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Definition of civil twilight for sUAS lighting

Remote Pilot (Part 107) practice question 14 of 31 on Airspace / Operational Requirements. ACS element UA.II.B.K10 · difficulty: recall. Want to answer it in a timed quiz? Use the Remote Pilot (Part 107) practice mode.

Question bank updated 2026-09-22

QUESTIONOutside Alaska, the evening period of civil twilight in § 107.29 begins at official sunset and ends when?

  1. A30 minutes after official sunset
  2. BOne hour after official sunset
  3. CWhen it becomes dark enough that unlighted objects cannot be seen
Show the answer and explanation

Correct answer: A. 30 minutes after official sunset

  • A — correct § 107.29(c)(2) defines evening civil twilight, except in Alaska, as the period from official sunset until 30 minutes after official sunset.
  • B — incorrect The regulation uses 30 minutes, not one hour, for the period after official sunset.
  • C — incorrect § 107.29(c) uses fixed clock times relative to official sunset and sunrise, not a visibility judgment.

BACKGROUND

Section 107.29(b) requires anti-collision lighting visible for at least 3 statute miles during periods of civil twilight. Paragraph (c) defines civil twilight for this purpose. Except in Alaska, morning civil twilight begins 30 minutes before official sunrise and ends at official sunrise, and evening civil twilight begins at official sunset and ends 30 minutes after official sunset. In Alaska, civil twilight is the period defined in the Air Almanac. Operation after evening civil twilight ends is operation at night, which also requires the remote pilot in command to have completed the required knowledge test or training after April 6, 2021.

STUDY TIP

Remember the 30-minute windows on each side of sunrise and sunset, and that Alaska uses the Air Almanac instead.

KEY POINTS

  • Evening civil twilight runs from official sunset to 30 minutes after.
  • Morning civil twilight runs from 30 minutes before official sunrise to sunrise.
  • Anti-collision lighting is required throughout civil twilight.

SOURCES

  • 14 CFR 107.29(b)
  • 14 CFR 107.29(c)
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SkyDrill is not affiliated with the FAA. This is an original practice item based on 14 CFR part 107, 14 CFR part 89, and the FAA Remote Pilot – Small UAS Study Guide (FAA-G-8082-22). Regulations and handbooks are revised; confirm details against the current edition.