Electrics Flashcards
What does the AC ESS XFER switchlight do when selected
Manually transfers the AC Essential Bus from AC BUS 1 to AC BUS 2
How can the DC Service bus be powered?
From DC BUS 2 during normal DC operation, or from the APU BAT DIR BUS through use of the DC service switch.
If ESS TRU 1 and 2 fail, how would the DC Essential Bus remain powered?
The automatic closure of the ESS TIE and the CROSS TIE will power both the DC BATT BUS and the DC ESS BUS in this situation
What is the purpose of the ESS TRU 2 Tie Contactor?
After failure of both AC BUS 2 and ESS TRU 1, allows the AC ESS BUS to power ESS TRU 2. It will also do this if on ADG power and ESS TRU 1 fails.
What does the ADG power?
H Hydraulic pump 3B E Essential AC bus F Flaps and slats at 1/2 speed A ADG bus S Stab trim channel 2
What items are powered by the DC EMER BUS?
Engine and APU fire extinguishers and hydraulic and fuel shutoff valves.
What are the Ampere/Hour and voltage ratings of the main and APU batteries?
Main 17 Amps/24 volts
APU 43 Amps/24 volts
How many TRUs does the aircraft have and what are they rated at?
4 TRUs/120 amps
What is the normal power source for the AC ESS BUS?
AC BUS 1.
What is the priority of power source for each AC bus?
Onside generator–APU generator—opposite generator—external power
What part of the IDG keeps the generator turning at a constant speed of 12,000 rpm?
Constant Speed Drive (CSD).
What is the minimum airspeed required for proper operation of the ADG generator and why must the handle be pulled after an auto deployment?
135 KIAS is minimum speed and will no longer generate sufficent power on approach. The DC ESS bus will continue to be powered through the batteries but after landing with the WOW, the internal logic will cause the loss of power to the DC ESS bus unless the handle is pulled.
What buses are powered by the ADG?
The ADG bus, AC essential bus, DC essential bus and the DC battery bus
How is normal power restored after an ADG deployment if a generator returns?
By stowing the ADG handle and pressing the PWR TXFR OVERRIDE button
What will happen to the AC ESS BUS and 3B pump after XFER Override when the aircraft generator power fails again?
They will revert back to being powered from the ADG
What busses are powered with no AC power available and the Battery Master OFF?
Main Battery Direct, APU Battery Direct and EMER DC Bus
What two conditions will result in an automatic l disconnect of the IDG?
Over temperature or Over torque
What will cause the FAULT light to illuminate on the IDG DISC Switchlight?
High CSD oil temperature or Low oil pressure
If the pilot presses the IDG DISC switchlight, the generator can be regained by releasing the switchlight
False.
If the checklist calls for it, how many attempts can be made to reset a failed generator?
ONE attempt
What DC bus is not normally displayed on the DC synoptic page?
When will it display?
DC EMER BUS
It will display when power is lost from one or both sources
What should happen if one of the engine generators fails in flight?
The AUTO XFER relays should close to allow the remaining generator to power both AC systems.
What does an illuminated FAIL light on the AUTO XFER switchlight indicate?
AUTO XFER was inhibited due to a fault on AC Bus 1 or 2.
What does it indicate if the AC ESS ALTN switchlight is illuminated?
AC ESS BUS is being powered by AC Bus 2.
Where is the APU battery located?
In the aft equipment bay
Where is the main battery located?
in the forward nose compartment
When operating off only the batteries in an emergency power situation, how many minutes of battery life does each APU start attempt cost?
6 minutes
What powers the DC emergency bus?
The APU Battery direct bus and the DC battery bus
What items are powered by the DC emergency bus
engine fire extinguishers, APU fire extinguishers, Fuel SOV’s and HYD SOV’s
Can hyd 3B pump be deselected after an ADG deployment?
no it is hardwired to the ADG bus for continuous operation
how much power does the ADG produce?
15KVA 115 volts
When will the ADG automatically deploy?
During a complete AC power failure
What does the DC ESS bus primarily provide power for?
The captains flight instruments
How are the DC bus ties controlled?
DC bus tie control is automatically accomplished through the two DC power centers DCPC
How can external power be used by the ground crew when the cockpit door is locked?
press the AC PUSH switchlight on the external service panel
Name an example the DC service switch may be used for?
External aircraft lights while re-positioning the aircraft without the battery master on
In an aircraft with no power switched on, which buses are powered?
The APU and Main battery direct buses and the emergency bus
How many volts must be present prior to APU start?
22 volts
How many AC buses are there?
Four
How many DC buses are there?
nine
What normally powers AC bus 1 and 2 and what is the switching priority in an abnormal situation?
G onside generator
A APU
G offside generator
E external power
How many DC bus ties are there?
5 the main tie, cross tie, utility tie, essential tie and essential TRU tie
What items are on the utility bus?
the passenger service units
if the cross tie closes what else will close?
The main tie and essential tie will close
when is the DC utility bus shed?
When the main tie or cross tie closes
