CFC Communication Equipment Operation 2 — Questions and Answers
Question 1: What is the primary purpose of a SELCAL (Selective Calling) system in aviation communications?
- To allow ATC to alert a specific aircraft without continuous monitoring by the crew (Correct answer)
- To encrypt voice transmissions on HF frequencies
- To automatically switch between VHF and HF frequencies
- To broadcast weather updates to all aircraft in a sector
Correct answer: To allow ATC to alert a specific aircraft without continuous monitoring by the crew
SELCAL alerts a specific aircraft's crew via a unique tone code so they don't have to continuously monitor noisy HF frequencies.
Question 2: When operating a VHF radio, what is the standard method for checking that a transmission is being received clearly?
- Transmit on guard frequency 121.5 MHz
- Request a radio check from the receiving station (Correct answer)
- Switch to HF and retransmit the message
- Activate the SELCAL tone before speaking
Correct answer: Request a radio check from the receiving station
Requesting a radio check asks the receiving party to confirm signal readability using the standard readability scale.
Question 3: Which transponder mode transmits both altitude and identity information to ATC radar?
- Mode A
- Mode C
- Mode S (Correct answer)
- Mode 1
Correct answer: Mode S
Mode S provides altitude, identity, and two-way data link capability, making it the most information-rich transponder mode in civil aviation.
Question 4: A flight crew receives a TCAS RA (Resolution Advisory). What is the correct communication action?
- Immediately notify ATC of the RA and the maneuver being executed (Correct answer)
- Declare an emergency on 121.5 MHz
- Request a new transponder squawk code from ATC
- Switch to HF to coordinate with the conflicting aircraft
Correct answer: Immediately notify ATC of the RA and the maneuver being executed
Crews must follow the RA first and notify ATC as soon as practicable of the deviation from clearance.
Question 5: What does the term 'frequency congestion' require a controller or pilot to do?
- Immediately switch to an alternate frequency
- Listen before transmitting to avoid stepping on other communications (Correct answer)
- Use data link (CPDLC) exclusively until the frequency clears
- Reduce transmission power to avoid interference
Correct answer: Listen before transmitting to avoid stepping on other communications
Standard radio discipline requires monitoring the frequency before transmitting to prevent simultaneous transmissions that block communication.
Question 6: Which device allows a pilot to monitor two VHF communication frequencies simultaneously?
- A dual-channel squelch unit
- A COM radio with dual-watch capability (Correct answer)
- A HF single-sideband transceiver
- A mode C transponder
Correct answer: A COM radio with dual-watch capability
Dual-watch (or dual-receive) on a VHF COM radio lets the pilot monitor an active frequency and a standby frequency at the same time.
Question 7: In aviation communications, what is meant by 'breaking squelch'?
- Manually silencing the radio receiver
- An incoming signal exceeding the squelch threshold, causing audio to open (Correct answer)
- Switching from single sideband to AM mode
- Using excessive transmit power that distorts the signal
Correct answer: An incoming signal exceeding the squelch threshold, causing audio to open
Squelch suppresses background noise; a signal strong enough to exceed the squelch threshold 'breaks' it and the audio becomes audible.
CFC Communication Equipment Operation 2
What is the primary purpose of a SELCAL (Selective Calling) system in aviation communications?