Electrical Flashcards
Five (5) sources of AC power:
+ Two (2) engines
+ APU generator
+ External power
+ Hydraulic Driven Generator (HDG)
Main battery and Standby system powers:
+ Hot Battery Bus
+ Battery Bus
+ Standby AC Bus + Standby DC Bus
DC Fuel Pump only operates when no AC power available.
(Automatic with no pilot control.)
When AC power is available, Left FWD AC fuel pump supplies APU.
(Automatic regardless of switch position.)
APU fuel supplied
From left manifold
APU BATT:
+ Starter
+ Air inlet door
+ APU control circuits
AC BATT:
+ Fire protection
+ APU fuel valve
+ DC fuel pump
In Flight, the main BATT Switch will not affect APU operation.
(Turning off main battery will not shut down APU)
APU RUN Light illuminates approximately
95%
APU Start indications:
+ FAULT Light flashes once
+ RUN Light flashes twice
APU GEN OFF Light illuminated with APU running,
APU generator control breaker open due to faults
APU starter duty cycle,
three (3) consecutive attempts within a 60 minute period.
APU shutdown cooling
normally approximately 60 seconds. (May vary between zero (0) to 120 seconds.)
APU Selector is accidently moved to OFF with RUN Light illuminated,
moving Selector momentarily to START then back to RUN cancels shutdown.
APU FAULT Light illuminated
APU will shut down
APU fire warning
APU will shut down
APU fire detection
On BATT BUS
APU fire protection
On batt bus
Ground Service Bus powers:
Battery charger(s) (one or two)
+ Equipment cooling fan
+ Left FWD Fuel pump
Load shedding during normal operations:
+One (1) electric hydraulic pump prior to engine start
+ Both center tank fuel pumps prior to engine start + Both utility busses during engine start (galley power) (When second engine is started only respective utility bus sheds)
Load shedding in flight after engine failure:
\+ Utility busses (galley power) \+ Respective center tank fuel pump \+ All cabin indirect ceiling lights \+ FWD direct ceiling lights \+ C2 hydraulic pump
The Hydraulic Driven Generator (HDG) activates automatically
when both L and R Main AC Busses are unpowered.
The Hydraulic Driven Generator (HDG) provides power
\+ Left AC XFR Bus \+ Right AC XFR Bus \+ Standby AC Bus (through L AC XFR Bus) \+ Captain’s FLT INSTR XFR Bus \+ Hot Battery Bus \+ Battery Bus \+ Standby DC Bus
GEN DRIVE Light illuminated:
+ High oil temperature + Low oil pressure
