Aeroplane Electrical Systems: Lights

Questions and Answers

What type of motor is used to rotate the reflector in a larger aircraft's anti-collision light?

Electric motor

What is the purpose of the reflective surface on the bulb in a rotating-bulb-type anti-collision light?

To cover approximately half the bulb surface

What is the source of power for a red strobe-type anti-collision light?

High-voltage power supply

Where are white collision-avoidance strobe lights typically mounted?

On the wingtips and tail Signup and view all the answers

What is the frequency of the flash from a white collision-avoidance strobe light?

50 to 80 times a minute Signup and view all the answers

When are white collision-avoidance strobe lights typically switched on and off?

Just before takeoff and after exiting the runway on landing Signup and view all the answers

What is the purpose of white collision-avoidance strobe lights?

To denote that the aircraft is in flight Signup and view all the answers

What is the visual range of the flash from a white collision-avoidance strobe light?

30 degrees above and below the aircraft horizon Signup and view all the answers

What is a characteristic of Level 2 knowledge in aircraft maintenance?

Ability to apply theoretical knowledge in practical situations Signup and view all the answers

What is the purpose of knowledge level indicators in aircraft maintenance licences?

To indicate the level of knowledge required for each category of licence Signup and view all the answers

What is the purpose of the Controlled Document notation in the training materials?

To indicate that the document is copyrighted Signup and view all the answers

What is the subject category that includes knowledge about electrical systems in aeroplanes?

Aeroplane Systems - Electrical Signup and view all the answers

What is a crucial consideration when working with strobe lights?

To avoid fuel leaks or vapour sources in the area Signup and view all the answers

Why should landing lights not be tested for an extended period on the ground?

Because they generate too much heat Signup and view all the answers

What is the purpose of the cam and micro-switch in some landing light extension systems?

To stop the actuator motor at pre-set positions Signup and view all the answers

What can cause a sealed beam to crack when replacing lamps?

Stressing the glass sealed beam unevenly Signup and view all the answers

What is the purpose of the parabolic reflector in some landing lights?

To focus the light beam Signup and view all the answers

What can happen to the filament in a sealed beam if it cracks?

It will burn out Signup and view all the answers

What is the purpose of the flap fairing in some landing light systems?

To extend or retract the landing light Signup and view all the answers

Why are sealed beams commonly used in landing lights?

Because most aircraft use them Signup and view all the answers

What triggers the illumination of the occupied sign and lavatory interior lighting in a lavatory advisory lighting circuit?

The plunger striking the micro switch in the door jamb Signup and view all the answers

What is the primary purpose of reading lamps in a passenger area?

To provide a restricted light in the reading area Signup and view all the answers

Where is the master switch for passenger reading lights typically located?

On the flight attendant panel Signup and view all the answers

What type of lighting is used in the flight compartment to illuminate controls and instruments?

White lighting Signup and view all the answers

How many main types of cockpit lighting are mentioned in the content?

5 Signup and view all the answers

What is the purpose of flight compartment lighting?

To illuminate controls and instruments with uniform intensity Signup and view all the answers

What type of lighting is used in older civil aircraft?

Red lighting Signup and view all the answers

How are some aircraft reading lights controlled?

Through electronic modules located under the seats Signup and view all the answers

What is the primary purpose of emergency lighting in an aircraft?

To provide light for the crew to operate emergency equipment and guide passengers to safety Signup and view all the answers

What is the typical location of the controls for emergency lights in an aircraft?

On the outside of the aircraft Signup and view all the answers

What is the purpose of the window at the bottom of emergency exit lights?

To illuminate the exit path Signup and view all the answers

What is the typical power source for emergency exit lights in modern aircraft?

Independent nickel cadmium battery pack Signup and view all the answers

What triggers the automatic switching of emergency exit lights to battery power?

Loss of aircraft power Signup and view all the answers

What is the role of the ICAO and civil aviation regulations in regards to emergency lighting?

To detail the intensity and position requirements for emergency lighting Signup and view all the answers

What is the purpose of the emergency lighting system in an aircraft?

To mark all exits and illuminate the cabin Signup and view all the answers

What is the typical location of emergency exit lights in an aircraft?

Adjacent to all emergency exits Signup and view all the answers

What is the primary source of air for anti-icing in a turbine aeroplane?

Compressor bleed air Signup and view all the answers

At what temperature does the thermal switch cause the shutoff valve to close?

