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.
