Aircraft Electrical Systems: Maintenance and Troubleshooting
1. Resistance Measurement
A resistance measurement of 0.005 ohms from a ground point of a battery to the ground terminal or ground point of a generator of an electrical device is considered satisfactory.
2. Ammeter Overload
An ammeter can be “redlined” at 100% of the alternator rating and is referred to as overload.
3. Electrical Connector Pin Side
The negative (-) connection is the pin side of an AN or MS electrical connector.
4. Bonding Terminals to Terminal Block (No Bus Bar)
When using a stud/nut combination for bonding terminals to a terminal block, the number of terminals should be limited to four (with no bus bar or jumper strip).
5. Bonding Terminals to Terminal Block (With Bus Bar)
When using a stud/nut combination for bonding terminals to a terminal block, the number of terminals should be limited to four (with a bus bar or jumper strip installed).
6. Brush Tension
Heavy spring tension on brushes can cause excessive wear, and light tension can cause arcing or bouncing.
7. Carbon-Pile Voltage Regulator
If the pressure on the carbon pile of a carbon-pile voltage regulator is reduced, the resistance will be increased.
8. Flashing the Field
Flashing the field is the term used to describe what is done if field coils lose their residual magnetism.
9. Armature Reaction
Armature reaction is proportional to the current flowing in the armature coils.
10. Armature Reaction Compensation
Overcoming armature reaction in generators or motors is done with interpoles or compensation windings.
11. DC Generator Field Wiring
The method of wiring the field to the armature is found in series, shunt, or compound wound DC generators.
12. Common DC Generator Type in Small Aircraft
The most common type of DC generator in small aircraft is the shunt wound type.
13. Alternator Output Control
Varying the field strength is the easiest way to control alternator output.
14. Commutator and Brush Assembly Function
The main function of the commutator and brush assembly in a DC generator is to change AC to DC.
15. FAR 23 Requirements
Per FAR 23, aircraft are required to have a voltmeter or ammeter in view of the flight crew.
16. Solenoid vs. Relay
The difference between a solenoid and a relay is that a solenoid has a movable core, and a relay has a movable switch.
17. Three-Phase Alternator Stator Windings
Delta and wye are the two configurations of stator windings in a three-phase alternator.
18. Commutator and Slip Ring Repair
#000 grit sandpaper is used to repair slight surface imperfections to the commutator and slip rings.
19. Residual Magnetism
Residual magnetism is the magnetic force that remains after an electric current is removed from a field coil.
20. Conductor Cross-Section and Resistance
If a conductor of twice the cross-section area is used for aircraft wiring, the resistance will be half.
21. DC Generator Residual Magnetism
DC generators’ residual magnetism remains in the field with no current flowing.
22. Solid-State Voltage Regulator
A solid-state voltage regulator will control the field circuit by opening or closing a ground path for the circuit.
23. Switch Derating Factor Example
Example: A switch installed in a 12-volt motor circuit that draws 10 amps of current, if the switch has a derating factor (DF) of 2, is 20.
24. Lacing Wire Bundles
When lacing wire bundles, the single-cord method is used on bundle sizes under 1 inch in diameter.
25. AC 43.13-1B Wire Bundle Routing
AC 43.13-1B suggests that when routing wire bundles for electrical systems of aircraft, the bends should not be less than 10 times the diameter of the largest wire.
26. Aluminum Wire Substitution
When substituting aluminum wire for copper, wire sizes smaller than #8 should not be used.
27. Four-Pole AC Generator Speed for 400 Hz
Example: What speed must a four-pole AC generator turn to produce 400 Hz AC? 12,000 RPM.