85 °C (185 °F) Signup and view all the answers

What is the purpose of a test plug in an anti-icing system?

To test the system without operating the aircraft engines Signup and view all the answers

Where is the air used for airframe leading edge de-icing/anti-icing typically vented in most aircraft?

Through small holes located under the wing Signup and view all the answers

How are the shutoff valves in an anti-icing system actuated?

Pneumatically Signup and view all the answers

What is the purpose of mixing hot bleed air with ambient air in an anti-icing system?

To provide a consistent temperature for anti-icing Signup and view all the answers

What is the approximate temperature of the hot bleed air used in an anti-icing system?

177 °C (350 °F) Signup and view all the answers

What is the purpose of using an external source of air when performing an operational system check?

To test the system without operating the aircraft engines Signup and view all the answers

What is the purpose of spraying silicon on de-icer boots?

To give the rubber an extremely smooth surface to which ice cannot adhere Signup and view all the answers

How should oil and grease be removed from de-icer boots?

By scrubbing the surface of the boot lightly with a rag that is damp with white spirit or lead-free gasoline Signup and view all the answers

What is the most common type of damage that engineers encounter when maintaining de-icer boots?

Scuff damage Signup and view all the answers

What should be used to repair de-icer boot damage?

Approved parts supplied by BF Goodrich Signup and view all the answers

What is the purpose of the inspection of de-icer boots?

To check the surface of the boots for condition and security Signup and view all the answers

What should be referred to when making repairs to de-icer boots?

The manufacturer's maintenance manual Signup and view all the answers

What is included in the kit for repairing de-icer boots?

All of the above Signup and view all the answers

What should be done before starting the repair of de-icer boots?

The aircraft should be hangared and ground power and shop air made available Signup and view all the answers

What is the purpose of the autotransformer in the windshield temperature control system?

To provide two different output voltages for the windshield element Signup and view all the answers

What happens when the windshield temperature reaches 45 °C with the low heat setting?

The temperature controller breaks the current path to the coil of RL1 Signup and view all the answers

What is the purpose of the overheat thermistor in the windshield temperature control system?

To break the current path to the coil of RL1 when the temperature reaches 55 °C Signup and view all the answers

What is the purpose of the pitot static probe heater?

To prevent ice formation on the probe Signup and view all the answers

What type of material should be used to manufacture pitot static probe covers?

Cotton or canvas Signup and view all the answers

What happens when the temperature controller or the normal thermistor fails in the windshield temperature control system?

The temperature of the windshield can rise above 45 °C Signup and view all the answers

What is the voltage supplied to the pitot static probe strut on the ground?

115-V AC Signup and view all the answers

What is the purpose of the temperature controller in the windshield temperature control system?

To control the temperature of the windshield to 45 °C Signup and view all the answers

What is the purpose of the current sensors in the pitot static probe heater circuit?

To sense the operation of the heater Signup and view all the answers

What is the function of relay RL1 in the windshield temperature control system?

To connect the lower voltage to the windshield element when low heat is selected Signup and view all the answers

How can the heater's operation be checked on the ground?

Using the Central Maintenance Computer (CMC) Signup and view all the answers

What is the purpose of relays R7423 and R7425 in the pitot static probe heater circuit?

To control the power supply to the probe Signup and view all the answers

What happens to the power supply to the pitot static probe heater in flight?

Relay R7425 is de-energized Signup and view all the answers

What is the consequence of not having airflow over the heater?

The temperature of the heater may rise, causing damage Signup and view all the answers

What is the primary function of the converter in an aircraft windshield wiper system?

To change the rotary motion of the motor to the oscillating motion required by the wiper blade Signup and view all the answers

What is the purpose of the guide arm in an aircraft windshield wiper system?

To keep the wiper blade vertical and govern the wiper pattern Signup and view all the answers

What is the typical spring tension of an aircraft windshield wiper blade against the windshield?

4-1/2 pounds Signup and view all the answers

How is the wiper blade typically removed from the windshield wiper system?

By pulling on the top of the arm and compressing the pressure mechanism Signup and view all the answers

What is the purpose of the park position on a four-position selector switch in an aircraft windshield wiper system?

To park the wiper out of view when not in use Signup and view all the answers

What is the function of the pivot stud in an aircraft windshield wiper system?

To support the end of the guide arm Signup and view all the answers

What is the attachment point for the wiper blade in an aircraft windshield wiper system?

The drive arm Signup and view all the answers

What is the typical method of inserting the steel pin to remove the wiper blade from the windshield wiper system?

