AET AET Aircraft Power Systems 2 — Questions and Answers
Question 1: Which type of aircraft battery is most commonly used in modern general aviation aircraft due to its maintenance advantages?
- Nickel-cadmium (NiCd)
- Lead-acid (flooded cell)
- Sealed absorbed glass mat (AGM) lead-acid (Correct answer)
- Lithium-ion
Correct answer: Sealed absorbed glass mat (AGM) lead-acid
Sealed AGM lead-acid batteries are widely used in general aviation because they are maintenance-free, spill-proof, and do not require water additions like flooded-cell batteries.
Question 2: What is the primary advantage of nickel-cadmium (NiCd) batteries used in turbine-powered aircraft over lead-acid batteries?
- Lower cost
- Higher energy density per pound
- More stable voltage during discharge and better high-current performance (Correct answer)
- Easier disposal requirements
Correct answer: More stable voltage during discharge and better high-current performance
NiCd batteries maintain a relatively flat discharge voltage and deliver high cranking currents reliably, making them preferred for turbine engine starts and emergency power in transport aircraft.
Question 3: An aircraft inverter converts aircraft DC power into AC power primarily to supply which type of equipment?
- DC motors and actuators
- AC-powered instruments and avionics that require 115V 400 Hz AC (Correct answer)
- Engine ignition systems
- Landing lights
Correct answer: AC-powered instruments and avionics that require 115V 400 Hz AC
Inverters convert 28V DC bus power to 115V 400 Hz AC to power AC instruments, gyros, and some avionics in aircraft that do not have AC generators.
Question 4: What does the term 'load shedding' mean in the context of aircraft electrical power management?
- Increasing generator output during peak demand
- Disconnecting non-essential electrical loads to reduce demand on a degraded power source (Correct answer)
- Balancing load between two generators
- Testing circuit breakers sequentially
Correct answer: Disconnecting non-essential electrical loads to reduce demand on a degraded power source
Load shedding involves selectively disconnecting non-essential electrical consumers to reduce the demand on a power system operating in a degraded or emergency condition.
Question 5: A ground power unit (GPU) is connected to an aircraft for maintenance. What precaution must be taken before connecting the GPU to avoid damage to avionics?
- Ensure all avionics master switches are ON
- Verify GPU voltage and polarity match aircraft requirements before connecting (Correct answer)
- Run the aircraft engine simultaneously
- Set all transponders to STANDBY mode only
Correct answer: Verify GPU voltage and polarity match aircraft requirements before connecting
Before connecting a GPU, technicians must verify that the GPU output voltage and polarity are correct for the aircraft system to prevent damage to sensitive avionics and electrical components.
Question 6: In a twin-engine aircraft with two generators, what component automatically connects both generators to share the electrical load?
- Voltage regulator
- Bus tie relay (BTR) or bus tie breaker (Correct answer)
- Current transformer
- Load controller unit
Correct answer: Bus tie relay (BTR) or bus tie breaker
A bus tie relay (BTR) or bus tie breaker connects the two main AC or DC buses together, allowing both generators to share the total electrical load equally.
AET AET Aircraft Power Systems 2
Which type of aircraft battery is most commonly used in modern general aviation aircraft due to its maintenance advantages?