT?
• Both AC transfer busses lose power in FLT. • Both engines are failed and C system pressure is low. • All 3 hydraulic system pressure are low.