By pulling on the top of the arm and compressing the pressure mechanism Signup and view all the answers

What is an important aspect of applying knowledge in a practical manner?

Following manufacturer's instructions Signup and view all the answers

What happens to the armature when the strength of the magnetic field is increased?

It becomes harder to turn Signup and view all the answers

What is the purpose of the solenoid in a vibrating-type voltage regulator?

To electrically connect or remove the field rheostat from the circuit as the voltage varies Signup and view all the answers

What happens when the output voltage rises above a specified critical value in a vibrating-type voltage regulator?

Contact B opens Signup and view all the answers

What is the purpose of the dashpot P in a vibrating-type voltage regulator?

To act as a dampener to prevent hunting Signup and view all the answers

What is the effect of a weaker magnetic field on the armature?

It becomes easier to turn Signup and view all the answers

What is the purpose of the capacitor C across contact B in a vibrating-type voltage regulator?

To eliminate sparking Signup and view all the answers

What happens when contact B closes in a vibrating-type voltage regulator?

The field rheostat is shorted Signup and view all the answers

What is the primary function of a vibrating-type voltage regulator?

To maintain a constant output voltage Signup and view all the answers

What is the purpose of the trip coil in a Bus Tie Breaker?

To release the mechanical lock and open the main contacts Signup and view all the answers

What is a characteristic of a Bus Tie Breaker (BTB)?

It contains three heavy-duty contacts Signup and view all the answers

What is the function of the close coil in a Bus Tie Breaker (BTB)?

To close the main contacts Signup and view all the answers

What is the purpose of a Generator Circuit Breaker (GCB)?

All of the above Signup and view all the answers

What happens when power is removed from the close coil in a Bus Tie Breaker (BTB)?

The main contacts remain closed Signup and view all the answers

What is the purpose of the auxiliary contacts in a Bus Tie Breaker (BTB)?

To connect various control and indication circuits Signup and view all the answers

What is a characteristic of Bus Tie Breakers (BTBs), Generator Circuit Breakers (GCBs), and Bus Tie Contactors (BTCs) of the same part number?

They perform different functions within the electrical circuit Signup and view all the answers

What is the purpose of tripping the bus tie breaker in a Generator Circuit Breaker (GCB)?

To ensure the AC loads receive power from only one power source at any one time Signup and view all the answers

What is the primary function of a fuse link in a ceramic fuse?

To disconnect circuit current once predefined limits are exceeded Signup and view all the answers

Which type of fuse is designed to protect against hard faults?

Current limiter Signup and view all the answers

What determines the limits of a fusing link?

The size and composition of the fusing link Signup and view all the answers

What happens to the fusing link when the current limit is exceeded?

It melts or blows Signup and view all the answers

What is the purpose of the metal ferrules at each end of the cartridge fuse?

To make electrical connections Signup and view all the answers

Why is it important to replace a fuse with one of the same voltage and current rating?

To ensure the fuse provides adequate protection Signup and view all the answers

What is the purpose of the wire wound resistor in a slow-blow fuse?

To introduce a time delay Signup and view all the answers

What is the characteristic of a current limiter that distinguishes it from a fast-blow fuse?

It protects against hard faults Signup and view all the answers

What is the primary function of the thermal element in a thermal circuit breaker?

To distort and release the latch mechanism Signup and view all the answers

Why are circuit breakers and fuses typically located close to the power supply?

To protect the wiring run from short circuits and overloads Signup and view all the answers

What is the function of the mechanical latching mechanism in a thermal circuit breaker?

To release the main switch contacts when the thermal element distorts Signup and view all the answers

What happens when the thermal element distorts in a thermal circuit breaker?

The latch mechanism releases Signup and view all the answers

What is the purpose of labelling circuit breaker panels?

To show the circuits they protect Signup and view all the answers

What is the secondary function of circuit breakers and fuses?

To protect the component at the end of the wiring Signup and view all the answers

What is the characteristic of a thermal circuit breaker?

It uses a bimetallic strip to operate Signup and view all the answers

What happens when the current exceeds the circuit breaker's rating?

The temperature of the thermal element begins to build up Signup and view all the answers

If there is no inbuilt locking device, the battery connectors should be lockwired with what type of wire?

Copper wire 26 gague Signup and view all the answers

When removing a battery, which terminal should you disconnect first?

Negative Signup and view all the answers

When installing a battery, which terminal should you connect first?

