AET Technical Knowledge and Skills 3 — Questions and Answers
Question 1: HF radio communication in aviation typically operates in which frequency range?
- 118–137 MHz
- 2–30 MHz (Correct answer)
- 960–1215 MHz
- 108–118 MHz
Correct answer: 2–30 MHz
HF (High Frequency) communication systems operate between 2 and 30 MHz, providing long-range voice and data communication via ionospheric skip propagation.
Question 2: Under FAA regulations, who is authorized to approve avionics maintenance work for return to service on a certificated aircraft?
- Any FAA-certificated mechanic
- An FAA-certificated repairman with appropriate ratings or an A&P mechanic with IA (Correct answer)
- Only an FAA-certificated repairman with an avionics rating
- Any person supervised by a licensed engineer
Correct answer: An FAA-certificated repairman with appropriate ratings or an A&P mechanic with IA
Return-to-service approval for avionics maintenance requires a certificated repairman with appropriate ratings or an Airframe & Powerplant mechanic holding an Inspection Authorization (IA).
Question 3: An ELT (Emergency Locator Transmitter) certified to TSO-C126 transmits on which frequency?
- 121.5 MHz only
- 406 MHz and 121.5 MHz (Correct answer)
- 243.0 MHz only
- 406 MHz only
Correct answer: 406 MHz and 121.5 MHz
TSO-C126 406 MHz ELTs transmit a digital distress signal on 406 MHz for satellite detection and a homing signal on 121.5 MHz for local search-and-rescue crews.
Question 4: ACARS (Aircraft Communications Addressing and Reporting System) primarily uses which communication medium for airborne data link?
- HF voice channels
- VHF Data Link (VDL) or SATCOM (Correct answer)
- ATC radar secondary surveillance
- DME interrogation/reply channels
Correct answer: VHF Data Link (VDL) or SATCOM
ACARS uses VHF Data Link (typically 129.125 MHz and others) for short-range digital messaging and SATCOM for oceanic areas beyond VHF coverage.
Question 5: An airborne weather radar system operating in X-band operates at approximately:
- 1 GHz
- 9.3–9.5 GHz (Correct answer)
- 3 GHz
- 35 GHz
Correct answer: 9.3–9.5 GHz
Airborne weather radar X-band systems operate at approximately 9.3–9.5 GHz, which provides good precipitation detection while keeping antenna size manageable.
Question 6: TCAS II issues Resolution Advisories (RAs) by coordinating with the intruder aircraft via:
- VHF voice communication
- Mode S data link at 1030/1090 MHz (Correct answer)
- ACARS messaging
- ATC radar instructions
Correct answer: Mode S data link at 1030/1090 MHz
TCAS II units coordinate complementary RAs between aircraft using the Mode S transponder data link on 1030 MHz (interrogation) and 1090 MHz (reply) frequencies.
Question 7: When using a spectrum analyzer to measure a VHF COM transmitter output, a technician observes harmonic spurs 40 dB below the fundamental. This result is:
- A critical failure requiring immediate grounding
- Within typical acceptable limits for airborne transmitters (Correct answer)
- An indication of a failed PA stage
- Normal and means the transmitter is operating at maximum power
Correct answer: Within typical acceptable limits for airborne transmitters
Harmonic suppression of 40 dB or more below the fundamental is typically within acceptable limits per FCC and RTCA standards for airborne VHF transmitters.
AET Technical Knowledge and Skills 3
HF radio communication in aviation typically operates in which frequency range?