CAT Avionics and Electrical Systems 1 — Questions and Answers
Question 1: What does the acronym 'EFIS' stand for in aircraft avionics?
- Electronic Flight Information System
- Electronic Flight Instrument System (Correct answer)
- Enhanced Flight Instrument System
- Electrical Flight Instrument System
Correct answer: Electronic Flight Instrument System
EFIS stands for Electronic Flight Instrument System, which replaces traditional analog gauges with digital displays for flight data.
Question 2: What is the standard DC voltage used in most commercial and military aircraft electrical systems?
- 12V DC
- 24V DC
- 28V DC (Correct answer)
- 48V DC
Correct answer: 28V DC
28V DC is the aviation standard for aircraft DC electrical systems, as specified in MIL-STD-704 and related airworthiness standards.
Question 3: At what frequency do most aircraft AC electrical systems operate?
- 50 Hz
- 60 Hz
- 400 Hz (Correct answer)
- 800 Hz
Correct answer: 400 Hz
Aircraft AC systems operate at 400 Hz, which allows transformers and motors to be significantly smaller and lighter than 60 Hz ground-based equipment.
Question 4: What is the primary function of an Integrated Drive Generator (IDG) on a commercial aircraft?
- Controls fuel flow to the engines
- Converts AC power to DC power for avionics
- Produces constant-frequency AC power from variable engine speeds (Correct answer)
- Monitors hydraulic system pressure
Correct answer: Produces constant-frequency AC power from variable engine speeds
An IDG incorporates a Constant Speed Drive (CSD) to maintain 400 Hz AC output regardless of engine RPM fluctuations.
Question 5: Which data bus standard is used in modern aircraft such as the Boeing 787 for high-speed Ethernet-based avionics networking?
- MIL-STD-1553
- ARINC 429
- ARINC 664 (AFDX) (Correct answer)
- RS-232
Correct answer: ARINC 664 (AFDX)
ARINC 664 (AFDX – Avionics Full-Duplex Switched Ethernet) provides high-bandwidth, deterministic data networking used in the B787 and A380.
Question 6: Which navigation system uses a network of VHF ground-based transmitters to provide azimuth information to aircraft?
- GPS
- VOR (Correct answer)
- ADS-B
- TCAS
Correct answer: VOR
VOR (VHF Omnidirectional Range) uses ground station radio transmissions to provide magnetic bearing information to airborne receivers.
Question 7: What is the purpose of an aircraft Ground Fault Interrupter (GFI) circuit?
- To regulate generator output voltage
- To detect and interrupt unintended leakage currents flowing to the airframe (Correct answer)
- To monitor engine ignition systems
- To control navigation radio frequencies
Correct answer: To detect and interrupt unintended leakage currents flowing to the airframe
A GFI detects small leakage currents flowing to the airframe structure and interrupts the circuit to prevent shock hazards or fire.
CAT Avionics and Electrical Systems 1
What does the acronym 'EFIS' stand for in aircraft avionics?