Positive terminal Signup and view all the answers

What should you use to neutralize led acid batteries?

Baking soda Signup and view all the answers

When neutralizing Ni-Cad batteries, what should you use?

Chromic acid solution Signup and view all the answers

Why do light aircraft use DC alternators?

They are lighter and more efficient than AC generators. Signup and view all the answers

The newer CSD, containing hydraulic trim units and a differential assembly, converts the variable engine RPM to an alternator input speed of what?

12,000 RPM Signup and view all the answers

A normal operating temperature for the cooling oil in a Constant Speed Drive (CSD) is approximately what?

50 degrees Celsius Signup and view all the answers

What are the three main components of a three-unit regulator?

Voltage Regulator , current limiter, Revere current cutout Signup and view all the answers

What regulators can be used with generators that require a high field current?

Carbon pile regulator Signup and view all the answers

What is the purpose of an equalizing circuit?

To maintain equal voltage across multiple Generators? Signup and view all the answers

What is the timing of signals produced by a 400 Hz oscillator?

2.5 milliseconds per cycle Signup and view all the answers

What is a non-trip free circuit breaker?

A breaker that can be reset and override by holding in Signup and view all the answers

What is the most common type of circuit breaker?

A thermal trip free circuit breaker Signup and view all the answers

At what voltage does A/C over voltage protection typically operate?

130 volts+-3 Signup and view all the answers

What is the only protection for feeder cables?

Toroidal current Transformers Signup and view all the answers

What is the Merz price protection system?

A system used to stabilize electrical power supply in aircraft Signup and view all the answers

Why are plugs with different sized prongs used in DC power receptacles?

To prevent incorrect connections Signup and view all the answers

What is the purpose of the DC power receptacle interlock sensing?

Prevent arching to pins from plug when disconnected live Signup and view all the answers

How many pins does the AC plug have on aircraft?

6 pins Signup and view all the answers

What is the purpose of the two small pins on an AC plug?

Interlock sensing Signup and view all the answers

Generally, the worst continuous icing conditions are found near which of the following locations?

Heavy stratified clouds Signup and view all the answers

How is ice formed at high altitudes above 9,100 meters?

Cumulus clouds with updraughts Signup and view all the answers

What is the altitude range where icing occurs most frequently?

3700m to 4900m Signup and view all the answers

What is glazed ice?

smooth sheet of solid ice Signup and view all the answers

What is rime ice?

Brittle and frost-like Signup and view all the answers

What is mixed ice?

Hard rough conglomerate Signup and view all the answers

Pure rime ice is usually confined to which of the following?

High altostratus or altocumulus Signup and view all the answers

Clear ice is usually confined to which type of weather phenomenon?

Fog Signup and view all the answers

What type of ice can form in warm weather with no visible moisture present?

Carburettor ice Signup and view all the answers

What are the three types of electronic ice detection?

Pressure, Shave, Frequency Signup and view all the answers

What is the most commonly used ice detection system on modern aircraft?

Ice shave system Signup and view all the answers

In cold conditions, how often do the boots inflate and deflate?

Inflate for 6 seconds, deflate for 54 seconds Signup and view all the answers

In warm conditions, how often do boots inflate and deflate?

Inflate for 6 seconds, deflate for 2 minutes 54 seconds Signup and view all the answers

What is chemical deicing fluid typically made up of?

Water and Salt Signup and view all the answers

What controls the flow of device fluid?

Rheostat Signup and view all the answers

How hot is the air for anti-icing in aircraft?

177°C (350°F) Signup and view all the answers

When is leading edge ice turned off?

At an outside air temperature of 85°C (185°F) Signup and view all the answers

What color is the ice indicator in the flight compartment?

Blue Signup and view all the answers

What type of regulator is used for icing to maintain temperature?

Regulator with bimetallic spring coil Signup and view all the answers

What is the heating film made of in windows? (Select all that apply)

Stannic oxide Signup and view all the answers

What is the typical temperature difference of an aircraft window in cold and warm conditions?

Cold: -10°C, Warm: 20°C Signup and view all the answers

What should pitot probes be covered with?

Cotton/canvas Signup and view all the answers

What is the usual quantity of rain repellent fluid used in aeroplanes?

5 cubic centimeters of fluid Signup and view all the answers

What color are the navigation lights on the port side of an aeroplane?

Red Signup and view all the answers

What color is the navigation light on the starboard side?

