1. Lesson 10: Aircraft Electrical Systems

2. Aircraft Electrical Systems
A circuit must have at least three parts.

3. Aircraft Electrical Systems
A circuit must have at least three parts.
The source

4. Aircraft Electrical Systems
A circuit must have at least three parts.
The source
The electron transportation and distribution system

5. 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)

6. 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.

7. Series And Parallel Circuits
A portion of the electrons flow through each filament.
The amount of voltage drop is equal to the total voltage produced by the source.

8. Voltage And Current Measuring Instruments
Current and voltage are the most commonly measured variables.
Voltmeters
Ammeters

9. Voltage And Current Measuring Instruments
Voltmeters (Parallel)
Measures current but indicates values of voltage.
Indicates electrical system condition.

10. 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.

11. The Aircraft Electrical System

12. The Aircraft Electrical System
Source
12 volt battery with the negative terminal connected to the airframe (negative ground).
Master solenoid
Master switch

13. 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.

14. 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.

15. 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.

16. 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).

17. Ignition Systems

18. Battery Ignition System

19. 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

20. Rotating Magnet Magneto

21. Rotating Magnet Magneto
Resultant Flux (E-gap)
Maximum current is flowing several degrees after neutral.

22. Rotating Magnet Magneto

23. Rotating Magnet Magneto
Dual Magnetos
High-tension Magnetos
Low-tension Magnetos

24. High-tension Magneto

25. Low-tension Magneto

26. 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

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

28. Impulse coupling

29. Vibrator starting system “Shower of Sparks”
Pulsating DC from the induction vibrator is directed into the magneto coil.