40 Questions
What is the primary concern when handling lead acid batteries in aircraft?
All of the above
What is the purpose of a Transformer Rectifier Unit (TRU) in larger aircraft?
To generate DC power from AC sources
What is the recommended action when electrolyte is spilled during battery servicing?
Neutralize it with bicarbonate of soda
Why are DC alternators used in modern light aircraft?
They are lighter than AC generators
What is the purpose of an auxiliary battery in an aircraft?
To provide backup power in case of main system failure
What is the recommended neutralizing agent for Ni-Cad battery spills on an aircraft?
Chromic acid solution
What is the purpose of fitting an insulator plug/cap onto the terminal connector?
To prevent short circuits
What is the primary function of a DC three-unit regulator?
To regulate DC voltage
What is the primary source of electric power in transport-category aircraft?
AC power systems
What is the purpose of a ventilation system in an aircraft battery?
To ventilate explosive gases
What is the function of a generator circuit breaker?
To protect the generator from overcurrent
What is the purpose of a Constant-Speed Drive (CSD) in an aircraft?
To maintain a constant output rpm with a variable input rpm
What type of alternators are commonly used in most aircraft applications?
Three-phase alternators
What is the purpose of a bus tie breaker?
To connect two electrical buses together
Why are AC power systems preferred over DC power systems in aircraft?
AC systems produce more power per weight of equipment
What is the function of an inverter in an aircraft electrical system?
To convert DC power to AC power
What is the purpose of a Merz-Price protection system?
To detect and isolate feeder faults
What is the purpose of a rectifier in an aircraft electrical system?
To convert AC power to DC power
What is the function of a switched reverse current relay?
To prevent reverse current flow in the electrical system
How many main AC power sources are typically found in an aircraft electrical power system?
Four
What type of drive is used to drive the engine-driven generators on a turbine-powered aircraft?
Constant Speed Drive
What is the purpose of a relay in an aircraft electrical system?
To switch high-current circuits on and off
What is the purpose of an Auxiliary Power Unit (APU) and Ram Air Turbine(RAT)generator in an aircraft?
To provide emergency power to the aircraft
What is the function of a constant-speed drive system?
To regulate the speed of the AC generator
What is the purpose of the harmonic filter in a static inverter?
To remove everything that is not 400 Hz
What is the function of the regulator circuit in a static inverter?
To maintain the correct voltage and frequency
What is the advantage of miniaturisation of electronic components in static inverters?
Relatively small and lightweight
What is the principle behind the operation of a transformer?
Mutual inductance
What is the purpose of the 400 Hz oscillator in a static inverter?
produces signals with the correct timing, which is 2.5 mS
What should be done with a static inverter that requires repair?
Send it to an approved facility
What is the output of the pulse shaper and power driver in a static inverter?
A 400 Hz square wave
What is the function of the output stage/final filter in a static inverter?
To condition the signal for use
What is the output of the full wave rectification of a 400 Hz, three-phase AC?
A DC voltage with a ripple frequency of 2400 Hz
What is the phase relationship between the input and output of a star-to-star transformer?
In phase
What is the output of the parallel rectified outputs of the two secondary windings?
A DC voltage with a ripple frequency of 4800 Hz
What is the primary function of the body or case in a fuse?
To hold the fuse together
What is the typical material used for the body or case in a fuse?
Glass
What is the advantage of using a glass body in a fuse?
It allows easy identification of a blown fuse
What is the purpose of the mounting in a fuse?
To provide a means of connecting the fuse to the circuit
What is the cheapest and most simple form of protection for electronic circuit?
Fuse
Study Notes
Electrical Power System
- An electrical power system is a critical component of an aircraft, providing power to various systems and instruments.
- The system consists of power generation, power distribution, and circuit protection.
Aeroplane Batteries
- Batteries are used as a backup power source in aircraft electrical systems.
- Lead acid batteries are commonly used in aircraft and require regular maintenance, including electrolyte level checks and terminal cleaning.
- Nickel-Cadmium (Ni-Cad) batteries are also used in some aircraft and require special handling and maintenance.
- Battery servicing should be performed with caution to avoid acid or alkaline burns.
DC Power Generation
- DC power is used in light aircraft, where a relatively small amount of electric power is required.
- DC alternators are used to produce electric power in light aircraft, generating an AC voltage that is then converted to DC using internal rectifiers.
- On larger aircraft, DC power is generated by Transformer Rectifier Units (TRUs) that convert engine-driven AC power to 28-V DC.
AC Power Generation
- AC power is the primary source of electric power in most commercial aircraft.
- AC generators (alternators) are used to produce electric power, and rectifiers are used to convert AC to DC where needed.
- AC power systems are more efficient than DC systems, but require a constant-speed drive to maintain a constant frequency.
- AC generators are classified by voltage, amperage, phase, power output, and power factor.
Power Distribution Systems
- Electrical bus systems are used to distribute power throughout the aircraft.
- Basic DC generation bus systems, twin-engine split DC bus systems, and twin-engine split AC bus systems are used in different aircraft applications.
- Relays, breakers, and contactors are used to control power distribution in aircraft electrical systems.
Inverters, Transformers, and Rectifiers
- Inverters are used to convert DC power to AC power, and are typically used in aircraft electrical systems.
- Transformers are used to change AC voltage and current levels, and are commonly used in aircraft electrical systems.
- Rectifiers are used to convert AC power to DC power, and are used in conjunction with transformers to generate DC power.
Circuit Protection
- Fuses are a simple and inexpensive form of circuit protection, used to prevent electrical overloads and short circuits.
- Current limiters, circuit breakers, and switched reverse current relays are also used to protect aircraft electrical circuits.
- Overvoltage protection, differential/feeder fault protection, and Merz-Price protection systems are used to protect against electrical faults and overloads.
This quiz covers the electrical power system of an aeroplane, including its components and functions. It is part of the CASA Part 66 training materials.
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