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What are the components of the elecrtical system?
- Four 28 VDC Generators
- One APU Generator 28VDC
- 2 Nic CAD 24VDC batteries
- One lead acid backup battery 24VDC
- 1 Inverter converts DC to AC controls TCAS windshear/GPWS, not powered in electrical emergency.
What are the electrical rules?
- GPU runs the show
- GPU cant charge the batteries
- 4 Gens = Two Networks
- Only BATT 2 can start APU
- 3 Gens = 1 network
- <3 gens = 1 network + lose shed busses, in flight
- ESS PWR Switch= overrides the EDL regardless of battery positions forcing the batteries power the ESS Buses.
What network do Gens 1+3 form?
- Left network driven by Engine 1
- Right network driven by Engine 2
What is EDL and what does it do?
- Electrical Distribution Logic
- Is the logic behind the system about what has priority in different situations
What are GCUs?
- Generator Control Units,
- Deenergizes the Generator if and overvoltage situation exists.
- Removing it from the system.
What happens when GPU AVAIL is lit?
What items are being powered?
- Ground service bus is energized.
- Passenger Cabin lights, lav lights, galley lights, courtesy stair lights, cockpit dome light, baggage compartment light.
Max temperature for two NiCAD batteries?
How much time wll they keep the airplane powered if all gens fail?
- 40 minutes in flight
- 12-15 on the ground.
Why is there less time on the ground for batteries than in the air?
- On the ground all buses are powered.
- In flight only essential buses are powered.
When does the Generator come on line?
56.4 % N2
What five items are on in an electrical emergency?
ISIS, RMU1, RMU2, EICAS, Light on Compass.
What does the Lead acid battery do?
What happens when the button is pressed in?
- Provides a stabilized power for operations of the GCUs protective function when voltage gets low.
- The battery is being charged and removed from the system when pressed out. EICAS message comes on.
What are the voltage limits on battery for APU start?
- 23.5 and up, normal start for APU
- 19-23.5V BATT1 off and start APU, wait three minutes before turning on BATT1. Will charge battery and will need at least 30 minutes.
- below 19 v call maintenance.
What needs to happen for all DC buses to be energized
- At least three generators online
- GPU is on and connected
- One Gen is online and shedd buses to ovrd.
What is on the Hot BATT BUses?
Fire extinguishers, Fuel and hydraulic shutoff valves, ELT, main door control, courtes lights and pressure refueling
What is on the shedd buses?
Recirc Fans, Nose landing lights, coffee maker, and taxi lights