Green Signup and view all the answers

What color are the tail navigation lights on an aeroplane?

White Signup and view all the answers

What angles should navigation lights be visible from for the wingtips and for the tail?

110 degrees for wingtips and 70 degrees for tail Signup and view all the answers

What angle above and below the horizon should anti-collision lights be visible?

30 degrees above and below Signup and view all the answers

How many flashes does an anti-collision light produce?

40 to 100 flashes Signup and view all the answers

How many times does the white anti-collision light typically flash?

50 to 80 times Signup and view all the answers

How long should you wait before performing maintenance on flashers?

5 minutes Signup and view all the answers

Why are quartz halogen globes used in taxi and landing lights?

They provide bright and focused illumination. Signup and view all the answers

what type of lights are used to laminate larger areas such as center consoles, floors, circuit-breaker panels and main instrument panels.

Flood lights Signup and view all the answers

Which of the following lights can be used in emergencies? (Select all that apply)

Wander or utility lights Signup and view all the answers

What type of battery is used in the emergency light system?

Hot battery bus Signup and view all the answers

What colors are warning and caution lights on an aeroplane?

Red and Amber Signup and view all the answers

Which of the following are warning light conditions? (Select all that apply)

Fire Signup and view all the answers

Study Notes

Category B1 Licence: Aeroplane Systems - Electrical - Lights

Knowledge Levels

Category A, B1, B2, and C Aircraft Maintenance Licence have different knowledge levels
Level 1: Familiarity with basic elements, simple description, and use of typical terms
Level 2: General knowledge of theoretical and practical aspects, ability to apply knowledge
Level 3: In-depth knowledge of complex systems, ability to analyze and troubleshoot

Rotating Bulb Type Anti-Collision Light

Uses two bulbs rotated by a small electric motor and gear train inside a red lens
Reflective surface on the bulb covers approximately half the bulb surface and is positioned with reflective surfaces back to back

Red Strobe Type Anti-Collision Light

Uses a high-intensity strobe light tube under a red lens instead of incandescent bulbs
Strobe unit located independently of the strobe light, powered by a high-voltage power source

White Collision-Avoidance Strobe Lights

Mounted on each wingtip, with some larger aircraft having a third light on the tail
Gives an extremely intense flash of white light for a very short period at a frequency of 50 to 80 times a minute
Visual from any point around the aircraft in an area 30 degrees above and below the aircraft horizon
Switched on just before take-off and switched off after exiting the runway on landing
Care must be taken to ensure no fuel leaks or vapour sources in the strobe light area

Landing Lights

Normally cooled by airflow during flight, care should be taken not to overheat them on the ground
Testing on the ground should be carried out quickly
Type of bulb used: pre-focused bulb placed in a parabolic reflector or a sealed beam
Most aircraft use sealed beams
When replacing lamps, tighten retaining fixtures evenly to avoid stressing the glass sealed beam

Landing Light Operations

Some landing lights extend to one position only, with a micro-switch and cam depressing the switch to stop the actuator motor
Another type of extension system can extend the landing light to two or more pre-set positions
System has more than one position on the landing light switch, for example, approach and landing

Passenger Reading Lights

Provide a restricted light in the reading area of a passenger
Some aircraft may have a master switch located on the flight attendant panel
Each light is individually switched, with the circuit powered from a circuit-breaker to individual switches and lights
Some aircraft reading lights are controlled from the passenger seats through electronic modules located under the seats

Flight Compartment Lighting

Has to be sufficient to illuminate all controls, switches, instruments, and panel inscriptions with uniform intensity
Five main types of cockpit lighting: integral lighting, post or pillar lights, trans-illuminated panels, floodlights, and utility or wander lights
Controls for these lights are usually located on the outside of the aircraft and, in some aircraft, are controlled by a micro-switch in the aircraft's landing gear

Emergency Lighting

Must mark all exits and illuminate the cabin with enough light for the crew to operate emergency equipment and guide passengers to safety
Intensity and position requirements of these lights are detailed in relevant ICAO and civil aviation regulations
Emergency exit lights are fitted adjacent to all emergency exits, indicating "exit" and using white light to illuminate the exit

De-icer Boot Maintenance and Repair

De-icer boot surfaces should be cleaned by lightly scrubbing with a rag dampened with white spirit or lead-free gasoline, and then wiped dry before the solvent can soak into the rubber.
Silicon is often sprayed on boots to give them an extremely smooth surface, preventing ice from adhering.
During inspection, check the boot surface for condition and security, and inspect the condition of plumbing fittings and lines/hoses.

