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32 Cards in this Set
- Front
- Back
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In flight, aircraft power is provided by what?
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Engine driven 3-phase AC generators.
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On the ground, before and during engine start, what provides power?
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An APU or GPU.
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An APU also contains a large compressor for what purpose?
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To provide Air Conditioning on the ground, and bleed air for engine start.
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What purpose does a Ram Air Turbine (RAT) serve?
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Windmills in the free stream airflow to drive a small generator in an emergency.
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Most APU's are of what turbine design, and are they constant or variable speed?
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Single spool axial flow gas turbine. They operate at constant speed.
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Where is fuel for the APU is taken from, and how is it pumped?
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One of the aircraft main tanks. Normally by AC pump, but DC pump if AC unavailable.
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How were earlier APU's monitored?
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On instruments in the flight station.
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How are modern APU's monitored?
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Simplified control, with parameters shown on EICAS.
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How is a modern APU started?
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Switch to ON, arms battery and associated control circuits.
Switch to START, activates fuel pump and opens inlet door. Sequence starts automatically once the door is fully open. |
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What will cause an APU to automatically shutdown?
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1. Fire or Fault
2. Low Oil Pressure 3. High Oil Temperature 4. Overspeed 5. Duct Overheat. |
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Can an APU be remotely shutdown, and if so, from where?
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Yes, usually a panel located in the nose wheel well.
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Approximately how much power could a wide body jet potentially require?
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Up to 200 KW.
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Why is AC preferred over DC for large aircraft?
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Mainly due to weight and space saving. They are high voltage and low current.
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What is Voltage a measure of?
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The electromotive force causing a current to flow.
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What is Amps a measure of?
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The rate of current flow.
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What is Ohms a measure of?
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The rate of resistance in a circuit.
1 Ohm permits a flow of 1 Amp, when 1 Volt is applied. |
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Name the 3 different types of field windings?
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1. Series Wound. As load increases, V increases.
2. Shunt Wound. As load increases, V decreases. 3. Compound Wound. Makes use of both types to achieve constant voltage over range of loads. |
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What phase alternator do most aircraft electrical systems use?
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3-phase.
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What provides the initial excitation for the magnetic field in a generator?
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A Permanent Magnet Generator (PMG).
Normal PMG Voltage is about 85V. |
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How is a generator kept rotating at a constant RPM?
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By the use of a Constant Speed Drive.
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What is the industry standard frequency for AC power?
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400 Hz.
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On a standard Gen Drive Oil Temp gauge, what does rise refer to?
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The difference between Oil In and Oil Out temperature.
I.E. 80 in and 90 out = Rise of 10 |
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If a CSD is disconnected in flight, when can it be re-engaged?
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Only on the ground.
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What does KVAR stand for?
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Kilo-Volts-Amps-Reactive.
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kVA is a sum of what?
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kW + kVAR
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A Split Bus Electrical System is typically found on newer or older A/C?
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Newer.
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What is the other type of Bus System?
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Parallel Generator System.
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What is the purpose of a TRU?
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Converts 115v AC in 28v DC
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An static inverter serves what purpose?
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Converts main battery 28v DC into 115v AC
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What are the two most common types of aircraft battery?
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Lead-Acid & Nickel Cadmium
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If connected in Series, how are battery terminals joined?
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Negative to Positive.
Increases total V at a constant A. |
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Why are most batteries connected in parallel?
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Pos - Pos.
Increases total A, at a constant V. |
