CFC Communication Equipment Operation 3 — Questions and Answers
Question 1: What HF propagation mode is most commonly used for long-distance oceanic aviation communications?
- Ground wave propagation
- Sky wave (ionospheric) propagation (Correct answer)
- Line-of-sight propagation
- Tropospheric scatter propagation
Correct answer: Sky wave (ionospheric) propagation
HF sky wave propagation reflects off the ionosphere, enabling transmissions over thousands of miles beyond line-of-sight range.
Question 2: A pilot reports a radio as 'unmodulated' during a transmission. What does this indicate?
- The carrier wave is present but no voice audio is being superimposed (Correct answer)
- The radio is transmitting on the wrong frequency
- The squelch is set too high to pass the signal
- The antenna connection has failed completely
Correct answer: The carrier wave is present but no voice audio is being superimposed
An unmodulated signal means the transmitter is keyed and a carrier is present, but the microphone or audio chain is not adding voice to the signal.
Question 3: What is the purpose of the 'clarifier' or 'fine-tune' control on an HF single-sideband radio?
- To adjust transmit power output
- To fine-tune receiver frequency for natural voice quality on SSB (Correct answer)
- To select between upper and lower sideband
- To enable SELCAL monitoring on the frequency
Correct answer: To fine-tune receiver frequency for natural voice quality on SSB
SSB reception requires precise frequency alignment; the clarifier allows small frequency offsets to restore natural-sounding voice.
Question 4: Which of the following best describes the function of the ELT (Emergency Locator Transmitter)?
- Provides continuous ADS-B position reports to ATC
- Automatically transmits a distress signal on 406 MHz and 121.5 MHz upon crash impact (Correct answer)
- Alerts the crew via cockpit audio when radar contact is lost
- Broadcasts weather alerts on VHF guard frequency
Correct answer: Automatically transmits a distress signal on 406 MHz and 121.5 MHz upon crash impact
The ELT activates automatically on impact and transmits on 406 MHz (satellite-detected) and 121.5 MHz (homing) to assist SAR operations.
Question 5: When a pilot acknowledges an instruction with 'wilco,' what does this term mean?
- I have received your message
- I have received your message and will comply (Correct answer)
- The instruction is not understood — say again
- Standby — I am unable to comply at this time
Correct answer: I have received your message and will comply
Wilco (will comply) indicates the message was received and understood and the pilot intends to follow the instruction.
Question 6: Which frequency band is most susceptible to static interference from thunderstorms during radio communications?
- VHF (118–137 MHz)
- UHF (225–400 MHz)
- HF (2–30 MHz) (Correct answer)
- Microwave (1–100 GHz)
Correct answer: HF (2–30 MHz)
HF radio is highly susceptible to atmospheric noise, including lightning static from distant thunderstorms, due to sky wave propagation characteristics.
Question 7: What is the correct procedure when an aircraft experiences a complete radio failure in IMC while operating under IFR?
- Land at the nearest airport immediately regardless of weather
- Squawk 7600 and follow 14 CFR 91.185 lost communications procedures (Correct answer)
- Climb to maximum altitude and broadcast intentions in the blind
- Switch to VFR flight rules and proceed to destination
Correct answer: Squawk 7600 and follow 14 CFR 91.185 lost communications procedures
Squawking 7600 alerts ATC to the radio failure, and 14 CFR 91.185 prescribes the expected route, altitude, and approach sequence to follow.
CFC Communication Equipment Operation 3
What HF propagation mode is most commonly used for long-distance oceanic aviation communications?