Repair Schemes

The "cold patch repair" method is used to refurbish scuff damage, repair tube area damage, tears in the fillet area, and pin-hole damage.
Scuff damage is the most common type of damage encountered during de-icer boot maintenance.
Always refer to the manufacturer's maintenance manual for guidance on making appropriate repairs and follow approved repair processes explicitly.
Never use tyre patches on aircraft de-icer boots, even as a temporary repair.
Always use approved parts supplied by BF Goodrich, the principal manufacturer of de-icer boots and accessories.

De-icer Boot Repair Kit

The kit includes a scuffing pad, glue, a roller, a variety of large and small patches, and a tin of talcum powder.
Follow the maintenance manual for proper guidance on installing a patch on a de-icer boot tube.

Aircraft Anti-icing and De-icing System

The system uses heated air from the engine compressor to anti-ice and de-ice the leading edge.
The hot bleed air is mixed with ambient air and flows through passages next to the leading edge skin at approximately 177°C (350°F).
The system is electrically controlled and pneumatically actuated.
An operational system check can be carried out by using an external source of air.

Windshield Temperature Control

The system uses a three-phase, 200-V AC power source and an auto transformer to provide two output voltages.
The lower voltage is applied to the windshield element when low heat is selected, and the high voltage is applied when high heat is selected.
The temperature controller regulates the windshield temperature to prevent it from exceeding 45°C.

Pitot Static Probe Heater Circuit

Each main pitot-static probe is anti-iced by two electric heaters.
On the ground, with engines not operating, the probe heaters are not powered.
With any engine operating, relays R7423 and R7425 are energised, supplying 115-V AC power to the strut and head of the probe.

Windshield Wiper Circuit

A four-position selector switch is used to control the windshield wipers (off, park, slow, and fast).
The park position is a momentary switch, used to park the wiper out of view once it is no longer required.

DC Generator and Voltage Regulator

A DC generator produces a greater output voltage when the magnetic field is stronger, but it requires more force to turn the armature.
A weaker magnetic field makes it easier to turn the armature, but the output voltage is lower.
When the load on a generator increases, additional field current must be supplied to increase the voltage output, and more force is required to turn the armature.

Vibrating-Type Voltage Regulator

The regulator uses a solenoid to electrically connect or remove the field rheostat from the circuit as the voltage varies.
When the output voltage rises above a specified critical value, the solenoid's coil opens the contact, reducing the field current and lowering the output voltage.
When the output voltage falls below a certain value, the contact closes, shorting the field rheostat, and the terminal voltage starts to rise.

Bus Tie Breaker (BTB)

BTBs contain three heavy-duty contacts that connect three-phase power to the generator bus bars, distributing power to the aircraft AC loads.
They also contain auxiliary contacts used to connect various control and indication circuits within the AC distribution system.
Power supplied to the close coil causes the main contacts to close, and the auxiliary contacts change, locking the breaker in the closed position.

Generator Circuit Breaker (GCB)

The GCB connects the AC generator's output to its respective bus if the generator is serviceable.
It ensures that when the generator's output is connected to the generator bus, the bus tie breaker is tripped, allowing AC loads to receive power from only one power source at a time.
It isolates the generator's output from the aircraft's loads if a fault is detected by the generator control unit.

Fuses

Ceramic fuses are designed for use in areas where a spark from a blowing fuse could be a hazard, especially in combustible environments.
The fuse link connects to the mounting and is designed to disconnect circuit current once predefined limits are exceeded.
The limits are determined by the size and composition of the fusing link.
Once the current limit of the fusing link is exceeded, the heat generated by the current flowing through the fusing link will melt (or blow) the fusing link.

Current Limiter

A current limiter is a device that behaves more like a fusible link than a fast-blow fuse.
It is designed to protect against hard faults as opposed to continuous but small overloads.
The circuit breaker must be reset manually.

Thermal Circuit Breaker

A thermal circuit breaker uses a bimetallic strip to operate.
It consists of three major assemblies: bimetallic thermal element, contact-type switch unit, and mechanical latching mechanism.
When current exceeds the circuit breaker's rating, the temperature of the thermal element builds up, causing the thermal element to distort, the latch mechanism to release, and the main switch contacts to open.

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Description

This quiz covers the electrical systems of an aeroplane, focusing on lights. It's a vital topic for Category B1 licence holders.