A remote pilot stands in a narrow valley near a non-towered airport and monitors the CTAF on a handheld VHF radio. A ridge lies between the pilot and the airport's approach area. Why might the pilot not hear calls from low-flying manned aircraft beyond the ridge?
- AVHF radio is limited to line of sight, so terrain between the radio and the aircraft can block the calls.
- BHandheld radios can receive the CTAF only within 1 mile of the airport.
- CManned aircraft stop broadcasting on the CTAF once they descend below 1,000 feet AGL.
Show answer and explanation
Correct answer: A. VHF radio is limited to line of sight, so terrain between the radio and the aircraft can block the calls.
VHF transmissions travel by line of sight. A ridge between a ground-based handheld radio and a low aircraft can block its calls, so the remote pilot must not treat silence as proof that no traffic is near.
- A. Correct. VHF radios are limited to line-of-sight transmissions, which is also why higher aircraft can be heard at greater distances.
- B. Incorrect. Wrong. Reception is limited by line of sight, not by a fixed 1-mile distance from the airport.
- C. Incorrect. Wrong. Manned pilots are expected to keep broadcasting in the pattern, on base and final, and after leaving the runway.
Source
FAA-H-8083-25C Pilot's Handbook of Aeronautical Knowledge, Chapter 14, Radio Equipment VHF radios are limited to line of sight transmissions; therefore, aircraft at higher altitudes are able to transmit and receive at greater distances.