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Characteristics of a stable air mass

Remote Pilot (Part 107) practice question 4 of 25 on Weather / Effects on Performance. ACS element UA.III.B.K1d · difficulty: standard. Want to answer it in a timed quiz? Use the Remote Pilot (Part 107) practice mode.

Question bank updated 2026-09-22

QUESTIONA remote pilot observes stratiform clouds, continuous precipitation, and smooth air with poor visibility in haze. These conditions are typical of

  1. Aan unstable air mass
  2. Ba stable air mass
  3. Ca squall line
Show the answer and explanation

Correct answer: B. a stable air mass

  • A — incorrect Unstable air produces cumuliform clouds, showery precipitation, rough air and generally good visibility.
  • B — correct Stratiform clouds and fog, continuous precipitation, smooth air and fair-to-poor visibility in haze and smoke are the listed characteristics of a stable air mass.
  • C — incorrect A squall line is a nonfrontal band of cumulonimbus thunderstorms, which are extremely turbulent, not smooth.

BACKGROUND

The stability of an air mass determines its typical weather characteristics. Unstable air is marked by cumuliform clouds, showery precipitation, rough air (turbulence) and good visibility except in blowing obstructions. Stable air is marked by stratiform clouds and fog, continuous precipitation, smooth air and fair to poor visibility in haze and smoke. When one type of air mass overlies another, conditions change with height, so a remote pilot should observe the cloud type and precipitation pattern to judge which regime is present.

STUDY TIP

Use cloud shape as the tell: layered (stratiform) means stable, heaped (cumuliform) means unstable.

KEY POINTS

  • Stable air: stratiform clouds, continuous precipitation, smooth air, poor visibility in haze.
  • Unstable air: cumuliform clouds, showery precipitation, turbulence, good visibility.
  • Air mass stability sets the typical weather a pilot will encounter.

SOURCES

  • remote_pilot_study_guide.txt ch3b "Stability" (unstable vs stable air table)
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MORE ON WEATHER / EFFECTS ON PERFORMANCE

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.