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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.
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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.
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What network do Gens 1+3 form?
Gens 2+4?
- Left network driven by Engine 1
- Right network driven by Engine 2
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What is EDL and what does it do?
- Electrical Distribution Logic
- Is the logic behind the system about what has priority in different situations
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What are GCUs?
- Generator Control Units,
- Deenergizes the Generator if and overvoltage situation exists.
- Removing it from the system.
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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.
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Max temperature for two NiCAD batteries?
How much time wll they keep the airplane powered if all gens fail?
- 70*c
- 40 minutes in flight
- 12-15 on the ground.
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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.
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When does the Generator come on line?
56.4 % N2
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What five items are on in an electrical emergency?
ISIS, RMU1, RMU2, EICAS, Light on Compass.
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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.
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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.
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What needs to happen for all DC buses to be energized
- Either:
- At least three generators online
- GPU is on and connected
- One Gen is online and shedd buses to ovrd.
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What is on the Hot BATT BUses?
Fire extinguishers, Fuel and hydraulic shutoff valves, ELT, main door control, courtes lights and pressure refueling
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What is on the shedd buses?
Recirc Fans, Nose landing lights, coffee maker, and taxi lights
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