Lesson 10: Aircraft Electrical Systems

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Lesson 10 Aircraft Electrical Systems
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Aircraft Electrical Systems

• A circuit must have at least three parts.

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Aircraft Electrical Systems

• A circuit must have at least three parts.
• The source

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Aircraft Electrical Systems

• A circuit must have at least three parts.
• The source
• The electron transportation and distribution
  system

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Aircraft Electrical Systems

• A circuit must have at least three parts.
• The source
• The electron transportation and distribution
  system
• The load (Where the work is done)

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Series And Parallel Circuits

• Series Circuit
• All electrons must flow through all active
  components.
• The amount of voltage dropped across the filament
  is always less than the total.
• Voltage drop depends on the amount of resistance
  of the individual load.

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Series And Parallel Circuits

• Parallel Circuit
• A portion of the electrons flow through each
  filament.
• The amount of voltage drop is equal to the total
  voltage produced by the source.

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Voltage And Current Measuring Instruments

• Current and voltage are the most commonly
  measured variables.
• Voltmeters
• Ammeters

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Voltage And Current Measuring Instruments

• Voltmeters (Parallel)
• Measures current but indicates values of voltage.
• Indicates electrical system condition.

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Voltage And Current Measuring Instruments

• Ammeters
• Measures current flow
• Battery is charging when electrons are flowing
  from the positive terminal.
• This would be a positive indication.

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The Aircraft Electrical System
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The Aircraft Electrical System

• Source
• 12 volt battery with the negative terminal
  connected to the airframe (negative ground).
• Master solenoid
• Master switch

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The Aircraft Electrical System

• The Starter Circuit
• Starter switch circuit (control circuit)
• Starter solenoid circuit (motor circuit)
• The master switch/solenoid circuit must also be
  connected.

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The Aircraft Electrical System

• The Busbar
• Rigid point that is a convenient place to
  terminate many wires neatly and safely.
• Connected to the positive terminal of the
  battery, when the master switch is on.
• Same electrical potential as the battery.
• Circuit breakers are often mounted.

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The Aircraft Electrical System

• The Alternator
• The alternator switch completes a circuit to the
  voltage regulator.
• The voltage regulator samples the system voltage
  and increases or decreases the field voltage
  which limits alternator output.

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The Aircraft Electrical System

• Ammeters And Loadmeter In The Circuit
• Installed between the master solenoid and the
  busbar.
• Senses the amount and direction of current flow
  in the battery circuit.
• Installed between A terminal of the alternator
  and the busbar.
• Senses current flow (in one direction), or
  output, of the alternator (loadmeter).

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Ignition Systems
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Battery Ignition System
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Magnetos

• Completely independent of the electrical system
  of the airplane.
• Primary current is interrupted by a set of
  breaker points, and high voltage for the spark
  plugs comes from the voltage step-up in the
  magneto coil.
• Rotating Magnet Magneto

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Rotating Magnet Magneto
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Rotating Magnet Magneto

• Resultant Flux (E-gap)
• Maximum current is flowing several degrees after
  neutral.

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Rotating Magnet Magneto
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Rotating Magnet Magneto

• Dual Magnetos
• High-tension Magnetos
• Low-tension Magnetos

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High-tension Magneto
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Low-tension Magneto
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Rotating Magnet Magneto

• Aids To Starting
• Magnetos provide a good, hot spark at idle, at
  cruise, and at high speed.
• But not when the engine is turning slowly during
  start.
• Impulse Coupling

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Impulse coupling

• A small spring-loaded coupling between the
  magneto shaft and the engine drive gear.

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Impulse coupling
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Vibrator starting systemShower of Sparks

• Pulsating DC from the induction vibrator is
  directed into the magneto coil.