Electrical Flashcards
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.
What might the DC Service switch be used for?
External aircraft lights while repositioning 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 minimum.
What is the time limit on battery power without the APU or external power and why?
5 minutes, to prevent over heating the CRTs without cooling fans.
How many AC buses are there?
Four.
How many DC buses are there?
Nine.
What normally powers AC Bus 1 & 2 and what is the switching priority in an abnormal situation?
- G - Onside Generator
- A - APU
- G - Offside Generator
- E - External Power
How many TRUs are there and what is their maximum power rating?
Four rated at 120 amps 28 vDC.
How many DC bus ties are there and what are their names?
Five:
- Main Tie
- Cross Tie
- Utility Tie
- Essential Tie
- Essential TRU Tie
If the Cross Tie closes, what else will close?
The Main and Essential Ties will always close if the Cross Tie closes.
When is the DC Utility Bus shed?
When the Main Tie or Cross Tie closes.
What items are on the Utility Bus?
The Passenger Service Units.
How are the DC bus ties controlled?
DC bus tie control is automatically accomplished through the two DC Power Centers (DCPCs).
When will the ESS TRU 2 TIE close (causing it to display on the DC synoptic page)?
With the loss of AC BUS 2 and ESS TRU 1.
What does the DC ESS bus primarily provide power for?
The Captain’s flight instruments.
When will the ADG automatically deploy?
During a complete AC power failure.
What buses are powered by the ADG?
The ADG bus, AC Essential bus, DC Essential bus, and the DC Battery bus.
What items are powered by the ADG?
- H - Hydraulic Pump 3B
- E - Essential Bus
- F - Flaps and slats at half speed
- A - ADG Bus
- S - Stab Trim channel 2
How much power does the ADG produce?
115v, 15 kVA.
What is the minimum airspeed for ADG operation?
135 KIAS?
Why must the ADG handle be pulled after an auto deployment?
After landing the WOW internal logic will cause the loss of power to the DC ESS bus if the handle is not pulled.
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.
Can Hydraulic Pump 3B be deselected after an ADG deployment?
No. It is hardwired to the ADG bus for continuous operation.
What items are powered by the DC Emergency bus?
- Engine Fire Extinguishers
- APU Fire Extinguisher
- Fuel SOVs
- Hyd SOVs
What powers the DC Emergency bus?
The APU battery direct bus and the DC battery bus.
When is the DC Emergency bus displayed on the DC synoptic page?
When power is lost from one or both of its power sources.
When operating only off the batteries in an emergency power situation, how many minutes of battery life does each APU start attempt cost?
6 minutes.
Where is the main battery located?
In the forward nose compartment.
Where is the APU battery located?
In the aft equipment bay.
