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Why must a switch be derated if it is used in a circuit that supplies incandescent lamps?
the high inrush current caused by the low resistance of the cold filaments requires that the switches be derated
What is a SPDT switch?
A single-pole, double-throw switch.
Where could you find the part number of a switch in an aircraft electrical system?
In the equipment table or bill of materials on the electrical circuit diagram for the aircraft.
What is meant by a trip-free circuit breaker?
A circuit breaker that cannot be closed while a fault exists, regardless of the position of the operating handle.
What is meant by a slow blow fuse?
A fuse that will allow more current than its rating to flow for a short period of time but will open the circuit if more than its rated current continues to flow.
What is the function of a fuse or circuit breaker in a aircraft electrical circuit?
It protects the wiring from an excess of current.  it will open the circuit when the current creates enough current flows to heat the wire until the insulation begins to smoke.
What are the two principles upon which the circuit breakers operate?
Magnetic circuit breakers open a circuit whent he current creates a stong enough magnetic filed.  Thermal circuit breakers open a circuit when the current causes enough heat.
What circuit in an aircraft electrical system is not required to have a circuit protective device?
the main circuit for starter motos, used during starting only.
What size generator must be used in an aircraft electrical system if the connected electrical load is 30 amps, and there is no way of monitoring the generator output?
When mounting is not practical, the total continuously connected electrical load must be no more than 80% of the rated generator output.  This would require a generator with a rating of 37.5 amps.  Practically, a 40 amp generator would be installed.
Is the automatic-reset circuit breaker approved for aircraft electrical circuits?
No, a manual operation is needed to restore service after the circuit breaker has tripped.
What is meant by flashing the field of a generator?
Restoring the residual magnetism to the frame of the generator.  This is done by passing battery current throught the field coils in the direction it normally flows whent he generator is operating.
What is meant by paralleling the generators in a multi-engine aircraft?
Adjsuting the voltage regulators so all the generators share the electrical load equally
What are the 3 types of voltage regulators used with aircraft generators?
Vibrator type, carbon pile, and solid state
What 2 things must you take into consideration when selecting the wire size to use in an aircraft elec system installation?
The current carrying capacity of the wire and the voltage drop caused by the current flowing through the wire.
How does a vibrator type voltage regulator maintain a constant voltage?
When the voltage rises above the desired value, an electromagnetic relay opens and inserts a resistor in the generator field circuit, decreasing the field current and lowering the generator output voltage.
What is the maximum number of wires that should be connected to any single stud in a terminal strip?
What two components are nomally housed with a vibrator voltage regulation is a three-unit control panel?
a current limiter and a reverse current cutout relay.
What color insulator on a preinsulated solderless connector indicates that the connector is proper for a 10 gage wire?
What is the smallest size aluminum wire that is approved for use in aircraft electrical systems?
6 gage
What size aluminum wire woudl be proper to replace a piece of four gage copper wire?
two-gage.  when you substitute aluminum wire for copper wire, use a wire that is two gage number larger
How is wire bundle protected form chafing whre the bundle goes through a hole in the fusleage frame or bulkhead?
The edges of the hole are covered witha flexible grommet, ad the bundle is secured to the structure with cushioned clamp.
What is the main disadvantage of aluminum wire over copper wire for use in an aircraft electrical system?
Aluminum wire is more brittle than copper.  It is more subject to breakage when it is nicked or when it is subjected vibration.
What kind of clamp is used to secure a wire bundle to the aircraft structure?
A cushioned clamp.
Why are solderless splices usually better than solder splices in the wiring of an aircraft electrical system?
Soldered joints are usually stiff, and vibration can harden the wire and cause it to break.  Solderless splices are designed to keep the joint flexible so vibration cannot cause the wire to break.
When should the brushes ina starter motor be replaced?
When they have worn to one half of their original length.
How is the direction of a DC electrical motor reversed?
Reverse the polarity of the armature or the field, but not both.
What is used as the rectifier to produce direct current in a DC generator?
Brushes and a commutator.
What is used as the rectifier to produce direct current in an DC alternator?
Six solid state diodes.
Is a starter motor series wound or shunt wound?
Series wound for maximum stalled rotor weight.
What are two ways wires can be attached to the pins in a cannon plug?
1. by soldering the wires into pots on the pins and sockets.
2. By crimping tapered pins onto the wires and inserting the pins into tapered holes in the pins and sockets.
Why is stranded wire used rather than solid wire in most powerplant electrical systems?
Solid wire is likely to break when it is subjected to vibration.
what two things must be considered in selection of wire size when making an electrical installation in an aircraft?
The current carrying capability of the wire, and the voltage drop caused by current flowing through the wire.
What must be done to a DC generator, after it has been overhauled, before it can produce electricity?
The field must be flashed to restore residual magnetism to the field frame so it can begin to produce current.
Why is it not necessary to flash the field of a DC alternator after it has been overhauled?
An alternator field is exicited by battery current and residual voltage is not used to start the alternator producing current.
How are electrical wires protected where they pass through an area of high temp?
Wires passing through these areas are insulated with high-temp insulation, and the wires are enclosed in some type of protective conduit.
What is the minimum seperation allowed between a wire bundle and a fluid line that carries combustible fluid or oxygen?
Which aircraft electrical circuit does not normally contain a fuse or circuit breaker?
The starter motor circuit.
What is a starter-generator?
A single, engine-mounted component that serves as a starter for starting the turbine engine.  when the engine is running, the circuitry automatically shifts so it acts as compound wound generator.
When should aircraft wiring be installed in conduit?
When wiring passes through an area in the aircraft where open wiring could likely be damaged, such as through a wheel well.
What is meant by a trip-free circuit breaker?
A circuit breaker that opens a circuit any time an excessive amount of current flows, regardless of the position of the circuit breaker's operating handle.
Which way should the toggle of a switch that controls the propeller pitch move to place the propeller in low pitch (high RPM)?
Why are protective covers placed over some switches in an aircraft electrical circuit?
To prevent the switch from being inadvertently actuated.
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