AMT Aircraft Electrical Systems 2 — Questions and Answers
Question 1: What is the purpose of a bus bar in an aircraft electrical system?
- To convert AC to DC power
- To distribute electrical power to multiple circuits from a common point (Correct answer)
- To regulate voltage output from the generator
- To store electrical energy for emergency use
Correct answer: To distribute electrical power to multiple circuits from a common point
A bus bar serves as a common distribution point that connects the power source to multiple branch circuits throughout the aircraft.
Question 2: A constant-speed drive (CSD) on an aircraft generator is used to:
- Vary the output voltage based on load
- Maintain a constant generator RPM regardless of engine speed (Correct answer)
- Regulate current output during peak demand
- Convert mechanical energy to hydraulic pressure
Correct answer: Maintain a constant generator RPM regardless of engine speed
The CSD maintains a constant generator input speed so the generator produces a stable AC frequency (typically 400 Hz) regardless of engine throttle setting.
Question 3: Which type of wire insulation is most resistant to high temperatures in an aircraft engine compartment?
- PVC (polyvinyl chloride)
- Nylon
- PTFE (polytetrafluoroethylene) (Correct answer)
- Rubber
Correct answer: PTFE (polytetrafluoroethylene)
PTFE (commonly known as Teflon) offers excellent high-temperature resistance and is widely used in engine compartment wiring where thermal stress is significant.
Question 4: What does the term 'electrical bonding' mean in aircraft maintenance?
- Connecting multiple batteries in series
- Ensuring all metallic parts are at the same electrical potential (Correct answer)
- Insulating wiring from the airframe structure
- Applying dielectric grease to terminal connections
Correct answer: Ensuring all metallic parts are at the same electrical potential
Electrical bonding connects all metallic components to a common ground potential to prevent static charge buildup and reduce EMI.
Question 5: In a 28-volt DC aircraft system, what minimum voltage at the battery indicates a fully charged state?
- 24.0 volts
- 25.5 volts
- 28.0 volts (Correct answer)
- 26.5 volts
Correct answer: 28.0 volts
A fully charged 28V aircraft battery should read approximately 28 volts at rest; readings below this indicate a partial or discharged state.
Question 6: A circuit breaker that 'trips' repeatedly under normal load conditions most likely indicates:
- The breaker is the wrong amperage rating
- A short circuit or overload in the downstream circuit (Correct answer)
- The bus bar voltage is too high
- The generator is producing excessive current
Correct answer: A short circuit or overload in the downstream circuit
Repeated tripping under normal load points to a fault — typically a short circuit or a component drawing more current than the circuit is designed to handle.
Question 7: Which instrument is used to measure insulation resistance of aircraft wiring?
- Ammeter
- Voltmeter
- Megohmmeter (megger) (Correct answer)
- Wattmeter
Correct answer: Megohmmeter (megger)
A megohmmeter applies high voltage (typically 500V or 1000V) to test wiring insulation integrity, measuring resistance in megohms.
AMT Aircraft Electrical Systems 2
What is the purpose of a bus bar in an aircraft electrical system?