CFC Communication Equipment Operation 4 — Questions and Answers
Question 1: What is the function of CPDLC (Controller-Pilot Data Link Communications) in modern aviation?
- Provides radar secondary surveillance data to ATC
- Allows text-based digital message exchange between pilots and controllers (Correct answer)
- Encrypts VHF voice communications in high-density airspace
- Activates automatic altitude reporting via transponder
Correct answer: Allows text-based digital message exchange between pilots and controllers
CPDLC enables digital text messages for routine clearances and reports, reducing voice frequency congestion especially in oceanic airspace.
Question 2: A flight crew is unable to establish contact on the assigned frequency. What is the recommended first action?
- Squawk 7700 and divert to the nearest airport
- Attempt contact on the previous frequency or a published backup frequency (Correct answer)
- Broadcast a PAN-PAN on 121.5 MHz immediately
- Turn off the transponder and attempt HF contact
Correct answer: Attempt contact on the previous frequency or a published backup frequency
Before declaring an emergency, crews should try the last used frequency or sector backup frequency, as the primary may be temporarily congested or the frequency assignment may be in error.
Question 3: What does the 'guard' frequency 121.5 MHz designate in aviation?
- The primary oceanic HF calling frequency
- The international aeronautical distress and emergency frequency (Correct answer)
- The frequency used for aircraft-to-aircraft communication in uncontrolled airspace
- The ATIS broadcast frequency at major international airports
Correct answer: The international aeronautical distress and emergency frequency
121.5 MHz is the international VHF emergency frequency monitored by ATC and military facilities worldwide for distress and urgency calls.
Question 4: In radiotelephony, what is the correct way to transmit the number '500'?
- Five zero zero (Correct answer)
- Five hundred
- Fife zero zero
- Five-oh-oh
Correct answer: Five zero zero
ICAO radiotelephony standards require all digits of a number to be spoken individually, so 500 is transmitted as 'five zero zero.'
Question 5: What is the purpose of a radio 'back-up' or 'standby' communications system on commercial aircraft?
- To provide an alternate means of communication if primary systems fail (Correct answer)
- To allow passengers to communicate with the flight deck
- To relay weather data automatically to the airline dispatch center
- To connect to military ATC frequencies during special operations
Correct answer: To provide an alternate means of communication if primary systems fail
Redundant communication systems ensure continued ATC contact even if the primary radio or audio panel fails.
Question 6: Which audio control panel function allows a pilot to transmit on one radio while monitoring a different radio for reception?
- Interphone coupling switch
- Split COM function
- Receive-only (RX) selector
- Transmit-select combined with independent receive selector (Correct answer)
Correct answer: Transmit-select combined with independent receive selector
On most audio panels the transmit selector and receive selectors operate independently, letting the pilot key COM1 to transmit while monitoring COM2 audio.
Question 7: What is the maximum range limitation most associated with VHF aviation communication?
- VHF is limited to approximately 50 nm regardless of altitude
- VHF is line-of-sight limited, with range increasing with altitude (Correct answer)
- VHF signals cannot propagate below 10,000 feet MSL
- VHF range is fixed at 200 nm for all aircraft types
Correct answer: VHF is line-of-sight limited, with range increasing with altitude
VHF propagates in straight lines and cannot follow the Earth's curvature, so range expands significantly as aircraft altitude increases.
CFC Communication Equipment Operation 4
What is the function of CPDLC (Controller-Pilot Data Link Communications) in modern aviation?