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25 Cards in this Set
- Front
- Back
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Why must a switch be derated if it is used in a circuit that supplies incandescent lamps?
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The high–inrush current caused by the low resistance of the cold filaments requires that the switches be derated.
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What is an SPDT switch?
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A single–pole, double–throw switch.
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Where could you find the part number of a switch in an aircraft electrical system?
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In the equipment table of bill of materials on the electrical circuit diagram for the aircraft.
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If no specific instructions are available, which way should the operating handle of an electrical switch move to turn a component on?
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Forward or upward.
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What is meant by a trip–free circuit breaker?
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A circuit breaker that cannot be closed while a fault exists, regardless of the position of the operating handle.
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What is meant by a slow–blow fuse?
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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.
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What is the function of a fuse or circuit breaker in an aircraft electrical circuit?
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It protects the wiring from an excess of current. It will open the circuit if enough current flows to heat the wire until the insulation begins to smoke.
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What are two principles upon which circuit breakers operate?
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Magnetic circuit breakers open a circuit when the current creates a strong enough magnetic field. Thermal circuit breakers open a circuit when the current causes enough heat.
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What circuit in an aircraft electrical system is not required to have a circuit protective device?
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The main circuit for starter motors, used during starting only.
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Is an automatic–reset circuit breaker approved on aircraft electrical circuits?
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No, a manual operation is needed to restore service after the circuit breaker has tripped.
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What two things must you take into consideration when selecting the wire size to use in an aircraft electrical system installation?
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The current carrying capability of the wire and the voltage drop caused by the current flowing through the wire.
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What is the maximum number of wires that should be connected to any single stud in a terminal strip?
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Four.
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How is a wire bundle protected from chafing where the bundle goes through a hole in a fuselage frame or bulkhead?
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The edges of the hole are covered with a flexible grommet, and the bundle is secured to the structure with a cushioned clamp.
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What kind of clamp is used to secure a wire bundle to the aircraft structure?
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A cushioned clamp.
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Why are solderless splices usually better than soldered splices in the wiring of an aircraft electrical system?
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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.
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What is the main disadvantage of aluminum wire over copper wire for use in an aircraft electrical system?
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Aluminum wire is more brittle than copper. It is more subject to breakage when it is nicked or when it is subjected to vibration.
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What size aluminum wire would be proper to replace a piece of four–gage copper wire?
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Two–gage. When you substitute aluminum wire for copper wire, use a wire that is two gage numbers larger.
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What is the smallest size aluminum wire that is approved for use in aircraft electrical systems?
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Six–gage.
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What color insulator on a preinsulated solderless connector indicates that the connector is proper for a 10–gage wire?
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Yellow.
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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?
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When monitoring 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.
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What is meant by "flashing" the field of a generator?
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Restoring the residual magnetism to the frame of the generator. This is done by passing battery current through the field coils in the direction it normally flows when the generator is operating.
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What is meant by paralleling the generators in a multi–engine aircraft?
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Adjusting the voltage regulators so all the generators share the electrical load equally.
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What are three types of voltage regulators used with aircraft generators?
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Vibrator–type, carbon–pile type, and solid state–type.
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How does a vibrator–type voltage regulator maintain a constant voltage?
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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.
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What two components are normally housed with a vibrator voltage regulator in a single–unit generator control?
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A current limiter and a reverse–current cutout relay. |
